Grounding rear suspenion

[johnbear]

My suspension keeps grounding.

I've changed the springs 400lbs front 350lbs rear.

She Ok normally, but when fully fuelled up plus some light luggage, she'll ground on the bottom of long sweeping drips at speeds.

I am running AVO's (22 point adjustable) at max, but I am convinced there are too short for the car. Dealer assures me the shocks are the same length (12" - centre to centre on bolt holes) when closed as the standard factory items.

Any ideas?

[gbbird]

When you say grounding do you mean your exhaust keeps grounding on the road? If so, this happens to me too on almost all non perfect roads. I have nitrons, set medium to low.

[johnbear]

The exhaust grounds on the u bolt joints and the rear two boxes have become flattened.

On the lakes tour I was the only car to ground.

[GreenV8S]

It shouldn't run so low that it is in danger of bottoming out in normal use, but it should also have bump stops fitted so that it doesn't bottom out on flat roads even if you do give it a bit of a yump. I'd check the bump stops if I were you.

[johnbear]

This is the bit that pi** me off. I've removed the springs from the AVO's shocks and refitted to check the geometery. The car will ground before the tiny bump stops come into play. I know the orginal shocks have massive bump stops.

These AVO's can't be right.

[GreenV8S]

Not right, but not that unusual either. I've had to fit or replace the bump stops on every single set of aftermarket dampers I've bought, including some from quite well known TVR specialists. They seem to be fitted as an afterthought to protect the insides of the damper from bottoming out rather than correctly sized as an important part of the car suspension.

[trackcar]

Indeedy .. a lot of people miss out the importance of bump stops(or correctly termed spring assisters)
.. I've been building a pair of rear dampers today for a guy with a T350 which is riding on the bump stops and giving an incredibly harsh ride .. the opposite of what you have funnily enough. I've specced a short body tube which in turn restricts the stroke available, but the car wasn't short of droop travel so we could sacrifice some of that to keep the body tube away from the bump stop and still give a low ride height which looks so good on the T350 (the owner isn't a hooner so the trade offs are not high on the priority list here). It's all about juggling the parameters you have to work with to get you the compromise you require (or as close as possible).

Sadly with the AVOs they weld the top eyes onto the damper rod on the normal TVR dampers so there's no scope for adding more bump stops / a single longer stop to the existing damper. AVO might make you a pair up with a longer bump stop though if you ask them

[GreenV8S]

trackcar said:

Sadly with the AVOs they weld the top eyes onto the damper rod on the normal TVR dampers so there's no scope for adding more bump stops / a single longer stop to the existing damper. AVO might make you a pair up with a longer bump stop though if you ask them

I guess you could just space it down with split nylon washers, although it'd be nice to be able to use the extra length to soften the bump stops too.

[trackcar]

I can't help think there's something up with the car .. exhaust/undertray too low .. I used to fit loads of AVOs for people and can't recall having these problems with grounding ..

but the only course of action might be to raise it up for heavy load situations and lower it agin for light loading .. it's adjustable after all

>> Edited by trackcar on Tuesday 30th May 21:03

[the gazman]

Yep
You have mentioned the closed length of 14", what is the open length?
I'm now at 15 3/4" open, centre to centre with a 2" progressive bump stop from Powerflex.
I would also re-visit the ride height and make sure the rear is 10mm ish higher than the front.

[johnbear]

Closed length including a 25 mm length bump stop is 12". Open length is 14.75". I am convinced that the min closed length at full bumpstop compression should be 13".

Rung the dealer again, he's informs me it's a problem that Cerbera's have always sufferred from. Great help!

I am considering buying some new bumpstops from Demon Tweeks, cutting a slit in one side, regluing and tie strapping them on.

It just concerns me at I could lose my exhast at speed.

[GreenV8S]

johnbear said:

I am considering buying some new bumpstops from Demon Tweeks, cutting a slit in one side, regluing and tie strapping them on.

Wouldn't hurt to try, but you'd need some pretty special glue to hold the tension when the car hits the bump stops. I think you'd probably have more success buying/making some nylon C washers and clipping them on the rod under the existing bump stop. If you really want, you can even fit these without removing the springs.

[the gazman]

johnbear said:

Closed length including a 25 mm length bump stop is 12". Open length is 14.75". I am convinced that the min closed length at full bumpstop compression should be 13". Rung the dealer again, he's informs me it's a problem that Cerbera's have always sufferred from. Great help! I am considering buying some new bumpstops from Demon Tweeks, cutting a slit in one side, regluing and tie strapping them on. It just concerns me at I could lose my exhast at speed.

That's around a Chim/Griff length of shock and is 3/4" to 1" too short, its no wonder you are having problems, the original equipment is also 15.50".

[avo]

JOHNBEAR.

NIGEL FROM AVO UK
HOW OLD ARE YOUR UNITS ? SOUNDS LIKE YOU MAY HAVE FRONT UNITS ON THE REAR, OUR REAR UNITS ARE 400MM OPEN AND ALSO HAVE A REMOVABLE TOP EYE SO EXTRA BUMP STOPS CAN BE FITTED !
GIVE ME A CALL ON 01604 708101 AND I WILL BE VERY HAPPY TO TRY AND HELP YOU OUT

REGARDS
NIGEL

[gazzab]

avo said:

JOHNBEAR. NIGEL FROM AVO UK HOW OLD ARE YOUR UNITS ? SOUNDS LIKE YOU MAY HAVE FRONT UNITS ON THE REAR, OUR REAR UNITS ARE 400MM OPEN AND ALSO HAVE A REMOVABLE TOP EYE SO EXTRA BUMP STOPS CAN BE FITTED ! GIVE ME A CALL ON 01604 708101 AND I WILL BE VERY HAPPY TO TRY AND HELP YOU OUT REGARDS NIGEL

I just love the web sometimes!!!!

[johnbear]

Sounds like a deal Nigel. I'll ring you tomorrow.

I purchased the units last june from a TVR dealer in cheshire.

Many Thanks

John





>> Edited by johnbear on Wednesday 31st May 19:51

[ireland]

How did this end up?

I'm in the middle of trying to sort out a bottoming-out problem at the moment, the car is not at all happy on our bad Irish roads.

I've got the AVO's and I'm just about to take them off the car and remove the springs off them and start measuring.

[ireland]

I'm half way through it and I reckon I can only sort half of it.

The back is now sorted, I just wound up the back suspension to give decent road clearance, no problem there.

The front, however, is an entirely different matter.

The front springs are almost compressed fully, one more full turn of the adjuster and there will be no movement at all in them.

Surely this can't be right.

Right now there is about 5mm of travel in the front suspension and after that the sidewalls of the tyres are doing the work.

Do these AVO coil-overs come with the springs on them or are the old springs re-used?

Should a longer spring be used?

Are the front and back springs the same or could they have been mixed up?


At this stage it wouldn't surprise me if they have been mixed up, I've found a lot of things put together arseways on the car.