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[GTV27]

Am experiencing nasty axle tramp on a hard launch. Traction when on-the-move is very good. Off the line it hooks up fine, except if it breaks into wheelspin, then it tramps quite badly

Car has 200 pound rear springs, koni yellow, SZ dedion bush. Tyres are 205/45 17 Michelin Pilot PP2. Donuts and centre support bush are in good order. Rear gearbox mount was recently replaced (as it was a bit saggy and I thought it was the problem) to no avail.

No other 116 that I know of does this (I've had a 2.0 GTV and Twinspark 75 and they didn't have this problem).

I don't launch it hard because of this problem, which is only a drama for sprints as it probably costs me a second or more on the first lap (and our sprints are cumulative timing for the whole run).

Any ideas what might be going on and how to fix?

[Mats]

Konis -> Bilstein = Bob's your uncle.

The Konis go to the bottom of a lake or similar (you might want to do it more environmentally friendly).

[MD]

Jason
The Bricks got 420lb progressive rate with a suspension travel of around 35mm no rear sway and Koni yellows valved to match the springs. It doesnt have a problem in that regard at least.

Step 1 might be to check the valving on your Konis. If that is OK then I guess changing the nature of the dampers is your next step. I think Mats has a point that it could be a damper issue but then driving with them on at the bottom of a lake is a somewhat drastic line to take..

BTW,I am switching to Bilsteins for the Orange Cab.

[xrad]

wheel hop?
LSD?
Clutch chatter ?

[Typhoon90]

Also check control arm bushes and I guess transaxle bushes. A little extra bump damping can often kill wheelhop too.

Regards, Andrew.

[GTV27]

I think there is a possibility that it is underdamped (although, I don't have any other evidence of that - it has great traction over bumps and doesn't float around?). I could increase the rebound rate to see if that helps. I don't think I have run them above about half (well, maybe, but don't recall if I launched with the dampers screwed up tight? probably not as its not nice)

The watts bushes are standard, but I'd discounted them having an impact...but think they are OK, otherwise I'd be having a lateral load problem, which I'm not.

Don't think the clutch or LSD could cause this. They both seem to be working fine (well, the diff has stock plates, so is a bit soft).

[MALDI]

SZ dedion bush.

Is it freely moving? I have heard that if not installed properly or if not regularly lubed they can bind and cause strange symptoms.

[Mats]

Jason
The Bricks got 420lb progressive rate with a suspension travel of around 35mm no rear sway and Koni yellows valved to match the springs. It doesnt have a problem in that regard at least.

Step 1 might be to check the valving on your Konis. If that is OK then I guess changing the nature of the dampers is your next step. I think Mats has a point that it could be a damper issue but then driving with them on at the bottom of a lake is a somewhat drastic line to take..

BTW,I am switching to Bilsteins for the Orange Cab.

It's referred to as "the lowest line"...

If you have the Konis revalved/shimmed I'm not suprised it works, it's the non-existing bump-damping on the Konis that makes them useless.

[Micke]

I have off the shelf yellow konis.
Whatever Mats says they are not useless.
It might of course be faster with other shocks but the suspension works well. Together with 520 LBS springs I have no problems at all.
My new shocks are another brand and then I'll see what the gain is if any.

[GTV27]

De dion bush is pivoting (right word?) freely (triangle droops and rolls OK without springs and shocks- albeit with some effort as it weighs a ton)

On the shocks, I also had koni yellow on my twinspark and it used to do quite excellent donuts (ahem, purely in the interests of driver training, in a closed course, with an experienced lunatic on board), but it also did have softer variable rate springs (which should still be lurking around somewhere....). As it was too many years ago, I have no idea what rebound setting they were at. As I was young and reckless then, I suspect that they might have been screwed up nice and tight to make the old 75 twitchy enough to match my young and fearless driving style (at that time).

So either the spring or shock rates could account for a difference...a hypothesis pending empiracal research (not likely this weekend as it is raining here at present and it requires a dry surface to be sure).