hobkirk

Dozens of flats in my first months of cycling taught me to keep my tires at 115/125 PSI. I upgraded my tires to Conti GP4000 (25mm wide) and stopped having flats. As I stopped having flats, I have lowered my PSI slightly to 110/115 but all those flats last year make me leery of experimenting.

Comfort is nice - I ride a lot of miles and my buying a carbon Specialized Roubaix reveals my preferences. Lower pressure gives a smoother ride.

You guys know it all,* so I will ask you!

• How low can PSI reasonably go for 25mm GP4000 tires?
• Or should I stop being a wuss and just experiment until I start getting flats?
• My roads are typical New England. I.e., snow and freezing as low as 5F in the winter) - mostly smooth but there are some unavoidable rough patches on every ride, some of which are taken fast (25).
  

Curious about all the flats? Read on...

Until I got the Conti GP4000 tires, my first 3-4 months of cycling were ridden on the Vittoria tires that came on my GT bike. I had LOTS of flats - including multiple flats on several rides (my Topeak Turbo pump got a lot of work). My tire pressure was 115-125 PSI, I used lots of different tubes - no difference by brand observed, and patched tubes (up to 5) seemed to work fine. There was no pattern to where the punctures occurred (the patches were spread all over the tubes).

[I was a fat, poor novice - I didn't expect different tires would make that big a difference, and $50 tires were daunting. I finally wore out the rear tire and was forced to buy tires. What a difference!]

* I am actually sincere about "you know it all" - the pool of experience here is remarkable.

10 Wheels

I don't believe PSI has anything related to flats.
Just use enought PSI to prevent snake bite flats.

Roy has 16,000 miles on this 700 X 32 tire, 60 PSI No Flats on his front wheel.

Garfield Cat

I hope you really didn't spend $50.00 for a tire.

LesterOfPuppets

I can run 25mm tires down to about 75 fairly safely, still gotta watch and unweight over the really rough stuff. I weigh 150.

They're pretty sluggish at that psi, though.

waltersc

Conti GP4000 are great tires, however they are designed with performance in mind. I love GP4000s and use them on my road bike, but not for comfort reasons. Lower air pressure will not reduce the flat protection, but could cause pinch flats. At 230# I would be a little concerned about running a real low pressure even in 700x25's. Are the Conti's providing the comfort you are looking for at 110PSI? If not maybe a drop of 10psi might. Just keep those extra tubes on hand.

Stickney

I ride Conti Gatorskins at around 100 psi and I am 250 lbs. I ride on everything from gravel to cheap seal to rough asphalt and concrete. I've come to that PSI based on trial and error.

Sheldon Brown has some info and a PSI table, though I feel like I have seen other variations on weight/PSI elsewhere:

https://sheldonbrown.com/tires.html#pressure

datlas 

There are all sorts of formulas (formulae?) and charts out there.

They are a good starting point but not to be taken as gospel.

If I had your weight, tires, and riding conditions I would drop the PSI to about 100 in front and 105 in back. I suspect that will give you good comfort, reasonable wear, good performance, and adequate pinch flat protection.

PS these are great tires and if you watch for sales/coupons (especially from PBK) can often be bought for 30-35 bucks each. Whenever they go on sale I buy a half-dozen which keeps me in tires for a long time.