I've been wanting to go with aftermarket wheels (possibly Mandrus) and I noticed they are available in 17 & 18" with what seems like a perfect width (1/2" wider front and back), the correct offset and they're hub centric.

Mandrus 23 wheels:
17 x 8", 32+ offset, 5x112 bolt pattern, 66.56 hub bore.
18 x 9.5", 25+ offset, 5x112 bolt pattern, 66.56 hub bore.

Im running 235/40-18 and 275/35-19 tires (on the factory rims) now, and in 17 / 18 diameter, just going up to 45 /40 in the aspect ratio keeps the same relative tire width and diameter, while increasing the sidewall height approx 1/2".

I wanted to try this to get a little more of a compliant ride, and lessen the chance of getting bent rims... my stock rims HAD bends in them, which I had repaired, and now they've got bends in them again... life in N.Y.

One of my concerns is clearance of the brakes and other assorted parts on the car with 17" fronts and 18" rears.

Is anyone running (or tried running) 17" front and 18" rear wheels on an SRT6?
Thanks in advance!!
Nikko

 

Nikko
The 2004 SLK32 had 17" wheels from the factory (regular SLK's were equipped with 16" rims), and the brakes are a little larger, as well as the rotors and it would appear there are no issues with fitment on the SLK.
The 45/40 aspect ratios should be compared to the original tire sizes on the 2004 SLK32 before you make a selection. You should consider the side view look of the Crossfire, with the gaps created by the smaller wheel, so you may want to go to a 55/60 aspect ratio to "fill up" the wheel wells, to make the look much better.
I'm betting the SLK's had a taller aspect, for a better ride, those buyers would never consider a Crossfire, due to the stiff ride attributed to the higher rate springs and low aspect tires.
Google the 2004 MB SLK32 for the tire info, it should help in your decision making with your potential wheel/tire combo.
Dennis
DTMenace

 

Thanks for that info and advice Dennis!! Im gonna check that out.

 

Nikko
Here's a site for wheel and tire sizes for an 2004 Mercedes Benz SLK32. The info is listed about 1/3 from the top of the page.
Dennis
DTMenace

https://www.wheel-size.com/

 

Nikko, I'm running 18x8.5, 19x9.5 Mandrus Rotec rims on my SRT-6 with the stock tire sizes.

The 225/40-18 tires on the front are really stretched on that 8.5" wide rim. I'm not sure what the widest tire that will fit on the front before rubbing, 245? 255 maybe?
255 isn't wide enough on the 9.5" rears but there's more room to go wider.

If you get the Mandrus rims you'll need different lug bolts, stock won't work. There's a thread about it here on the forum. https://www.crossfireforum.org/forum...arly-pics.html

Something I've noticed is that my car rides much smoother when the temp gets over 85. Below that the tires won't get warm enough to eliminate the flat spots from sitting. Does it get that hot where you are?

You also might consider using a SL rated tire instead of an XL to soften the ride.

 

I run 245-35 on the front with a spacer and have no issues but I think a 255 would have issues.

 

Is that on the stock rims? That's about as wide as I thought without rubbing. That 20MM would almost make up the extra inch of width on the Mandrus rims.

Stock rims:
Front 7.5x18 ET +35mm 225/40-18
Rear 9x19 ET +22mm 255/35-19


Mandrus rims
18x8.5 ET +32mm
19x9.5 ET +25mm

 

Correct, 245/35 is the widest you can go on the front w/o rubbing, and that needs to be on <32mm offset. So, +35mm offset might actually allow for some rubbing.

I stuck with the 225/40 on mine and had no issues. Flat-spotting is very common on high-performance summer tires, especially if you allow them to get cold in the same spot after aggressive driving.

I would stick with XL load rating. SL is mathematically fine but the confidence in the tire suffers because they have a higher tendency to "squirm" under cornering loads.

Continental has a new tire out which has been getting VERY good feedback on the Mercedes forums:

https://www.tirerack.com/tires/tires...re=735YR9ECSXL

VERY reasonable too.

 

Actually, just the last two days have been above 85 in New York, but I havent had the car out the last two days (Im having Dave at LED Fix replace the 3rd brakelight LED's, so the car is in the "hospital" right now, haha!!).
Anyway, it just seems to have a very harsh ride with the tires on there now (235/40-18 & 275/35-19 Conti DW's on factory rims).

Thats why I have been thinking of going down in diameter to 17" ft / 18" rr. The tires critical measurements (diameter, circumference and width) are essentially the same as I have now if I use 235/45-17 and 275/40-18 tires, but both tires will have nearly 1/2" more sidewall.

Current 18" front--235/40-18--(25.40" diameter--79.80" circumference--9.25" wide)--3.70" sidewall
Mandrus 17" front--235/45-17--(25.33" diameter--79.57" circumference--9.25" wide)--4.16" sidewall (+.46")

Current 19" rear--275/35-19--(26.58" diameter--83.50" circumference--10.83" wide)--3.79" sidewall
Mandrus 18" rear--275/40-18--(26.66" diameter--83.76" circumference--10.83" wide)--4.33" sidewall (+.54")

Plus the 17" / 18" Mandrus 23's are both 1/2" wider than the stock rims (8"w front / 9.5"w rear)
That combination SOUNDS like it will work.

Just as a side note, with the factory rims and the 235/275 tires, I WAS using 10mm front and 15mm rear spacers (Eibach hub-centric). The idea of using spacers just kept bugging me for some reason (even though the car looked great with them). Anyway, I ended up taking them back out. Now the car is "narrower" again, but Im sleeping better at night.

Car has stock springs, except I swapped out the "four nub" spacers in the rear for "one nub" spacers to level the car out.

PS-Im not gonna be re-installing the Eibach wheel spacers, so if anyones interested, PM me. They're essentially in new condition, with the Eibach bolts, still in the Eibach box. I dont think they were in there for more than 20 miles.
I paid $279 + shipping for the set of 4 spacers. I'd sell them for half that, $140 including shipping (within the Continental U.S. only) if anyones interested.
If not, they'll make a unique set of super duty drink coasters .

Thanks for all the info!!
Nikko

 

That sounds like it will all work well and the overall diameters are bang-on.

You will definitely have more compliance over the potholes, so that's a plus. I'd keep the PSI near 35 to compensate for the added sidewall, but you will love the stability that comes from the width.

 

I checked the tire pressure today and found it a little high, within a pound of 40psi on all tires. I saw the sticker on the door jamb says 36psi is recommended, so I lowered it to 36psi.
I was thinking of setting it at 34psi, but I wonder if that might be a bit low for tires with 35 & 40 aspect ratios.
The Conti DW's that are on the car now are considered a "max performance summer" tire. The car has been parked for a couple of weeks, and I took it out today after re-installing the 3rd brakelight... man, it DOES take some miles before the parking flat spots come out!!

Thanks again for all the comments and info!!
Nikko

 

Anything north of 30 psi will be fine... If it feels "wiggly" at that PSI, just bring it up until you've reached the right balance of comfort and feedback. Keep an eye on wear patterns, that will be the biggest indicator as to the optimal PSI. I have dropped rear PSI to as low as 18 when I was at the 1/4-mile track, to give the sidewall a bit more flex. But once you leave the track, just be sure to bring the PSI back up to a safe level.

 

Learned another tidbit of information today. Didn't know the tire pressures on an SRT6, is higher (N/A 32F 33R). Seems one set or more on the door sticker for the SRT is 36 PSI?

.

 

Thanks for that info, 2K... I would have thought around 35psi would have been minimum, considering the aspect ratios make the tires little more than rubber "veneers" on the rims . Im gonna try around 32psi and see how it reacts.
Yep... thats what mine says, 36psi ft and rr. Mine is a roadster... I wonder if the hardtop (or a N/A Crossfire) requires a different tire pressure??

I had a '92 convertible 5.0L Mustang years ago, and the convertible car was a few hundred pounds heavier than the hardtop.
Between the framework of the convertible, the mechanism to move it, and the SC in an SRT, I dont doubt that a roadster could be heavier than a hardtop, and maybe need a little more tire pressure.

That Mustangs convertible top was something that DEMANDED a persons attention when putting the top up. It moved slowly for about 80% of its travel when putting the top up, but would snap forward REAL fast when the header got near the windshield. The framework of the top weighed a TON, and could easily break a bone, or even knock a person out if they got hit in the head with the leading edge of it.

 

Yeah, that would be pushing it according to this thread. https://www.crossfireforum.org/forum...-18-front.html

But the 255/35-18 is the same diameter as the 225/40-18. The rims in that thread are 9" wide with a 30mm ET vs a 8.5" wide rim with a 32 ET

This says they would be just under 10mm closer on the inside
Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

Do you have the Koni Shocks installed? Mine had them installed when I bought the car. They're set as soft as they will go and although they take some of the harshness out you still can feel the bumps. About a week ago I bought three 40 lbs bags of water softener salt and put them in the hatch area. That extra 120 lbs plus the spare tire weight (30 lbs?) made it ride super smooth. So for daily driving try driving with some weight back there.