right tyre pressure

Calculator is all well and good if you have decent tyres which will handle , for example, 140 psi on the rear, but when that exceeds the manufacturers recommendation, or even that specified for the rim, it's probably not a good idea

Handmade tubular type with high thread count will work, but not much else

And no, I don't think going up to a bulging 25 or 28 is what I want to do when I've spent loads on an aero wheelset!

Still,, seems to justify my high pressures for the rear, though says my front needs to be reduced

I'm bemused by the science and the calculator.

I currently inflate both tyres to 90. What am I doing wrong?

I am 86 kg and have an 8kg Giant TCR Advanced. I have 23c Giant P-SLR 1 tyres. (Giants top tyres with different compound front and rear) The max pressure is 120psi and I have been running at 110 psi. A few months ago I came off the bike in the wet when the rear end slid away from me. Still recovering from a wrist injury. Are my tyre pressures too high?

Here's an online calculator based on the 15% drop method: http://www.dorkypantsr.us/bike-tire-pressure-calculator.html

Works well IME

According to that, I'm supposed to have 9.5 Bar in my tyres. Only problem is, my Conti 4000 S tyres say max pressure of 8.5 bar...

Wonderful...

Al, I'd suggest your pressures sounds about about right for your weight. You and Shane should try 10 psi either side of what you run now and see how it feels, establish what suits you.

Get the Vittoria Ityre pressure app, gives you ideal pressure based on the tyre and conditions. It is intended to work with vittoria tyres, but you can get it to work pretty well for other brands

Vittoria do an app for their tyres, I think on the open corsa I ended up running 120/115 in dry smooth conditions and 5-10 lower in wet/rough

Ha -answer is 'it depends'

105 sounds reasonable, I'd you feel reasonably comfortable and quick then it's right. Worth experimenting though.

Otherwise..

Follow manufacturers guidelines for your weight (if specified), take into account road surface you're riding on that day -lower pressure for rough surfaces - and type of riding (I always go higher for TT's)

Clinchers will also have a specified max for the wheel, tubs can go loads higher. I've had anything from 100 - 160, depending! But I'm quite heavy..

very interesting, one thing I have noticed is my tires after a 80k ride drop pressure from 110psi to 85psi, that measurement I gave taken the last three 80k rides I have done.

proving the point that you should alwsys check your pressure at least before anything over 20k

It depends a little bit on the tyres you're using but as a rule the front should have 10 less than the rear and as above 105 is probably high.

Personally I think the article suggests pressures that are a bit low for my liking (round about 80/90psi for me) but it's in the ball park. I'd also say I add 10 for good surfaces (racing crits, riding in France) and another if I'm on my race tyres as they're extremely supple.

NO. Not unless you are on 23c's and weigh 100kg. Follow this PDF, it's science. Anyone else is wrong.

http://www.bikequarterly.com/images/TireDrop.pdf

Your arse, hands and times will thank you.