R129 Suspension Upgrades

[OneTwoNine]

So I've got a 97 SL320 which has been in the family 20 years. Handed down to me by my Granddad. First thing I did when I got it was install Silver Arrow Alberio wheels with P Zero tyres and some 30mm AP springs. But, the car doesn't really feel planted at all. 'Sports Lightweight', not even close. I love the power delivery and how smooth it is but, the handling is piss poor.

Has anyone done any suspension upgrades on their R129 in terms of shocks & springs/coilovers, anti-roll bars, polybushing, adjustable arms etc..? I'm looking to go down the fast road spec setup.

Please don't give me the whole, leave the car standard they've been engineering this way and that, because a car can always be made better and this has been proven time and time again.

I will also be changing the wheels for a wider specification, forged single piece wheel.

All input will be greatly appreciated.

 

[Petrol Pete]

Don't leave the 23 year old car standard if you don't want to , but if you want a sharp handling sports car go out and buy one. no matter what you do to this car it will never be a nimble sports car.

 

[OneTwoNine]

Don't leave the 23 year old car standard if you don't want to , but if you want a sharp handling sports car go out and buy one. no matter what you do to this car it will never be a nimble sports car.

I have a built 205 GTi for the 'sharp handling, nimble car'. I want a car that shouldn't feel like a barge. I'm sure people have done it so I'm just looking to see what everyone has done.

 

[Doodle]

You haven't mentioned any previous maintenance but after 23 years it's more than likely tired. Fitting the springs on original shocks would make the situation worse as you've gone stiffer with tired old dampers that can't contain them.

You're going to struggle to find the ubiquitous "fast road" pack because there's no demand for it, and because of the design of the chassis hardware which means it quickly gets uneconomical to pursue. Freshening it up and making sure it's properly aligned will make a big difference. Put some Bilstein B6s on to better complement the lowering springs, renew the stock bushes (which actually work quite well), fit a new steering damper. You can't fit traditional coilovers because of the spring size and location, and adjustable rear arms aren't easy to achieve without compromising the operation of the multilink rear. ISTR a company called Hedgehog Racing in the far East did some adjustable arms, but rose joints generally don't play nicely with road use. I presume you're not about to drop several thousand pounds on a set of bespoke Penskes or similar.

You also need to recalibrate your brain though. The SL platform is somewhat idiosyncratical, it is designed with far longer wheel travel than your average car, and you sit just ahead the rear axle. The "Sports Lightweight" claim is utter boll*cks as they're nearly 2 tons, but you can pedal them at an fair rate down the road. Just don't expect to do it the same way as most other cars, because that approach doesn't work.

 

[OneTwoNine]

You haven't mentioned any previous maintenance but after 23 years it's more than likely tired. Fitting the springs on original shocks would make the situation worse as you've gone stiffer with tired old dampers that can't contain them.

Freshening it up and making sure it's properly aligned will make a big difference. Put some Bilstein B6s on to better complement the lowering springs, renew the stock bushes (which actually work quite well), put a new steering damper in. You're going to struggle to find the ubiquitous "fast road" pack because there's no demand for it, and because of the design of the chassis hardware. You can't fit proper coilovers because of the spring size and location, and adjustable rear arms aren't easy to achieve without compromising the operation of the multilink rear.

You also need to recalibrate your brain though. The SL platform is somewhat idiosyncratical, it is designed with far longer wheel travel than your average car, and you sit just ahead the rear axle. The "Sports Lightweight" claim is utter boll*cks as they're nearly 2 tons, but you can pedal them at an fair rate down the road. Just don't expect to do it the same way as most other cars, because that approach doesn't work.

Cars done 31k miles from new. It had a full refresh on control arms and bushes where possible when I got it with brand new KYB shocks all round.

You can convert the car to true coilovers, Yellow Racing, Ceika both do true coilover conversions but, also offer the seperate adjustable springs and shocks which have adjustable length and adjustable spring perches. Thats along with Silver Project Adjustable rear upper control arms and camber adjustable front top mounts.

Whats the need for a new steering damper when theres no play in the rack..?

 

[Capa]

What about throwing some AMG bits at it; do any fit? Might keep the character of the car whilst offering more sporty handling?

Failing that. Yeah I guess you're down to doing what you say - throwing coilys and some polybushes at it.

On the other side of things. I have the Benz as something to barge about in in all its wallowy glory - and the caged 205 for when I want to go tossing round backroads. Works well I find.

 

[Doodle]

You can convert the car to true coilovers, Yellow Racing, Ceika both do true coilover conversions but, also offer the seperate adjustable springs and shocks which have adjustable length and adjustable spring perches. Thats along with Silver Project Adjustable rear upper control arms and camber adjustable front top mounts.

I've seen plenty of traditional coilover setups advertised, few in use. The area where the top of the shock mounts is not designed to bear the load of the car, only locate the top of the shock. Unless you're going to weld this up, it will bend. I've seen the results first hand when people have tried. You can fit adjustable spring perches, sort of - to do it properly you have to start modifying metalwork. Are you willing to go that far? Don't forget the 129 already has some modicum of height adjustment through the spring pads.

Whats the need for a new steering damper when theres no play in the rack..?

There's no rack on a 129. It's a steering box, and 3 tie rods.

I suggest you go and do some research and understand what you're working with on this car, and what the purpose of that damper is. But what do I know, I've only spent nearly 2 decades doing this. Good luck with your endeavours.

 

[Doodle]

What about throwing some AMG bits at it; do any fit? Might keep the character of the car whilst offering more sporty handling?

There's not many "AMG bits" on the 129 chassis, and what did exist is now rarer than a rare thing. There was a spring and damper kit available for those cars that didn't have ADS, but you'd achieve the same with decent lowering springs and B6s. ISTR there were anti roll bars available, I'd need to look at my files again.

 

[BTB 500]

There was a spring and damper kit available for those cars that didn't have ADS

I guess that's the £1900 "AMG Sports Suspension" option for the 280/320/500/SL60 (the 600 had standard ADS of course) on my 1997 price list ?? Bit mean not to include it on the SL60!

 

[alabbasi]

The SL is not a sports car, it's a GT car which means that it's better suited for motorway blasts than for twisty roads. You'll never get the handling that you're going to get from your GTI in the SL because the SL has something that your GTI does not have and that's weight, which is everything.

Renewing the suspension (all bushings , shocks etc) will likely improve the quality of the ride and handling by an order of magnitude, but it's not going to turn it into a sports car.

 

[Deleted member 149005]

The SL is a GT/ touring car, not a sports car....

(Silver) Arrows go well in a straight line but tend not to go round corners unless they hit something....

 

[BTB 500]

ADS helps a lot. Still a 2-tonne car though.

 

[Deleted member 149005]

Was ADS available on the 320 in 1997?

 

[BTB 500]

Was ADS available on the 320 in 1997?

Yes it was an option on all R129s apart from the 600 (which had it as standard). Even the SL60 AMG.