Optimal tubeless 28mm tire pressure?
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Unless my gauges are wrong, I ride 125 psi rear and 100 psi front on the MUP here. I don't get my bones shaken. However lately I've been on the roads which have a few segments of rougher road. So I've dropped the pressure in the rear to 110 psi. 25mm GP5000's, tubed version.
I'm both faster and less tired at those pressures than when I've tried 90 psi. But your roads aren't my roads. So I'm not going to say what you should run. But if you just let a calculator tell you what to put in them, you are doing yourself a disservice, IMO.
I'm both faster and less tired at those pressures than when I've tried 90 psi. But your roads aren't my roads. So I'm not going to say what you should run. But if you just let a calculator tell you what to put in them, you are doing yourself a disservice, IMO.
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For me at least both those calculators recommend very similar pressures. Silca 69/71 Sram 67/71
I don't fuss over a couple of psi here or there. I don't find it that sensitive.
The only big variation I see between the various calculators are those that recommend significantly lower front pressure based on the 15% drop rule e.g. I've got one that recommends 52/79 with a 60% rear weight distribution.
I don't fuss over a couple of psi here or there. I don't find it that sensitive.
The only big variation I see between the various calculators are those that recommend significantly lower front pressure based on the 15% drop rule e.g. I've got one that recommends 52/79 with a 60% rear weight distribution.
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You can simply just take the Zipp calculator and see larger differences than you're showing by simply toggling between tubed, tubeless and hookless tubeless selections.
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I see what you mean. I guess the Silca calculator doesn't attempt to account for all those parameters and just by coincidence it spits out much the same recommendations for my specific combination of those parameters. I'm surprised that the Silca calculator doesn't make any differentiation between tubed and tubeless tyres.
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I see what you mean. I guess the Silca calculator doesn't attempt to account for all those parameters and just by coincidence it spits out much the same recommendations for my specific combination of those parameters. I'm surprised that the Silca calculator doesn't make any differentiation between tubed and tubeless tyres.
We know that a tubed tire setup can be run a max pressure higher than Tubeless hooked, which in turn can be maxed at higher value than hookless Tubeless. On the flip side, the tubed setups can't be run at as low of pressures as the TL options without more severe risks of pinch flatting. Perhaps the returned values for Zipp's calculator is to match the marketing if they want to rate a rim as ok for certain max rider weight and the likely tire width that rim is optimized for? On the flip side, Silca seems to disregard any tire, rim or weight ratings, and effectively is telling consumers to figure that part out for themselves.
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I guess it's just my theory, but can't say I've seen anything contradictory yet, but Silca spits out what they deem 'optimal' (for lack of a better term). Ie. what yields fastest speed for the given parameters for a given power input. That is, what data is out there that, providing an average weight rider would be within safe operating levels regardless, that a tubeless tire should be run at a lower PSI than a tubed tire to yield max speed for provided power?
We know that a tubed tire setup can be run a max pressure higher than Tubeless hooked, which in turn can be maxed at higher value than hookless Tubeless. On the flip side, the tubed setups can't be run at as low of pressures as the TL options without more severe risks of pinch flatting. Perhaps the returned values for Zipp's calculator is to match the marketing if they want to rate a rim as ok for certain max rider weight and the likely tire width that rim is optimized for? On the flip side, Silca seems to disregard any tire, rim or weight ratings, and effectively is telling consumers to figure that part out for themselves.
We know that a tubed tire setup can be run a max pressure higher than Tubeless hooked, which in turn can be maxed at higher value than hookless Tubeless. On the flip side, the tubed setups can't be run at as low of pressures as the TL options without more severe risks of pinch flatting. Perhaps the returned values for Zipp's calculator is to match the marketing if they want to rate a rim as ok for certain max rider weight and the likely tire width that rim is optimized for? On the flip side, Silca seems to disregard any tire, rim or weight ratings, and effectively is telling consumers to figure that part out for themselves.
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My use of higher pressures in my tires isn't some stuck mindset as those that only do what formulas and calculators tell them to do. I have on many occasions tried out different pressures. And not just when changing my tire size, but also when changing models or brands that are the same size.
Typically I'll ride six to twelve rides at the same pressure. Then adjust it up or down and ride the same number of rides at that new pressure and then rinse and repeat till I find the PSI I like.
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The only disservice will be if I continued to maintain that PSI for every ride and never tried other pressures to see if I both felt something better in my legs or the handling, and compared that to my metrics collected for those rides.
My use of higher pressures in my tires isn't some stuck mindset as those that only do what formulas and calculators tell them to do. I have on many occasions tried out different pressures. And not just when changing my tire size, but also when changing models or brands that are the same size.
Typically I'll ride six to twelve rides at the same pressure. Then adjust it up or down and ride the same number of rides at that new pressure and then rinse and repeat till I find the PSI I like.
My use of higher pressures in my tires isn't some stuck mindset as those that only do what formulas and calculators tell them to do. I have on many occasions tried out different pressures. And not just when changing my tire size, but also when changing models or brands that are the same size.
Typically I'll ride six to twelve rides at the same pressure. Then adjust it up or down and ride the same number of rides at that new pressure and then rinse and repeat till I find the PSI I like.
Out of interest what pressure would you have started at with 28 mm tubeless?
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Originally Posted by PeteHski View Post
Well if you banged those pressures straight into a 28 mm tubeless setup you would definitely be doing yourself a disservice!
Well if you banged those pressures straight into a 28 mm tubeless setup you would definitely be doing yourself a disservice!
Tubed or tubeless, my procedure for finding out what PSI to run them at on the road conditions around me will be the same.
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That's what to me your assumption was about people that .....
I probably won't know till I get 28 mm tires. I wouldn't expect to run the same pressure as my current tires once I did my trials with them. So as long as I'm within the range suggested by the mfr, what does it matter what PSI I start out with?
Tubed or tubeless, my procedure for finding out what PSI to run them at on the road conditions around me will be the same.
I probably won't know till I get 28 mm tires. I wouldn't expect to run the same pressure as my current tires once I did my trials with them. So as long as I'm within the range suggested by the mfr, what does it matter what PSI I start out with?
Tubed or tubeless, my procedure for finding out what PSI to run them at on the road conditions around me will be the same.
These calculators would give you a very good idea how much to reduce from your preferred pressure on narrower tyres. They provide a good relative tool in that way.
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Well, stuff happens.
In a gravel race last month, I was descending, in a forest with dappled sunlight, with my sunglasses' lenses smeared up with sweat and road grime...I thought, "I hope there's not a big pothole or tree root on this trail, 'cause I would not be able to see it." The next moment, BAM! Right through a nasty pothole. The wheels were fine, but the rear tire burped out enough air that I had to stop to pump it up.
At least it was towards the end of the race; three riders passed me as I was pumping up the tire, though I later caught one of them. Yeah, I was really bummed - I ended up in 21st place instead of 19th. It was tragic!
In a gravel race last month, I was descending, in a forest with dappled sunlight, with my sunglasses' lenses smeared up with sweat and road grime...I thought, "I hope there's not a big pothole or tree root on this trail, 'cause I would not be able to see it." The next moment, BAM! Right through a nasty pothole. The wheels were fine, but the rear tire burped out enough air that I had to stop to pump it up.
At least it was towards the end of the race; three riders passed me as I was pumping up the tire, though I later caught one of them. Yeah, I was really bummed - I ended up in 21st place instead of 19th. It was tragic!
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I was JUST coming in here to drop that one. a couple psi is also a huge difference in these lower pressures as well.
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25mm tubed GP4000 that measure a touch over 27 on 19mm (internal) rims. I have been playing with pressures. My roads are usually quite good with a few expansion cracks in sections. I am 175 lbs and have ranged from 70-90 rear and 65-80 front. Recently, it feels like ~70F/80R feels the best and can be slightly faster (per my Strava stats/PRs) than higher pressures on the downhill corners and downhill fast sections too. I definitely feel more confident downhill at slightly lower pressures but have not gone as low as many do. I'll swap to tubeless in September and see what pressures feel the best, with no worrying about pinch flats.
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The point is that there is no free lunch. If there’s not enough pressure in the tire on a tubeless setup, by definition you can’t pinch flat, but bad things still happen.
So whether, you’re tuned or tubeless, there still needs to be enough air pressure to support the load and forces imposed. The precise math may change as to what is too low, but bad things still happen if the pressure is too low.
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So don't run 28 mm tires at 5 psi like a mountain bike. 🙂
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The same physics that cause a tubed tire to compress enough to pinch a tube against the rim, compress a tubeless tire against the rim sufficient to cause rim damage and/ or the bead to separate enough to flat the tire.
The point is that there is no free lunch. If there’s not enough pressure in the tire on a tubeless setup, by definition you can’t pinch flat, but bad things still happen.
So whether, you’re tuned or tubeless, there still needs to be enough air pressure to support the load and forces imposed. The precise math may change as to what is too low, but bad things still happen if the pressure is too low.
The point is that there is no free lunch. If there’s not enough pressure in the tire on a tubeless setup, by definition you can’t pinch flat, but bad things still happen.
So whether, you’re tuned or tubeless, there still needs to be enough air pressure to support the load and forces imposed. The precise math may change as to what is too low, but bad things still happen if the pressure is too low.
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The nice thing about hookless rims is that the rim bead area is so much stronger. It takes a lot to hurt those over the hooked-bead rims.
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