Ideal geometry for my track set-up.

[pedrosixfour]

Hi peeps.

 

I have some fairly sustantial upgrades to make to my track-only SZ-R over the next 2 weeks, none more important than my new suspension kit.

 

This includes TT spec bilstein coilovers with a Chris Wilson fast road upgrade, including ride height adjustment and a complete polyurethane bush replacement kit for the chassis.

 

To get the most for my new bits I'd like to know what the ideal geometry settings for the front and rear axles might be.

 

Could anyone provide the necessary information?

 

At the moment I have the modest caster and camber available maxed out on the stock front wishbones with some positive results but I'd imagine that doing likewise to the rear camber would not be the ideal solution as rear grip under hard braking is already in short supply with the current settings.

 

I may need a brake bias kit to address this "problem" if more grip cannot be found with the proper geometry but for now I'd just like to ensure that everything is working in the manner it should so any guidance would be greatly appreciated.

 

Regards,

Damien.

[Chris Wilson]

A lot depends on what tyres you are running. A proper DOT legal race tyre like a Pilot Sport Cup needs a lot more front camber than the stock adjusters allow, and it'll stand more castor too. The rears should be OK with the adjustment available on the stock cams. I have to say that you need to be careful where you use poly bushes, in some places the stock MKIV bushes are better.

[pedrosixfour]

Hi Chris, thank you for the input sir.

 

I was aware that you have some reservations about the use of poly bushes as the chassis then ends up being the compliant component instead of the suspension as Toyota intended but I felt that changing one or two bushes for new and then running back and forth to Toyota as the remaining original rubbers gave in to the pressure was a bit pointless.

 

Also, despite my low budget approach to most things in life, the car has a multi-point welded roll cage, based on Wez's fine Andy Robinson example, which runs from the rear suspension to the front of the cabin.

 

As I currently divide my track time between 17" 225/45 & 255/40 R888's, your favourites , and a full set of Bridgestone road tyres, slightly undersized for the car at the moment, 215/45 & 235/40, is it safe to assume that the camber and caster offered by the stock front cams is sufficient or even, dare I say it, appropriate?

 

Should the above prove to be the case what would the complimentary rear settings be? Use all available adjustment or is some moderation needed to maintain a good balance.