Tyre pressure debate

[lukemillar]

Originally Posted by Skip

Had an evening session at Snetterton last night and dropped my pressures -3 on the rear and -4 on the front - it seemed to work for me - but then I am no expert! lol Meant to check the pressures when I got back into the pits but was so pumped up I completely forgot every time!

cool! having fun is the main thing.

I took some pics of what I am babbling on about this morning, but they are out of focus, so I'll try again tomorrow!

Originally Posted by lukemillar

Bridgestone man said road tyres are designed to work at ~70c.

Is that not a slighlty simplistic statement from the Bridgestone man? Each tyre has an optimum temp, but works over a wider range. A touring tyre will work better over a wider and cooler range, whereas a race tyre will have a smaller, hotter, range.

You need this.

[lukemillar]

Originally Posted by simesb

Is that not a slighlty simplistic statement from the Bridgestone man? Each tyre has an optimum temp, but works over a wider range. A touring tyre will work better over a wider and cooler range, whereas a race tyre will have a smaller, hotter, range.

You need this.

We are talking road tyres on the track, not race tyres. It's not about the precise temp - the "~" means around, but more the way in which the heat is generated and dispersed and the affect this has on that operating temp.

Hmm - you link has four letters replaced with ****! Not sure what is censored.....

[Skip]

Originally Posted by lukemillar

cool! having fun is the main thing.

It is indeed - only two groups and (without trying to sound big headed) I was definitely one of the faster ones in the slow/intermediate group - tried hanging off the bike to see if knee would touch tarmac to no avail - pegs ground out way before I got close Gave up in the end as I was going plenty fast enough through the bends anyway!

Originally Posted by lukemillar

Hmm - you link has four letters replaced with ****! Not sure what is censored.....

Stoopid censor. it's "bright water" without the space, which the censor seems to think contains a naughty word.

[lukemillar]

Originally Posted by Skip

It is indeed - only two groups and (without trying to sound big headed) I was definitely one of the faster ones in the slow/intermediate group - tried hanging off the bike to see if knee would touch tarmac to no avail - pegs ground out way before I got close Gave up in the end as I was going plenty fast enough through the bends anyway!

You should check out some pics of yourself if you can. Really helpful for checking out body position and stuff. It will probably feel like you are hanging off a lot more than you actually are. Was there a trackday photographer?

[Skip]

Originally Posted by lukemillar

You should check out some pics of yourself if you can. Really helpful for checking out body position and stuff. It will probably feel like you are hanging off a lot more than you actually are. Was there a trackday photographer?

There was but he was only at the Russell chicane - somewhere I wasnt trying that hard - a friend took some pics around the circuit so will check them out - he said I was only 3-6 inches away so I was close - the Zed has very poor ground clearance on the pegs though

[lukemillar]

Large River Patterns

This is what you get when your pressure is too low. Bigger footprint, less heat and larger tear patterns. Rear psi was ~6 lower than the manufacturers recommendation (36 psi):



Small River Patterns

This is the sweet spot! You get the same patterns but they are much smaller indicating that the tyre is operating at it's optimum temperature. Rear psi was ~1-2 lower than manufacturers recommendation (36 psi):



NOTE: This is just the info relayed from the Bridgestone technician. I'm running Michelin Pilot Power 2CTs, but he said that the principle is the same for most road tyres on the track. Also said that the front doesn't generate as much heat, so leave that pressure as is.

[Skip]

That first picture is pretty much how my tyre looked after the trackday on Monday evening - so the pressures were too low? I checked them last night and the rear was at 39psi - normal road pressure is 42psi.

[lukemillar]

Originally Posted by Skip

That first picture is pretty much how my tyre looked after the trackday on Monday evening - so the pressures were too low? I checked them last night and the rear was at 39psi - normal road pressure is 42psi.

No idea! This thread was supposed to be more of a discussion than a "Do this!".

Like I said I have always dropped mine, but now have found out something to the contrary, with some theory and images to support it. I think I'm going to experiment a little on my next trackday, but as a base I'll drop 2psi on my rear and keep the front as is.