I am running Bridgestone BT45's on the BMW at 30 PSI front and rear...mainly as thats what the Cali School set them to on the Thruxton... Consulting the Inneret....the pressures are run higher on modern tyres and they are saying 34 front/ 38 rear. I noticed a couple of the old boys checking their pressures after being on the track.....whats all that about..... The front tyre has wear right to the edge and the rear about 5mm left....is that coz the front is a 19"?
if you want to have a constant tyre preassure put nitrogen in them I do this on the car tyres as it is denser than air and the molcules are larger it also does not heat up as much as normal air while racing go one put so F1 tech stuff into old school racing
Wow...from footpump to Nitrogen...... they would ban me. We used Nitrogen in Air Con work, because it was dry, it still expands and contracts like other gases.....mind you thats at 150 psi plus.... I read about some stunt guys who used Hydrogen, put pinhole leaks in the tyres and lit them before the stunts......
Remember that modern radial tyres always run much higher pressures than old style cross plies (something to do with the different construction). The BT45 is a bias ply, so technically a cross ply. I run 30/32 in the BSA, 28/30 on Titans 32/34 on GT750. Your BMW is fairly light so 30/30 sounds about right.(EDIT: Those are the figures on my gauge, I don't know if its accurate, but its consistent , so the actual figure doesn't matter much, I know that figure on my gauge works. )Maybe the guys checking pressures after the race were seeing how much they had gone up? There's a theory that says that if the pressure increases by 5 psi in use (ie 5 psi increase once the tyre , and thus its air , is hot), then the pressure is right. Lower the pressure, more it will go up (more tyre flex I suppose)
The air we breath has 78% nitrogen and 21% oxygen...I don't really see all the fuss about getting the extra 22%. I'm a low pressure kind of guy - low pressure gives more contact patch, and so more traction. I can't believe how much grip my S11 had at 8 psi. I use 20 psi front and 25 psi rear with my K70's, there is a shit load of tyre on the road, much more than the Bridgestones with stock pressures. I come to my weird theories by not listening to other people and experimenting on my own - don't listen to me, but do make your own choices.
You're good at starting religious threads Volty... was it you asking about the OIL the other day? +1 on Nitrogen, i run it in my car and it lost only a couple of psi over close to one year Bruno is typically on 34/38psi I would experiment before deciding on anything ... appropriate tyre pressure depends on the road conditions as well as suspension settings. If the track is in good condition with no bumps on the surface then i would probably stiffen up the suspension and add pressure to tyres (as compared to regular road use). Tyres will have max pressure alowed stamped on them but most modern (bftp) tyres can take at least 40psi. My 2c (and I've been wrong before)
36 Front and 40 rear.......+2 psi if racing......
36 Front and 40 rear.......+2 psi if racing...... seems to be what they say....I just wonder what determines it?
I just wonder what determines it? perhaps how many pies you had for break-fats
On the LC on BT45 I used to run 32/34 which are figures I guessed at and seemed to work, trying different pressures and see what feels best for you is really the only way to do it
Again referring to the Super Saloon we run Nitrogen and have done for the last 7 years. It stays a constant temperature and you don't come in with different pressures in the tyres, makes for very easy setting up of the car/ Bike. Use it , they can't stop you. Remember to purge the tyre first though, got to get all that nasty AIR out.
Volty, don;t worry too much about how much tyre you are using on the rear vs front. is as much affected by the shape of the tyre and rim size as anythingelse. Even riding style and tyre weighting can do it. As you wills ee coming out from the above posts, if using air, look at pressure rise, temp, and how the rubber is roughing up. From a personal experience, I'd not be a proponent of nitrogen in bike tyres. Call me conservative, but I like my tyres to get sticky as a result of being warm. Bikes don't load the tyres like cars do, so the needs may well be different and if Nitrogen stops them getting warm, they may well not get teh grip level expecting. If you have an over heating problem, it may well be a way to negate it. But I didn't see that on Sunday. Al
Y'know, specific heat of nitrogen @ 400K is 1.044. Oxygen, 0.941. That's a 10% difference. So a nitrogen filled tyre will run a *little* cooler, but only 10%. Not much of a difference. So, is maybe the perceived effect of nitrogen actually due to the fact that the N2 will be bone dry, whereas the air filled tyre will have a lot of water vapour in there ?
to the fact that the N2 will be bone dry, whereas the air filled tyre will have a lot of water vapour in there That's what I think to Nitrogen wont stop your tyres heating up, it will stop or slow a pressure change as the tyre heats up
... and as motu said air's already got 80% nitrogen so that difference in temperature is even smaller. i really only run nitrogen on the car tyres because they seem to retain the desired presuure setting for much longer than air.
