Wheel Sizes/Ride/Comfort on R231 SL 350

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New Member
Nov 27, 2014
R231 SL 350
I have now had my R231 SL 350 for 9 months and still loving it (pic in SL register some months back) so - a question to those more knowledgable than me re wheel size and tyre combinations please.

Car currently has 19 inch wheels with 285/30/19 on the rear and 255/35/19 on the front - Continentals on reccommended pressures - now about half worn.

The ride is great on smooth roads but pretty hard and bumpy on lesser roads and the increasing number of potholes are not helping - in fact I suspect they have contributed to a bit of expensive MOT work to the nearside front suspension. I big pothole unseen can give quite a bang despite best efforts to miss the worst.

Could I improve on the hard ride with different 19 inch tyres ? any reccommendations ?

Would I be better with 18 or even 17 inch wheels and corresponding deeper profile tyres given that I prioritise comfort and wear and tear over outright performance - if so do I really have to have different front and rear ?( this issue and offset etc bit of a dark art to me ) might it affect speedo reading albeit the total overall diameter of wheel and tyre might be the same? would I suffer much on handling ?

I guess I might also need to mention to insurer too if going down this route although I thing more than one wheel size is 'standard'

many thanks
The rear tyre size limits your options if you want a matchng set. Simply there are so few vehicles using 285/30/19 that not many manufacturers offer them in the UK market.

I eventually went with Pilot Super Sports which are available in MO specification actually designed for the SL65.

The reality is will all SL's running the same wheel sizes anything under the SL63 is pretty much overtyred.
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You can find official wheel size options here so it looks like you can go as small as 17" if you want.

You'll see the "usual" wheel size and specifications on the tyre pressure chart on the car.

17 is comfiest of comfy, but 18 is more common.
This is what I went for for my R230:-


Prices will undoubtedly risen since I purchased these.

(Cough) You'll find 18's for less than a grand on Ebay but usually with brand new or near new winter tyres.

And you'll have no difficulty selling your 19's to someone wanting an upgrade from 18's. (Could this be an arbitrage opportunity?)

Importing wheels from Germany is a whole different thread.....

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On my wifes 2005 r230 I changed the wheels from 17s to 18" AMGs purely for the looks and I was shocked how much it negatively affected the ride. (Bye the way, Goodyear as3/4/5s would be my choice of tyre on 19s. Had them on the cls55 and they were a significant improvement over the Contis in terms of comfort.) Back to the SL and my wife is just changing the r230 for a newer one and we have specifically sought out one with 17s to get the most comfort. Cant comment on difference yet as its not been delivered. Larger wheels look better and usually come in nicer designs but for everyday driving, without her pants on fire, we are hoping the 17s will waft her along.
UK R231s never came with 17" wheels. Only 18" and 19".

you could order 19"/20" on AMGs.

how old are the tyres? How many miles? I found that at 20k miles, the ride deteriorated noticeably even though there was around 4mm thread left. new tyres, and it became lovely, firm and smooth again.

for me, the ride on my SL is better than a W213 E class loan car I had with 20" wheels.

I find the R231 quite sensitive to tyre pressure.

I put in/remove air using the on board TPMS readings. As soon as readings are available, I remember the readings and then after the journey add or remove air .. to get to 2.1 bar front and 2.3 bar rear cold.
17s on an SL look a bit small but will give the best comfort. 18s will be much better than the 19s comfort wise too and give the wheel and suspension more protection. 18s would be the best compromise in my opinion. Dumped my 19s off my A207 for the exact same reason.
Thank you all very much - plenty of helpful comments and information. It is tempting to go for 17's - but as others have said maybe the best compromise would be 18's. The tyre pressure info in the fuel flap reads for 17's - all the same - or 18's staggered, or 19's staggered - my 19's are staggered. Pardon my ignorance here but 'must' I have staggered ? MB seem to see it as de rigueur - and I get the reasons - but I use the car much more a as GT - with the odd burst for overtake or occasional quick take off so would prefer same all round as long as there are no problems in doing so.

If I did go for same 18's all round would I go for 18x8 with 35 offset or 18x8 .5 and TYRES - 225/40/R18s or 255/40/R18'S -

car was designed to run with staggered wheels/tyres. I would not meddle with that .. may affect ride, handling, assist systems

may also invalidate your insurance as not using correctly dimensioned wheels/tyres
If it helps, the only wheels listed for the R231 350SL are 19" (code 770 as std fit, code 785 or 662 as options) with the tyre sizes as quoted by you. There are no 18", or 17" for that matter, listed as either standard fit or optional.

This information is taken from a UK-market 2013 brochure. 19/20" wheels were optional on the SL63 and SL65.

Of course, it's possible that smaller wheels were available in other markets, or for use with winter tyres (to allow for the fitment of snow chains). Are 17" or 18" listed in the handbook?
I would always advise insurers of anything that might be construed as a deviation from standard specification, and would recommend that everyone do likewise.

The modifications sheets for my MGB GT V8 run to 3 or 4 pages of A4 - insurers have never been concerned as performance enhancements have been balanced with uprated suspension, brakes, wheels & tyres.

Stick with standard spec. Anything else runs a risk and brings potential insurance wobbles. If the designer thought it was the right thing to do, it’s the right thing to do.

There will be plenty of wheel sets out there looking for new homes.

As for using your SL as a GT: join the family. It’s what these cars are used for. A few exceptions around, maybe, but really it’s all Bobby Ewing territory. Just watch how they’re actually driven in the real world.
Thank you all again - to summarise - lots of useful info -

on alternative make of 19's,

Tyre pressure sensitivity - couple of psi lower than mine on front - interesting

Tyre wear - they are almost/pretty much half worn - not sure of age as they were on the car when I got it

Apparantly UK 231 350's only came with 19's - again interesting as tyre pressue chart in car petrol flap quotes pressures for 17's , 18's staggered, and 19's staggered.

Consensus seems to be stick with staggered, and some consensus on sticking with stock for good reasons.

Advise insurer - I did actually put this in my initial post that I would do that - I just wanted to do as much homework before approaching them on what is recommended - what acceptable alternatives if any there are - according to MB - UK and worldwide - in order to give them some context.

The 231 does seem to come up with different wheel sizes on a generic search - 18 inch comes up most often - but this is wordwide. It feels I need something definitive from MB - but the insurer will be the final arbiter.

If I got something definitive from MB on say 18's- and insurer was happy with that - then that could be a go. If not then it will be stick with the 19's - try Goodyear next time - and in the meantime try softening the front by a couple of psi.

Much of the time the 19's are fine on decent roads- its the crap roads and the potholes that really show them up- back in the winter I hit a new one on the M4 I didnt notice and the bang was unbelievable even at about 65mph - possibly the cause of my recent MOT work on NS suspension.

Just a quick update for reference - MB Bristol on looking up my car offered from the data that 18's OK staggered - but not 17's.

According to them - Rear 8x9.5 ET 47.5 with 285/35/18's Front 18x8.5 ET 35.5 with 255/40/18's

So will see what is available and if right ones are then check with insurer.

Thanks again.
Mine's a late facelift r230 where the 17s were still the base fitment....wheels just get bigger and bigger and tyres thinner and thinner
Apparantly UK 231 350's only came with 19's - again interesting as tyre pressue chart in car petrol flap quotes pressures for 17's , 18's staggered, and 19's staggered.

As you say interesting. I was in France a few weeks ago in my R230 talking about wheels & tyres with a French friend who had an R231 which was on staggered 18". He had been told by a French dealer that he couldn't fit 17" wheels. He said he thought that advices was b***ocks and that at the end of the Summer he was going to fit unstaggered 17".
If you have the Sport Pack on the R231 - very common in the UK - with the large front brake callipers, 17" wheels may not fit.

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