# Tire Pressure - is there a rule-of-thumb??



## Tauntonian (Nov 3, 2011)

I have a question. Is there a rule-of-thumb when finding the right(proper) tire pressure.

I bought a Specialized Roubaix in October and have always inflated the tire pressure to the max allowed by the manufacturer. I'm a big guy, 204lbs, 5'11" and thought because I am a big guy I should inflate my tires to the max.allowed.When I bought the bike it had 25mm Specialized Roubaix tires, I changed them to 23mm Mitchlin Pro Race III. I put the maxium amount of pressure allowed in both sets. 

My question is - is there some kind of formula (rider's weight and height/x = proper psi) or do you just adjust your psi by the way the ride feels to the individual rider.

This is probably a stupid question, but I over heard a conversation at the LBS that proper tire pressure is as important as the tire itself? Do you agree?


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## Switchblade906 (Mar 4, 2012)

Im bigger then you at 6'1" 270ish and i inflate my tires to 120-130 psi and it has been fine so far.


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## Chris-X (Aug 4, 2011)

Bigger tires with lower pressures give a smoother ride. The Roubaix allows clearance for 28's. That's what I ride and I'm 175 lbs with an in shape weight of 160.

The very minimal added weight shouldn't affect big strong guys like you in the least. YMMV.


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## JCavilia (Sep 12, 2005)

Do a forum search; this is endlessly discussed, and you'll find much helpful advice. 

At your size, you'd probably be better off with the 25's.

Almost nobody benefits from maximum pressure. If you need that much pressure to prevent pinch flats, you'd do better to get a larger tire.


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## L_Johnny (Jul 15, 2006)

I find that the bigger the tire, talking 25-28, the more I feel the drag as the tire pressure declines. So on my commuting bike, I make a point to re-inflate them every Sunday eve or Monday morning. 110-120 psi on my commuter works great.


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## Chris-X (Aug 4, 2011)

L_Johnny said:


> I find that the bigger the tire, talking 25-28, the more I feel the drag as the tire pressure declines. So on my commuting bike, I make a point to re-inflate them every Sunday eve or Monday morning. 110-120 psi on my commuter works great.


Your mind is playing tricks on you. Really....There's no uh....drag. There just isn't. I ride at 70-80 psi all the time and the ride is just sublime compared to 105-110 on 23's.

Pro's wouldn't be riding cobbles at those pressures if there was drag. Paris-Roubaix is over 150 miles with less than a third of that cobbles and pro's aren't going to sacrifice speed if there was discernable "drag."


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## MerlinAma (Oct 11, 2005)

Google is your friend. 

Michelin Bicycle USA - A better way forward®

Bicycle tire pressure calculator


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## L_Johnny (Jul 15, 2006)

Chris-X said:


> Your mind is playing tricks on you. Really....There's no uh....drag. There just isn't. I ride at 70-80 psi all the time and the ride is just sublime compared to 105-110 on 23's.
> 
> Pro's wouldn't be riding cobbles at those pressures if there was drag. Paris-Roubaix is over 150 miles with less than a third of that cobbles and pro's aren't going to sacrifice speed if there was discernable "drag."


come over and ride my bike, heh! rolling resistance vs air pressure? Where is Kerry Irons when you need him.


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## amandadun (Mar 11, 2012)

Tauntonian said:


> This is probably a stupid question, but I over heard a conversation at the LBS that proper tire pressure is as important as the tire itself? Do you agree?


Yes, but it's easily taken care of. Just keep an eye on your pressure every once in a while. 

_______________________________
Cheers - Amanda


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## Kerry Irons (Feb 25, 2002)

*Road surface*



L_Johnny said:


> come over and ride my bike, heh! rolling resistance vs air pressure? Where is Kerry Irons when you need him.


On very smooth surfaces, higher pressures are better (witness track tires pumped to over 150 psi). On rough roads, lower pressures (to a point) are actually faster because the tire is not bouncing off the rough places and wasting energy. Bicycle Quarterly did a good test on this where they rode on rumble strips at different tire pressures to get the extreme case.

What the best pressure is for a given rider depends on road surface, tire designe and size, rider weight, and rider skill. It's really not possible to say but the general rule of thumb is that 90-100 psi is the best compromise for comfort and speed (and it's hard to be fast when you're not comfortable). If you get pinch flats at those pressures, you need wider tires but of course there is a limit to how wide a tire you can fit on your bike and at that point you may need to pump things up.


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