Just as a starting point for me, thanks guys.
HR 2 front, Minion SS rear.
Assuming standard not plus tyres. Weight in stones (including gear) times two. Then add two psi for the rear, subtract one psi for the front.
Yeah, not plus tyres mate. Ok psi obvs?
Thanks!👍
I've always used riders weight in lb / 7 = PSI
-1 for the front and +1 for the rear.
think I got this from Stans website many moons ago. I am still on unfashionably old 26" wheels. Not sure how this applies to bigger wheels with fatter tyres.
Yes PSI not bar!
I have to run the Minion SS harder than I run more rugged tyres - not so much for the fragility, but so that the side-knobs don't touch the ground all the time.
Interestingly whitestone's forumla works out for me even though I've never done it off anything other than 'ride till you pinch flat then up it a tad'.
There’s a handy calculator on the Vitoria website. Not perfect, but good start
Wow there's a calculator for tyre pressures 😲
I'm purely in the school of pump up feel it with my hands, let out until feels right.
Try a trail and let more out if needed depending on surface type.
I tend not to over think it too much
42
weight in lbs/7 to get max pressure. The sweet spot will be below that.
mine is front (-8) Rear (-2) on soft ground. Front (-4) Rear (-0) on hard ground.
HTH
I’m purely in the school of pump up feel it with my hands, let out until feels right.
Try a trail and let more out if needed depending on surface type.
Amen.
A weight based calculator that doesn’t take into account ground conditions; air temperature (and how much extra grip the rubber gives on warm summer days); riding style; how much extra weight the rider is hauling because they lie about their weight; the fact they haven’t emptied their pack in two years and are carrying a ton of pointless tools; the fact that different tyres need different pressures; tubeless v non- tubeless.
Yeah, that’ll work.
As a starting point, for tubeless I’ve always used the all up weight of me and kit in lbs/7 minus a bit for rear and a bit more for the front and its worked for me on most terrain.
No hard and fast rule, it’s a starting point, much like the air pressures, rebound and compression settings for suspension, all subjective and down to personal preference.
Member
weight in lbs/7 to get max pressure. The sweet spot will be below that.mine is front (-8) Rear (-2) on soft ground. Front (-4) Rear (-0) on hard ground.
HTH
That would be waaaaaay too low for me. Horrid squidgy feeling with the tyres rolling off the rim on cornering
One thing not mentioned here is rim width. Wider rims the tyre rolls of the rim less so lower pressures can be used. I have old narrow rims hence needing 30+ psi
27/ 30 would shake my fillings out, I’ve been at 17/ 19 since recovering from my tendonitis. It’s a bit bouncy but more comfortable than the 21/ 23 I had set before and no loss of grip.
That’s 2.4s on the 650b and 2.4/ 2.3 on the 26. I never knew there was a formula, I have just fiddled around since I bought my first bike and progressively found lower was better.
Starting point: tyre deflection of about 15-20% with your weight on the bike.
There's no rule except what works for you.
Love these threads such old wives tales!
Any formula that doesn't account for tyre width is clearly BS right off the bat.
PSI stands for Pounds per square inch. Your weight in pounds, your contact patch in square inches. Simple. Add your weight and your bike weight in pounds to get total weight. Use Pi x R^2 (R here being the tire width/2) to get the rough contact patch in inches for each tire. Double this (unless on a unicycle). Now you divide them up to get PSI you'll need.
That's your starting point. A larger contact patch can be made by reducing pressure, a smaller one by increasing. The ultimate limit will be a contact patch so large that your rim touches the tire in the middle. Bear in mind that pounds of pressure will be more when landing of course...
Personally I've always found that weight and tire size assuming a circular patch gives me spot on numbers for best control and feel. I give a slight bias to the rear tire because of weight distribution etc. but every 1psi I remove from one I add to the other.
Your weight in bird feathers divided by the number of public KOMs you have. 😉
I’m surprised by some of the formula.
I run my front 10psi lower than my rear, works for me.
Don't forget to divide by your bimble factor. Bimble = age / avg speed.
So on a fat bike you'd run the front at zero? Bless you for taking part.
I just shove 40psi in mine.
I've always used the formula:
Trial + error = best pressure that suits