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psi advice please

andyh01andyh01 Posts: 571
edited November 2013 in Road general
Hi all, just fitted some conti 4 seasons 25mm on the training/commuting bike recommended PSI between 95-120psi is there a concensors on the best PS I mainly to get Max grip and comfort over performance gains ? Previously ran supplied bontrage 23 not sure of exact model and ran at Max 120 PS I Thanks Andy

Posts

  • meursaultmeursault Posts: 1,433
    tumblr_mly455rW5P1qjemo2o1_500.gif
    Superstition sets the whole world in flames; philosophy quenches them.

    Voltaire
  • SproolSprool Posts: 1,022
    how much do you weigh? I went from 23's at 110 psi to conti gp4000s 25's at 95. I weigh 12.5st. Running at the slightly lower pressure made for a little more cushioned ride.
  • andyh01andyh01 Posts: 571
    Thought be case similar to helmet debate... I also weigh in region of [email protected] [email protected] twelve stone on a trek @.! Two point one five mile commute each way plus training don't wan damage rims or risk puncture running at too low but don't want lose grip at too high
  • meursaultmeursault Posts: 1,433
    I don't know if it's any help, but I also have Conti 4 seasons, just put 100 in front and back. No idea if it's 'correct' but it works for me.
    Superstition sets the whole world in flames; philosophy quenches them.

    Voltaire
  • kajjalkajjal Posts: 3,380
    meursault wrote:
    I don't know if it's any help, but I also have Conti 4 seasons, just put 100 in front and back. No idea if it's 'correct' but it works for me.

    Same but put 105 front and back on 23mm 4 seasons. I weight under 16 stone. The balance to look for is too low and you get too much drag and too many punctures v too high and you get loads of vibration from the road. It is down to personal preference between those two extremes.
  • 100 psi.

    It's a nice round number.
  • andyh01andyh01 Posts: 571
    Thanks out of interest what advantage is there in running at diff PS I for front and back and is it best to have front higher PS I given the weight transfer under braking on front end?
  • marcusjbmarcusjb Posts: 2,412
    The rear will usually have slightly higher pressure - it is taking the majority of your weight. The front is taking less weight and you will feel the comfort benefit of a slightly lower pressure as your arms and shoulders get a little more cushioning.
  • smidsysmidsy Posts: 5,273
    You have stumbled (or maybe intentionally) on a black art indeed.

    Tyre pressure is determined by a combination of factors (some unique to you) such as tyre width, rider weight, rider distribution, road conditions, weather and tyre make up.

    Some basic rules can help i.e. wider tyres can run lower pressure than narrower ones, rear tyre generally should have more psi than front, psi should be reduced in poor weather etc.

    You need to experiment to find your ideal.

    PS: if you find the magic answer can you tell everyone which saddle is the best one for everyone too :mrgreen:
    Yellow is the new Black.
  • CiBCiB Posts: 6,098
    The answer is 102.3psi, or enough that your thumb can make a small indent in the surface of the tyre with the correct amount of squeeze action. Both are correct, you'll find. :idea:
  • keef66keef66 Posts: 13,123
    I too run 25mm GP 4 Seasons, as the name suggests, all year round. I weigh 10.5 stone / 67kg and find I get a comfortable ride and decent grip at only 65-70 psi front, 80 psi rear. Probably not immune to a pinch flat if I hit a serious pothole though.
  • ju5t1nju5t1n Posts: 2,028
    It’s your maximum heart rate minus your IQ
  • smidsysmidsy Posts: 5,273
    ju5t1n wrote:
    It’s your maximum heart rate minus your IQ

    But how do you inflate to negative pressure? :mrgreen:
    Yellow is the new Black.
  • ju5t1n wrote:
    It’s your maximum heart rate minus your IQ

    You owe me a new tyre - I just tried that and it exploded…

    WTF?
  • BobbinogsBobbinogs Posts: 4,841
    mmacavity wrote:

    That Vittoria app looks good, until you realise that tyre size has not been factored in, doh!

    To the OP, there are 3 pressures for a tyre:
    1. The minimum pressure needed to avoid pinch flats (there are a few charts around on this but I don't think there is any science...and if you twonk a pothole the charts go out of the window anyway)
    2. The maximum pressure (determined by reading the sidewall but, let's face it, that won't be the real maximum just the most that a risk adverse litigious society has led the manufacturer to come up with).
    3. The optimum pressure (which is between the above two and is highly subjective)

    So, a few factors and most folks don't accurately measure weight distribution... so the whole thing about a specific figure is nonsense, which is why these threads always end with the 'it depends' concensus.

    FWIW, I weigh 65kg so on 23's run 85/95 but will go 90/95 for a hillier route. 5 psi down for 25's.
  • hopakhopak Posts: 193
    smidsy wrote:
    ju5t1n wrote:
    It’s your maximum heart rate minus your IQ

    But how do you inflate to negative pressure? :mrgreen:

    Turn your bike upside down, all pressures then become negative and it will float away.
  • mpiempie Posts: 84
    11st and run ~90psi on GP4000s 23mm and ~80psi on 25mm. No punctures in the last year.
    I've tried higher pressures to see if I can detect any less rolling resistance, but generally find that on most tarmac surfaces (not smooth) the increased 'chattering' at high pressure seems to slow me down.
  • andyh01andyh01 Posts: 571
    Thanks for the info went out this morn on around 95 PS I simply because I miss read the packaging where it specified the min 95 didn't see the min or Max 120, and didn't have time to pump up anymore as late. To be fair the ride didn't feel too different think they roll better then old ones and less vibration as used to running at 120 on the old 23s. My pump gage isn't that accurate anyway, think I might try and run at 110 I sh and leave at that, to take into account bad weather conditions as won't mess around deflating a little in bad weather or is around 110 PS I in bad weather to high
  • smidsysmidsy Posts: 5,273
    Wet weather around 85 - 90 is sensible IME on a 25mm tyre.
    Yellow is the new Black.
  • BobbinogsBobbinogs Posts: 4,841
    Personally, I wouldn't pay too much attention to the min pressure value stamped on a tyre as it doesn't factor in rider/bike weight, type of road, etc., and it is snakebites that are the main problem with going low. OK, there needs to be a min to keep the tyre on the wheel but 95 PSI is stupidly high as a minimum for doing that.
  • andyh01andyh01 Posts: 571
    smidsy wrote:
    Wet weather around 85 - 90 is sensible IME on a 25mm tyre.
    Would that be same for frost/ice/snow? :lol:
  • smidsysmidsy Posts: 5,273
    AndyH01 wrote:
    Would that be same for frost/ice/snow? :lol:

    Indeed so...in fact any figure you like as it makes no difference when the bike is in the garage :lol:
    Yellow is the new Black.
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