hillclimb tyre pressure advice

[Stuwey]

and swap on a pair of semi fronts when its dry.

Nooooo!

Even grip all the way round the car, please. Be it high or low, you want the back of the car to grip the same as the front!

[kaanage]

Again, total agreement with Stuwey - putting the semis on the front and leaving the street tyres on the rear will turn you around as soon as you think about lifting off mid turn. I once scrubbed in a single A048R on a rear rim and it TOTALLY screwed the handling of the PoD, making the car understeer in a diabolical way and turning in very strangely as the car would seem pivot about that tyre - it was weird enough that a Polo GTi driver following me on that cruise commented on how odd the car looked in the turns.

But they let go very suddenly in the wet and don't tell you they are about to in the way that the street tyres had thats for sure. Its just a question of keep them on and hope it doesn't rain or get the RE003's on and hope it will!

This!

If I do get the RE003's put on whats the quickest way to scrub off the greasy new top layer. Will a quick flog on a favourite stretch have them ready?

Street tyres (any tyres really, except GP 125 slicks) seem to scrub in almost immediately IME once you lean on them a bit so about 4 corners into a decent fang on a dry road should do it, I would think.

[sambb]

I know I know I agree. For the street I'd be putting on another set of dunlop sport maxx R/T fronts to keep it all the same if I could but they are discontinuing in that size and they are now over $220 a tyre. Thats why RE003 is in the picture.
As for the AD08R's on the front that was really just an experiment to see how much of the dull polo steering and poor forward traction under power was tyre related (the dunlops have a really soft sidewall) or if I'd need to throw money and effort at steering rack rebushing/big geometry chgange etc. In all honesty I just don't have the coin to go to a seperate set of semis all round anyway.
I do understand the risks re lift off oversteer. The track is very tight and outright speeds don't get very high (its all second gear really) so spots where a mid corner lift could get me out of shape are few. There's none of that high speed building high g's stuff that does give you the heebies if you chicken out. If you watch the vid there is a down hill section at the end that could definitely be a lift off risk though. Being uphill too and front drive the only time i'll really get oversteer is corner entry on lift/brake but at those low speeds my rear dunlops are ssoooo progressive so I back myself. Through a similar uphill stretch where I like to go locally, I've got to be literally trying to loop it to get it to step out going uphill. If it s wet on the day though, that will be a different matter if I still have the AD08R's on for sure though. You're absolutely right .....its a calculated risk.

here's the course:
https://www.youtube.com/watch?v=OWiAUokdU-c

here's where the risk will be:
https://www.youtube.com/watch?v=lO351ek0Q4k (at 1:30)

[sambb]

Well the event is done. It was such an unreal spectacle. I'm not sure about how the track days go down but the hillclimb had such an amazing carnival atmosphere. There was everything from formula vees, dallaras, lolas, penskes, right down to my humble little shopping cart. The most insane class was formula libre. Almost all of them were hyabusa powered missiles, supercharged, turbo charged etc.
M. Oastler (the nsw champ) did it in 33.95. To but that in perspective thats 10 seconds quicker than an improved production 200SX around a course that is 720m long - mental! The guy has worked for mclaren and BAR apparently so figures. Me - my best was 47.17. All I really cared about was that I improved on each run which I did (except for the first run after lunch when the tyres cooled right off and front pressures in the AD08R's got down to 29psi).
For me the times were better when I had 33psi in the fronts. Lower and I had trouble turning it in without it pushing and poorer steering feedback. Higher and I couldn't get traction on corner exit. The rears more or less stayed fixed at 33 ish psi. During the event today it took about 45 mins for everyone to cycle through so the tyres had a chance to cool for each run. On saturday practice though unbelievably (to me) one 48 sec run would add nearly a psi to the fronts. When I had the chance to do 3 sort back to back runs the car got less and less traction under power (even though they were getting sticky) and I couldn't believe the fronts were nearly 36psi when I parked it. You guys that do sustained laps/track days must have to dump so much air to keep the pressures where you want them.
How do you guys launch the car? I tell you what traction control sucks a##se. In the end the best thing I found was to hold the clutch at the bite point with the handbrake on and 2000rpm for an unmolested launch. Did anyone ever find out, is it just brake force modulation that shuts things down or is there a boost cut too because it felt like it? - woeful. The way a datsun 1200 coupe with a sidedrafted SR20 launched... now that had me pining for my escort back!

[kaanage]

That sounds like you had a fun day out

I suspected that you needed some pressure in the fronts to start with since you start from cold in a hill climb (missed by 1 psi, though :p). With track sessions, I basically start with pressures low enough to get the tyres to 32-34psi when they are fully warmed (when EVERYTHING you run over sticks to them) which rarely takes more than the out lap as I basically build speed over the course of the lap, feeling the grip increase with each corner.

With track days, you get timed on flying laps so launching isn't a requirement - a good thing for me since the PoD is such a slug.

I do understand the risks re lift off oversteer. The track is very tight and outright speeds don't get very high (its all second gear really) so spots where a mid corner lift could get me out of shape are few. There's none of that high speed building high g's stuff that does give you the heebies if you chicken out.

The guys setting really quick times don't build corner speed - they turn in pretty much on the limit which is why some element of stability is required so can go in a touch hot without instantly flying off the track. I'm not sure I could commit that much on a hill climb - I'll find out someday, I guess.

[sambb]

Speaking of hillclimb commitment, it really blew me away how dangerous it is for the really fast guys. I mean apart from solid barriers on some corners, what really got me was the top section where they would be maxed out in third (450kg cars and turbo'd hyabusa motors) with trees either side. I mean there is no runoff at all - they will basically die.
The serious guys were rubbing down their slicks and black plastic wrapping them after each run and they'd arrive at the line with the plastic on the tyres and unwrap them just before going into the burnout area. Keeping heat in and the surface perfectly clean I suppose.
Well now that my front advans are basically on the inicators, next time (which will hopefully be Matara/king edward park) they will go on the back and i'll get a fresh pair for the front (so that i'll have a matched set all round) just as soon as I find someone who doesn't need an OEM ET43 rim and wants to sell it on and help out my cause. Anyone out there got one? change to a space saver spare (they're lighter!) and sell me yours.