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Optimal tubeless 28mm tire pressure?

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Optimal tubeless 28mm tire pressure?

Old 07-26-21, 11:33 AM
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LuMax
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Optimal tubeless 28mm tire pressure?

I ride on Zipp 303 NSW tubeless disc rims with Schwalbe Pro 1 TLE 28mm tubeless tires, Stan's Race sealant.
My bicycle weighs in at ~15 pounds, and I weigh 155.
I run 70psi in the front tire and 75psi in the rear, and I am curious if you consider this optimal, or could my ride and/or rolling resistance be improved with different pressures?
Curious what pressure you use and how you like it?
Thanks.
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Old 07-26-21, 11:43 AM
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Originally Posted by LuMax View Post
I ride on Zipp 303 NSW tubeless disc rims with Schwalbe Pro 1 TLE 28mm tubeless tires, Stan's Race sealant.
My bicycle weighs in at ~15 pounds, and I weigh 155.
I run 70psi in the front tire and 75psi in the rear, and I am curious if you consider this optimal, or could my ride and/or rolling resistance be improved with different pressures?
Curious what pressure you use and how you like it?
Thanks.
That sounds reasonable, but it's a surface-dependent issue. I'd probably go lower if there was lots of rough chipseal, for instance.
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Old 07-26-21, 12:17 PM
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I go anywhere from 65 to 80 psi depending what I plan to ride on. I weigh more than you.
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Old 07-26-21, 12:27 PM
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Thanks HTupolev and Seattle Forrest.
The roads here are always mixed.
A typical ride will feature anything from new, silky-smooth asphalt to choppy, cracked, potholed, old pavement with lots of cracks. Minimal gravel, some chip seal.
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Old 07-26-21, 12:31 PM
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You are probably in the ballpark. Maybe a smidge lower if wet and/or rougher pavement, a smidge higher if riding smooth dry roads.
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Old 07-26-21, 12:50 PM
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I'd run 50-55 front and 70-75 rear, assuming 60/40 weight balance.

I'd run 55-60 front and 67-72 rear, assuming 55/45 weight balance.
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Old 07-26-21, 01:34 PM
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I use this as a gauge and then adjust as needed... I don't ride zip wheels, but its always been a good first start....

https://axs.sram.com/guides/tire/pressure
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Old 07-26-21, 02:09 PM
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Try a dozen or so rides at one PSI. Then ride another dozen or so rides at another PSI. Then ride another dozen rides at some other PSI. Which felt better to you and left your legs feeling like they had more energy to ride more? Which does your data say that you did better times on?

That's your personalized optimum PSI for that road surface and tire. If you happen to get pinch flats, then your PSI is way too low for that riding surface regardless of how good it felt.
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Old 07-26-21, 05:57 PM
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I think you could probably go a bit lower at your weight. But I donít think you are far off the mark. Some people run much lower front pressure in line with weight distribution, but I donít personally like the way that feels when climbing steep hills. So I normally keep my front pressure just 5 psi less than the rear. Iím currently running 70/75 psi on 30c tubeless race tyres. But Iím a fair bit heavier than you at 175 lbs.
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Old 07-26-21, 05:58 PM
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Originally Posted by Iride01 View Post
Try a dozen or so rides at one PSI. Then ride another dozen or so rides at another PSI. Then ride another dozen rides at some other PSI. Which felt better to you and left your legs feeling like they had more energy to ride more? Which does your data say that you did better times on?

That's your personalized optimum PSI for that road surface and tire. If you happen to get pinch flats, then your PSI is way too low for that riding surface regardless of how good it felt.
Pinch flats wonít be an issue with tubeless.
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Old 07-26-21, 08:11 PM
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https://info.silca.cc/silca-professi...ure-calculator
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Old 07-27-21, 05:25 AM
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Originally Posted by yarbrough462 View Post
That, everything else above is a (educated) guess, LuMax .
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Old 07-27-21, 05:36 AM
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Originally Posted by Badger6 View Post
That, everything else above is a (educated) guess, LuMax .
The SRAM/Zipp calculator linked to earlier in the thread is the best I've seen - and free. It's the only one that covers pretty much every parameter.
But even these calculators are educated guesses and not meant to be absolute. What they provide is a good starting point. You also need a good tyre pressure gauge to make any use of them!
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Old 07-27-21, 05:48 AM
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The Silca calc is free (I never put my real email in). I've used the SRAM one, I cannot remember why I switched to using the Silca one...I think it was because Silva works off of measured width, rather than what the sidewall says. Either way, a calculator is key. And, as such, a calculation (if it is indeed calculating) is not a guess, but the returned result is definitely a starting point.
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Old 07-27-21, 05:54 AM
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28mm nominal but 30.3 mm actual on my set.

Also depends on your roads and weight distribution. Frank Berto's chart is a good lower end pressure setting and they work on my roads
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Old 07-27-21, 06:00 AM
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Originally Posted by Badger6 View Post
The Silca calc is free (I never put my real email in). I've used the SRAM one, I cannot remember why I switched to using the Silca one...I think it was because Silva works off of measured width, rather than what the sidewall says. Either way, a calculator is key. And, as such, a calculation (if it is indeed calculating) is not a guess, but the returned result is definitely a starting point.
I agree. Just have to bear in mind that the calculation is an estimate based on various parameters and assumptions. For example they have to make assumptions about your tyre compound and construction. It's worth checking your tyre manufacturer's pressure guide too, as the better ones have detailed recommendations for their specific tyre variants.
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Old 07-27-21, 06:01 AM
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Make sure your pressure gage is accurate, many are wildly off. I have one that is over 10 psi wrong
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Old 07-27-21, 09:32 AM
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Originally Posted by PeteHski View Post
Originally Posted by Iride01 View Post
Try a dozen or so rides at one PSI. Then ride another dozen or so rides at another PSI. Then ride another dozen rides at some other PSI. Which felt better to you and left your legs feeling like they had more energy to ride more? Which does your data say that you did better times on?

That's your personalized optimum PSI for that road surface and tire. If you happen to get pinch flats, then your PSI is way too low for that riding surface regardless of how good it felt.
Pinch flats won’t be an issue with tubeless.
Yeah, I actually think I came back in a added that after I got off my soap box. My bad!

So lets just change that to something like if your tire beads or rims are getting torn up or the tire burps air when on twisty paths or roads, then you might have too low a tire pressure.

Will that work? I imagine eventually if I ride long enough I might be tubeless, so I'd like to have that stuff figured out when I get there.
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Old 07-27-21, 10:07 AM
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Originally Posted by Badger6 View Post
Either way, a calculator is key.
No it's not. Keping track of what you're using and then adjusting to suit from there is key. A calculator is just a calculator.

Originally Posted by Badger6 View Post
And, as such, a calculation (if it is indeed calculating) is not a guess
If you're trying to say that the actual process of doing math is not guessing...at some theoretical level I would entirely disagree with you. Algebraic calculations are done using formulas that others.... wait for it... guessed at as a good approximation of what they believed they observed as ideal using their own preset biases of what they think should happen. Having made pressure calculation formulas that I have also posted on this forum well over a decade ago I can tell you that all the formulas are guesses at some level. It is after all a guess of what we "think" will "work well" for you.

Originally Posted by Badger6 View Post
but the returned result is definitely a starting point.
As are all pressure recommendations: a starting point. We don't all ride on the same saddle because...well...we are all different. tire pressure is the same. Considering how much real world pressures will vary with respect to a recommended starting pressure (not uncommon to see it vary by 15%-40% in many cases) it really does point out that even though they have nice web pages and claim to have a lot of time and "research" (which btw is simply a bunch of bike nerds comparing things with their friends at work after doing field "testing") they are actually just... guesses. Guesses made through the filter of a lot of experience and feedback but guesses nonetheless.

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Old 07-27-21, 10:32 AM
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For you Psimet2001 and many others, like me, who have a lot of experience (meaning lots of saddle time)...I completely agree with you.

But, when someone rolls in here and says I weigh X (no mention the bike) and I'm riding on tires xx mm wide (no mention of tire). I always point them to a calculator for a starting point because any other advice off of the incomplete data they provided is a WAG. No idea if they're riding board stiff Schwalbe Marathons or Gatorskins or a nice supple Vittoria. No idea they're riding a 8kg gravel rocket ship or a 22kg tourer loaded out for a four week epic in the Alps. No way to give even a good stating point, maybe some opinions, sure.

At least with a caclulator the guess the user gets is somewhat scientific, and therefore more SWAG, and in reality is a much better starting point. Mea Culpa if I let it be thought that if a calculator says run the pressure at Y thats what it should be. FTR, Silca tells me to put my gravel tires around 42psi...I've never run them higher than 36, except on the first ride fro about 5 minutes. It was a good starting point...so there's that.
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Old 07-27-21, 10:32 AM
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Originally Posted by Psimet2001 View Post
No it's not. Keping track of what you're using and then adjusting to suit from there is key. A calculator is just a calculator.


If you're trying to say that the actual process of doing math is not guessing...at some theoretical level I would entirely disagree with you. Algebraic calculations are done using formulas that others.... wait for it... guessed at as a good approximation of what they believed they observed as ideal using their own preset biases of what they think should happen. Having made pressure calculation formulas that I have also posted on this forum well over a decade ago I can tell you that all the formulas are guesses at some level. It is after all a guess of what we "think" will "work well" for you.


As are all pressure recommendations: a starting point. We don't all ride on the same saddle because...well...we are all different. tire pressure is the same. Considering how much real world pressures will vary with respect to a recommended starting pressure (not uncommon to see it vary by 15%-40% in many cases) it really does point out that even though they have nice web pages and claim to have a lot of time and "research" (which btw is simply a bunch of bike nerds comparing things with their friends at work after doing field "testing") they are actually just... guesses. Guesses made through the filter of a lot of experience and feedback but guesses nonetheless.

You have to start from somewhere and the online calculators are a good place to make that start from. But it is important to realise they are not set in stone and in fairness most of them even state this e.g. on the sram calculator "⚠ Disclaimer - This pressure guide is a starting point recommendation and further refinements are encouraged to find the right pressure for any given setup."
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Old 07-27-21, 10:40 AM
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Originally Posted by Badger6 View Post
But, when someone rolls in here and says I weigh X (no mention the bike) and I'm riding on tires xx mm wide (no mention of tire). I always point them to a calculator for a starting point because any other advice off of the incomplete data they provided is a WAG.
Let me also be clear...the OP did not do that.
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Old 07-27-21, 11:06 AM
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FWIW, I believe that that at least for the Silca calculator, the returned values are based on a lot of actual 'real world' testing. Sure, every possible iteration of weight, road surface, tire width, etc wasn't tested, so likely a good chunk of values interpolated. But, to imply that all of it is just theoretical guessing is a bit extreme IMO.
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Old 07-27-21, 12:05 PM
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Originally Posted by Badger6 View Post
FTR, Silca tells me to put my gravel tires around 42psi...I've never run them higher than 36, except on the first ride fro about 5 minutes. It was a good starting point...so there's that.
I do like the Silca one if you're going to use one... but to help illustrate what we are talking about - even your seemingly small adjustment from 42 to 36 is over a 15% change from their recommendation. I posit that at that point anyone with some experience can simply guess a pressure and get someone within the same range of 15%-20%. In other words I fear we have put these calculators on too high of a pedestal. Absolutely a great starting point ... but as valuable as any experienced rider's guess.
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Old 07-27-21, 12:38 PM
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To arrive at the number that was ~15% lower, I had to ride it after getting the "recommended" pressure. Moreover, despite hundreds of thousands of kms all over the world on all sorts of bikes, and all sorts of tires (type, brand, size), my initial guess was even higher than Silca. I am putting the calculators on the pedestal they belong: find the best starting point for air pressure. I also prefer it because it's simpler. The SRAM calculator asks for a lot more info, which gives an impression of granular precision which it cannot deliver, exactly to your point, Psimet2001 .
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