- My journey to the darkside is complete… do i really put 100 psi in the tyres?
Put some conti GP 4 seasons on my cx bike the other day.Posted 4 years ago
Have been doing mainly road miles on some cx tyres and decided i could be going a bit faster. Head scratching moment of do i really put that much pressure in the tyres?? It goes against all my tubeless 23 psi instincts.TiRedMember
Depends on the width of the tyre and your weight. For 23c and a 70 kilo rider you will need 100/110 PSI front/rear. For 25c this falls to 90/95.
There are lots of formulas for the optimal tyre pressure for load and width, that minimize rolling resistance depending on surface. If you ride on a poor surface, lower pressure wider tyres, correctly inflated, will have lower rolling resistance.Posted 4 years agoYakSubscriber
I’m about 65kg and go 95/105 psi front/rear on 23c.
Tried higher but it feels skittish. Sometimes go lower for bad weather, but have no proper evidence that it is more grippy. Its just that ” oooh, its a bit frosty, i’ll let a few psi out” habit.
edit – think I started from some Michelin chart somewhere then adjusted a bit after that.Posted 4 years agoMrSmithMember
Most people over inflate thinking it makes them faster, it doesn’t unless the surface is billiard table smooth ( get down and run your hand over Tarmac and feel how rough the surface is) it’s carcass deformation that gives you grip and lowers rolling resistance.Posted 4 years ago
70kg 23or24c 75psi front 90rear
have no proper evidence that it is more grippy. Its just that ” oooh, its a bit frosty, i’ll let a few psi out” habit.
well if its slippy out and the pressures are too high, then you can feel the tyres, erm. slip when cornering or climbing. I have occasionally had to get off on hills because the rear wheel was spinning underneath mePosted 4 years agorusty90Member
The call of the road is obviously strong at the moment – just put 28mm GP 4 seasons and larger chainrings on my Guerciotti at the weekend. At 70kg I’m running them at 95 rear, 90 front, which seems the best compromise between zing and comfort. Brought back fond memories of crisp mornings at the TT start with Clement No. 5s at 120 psi 🙂Posted 4 years agowhatnobeerMember
80/90 but then I run tubeless
Same here, when I ran 23c ProRace3’s with tubes I ran 90/95. I’m 63kg. No point in running higher than that for me with the quality of roads around here and my weight.
I’ve never run 28c tyres but I’d reckon 100psi would be too much unless you’re a very big bloke.Posted 4 years agoretro83Member
njee20 – Member
So they reckon 40:60 weight distribution on a road bike, so that’s 28kg on the front wheel for a 70kg rider, so 65psi… no thanks!
No, it’s bike + rider weight, and the 40:60 is just a guide line. Yellow pages under the back wheel, then scales under the front and sit on the bike; then swap to get an accurate ratio.
70kg rider + assumed 7kg bike on 23 mm tyres = 70 front / 105 rear.
Don’t write it off without trying it.
asterix – Member
at such a low pressure doesn’t your front tyre start to “squirm” when cornering fast?
Not that I’ve noticed. It gives the same effective squish on your front and rear tyres. Without carrying the track pump and trying a corner at e.g. 100/100 and 75/110 I don’t think you’d readily notice.
The main difference I have noticed is that the front wheel grips so much better and doesn’t skip over small bumps, and the rear wheel never bottoms out.
Works for me anyway. Nothing to stop you adding 10% to those figures, but according to the article, that’s the optimum balance between the amount of squish for the tyres to work properly over bumps and roll fastest.Posted 4 years agobrakesMember
^^^ same here, 100 is an easy number to hit, plus my track pump is knackered so I doubt it’s very accurate. even when it was new it can’t be that accurate anyway.
over a week my tyres go down by 10-15psi so are between 85 and 100 psi depending on when I last pumped them up. anything less than 80 psi just feels weird.
and remember for that ‘calculator’ it’s rider + kit + bike.
EDIT: why does a randonneur have more weight over the front than a racer?Posted 4 years agobikebouyMember
I have a Cervelo R5 which is quite “springy” and run GP4’s at 95 front and 110-115 rear.
I also have a Parlee Z4 which is solid as a rock and run again on GP4’s and …yes you guessed 95, 110 as before.
I do change the wheels though and Mav R-Sys which are light climbing wheels feel better at this psi, I’ve some carbone 40mm aeros and again run psi’s at the above.
I ride SOuth Downs lanes and they are full of potholes and shagged out surfaces..Posted 4 years ago
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