Hi Phil,

I noticed in the "WRX engines" discussion you mention that you run the various cars you use on Michelin slicks. Various people here have asserted that the grip levels with full slicks are too much for standard road car shells, and that they will suffer structural problems unless they are seam welded.

As you are running cars on the track, day-in day-out, you must be in a fairly good position to verify this. Is it a real concern, or is it just BS? Do you happen to know if all your cars have been seam welded to avoid problems?

TIA

-= mike =-

Hi Mike - I'm posting this to your e-mail too (just in case you don't pick this up for a while).

This is my honest oppinon. Basically if I was running an Impreza with either standard or even slightly uprated suspension - I'd be more than happy to use slicks on trackdays.

If you were constantly on the track with big spring rates and track geometry (i.e. wild track and camber adjustment) then in time you will fatigue the shell around it's weak points - normally around the suspension pick-ups and the bulkhead.

Back in the real world however doing half a dozen track days won't hurt the car.

As for the Palmer cars - no they are just standard WRX STI V.5's. I don't know if they come seam-welded as standard but they haven't done anything to them - they don't even have cage's in them!

Professor Nunan,

Thanx for asking me about slicks and Palmers cars, I work there too you know!!

I agree with what Phil says, a few track days here and there won't make TOO much of a difference, although over a few years of using them it will weaken the shell.

Remember, with slicks you are capable of generating up to 60% more grip, and this does have to go somewhere. Cars generally don't come factory strengthened on the seams for two reasons;

1st - it can make the car too harsh on the public highway.

2nd - it doesn't need it!

It's not only the suspension that determines the handling of the car, the basic bodyshell structure can have a major influence on how it all handles as well. The suspension not only has to get the car arond the corner, it has to be able to control the twisting of the shell as well. If a manufacturer made a super stiff shell, it would handle great on the track, but could be uncomfortable on the road. As far as I can tell, the Impreza's shell is fairly stiff for a road car anyway.

Also as a referance to balance the argument, look at the Lotus Elise. That has a very stiff alloy tub, a bit like a racing car. The tub provides the body control, allowing the suspension to do it's job better. The Elise suspension is very soft if you press down on the car; you can almost bottom it out! But go over a small bump at 10-15 mph in one and you will knock your fillings out! This is due to designing a very stiff 'bodyshell', but then again the car is very light.

Rob.

Sorry, Rob, I'd kinda forgotten that you were working there too! Didn't mean to offend, and TVM for all the extra info.

-= mike =-

No problemo http://bbs.scoobynet.co.uk/wink.gif

Rob.