# Is my tire pressure correct



## bgeurts929 (Jul 24, 2011)

hi there, I am new to road biking. in fact i just got my first road bike yesterday . I road it home and when i look down at the tires where they meet the road, it seems like the look a little deflated. I brought it back to the shop and they told me the pressure was right. Do road bike tires always look like theyre a little deflated or should it look firm where it touches the road. 

Just seems like its a little deflated and i dont know if it should be that way

Any imput?


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## PJ352 (Dec 5, 2007)

bgeurts929 said:


> hi there, I am new to road biking. in fact i just got my first road bike yesterday . I road it home and when i look down at the tires where they meet the road, it seems like the look a little deflated. I brought it back to the shop and they told me the pressure was right. Do road bike tires always look like theyre a little deflated or should it look firm where it touches the road.
> 
> Just seems like its a little deflated and i dont know if it should be that way
> 
> Any imput?


Tire pressure is determined by a number of factors, such as tire construction and size, rider weight, road conditions and riding style.

Here's a guide to give you an idea of what _range_ might be a good starting point. From there, experiment to find what works best for you. Because rider weight is biased ~60/40 (rear/ front, respectively) many cyclists opt for slightly higher pressure at the rear (ex: 100/ 90).

Michelin Bicycle USA - A better way forward®

BTW, if you haven't already done so, invest in a floor pump, saddle bag, spare tubes, a patch kit, mini pump and/ or CO2, and tire levers. Then (if it's offered) sign up for a class at your LBS on repairing flats, or check out Youtube for some instructional vids.


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## JCavilia (Sep 12, 2005)

PJ's right. You need a floor pump with a gauge, and then you figure out what your appropriate pressure is.

Your description of what you saw and expected suggests some confusion. When you say it looks a little deflated, I guess you're describing the tire deflecting visibly under load. Any properly-inflated tire will do that. If it's so firm you can see no deflection it's too hard to ride comfortably.


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## PJ352 (Dec 5, 2007)

JCavilia said:


> PJ's right. You need a floor pump with a gauge...


Well, I'm only 1/2 right, because I forgot the 'with a gauge' part, so thanks for the addition... :thumbsup:


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## Kerry Irons (Feb 25, 2002)

*Sag test*



bgeurts929 said:


> hi there, I am new to road biking. in fact i just got my first road bike yesterday . I road it home and when i look down at the tires where they meet the road, it seems like the look a little deflated. I brought it back to the shop and they told me the pressure was right. Do road bike tires always look like theyre a little deflated or should it look firm where it touches the road.
> 
> Just seems like its a little deflated and i dont know if it should be that way
> 
> Any imput?


The proper pressure is that which allows a 15% "sag" of the tire when the rider is on the bike. IOW, you should see deflection in the tire sidewalls, which may have been interpreted by you as "deflated."


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## biker_on_a_budget (Aug 19, 2011)

Doesn't each tire show max PSI on it? How would you calculate the 15% sag?


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## cxwrench (Nov 9, 2004)

yes, every tire will generally have a _MAX_ pressure on the sidewall. that has nothing to do w/ what pressure you should use in that tire, other than not exceeding the _max_. calculating sag on a road tire is something i've heard about, but i don't know one person, other than maybe Kerry, that does it. it does make sense, because the tires are the suspension on a road bike, and you set up suspension on mountain bikes and motorcycles using sag.


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## biker_on_a_budget (Aug 19, 2011)

Hmm. Well i just got started so I treated my bicycle tires like my vehicle tires. I put them close but just under max. Guess I should have done my research!


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## cxwrench (Nov 9, 2004)

i'd try that search function. there have been dozens and dozens of threads about tire pressure. it's probably one of the most-beat-to-death subjects on this forum.


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## pigpen (Sep 28, 2005)

And don't forget to top them off to the pressure that suits you before every ride.


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## PJ352 (Dec 5, 2007)

biker_on_a_budget said:


> Hmm. Well i just got started so I treated my bicycle tires like my vehicle tires. I put them close but just under max. Guess I should have done my research!


You can reference the Michelin link in my first post for a starting point.


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## NJBiker72 (Jul 9, 2011)

PJ352 said:


> You can reference the Michelin link in my first post for a starting point.


Interesting that link says to fill to the max for those of us over 180.


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## PJ352 (Dec 5, 2007)

NJBiker72 said:


> Interesting that link says to fill to the max for those of us over 180.


Correct, but keep in mind that it's a _guide_, and other factors such as tire construction, style of riding and road conditions also play a role. 

My advice would be to start at max pressure then taper down from there. Odds are, many riders could run at lower pressures, especially up front.


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## Kerry Irons (Feb 25, 2002)

*Max and sag*



biker_on_a_budget said:


> Doesn't each tire show max PSI on it? How would you calculate the 15% sag?


The maximum pressure is just that - the upper limit. Has nothing to do with proper pressure, as many people have pointed out. I don't know about your car tires, but the max pressure on mine is 50% higher than the proper pressure.

You don't calculate sag. You sit on the bike and measure it. I don't do that and I don't know anybody who does, but the tire makers say that 15% sag is the best balance for traction, rolling resistance, tire wear, and rider comfort.


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## NJBiker72 (Jul 9, 2011)

PJ352 said:


> Correct, but keep in mind that it's a _guide_, and other factors such as tire construction, style of riding and road conditions also play a role.
> 
> My advice would be to start at max pressure then taper down from there. Odds are, many riders could run at lower pressures, especially up front.


I agree with that. I personally will go a little lower but not much. Maybe I'll experience a bit more in the future buy I'm comfortable now at the high pressure and the bike feels more responsive. 

Just find it kind of funny how so many blast high pressure yet that is what Michelin suggests.


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## cxwrench (Nov 9, 2004)

NJBiker72 said:


> I agree with that. I personally will go a little lower but not much. Maybe I'll experience a bit more in the future buy I'm comfortable now at the high pressure and the bike feels more responsive.
> 
> Just find it kind of funny how so many blast high pressure yet that is what Michelin suggests.


the max pressure on their chart is 8bar/116psi. for a big guy, that is quite reasonable. what most people around here are blasting are the 145lb guys that inflate tires to nearly their body weight in psi thinking they'll go faster.


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## NJBiker72 (Jul 9, 2011)

cxwrench said:


> the max pressure on their chart is 8bar/116psi. for a big guy, that is quite reasonable. what most people around here are blasting are the 145lb guys that inflate tires to nearly their body weight in psi thinking they'll go faster.


Not true. Lots in here are downright insulting if a 190 lb guy rides 110-120. 

Personally it does feel quicker. 110 is good. Maybe 120 is faster. It's close. 

But really the condescending nature made me think that I should re-think.


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## ColoradoVeloDude (Oct 7, 2005)

Are you a big dude (like me)? Then probably 700x25MM tires inflated to 120PSI is a good place (this is where I ride). Also tires make a big difference and it is good to try different kinds to see what suits you best. I ride on the Continental GP 4000 (black chili) after going through a bunch of tires to see what I liked best. Only downside is price - wipe one of these out on a road hazard and it's serious $$$$ to replace. Anyway, I think good combination of price and performance and durability.

Tires are probably the next most personal thing behind a bicycle saddle. Your mileage and experience may vary. You'll just have to research and try to find the right one. Enjoy the ride, and the search!

Hope it helps

ColoradoVeloDude
Colorado Springs, Colorado


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## Peanya (Jun 12, 2008)

I can't stand that Michelin guide. If I followed that, I'd be running at max psi (I'm about 190lbs). I run 90~100psi max in the rear, and 80~90 up front. Also, if I ran that, I'd have a LOT of puncture flats. Then again, that guide was made by a company selling tires...
My advice on pressure is the same for everyone: find out what works for you. If you go too low, you get pinch flats. If you go too high, you get a lot of puncture flats.


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## PJ352 (Dec 5, 2007)

Peanya said:


> *I can't stand that Michelin guide. If I followed that, I'd be running at max psi (I'm about 190lbs).* I run 90~100psi max in the rear, and 80~90 up front. Also, if I ran that, I'd have a LOT of puncture flats. Then again, that guide was made by a company selling tires...
> My advice on pressure is the same for everyone: find out what works for you. If you go too low, you get pinch flats. If you go too high, you get a lot of puncture flats.


Based on the bolded statement above I'm thinking you either didn't understand or chose to ignore the text in the guide that states... _"Obviously, your style of riding can have an effect too, but the chart below should give you a reasonable *guide of where to start when experimenting* to find the proper tire pressure for you"_...


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## willieboy (Nov 27, 2010)

For what it's worth. I'm running GP4000's (which is my third brand) and like them very much. I played around with preasures quite a bit and settled on 120psi rear and 110psi front. 700 X 23, 160lbs rider.


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## Peter_leo (Aug 26, 2011)

Check the pressure on the side wall of the tyre then take the upper limit if you are after a hard fast ride.


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## Kerry Irons (Feb 25, 2002)

*Wrong answer*



Peter_leo said:


> Check the pressure on the side wall of the tyre then take the upper limit if you are after a hard fast ride.


Did you not read the rest of this thread, or did you choose to completely ignore it? It is a rare case indeed where the max pressure on the tire sidewall is the best choice. High pressures means fast tire wear, poor traction, discomfort, and possibly higher rolling resistance if the road surface is anything but smooth.


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## smokey422 (Feb 22, 2004)

The late Sheldon Brown used to recommend running 10% less pressure in the front tire than in the rear. This has always worked well for me. I usually end up running max pressure in the rear on my 700X35s (90psi) because I am a 250# Clydesdale.


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