Question Regarding Chassis Stiffness.

[ManwithSupra]

It was just a passing question really, if you have a standard Supra (liftback model i.e not aero top) and have stiffened the suspension, added stiffer anti roll bars and harder bushes, would you need to increase the torsional stiffness of the chassis in order to get the best out of it?

[Chris Wilson]

Yes, ideally, because nearly all road cars are as floppy as a paper bag. Example, jack a Porsche 928 up on the front jacking point and the door won't open and shut properly. And Porsche made a play about how stiff they were None Aerotop JZA80's are not TOO bad, stiffness wise, but for any serious track work a weld in roll cage will transform them. Aerotop models are dreadful, chassis stiffnes wise, as you might expect. I think the only road car with really good published chassis stiffness is a McLaren F1 or whatever they're called. The old Austin 1800's / 2200's were very good, surprisingly, probably by luck rather than design, knowing BL at the time

[ManwithSupra]

Yes, ideally, because nearly all road cars are as floppy as a paper bag. Example, jack a Porsche 928 up on the front jacking point and the door won't open and shut properly. And Porsche made a play about how stiff they were None Aerotop JZA80's are not TOO bad, stiffness wise, but for any serious track work a weld in roll cage will transform them. Aerotop models are dreadful, chassis stiffnes wise, as you might expect. I think the only road car with really good published chassis stiffness is a McLaren F1 or whatever they're called. The old Austin 1800's / 2200's were very good, surprisingly, probably by luck rather than design, knowing BL at the time

 

Fantastic thats just the answer i was looking for thanks Chris Aside from the weld in roll cage (won't be getting one just yet but later ) are there any other things you can do in the meantime to stiffen up the chassis on a Non-Areo top JZA80?

[Chris Wilson]

Not really, the commercially available spring top front tie bars (strut bars or whatever the people call them) do sod all and are really just for show, as they are neither of large enough diameter or section, and are not triangulated back to the bulkhead. You can get the roll cage people to make you a proper one when they do the cage. You could make some solid subframe mounts to get all the compliance out of the rear frame, and diff mounts. You could remake the engine and gearbox mounts and rubbers and solid mount the engine and box, and use the engine as a semi stressed member, but it's a LOT of work, and hellish noisy when done. A cage will make all the difference. Bolt in ones don't do much from a rigidity point of view as the bolts move in their clearance holes. Welded in is the way to go with full triangulation.

[ManwithSupra]

Cheers Chris.

Can you or do know of any reputable fabricators that will do the welded roll cage and front welded tie bars??

[Chris Wilson]

Speak to Wes, he was very happy with the people I recommended to him. You will find some pics of his cage on this forum somewhere.

[ManwithSupra]

Cheers chris