Tyre pressure debate

[flymo]

Almost all racers I've compared info with are running near enough the same pressures, even across different tyres and bikes.

Front is normally 30psi and rear is 29psi when cold (I confirmed mine with a BSB Pirelli tyre technician, a drinking buddy of mine). The important point is the target temperature that they reach during your race or track session. Other than outside influence such as ambient air temp and track surface temp you can influence it most by the style and speed of your riding.

It all depends on the length of the track session and your ability. The harder you ride the faster your pressures and tyre temperature will rise.

I wish I had tyres that looked that good after a race!

I usually run about 30/30 on my GSXR (standard = 36/42) and get river patterns like here, though most of the time worse.

Yesterday I ran 32/38 at anglesey. I've never had grip problems with fully warm tyres so I can't really assess the effects. This is what my brand new pirelli corsa III:


The surface has been ripped away, another 2/3 trackdays and the tyre would be squared off around that wear mark. The only other difference I could visually see was that the tyre picked up less rubber on the edges for both front/rear.

Larger river patterns, small river patterns ... why are small ones better than large ones? Are smaller ones really indicating less wear? Which have given the better grip/feel on track? Surely that is more important than any wear pattern?

Now this one has always got me ... do you pump them up a bit more or let them down a bit if it is colder?!!?

Oh and BTW my view on the 'focused heating' is sceptical. Lets face it, that guy is a paid tyre technician, but it is contrary to the logic I am about to present (which was originally given to me by a paid tyre technician ).

Flex a bit of rubber (or metal, or plastic) in your hands ... it doesn't take long before it gets hot. Its this property that actually aids heating the tyre across its width, the bit that flexes the most will provide the most heat (the same centre spot).

About to watch motoGP on telly so this is a bit brief, but will discuss/elaborate more later if anyone is interested!

[flymo]

Originally Posted by Zombie Jesus

I usually run about 30/30 on my GSXR (standard = 36/42) and get river patterns like here, though most of the time worse.

Yesterday I ran 32/38 at anglesey. I've never had grip problems with fully warm tyres so I can't really assess the effects. This is what my brand new pirelli corsa III:


The surface has been ripped away, another 2/3 trackdays and the tyre would be squared off around that wear mark. The only other difference I could visually see was that the tyre picked up less rubber on the edges for both front/rear.

I think you were closer to the mark with the original 30/30 although you may want to try a lower rear pressure to start with....say 29psi and see how you get on.

Other than pressures the other thing you might want to think over is the suspension setup as that can also affect tyre wear. I race Anglesey regularly and have never had tyre tear like you are showing.

Hanging of would give you more traction, which may save you from a future crash. Never know how close to the edge you are until you slide. Best to have all the traction you can get just in case.

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!

I've got Diablo Rossos on my bike. Pirelli's UK Product Manager told me not to change the pressures at all and the tyre man told me to go quite low even though I said I was a novice. I've tried both and I settle somewhere in between. 33/33 or maybe a tiny bit lower instead of 34/36. Last trackday I got me knee down and the tyre to the edge with no wobbly moments. Had no rip on the right side but thick wobbly lines of snot on the left (mallory park) which I assume is cold wall rip (?).

The debate goes on.....

Edit: As a side not I mentioned to someone queing to go out on an Aprilia 250 that it looked like he had oil on his rear tyre. Patches of purple and other colours. He said it was just where they'd got hot!

Interesting thread. I did a track day a couple of weeks ago and was having issues with tyre grip running a Diablo Rosso on the front and a Diablo on the rear both at 29psi. I did another trackday yesterday and tried running them at 33psi front and 36psi rear and they seemed to me to perform at least as well as at the lower pressures. I didn't have any significant slides this time, but I think I probably wasn't pushing it quite as hard as last time, doing a better job of staying within the tyres' limits. I think the tyre wear looks less, unfortunately I didn't take photos of them after running them at 29psi, but here's some from yesterday after running them at 33psi and 36psi:
http://s38.photobucket.com/albums/e1.../sv650s/tyres/

Is the discussion in this tread is a bit bum about face?

Discussing cold tyre pressures is largely irrelevent when it's the hot pressure that matters, which is why racers use hot pressures to adjust their tyres.

Every rider, tyre set and suspension set up being different, Surely the advise should be to set your cold pressures so that we *all* have the same hot pressures regardless of set-up/bike/ability/power/rider weight.

Tyre pressures should be measured when coming back in from a track session, or when just finishing a spirited ride.

Sending a novice out on 29psi tyres front and rear is not a good idea simply because the tyres are underinflated. If that novice never gets to a point where his tyres are "hot", he'll be running on tyres that will be squirming all over the place due to deformation from the low pressure.

Rather than saying you should set your cold pressures to XYZ, we need a figure to set them to hot, measure them hot and adjust them hot. The point at which they run is the important measurement and as we all ride differently, we should, in theory, be all starting from a different starting point to reach the *same* end point.

So if we all want to end up with a hot pressure of say 36 front, 38 rear, some will start at 29, some will start at 32 and some may start as high as 34-35.

And tyre pressures are only half the story, Maybe even less than half.
Properly adjusted suspension is more important in terms of feel and keeping the tyre on the road. Having the rear too stiff will cause the bike to push on the exit and will increase the temperature. It may cause the rear to skip under power and increase temperature and wear.

So, is it not the case that this thread should be about "which hot pressures should we all be looking for so we can all set our cold pressures to suit our own particular circumstance"?

Cheers,
Carl

[Viney]

Its quite simple, you do what works for you. One mans meat and all that.

I have never done a track day, but i can notice a 2psi drop in either tyre on my bike and its horrible.

I've never track ridden an SV, but I have a Hornet and then a Daytona 675.
Tyre pressures (for me mind-high intermediate speeds) are set to aim for around 35psi front and rear when HOT, and i mean HOT!
I normally start a track day at around 31-32 and then adjst them after the first session as soon as i come off track.
This has worked for me, I'm hard on the brakes so kepe the front very hot. I've been known to outbrake a Blade at the end of Park despite having 100bhp less for the long drag!
I've used both Bridgestone and Pirelli track focused road tyres. 012ss and supercorsa sc2's. As well road tyres, 010's on both the Hornet and 675.
So i agree with what has been said, lowering tyre pressures is what people do and it does work.
I believe lowering the pressure allows the tyre to move around more at first but this will ultimately heat the tyre up faster, increasing the pressure higher, quicker.
HTH
J