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Tyre pressure for 28mm tubeless on 17mm internal.

bristolpetebristolpete Posts: 2,255
edited August 2018 in Road general
Hi.

Running pro one tubeless tyres and wondered what others think a sweet spot pressure for 28mm tubeless on 17mm internal might be on a 30mm rim carbon clincher. Not sure if I need to add more air as I read 50% more air in the chamber or indeed lower it ?

90kg rider so do not want to feel sludgy, nor do I want the bike to go back to being rock hard akin to the 23mm days. Could I go 70 on the front for example ?

Anyone found any nice pressures to start with ?

Cheers.

Pete.

Posts

  • tonysjtonysj Posts: 326
    Hi Pete,

    I have 25 mm Pro Ones and I'm 78 kg. I run 80 psi in the front and 85 psi in the rear. I find the rear feels a little soft if the road surface is censored but other than that I think they are right for me.

    I would guess maybe start with 75 front and 80 rear and see how it feels.

    Regards.

    Tony.
  • whyamiherewhyamihere Posts: 7,357
    70-75 psi should feel pretty good with 28s at your weight (I'm similar). The best thing to do is to experiment though - Use 70 as a starting point, then drop it and raise it gradually until you can feel how the pressures affect the ride and find something you like.
  • bristolpetebristolpete Posts: 2,255
    Great - thanks. Was not sure if the objective with 28mm was to go back up towards 100 psi but seems not. Will start at 80 front 85 rear tomorrow.
  • apreadingapreading Posts: 4,535
    General rule of thumb is that 15% tyre drop when in use is around the optimum.

    You can use this to work it out: http://www.dorkypantsr.us/bike-tire-pre ... lator.html (bear in mind that if you use the top box it is the individual weight at each wheel - the bottom box is easier to use.)
  • oxomanoxoman Posts: 8,348
    Currently use 28s on my best bike with carbon wheelset with 80 in the front and 95 in the back. Weight wise I'm around 85kg plus probably another 3kg or so for water and bag when commuting.
    Too many bikes according to Mrs O.
  • Do you stay seated on climbs, or do you get out of the saddle? This will affect how much load is being supported by the front and rear wheels/tyres, a nice low pressure for comfort while seated could feel horribly squishy while out of the saddle.

    It's not just your weight that needs considering, it's everything that the tyres are supporting. You; bike; clothing; water; food; repair kit; mobile etc. For me that's ~92Kg on the Cube, if I head out with with 2.7 litres of water, now using ~80/90PSI with GP4000S2s and latex tubes if I expect to climb out of the saddle (~70/85 if it's a planned recovery ride where I stay seated on climbs).

    Given you don't need to worry about snakebite punctures, I would guess at 65-70 for the front and 80-85 for the rear, as a starting point. But you may find that squishy, out of the saddle.
    ================
    2020 Voodoo Marasa
    2017 Cube Attain GTC Pro Disc 2016
    2016 Voodoo Wazoo
  • Do you stay seated on climbs, or do you get out of the saddle? This will affect how much load is being supported by the front and rear wheels/tyres, a nice low pressure for comfort while seated could feel horribly squishy while out of the saddle.

    It's not just your weight that needs considering, it's everything that the tyres are supporting. You; bike; clothing; water; food; repair kit; mobile etc. For me that's ~92Kg on the Cube, if I head out with with 2.7 litres of water, now using ~80/90PSI with GP4000S2s and latex tubes if I expect to climb out of the saddle (~70/85 if it's a planned recovery ride where I stay seated on climbs).

    Given you don't need to worry about snakebite punctures, I would guess at 65-70 for the front and 80-85 for the rear, as a starting point. But you may find that squishy, out of the saddle.

    Exactly this. Too easy to forget any recommended psi advice for rider weight doesn't include any of the additional guff. I'd be inclined to add about 3-5kg to your "rider weight" (depending on how much guff you choose to carry). Shoes, clothing, helmet, mobile phone, sunnies, multi tool, pump or CO2, one or two bottles of liquid!! Put all that on a scale and see what it comes in at. Oh, throw a few gels, chicken legs or whatever you fancy in there too for good measure...
  • cyclecliniccycleclinic Posts: 6,865
    Try different pressures and uses what feels right to you. Ideal Pressure will vary depending on road conditions.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • bristolpetebristolpete Posts: 2,255
    RIghty ho thanks all. Heading out tomorrow for a 'shakedown ride' as done a couple of quick to and from work options but nothing extended. Look good though and nothing like the MTB tyre size I was dreading. R5 complete now and just waiting on new bottle cages to finish it off. My n+1 has been completed and the R5 is now my sole road machine in effect.
  • joe_totale-2joe_totale-2 Posts: 1,075
    I'm 70kg and using Hutchinson Sector 28's. I'm running 65 at the front and 70 at the rear and it's great, very comfortable ride and no discernible loss of speed.

    I agree with the poster above that 70 front and 75 rear would be worth trying.
  • zefszefs Posts: 484
    Mavic app recommends 85-90 for your weight/wheels.
  • cyclecliniccycleclinic Posts: 6,865
    Experiment and see. I don't understand why the op didn't do this on the first place.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • I ran your numbers through a well known calculator (https://goo.gl/zonJ2i) and it said 83 psi front and 93 psi rear for good conditions....dont know if that helps. MM
  • bristolpetebristolpete Posts: 2,255
    Experiment and see. I don't understand why the op didn't do this on the first place.

    It is good to talk as they say.
  • indypindyp Posts: 733
    I have same tyres but size 25mm and on 19mm internal width rim. rode them around 55/60 psi this week and still managed one of my quickest rides! It wasn't planned just not topped up air for a few days and went out quickly. It definitely made the bike more comfortable and without noticeable difference to speed although I've now gone back up in pressure. I won't be too worried if I did the same again
  • bristolpetebristolpete Posts: 2,255
    indyp wrote:
    I have same tyres but size 25mm and on 19mm internal width rim. rode them around 55/60 psi this week and still managed one of my quickest rides! It wasn't planned just not topped up air for a few days and went out quickly. It definitely made the bike more comfortable and without noticeable difference to speed although I've now gone back up in pressure. I won't be too worried if I did the same again

    Seems that the internal width has quite an impact as my spin hand builts with a huge 19.85 internal make my 25mm more supple than 28mm on 17mm internal. Funny old game. And Vittoria corsa g certainly way more supple than pro one tubeless as a tyre, which I suspect is based on thread count.
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