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suspension bracket position
angliamotorsport - 15/1/11 at 10:15 AM

Hi all, a question for the suspension wizards.

I have a bare locost chassis and have some gts challenger bodywork and want to sprint and hillclimb the finished car.

My question is; if I want to run a 50mm ride height should I, (a) position the wishbone brackets 50mm higher up the chassis to keep the wishbones faily level, or should I (b) wind down the spring seats and have the wishbones at a steeper angle.

My first thought would be to choose (a).

I realise that by choosing (a) I would have to redo the front part of the chassis (make it slightly narrower) to retain the correct pivot points, ie top mount, steering arm ball and bottom mount.

An comments or if anyone has done this before I'd like to hear from you.

Thanks


big_wasa - 15/1/11 at 10:31 AM

Dont mess with the front Geo' Take a look at pics of the 750 race cars and procomps LA gold All run very low to the ground and from what I have seen mount the bones as per book but tweek them for anti dive ect.

If you run 13" rims with a 60 profile the car will be lower than you think..


I love the gts challenger bodywork, are you going to be able to replace it if you bump it ?


Theshed - 15/1/11 at 10:51 AM

If you use option (b) but use standard rolling radius wheels and tyres you will have radically altered the existing geometry. That may be a good thing or truly awful! Option (a) will preserve the geometry which again may be a good or a bad thing once you introduce some aerodynamic downforce unknown to the original design.

There is a lot to be said for reducing the rolling radius of the tyres as a means of lowering the ride height but you may need to change the gearing to compensate.


MikeRJ - 15/1/11 at 11:37 AM

If you wind down the spring seats you will be operating near the top of the dampers stroke so will have very limited suspension travel before you hit the bump stop. This is a bad idea and will make the car much more twitchy on bumps.


minitici - 15/1/11 at 12:16 PM

Move the suspension pick-up points higher in the chassis to maintain suspension geometry.


interestedparty - 15/1/11 at 01:08 PM

My question would be to ask whether 50mm ground clearance would be enough in all the circumstance you are likely to encounter, and whether the extra spring stiffness needed would have any unforeseen effects on the handling. Not saying it would, mind, just asking.


angliamotorsport - 15/1/11 at 04:44 PM

Thanks for the input guys, I think I will take the following path,

Draw out full size, pickup points, suspension brackets, chassis, section thro', wishbones, uprights and wheel/tyre combination, that should give me an idea of what is going to happen, sorry all you young guys out there using cad, I'm old, so drawing works for me.

I want to run a low ride height as the original car did not have any aero apart from being a slippy shape.
My idea being to have a one piece floor and using the natural curves at the front and real of the bodywork to produce the shape of the underside of a wing and perhaps introduce end plates at suitable places if not too obvious.

As far as springs go, I run a small single seater with 300lb front and 450lb rear, wings front and rear and other bits. Ride height is 50mm front 70mm rear and my bum is still in one piece, ( too much info).

Please do comment.

Regards


interestedparty - 15/1/11 at 05:54 PM

quote:
Originally posted by angliamotorsport

As far as springs go, I run a small single seater with 300lb front and 450lb rear, wings front and rear and other bits. Ride height is 50mm front 70mm rear and my bum is still in one piece, ( too much info).

Please do comment.



How stiff the effective springing is depends on the angles that the springs are in relation to the up/down movement of the wheel, so the spring rates you've quoted don't really mean very much on their own.