my 340 is bouncy at the front, coilovers used

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seannaayy
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my 340 is bouncy at the front, coilovers used

Post by seannaayy » 05 Jan 2013 02:58 pm

I found the walkthrough on here on how to make your own coilies, using mk2 golf coilovers. i had a mk2 scirocco knocking about with coilovers, and with them being basically the same car, i used those however its very bouncy under uneven terrain?

im just wondering wether i can improve it somehow? maybe upping the spring rate? (i think its 350lbs?) or maybe the damping?

or should i just accept the ride as it is as i run it pretty low and the geometry of the car is all over the place? it also has modified subaru adjustable topmounts and i run quite a bit of negative camber with a bit of added caster, could this have an effect?

cheers for any help :) p.s. its a 1.7 340 340pw

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Chris_C
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Re: my 340 is bouncy at the front, coilovers used

Post by Chris_C » 05 Jan 2013 04:55 pm

Just because something physically fits, doesn't mean it's a good idea. I've no idea on the corner weights of a mk2 golf/scirroco, I'd imagine it's almost similar to a 300 though so you should be with a fighting chance I'd have thought, unlike some of the random car choices people seem to have used.

What way does it feel bouncy? Over sprung and under damped to me is the scariest form of driving, it does feel "bouncy". However, with the amount of work you've done, I'd be thinking about how much everything else has moved and been affected. Have you had the car on a proper alignment machine since to see how symmetric it all is, and to compare to the original book values?
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
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'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

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mac
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Re: my 340 is bouncy at the front, coilovers used

Post by mac » 05 Jan 2013 05:14 pm

In any suspension system the spring rating and damper characteristics should be carefully matched to the expected force input during use. The main factors to take into account are weight (both sprung and unstrung) and the vehicle use.

At the end of the it's all about balance. Using a system designed for a very different vehicle can have unpredictable consequences as you have found. In any vehicle the suspension is there simply to ensure that the tyre remains firmly in contact with the surface at all times (driver comfort is a by product).

If your car is as you describe "bouncy" it would suggest that spring rebound is poorly controlled, most likely because of weak rebound damper characteristics due either to mismatch or wear. Even if the coilovers you are using stated life as a matched system, and are unworn, they are no longer fitted to the designed application - there is no guarantee they are still matched. If you increase the spring rate you will make things worse. If you feel the compression damping is OK then you need to increase the rebound damping only.

Running an increased camber-caster won't directly effect spring/damper performance but playing around with caster especially can have an enormous effect on steering response, turn in, self centering, weight, etc. adjust with great care - you may find it unpredictable. With too much caster you can get a situation where a vibration can turn into an uncontrollable "wobble" and loss of control!.

Mac.
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classicswede
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Re: my 340 is bouncy at the front, coilovers used

Post by classicswede » 05 Jan 2013 10:57 pm

This has been pretty well covered in the responses already. It does sound like the rebound on the dampers is not upto the job. Are the dampers adjustable?

I would also suggest you get tracking and caster camber angles dialed in right. Also if you have it sitting to low (much less than 3" lower) then you will have problems with the angle of teh bottom arm.
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seannaayy
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Re: my 340 is bouncy at the front, coilovers used

Post by seannaayy » 20 Jan 2013 03:59 pm

Thanks for the indepth replies guys!

i also figured it would be the damping rate, (didnt nessecarily realise it could be the rebound rate though, doh!) yeah i know its not wise to *bodge* products from other cars but as i had a seperate set of struts and coilovers from a similar (in my opinion) weighted car, so to save me 500 odd quid id figured id have a go haha and dont worry im more than capable of doing this sort of fabrication work, is it possible to buy different damper inserts?

and no these dampers arent adjustable unfortunately, will a different weight oil n the damper help?
also ive not had the tracking set professionally as it seems pretty good (doesnt wander on the road or wobble etc) i know this could still mean its way out but im a tight arse and if something seems ok ill begrudge spending 40 quid on something that wont make a difference :P

so im thinking, adjustable damper insert available to buy? or more viscous oil inside?

thanks again guys :)

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Re: my 340 is bouncy at the front, coilovers used

Post by classicswede » 20 Jan 2013 10:09 pm

Mk2 golfs should be well covered with dampers. Do a search on ebay and have a look around on the golf forums.
Dai

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seannaayy
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Re: my 340 is bouncy at the front, coilovers used

Post by seannaayy » 22 Jan 2013 12:04 am

ok cool, cheers for the reply, would you agree its probably under damped then? anyway i can find out what its rated at, at the moment? will it be stamped somewhere on the damper tube?

thanks again

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