Tyre pressures

[Maladict]

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]

It depends how rough the road surface is; the smoother, the higher, the narrower, the better.
Otherwise, not.

[border-rider]

On a really rubbish surface, a very hard tyre can actually make you a bit slower

[Maladict]

Hmm, I looked at this topic, then I looked again and there were less replies. 

[valkyrie]

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.

[giropaul]

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]

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]

Doesn't it depend how heavy you are also?

[Maladict]

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).

[giropaul]

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]

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.