I've seen a few "real world" tests of wider road tyres, which tend to suggest that wider is better (or at least no worse) once you account for suspension as well as hysteresis losses. But these tests all seem to stop at around 28mm. Is anybody aware of any tests that go much wider (e.g. 50mm or even higher)? I know there are some lab tests on fat tyres, but they ignore the suspension effect so aren't really what I'm after.
The trouble with real world tests is there are too many variables.
A 50mm tyre might be faster on a rough bit of road, but is going to be slower on smooth roads simply by virtue of having more than doubled the aerodynamic drag. So it becomes subjective, do you want to go faster or more comfortably? Which isnt going to be something a simple test can tell you.
I.e. you could probably optimise a bike arround 25 or 28mm tyre and find its faster in some conditions, but you wouldnt put 32mm tyres on a bike for racing on the road. But you might put them on your sunday clubrun bike if your fit enough to overcome their drawbacks and keep up.
I suspect there are also speed variables in this ie at one speed the wide tyre is better, at another the narrow one.
Surely that’s why you need a real world test though. I can see that a wider tyre has more aerodynamic drag in theory but I have no idea whether that actually matters out on the road at the speeds I ride. Bicycle “science” seems to be full of accepted wisdom with very little evidence to back it up.
I agree that it’s hard and most tests don’t come close to being scientifically rigorous but some are better than others.
Rule of thumb, the faster your average speed the narrower a tyre you should run as the aero benefits outweigh the reduced rolling resistance.
Hence why the pro peloton arent all on 32c's if it was proven to be faster they 100% would be.
Yes, but if I tested a tyre down the new bypass Id bet my bike on it that a 23mm tyre is quicker as its like a billiard table.
Down the old cycle path running parallel to it then Surly E.T.s would win simply by virtue of getting through without a puncture.
Remember for a comparable tyre rolling resistance is the same for the same comfort level (i.e. lower pressure in a big tyre). A wider tyre is faster at the same pressure but only by about 1W between 23mm and 32mm.
The difference between a shallow and 50mm rim is about 12W (for a pair) at 30km/h.
I cant find a figure for the total aero drag of a 23mm tyre and wheel, but its going to be of the order of 10-50w i imagine, and doubling the frontal area is double the drag so that 1W saving in rolling resistance is completely dwarfed.
If you want a "real world" test go an do it yourself as the real world is the world as you experience it.
I have a few loops I do that I have done a lot of times over the last few years and my times vary so much (even on the exact same bike, tyres etc,.) that any difference in times with different tyres were not prove anything. That is why a scientific test would be better but that would be a number of tests on specific terrain for specific distances and gradients so again when riding 50 miles and encountering the different terrain, gradients, wind speed etc,. in the real world you may not match up with what the scientific tests would suggest.
I am currently riding 23c tyres because I like how they feel...
Bicycle “science”
Is largely marketing.
the aero benefits outweigh the reduced rolling resistance
Daft question, have you got a link to anything which proves the RR benefits of wider tyres at proper pressure? I've seen plenty of "studies" which show that a 23 run at 50 psi is crap. I've not seen anything that shows a 28 is better than a 23 at 100psi.
No argument here that lower pressure is more comfortable (which might be faster as a result of fatigue etc) but the RR thing seems largely to be reliant on running skinny tyres at inappropriately low pressures. (and often different tyres and carcasses too)
(I've never seen anything testing wider tyres at a range of pressures either, certainly my wider tyres at 80psi feel much better rolling than they do at 50 but I'm not sure the comfort benefits exist at 80 because the tyre feels that much more firm than a narrow one at 80.)
As to the op, I can provide RW opinions of my 23s vs 32s, vs 42s vs 2.35s but, they're all different tyres so of no real scientific value (the 23s are on a different bike too). One thing which is constant is they all feel quicker at higher end of acceptable range pressure than mid range or low.
At the same deflection all widths roll the same. I commuted today on 32c, rode 100 k on 23c on Sunday and did a 12 hr TT recently on 20c (ok it has three wheels). Comfort is better on bigger tyres at lower pressures. But for speed, my 20c on 3x HED3 carbon wheels is the fastest and most aero.
I see little benefit once you get above 25c. Tyre quality is a bigger factor. I’m 69 kg. Heavier riders may want a higher pressure.
BTW I have GP4000 in 20/23/25c and GP5000 in 23/25c for reference on different bikes and wheel sets.
Narrow tyres on a wider profile rim give a wider profile, e.g. a 23mm on a 28mm internal rim width will come out at 26mm (Cannondale SystemSix).
OP, check out Jan Heine and Bicycle Quarterly for the gospel about wider tyres
Once you're travelling above ~15mph, aero losses play an incresingly important role, especially at the front end of the bike for factors including how the front tyre shape "blends" into the front wheel rim sides.
For a compromise of speed vs comfort on my 17mm internal rim width wheels on my road bike, I should probably go ~23mm (real world measurement) up front and 32mm at the rear (if I could just about safely squeeze them in, 28mm GP4000S IIs are ~31mm wide).
I swapped out my fatbike's fat rear wheel with 26x4" JJ back to FatNotFat 29er with 700x28 Grand Sport Race on Monday. This reduced the weight by ~1.9Kg and the rolling resistance by a guess of ~7W, but even at ~12mph the ride home with ~350feet of climbing polarised towards the end of the ~4.5 mile commute felt much less hard work... Depsite having a 29x2.35" G One Speed Evo up front.
I’ve not seen anything that shows a 28 is better than a 23 at 100psi.
but you'd never be running a 28 at 100PSI, that would be defeating the purpose of the larger tyre
Daft question, have you got a link to anything which proves the RR benefits of wider tyres at proper pressure? I’ve seen plenty of “studies” which show that a 23 run at 50 psi is crap. I’ve not seen anything that shows a 28 is better than a 23 at 100psi.
Have a look at the gp5000 test on bicycle rolling resistance .com. its probably the only tyre they've tested from 23mm to 32mm. And they test them at, the same pressures, the recommended pressure and equal deflection. The biggest difference is about 1W, it's tiny really.
Bicycle quarterly kicked off the whole wide tyres are fast thing, but then the owner owns compass tyres IIRC.....
I dont dispute that there are benfits, but outright speed on the road isnt one of them unless your road is truly bad enough that suspension plays a part. If you want to ride a 200k audax, 28c tyres might make it more confortable. If you want to do a 200k race, 700x25.
Is largely marketing.
There are a few people trying to be (at least a bit) scientific about things. Whether that is peer-reviewed work in journals or just trying to devise a test that isn't too biased and approaching the question with an open mind. But you are right, the vast majority of tests you find online are really just thinly disguised marketing. You want to buy a new bike, but find it hard to justify (to yourself or whoever)? No problem, here is an article/video that "proves" your new bike will be better. It does no such thing of course and usually doesn't even pretend. But as long as you realise it's only there to help the economy keep ticking over that's fine.
If you want a “real world” test go an do it yourself as the real world is the world as you experience it.
That's true, but a) it would mean buying a load of tyres, wheels and probably frames to accommodate them anb b) I'm lazy and it is much easier to sit here and criticise somebody else's test rather try to devise my own for other people to criticise.
OP, check out Jan Heine and Bicycle Quarterly for the gospel about wider tyres
It was reading those articles that started this thread 🙂 But I've still not found many actual tests that go beyond 28mm. I'll look again though.
And they test them at, the same pressures, the recommended pressure and equal deflection.
Ah I'll dig that up ta.
The biggest difference is about 1W, it’s tiny really.
Speak for yourself, that's like 50% upgrade...
but you’d never be running a 28 at 100PSI, that would be defeating the purpose of the larger tyre
I'd be much more inclined to run 28s at 100psi than 23s at 60psi but regardless this is sort of my point, most everything I've seen relys on running the wrong tyre at the wrong pressure. (Tinas' article doesn't count as I've not read it yet and, even then, it's one in a myriad of things)
Then tyre makers go and ruin it all by having completely different ideas about what a 25c tyre atually is. Or 28c or whatever.
My Michelin Pro4 25c are just about as wide as the identical tyres in 28c on another bike, jjust the 28c is taller. Vittorias 25c on another wheel (identical rim) is 3 or 4mm narrower, so even if you decide you want, say 25c tyres, there's no guarantee you're going to get the benefits anyway.
Interesting there's more of a difference from the tube type than the width or the [sensible variation in] pressure. At "recommended" pressure there is marginal RR difference between 32s and 23s,the 23s being lower resistance but the wider tyre has a lower RR for any given pressure - 32s need to be at 100psi to have lower RR than 23s at (appropriate for the size) 120psi.
That’s true, but a) it would mean buying a load of tyres, wheels and probably frames to accommodate them anb b) I’m lazy and it is much easier to sit here and criticise somebody else’s test rather try to devise my own for other people to criticise.
I have bought a load of tyres over the years and recently switched from 28c to 23c (same model of tyre). The 23c is faster uphill. I also did a comparison 2 years ago (again with same model of tyre) between 43c and 38c. The 38c tyre was faster (on road and gravel)
The tests were various Strava segments where I was going as fast as I could.
Again, if you really want to know you will need to make your own comparisons as you may not find what I found due to you being heavier/lighter, riding on different roads and different gradients and at different speeds.
I had 42mm voyagers on my commuter. They were shit (draggy). Got 30/32 spesh roubaixses now, they're better and still comfy even on rough Cumbrian lanes, not up to much off road though.
25mm tyres are faster than 30mm according to me and this improvement in fastness goes up when riding in a group thats faster, but I prefer 28mm tyres which are still fast with some comfort and befote you ask yes i r scientist.
Might have popped some GP5000's in a 32 on my commuter last night 🙂
Still to early to pass judgement but 32's def slower to spin up than schwalbe ones in 25 and def a noticeable change in steering feel as expected but not soul destroyingly slow once rolling and the extra grip/comfort is very nice for the winter months as the roads around here fall apart.
Got some 47 Horizons on 650b on the fun bike and they are suprisingly quick but I think the novelty runs out if you were commuting any distance on em on normal roads but great if your mixing your surfaces up.
In my experience wider lower pressure tyres are much slower but much more comfortable. My winter bike has 42mm Contact Sports (lovely tyres) and running low pressure is like sitting in an arm chair but bloody hard work. My commuting bike has 32mm tyres and is quicker but less comfortable, my 'summer' bike has 23mm tyres and is quicker again (you have to factor in the difference in weight as well).
In the '80s I used to TT on 18mm tyres pumped up 'as hard as they would go'. It would be interesting to ride a bike with a variety of tyres and pressures on the same road to see what the difference would be. The problem is that you can never recreate the same conditions and that lab rolling resistances only tell part of the story.
yes i r scientist
Botanist?
I have ridden the same bike on 22mm tubs, 25 mm and 28mm contis. I cannot tell a difference apart from the gp4000s are far grippier and that for me trumps everything
the only difference I can tell is if the pressures drop they feel significantly slower.
My best road bike has 23s, my allroad I either ride with 650b 48 or 700c 32.
The road bike is fast at 85/90psi, the 650b48’s are long distance good and the 700c32’s are good compromise fast.
I did run 650b38 but found the gearing too low.
I don't ride road bikes but have done and there are a few in our household.
Tyres seem to have settled on 25mm width for (perception or other wise) comfort and efficiency.
Maybe one reason they don't test anything wider with any conviction is because most road frames that are built for speed won't take anything much wider, I know my OHs bikes won't.
Therefore, seems a tad daft wasting time to prove a 42mm tyre may well be the be all and end all to find 90% of the people who could benefit from it can't fit it on their bike.
Therefore, seems a tad daft wasting time to prove a 42mm tyre may well be the be all and end all to find 90% of the people who could benefit from it can’t fit it on their bike.
Plus it is very, very unlikely to be faster. It will weigh more and it will be less aerodynamic. Unless the roads are very rough the 42 will not give anything over a 28.
30s at 60 psi tubeless here. I don’t race or do fast chain gangy stuff so speed is not important, faster or slower. Its great on crappy roads and cornering. I can barely get my crappy track pump to 100 psi anyway.
I am currently riding 23c tyres because I like how they feel…
One thing which is constant is they all feel quicker at higher end of acceptable range pressure than mid range or low.
This is covered in some of the wider/balloon tyre write ups. people "know" skinny tyres at high pressures are the fastest, and with that comes with harsh/direct ride feel, so they associate harsh/direct ride feel with a tyre being fast, and "know" a more comfortable, less buzzy ride will be slower, and won't like it.
Whether it's actually quicker or not doesn't really come into it!
There was another article on a similar theme someone posted a feew weeks back about long term bikes testing with blinded riders. Almost all opinions about how a bike rode or how quick it was were pre-formed by what sort of bike it looked like.
Whether it’s actually quicker or not doesn’t really come into it!
Well in the interest of scyunse I put 65psi front and rear in my 42s this morning. Much more noticeable over rougher tarmac, more jarring but I wouldn't say uncomfortable, that said it's a road, even the "path" is only so rough and then it's mostly easily avoided in all but short sections.
On those rough bits I was definitely slower by virtue of using my arms and legs to absorb the impact so pedaling les, even if I was only half my normal speed over those bits though that's maybe a minute max extra over 35 minutes of riding. On cobbles it might be different but actual roads mostly aren't bad enough for there to be any real benefit IMHO.
I was, in total, 3.5 minutes quicker than average for my morning commute this morning though and traffic seemed as bad as usual. So on that basis:
3.5mins faster than 35min average means 65psi is roughly 10% more betterer than 50psi
Thanks for all the responses. It looks as though the simple answers to my question is "no, there aren't any real world tests of tyres above around 30mm that could count as even vaguely scientific". Lots of received wisdom that doesn't seem to have any actual evidence to back it up. I guess that's pretty much the definition of received wisdom.
I hear comments to the effect that a wider tyre will be slower because it's heavier or less aerodynamic, which sounds fair enough, but I'd still like to see the proof.
Lots of anecdotal stuff of course, which is almost the raison d'être for discussion boards like this. All very interesting but most of it doesn't stand up to much scrutiny (different tyres on different bikes under different conditions are different)
The one that interests me (particularly in light of the test done on tank seats by the army, which showed that a human body can easily absorb more power that a top cyclist can generate) is the idea that wider may be more comfortable but narrower is still faster. This seems to assume that discomfort is just something to endure and the only negative effect is on long term endurance of the rider. But is this true? What is discomfort? Is it just the body's way of telling you that heat is being generated somewhere? If so, that discomfort isn't just annoying it's actually lost energy that would affect your speed.
I'm not saying a 40mm tyres is faster than a 25mm one, but I'm not saying it's not either. I'd like to see a well designed study that tried to answer the question. It sounds as though there isn't one though, so we can just continue to argue the toss until someone does one 🙂
the only difference I can tell is if the pressures drop they feel significantly slower.
Completely non scientific I know, but after listening to that podcast, I've stopped pumping up my road bike tyres completely. I used to religiously put 120psi in each morning before a ride. Other than the loss of road buzz, and smoother ride, I've not noticed any excess loss when riding in a fast group. No idea what pressure they're at now, probably about 60 maybe (25mm GP4000s). I intend to continue the experiment until I start hitting rims on the tyre, at which point I'll put some air in them...
Thanks for all the responses. It looks as though the simple answers to my question is “no, there aren’t any real world tests of tyres above around 30mm that could count as even vaguely scientific”.
A real world test will never be scientific. A real world test would be me riding around a 20 mile loop using different tyres each time. However, during that loop the wind speed and direction will differ and the exact bits of road I ride on will differ. As my times around that loop already differ by up to 5 minutes with no change of tyre so any changes from a tyre are going to be impossible to claim.
To narrow it down a but I can pick a segment on strava and repeat that with different tyres. As said, I have done that. 23c was faster uphill, 38c was faster on gravel.
That is as scientific as a real world test will be.
Botanist?
I prefer plant community ecologist!!
A real world test will never be scientific.
That's going to upset a lot of scientists 🙂
That is as scientific as a real world test will be.
Are you sure? How about (as a starting point) a group of riders with power meters and GPS devices riding the same segment multiple times, swapping wheels between each run, on a day when the conditions were stable. That should give you data on the power required to maintain a certain speed with different tyres (on that particular segment, under those conditions). As long as you do enough runs and you can get tyres of the same construction in the different sizes. you should be able to tell whether tyre size is a significant factor or not. You could also test whether time of day was a significant factor to see if the conditions changed significantly.
It's not that hard to design real world tests. Scientists do it all the time. You don't have to remove variability, you just need to ensure that there isn't a systematic bias. If there is too much variability for any of the factors to be statistically significant that's fine. It's still scientific, it's just inconclusive. The conclusion of most scientific studies is usually "more studies required (please send money)" anyway.
I can pick plenty of holes in my own study design above, but I still think it's possible to design a scientifically valid real world study. Just avoid the technique beloved of GCN, GMBN and many others of designing "experiments" specifically to highlight differences that you've already concluded are there 🙂
Not necessarily what you are asking, but there is enough information around which infers to me what the fastest tyre size is. Plenty of scientific information about, both Zipp and Enve have had reports about the fastest tyres on their wheels. Reynolds, while I've not found a report - just individual statements. They don't go to the 50mm tyre size, but they don't need to. Google the 105% rule to find more information.
https://blog.silca.cc/part-5-tire-pressure-and-aerodynamics
I also don't really find the infomercials from Bicycle Weekly / Compass very useful. The word "probably" comes up a couple of times, narrower tyres are probably faster in certain conditions etc. Also, as an inference, I look at the fact that the Pro-Peloton are not riding wide tyres. There is a culture in pro and amateur cycling to look at the most marginal of gains possible. If 32 or 35mm on the current frames and wheels available was fastest, pretty sure we would see them at the start line.
I ride 23mm front and 25mm back on my race bike and 32mm front and back on my winter/training bike. Different compounds so impossible to say if its the tyre size - but I am slower on the wider tyres (on the same rim).
I can pick plenty of holes in my own study design above, but I still think it’s possible to design a scientifically valid real world study.
Yes, you are probably right. Maybe by literal reading of the term "real world"
My real world is riding mixed terrain all year around. On some sections a wider tyre is better and on other sections a narrow tyre is better. Doesn't really matter what someone else has tested with power meters etc,. as they are not riding the same mix that I am so it makes no difference to my real world as I am not going to be switching tyres half way around, dependent on what route I fancy half way around etc,.
Ah, right, fair enough. I think I see what you mean and I agree. Any test that is remotely scientific is probably going to have to be limited to a very specific set of conditions (e.g. single segment of track). It may still be a real world example but isn't necessarily going to tell you what is best for you over a whole ride.
You don’t have to remove variability, you just need to ensure that there isn’t a systematic bias.
And repeat it, a lot.
And then some more 🙂
I can't think of a reasonably wide tyre (35mm+) that is built as lightly as a narrow "fast" tyre, and that's what is needed for a proper comparison test.
Why do you all want to go faster so badly?
wzzzzzzzzz - I agree. I want the tyre with the best grip that is not unacceptably draggy
If wide soft tyres are faster why is my fatbike so slow?
I want to go faster because it’s a race. So I have aero on three wheels, all of which have narrow rims. So 20c tyres are the best aero match for those wheels. Fortunately it’s on reasonable A roads. For general riding I’m happy with less fast. So 25c is fine the 32c i commuted on today feel like overkill though. Noticeably harder to spin up, even on light wheels
Some of us race. Some of us ride in chain gangs and fast group rides.
Don’t compass make 35mm light tyres? They do two options, normal and light, but not sure of the competitive weight to a normal 25 or 28mm tyre.
The data is already dry there showing the tyre size and the crr and aero differences. As I’ve mentioned earlier and said rather a lot on this forum, Zipp and Enve have published data on tyre sizes, google 105% rule for cycling. All the data is available to read.
Used to run 40mm compass Barlow pass extralite at 42 psi on my tripster (well under 300g I think) and they were bloody fast as shown by times on my fav loops round the roads in Galloway, poorly surfaced and more than not they were chipsealed with chunky gravel. To begin with I thought they were slow on the road due to them making the ride feel so comfortable and relaxed as I was used to getting bounced around on my previous 28mm at 90 psi but after quite a few rides I found I was getting home earlier than usual and my back and shoulders/arms/wrists etc didn’t feel as beat up.
totally unscientific but fat tyres with a light and supple casing to conform to the surface and run at sensible pressures are faster over normal roads, high pressure 23mm tyres belong on a velodrome.
fight !..........
Somafunk, scientifically they are proven to be slower. But it’s not a massive difference, but it is quantifiable slower to use wider tyres on current road bikes.
I’ve provided the evidence in this forum in similar debates on numerous times. Then a month later the same question is asked and always using the Compass / Bicyling weekly advertorial as the benchmark. Rather than look for the 105% rule which is used by Zipp, Enve, Bontrager and Reynolds.
I’ve also ridden compass (panracer made) 35 and I think 38mm tyres. They are really good tyres for winter riding. But I don’t find them as fast in race conditions as my 23mm race tyres. There’s also not always a big difference in grip between 23 and 35mm tyres. That comes down to casing, the panracer /compass tyres in my opinion are the best wide tyre I’ve used in that regard.
People should ride what they want and if a wide tyre makes you think it’s the fastest for your conditions, that’s great. But please read all the different views out there, including those of the people who make wheels and whose job it is to make the fastest race system, not just the views of those people selling wide tyres.
I’d agree that on a specific wheel and in specific conditions a wider tyre will be as fast or even faster than a 23mm tyre. But there are very few wheels or bikes available to take a 30mm external rim, Enve 3.4 AR is the closest that I’m aware of.
Why do you all want to go faster so badly?
tyre choice should come somewhere after skin suit and aero lid which would be a long way behind tri bars 😀
Apart from tri bars are not allowed in a race, chain gang or fast group ride.
And most importantly I can’t get any tri bars to fit my aero bars!
chain gang or fast group ride
LOL the rules the rules
I'll add some anecdotage, since I was thinking of this while riding back home yesterday. My commute is mostly dirt road, and I alternate between two bikes on different days, one of which has 37 mm tyres and the other 31 mm. I realized that I feel a significant difference between how they react to deeper and looser sand and gravel. The thinner-tyred bike feels like it slows down when riding through the softer stuff, which I hypothesized is due to plowing into it, while wider tyre rides on the top and isn't affected as much. So, as said above, what you consider a road has a lot to do in what kind of tyres are faster.
As an another example, not from me, a local ultracyclist experimented with a 90's ATB and some wide, around 50 mm, Compass tyres a year or two back, but came back to 32 mm's because they were faster and comfortable enough for him.
I have ridden a range of tyre width's on the gravel roads I ride on and would agree. I am currently on 23c and they are slower on gravel. Last year I tried 43c and 38c in same tyre model and the 38c was faster overall. The 43c was 100g heavier and teh extra width didn't seem to make any difference.
However both of those sizes of tyres made the bike just feel less responsive so I went back to 28c.
For me tyres are not just about speed but how they make the bike feel. I like 23c on road but they are not as nice off road. The difficulty for me is that pretty much every ride I do is 50% road and 50% gravel.
Klunk, if you race road or crits with a team then you would ride in a fast group ride or a chain gang. Another name for it is training.
When I’m pootling along I’m more than happy to use 32mm or wider tyres.
The question keeps getting asked about the lack of scientific evidence around tyre width, but it tends to be from guys who commute in wider tyres and want a level of justification for their purchase. The evidence is there, it’s real. But it’s like talking to flat earthers.
If my winter bike could take 35mm tyres
I’d run a set of compass tyres on them. But I’d accept that scientifically I wasn’t on the optimal tyre size.
If people feel safer and faster in wide tyres that’s great, but it doesn’t mean the science and the Manufacturers are wrong.
Another name for it is training.
so they are allowed then ?
Tri bars? No. Not for chain gangs. But that’s because they would be deemed unsafe at that intensity.
We have between 6 and 10 guys riding at max effort centimetres away from each other. Tri bars wouldn’t be safe. Different discussion though.
I already have the skin suit helmet and aero front end tribars 🙂 . Now down to tyre choice. I had the choice of 23c GP5000s or 20c GP4000s because Continental have not produced their newest Uber tyre in the narrowest width. The watts saving for the new ones, which are very good, would be less than the aero savings from a properly fitting tyre. And all three wheels are right out there in the wind (it’s a delta upright tricycle). Also for the two rear wheels this will help a little with load and hence comfort and I can run them a little lower than 120psi.
Now for training I run 23c on different wheels. It’s more comfortable. But not faster. I race my two wheelers on 23c front and 25c rear because the back tyre is shielded by the seat tube. Front is out in the wind.
There have been aero tests of width vs power (aero coach published one). And it’s a real effect. In a TT you need every watt you can find. In a road race you still need them even when drafting.
From my commute times going from 28c gp4000 on a carbon road bike were about 3 minutes fast over 10miles than 40c wtb nano on a alloy gravel bike. The gravel bike winning on comfort road holding. The lack of buzz on poor road surfaced is more than worth losing 3 minutes. Even sold the road bike as I just don’t use it anymore.
Correct me if I'm wrong @w00dster but I thought the data from Zipp, Enve etc was only for lab tests.
Not that there is anything wrong with lab tests. They are a great way to isolate a single factor and dramatically reduce the variance allowing you to tease out tiny differences in that one factor. The problems comes when you try to extrapolate to a real world situation and have to make assumptions about all the other factors, especially if those assumptions have not been validated.
I'm happy to accept that the evidence shows that hysteresis and aerodynamic losses are greater in a larger tyre. They are also (like for like) heavier. But they have an advantage in reducing suspension losses and these seem to be very poorly understood. So, people look at lab data, which shows hysteresis or aerodynamic loses are higher and conclude that wider is slower (i.e. ignore the suspension effect that "may" offset these losses). Or they say things like "narrower tyres are better on smooth roads" without providing evidence. Yes a smooth road is smoother than a rough one, but it's not perfectly smooth. Does that matter? I don't know.
The results I've seen are enough to convince me (and most of the pro peleton by the sound of it) that 25 is faster than 23 pretty much everywhere. I'm also convinced that 28 is probably better than 25 at the sort of speeds I ride at and on the sort of roads I ride on. But I'm left wondering what happens above that. Maybe the negative effects (hysteresis, aerodynamics, weight) outweigh any suspension benefits on all but the roughest of surfaces. But I'd like to see the proof.
Why do you all want to go faster so badly?
It's a good question. I ride on my own, so why do I care about speed? Off road I don't. I choose to use tyres that provide plenty of grip and security in exchange for speed as I'm just out there to enjoy the environment and going faster really doesn't improve things for me. It's why I've no interest in ebikes, but that's a different thread.
So the question, for me, is why ride on the road? I prefer riding in beautiful places, with peace and quiet, away from the noise and annoyance of cars (and people for that matter). I can get all that off road. But one thing I get from road riding that I can't get off road is that feeling of effortless speed. I quite like the idea of tyres (or even a bike) that opens up options to take rougher tracks. But take away that effortless speed any I've removed the main reason why I would ride a road (or gravel/adventure) bike in the first place.
If wide soft tyres are faster why is my fatbike so slow?
"all other things being equal". Your fatbike tyres are running very low pressures, probably of not that light construction, and the overall weight is much higher.
The corollary to wanting to go faster (with acceptable levels of grip) is wanting to put less effort in for the same speed and grip, or get more grip for the same speed and effort (and durability/reliability of course). I don't know anybody that doesn't want this tradeoff to be better, no matter what they say.
I choose to use tyres that provide plenty of grip and security in exchange for speed as I’m just out there to enjoy the environment and going faster really doesn’t improve things for me. It’s why I’ve no interest in ebikes, but that’s a different thread.
I challenge you to go out and buy a set of dual ply supertacky Swamp Things (NOS somewhere perhaps - I'm sure the current version will be a bit faster rolling) and still feel this way. You won't better the grip on a rooty rocky muddy ride, but you will want to roll faster unless you have an uplift and 100% steep descents. And it's not just the weight, it's like riding with the brakes on.
Hi Roverpig,
I'm not disagreeing that 25 or 28mm could be faster (or as fast as a 23mm tyre). But it needs the correct rims / frames to make that work. With regards to riding conditions, thats very changeable, so my information is based on tests showing the actual fastest, not the fastest for your personal ride.
Real world tests have been done and the Hambini blog is worth a read, 23mm still comes out on top. But the margins we are talking are incredibly small. Hambini has completed a mix of lab and real world testing, but the focus has been on the wheel rather than tyre - after all they have already concluded what is the fastest tyre/rim combination. An extract "This guidance is uniform across the board. It is vitally important to install tyres that are slightly narrower or inline with the brake track of the wheel rim. A ballooning tyre will impact the drag significantly.
There has been a trend towards wider tyres on bikes of late. From an aerodynamic perspective, the width of the rear tyre has little effect but the width of the front tyre has much more impact and therefore a 23mm front tyre is recommended irrespective of whether the wheel was designed for 25mm tyres. At speeds above 30km/h, it is more beneficial to have 23mm tyres than 25mm front tyres for aerodynamic benefit."
https://www.hambini.com/blog/post/bicycle-wheel-aerodynamics-which-one-is-fastest/
Its worth saying incase it gets missed in the long texts. Read about the 105% rule, this is what wheel manufacturers build to and reflects what Hambini is stating. Really worth a read. The point I try to make is that the accounts made by Bicylcing Weekly and Compass that fatter tyres are faster is incorrect and the science points away from that.
For my closed circuit crit racing, 23 front and 25 back is without doubt the fastest combination for my wheel profile, the wheel and the bike are designed to work specifically for that combination. But, that is completely different than other people's riding. With my current rims I personally wouldn't race on anything above 25mm, that includes open roads where the tarmac isn't always great.
The testing has been done to show that 28CRR is pretty much the same as 25, above 28 and CRR stays pretty similar but drag increases. Its all marginal, hence why I ride with 32mm for winter rides. Once wider rims and disc brakes become the norm, then this will change the tyre / rim design. Hunt have a wider rim as do Enve, I'd happily race wider tyres with those rims. (As the pro's ride with wider tyres with the rim with the wider brake track - but this is also only for specific races)
Site I've previously linked to that is well worth a read.
https://blog.silca.cc/part-5-tire-pressure-and-aerodynamics
The results I’ve seen are enough to convince me (and most of the pro peleton by the sound of it) that 25 is faster than 23 pretty much everywhere.
You will find that there are no pros racing TTs on 25c tyres. Most TT wheels are now optimised for 23c clinchers or 22c tubulars. HED have made their iconic Hed3 rim wider due to the availability of narrow tyres diminishing (19-20c) and some percieved comfort benefits. But the original 17mm internal diameter wheel is faster when run with the correct tyre. And my it is fast! I run 23c on my rear disc wheel, which is a wider Hed wheel. But rear is not really an issue for two wheelers due to the seat tube.
On my best bike, I run 25c GP5000 front and back with latex tubes on wide 60mm carbon rims. It's a great choice for general roads, comfortable yet fast. For road racing I run 23/25c Corsas on older Hed Jet6/9 rims, but will eventually switch to GP5000s as I like them that much.
There's not a huge amount in it, but I can'r see a switch to anything wider any day soon. The 32c Schwalbe G One Speeds are a nice tyre, and I run them tubeless, but they are not in the same class 😉
25c is the new 28c as far as I can see.
28mm works for some
What is "real world"?
https://www.conti-tyres.co.uk/latest-news/165-wider-tyres-go-faster
https://www.cyclist.co.uk/in-depth/726/are-wider-tyres-really-faster
https://www.businessinsider.com/tour-de-france-wider-tires-lower-pressure-faster-2018-7?r=US&IR=T
Maybe different tyres and different tyre pressures suit different riders
https://www.youtube.com/watch?v=E3C5RzQrTvw
If wide soft tyres are faster why is my fatbike so slow?
Ohhh, I dunno.
I did a local hillclimb on my on-one and didnt come last beating a few road bikes (at least one ridden by someone i didnt think id beat even on a propper bike) despite having a nightmare with pacing and taking the steepest bit far too easily thinking there was more to go.
Its still slower though.
Well it’s going to take me a while to get through that lot (I’m still working through the homework @w00dster set me 😀) but thanks.
GCN video is summarised by 28mm tyres or slightly wider on the wide Enve rims is faster than a 25mm tyre. I’d agree with that, in those rims on that bike.
Most rims though, nope. Simon does say that in the video (approx 6:50 in).
There’s no science or details on the tests carried out, just refers to the Compass tests.
The cyclist test, while interesting isn’t really a good test, that’s a roll down test on an 18 second test. Using a rider doing 30 attempts. Room for error seems to be high.
Extracts from the continental data “ Tyre giant Continental claims a 23mm tyre at 120psi, a 25mm tyre at 90psi and a 28mm tyre at 80psi all have the same rolling resistance.
Wider tyres may provide less rolling resistance, but they can increase the amount of aerodynamic drag, cancelling out any gains you may have made. This is especially true if you have narrow rims, as the larger tyre will bulge out more. The best way to get the most out of your wider tyres is by having wider rims to match. This creates a more rounded and aerodynamic profile, helping to get the best of both worlds; lowering rolling resistance and aerodynamic drag.”
The best way to get the most out of your wider tyres is by having wider rims to match. This creates a more rounded and aerodynamic profile, helping to get the best of both worlds; lowering rolling resistance and aerodynamic drag.”
Whilst true, a wider rim will minimise drag for a wider tyre. It doesn't get you round the simple fact that the A in CdA is area, and a 28mm wide wheel is 40% wider than a 20mm wheel so even if both were optimised for their tyres its still a little over 40% more drag.
When they talk about the aerodynamics of the tyre being important, I wonder just how significant that figure really is.
There are fork legs, spokes. cyclists legs, cranks and frame tubes also creating drag in that part of the frontal area.
Is the magnitude of the aerodynamic gains a significant figure compared to those?
And does it matter to anyone who isn't capable of TdF type performance?
Epicyclo, they have quantified the aerodynamic loss of the different tyre size, all bikes have spokes and forks so that’s a consistent figure.
Agree that it may not matter to some. For some people having a 32mm tyre losing a small number of watts and being heavier than 25mm tyre won’t matter.
You don’t need tdf levels of performance though. People on this forum will be fast riders, solo and in group rides/races and will want their most performant set up as possible. For me doing a crit on closed roads, tends to be decent enough road surface and comfort for 1 hour 10 mins isn’t an issue, I want to have the fastest possible wheel and tyre set up.
If I was riding on broken roads, lumpy up and down sections for a long race, I’d probably be happy on wide rims and 28 or 30mm tyres. (Not 50mm though)
But with the existing rims I have, 23mm front and 25mm rear is proven to be the fastest combination. (Reynolds Strike, 62mm depth, 25mm outer and 17mm inner)
It's an interesting discussion. My questions are a) given that a bike is generally quoted at about .85 - .90 drag will the change from a given Tyre size, assuming appropriate wheel size, be enough difference to detect, relative to total drag.
B) given that drag is the square of speed, will people outside of top flight TT go fast enough to worry about Tyre drag?
Some excellent articles to read there, thanks!
I've recently gone from race style 23c on a road bike to 35 rear slick, 42 front gravel tread on a cross bike for my commute. There's a bit of a speed difference on smooth flat road, but surprisingly little most of the time... And it opens up lots of interesting route choices.
One thing no-one seems to have noted is the perception of gearing for bigger tyres. You're increasing the driven wheel diameter, so the effective gear increases too. Means that it can feel harder to push the same ratio on bigger tyres, giving the impression of more drag.