Hi all, just asking because the 'official' minimum pressure for my Kenda tyres is 40psi, whereas I typically run them at 35 back and 30 front.

I have some fairly big 2.35" Small Block 8s now and was thinking of running them a little lower, but my rims are fairly narrow (XM719). Has anyone got advice/experience as to how low is safe?!

Thanks!

EDIT: Running tyres and tubes, not tubeless

After replying to a different thread I realise the answer to this question will be very rider-weight dependent… I am 13.3 stone or ~85kg

I suspect they design the tyre to a 75kg "average" rider. That said, their minimum pressure rating may not be because it'll roll off, it may be because it'll cause excessive sidewall wear, or because it'll be too soft and not protect the rim due to tyre construction etc. My advice would be run whatever pressure feels right to you and see how the tyre reacts.

Lots of factors I'd have thought – pinch flats are also a threat.

As al says – lots of factors including what tyre and what sort of construction.

In general I find anything less than around 35 psi just feels horrible – like a flat tyre and squirms around. Some tyres even lose grip as the pressure drops as the knobbles fold in on themselves.

Experiment – its the only way

Yeah… bit of an open ended question. Has anyone ever managed to roll a tyre off the rim?

95kg. Flow rims, UST Advantage tyres. I was happily running 20/25 psi. Tyre4s were fine. I only went up to 22.5/27.5 as I occasionally felt the rim through the tyre on big hits.

I think tubeless is another variable to consider. My 2.35" Kujos with tubes are about 30/35 f/r

TJ – not to sound too personal, but how much do you weigh? Tyre contact patch being proportional to weight etc.

Yeah… bit of an open ended question. Has anyone ever managed to roll a tyre off the rim?

Yes, twice. Both running ghetto tubeless. One on a Tioga factory DH 2.3 at 25psi (front) and one was an IRC mudmad DH tyre at ~28psi with a funny landing. Never run that low with tubes as they pinchflat long before that pressure.

When I converted to Ghetto Tubeless using Panaracer Fire XC tyres, I had the rear come off the rim after a squint landing, wasn't particularly low pressure, approx 35PSI, but the tyres were very loose on the rim when I fitted them.

Yeah… bit of an open ended question. Has anyone ever managed to roll a tyre off the rim?

seen it done in DH competition.

but i generally find the sidewalls will wear out before the tyre comes off.

once rode 3-5 miles with a flat tyre (tracknuts and no spanner) and the tyre stayed on….

poppa – Member

TJ – not to sound too personal, but how much do you weigh? Tyre contact patch being proportional to weight etc.
Around 13 stone these days.

I think with me a part of it is from motorcycling – a tyre that squirms when you are on your motorbike is punctured and you are about to crash.

poppa – Member

Yeah… bit of an open ended question. Has anyone ever managed to roll a tyre off the rim?

I have seen several people do it – all with tubeless setups and low pressures

im around 12 1/2 stone and run my mtbs at 28 psi front and rear on tubeless and tubed wheels

Ok, so it looks like I will run into problems with pinch flats before I risk the tyre coming off! I must admit, I don't like tyres feeling too squirmy either, but I only usually notice it on the rear (hardtail rider) – I have to keep checking to see if I have a puncture!

Depends on the tyre and rider weight.

80kgs odd here, and 22 psi is fine on the DH bike with dual ply UST high rollers, but would be squirrely as anything on 5-600g tyres on the XC bike.

As you reduce pressures you'll find they go from: fine->pinch-flatting more -> squirmy -> rolling off when you're caning it.