Road bike tyre pressures

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Road bike tyre pressures

Postby Caelum » Tue Feb 19, 2008 1:16 pm

Yes, this should be a FAQ, amongst many other FAQs really.. But there isn't one(that i know of)... and do you KNOW how many results you get for searching tyre pressure on a bike forum? :P

So what's the general rule of thumb?


I'm currently running 100psi in my Maxxis Detonator 28c's. They sing along quite nicely on the road now, and surprisingly it isn't that much more of a harder ride than how they were pumped up a few days ago(before i got a floor pump) at about 30psi...

But when it comes down to it? What's the max pressure i should look at using in them? How about other tyres that i'll end up using? gp4000's, gatorskins etc etc etc... How do various sized tyres change what pressure you should use? do they change?

What are generally the max/min and suggested pressures?


Cheers :)
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by BNA » Tue Feb 19, 2008 1:44 pm

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Postby mikesbytes » Tue Feb 19, 2008 1:44 pm

Depends on what size tyre, how much you weigh and personal preference. Brand/Model of tyre (ignoring tubeless and singles) makes little difference in deciding on tyre pressure.
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Postby Caelum » Tue Feb 19, 2008 2:01 pm

mikesbytes wrote:Depends on what size tyre, how much you weigh and personal preference. Brand/Model of tyre (ignoring tubeless and singles) makes little difference in deciding on tyre pressure.



Well discounting the above that we can discount... I weigh in at about 85kg, and am running 700x28c's at the moment...
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Postby rustychisel » Tue Feb 19, 2008 2:03 pm

Depends what's said on the side of the tyre. :wink:

which is usually a rated maximum, with an error factor of at least 20%. I wouldn't have thought Maxxis Detonator tyres were rated very high, and in any case most Mavic rims (for example) are limited to what they call a 'safe infaltion pressure' which is about 120psi. The average person (??) wouldn't need to exceed that, IMO
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Postby mikesbytes » Tue Feb 19, 2008 2:49 pm

The rating on the side of the tyre is based on whether the marketing department or the legal department won.

Caelum, I weigh 83kg and pump them up to 110 front, 120 rear on 23's or 25's. If I was running 28's I'd probably drop the pressure by 10 each end. I pump my tyres up once a week, unless I think its going to rain and then I don't pump them up or pump them up to 100 front and 110 rear.

Feel can be deceptive as the harder tyres feels like its giving you lower rolling resistance but what happens is that it bounces over rather than rolling around the micro bumps on the road.
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Postby sogood » Tue Feb 19, 2008 2:53 pm

mikesbytes wrote:Feel can be deceptive as the harder tyres feels like its giving you lower rolling resistance but what happens is that it bounces over rather than rolling around the micro bumps on the road.

... And slower. Macro bumps. ;)
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Postby Caelum » Tue Feb 19, 2008 3:12 pm

Well yeah, as i said i'm running 100psi(90 in the front) at the moment... so i guess that's a reasonable figure based off what mike has just said(thanks).

See how it goes for a while i guess..
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Postby Kalgrm » Tue Feb 19, 2008 4:37 pm

I know you have little prospect of needing this advice, but it has been said that you should drop those pressures by 10psi or so when the roads are wet. That gives you a bigger contact patch for better traction.

Should I remind you again next year when the roads get wet again? ;)

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Postby 531db » Tue Feb 19, 2008 7:22 pm

You'll find a maximum recommended inflation pressure of 120 psi marked on the sidewalls of your 28C Maxxis Detonators.
I tend to use 110-120 psi on the front, 120-130 psi on the rear with these tyres on quality (Wolber/Mavic/Velocity) rims.
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Postby Mulger bill » Tue Feb 19, 2008 11:15 pm

I run 110/100 on my Zaffiro 25s with 83ish kg.

Will pumping harder improve cornering grip?

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Re: Road bike tyre pressures

Postby europa » Tue Feb 19, 2008 11:48 pm

Caelum wrote:Yes, this should be a FAQ, amongst many other FAQs really.. But there isn't one(that i know of)... and do you KNOW how many results you get for searching tyre pressure on a bike forum? :P

So what's the general rule of thumb?


I'm currently running 100psi in my Maxxis Detonator 28c's. They sing along quite nicely on the road now, and surprisingly it isn't that much more of a harder ride than how they were pumped up a few days ago(before i got a floor pump) at about 30psi...

But when it comes down to it? What's the max pressure i should look at using in them? How about other tyres that i'll end up using? gp4000's, gatorskins etc etc etc... How do various sized tyres change what pressure you should use? do they change?

What are generally the max/min and suggested pressures?


Cheers :)


Caelem, Sheldon Brown has some suggested tyre pressures, but they are only suggestions.

Basically, what's written on the side of your tyre can be treated as a useful maximum - you know it's safe because at that pressure, the company lawyers start having kittens. The trick then is to work out what suits you.

Typically, with these upright horrors that most of you ride, your bum is right over the rear wheel banging most of your body weight onto the rear tyre. This is why Sheldon suggests something like 10% less pressure in the front tyre than the rear. On a sensible bike like a bent, where the weight distribution is more even, you may choose to run equal pressures.

However, the pressures you choose to use depend on your bike, how much you weigh, how you use it and the tyres in question.

It's not so hard to work out. Simply start up near the max and work your way down. Most tyres lose pressure over time so by being sensitive to the way your bike works and feels, you can gain a feel for what sort of pressures you need to be running. You are sensitive to what your bike is telling you aren't you? Listen to her, she's the expert, not some loud mouth on a forum.

I too ride on 28mm Detonators and find that 100 front and 110 rear works very well for me on the goat tracks I ride. They are compliant at that pressure and grip the road well. I'm a tad over 100kg so if you're lighter, you may wish to run them lower. The max pressure of 120 makes for a very solid ride which my aging body does not relish.

That said, on the bent which runs 1" Detonators (on 26" rims), I've found that 100 front and rear works well, because the weight distribution is even.

Forget what 'Expensive Bits Magazine' tells you and ignore what the fairy on the hyper bike likes to claim on a forum somewhere in cyberspace. This is about YOU and YOUR bike.

Start with the max pressure shown on the tyre and work down. The tyre will probably be overly hard and lacking in grip at the max pressure (but not always - read toolong's reports). As the pressure lessens, at some point, the tyre will start to perform really well under the provocation you provide - a more sporting rider will demand higher pressures than a plodder, and it's here that a comparison between toolong's tyre pressures and my own starts to bear fruit :oops: After that, you'll discover that the grip gives way to softness. Pump the tyres up a bit and you'll discover the pressure that works for YOU - everyone else's numbers are meaningless in your world, even if those numbers work in theirs.

Experiment and be sensitive to what that lovely cycle is telling you, that's all you need.

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Postby mikesbytes » Wed Feb 20, 2008 10:56 am

Mulger bill wrote:I run 110/100 on my Zaffiro 25s with 83ish kg.

Will pumping harder improve cornering grip?

Shaun


Only if they were under inflated and are deforming excessively on the corners.
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