FalconChief

My '96 SL500 came with AMG rims. I guess the owner traded with his neighbor (they liked each others rims). The tyres seem to be rubbing on the fender as the fender lip has been bent out when the tyre hits it.

What is the correct tyre size for the 17" AMG rims on a stock SL500?

Are the AMG fenders different? (As in larger)

rojacobs1

Yeah, it looks like you have a lot of meat on those rims.
I have a '96 Sport with AMG rims on them (but a different style) and my tires are pretty low profile. I'm out of town right now and I don't remember the size off the top of my head. I'll be back home on Friday and will post again then if no one comes up with the correct size for you.

ohollenbeck

First off, those wheels are not SL wheels, 17" - 5 spoke wheels of that design were never designed and built for 129's, they are SLK wheels.

Offset or "ET" is almost always overlooked when swapping wheels around from model to model.

ET is a wheel size that very few know about or understand. There are 3 Wheel sizes and all 3 are important for proper fitment. When you add tire sizing on top of the wheel sizing problems, you get problems like your experiencing.

Start with basics - the 3 wheel sizes are width, diameter, and ET. If you look on almost any Mercedes wheel, you will find these three measurement cast into the wheel somewhere, and it will typically look like this;

7 1/2J x 17H2 ET37

The example I have shown is the size you will find on your front wheels, assuming they are a standard set of staggered SLK wheels.

Where everyone understands width and diameter, very few pay attention to ET and fewer still understand it's impact on fitment.

ET describes the placement of the wheel inside the wheel well. High number ET's push the wheel closer to the suspension, where low number ET's locate the wheel closer to the outside of the fender.

There is no universal ET, all cars are designed with there own ET and wheels, many are close and you can swap wheels around easily, but many you can't or shouldn't because of incompatible ET's.

Ever see a jacked up Jeep with the wheels sticking outside the body? That's a very low numbered ET, maybe even a negative numbered ET.

All that being said, 129's are designed for ET's in the 20's to mid 30's, but mostly commonly in the 20's.

Where SLK wheels are more compatible with older E class, having the front wheel with an ET of 37.

Even with the small ET difference in this case, they should not rub unless the tires are way too big.

Tire size for a 17" 129 wheel should be 245/45, which keeps the tire diameter at 25.7 I believe, keeping your speedometer accurate.

Have you pulled one of the wheels off yet to look, I wonder if they put spacers on them, which effectively lower the ET and push the wheel towards the outside of the fender.

7.5 wide 17" ET37 wheels (fronts), should work on a 129 as long as they clear the brakes-suspension, and don't have spacers that are too big.

AMG fender question, in later years there was an option for 18" 5 spoke wheels that look exactly like your wheels, and if you ordered them there was a larger wheel well built to accommodate these 18" wheels. The ET on the 18" 129 5 spoke wheels is 25 front 23 rear, so it's puzzling why your ET 37 wheels are rubbing on the outside of the fender.

But these SLK wheels should work without spacers and with 245/45 tires.

Pull one of the wheels that are rubbing to see if there are spacers, and look on the inside of the wheels for the sizes cast into the wheel.

FalconChief

Very helpful and useful information ohollenbeck! I didn't have time to remove the wheels last night but I did get the tyre size: 235/55R17. I'm guessing this is part of my problem since these would be 1.5" larger in diameter! I'm guessing my speedometer is off as well since there are 43 fewer Revs/Mile.

Looks like a trip to the tyer store is in my future.

Thanx for all the help guys.

ohollenbeck

Yea tire size it is, the 235/55 = 27.2" diameter, which as you noted is 1.5" too big.

The wheel comparator program I use says: this tire size does the following

Wheelwells clearance:
Will fill out the wheelwell by extra 19 mm. Make sure that you have enough room under the fender. If not, consider lower profiles or smaller rims.

SPEEDOMETER:
When speedometer reads 60mph (96.6km/h) actual speed will be 63.5mph (102.2km/h): 5.8% faster.

That speedometer error might get you a ticket if your pushing the limits some..

The rear wheels (if a stock SLK set) are 8.5J x 17H2 ET30, and the tire size for these staggered rears should be the same. Unfortunately 17" wheels don't have enough tire size choices to match 25.7 with a wider tire. So your stuck with 245/45 all around, even though the rear wheels may be 8.5"wide.

If you were putting these wheels on an SLK or 124, you would shoot for an even 25" diameter tire, 25" does work somewhat better for matching wider rear tires.

On an SLK or 124 the tire sizes on these wheels would be 225/45 fronts and 245/40 rears, yielding 25 & 24.7, 17" wheels are tougher to match different tire sizes and get the same overall diameter.

FalconChief

This is an SL not an SLK. Do the same parameters apply?