Excessive R230 SL road noise from rear - what's yours like??

[martin_sv]

Could the new rear shocks have been fitted incorrectly?
( To any who have driven, worked on or just know about r230 rear suspension partic. SL 350 ie non ABC modell)

Hi to you all,
Sorry about my long post.
I'm generaly very pleased with the refinement of my 2003 350Sl 2003. I've only done about a thousand miles so not too much experience particularly as most done with the roof down. In this state I can hear the rear tyres but at a level that seems perfectly acceptable ie mostly drowned out by wind noise. However with the roof up it's another story. With music on again it's drowned out but now I've got over the novelty of the high quality sounds emanting from the bose system I'm moving back to wanting (relative) silence. Those rear tyres Pirelli p zero rosso's really spoil the show. I always thought my previous drive an alfa 156's weak point was toad noise, ( both front & rear) but this is definitely noisier. It's clearly the dominant sound at motorway speeds .
Front tyres seem very quiet in comparison. The tyres have appx 6mm equally worn across the treads so I'm just wondering whether the rear shocks have been replace incorrectly. Last owner had plenty of kit including full hydraulic lift and seemed pretty clued up. He had replaced the front control arm and ball joint -seems fine. The car was given a full geometry check after the shocks were fitted. The thing that sticks in my mind is the bill he gave me from Robinson Merc dealer of Peterborough for .£114 to "fit spigs on shock absorbers" Not come across this before but have found them on the parts diagrams., seem to be some sort of top cap to the shocker itself. Is it possible for these or indeed the whole shocker to be replaced incorrectly eg rubber bushing/ washers in wrong order perhaps? Any help greatly appreciated as I dont want to be forced to listen to music or radio 4 whenever I'm on the motorway!! :neutral:

 

[television]

I do not think the suspension can have anything to do with road noise, the tyres that you have I found them to be very noisy once ½ way through their life on my SL500

 

[martin_sv]

I do not think the suspension can have anything to do with road noise, the tyres that you have I found them to be very noisy once ½ way through their life on my SL500

Interesting - I'm a bit suprised at just 2mm of wear though and also that the fronts although same brand seem very quiet. There's a piece of coarser surface road I drive along regularly in my other car a late model alfa 156 where the change in the level of road noise is really noticeible particularly from the front tyres. In the case of the SL there's hardly any change at all. So it seems that I have noisy rears whatever the road surface. ( I tell a lie on some m ways where they've put that nice black looking tarmac compound the back end quietens down a fair bit, but that's the exception)

Regarding supension effects. I thought is was well established that as well as being important for appropriate suspension component location via its' stiffness the exact choice of rubber /synthetic compound for suspension bushes is a key component in reducing noise / vibration and harshness. Often becoming something of a trade off between the two design objectives. This was the root of my question in that I felt perhaps something was amiss in the suspensions' rubber joints with the recently replaced shockers ( not done by a professional) being a possible line to examine. Do you know what the top caps "spigs" on the shock absorbers do?

 

[Gkinghorn]

I would echo what Malcolm says having taking possession of his car with those p-zeros on them. The fronts were incredibly noisy but fortunately needed replacing and the new tyres are whisper quiet. The rear are not as worn , maybe halfway thru their life I would guess or just over , and whilst not overly noisy they are noticeable.

I would put money on it being the tyres ...


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[television]

One has to remember that in the SL the boot area is not sealed off as on a normal saloon, so they will be noisier, one would have to drive it before you could tell if it is noisier than it should be.

I think the suspension bushes would have to be very hard before any noise is transmitted into the car, but incorrect part or assembly could possibly cause it

these are the rear shocks

 

[martin_sv]

I would put money on it being the tyres ...

I may have to consider biting the bullett! Can I ask what make/model of tyr you replaced the p zeros' with?


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Television or Malcolm I believe.... ( I've read so many of your helful contributions)

One has to remember that in the SL the boot area is not sealed off as on a normal saloon, so they will be noisier, one would have to drive it before you could tell if it is noisier than it should be.

I think that's perhaps the nub of it, I need to do some comparisons, --anyone around Hampshire/Berkshire with a sl350 (non ABC model) prepared to take me for a short ride on a fast road /dual carriageway? I'd be more than happy to reciprocate??

 

[Mic]

Gordon put Syron tyres on his car.

Dunlop Sport Maxx GT are well rated for quietness.

www.tyres-pneus-online.co.uk

I am still minded to go for the Continental SC 5's because I think wet grip is everything.

Mic

 

[television]

I have the Dunlop sport on my CL and they are quite good re noise, the interesting thing is that the roads over here are much noisier than those in Germany or Sweden

 

[drmw]

I had P Zero Rosso on both the SL500 & the SL55 - took them close to the legal limit & can't say I noticed excessive noise.

My attention was drawn to the OP's opening comment - "Last owner had plenty of kit including full hydraulic lift " - now, I have no idea what that is, but it does imply (backed up by the odd "repair" description) that someone has been messing about, perhaps where they shouldn't have.

If, for the sake of simplicity, there are incorrect or missing bushes ("spigots"? "springs"?) then personally I would be looking for a second opinion on the setup before splashing out on new rubber !

 

[martin_sv]

Thanks for all your responses and comments.
I think I have 2 courses of action to pursue. Firstly to see if i can get a ride in another SL preferably a 350 without ABC -- I'm open to all offers and can travel! This will allow me to check out how mine compares in respect of road noise and should mine seem significantly worse subsequently to then get it up on a ramp with a tech who can visually inspect the rear end and report anything not as it should be.
In the mean time today I took it for a spin after stuffing some old pillows in the boot near the roof folding mechanism ( where there are quite significant gaps allowing noise to travel between the boot and the cabin) and it did seem to offer some improvement. Still bad though. Am I wrong in expecting it to have less road noise than a similar muileage (80k) Alfa 156?

 

[television]

You could have a noisy wheel bearing

 

[Mic]

Thanks for all your responses and comments.
I think I have 2 courses of action to pursue. Firstly to see if i can get a ride in another SL preferably a 350 without ABC -- I'm open to all offers and can travel! This will allow me to check out how mine compares in respect of road noise and should mine seem significantly worse subsequently to then get it up on a ramp with a tech who can visually inspect the rear end and report anything not as it should be.
In the mean time today I took it for a spin after stuffing some old pillows in the boot near the roof folding mechanism ( where there are quite significant gaps allowing noise to travel between the boot and the cabin) and it did seem to offer some improvement. Still bad though. Am I wrong in expecting it to have less road noise than a similar muileage (80k) Alfa 156?

If you are prepaed to travel a good lump try Carnut 13

Mic

 

[Gkinghorn]

Never driven an Alfa 156..does it not rattle?

I can only get the Syron race 1's for the front though on the sizes i have fitted..the rears will need to be something else when they go... either Falken (favourite) or Conti's I suspect...(Unless syron release a new tyre by the time I need to replace)

Maybe this guy will let you try his ?

http://forums.mercedesclub.org.uk/showthread.php?t=107551

 

[drmw]

Thanks for all your responses and comments.
I think I have 2 courses of action to pursue. Firstly to see if i can get a ride in another SL preferably a 350 without ABC -- I'm open to all offers and can travel! This will allow me to check out how mine compares in respect of road noise and should mine seem significantly worse subsequently to then get it up on a ramp with a tech who can visually inspect the rear end and report anything not as it should be.
In the mean time today I took it for a spin after stuffing some old pillows in the boot near the roof folding mechanism ( where there are quite significant gaps allowing noise to travel between the boot and the cabin) and it did seem to offer some improvement. Still bad though. Am I wrong in expecting it to have less road noise than a similar muileage (80k) Alfa 156?

Don't know the Alfa, but it shouldn't be loud enough for you to feel there's something wrong, so comparative makes a lot of sense - trouble is, if the other one is quieter but has different tyres, you'll not know where the difference lies

 

[BurgerDave]

I have an SL350, non ABC and live in Kent. You're welcome to come and listen etc. However, I am 100% certain it will be your tyres from my own experience. When I got my car it was fitted with Michelin Pilot Sports (the originals) and it was very quiet considering the factors you've mentioned about insulation from the boot etc. When I replaced the rears about a year ago, the garage convinced me that the original pilot sports were no longer available and to fit pilot sport 3's... This turned out to be complete nonsense and obviously based on what they had in stock but the point is they ruined the car!!!! For some reason, on some of the quietest roads in the world (Germany) they whine like the clappers. You'd swear the rear diff or a wheel bearing was about to explode, but it isn't. It is 100% the tyres. As for Pirelli P Zero's, I had them fitted on an XJ8 I had and it is a fact they go noisy once they start to wear. They produce anything from a whine to a rumbling noise depending probably on the car and suspension set up etc. as well as other factors.

 

[television]

I have an SL350, non ABC and live in Kent. You're welcome to come and listen etc. However, I am 100% certain it will be your tyres from my own experience. When I got my car it was fitted with Michelin Pilot Sports (the originals) and it was very quiet considering the factors you've mentioned about insulation from the boot etc. When I replaced the rears about a year ago, the garage convinced me that the original pilot sports were no longer available and to fit pilot sport 3's... This turned out to be complete nonsense and obviously based on what they had in stock but the point is they ruined the car!!!! For some reason, on some of the quietest roads in the world (Germany) they whine like the clappers. You'd swear the rear diff or a wheel bearing was about to explode, but it isn't. It is 100% the tyres. As for Pirelli P Zero's, I had them fitted on an XJ8 I had and it is a fact they go noisy once they start to wear. They produce anything from a whine to a rumbling noise depending probably on the car and suspension set up etc. as well as other factors.

Thanks Dave and exactly my findings on all those

 

[martin_sv]

I have an SL350, non ABC and live in Kent. You're welcome to come and listen etc. However, I am 100% certain it will be your tyres from my own experience. ..........
As for Pirelli P Zero's, I had them fitted on an XJ8 I had and it is a fact they go noisy once they start to wear. They produce anything from a whine to a rumbling noise depending probably on the car and suspension set up etc. as well as other factors.

Thanks for this BurgerDave it does seem that the tyres seem to be getting the most votes as the source of the problem. I would describe it as similar to the tyre roar I've heard on many vehicles but just more of it!! A continouous rumble would certainly not be a bad alternative description.
Whereabouts in Kent would that be? Although now based north of Basingstoke I'm a londoner originally and in my very early driving years ie 17yrs old with a purple ford anglia into which like many I installed the cortina GT engine. Many drives out with gang would end up either with the well known "Grand Prix de Kingston Bypass" with the good old sidcup bypass a close second. Those were the days!!

 

[BurgerDave]

I'm out near Sittingbourne, but grew up in my early years much nearer to the two wonderful race tracks you mention Unfortunately both would now be named speed camera alley - they spoil all the fun eh? If you do get this way you'd be very welcome to a drive in my SL to see how it compares.

 

[martin_sv]

I'm out near Sittingbourne, but grew up in my early years much nearer to the two wonderful race tracks you mention Unfortunately both would now be named speed camera alley - they spoil all the fun eh? If you do get this way you'd be very welcome to a drive in my SL to see how it compares.

Yes, a lot of the pleasure has certainly been taken away. In fact one of the reasons I chose the SL was that it could provide that lovely wafty driving pleasure without feeling the need to unleash all the performance to have some fun. I've found it meets those needs very well indeed.
Thanks again for the offer, Sittingbourne being a bit if a hike (100mls) I'd like to try and kill two birds at the same time. If you don't mind perhaps you could P.M me a contact number so when I know I'm going to be around the M25 I could give you a bell in advance to see whether we could work something out? ( I don't have sufficient posts as yet to PM you). I'd also like to ask about your throttle booster you have fitted as I'm not a fan at all of the "adaptive throttle profile" programmed in as standard.

 

[Doug1234]

Have a look at the tyres sidewalls and check if they have a 'direction of rotation' arrow, if they do are they fitted the correctly as fitted the wrong way round they will make a lot more noise.