Optimal Tyre Pressure

[royalpig180]

So I've been debating recently just what tyre pressure I should be using in my road bike. In good conditions, I typically run both front and back tyres at 120 PSI, and leave it a bit lower if it's wet out.

Now that racing season is rolling around, I'm trying to decide if I should change it up (and I think I should). From what I've read, it seems that for a road bike, I definitely want a higher PSI in the back than in the front, and that higher isn't always better. I weigh about 78 kgs and the bike is about another 9 kgs. I found an article here that discusses tyre drop and the ideal pressure based on your tyre width and weight. If I'm calculating it correctly, based on their estimated weight distributions I should run about 85 PSI in the front and 115 in the back. These seem a bit low (especially in the front), but is this more or less accurate? I'll be using Michelin Pro 3 Race's (700x23) come race season.

Thanks in advance for your help!

 

[JayKosta]

Optimum pressure is going to depend on the road surface - rough, smooth, loose, wet, etc.

Too much pressure can give wheel 'bounce' and hurt steering and rear wheel contact.

Jay Kosta
Endwell NY USA

 

[Notso Swift]

Optimal itself is a misnomer. Optimal for what? Comfort, drag, grip (be it traction or lateral)
Then there are different wheels doing different things, the front wheel has quite a bit of force going into it when you get out of the saddle and pull on the bars, for example

Most of these studies show 12-15% drop which sounds like a fine place to start and give it a go at what you have seen. That said, like you I would be likely to add some to the front, as that does sound quite low for a race situation

 

[Fiemme]

I mainly use tubulars (Racing and Training).
Training I generally run about 130 to 150psi.
Racing, depending on road and weather conditions I run up to 200psi.
Good weather Good road surface 200psi.
Bad weather, bad road surface 150psi.
Tyres Conti Sprinter Gatorskins.
If I do ride my only clincher wheels (Campag Zondas) I run about 120psi training. I have never raced on clinchers.

 

[Boeing]

This is an interesting question

It depends is the answer. Velodrome or cobbles?

I ride with guys who believe that MAX PSI is the way to go because they feel it makes them faster.

Hutchinson tyre are one of the few tire companies who argue that less is more in most roadie circumstances. as in higher pressure tire tends to bounce off imperfections causing a force away from the direction of motion etc etc.

I talked to a Hutchinson rep a few years ago and he suggested they believed USt was for real in the Roadie market and wider profile rims would follow, all as a means to support lower pressure tubeless etc.


personally I run about 10 psi lower than stated for comfort on a road bike

but tubeless on a mtn bike I go as low as I can 20-25 with the brew I use

 

[richwagmn]

I run 90psi in my GP4000s on Hed C2 rims. Before I bought those I'd run 105psi on normal width rims.

I'll take comfort over a decrease in rolling resistance any day.

 

[BroDeal]

If you don't care about comfort, only about rolling resistance, then between 120 and 130 in the rear. Subtract 10 or so for the front. Using more will increase rolling resistance somewhat. More importantly, using super high pressures will make your bike handle like ass. Mechanical grip will decrease when cornering. This will be especially true for rough road surfaces.

Personally I think that tires at 120 or so chatter across chip-n-seal, resulting in crappy comfort and crappy handling, so I would use something like 110/100. Adjust up or down a little depending on whether you ride "heavy" or not.

 

[royalpig180]

Maybe I should clarify what I'm looking for. I'm definitely looking for a degree of comfort, as the roads I ride and race on are typically far from pristine. With that said, I am racing, so rolling resistance/speed is also a concern.

 

[STODRR]

75 Kilos for 23s I use 90 rear 80 front. Back down about 5 with 25s

Only time I use more is on really really smooth roads during TTs

 

[Hawkwood]

I'm 84 kgs and am running 25mm tyres. I used to pump front and back up to 120psi, then I found an online pressure calculator and now run 110 back and 90 front. I noticed an immediate improvement in confort, and have a suspicion they run a bit faster.

 

[royalpig180]

I'm 84 kgs and am running 25mm tyres. I used to pump front and back up to 120psi, then I found an online pressure calculator and now run 110 back and 90 front. I noticed an immediate improvement in confort, and have a suspicion they run a bit faster.

Where was this calculator you used? Can you provide a link?

EDIT: I just found this one which claims to be based on the 15% drop method: http://www.dorkypantsr.us/bike-tire-pressure-calculator.html

 

[laziali]

So I've been debating recently just what tyre pressure I should be using in my road bike. In good conditions, I typically run both front and back tyres at 120 PSI, and leave it a bit lower if it's wet out.

Now that racing season is rolling around, I'm trying to decide if I should change it up (and I think I should). From what I've read, it seems that for a road bike, I definitely want a higher PSI in the back than in the front, and that higher isn't always better. I weigh about 78 kgs and the bike is about another 9 kgs. I found an article here that discusses tyre drop and the ideal pressure based on your tyre width and weight. If I'm calculating it correctly, based on their estimated weight distributions I should run about 85 PSI in the front and 115 in the back. These seem a bit low (especially in the front), but is this more or less accurate? I'll be using Michelin Pro 3 Race's (700x23) come race season.

Thanks in advance for your help!

Hi Royal, there are near infinite views on this. Some theoretical hypotheses are that lower pressures roll faster, but real world experience of most racers is that higher pressures are (feel?) faster. Sheldon Brown has a good topic on this as well. But, so many variables. I'll give it a try anyway.

We know:

1. Your riding 700c x23 with good quality, slightly sticky tyres.
2. You are 78kg.
3. You are a racer.

Let's assume:

4. You are using shallow depth alu clincher rims* (you say a 9kg race bike, which suggests mid-level price point).
5. Your frame is carbon, reasonably stiff but not Cervelo-style jangle your teeth out.*
6. You are racing on reasonably smooth roads.#
7. It's dry!+

Based on the above, I suspect you are going to find 110-120psi front and back the best balance between fast and comfortable.

*If you are riding a super stiff frame and/or deep carbon rims, you may find reducing tyre pressure 10 or 20 psi adds greatly to comfort.

#Rougher roads are move comfortable with 10-20psi lower inflation. Conversely, I used to race on wooden tracks on tubs at 160psi. If you are on a really smooth crit circuit, you may want to try adding 10psi to normal.

+ Many people lower tyre pressure by 10-20psi in the wet - whether it's safer is debatable, but it certainly adds to confidence.

Good luck - ultimately, the best advise is to try out different pressures on roads similar to your most common race surface and see what works for you. FWIW, for me, (77kg, Colnago C59, 50mm carbon clinchers, Schwalbe ZX) 120psi front and back seems to "feel" fastest.

 

[Master50]

I used to ride between 110 and 130 in 23s but repeatedly after fixing a flat and using a CO2 cartridge I would get home on 75 to 90 psi. The bike always rolled as easy and definitely felt more comfortable without any sense the tires needed more air.
I too am 78 Kg and now I run 25 on the back at 100 with a 23 in front at 110. I will definitely move to all 25as use up my 23s. 100 rear with 90 front should be the ticket here.

 

[Hawkwood]

Where was this calculator you used? Can you provide a link?

EDIT: I just found this one which claims to be based on the 15% drop method: http://www.dorkypantsr.us/bike-tire-pressure-calculator.html

I think that's the one I used, or if it's not it's based on the same data.

 

[Hawkwood]

*If you are riding a super stiff frame and/or deep carbon rims, you may find reducing tyre pressure 10 or 20 psi adds greatly to comfort.

#

My subjective view is that virtually every frame now is stiffer than the steel ones I was riding in the 1970s and 1980s. I understand that the tyres are the most effective part of the suspension system in terms of dampening vibrations, so with the stiffer frames we have now it might be necessary to compensate with fatter tyres/lower pressures. I certainly feel as if I'm losing fewer fillings having lowered the pressures on my bike!

 

[royalpig180]

Hi Royal, there are near infinite views on this. Some theoretical hypotheses are that lower pressures roll faster, but real world experience of most racers is that higher pressures are (feel?) faster. Sheldon Brown has a good topic on this as well. But, so many variables. I'll give it a try anyway.

We know:

1. Your riding 700c x23 with good quality, slightly sticky tyres.
2. You are 78kg.
3. You are a racer.

Let's assume:

4. You are using shallow depth alu clincher rims* (you say a 9kg race bike, which suggests mid-level price point).
5. Your frame is carbon, reasonably stiff but not Cervelo-style jangle your teeth out.*
6. You are racing on reasonably smooth roads.#
7. It's dry!+

Based on the above, I suspect you are going to find 110-120psi front and back the best balance between fast and comfortable.

*If you are riding a super stiff frame and/or deep carbon rims, you may find reducing tyre pressure 10 or 20 psi adds greatly to comfort.

#Rougher roads are move comfortable with 10-20psi lower inflation. Conversely, I used to race on wooden tracks on tubs at 160psi. If you are on a really smooth crit circuit, you may want to try adding 10psi to normal.

+ Many people lower tyre pressure by 10-20psi in the wet - whether it's safer is debatable, but it certainly adds to confidence.

Good luck - ultimately, the best advise is to try out different pressures on roads similar to your most common race surface and see what works for you. FWIW, for me, (77kg, Colnago C59, 50mm carbon clinchers, Schwalbe ZX) 120psi front and back seems to "feel" fastest.

Thanks for the detailed advice. I'll do some experimenting and this is definitely a good place to start...