• This topic has 46 replies, 35 voices, and was last updated 8 hours ago by timba.
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  • Road tyres – speed vs girth ;-)
  • letmetalktomark
    Full Member

    I currently run a pair of Panaracer Gravel King Sks on my “road” bike in a 38mm size.

    These actually size up as 40/41.

    I like the tyres but they are a carryover from when I used the bike for more gravel than it sees these days.

    The wheels are Hope’s 20five so I’ve room to space down to circa 28s but find myself looking at 32s as they seem a reasonable balance but are they likely to be any faster – I’m likening of replacing like with like albeit less girthy.

    robbo1234biking
    Full Member

    I have 32mm GP5000’s on my bike at the moment for winter duties. They roll really fast and are very grippy. Would be a lot quicker than gravel kings. 32mm is pretty comfy as well. I run them with tubes in at around 45-50psi and I am pretty chunky (90kg).

    fasthaggis
    Full Member

    If you look at what the Audax riders are using these days,there has been a move to 30-32 tyres.
    TBF some of the bigger gravel tyres(like the gravel kings) roll pretty good.
    I suppose it depends what kinda mileage you are planning and what speed,comfort and performance you want.
    I still run 23s on my road bike and the first ride in the spring is a bit of an ambush 😃

    rt60
    Full Member

    GCN did a piece on this and basically said go for the 32’s unless racing.

    chakaping
    Free Member

    I’m on 28c and would go 30 or 32 next time.

    tjagain
    Full Member

    Ive ridden the same bike on 23 and 32 wide tyres. The 23s were a tiny bit quicker (subjectivly) but the 32 a lot more comfortable and most importantly to me much more grippy. I treasure grip above anything else for riding

    Jamz
    Full Member

    It’s a shame they are Gravel King SK and not slicks as the slick makes a great winter road tyre. If I were you I would buy some 38mm slicks for winter use (Panaracer currently have all their tyres discounted on their UK site). I don’t think there’s any point going down to 32mm (unless you live somewhere very hilly?) – would rather have the bigger contact and extra comfort in poor conditions. Plus I reckon a bigger tyre is faster on rough roads at normal riding speeds. I would then change to a fast 30/32mm tyre next summer. FYI I have 44mm slicks on my winter bike and 32mm on my summer bike currently – very happy with both choices, definitley won’t be going back to 28mm tyres unless I move somewhere abroad with lovely smooth roads.

    infovore
    Full Member

    I ride GravelKing 35 slicks on my road wheels, because it’s a gravel bike really and 32s felt very skinny. They are… fine? I certainly keep up with riders around my fitness level, it’s a little more plush. And as they’re tubeless, the pressures aren’t mad hihh I’d probably use 32s on a skinnier bike.

    I briefly looked into rolling resistance and as long as the tread is suitably slick… I right now would gain more from weight loss or a bit more training than I would from a skinnier tyre. Yes, the rolling resistance is larger, but right now, not in a way that is meaningful.

    TiRed
    Full Member

    I rode an 18c on the front of the trike, (not a typo) with a HED3 narrow rim and best aero profile, but had to move to 21c GP4000s as they are no longer made (can’t think why). Tbf there are three tyres. As for other road rides, I’m a 25c GP5000 rider, but have some G One Speeds in a 32 that seem to roll just fine as well. For more comfort, I’d probably go to a 28c for Audax style rides, but wider rims than Open Pros (19mm internal) are probably better for 32c tyres. Although not stated, modern 25c come up like old school 28c tyres anyway, which is why everyone switched to racing 25c.

    Speed-wise, wider rolls faster at the SAME pressure, but you don’t run a 32c at 100PSI, so it’s probably moot. you will get an aero hit though.

    letmetalktomark
    Full Member

    Thanks folks.

    Some really useful information there.


    @robbo1234biking
    GP5000s would be up there on my list but they are at the prohibitively expensive end of the spectrum.

    A couple fo other factors(?) …… I live in Suffolk so no hills to speak of but lots of false flats where maintaining speed is critical.

    Mileage wise I am wanting to up my endurance and eek out further rides but current spins are circa 40-60kms so by no means far.

    MoreCashThanDash
    Full Member

    Running slick Gravelkings in 32mm on my winter bike, 30mm Duranos on the summer bike.

    Any issues of girth affecting speed are unrelated to the tyres.

    zilog6128
    Full Member

    Schwalbe did some real-world testing on this years ago, plenty of info if you google it.
    the whole “narrower is faster” thing is a bit of a myth unless speed is high and the road surface is good, especially when talking about tubeless.

    J-R
    Full Member

    I treasure grip

    What a lovely turn of phrase – and so true.

    tjagain
    Full Member

    the whole “narrower is faster” thing is a bit of a myth unless speed is high and the road surface is good,

    Try riding a fat bike the extra drag from the wide tyres is obvious

    the only testing I saw was very flawed

    cp
    Full Member

    This thread just cost me a set of panaracer gravel king slicks 700×32 for the winter bike.

    zilog6128
    Full Member

    Try riding a fat bike the extra drag from the wide tyres is obvious

    how is that relevant to road tyres 🙄

    there’s always one 😂

    n0b0dy0ftheg0at
    Free Member

    I’ve been riding GP5000s, 23/25mm up front (latter after getting a possibly dodgy sidewall split mid summer) and a 32mm on the rear. Typically ~95/85 PSI up front, ~80 on the rear, with latex tubes. Relatively aero for leading edge of bike, with comfort under my saddle. Felt speedy when I felt hell of a lot fitter than I’ve been for the last two months.

    w00dster
    Full Member

    Depends on what you’re after really, for race level speed then 25 to 27mmm. I love my 27mm Challenge tyres, and being honest, set up tubeless they are fast and comfortable. Grip is really good. Never had any issues racing or training in all weathers.
    But….I also have 32mm Challenge Tyres and also 38mm Rene Herse. All slicks. All of these tyres are quick enough and will be quicker than the Gravel Kings SK, but they’re not as quick as the 27mm tyres on my “fast bike”.
    I’m enjoying being a tad slower and having the comfort of the wider tyres. I’d never race in anything over 28mm, but that’s because for the crits I do/did it’s just not needed.

    Loads of people will say Renee Herse has proven wide tyres are just as fast…..as someone who really likes wide tyres, I’m not 100% convinced in this. Also need to remember that the people saying wide tyres are just as fast tend to be the people selling wide tyres. But they are super comfortable and you’re not really giving up much speed, a little bit more weight maybe, but take your pick in what’s important for you.

    dickie
    Free Member

    I replaced my 32mm GP5000 with Pro One 34mm (thought I’d ordered 32mm) & have seen no difference in speed.

    MoreCashThanDash
    Full Member

    This thread just cost me a set of panaracer gravel king slicks 700×32 for the winter bike.

    *waits for commission cheque tocome through “

    timc
    Free Member

    In my experience the choice of tyre will make more difference to speed & comfort over a small size difference between 28/30/32.

    GP5000 / 5000S are nice, fast & grippy, but wear out pretty quick, I’ve switched to Michelin Power Road, better wet weather grip, better wear rates, maybe a fraction slower rolling initially but my speed has actually gone up, so splitting hairs.

    thisisnotaspoon
    Full Member

    Rolling resistance is only half the equation though, there’s also aero drag from both the tyre and it’s interaction with the rim.

    27-28 feels fastest to me, somewhere between that and 32mm keeping up with clubruns becomes really hard work.

    Depends on rims though, supposedly a 28mm tyre on a matched rim is faster than a 25mm tyre on an old-fashioned narrow rim.

    Next time I buy wheels that’s what I’m aiming for (28c and matched rims).

    tjagain
    Full Member

    how is that relevant to road tyres

    Because it show that there are more factors at work than wider is faster because fat tyres are clearly slower

    crosshair
    Free Member

    One thing to consider is that the comfort pressure for each sized tyre will change.
    You can actually make a 25 feel like a 32 but then of course you’ll be running the risk of pinch flats or burping.

    At the same “comfort pressure”- the rolling resistance differences no longer exist either: the same compound tyre will roll the same.

    That said- I like my 32 tubeless 5000’s mainly because you have a little more air and time to play with before the tyre is off the rim and you’re skating down the road 🤣

    I have to be honest- there’s not a massive difference riding my 700×38 or 42 Pathfinder Pros. And even my 2.25 rocket Ron’s on the xc bike only seem to really cost watts over 20mph.

    cp
    Full Member

    *waits for commission cheque tocome through “

    you know what, I’m going to post a link to amazon in the hope that Singletrack gets a commission from any click throughs (as much as it pains me to use them and I’m not sure how all the click through commission thing works but I doubt STW get commission from Panaracer direct).

    £29 each

    Daffy
    Full Member

    I run 32s on the road bike. They’re significantly faster/easier than 37>40s, especially above 30kph.

    The longer the ride the more you feel it.

    bensales
    Free Member

    Member of the 32c massive here as well. Conti GP5000 for the summer and Conti GP 4 Seasons for the winter. Run at 80/85psi for my svelte 115kg is comfy and fast.

    Had to put some 25c GP 4S on temporarily recently before the 32s turned up and it was horrible. Had to run at 95/100psi, horrendous ride quality.

    dovebiker
    Full Member

    My ‘road’ wheels for my Diverge are 32mm Gravelking slicks and suit my local riding perfectly, plus if I want to detour for a few miles of forest track, then I can without rattling my fillings loose. I run them tubeless at around 40psi.

    Northwind
    Full Member

    I went to 35s, tbh I think they were probably slower rolling than my 28s overall, but they definitely felt more secure on my local freshly ploughed tarmac and so I carried more speed a lot of the time. No idea if that cancelled out, but it definitely could

    Saccades
    Free Member

    Have spec Roubaix 30/32 on my hope five20, appear bombproof and are great on the Sunday road clubrun. Gallons of grip with tubes at 65psi and over 100kg.

    I moved up from 28s as roads are rough, no noticeable change in speed.

    kerley
    Free Member

    The differences are so small as to be irrelevant unless you are racing and everything adds up.

    I road 25c road tyres on road and gravel, 33c dry CX tyres and I am currently riding 44c tyres.
    There is no consistent difference over any 1-2 hour loops and I see bigger differences using the same tyres depending on good I am feeling on that day.

    What is consistent though is how much more comfortable the 44c tyres are and how less tired I am after a ride due to that.

    jimdubleyou
    Full Member

    I’m currently on 32s tubeless (GP5000 TR) on the “road” wheels and wouldn’t go lower – but I don’t race and rarely ride in a group so if I’m slow I don’t notice.

    I’ve got some Byway 44s that may well go on instead if the GP5000
    wear out soon.

    tthew
    Full Member

    Interesting article in/on Cycling Weekly about this plus other wheel speed tech. By a proper engineer who’s done some proper controlled scientific tests into such things. Clicky.

    In your circumstances, you may actually be better sticking with the wide tyres at lower pressures. Goes against received wisdom.

    Frim the article, (quite a way down)

    That said, he would recommend the bigger tyre because it can be run at lower pressure for improved rolling resistance.

    So in the future will road wheels actually be designed for 30mm or even bigger?

    “Ultimately we are driven by tyre development on that front,” says Tate. “The choice might be thinking about what makes a tyre width faster and we are increasingly understanding that it’s the ability to run a lower pressure.

    TiRed
    Full Member

    Interesting interview. But there was one obvious point:

    Tate reports, for example, that the new Parcours Disc² tests no slower with a 30mm tyre despite being optimised for a 28mm.

    Disc is on the back behind the seat tube. They didn’t try this on the front.

    If you’ve ever ridden a TT bike on a gusty day with a 900 mm deep section on the front, you’ll know that there is a limit to rim depth (and why 900 mm front wheels are relatively cheap second hand!). the accelerometer data would show less high frequency vibration for wider tyres at lower pressure. Whether that vibration and movement matters is moot for stability. The aero effects of a wider tyre on the front are, however, easily quantified in a wind tunnel and they are real. You won’t see anyone riding a 32c (or a 28c) on the front of a TT bike. You might see one on the back though.

    molgrips
    Full Member

    Weeell, I have Schwalbe Pro Ones in 28c on my road bike and they are great on the shittiest road surfaces I have around here, including some pretty broken sections. I run tubeless at 57psi roughly at 90kg. But then, I do have 19mm rims.

    I have no plans to go larger. Partly because they won’t fit under my mudguards but mostly because I don’t see the need for anything larger on my local roads.

    Definitely faster than 23s on my old bike. On tarred and chipped sections on that bike I could feel the buzz slowing me down.

    Jamz
    Full Member

    Disc is on the back behind the seat tube. They didn’t try this on the front.

    If you’ve ever ridden a TT bike on a gusty day with a 900 mm deep section on the front, you’ll know that there is a limit to rim depth (and why 900 mm front wheels are relatively cheap second hand!). the accelerometer data would show less high frequency vibration for wider tyres at lower pressure. Whether that vibration and movement matters is moot for stability. The aero effects of a wider tyre on the front are, however, easily quantified in a wind tunnel and they are real. You won’t see anyone riding a 32c (or a 28c) on the front of a TT bike. You might see one on the back though

    For anybody not racing the aero aspect is irrelevant though – the rolling resistance reduction from wide tyres easily outweighs aero losses at lower (normal) speeds on average UK roads.

    Also, my Roval Rapide CLX front wheel is 35mm wide so I wouldn’t be overly bothered if I had to race it with a 32mm tyre on, especially not on a sporting course.

    27-28 feels fastest to me, somewhere between that and 32mm keeping up with clubruns becomes really hard work.

    This is absolute bollocks. Same tyre at the correct pressure will no slower. Last weekend on a club run I did 70 miles/3700ft at 19.3mph average on 44mm tyres (38psi) and it was dreamy.

    molgrips
    Full Member

    Because it show that there are more factors at work than wider is faster because fat tyres are clearly slower

    The ‘wider is faster’ slogan refers to road bikes, where 23 is skinny and 32 is fat. Within that context the fatter end of that spectrum is faster.

    endoverend
    Full Member

    This is making me feel old, and my kit vintage. I remember when I first put 25’s on my race bike and took them straight off because thought they looked bulbous ridiculous and slow… eventually succumbed, but that’s the largest that’ll go through the frame, and not going to upgrade it until its broken because there’s nowt wrong with it – in fact, with a quality frame and wheels I don’t feel the need for any more comfort than on 25’s – and struggle to see how adding a few hundred grams of excess rubber on the rotating edge of the wheel is going to make me any faster on a long Alpine climb unless physics is being marketed differently these days. Started out on 19’s at 120psi+ so maybe have buttocks of steel. 30c+ to me is a gravel bike, but yeah gravel bikes can be quite fast…

    molgrips
    Full Member

    struggle to see how adding a few hundred grams of excess rubber on the rotating edge of the wheel is going to make me any faster on a long Alpine climb

    In the alps it might not. They tend to have very smooth roads. But even then, having a wider tyre at lower pressure gives a wider and shorter contact patch which apparently has less RR.

    On rough UK spec roads there’s no contest. It smooths out so much buzz and vibration that would otherwise slow you down.

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