The weekend before last I did a longer ride and had an old puncture repeatedly open up (this is tubeless) until I remembered I had anchovies and sorted it out. Later that week I took the tyres off to refill and repair the small cut with a patch on the inside. To test it out I went on a 1hr ride (spoiler*), but wary of blowing the freshly applied patch I dropped the tyre pressures to 55psi in my 28mm tyres. Given I weigh 87kg this is quite low. Although I do have 'wide' 19mm ID rims.
The bike felt surprisingly sprightly straight away, I was flying. There was no squirming or bouncing either. So the next day I rode to my folks which is 118km with 630m of ascent on main roads, which are a mix of smooth and really very coarse surfaces. My previous best time was 4.5hrs with an average speed of 26.5 and this time I did it in 4h01 (bah!) and an average of 29.5. The bike felt really fast again.
So is it possible that the optimum tyre pressure is that low for someone of my weight? Has anyone tried really lowering pressures this much and comparing speeds?
* tyre stayed up
Your in Cardiff no ? - everywhere out of Cardiff heads north essentially unless your swimming right ?
Unseasonably high southerly winds probably had more of an effect than tire pressure
Noted as conversely I was heading south and was buffeted all the way with correspondingly slow average speeds
everywhere out of Cardiff heads north essentially unless your swimming right ?
No you can go east and west too.
Unseasonably high southerly winds probably had more of an effect than tire pressure
I checked that (obviously, cos you know, science and that) and noted it. It wasn't a windy day at all, not in the morning at least, just occasional light gusts which were from the side at first and then later from behind. But they were slight.
And the previous day I also got a string of PRs on the local loop.
What's your normal tyre pressure for the 28s?
I run mine about 60psi (although I'm about 76kg) and noticed a similar increased comfort-and-speed benefit.
This is on a new-to-me bike with stiffer frame as well as the bigger tyres though.
The latest Zipp 303s are wider internally than your wheels, but when they came out they made quite a big deal about wanting to be run with what feel like bizarrely low pressures.
Anecdotally I've been experimenting with lower pressures as well and while I'm not setting any fresh PRs it's been nice and comfy without the dreaded squirmy feeling.
EDIT: about 80psi for me, at around 83kg rider weight on 25mm GP5000s with Reynolds AR X 41 dbs (21mm internal width). Maybe I should try ~70psi...
I'll give you north east and north west but unless my maps broken east and west will have you in the sea only a little after heading south.
I did it in 4h01
You know what you're going to have to do now though, right? Good effort BTW!
I run my commuter tyres as this sort of pressure (there's some rough-ish paths), and don't feel like they're super draggy.
Power meter?
Look on Mywindsock.com to see what weather impact was.
I am lighter than you and on my road bike that low a pressure feels horrible. squirmy, bouncy and smacks the rim on potholes
on my road bike that low a pressure feels horrible
Yes but your road bike is older than I am.
55psi in my 28mm tyres. Given I weigh 87kg this is quite low.
Matter of perspective. 55PSI that in my money high end of my usable pressure.
OK, I'm 67kg, but my low is below 40PSI in 28c (38-35 probably)
Best results of speed and comfort combo for me is just smidge above 40PSI.
Cheers!
I.
55PSI in the rear 28mm tyre, with you weighing ~87Kg? 😮
I use ~73PSI on my rear 32mm GP5000 and ~93PSI on my front 23mm GP5000, with me weighing ~83Kg these days, on the road bike.
On the commuter hybrid, I think I topped up the front 35mm Marathon Supreme to ~70PSI and the rear 40mm Vee Speedster to ~80PSI (to try and reduce chance of debris getting stuck in honeycomb tread and being driven into the tube over time) last night.
Last time I recall using ~55PSI was on the front 38mm Marathon Cross on the hybrid and that felt borderline squishy.
I've plotted everyone's findings on a graph, and as expected it shows that with Zero psi I will be travelling at the speed of light.
But seriously, I've been out on wife's road bike without checking the pressures, and it's felt absolutely fine at 50psi on 28mm, no draggyness at all. However, on my road bike with 23mm, lower pressure is rubbish. I've no idea what or why.
Nokia published a study on this subject a long time ago, but basically I think found that at lower pressures the tyre can deform around an obstruction rather than having to climb over it.
@Molgrips without power and or wind data, there could be many other explanations, but as a scientist you will know that and also the power of a personal anecdote.
I am lazy and often find my 25 tubeless tyres at 20-40, which feels ok, I pump them back up to 60-70. I don't measure enough things to know what the effect is.
Nokia published a study on this subject a long time ago, but basically I think found that at lower pressures the tyre can deform around an obstruction rather than having to climb over it.
Yep, less deflection.
What's it got to do with old-fashioned mobile phones though?
On a smooth surface the higher the pressure the lower the rolling resistance.
But on a rough surfaces Lower pressures offer less rolling resistance. If a bump creates vertical motion your being slowed down. Every bump that comes up into you and the bike is lost energy.
I started off with the max rated of 70psi thinking 'there's no way I can go lower than that'. Then I dropped to 65 thinking that was plenty low, and hoping it would help the tubeless. It was straight to 55 this time.
I am lighter than you and on my road bike that low a pressure feels horrible. squirmy, bouncy and smacks the rim on potholes
The secret apparently is wider rims coupled with wider tyres. One of those two things doesn't help.
You know what you’re going to have to do now though, right? Good effort BTW!
I know! There were temporary traffic lights on one bit too, which I had to stop at. On the other hand, I caught greens at Asda in Hereford. I stop my Garmin if I have to stop to fix something, but I don't stop it for traffic lights or breathers. Garmin had me down as 3h59m46 moving time and 4h04m43s total. 5 mins of stops is pretty good I think, part of that was me stopping to check something stuck to my tyre.
Blinking auto correct. Whatever happened to Nokian anyway, used to love their tyres.
What’s it got to do with old-fashioned mobile phones though?
Nokia (or Nokian) started off making rubber, they then branched out into electrical cables, then spun off into electronics, communications equippment and phones. The rubber company still makes tyres under the name Nokian, which is means 'from Nokia' which is the town they're from.
I also noticed less deflection and slow-down from lumpy bits and undulations even when the surface itself was smooth.
there could be many other explanations
Of course, the point of the thread is a) to show off about my awesome ride and b) to point out that what seems unfeasibly low could work and actually be better, without downsides, so you could give it a try.
Just like with MTB tyres it all comes down to internal volume:
I'm a similar weight to the OP, running 25mm tubed tyres on similar width rims, I've found going down as low as 70psi beneficial for comfort and rolling without squirm. Obviously with tubes and a narrower tyre I've probably got significantly less internal volume.
A slightly wider tyre and rim, plus the removal of a tube mean you've got a bit more internal volume and compared with 23/25mm and tubes can comfortably reduce pressures by ~20-25% and require less pressure to optimise the ride characteristics of the tyre...
Gravel bike has 38mm tubeless tyres on 25internal rims and can be run mid-low 30s for on/off road use, again without squirm...
Personally I prefer slightly less pressure in the front tyre, there's less of my bulk over it and it helps more with arm/neck comfort (IMO/IME), so if I were going to pick one tyre to be higher volume and/or tubeless it would be the front...
I've been running 45/50 in 32mm tyres and that gives what seems to me to be good compromise between speed and comfort. I've also done lightweight touring at this pressure - saddle bag and bar bag no tent or cooking gear. Coming off the Grand Ballon in heavy rain they felt very confidence inspiring.
Jan Heine has written at great length about appropriate tyre pressures.
FWIW I use 50 front 55 rear in 28mm Contis on 19mm rims, the tyres measure 30mm across. I'm 76kg, the bike's probably 10kg. That doesn't feel really low to me. Light 650 x 42s at 35-38 psi are another level of easy rolling.
Nokia (or Nokian) started off making rubber, they then branched out into electrical cables, then spun off into electronics, communications equippment and phones. The rubber company still makes tyres under the name Nokian, which is means ‘from Nokia’ which is the town they’re from.
Every day's a school day.
🙂
And it's nice that we appear to have reached a consensus for once: lower pressures are great in modern tubeless road tyres.
molgrips
On the other hand, I caught greens at Asda in Hereford.
You jammy barsteward - one of the worst designed junctions I've ever had the misfortune to negotiate. It makes me anxious me in the car (as a local who's been using it since the start) - there's little no chance I'd consider it on a bike!
Nope cha****ng - I loathe low pressures. makes the bike feel horrid.
I think this comes from motorcycling where that feel of tyre squirm because of low pressures means you have a puncture and are likely to crash
People run their bikes at pressures that I simply could not ride
I run 28mm on my commuter bike and over the years have gradually reduced pressure from 80 or 90 to 60ish. Seems more comfortable and faster…
If the bike would accommodate them I’d actually go to 32 mm at about 50psi.
TJ - what width of tyres are you using and are you tubeless?
Nope cha****ng – I loathe low pressures. makes the bike feel horrid.
Me too, but my point is that at 55 I got no squirm or bounce. It's a combination of wide tires designed for low pressures AND a wide rim. Guessing you have neither on your road bike.
I used to run Specialized Butcher/Slaughter on my Salsa, with suitably wide rims (23mm ID) and I had to run 35psi to avoid squirm and bounce. With Racing Ralphs in the same size and on the same rims I run 22psi and get no squirm. Any lower and it bounces if I spin fast but is still completely rideable.
So a lot is down to the tyre carcass.
You jammy barsteward – one of the worst designed junctions I’ve ever had the misfortune to negotiate. It makes me anxious me in the car (as a local who’s been using it since the start) – there’s little no chance I’d consider it on a bike!
I dunno if you're a born and raised country bumpkin 😉 but it's nothing compared to some stuff I've ridden in the big cities. Even Cardiff has worse e.g. Gabalfa roundabout and/or flyover.
No squirm you feel molgrips - I bet I would find it unridable. Yes tyre type and width and rim width alters it but I just think I am very sensitive to this because of the motorcycling. Deep in my reflexes / brain I have a fixed idea that tyre squirm means a big crash is coming
TJ – what width of tyres are you using and are you tubeless?
It doesn't matter - I get this effect on any bike even my fatbike. tubeless or not, skinny or wide. I have ridden friends bikes I find unrideable because of the low pressures they run
Its not about the bike - its about me.
Having yet to try tubeless, I can only guess that these super low pressures talked about feel very different when the air pressure isn't just inside a tube. Like tjagain, even on my fatbike, I felt the need to run the rear 4" Jumbo Jim at ~22PSI+ on tarmac and often close to ~27PSI... Otherwise with a tube (sometimes with a "stretched" SV13F, other times a proper size SV13J), it felt really odd as if a slow puncture was developing, not to mention it felt incredibly draggy on tarmac.
No squirm you feel molgrips – I bet I would find it unridable.
Very seriously doubt it I am extraordinarily picky. I'm very well aware of squirm and bounce. What I am saying is that just like you I would have thought 55 too low and would result in too much squirm. However the difference between us is that I have actually tried it on this tyre and rim combo, and you haven't. Don't assume that your previous experience applies in all future situations.
Having yet to try tubeless, I can only guess that these super low pressures talked about feel very different when the air pressure isn’t just inside a tube.
It's to do with tyre construction as well as widths. Carcass construction is changing as we move to tubeless.
It doesn’t matter
Erm, if you've not tried what Molgrips is describing, it does make your verdict on it a bit redundant TBH.
Classic TJ…
I used to run Specialized Butcher/Slaughter on my Salsa, with suitably wide rims (23mm ID) and I had to run 35psi to avoid squirm and bounce. With Racing Ralphs in the same size and on the same rims I run 22psi and get no squirm
Hang on a minute, you're saying that the notoriously flimsy Racing Ralph has a stiffer side wall than a Spesh Butcher - which is essentially what stops tyre squirm once you eliminate pressure.
Its not about the bike – its about me.
I feel the same. I don't have a pressure gauge so no idea what pressure I run but I know it is high as I can't squeeze the tyre down with my thumb. Tried lower pressure as know it could be faster/easier rolling but I don't like how it feels at all.
Run pressures that are probably way higher than ideal on all bikes I have owned.
Its that squirm others cannot feel makes me feel very uneasy. Its repeated many times on many bikes with many different combos of tyres. Its about what I feel and like
I am sure moley is right for him.
Most folk would think I run far too high pressures. We ain't all the same
You jammy barsteward – one of the worst designed junctions I’ve ever had the misfortune to negotiate. It makes me anxious me in the car (as a local who’s been using it since the start) – there’s little no chance I’d consider it on a bike!
I dunno if you’re a born and raised country bumpkin 😉 but it’s nothing compared to some stuff I’ve ridden in the big cities. Even Cardiff has worse e.g. Gabalfa roundabout and/or flyover.
As someone who used to drive a slow, big van through both areas on a regular basis I can confirm that the Hereford Asda junction is a pussy cat compared to a few places in Cardiff, some nasty ones in Newport too.
Its that squirm others cannot feel makes me feel very uneasy.
i used to ride with someone who claimed to need his suspension pressures set to the exact psi.
i also used to let some out every now and then when he wasn't looking.
he never noticed...
Brilliant 🙂 I can tell you if a tyre is soft tho
Its that squirm others cannot feel makes me feel very uneasy.
I guarantee if it were squirming I'd notice. I just lowered my saddle by 3mm, and it was a big improvement. Yes I am that fussy.
Anyway, I used to run 100psi in my old 23cs on narrow rims. For the reasons you cite. But now I'm on nearly half that, because modern technology. The point is that the old knowledge you used to have, those old comfortable ideas that took root in your brain, they may not apply any more. Things you thought would be wrong can actually be right now.
I had a Tubeless puncture that (after a while and a lot of spurting) sealed itself today. I normally run 80psi at 101kg on 28mm Hutchison (really long tyre name, storm compound 11 in there somewhere).
I stuck a bit more air in but my mini pump is a bit poor and I only had 10km or so to go.
It was clearly lower pressure than I normally run but actually felt OK; I checked when I got home and it was about 58psi. I didn’t hammer the last section home so I have no idea on times, but it made me think about maybe trying say 70psi for a while.
As previously mentioned in the thread Jan Heime here and elsewhere throughout his tech info has loads of verifiable data and tests showing lower pressure (outside of a velodrome) is beneficial.
I know lower pressures are beneficial, but I don't like how they feel and am happy to ride my bike with almost solid tyres, same as TJ.
I don't like standing climbs with low pressures, I don't like skid stopping with low pressures, I don't like cornering with low pressures.
I don't like riding with too low pressures either.
But with modern tyres and rims, what constitutes 'too low' is a lot lower than it used to be.
I didn’t hammer the last section home so I have no idea on times, but it made me think about maybe trying say 70psi for a while.
Sealant works better at lower pressures, so more likely to seal. Also - use anchovies.
Most folk would think I run far too high pressures. We ain’t all the same
I’m the other way and run low pressures. Not road bike though. Stooge and WTB 40’s I have nine PSI up front and 13 back. Running a pair of Teravail Coronado 3.0 with the light casing. Might have to go to low double digits up front after I got a bit of squirm on a sharp corner.
Some of the pressures mentioned on here are obscene, 60! 😱
Sealant works better at lower pressures, so more likely to seal. Also – use anchovies.
Left the pack in the bar bag on my gravel bike. What anchovies for road bike that don’t take up much space?
Some of the pressures mentioned on here are obscene, 60! 😱
This is a road tubeless thread…
my (35mm, marathon plus tyres) showed 21 psi last time I checked. Normally pump them up to 40 then leave them till the handling goes funny and the squelch on sprints. I'm 100kg with my bike and gear on. They feel a little quicker when pumped up, but I don't notice going slower as they drop.
I experimented tonight, 70kgs, running 28mm tubeless tyres on a 21mm internal rim. With a power meter. 8.5kg bike. I had 55psi in and there was no difference in my average speed. I didn’t feel a squirm or a rim ding, but I wasn’t as confident in the faster corners.
I only tried pushing hard on a couple of segments, but don’t think there was any speed difference.
I might try this at lower pressures later in the week. My local short loop is 27 miles, I normally average anywhere between 19 and 21mph on it. Will try at 50psi on 27mm tyres(new Challenge Strada tyres due in the next day or so).
This is my normal bike with my normal tyres, just new ones. Ive done this loop countless times in all winds. I very rarely get any new PB’s.