Track Geo

[J888PRB]

Hi all

 

i have a 420r mainly for track use, looking for pointers on the setup please

ride height, camber and toe. 
 

not worried about road handling

 

thanks

[aerobod - near CYYC]

This is what I did with my R400D: https://www.caterhamlotus7.club/comment/2392485#comment-239248

I also recommend putting in a spherical bearing to replace the A-frame to deDion bush: https://www.caterhamlotus7.club/forum/finally-decided-put-spherical-bearing-dedion-frame-connection

[KnifeySpoony]

Tires? Which springs/dampers do you have? 

[aerobod - near CYYC]

I'm using Nankang AR-1 R-compound 13" tyres in 185/60-13 front and 235/45-13 rear sizes, together with the standard R400 Bilstein adjustable platform sport dampers and springs.

[KnifeySpoony]

Ok now OP"s turn. ;)

[J888PRB]

#3

 

Road tyres as can't be faffed with slicks

currently have 2 sets of wheels. staggered 13's. have 888Rs on one set and ZZS on the other. Looking for next option to replace the ZZS soon for obvious reasons.

have lots of experience in M3 setup but new to the Caterham fraternity, so advice from any track day enthusiast welcomed.

I just want a good track setup for any track legal road tyre.

on ride height....if I go too low does it mess up the caster?? Is there an optimum height to try?
 

standard 2016 springs and bilstein shocks. Spring rates unknown to me.

 

thanks

 

what do the the Caterham race series run? Anyone involved Willing to share.

 

thanks in advance 

[J888PRB]

Thanks #4

You using yours for road or track - are you happy with the nankang setup? I am looking for option to move on from Avon and I'm not overly impressed with the high profiles on the 888R

what camber & toe do you run? 
 

trust realised you were 2 posts - reading your link now 

[aerobod - near CYYC]

Re #7, I was unsure about the Nankangs before I tried them on the recommendation of my tyre specialist over the R888Rs, having previously been using Hoosier slicks on the track and Bridgestone RE-71Rs on the road. Overall they suit the car very well, but I found I had to run a much higher (24 PSI hot) pressure than the 18 PSI hot I ran in the other tyres. I recently just fitted the 3rd set of fronts and I'm halfway through the 2nd set of rears, with probably 2/3  track and 1/3 road use of them.

Synopsis of the Geo I use from the link is:

Camber: -3.0 degrees front, -2.7 degrees rear

Castor: 4.3 degrees

Toe: 0.6 degrees total toe-out front, 0.5 degrees total toe-out rear - car is a lot more stable and much sharper turn-in than I would have thought with these moderately radical settings.

[KnifeySpoony]

I drive mostly track, but still drive to/from the track. My first set of tires were ZZS. I started with 2.25 deg camber up front and the standard 1.5deg de dion ears in rear. Running zero toe up front and 7 deg of caster (to answer your question, ride height does not affect caster angle). Rear is 0.25 deg toe in.  I found that the fronts seemed to wear well edge to edge, but the rears had severe outer wear - not just shoulder wear but a broad angled wear across the tires. Currently running ZZR (A64 compound)-  now have 3.0 deg up front and swapped to the 2.0 deg de dion ears. Overall tire wear looking very good now, even on the rears - I was worried that the ZZR would require even more camber, but it seems not. Some minimal shoulder wear front and rear but no obvious signs of too much/too little camber. 

In terms of ride height I am running quite low, but I have the track rate springs (250F/215R). I set the front ride height to have the lower wishbone parallel with the ground. This puts the ride height at 119mm (giving me about 68mm clearance to ground at the bellhousing). Rear ride height is at 138mm. In order to accomplish this, I had to remove the rear locking collars and the main perch is ran all the way down. Rear ARB is set one hole from stiffest. 

 

Overall the balance is excellent, easily adjustable at any phase of cornering with driver inputs. 

[aerobod - near CYYC]

Re #8, my castor value should be ignored. I initially set it to a "medium" setting which was at 4.3 degrees, but was expecting high steering forces with the high camber and toe-out. After the steering forces were less than expected, I went to maximum castor (4 washers to push lower wishbone forward) and didn't remeasure. The castor is not dependent on ride height as KnifeySpoony mentioned, but is slightly dependent on rake (about 0.25 degree change for every 10mm change in rake).

[7 wonders of the world]

The castor is affected by ride height, since the wishbones operate around individual axis that are not parallel, therefore lowering the ride height has the affect of rotating the upright increasing the positve castor as it does so - you are moving the datum point in the bump castor range.

This may be a negligible amount as I have never measured it fully, but will vary again dependant if you run with or without the lower wishbone spacer too as again the initial datum points will differ.

[J888PRB]

this is all invaluable - thanks for all input.

I will have a play around in the next week or so to make some adjustments and im back on track on the 27th.