Hello!

Just wondering what tire width and pressure I should go with for lowest rolling resistance? I was using 20's but replaced them with 23's because I read wider tires are faster. But how much is too wide? Should I go up to 25's? Zipp says their rims are designed for optimum aero performance for 23. Any wider and negative aerodynamics start to dominate. I don't use Zipp's. Anyone have a guess on what tire width is best for Reynolds 32's?

After choosing a width...what pressure should I run them at? I'm 135 lbs right now. I was running 100psi front and rear. Should I ride lower?

Thanks!

Generally 25s have less rolling resistance than 23s. But it varies by manufacturer and how they design and build the casing. So the same. General rule doesn't apply across the board. Also there's the aero benefit of narrower tires to consider. If I were you I ould stick at 23s and 100 lbs

As light as you are, you could go lower. I weigh about 180 and I'm running 100/110 (f/r) in my 23's. I once saw a thread on here (sticky maybe?) about what tire pressures to start out at without the worry of pinch flats. I can't find the thread, but I took a pic of the formula with my phone.
Edit:I tried to paste the pic of the formula, but it looks like its not gonna take. Anyway the formula for a 23mm rear tire is...

(rider weight in lbs x .33) + 53.33= rear tire psi

To find the psi for the front tire, simply multiply rear tire psi x .9

Example (135lbs x .33) + 53.33=97.88psi (rear tire)
97.88psi x .9=88.09psi (front tire)

Again, these are merely starting points. Hope this helps.

Thanks!

Does it matter whether you run clinchers or tubulars? Same formula?

Good question. I really have no idea.

I weigh anywhere between 130 and 140. My preference is a 25 in the back and 23 in the front, I have done this with many kinds of tires. although there is great debate on this subject, I believe it is beneficial setup. I keep the back at about 95~ and the front at 90~. If I know I will be riding on very smooth roads I will pump them up 10-20 more psi. But generally I dont break 100. Any higher and the pain starts kicking in.

135 pounds is pretty light, so you can probably do anything you want. Personally, though, I like larger tires--at least 28--at lower pressures, down into the 70s with 35mm tires. It's not any slower in the riding I do (I'm not saying it isn't slower, just that it doesn't make a measurable difference in my commute). And it's WAY more comfortable and stable.

Bicycle Quarterly did wind tunnel tests with rider on bike and at speeds 22 mph and below there was no measurable difference in aerodynamic drag between narrow and wide tires. If most of your riding is done at speeds below 22 mph than go with tires with the lowest rolling resistance regardless of width.

Tire pressure chart

Handy calculator based on the above chart

Agree...based on your light weight you should stick with what you are doing. You could probably drop it to 95PSI in front and keep 100PSI in back. The folks who should go to 25 are heavier and/or ride on really crappy roads.

p.s. extra BF credit if you are running GP4000s tires.

Actually it's not that simple. Those wind tunnel test measured with wind straight ahead. When it comes at an angle, the differences are greater. But more importantly wider tires impact aero wheels. That's why Zipp recomends, per the post above don't use more than 23 with their wheels

I'm not saying this might help, but this might help. I was a bit surprised because I always pump my tires to max psi, but decided to give the chart's suggestions a go. Granted, I'm 140-ish pounds, but I found 90-100 to be quite workable.