SLK tyre sizes
 

Hi
I have an 1997 SLK230 kompressor with 7000 driven miles on the clock. It has the original tyres still fitted but they are all cracking.
So time to replace.

I only use the car in the summer and it’s only local travel
At the moment they are 245/40R17 on the front and 255/45R17 on the rear.
My local tyre garage is having problems sourcing as well as Quik fit. They are coming at me with different numbers and don’t seem to be that sure so I don’t trust their recommendations.
Are their different configurations to the above that are more commonly available?
Thanks in advance for any help.

Tyres or Tires?
 

Seems getting tires for these older vehicles is getting harder and harder :mad: I don't blame you for not feeling very trustworthy of tire shops, my experience would be in agreeance and I try not to rely on others for help in this area.
Former Tire Tech here. Original tires huh? That's pretty impressive - fun fact, in the USA tires that are older than 5 years old can no longer be legally sold, and most companies strongly recommend replacing tires older than 10 years, even if they do not show any signs of aging or damage. No idea what the laws or regulations are anywhere else in the world because hello stupid American :D
To answer your question; My official and formal answer is I would not change the tire size. Mercedes engineers are meticulous when considering any and all parts and aspects of the vehicles they design and manufacture. There's a plethora of reasons to keep the same tire size in order to maintain OEM quality of the vehicle in general.
...
That being said, I understand the sentiment behind wanting to mod or change aspects of my personal vehicle, and the lack of availability of OEM size tires.
You can actually calculate tire sizes for yourself, just gotta manipulate the math a little bit. Let me break it down.

245/40R17
245 Millimeters, 40% Sidewall Ratio, Radial, 17Inch Rim
245 x 40% = 98mm - So the width of the tire is 245mm and the width of the sidewall is 98mm. If you can maintain that sidewall width you could somewhat finagle the tire width size and maybe you won't need any modifications to the body or suspension. For example:
255/40R17 --> 255 x 40% = 102mm sidewall width
265/35R17 --> 265 x 35% = 92.75mm
275/35R17 --> 275 x 35% = 96.25mm
285/30R17 --> 285 x 30% = 99.75
Granted, not changing out rims or using any spacers or not modifying suspension or body in any way will inevitably cause issues like rubbing if you use tires too wide. So despite the fact that a 275/35R17 and 285/30R17 maintains OEM size rim, and pretty close to OEM sidewall width (therefore maintaining close-to-stock ride height), you could still end up hitting suspension parts with the new wider tires.
BUT!
Rear tires you can typically get away with this kind of thing without too much trouble since they don't turn. Referring to your rear 255/45R17 tires, so long as they don't hit anything in its suspension travel you could theoretically put 265/40R17 or 275/40R17 on and might be fine. Please do not forget: despite the fact that both front and rear rims are 17 inches, the rims themselves are likely staggered like the tires. Do not put the rear rims on the front axle, YOU WILL RUB THINGS THE WRONG WAY, LITERALLY.:eek:

Honestly I'm a little biased in my recommendation which is: Bridgestone Potenza is a great product; you can get them in sport/summer or you can get them in runflat versions. Considering you don't drive it often and it is an aged vehicle I would highly recommend runflat tires regardless of what brand you prefer. Every brand will boast a different number but the general understanding is this: If your tire suddenly goes flat and you don't have time or money for a tow truck then on runflat tires you can drive up to 50 miles at 50 miles per hour (or 80km at 80kmh). But I've personally witnessed customers who've driven 70 miles at 70 miles an hour (112km at 112kmh) and when they arrived at the tire shop there was no visible damage to the sidewalls, so we just patched the hole and sent the customer on their way for a cool $25. :cool:

Last thing: if you buy used tires (assumingly because you're desperate) ALWAYS check the DOT number on the sidewall of the tires!!! The last 4 numbers are the only ones that matter for you. The first 2 numbers are the week of the year, and the last two numbers is the year. i.e. 0820 is the 8th week of 2020. see attached picture. Never buy tires older than 5 years.
https://cimg0.ibsrv.net/gimg/mercede...e6aa7d5bfb.jpg
Last 4 digits of DOT number indicates age


Hopefully this information has helped you, and I wish you the best of luck.