Trackday - setup, pressures..

[upsidedownmark]

First trackday in the caterham coming up - done plenty in more normal road type cars. Not afraid to push..

It's an ex academy roadsport, cr500's on 13x6. Fixed front ARB, adjustable rear. Tyre pressures are about 22 on road. Allegedly has a reasonable setup, but I've put an LSD in it since.

So.. where should I expect to be / start with tyre pressures? Don't have a round-pin C spanner, so I think I'm stuck with the ride height.. hopefully there's no big imbalance and the ARB can fine-tune..

[DCL]

Firstly I wouldn't become obsessed with tyre pressures, but I would aim to start with what you are used to - 22 psi hot, perhaps 2 psi lower on the front. I suspect best grip will be well below that, so once you comfortable with the car on track you can play around to find what suits you. Remember the balance can related to tyre pressures too.

[Steve Campbell]

Whilst we are on this theme....I always started with CR500's 18 cold and worked from there (think they usually ended up around 21 or 22 hot)

Now on ZZS's .... should I use the same ? I heard somewhere that optimum for those is a bit higher ? Comments ?

[fergus]

consider unbolting (and zip tie-ing out of the way) the rear anti roll bar drop link until you get used to the car moving around.

[Tazio77]

The road pressures you are using at 22psi is far too much....general consensus and starting point is 16psi....and on track aim for 20 psi hot

[Amris]

Different tyres have different optimal temperatures. I find ZZR's run best at 22 hot, ZZS's around 24 hot (both in the dry). Play around with it thought and see what suits you best. I take a mini compressor to track days and check pressures before and after each session. Its amazing how much they fluctuate both between hot and cold and wheel to wheel. Can speak for CR500 as have never run them. In the wet you can pump them right up to 30-35psi to get the best traction.

[upsidedownmark]

Thanks folks.

Was expecting 22 cold to be too much, but coming from 'normal' cars mid teens seems scary low!

I'm actually doing the 'how fast' in the morning so chasing a laptime, smart plan for the first time out in the car .. but at the risk of sounding like an arse I tend to be able to get a handle on these things pretty quickly. More concerned it's going to understeer having put an LSD in it since it was set up... let's see!

[Amris]

Assume you are doing Bedford, so can always adjust the rear torsion bar too if the under-steer is giving you issues. Fairly quick job you can do on the track side and completely changes the way the car handles.

[rubystone]

Amris said:

Assume you are doing Bedford, so can always adjust the rear torsion bar too if the under-steer is giving you issues. Fairly quick job you can do on the track side and completely changes the way the car handles.

I'm guessing you mean the anti-rollbar? I'd not play with that..and certainly not by the 'trackside'

I'd recommend 18 all round, but see how hot they are after a few laps.

[radical78]

16 to17 psi cold

[upsidedownmark]

Finished up at about 24 hot all round by my dodgy cheap gauge, so could have been anything. Probably needed less.

Perhaps predictably made a complete horlicks of it, overdrove left right and centre. First few laps were very oversteery, took some air out and moved the rear bar to full soft (from middle), that made a huge difference, quite nicely balanced. Of course being a complete numpty, I spun on the penultimate corner of my first 'counting' lap, thereby runing that, AND making sure I started the second one slow. Hey ho.. over ambitious really, but on the bright side, I had an hour and a half of sharing West with ONE other car, which was pretty special.

Spent the rest of the afternoon on SEN doing the regular trackday, had a lot of fun, and started to smooth things out. My braking still needs a lot of work, but had awesome fun, can't ask more than that..

Edited by upsidedownmark on Saturday 1st July 19:47

[Skyedriver]

Interesting as we were discussing this at Harewood Hillclimb today.
It was my first time driving the Caterham after 15 years of other vehicles, I was running Toyo R888R at 18lb and just trying to establish gears and braking points but-
Guy next to me with Avon slicks was on about 12lb but mucking around every run, checking temperatures across the tyres.
Guy next to him was on soft compound 888R not the R888R and was also playing with pressures, his preference was 26 but he'd been told by the ex Class Record Holder (no longer in this class) that 28 was the optimum. He was finding 24 gave better grip but slower speeds and vice versa.

[sundance002]

I run 14 psi front 16 psi rear. cold
CR500. I find that gives me the best grip on a hot day. I also run 2psi harder on fron right and rear right depending which circuit im at. sometimes the opposite