rguy

If you just go to tirerack.com, I believe the first wheel that shows up for a 2005 C55 is the 18" version of the wheel. I think they might even be using it on the new slk350 (not as sure about that one). Anyway, offset up front is 37mm and outback is 30mm if you go with a 17x7.5 and a 17x8.5 staggered winter setup. (I am not trying to get into a proper sizing argument here. I like the winter sizing I use and will continue to use it.)

noka

Someone posted in this thread earlier:
Stock C55: front = ET30, rear = ET34
Can't seem to get any stable numbers. Any problem with the offset variation?

Rgds,
Norm

rguy

Cldriver, it has dawned on me that they might have continued using the clk430 wheel on the clk500 for awhile and changed it this year. This may be the source of the confusion.

smgC32

Just buy the wheel already! Luke has said he will take it back so there is nothing to loose. And I agree, that it will fit. On a 7.5" wheel with a 225mm tire, the additional 7mm out towards the fender will not pose a clearance problem as long as you stay with this tire size. It is on 8.5" front wheels that offset is much more critical. A ET30 8.5" front wheel has a 12.7mm wider track and will fit with 235's, although I personally prefer a ET32 in this application.

rguy

Who are you talking to about just buy the wheel already? Noka? The offset is a good thing in my opinion. Stock C55 numbers that Noka reiterated are correct and I never said that the stock c55 had 37 and 30 mm offsets. I said that the clk500 wheels had 37 and 30 mm offsets and should virtually 100% be guaranteed to fit for much less money and (I think) a better look.

noka

Sorry if I misquoted you. My misunderstanding. And I'm still confused. I wish there was a website or brochure I could consult to compare all the wheels.

Rgds,
Norm

cldriver

That would be me. Those numbers are for the Stock C55 18" wheels straight from the owners manual. I've taken both wheels off to verify as well. I took them off to get them repaired as I bent both driver side wheels.

Currently the 17" AMG wheels I have seen come in 17x7.5 37 (Front)
and 17x8.5 30 (Rear).

noka

So if using the stock front C32 AMG wheels (offset 37) on all fours for Winter on the C55, there is no problem with fitment or looks, according to Luke at TireRack and some others. Can anyone confirm that (maybe someone who has done it)?

Rgds,
Norm

smgC32

OK, I got confused as well. I re-read all the post and there are multiple questions going on here. My posts referred to a C55 wheel fitting on a C32. The real question is whether a front C32 ET37 wheel will fit on the front of a C55, which has an ET of 30. The rears are constant. The opposite to my previous post will apply. Changing the offset 7mm from 30 to 37 will put the wheel closer to the inside or towards the strut. If the mounting pad thickness has remained constant between the two wheels, then the caliper will hit the inside spoke most likely since there was not much space with the stock caliper clearance to begin with. If the spoke design has changed between the two wheels and the pad thickness has increased than it should fit. Offset is not the only think that affect caliper clearance. For example, (and not applicable to the C32 wheel at this moment), if you were to take the stock C55 wheel with an offset of 30 and add 7mm to the mounting surface (like adding a spacer), you would end up with a wheel that moved out towards the fender with a new offset of 23mm and that would provide 7mm additional clearance between the inside spoke and the caliper face. In contrast, if you were to take away 7mm from the stock C55 wheel's mounting surface, you would end up with a wheel that moved in towards the strut with a new offset of 37. In addition to the wheel's center line moving in, the relationship between the caliper and the inside spokes would decrease by 7mm, most likely causing a clearance problem. Assuming that the C55 is using the same caliper, rotor, spindle, control arm, the only way to know if it would fit besides trying it! would be to measure the current clearance between the stock C32 caliper face the the stock C32 front wheel inside spoke surface. If more than 7mm exists, then it will fit. Are we more confused now...

Blake P

Reading the post above leads me to believe that I should have absolutely NO PROBLEM fitting AMG brake kit on my C230 with C55 wheels with the extra 7mm offset. I was confused in thinking that lower offset meant less clearance, but I guess that's the opposite, right?

smgC32

The lower the offset number, the farther to the outside the wheel sits. The higher the number, the closer to the inside it will sit. Offset can be misleading though in caliper clearance, since offset is only the relationship between the wheels mounting pad and its centerline. It is the wheel's spoke design and distance from the mounting pad to the backside of the spokes that is critical in proper caliper clearance. The same offset wheels in the same widths can either clear or not clear the same caliper. With the same offset wheel, the wider the lip, the less caliper clearance there will be. The narrower the lip, the more clearance there will be. Since the offset is the same, it is the mounting pad thickness that changes. When offset changes, then you must confirm all measurements to ensure proper fitment and clearance issues. Speak with several reputable wheel resellers and they should steer you in the right direction when looking for aftermarket wheels. Wheel Experts is a good source as they have extensive experience with MB products, including the C32.

rguy

The way that I have always seen offset measured is by taking the mounting surface and the distance to the centerline and subtracting the two. To me this means that if you increase the offset you widen the track because you increase how much the wheel is offset from the mounting surface. I don't really understand why you guys feel that more offset is a narrower track.

Maybe et offset and actual offset are different things. Every website I have read about measuring offset has stated the above though. Please help with this concept.

Thank you. And try to be positively educational rather than condescending, as is the tendency of some posts on the site.

smgC32

You state: "The way that I have always seen offset measured is by taking the mounting surface and the distance to the centerline and subtracting the two." I think you meant that the measurement is the distance between the mounting surface and the centerline. There is no subtraction involved in the way you have stated it. To get the difference, you need to find where the mounting pad resides in relation to the centerline of the wheel. The way this is done is to measure the backspacing of the wheel, which is the measurement from the pad surface to the outer rim bead on the backside of the wheel. You then take this number and subtract it from .50 times the width of the wheel, or half of the wheels width.

If you take the stock 7.5" wheel width and divide it by two, you get 3.75". If the mounting pad backspace dimension is 4.93", then you subtract the two numbers and get 1.18", which is the difference between the wheel's centerline and the mounting pad, or the offset. Since the mounting pad is towards the outside of the centerline, it is a positive offset. If a wheels mounting pad is towards the inside of the centerline it is a negative offset. So, we now have to convert 1.18" inches to mm, and we get an offset/ET of 30!

When you increase the offset number, you are increasing the distance between the centerline of the wheel and the mounting pad. By doing this, the wheel needs to be pushed farther in for the wheel's mounting pad to come in contact with the hub surface as the wheel sits within the wheel well. Therefore, the larger the number in positive offset, the closer the wheel sits to the inside. Hope that helps. It is sometimes difficult to visualize and most people get confused by this concept. Now try to think what happens when an offset stays constant, but the wheel's width increases!

noka

Are the wheels you purchased offset 37? How close are the calipers on the front?

Rgds,
Norm

noka

Perhaps I missed a followup post but did you ever pull your stock C55 wheels and confirm the offset for front/rear?

Rgds,
Norm

NORTH 44 C63

37mm they are>>>>>fit perfect over the calipers
Since I started this thread and went through the process, Tirerack has updated their order page (thanks to Luke) to reflect what 17" wheels will fit the C55.

Here is the link. All specs including offsets are available on this site.

to get to the wheel page, select C55 as your vehicle and then pick a winter tire. then it will redirect you to the page that has 17" wheel packages link half way down the page. Select that and follow the bouncing ball>>>>


http://www.tirerack.com/snow/WinterW...&Qty5=4&Qty6=4

noka

Thanks. I just came to the realization that the stock 18" wheel is not the same style as the 17" C32 203 dual spoke. The C55 has "AMG" once and the C32 is stamped twice. Slightly different style also. On the C55 the small slots extend all the way to the lugs but on the C32 they stop short. I think the C55 wheels are "209" or something. Anyway, I like the wheels you got more and more as I look at them and even though there is a 7mm offset difference compared to stock, your tests prove they fit OK. I couldn't really tell from your pics (in other post) what the wheel gap looks like. Perhaps you could comment on that. The other choice would be to move to 18" Winter wheels but .. less rim protection, fewer tire choice and higher price. Now I just have to decide if I really need to drive it on the crappy days. The Pirelli P-Zero's would be horrible in snow/ice but I suppose I could wait for the sunny days when streets are clear and dry. It's always a gamble. Sometimes I think I should get the Winter setup just for piece of mind, in case I ever needed to take it out on those bad days.

Sorry for rambling. Maybe you have time to comment.

Oh, btw, I just took delivery!! She's in the garage sitting there all pretty!! Time to RT(F)M.


Rgds,
Norm

NORTH 44 C63

Soooo, where are some pic's of your new ride????

Yes, I like the flat face 203 - 5 spoke better all the time as well. I have been very, very happy with how easy they are to keep cleen. I think its the better choice over the double spoke for a winter setup. I has in northern Ontario this week and we had lots of snow for a few days. First mornnig there was about 8" on the ground and I had no problem. Just put it in "C" and away I went, nice and smooth with very little slip. I think the 17" setup is the better choice for snow as a higher profile tire will always cut and grip better. A lot less cost as well. Tirerack has them on for $299 right now and with a set of PA2's you under $2000.00.

Here are some quik pics of the caliper wheel relationship to answer your other question.

noka

I'll try to snap one later and then figure out how to post on this site (since I haven't done it yet. I assume no big deal).

Yes, it answers my question about caliper clearance. Not sure about fender wheel gap though. Does it look OK with those 17's?

By the way, now that I have an owner's manual to read it also answers my questions about wheel offset. Although the stock staggered 18" wheels are fr=30 and rr=34 offset, the wheel recommendation for C55 when all four are 7.5 x 17 is offset=37. So yours being 37 is just the ticket and the C32 203 double spoke being 37 would be fine as well, from an offset perspective at least.


What made you go with the Michelin PA2 over the Dunlop Wintersport M3? A toss of the coin or some experience with them? I guess I heard decent things about Blizzak LM-22 as well.

Rgds,
Norm

NORTH 44 C63

I went with the PA2's for their all around performance and low noise.
I have been running Michelin's for years, both wither and summer and find they work best for me. I guess I'm a little brand loyal as well.
Dunlop, Pirelli and Bridgestone make great products for winter but in my meager opinion, the PA2 ist the best all around. The Pirelli might be better on dry, the Bizzak might be better on snow and the Dunlop better on ice, but I wanted an all around and they are the quietest snow tire I've ever owned......you can't go wrong with that PKG from Tire Rack...

TNblkc230wz

Lets remember what off-set is. It is the distance from the mounting pad to the center line of the rim. If you have thick or in-set spokes, the rim won't clear the caliper even if it is the stock off-set when you have large calipers.

Moral: Choose your rims wisely!

noka

Thanks. I did try to qualify it by saying, "... C32 203 double spoke being 37 would be fine as well, from an offset perspective at least". I now know there are wheel variations w.r.t. possible spoke location, etc., that could cause problems. Unfortunately, I am not an expert in these matters and must rely on the judgement of others for some things. The trick is finding the right expert to listen to. TireRack now lists the 203 and 209 split spoke 7.5 x 17 wheels for Winter use, in addition to the wheel NORTH 44 C55 has.

I am trying!

Rgds,
Norm

noka

Dohh! Just realized I'm limited to 800x600 on this site and my camera is set to 1280x960 by default.

Rgds,
Norm

NORTH 44 C63

can't u save to your desktop or photo editor and change the ratio???

noka

When I changed to 800x600, then it just cropped the pic so I only got a piece of it. Not sure how to change entire pic from 1280x960 jpg to 800x600 jpg. Not yet anyway.

By the way, I forgot to ask. Did the new Winter AMG wheels you got take the same lug bolts as the stock wheels?

Rgds,
Norm