Author Topic: Tyre pressures  (Read 2236 times)

Maladict

Tyre pressures
« on: April 27, 2008, 10:11:02 pm »
I checked the tyre pressures I had on the bike I did the TT on last week - 80 PSI.  That's what the LBS must've given me.  I pumped them up to 100 PSI tonight, but I think they're good for 120.  How much would that knock off at 20mph compared to 80 PSI (25mm tyres).

Also how much would 23mm tyres improve things on a 10?

LittleWheelsandBig

  • Whimsy Rider
Re: Tyre pressures
« Reply #1 on: April 27, 2008, 10:29:55 pm »
It depends how rough the road surface is; the smoother, the higher, the narrower, the better.
Otherwise, not.
Wheel meet again, don't know where, don't know when...

border-rider

Re: Tyre pressures
« Reply #2 on: April 27, 2008, 11:00:27 pm »
On a really rubbish surface, a very hard tyre can actually make you a bit slower

Maladict

Re: Tyre pressures
« Reply #3 on: April 27, 2008, 11:31:31 pm »
Hmm, I looked at this topic, then I looked again and there were less replies.  :)

valkyrie

  • Look at the state of your face!
    • West Lothian Clarion
Re: Tyre pressures
« Reply #4 on: May 18, 2008, 10:26:12 pm »
Don't you check your tyre pressure before a TT? I check mine before every audax, FFS. Mind you, that's mostly cos the front one seems to lose pressure quite quickly in the garage. I usually ride at about 110 - 120psi, but I've really no idea what the optimum pressure is.
World Class Excuses for Piss-Poor Performances

Re: Tyre pressures
« Reply #5 on: May 19, 2008, 08:55:46 am »
On pressures, probably 8 bars depending, as said previously, on road conditions and your weight.

On tubs, 8 bars as a guide for cottons, but 9 bars for silks (setas).

Wibble

Re: Tyre pressures
« Reply #6 on: May 20, 2008, 05:08:42 pm »
Also how much would 23mm tyres improve things on a 10?

23mm will roll worse but give less wind resistance.  They'll make you slower unless you're wheely fast with a capital F.

Seineseeker

  • Biting the cherry of existential delight
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Re: Tyre pressures
« Reply #7 on: May 20, 2008, 05:15:54 pm »
Doesn't it depend how heavy you are also?

Maladict

Re: Tyre pressures
« Reply #8 on: May 20, 2008, 05:21:13 pm »
Don't you check your tyre pressure before a TT? I check mine before every audax, FFS. Mind you, that's mostly cos the front one seems to lose pressure quite quickly in the garage. I usually ride at about 110 - 120psi, but I've really no idea what the optimum pressure is.

They were inflated for me the day before.  I don't normally experience significant loss of pressure in 24h.  However I think the tubes were a bit thin (I noticed a lot of loss of pressure before the Fred Whitton and I think that's why I got a snakebite).



Re: Tyre pressures
« Reply #9 on: May 20, 2008, 07:51:08 pm »
You are not using latex tubes are you? They will lose 10psi or more overnight.

With light tyres, and especially latex tubes (or tubulars) it's a good idea to let them partailly down after each ride anyway.

Maladict

Re: Tyre pressures
« Reply #10 on: May 20, 2008, 10:18:37 pm »
You are not using latex tubes are you? They will lose 10psi or more overnight.

With light tyres, and especially latex tubes (or tubulars) it's a good idea to let them partailly down after each ride anyway.

I suspect they might be.  I normally use butyl rubber tubes, but it's what the bike (Madone) came with - Bonty Racelight inners, I can't find the spec.  But they feel smooth compared to Butyl tubes so I suspect they are latex.  I binned them.