Tyre pressure debate

[lukemillar]

Ok, I'd be interested to hear peoples thoughts on this. I have done somewhere between 15 and 20 trackdays and have always dropped my (road) tyre pressures down a few psi - Usually run something like 28-30psi front adn 30-32psi rear. Today I went to a new track and was noticing that my tyres felt good at the beginning of the session but started to slide towards the end. A few guys in the pits said they were running around 34-36 front and rear which I thought was way to high, so I went and quizzed to the Bridgestone guy who was giving out this advice.

He said that running lower tyre pressures gives a larger footprint on the track. I agreed. However, he then said that the larger footprint doesn't generate enough heat or the heat is to dispersed across the tyre so they don't get up to their correct working temperature. This causes small level cold tearing (the 'large' river like patterns - usually in the spot where you get on the gas). He said if you run the same pressures as on the road - maybe 1-2 psi either way depending on preference. Then the tyres footprint is smaller and the heat generated is much more focused, which is how the tyres are designed to work and offer the optimum grip. He then went on to say that you know that you tyres are getting up to temp because the river like patterns are much much smaller - that is the sweet spot.

I tried this out and for the first few laps, they felt awful. I was sliding all over the place - one corner, I could feel the whole bike drifting sideways as I exited. However, after a few warming laps, they actually felt better than before?

So, what is correct??

(remember this only applies to road tyres - not race tyres)

Neither and both I'd hazard. Which felt best to you over the whole session?

Without knowing which tyres, taking temperatures, knowing the manufacturers optimum temperature range, and a whole host of other factors (left/right circuit, speed of corners) it's all about what feels best to you. Think about how much they spend developing tyres and how a given brand can be hated by one rider and adored by another.

I havent done 20 trackdays, but have done a few. I never adjust my front tyre. Just leave it at road pressures, currently 32 / 33. I do drop my rear down to about 30 / 31 though.

This was from advice from Dunlop rep at CSS Rockingham. I also picked the brain of a well respected team owner in BSB 600 Supersport.

So far it has been good advice

I've done less than 10 track days and all of them at Knockhill and I've not once adjusted my tyre pressures. I never thought I was 'racery' enough to notice a difference. I may look into this next time.

[Skip]

I have a track evening at Snetterton tonight - usually just drop the pressures by 2-3 - I have found this ok at the 6-7 trackdays I have done. For the Zed that means 34 front and 39 rear I think...

[fastdruid]

I've done some 15 or so trackdays and I've tried at std pressures and dropping a few PSI, at standard pressures the tyres begin to feel squirmy towards the end of a session. Dropping about 3 PSI and they feel odd for the first lap then feel great.

I thought that the idea was to run at about the std recomended pressures but that the pressure will rise in the tyre as the tyre warms so will end up wth a higher pressure than it would on the road for the same cold pressure. So you drop it a few PSI to end up with the same 'hot' pressure.

One way I've heard but never tried is to set the pressures hot, ie *straight* after you get off track, that should allow you to change the pressure relative to how hot the tyre is getting. Probably best to start with to just measure it and note it down, comparing it to cold pressures so that you get an idea of what's going on before you start making changes.

Druid

chap i was speaking to at the weekend reccons i should drop my tyre pressures on the road to about 36rear and 33 front.... am not convinced....

Not sure what bike/tyre combo you're on Custard, but a lot of the tyre manufacturers and Suzuki recommend 33F/36R on the SV for general use.

[lukemillar]

Originally Posted by simesb

Without knowing which tyres, taking temperatures, knowing the manufacturers optimum temperature range, and a whole host of other factors (left/right circuit, speed of corners) it's all about what feels best to you. Think about how much they spend developing tyres and how a given brand can be hated by one rider and adored by another.

The tyre manufacturer is largely irrelevant - the question was more the theory of lower pressure = bigger footprint, more dispersed heat, means tyres aren't getting up to optimum temperature.

Bridgestone man said road tyres are designed to work at ~70c - so after a session on the track, although your tyres may look torn up, and feel warm, they actually were operating at a lower temp, which is why you get the large river patterns - because the tyre is tearing (mildly) away from the track surface. With a little more heat, there is less tearing and more grip! I'll post some pics of the big and small river patterns from my rear when I get a chance

It's interesting that someone quoted a Dunlop guy at Rockingham saying almost the same thing. I think on my next trackday, I'll probably keep my front as is and just drop the rear a little - see how that works out.

I find this really interesting. Someone else also suggested taking pressures readings the second you get off track - to see the cold/warm difference and gauge how much of an increase hot tyres gives. Mine were ,at most 2-3psi higher, but that was it.

[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!