Tyre pressures

[robing]

Forgive me if this has been covered before. I read this article from Wiggle:

https://guides.wiggle.co.uk/how-get-cor ... campaign=-

According to this, on my road bike running 25mm tyres I should have 90/93 psi in the front and rear tyres. I normally run my tyres much higher than this, around 120 to 130 psi. (I used to have 23mm tyres so guess I should reduce for 25mm tyres). I've always kept the same between front and rear. Thoughts?

[gaz]

Discussion of tyre drop has cropped up plenty of times.

I've certainly reduced my tyre pressures since reading it, although perhaps not quite so much as the graph suggests*. My ride is more comfortable as a result.

*Largely because I can't be bothered to do more than estimate the all up weight of rider, bike, saddlebag, etc

[meic]

The figures seemed right to me. I get an extra 8psi in each tyre due to my weight.
Should I get another 2psi for the bike (food and flask etc)'s extra weight.

Then there was this bit.

Because of the risk of inner tube pinch flats, sometimes you need to run a slightly higher pressure than would be optimal in an inner tube set-up, to reduce the risk of puncturing.

I have had a few snakebites which taught me not to let my 25mm front tyre get below 100psi.

[softlips]

Run my 25's at 80 and my 32's at 70. The former are tubeless.

[pwa]

It does depend partly on your weight, of course. A light cyclist like my Missus can get away with much lower pressures than me.

[Samuel D]

Wiggle does take a stab at accounting for weight, pwa.

I think the Wiggle pressures are about right, at least in the sub-70 kg range that I know from personal experience. I disagree with their suggestion to run tubeless at lower pressures for two reasons: (1) having the rim bottom out on big impacts has the potential to be worse than a mere pinch flat, and (2) my pressures are mainly chosen for comfort and rolling resistance; if your pressures are mainly chosen to avoid pinch flats, my view is that your tyres are too narrow.

But 120–130 PSI is too high for a 70 kg cyclist on 25 mm tyres except in special circumstances (e.g. smooth tarmac, Moulton suspension, climbing only). The typical vibration-induced energy losses are high (the energy coming from your legs’ work, remember!), and even the strict rolling resistance is trivially lower than at 20 PSI less: see Bicycle Rolling Resistance for details.

The front pressure would ideally be lower than the rear, since it usually bears less load, is key to comfort (the saddle absorbing much vibration at the rear), and needs good grip to avoid a dangerous front wheel skid. The more careful you are to avoid whacking obstacles with your front wheel, and the more gently you brake, the greater should be the pressure difference between front and rear.

[531colin]

For 32mm tyres at less than 70 kilos, I run 45 front, 55 rear.....pretty close to Wiggle's guide for 35mm cross tyres.

[Mick F]

I have 120psi rear and 80psi front.
23mm Rubino Pro.

As far as I'm concerned with my 531c springy frame, it's perfect.

[meic]

To contrast that, my daughter has 50psi front and rear in her 23mm tyres!

[Airsporter1st]

Discussion of tyre drop has cropped up plenty of times.

I've certainly reduced my tyre pressures since reading it, although perhaps not quite so much as the graph suggests*. My ride is more comfortable as a result.

*Largely because I can't be bothered to do more than estimate the all up weight of rider, bike, saddlebag, etc

If you wanted to, you could use simple bathroom scales to measure your wheel loading one at a time, since that is what the chart works on. For amximum accuracy, you either need to be able to balance stationary or arrange it that you can very lightly rest against e.g. a wall, without applying any upwards or downwards load with your fingertips.

[Mick F]

To contrast that, my daughter has 50psi front and rear in her 23mm tyres!

50psi in mine would be running on the rim at the rear.
12st 4lbs = 172lbs = 78kgs

I guess your daughter is quite light.

[meic]

Yes, less than half your weight, so around half the tyre pressure should be fine.

[robing]

I have 120psi rear and 80psi front.
23mm Rubino Pro.

As far as I'm concerned with my 531c springy frame, it's perfect.

That's a big pressure difference between front and rear. That's not your Chopper is it?

Today I went out on my bike with 23mm tyres. 120 front and rear, felt great. Was a beautiful day.

[robing]

What about puncture resistance? The higher the pressure the better, surely?

[Mick F]

Two answers.
Yes, big pressure difference.
I used to do 120/100, but found that 120/80 was fine.
The Mercian is 73deg parallel so the bulk of my weight seems to be well to the back, and the 120 seems to work ok.
The front is very light, so 80 is fine.

Rarely get punctures, and I can't remember the last on on Mercian.
Yes, I can actually, because I keep records.
10th Sept 2015 at Lydford in Devon. Never found what the puncture was caused by, as whatever it was went in and then out. Could have been a thorn.