chas58

I had always thought one of the avantages of tubular tires was there ability to run at higher pressures leading to less rolling resistance.

This article implies that tire pressure does not make much of a difference at all, and that high pressure with tubular tires on smooth surfaces is actually a little slower.

Some quotes:

Is this relevant to track riding?
What PSI do you ride at?

Reference article from 2-17-2015:
https://janheine.wordpress.com/2015/...a-and-details/

dunderhi

The need for correct pressure for the tire size and rider weight has been known for decades, so I'm not sure why people think fat tires at lower pressures is something new. I raced on 25c tires back in the '80s and 90psi was plenty. Downhill coasting races were a regular easy-day occurrence. I guess that's how we figured it out.

The optimal tire pressure is based upon the tire design, tire width, rim width(primarily clinchers), and rider weight. Today, I ride 25c clinchers on 24.5mm rims at 90-100psi (very heavy rider) on the road, but on the track, it is 22c/23c tubulars at 150/145psi respectively. If I am in a pursuit, then it's 19c/22c tires at 190/175psi respectively. I've never downhill raced my pursuit bike, so I don't have any solid data for my pressure choice. Maybe one of those powermeter thingies might help.

queerpunk

For starters, take anything that Jan Heine says with a grain of salt. He'll find a way to dig up data that says that a randoneurring bike from the 1970s is objectively the best, no matter what you want to do on a bicycle.

Secondly, yes, lower pressures can be faster on the road.

Road and track have very different demands. On the track, low pressures can severely compromise handling on banking, maneuvering at the speeds we see.

And, we don't have "rough pavement" conditions (well - some tracks do, but that's beside the point). His analysis is based on the fact that lower pressure allows the tire to keep the system moving forward, rather than converting forward momentum to upward momentum (bouncing) when encountering obstacles. That's very important information for roads. That is not useful information on a track.

gtrob

exactly. On rough road the tire has to conform to imperfections, and too high of a pressure causes it to bounce and go over instead of 'through' the bumps. It doesn't take much, even smooth pavement is very bumping compared to track wood.


On the track (smooth wood), higher pressure is faster. Much faster. Most race tubs have a minimum of like 160psi

Brian Ratliff

Tire pressure acts as suspension for the bike. On the road, where you are traveling over chipseal-ish surfaces, wider, lower pressure tires allow for a softer suspension so the mass of the bike/rider is not moving up and down (this takes energy - the only source of which is your legs - which is not going towards moving you forward!). On the track, with the exception of some rougher tracks (Alpenrose, for instance, sometimes heavier people benefit a bit from wider tires), the surface is very smooth. Like, railroad track smooth. This means that higher pressures are beneficial to rolling resistance.

TL;DR:

• As the surface gets rougher, wider, lower pressure tires act as suspension and reduce up-down movement of the CG of the rider and equals faster rolling.
• As the surface gets smoother, higher pressure tires decrease tire casing deformation and decreases rolling resistance.

The takeaway: The question "what is the best tire pressure to ride" is highly dependent on the surface you are riding and your weight. There is no one right answer.

I ride 23mm tubulars at 155psi.

Quinn8it

Try riding 90psi through turns 3-4 at 40mph..

wens

Also, you can easily pull 2+ g's on a steep track

Brian Ratliff

That too. Squishy squishy.

chas58

Good point!

He did seem to say that higher pressure works better on a rough road than on a smooth road (something about the imprint of the rough road on the softer tire...???)

Good point about the G forces. I think the FCV has some people hitting 3-4G in the turns, but that is a way tight track. Still, on a typical 200m track, we are doing 1G at 17mph according to the track designer. 35mph is a lot of force in the turns

I'm thinking that going for the ultimate max PSI that I have been obsessed with is probably not too nescessary. I'm not going to be riding around at 90psi either.

aramis

I've run 90/100 psi on clinchers at the local outdoor track in endurance races and it was no big deal. I don't know if it was faster or slower but I didn't notice any weird handling.

Note quite 40mph but I think there is a big difference wood vs concrete and even the surfaces at different concrete tracks varies widely.

How many velodromes in the US are wood vs concrete?

nspace

90 psi with my tubulars (Veloflex Record) on wood track 42 banking definitely doesn't feel great, and I am only 140 lbs. I've found 130 psi to feel much nicer on the track. There is something unsettling when you can feel the sidewalls conforming too much in the turns.

Brian Ratliff

It really depends on 1) how banked the turns are, and 2) how much you weigh. If you are on a shallow track (333 or 400m) and you weigh 150lbs, you can ride anything at any speed. If you are at Alpenrose and weigh over 200lbs, you start getting sensitive to how your bike handles in the turns.

Quinn8it

But did you win?

TrackMonkey7

+2 I think there shouldn't be any hard and fast rules in regards to tire pressure, given the variables involved. Surface, weight, and preference all play a role.

When I got my tubulars, I thought the pressure range was 155-220. I ran them at 145 at Kissena, thinking that sounded a little high. At the end of the first race in turns 3 and 4, I couldn't help but swing wide as each bump pushed me further up the track. I'm surprised I didn't hear any expletives from behind. Now I run them at 100-110 for Kissena.

Meanwhile at T-Town, I ran them at 120-130, and still felt like I could have gone higher on them.

rensho3

I made the mistake of running 160 at Colorado Springs a few years ago when I did my 500 TT. I bounced badly between three and four, overcorrected and ran over several sponges coming out of four. Missed a PR by .5 because of it. I weigh 150. I ran 125 for the rest of Natz and everything handled much better. I continue to run 160 at Velo Sport Center (wood track). I should have known better at Natz, since I had also raced at Encino and San Diego that year. Brain freeze under pressure (pun intended).

Quinn8it

I run 160psi at Encino on training wheels and as much as about 180psi on race wheels...
My fastest ever 500m there was a club event where I ran 200psi in my Disc. In the middle of turn 2 on my second lap I bounced and kicked the wheel out. The disc let out a huge thud like a bass drum. It was terrifying and I'm sure cost me time..
Still- dropping PSI does not make you faster- it might make you feel safer, which will likely result in a faster time..

Baby Puke

I thought Colorado Springs was a very smooth track. I ran near 200 PSI there without an issue.

Oldan Slo

Actually it is the radius of the turn that is more influential than the banking angle.

wens

Those two things are intimately related

carleton

Or you can get it wrong like at DLV where the banking is too shallow for the radius. We have 36 degrees with the radius of a 44 deg 250M. It doesn't have neutral handling at high speeds. Our local Georgia Tech PhDs have deduced that, at our track, neutral handling only exists at 32mph. If you exceed that, you drift up track. So, you have to sort of counter steer otherwise you'll shoot over the red line as you come out of turn 4 during a flying 200.

Making a great track is part science and part black magic.

queerpunk

isn't there also an elevation difference between turns 1/2 and turns 3/4 at DLV? one of the straights goes uphill, the other downhill?

carleton

Yeah, one end of the straights are 42 inches higher than the other end. So, you travel down 42 inches as you ride the back straight and you climb 42 inches as you ride the front straight.

Back when I used a power meter at DLV I made this observation:

Track altitude | The Dick Lane Velodrome

Oldan Slo

Tell us how they are related.

carleton

Consider the G-forces involved in traversing a hair-pin turn vs a wide turn at 40mph (in a car or on a bike).

Tight turns on tracks like a 250m can make it feel like you are "slamming into a wall" at high speeds. On tracks like 333M or longer, the turns are so wide you don't get that feeling. It's also easier to maintain a steady pace.

Oldan Slo

I know the answer. I'm just seeing if wens knows the answer.