[BillyK]

Hello,
First time poster, first road bike. I picked up my new road bike this morning at my LBS. The bike is a 2011 Specialized Secteur Elite Compact with SRAM/Apex. The only upgrade I had them perform was to swap out the stock tires for a pair of GP4000's (700x25) At the moment I weigh around 175lbs. The max tire pressure is 120 psi. Based on my weight and the tires, what would you recommend for tire pressure for the back/front? My primary concerns are flats, comfort, and tread life. Based on the little research that I've done, I'm thinking something along the lines of 105/95-110/100. Does this sound reasonable? Could I go even lower? I live in NH so lots of hills, back roads, and the roads aren't in the greatest condition. I took a look at that 15% tire drop graph and that put me at around 110/70. 70 seems kind of low to me, even for the front tire, but what do I know. Anyhow, I welcome all suggestions. I realized it's not an exact science but I'm just trying to find a good starting point that should produce decent results all around. Thanks in advance!

- Bill

 

[Trouble]

25's are good, 28's might be even better.
At 175, start with 85 front and 90 rear. If you ride light in the saddle lower the rear to 85.
While you're out riding, look down at both tires and make sure you have a nice contact patch. No bulging sidewalls. You could even take a big blue chalk stick and mark the tire and ride it too see the wear pattern.
I'm 185, ride 28's at 80-85 front, 90-95 rear.
You get better handling, comfort, tread life and less flats running lower pressure.

 

[Opus51569]

I'm going to respectfully disagree with Trouble's advice. I don't know what kind of road the OP rides, but to minimize the risk of pinch flats in particular, I would suggest inflating your tires closer to the 120psi maximum to start with. If the ride seems particularly harsh afterward, try backing off 5psi at a time. Ideally, you're looking for the highest pressure you can run while keeping the ride of the bike comfortable.

 

[Kerry Irons]

Repsectful disagreement

I'm going to respectfully disagree with Trouble's advice. I don't know what kind of road the OP rides, but to minimize the risk of pinch flats in particular, I would suggest inflating your tires closer to the 120psi maximum to start with. If the ride seems particularly harsh afterward, try backing off 5psi at a time. Ideally, you're looking for the highest pressure you can run while keeping the ride of the bike comfortable.

At 175 lb and 25 mm tires, there's no way the OP needs 120 psi. The result would be loss of traction, faster tire wear, and uncomfortable ride. The OP's original guesses are pretty good. At his weight on 23mm tires, I run at 105 and never get pinch flats. 90-100 psi should be just fine.

 

[cxwrench]

way to high Opus, i'm gonna agree (as usual) w/ Kerry...the OP is right on track, if he pinch flats he can go up 5psi rather than starting off w/ a rock and going down 5psi.

 

[Opus51569]

To clarify, by saying "closer to the 120psi maximum to start with" I didn't mean "the OP needs 120 psi." I agree, the OP will likely find the sweet spot somewhere in that 90-100 range. But, without knowing what kind of roads the OP rides on, it seemed more prudent to start with a higher pressure and work down, then to start too low and work up.

 

[danl1]

To clarify, by saying "closer to the 120psi maximum to start with" I didn't mean "the OP needs 120 psi." I agree, the OP will likely find the sweet spot somewhere in that 90-100 range. But, without knowing what kind of roads the OP rides on, it seemed more prudent to start with a higher pressure and work down, then to start too low and work up.

Interesting difference in point-of-view. To my knowledge and experience, higher pressures increase the chance of puncture, while decreasing the chance of pinch flat.

In my estimation, pinch flat situations are more avoidable than punctures: Puncture hazards tend to be harder to see and avoid.

Not saying right/wrong, just an interesting difference.

FWIW, I'm surprised no one has posted this gem yet:
http://www.bccclub.org/documents/Tireinflation.pdf

There are other versions on the web that do a better job of the graphing and calculation for front/rear bias.

 

[Opus51569]

Actually, I posted a thread a while back with a question about the Berto diagram and Kerry was very helpful. In my situation as a Clyde, the recommended pressure according to the diagram exceeded the maximum rated for the tires I use.

 

[AndrwSwitch]

FWIW, I'm surprised no one has posted this gem yet:
http://www.bccclub.org/documents/Tireinflation.pdf

Looks like I managed to stumble my way to the recommended inflation on my own - 150lb me, heavyish bike for a road bike, and 80 front/95 rear tire pressure. Chart recommends right around 95 for the 23mm tires I use.

I chose my tire pressure for ride feel, after deciding that the 120psi recommended on the sidewall was unnecessarily rough.

Go figure.

 

[joker1656]

I stumbled onto this thread, but wonder the same thing.... or at least similar. Currently my bike has Bontrager tires that have a 100 psi max. I was guessing to reduce rolling resistance etc that I would change to a 120-130 psi tire. My weight is roughly 230. Is that a bad idea?

 

[Ventruck]

I stumbled onto this thread, but wonder the same thing.... or at least similar. Currently my bike has Bontrager tires that have a 100 psi max. I was guessing to reduce rolling resistance etc that I would change to a 120-130 psi tire. My weight is roughly 230. Is that a bad idea?

Your tires may be to handle that pressure, but your rims may not. I actually can't disagree with pumping up to 120psi at your weight (well, maybe 110 would be better). You can't say you're reducing rolling resistance unless you had the tools+computer to prove so.

If anything, I'd nod to getting higher-rated tires and go to 110.

 

[lawrence]

I hate this subject because of too many opinions. But here's my own 2 cents. High tire pressures destroy your wheels and break spokes due to the lack of sidewall flexing of your weight and when you are going over bumps in the road. I'd ride no higher than 100/90, or 95/90 or 90/85, something around there.

 

[BillyK]

Thanks to everyone for all the great advice! My last ride was around 105/95 which seemed pretty comfortable, but I may try 100/90 for the next trip. The roads around here can be pretty rough so I'm a little concerned about pinch flats if I come down too much. As many of you have pointed out, I think the sweet spot will be somewhere between 90-100. Thanks again everyone. This forum rocks!

 

[wiz525]

i've been on Conti GP4000s (700x23) for years and run front and rear at 120 psi... maybe i should try lower??

i have no problem with the ride comfort. given that, is there really any reason to go lower in pressure?

i'm 6'1", 160 lbs....

 

[lawrence]

See my post "Lawrence" on this subject. It's short and to the point.

 

[AndrwSwitch]

i've been on Conti GP4000s (700x23) for years and run front and rear at 120 psi... maybe i should try lower??

i have no problem with the ride comfort. given that, is there really any reason to go lower in pressure?

Because you could be more comfortable. Try lower. If you don't like it, go back. It's not like you're cutting a steerer tube...

 

[Kerry Irons]

Reasons

is there really any reason to go lower in pressure?

Better traction, lower tire wear, more comfort, and possibly lower rolling resistance depending on your road surface roughness.