datlas 

You are doing it wrong.

genejockey 

At 140 psi, you might as well be running Armadillos.

LarrySellerz

The rider weight is important.. most of the tests are done with smaller riders. Also there is the financial aspect, the UCI has been compromised for decades and Big Gravel isn't much better. it's not like it will fail putting 40 extra psi of pressure in the tire... you could run 23s at 200 probably? The hard tire gives a harsher ride that feels faster even if it isn't which some people enjoy. A bike shop owner told me they overinflate tires for test rides for this reason, makes the bike feel fast.

KJ43

genejockey 

So, they aren't any faster, but they FEEL faster?

It's not just the harsher ride. They also handle worse. Instead of absorbing lumpy pavement in corners, they'll hop, and with all that centrifugal force, they'll hop sideways. You were asking about how to corner faster? That ain't how.

Seattle Forrest

The rule I've used is ignore the pressure rating on the tire, obey the one on the rim.

For the OP, I run 70 to 80 psi @ 28 mm depending on the day and what I'll be riding on.

Symox

I am gravitating to 85psi rear and 65 front
guess I just got used to it

Sy Reene

You're missing the point. All that you say is true, but those factors are all contributing to the excitement of bike riding that is lacking with more mundane pressures.

vespasianus

For some tires, yes, yes it will. Riding tires way over inflated will dramatically shorten the life span of the tire and could lead to a major issue.

Again, you have to listen to both. When Challenge says the max pressure in their tire is 50 PSI, use 50 PSI max.

There are nuances to these of course but making these statements as fact is dangerous and could get people injured.

ThermionicScott 

I dunno if I'd go that far. If Larry and his bike together weigh about 285 lbs, plugging that into the 15% drop calculator gives 130 psi for 25mm tires. He's only a bit north of that.

vespasianus

Which is a sign that he should not be using 25mm tires.

ThermionicScott 

It wouldn't be my choice either, but I've seen bigger people use smaller tires.

datlas 

If he asked me, of course I would suggest 28 but even at his weight he would likely do well at 100-105F and 110-115R. 140 is way too high. And the 15% drop rule is arbitrary, I am not an expert but pretty sure there is no science to that versus 18% or 12%. It’s a round number.

ThermionicScott 

Sure, 15% drop is arbitrary, and max inflation pressures have some margin around them. That's what makes it futile to boil this down to "right" or "wrong". If the tire doesn't blow off or wear funny, it works.

Sy Reene

You don't even need a calculator, just the ole charts. 285lbs @55% rear weighting, 25mm tire..
Maybe why Vittoria Corsas have 145psi max on their sidewalls.

genejockey 

Larry ain't even on the chart. Hell, I ain't even on the chart and I weigh 60# less!

Sy Reene

Those weights are PER wheel, not overall bike weight.

Symox

Reduced pressure by 5psi per tire and was surprised how much more comfortable and less bouncy on rough roads it was for downhills.

latest setting is 75 psi rear 60 psi front for 28mm GP5000

(at least on the rear tire) I felt 70 psi was too squishy and 80 bounced a bit on rough roads doing fast descents. Really surprised

scottfsmith

I am close to you (weight, bike model, tire model) and am at a similar spot on pressures as where you are at now. I run them a bit less in wet conditions.

Symox

that is very reassuring- thanks

Sy Reene

I don't know if I find it humorous or what, but you're pretty much matching the Berto graph chart a couple posts up for a 45/55% F/R split on your total weight.

What is tangentially interesting is how most everyone might suggest that the LarryS scenario of 140psi in 25s is way too much, but this same chart also says that's correct. What would cause the Berto vs "Modern" models to incrementally diverge further apart from one another at higher rider+bike weights?

rm -rf

I saw your previous posts, and was going to suggest a gradual change to any new pressures. For instance, go from 80 to 75 instead of 80 to 70. It takes a few rides to have the new pressures feel normal instead of weird.

It's interesting how many of the riders in this thread are using similar pressures, or scaled similarly to their different weights.

At 170 pounds, I was using 65 and 72-75 psi. Now, it's usually 70-72 and 78-80.

Fredo76

I weigh 220 lbs, and am running my 28s (different brand) at 80/85 psi f/r

vespasianus

They are a different brand of tires.

Silver Steve

I find the Silca calculator to be pretty spot on.