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Author: Subject: Change springs or try ARB
Nitrogeno25

posted on 10/11/14 at 03:33 PM Reply With Quote
Change springs or try ARB

Last week I installed a new set of Protech 400 (single valve) in my car. Springs are 300lbs at the front and 175lbs. at the back.

Yesterday I tested it in a circuit and the tail is, although predictable, very happy. I can't apply power until the car is completely straight.

In tight turns in 2nd I get lots of wheel spin with some nice spins

Now, I plan going to 350lbs at the front, that seems the easier but I can go the ARB route with I like to reduce roll.

What should I do?

Many thanks!

cheers

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mookaloid

posted on 10/11/14 at 03:45 PM Reply With Quote
That's a huge question

I think we would need to know a whole lot more about your set up before we could answer that.

just for starters:

It could just be tyres or tyre pressures causing this. Suspension geometry, or even too much power

do you have a limited slip diff?

what sort of car?





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britishtrident

posted on 10/11/14 at 03:55 PM Reply With Quote
A front anti-roll bar is fairly easy to make up, if you go this way the arb needs to be fairly soft by road car standards, try 13mm dia for starters.
On the other hand springs are fairly cheap but you might have to try a few sets.





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rodgling

posted on 10/11/14 at 04:32 PM Reply With Quote
Interested in the answer to this as I'm in a similar boat (car). Mine rolls a lot on 450/300 lb springs front/rear - the result is a slightly wallowy-feeling car and I suspect an ARB would improve this. I've tried going stiffer on springs but found that the car starts to lose grip more than it improves roll behaviour. Handling otherwise seems OK though.

Ride height could be a factor, if you can lower it you'll get less roll. Has the car been properly set up (and shocks adjusted properly)?

Pictures of your car mid-corner might help us get an idea of how much its rolling.

[Edited on 10/11/14 by rodgling]

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Phil.J

posted on 10/11/14 at 05:52 PM Reply With Quote
Does the geometry of the suspension allow you to put preload on the front springs? ie zero droop. If so, try putting about 100 lb preload per side ie 1/3"up. on the spring platforms on the front.
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britishtrident

posted on 10/11/14 at 07:16 PM Reply With Quote
quote:
Originally posted by rodgling
Interested in the answer to this as I'm in a similar boat (car). Mine rolls a lot on 450/300 lb springs front/rear - the result is a slightly wallowy-feeling car and I suspect an ARB would improve this. I've tried going stiffer on springs but found that the car starts to lose grip more than it improves roll behaviour. Handling otherwise seems OK though.

Ride height could be a factor, if you can lower it you'll get less roll. Has the car been properly set up (and shocks adjusted properly)?

Pictures of your car mid-corner might help us get an idea of how much its rolling.

[Edited on 10/11/14 by rodgling]



It sounds like your roll centres are very low. The geometry in the books is a bit iffy. A lot of people following the book and looking at pictures of F1 cars end up building with ground level roll centres. A ground level roll centre will increase the amount of roll particularly if the cg is a bit high.


To take an extreme examples the original Range Rover had a cg and soft springs, the roll was kept under control by designing the suspension to have high roll centres. An F1 car has a very low cg and because of the aero loads very stiff springs and so can use a ground level roll centre.

Classic 1960s & 70s Lotus models used a front roll centre about halfway between the bottom of the chassis and the ground.

This link http://lotuselan.files.wordpress.com/2010/03/lotusfrontsuspension0162.jpg shows the front suspension of the Baby Elan note how the front top wish bones are inclined slightly downwards from the wheel end. The angle of the top wishbone is what essentially defines the roll centre height. Link to full site http://lotuselan.wordpress.com/elan-in-depth/

[Edited on 10/11/14 by britishtrident]





[I] What use our work, Bennet, if we cannot care for those we love? .
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Camber Dave

posted on 11/11/14 at 08:42 AM Reply With Quote
I would add to the confusion - Rear dampers too short.
Sound like it is unloading the inside rear wheel.

I also vote for a front ARB. Try 22mm O/D 3mm wall tube and flat levers
Depending on lever length and drop link position, it's worth about 160 Lb of weight transfer
and a similar amount of roll resistance as the 300 lb springs.

This could cut the roll by 1 deg and retain more weight on the inside rear.

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procomp

posted on 11/11/14 at 02:11 PM Reply With Quote
Hi. You dont add an anti rollbar in to the equation untill the handling is already sorted. That's the big mistake most make.

Yo do not use an anti rollbar to stop the car rolling you use it to fine tune the weight transfer.

The one very basic question is what is the valving ratio on the dampers being used ?. If you don't know the answer to that your just guessing. 99% of dampers supplied by manufacturers have basic saloon car valving IE far too stiff in compression and no where near enough rebound to control the very basic problem that is being discussed.

Adding a front ARB to cure the problem at the rear is a backwards step.
Cheers Matt

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Nitrogeno25

posted on 11/11/14 at 02:32 PM Reply With Quote
quote:
Originally posted by procomp
Hi. You dont add an anti rollbar in to the equation untill the handling is already sorted. That's the big mistake most make.

Yo do not use an anti rollbar to stop the car rolling you use it to fine tune the weight transfer.

The one very basic question is what is the valving ratio on the dampers being used ?. If you don't know the answer to that your just guessing. 99% of dampers supplied by manufacturers have basic saloon car valving IE far too stiff in compression and no where near enough rebound to control the very basic problem that is being discussed.

Adding a front ARB to cure the problem at the rear is a backwards step.
Cheers Matt


Thank you very much!

I bought them directly from Protech (we were in touch before as I really want you to supply the shocks, but I'm in America and need to import them).

Wheels: 185/60 14 R888 at 18psi cold. No LSD.

The car is a Lotus S3 replica (not the best from suspension geometry point of view) with a 2L Duratec. The new shocks alone really make the car very comfortable. I tested 7 clicks rear, 9 front.

Then, I increased the front to 12 clicks and 6 click rear but the situation did not seem to change, althought the car feel better at the track with more damping.

Car weights 588Kg but weight distribution is 45/55 (F/R). With me It is almost 40/60, that should not help the situation.

I really appreciate everybody opinions.

Cheers

[Edited on 11/11/14 by Nitrogeno25]

[Edited on 11/11/14 by Nitrogeno25]

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Nitrogeno25

posted on 11/11/14 at 10:56 PM Reply With Quote
And a picture of the car!



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