95viper

I have been doing a lot of research and wondering if going up 1" in overall diameter is really such a big deal. My purpose is because I think a 305/25/20 sidewall sure is skinny and I would like to get more meat there if possible. Here are my findings:

07CLS550 stock - Not lowered; OEM stock

Common 20x9 255/30/20 and 20x11 305/25/20 = 26" diameter
Proposed 20x9 255/35/20 and 20x11 305/30/20 - 27.2" diameter

Speedometer
26” 27”
30mph = 31.15 mph
60mph = 62.30mph
90mph = 93.46mph

Gear ratio
26” / 27”
1st 4.38 / 4.54
2nd 2.86 / 2.97
3rd 1.92 / 1.99
4th 1.37 / 1.42
5th 1 / 1.03
6th .82 /
7th .73 /

My question is whether this will really cause a problem assuming the right offsets do not cause the taller tires to rub.

CLSED550

No good , I replied to other post. You cannot run those tires. To big.
I don't think they make a 305 30 20, either way not good.
Maximum tire height is 26.7 and every tire brand is little different. (This is with correct offset).
Height of the car don't matter, the Suspension components are in the way.
Look in your wheel well of your car now (with tire on) and look how much room is between the tire and strut/airbag mount. Then take into consideration a wider and taller tire and how small that gap will get.
Hope that helps
---Eddie

95viper

Oh NOW I get it. This sentence did it for me! Before I was only thinking of tires and wheel well but of course the suspension stays moving with the hub. I am looking at things completely different now.

Height of the car doesn't matter, the Suspension components are in the way.

Thank you.

95viper

You guys might find this interesting. After talking to CLSED550, I went out and measured my gap. He was right because I could barely get a 1/2 spacer between the tire and threads of upper a arm bolt. I guess I could get a grinder out there if I wanted to get silly .

Therefore I gave up on the 27" diameter sized and went back to what everyone runs. 225/30/20. While searching on these brands I came across one that has a wider sidewall. Bridgestone S001. They are 26.5. That will fit perfect and give me as much sidewall as possible.

Problem - they are EXPENSIVE

threeMBs

You probably meant 255/30-20 (not 225/30-20), which is a stock diameter of 26".

FYI: you can safely use 245/35-20 front and 285/30-20 rear with stock suspensions. Both are 26.8" for almost all brands and fit with zero issues on non-lowered CLSs.

95viper

Yes I did mean 255...thanks. My point was that there is a rare option to get more sidewall although expensive.

Your 248 and 285 suggestion solves a diameter issue but I would not run that width on a 9 and 11 inch rim. Curbs are just waiting to happen.

threeMBs

If you do not have the 9/11 wheels yet, then you can still run 245/285 and get 8.5/10 wheels. However, if you have wheels already, then you're stuck with 305/25-20 rear. For front you can use 265/30-20 (though this size is much less readily available and is pricier than 255/30-20).

CLSED550

This is what we are talking about if anyone cares to see..
This is with a 255 40 18

threeMBs

That picture is with stock front 26" diameter. With 255/35-20 (27"), tire touches that bolt. Car still can be driven, but it will create a grove in a tire at the point of friction (I actually used 255/35-20 front tire on my SL for years and know what I'm saying). However, with 245/35-20 (26.8") tire (what I'm using now), there is enough clearance that there is absolutely no rubbing with pictured bolt. All above applies to both C219 and R230.

245/35-20 can even be used on C218 (we tried that too) that has a bit less "room" than C219, while 255/35-20 (on C218) can not.

95viper

Yep, there it is. If that nut/end of bolt was 1/4 higher then all problems would be solved. Not much there to grind off too and grinding off 1/8" or so from the arm so the nut spins up more is probably a bad idea since I am sure MBZ engineers wanted it that thickness for a reason

The best idea was suggested by three MBs. Stick to a 8.5 / 10 wide rims if you want to run 35 / 30 series tires in 20". If you do that you can run 245 / 285 and not hit this bolt.

95viper

Is there any chance that this only applies to a SL? I ask because I just went out with a straight edge and tape measurer. I have 26" diameter tires 255/40/18 Pilot Sport A/S 3. They have 3k miles on them so they have to be less than 26" now.

I have exactly 3/8" from top of tread to bottom of bolt.
5/8" from tread to bottom of nut.
15/16" from tread to bottom of A arm.

With these measurements I have a hard time understanding how a 26.8" diameter tire would work. Is there something that I am missing? Is there any way that the bolt/arm moves away from the tire when the suspension raises? Or maybe the SL's have a little more room than the CLS?

I would kill if someone would try this tire size on a CLS.

95viper

Guys, Especially threeMBs and CLSED550 since you have been commenting on this and obviously have experience...

This continues to bug me so I did a bunch of tests today. I removed my tire and inspected everything. In CLSED550's pic above there is an arm that goes around the tire and down to the back of the hub. It is a significant part and is directly mounted to the back of the hub and also serves as lower suspension mounting points. It is fixed and moves with the hub.

Back to the picture, there is a upper a arm with a ball joint. It is a strangely shaped part with a triangle piece attached to the joint that mounts to the a arm with three bolts. When the tire travels up and down the hub moves, the a arm moves and everything pivots on this ball joint.

The important point here is that the nut in the picture above never moves away or towards the hub. It is fixed and moves with the hub. I tested this. I measured from the edge of the rotor to the bottom of the nut. 7 1/8. I put jack stand and lowered the car on the suspension raising the hub and re-measured. 7 1/8. I opened the car door and the car lowered the suspension more. I re-measured 7 1/8.

The OEM front rotor is 13". Half is 6 1/2. Add 7 1/8 and you get 13 5/8.

If my initial goal was to get a 27" overall diameter tire on there....specifically a 255/35/20 Pilot Super Sport....how would it rub? Half of 27" is 13 1/2 and I have 13 5/8 room.

95viper

P.S. Before you ask, the bolt is almost exactly above the top of the rotor so it wasn't like I was measuring on an angle and got a longer measurement.

threeMBs

95viper, as I stated above in post #9, I actually used 255/35-20 on my SL (the problem part is identical to CLS so it does apply here as well). When I was using 255/35-20 with "recommended" range of wheels' offsets, that bolt was touching the tire and created a grove in it during driving. Other than that visible clue, there was absolutely no driving issues while with 255. You can actually use 255/35-20 if you "push" wheels out either with much lower offset wheels (say low teens) or spacers with whatever wheels you have as long as resulting offset would be as above. If you're looking for a higher sidewall (as I was) the difference between 245/35 and 255/35 is only about .1" (diameter is only .2"). IMHO, above (.1" sidewall difference) is quit insignificant hence now I'm running 245/35 on all my SL wheels.

95viper

Totally makes sense now since they share this part. What do you think about popping the ball joint out and drilling 1/8" into the hole from the bottom with a bit wide enough to allow the nut to spin up 1/8" more and then grind down the excess bolt. That would clear a 27" tire and do nothing to the suspension.

CLSED550

I have to look at the suspension tomorrow. Now you got me thinking after I decide to put factory 63 wheel on my car!

95viper

Just looked at it again. I think I would rather not manually drill it out while on car. I can easily picture it being drilled on an angle. In addition, using a drill bit would create a slight curved hole since the drill bit is not flat across at tip.

I think the best way would be to totally remove this part and have a machine shop perfectly grind it down something like 1/8" on the bottom side facing the nut. Then the nut could spin up and excess cut off.

95viper

Problem is that this thing is secured to he back of the hub and has multiple connections that would need to be removed. Kind of a hassle but not the end of the world.

threeMBs

I just came across a different thread where its clear that you already have the wheels (9f/11r). Then forget 245/285 I suggested before as 285/30-20 are too narrow for 11" wide. I think its OK to run 255/35-20 front (you may need 12mm spacers to push front offset from et25 to et13 to clear that bolt) and 295/30-20 rear (both are 27") also with 10mm spacers for et25.

95viper

Thanks for the advice. I am going to take a different route though. I am having HRE rebarrel the inner barrels on the rear rims making them 10.5 with et29. I want to run 255 and 295 and my et25 and et29 is perfect for me.

I have 255 on the front now albeit with a 18" rim. I do not want to push them out with spacers to clear the bolt. I don't want them sticking out further than they are. I am still going to modify that bolt even if it takes removing the entire arm and taking it to a machine shop.

95viper

Update - I mounted a Hancock 245/35/20 today. I can just get a 1/4 wide pencil between it and the tire. This is a 26.8 so I will call them today to order a 255/35/20 which is 27. I would really like to get more width on this 9" rim. My option is to have HRE rebarrel it into a 8.5 and run these tires.

95viper

Hankook.....I used to work with a Hancock and always misspell that.

95viper

Completed more testing. Interesting. UDWANIT2 in another thread was warning about rubbing when turning as opposed to hitting the A arm bolt. I just turned the wheels with the 245/35/20 and there is about 1/16 or 1/32" between the edge of the tire and the front plastic liner. I guess I could mark it, remove it, cut it and reshape it to clear the tire. Hmmm.

So there is another thing to worry about when trying a 255/35/20. No need to lower because the bigger diameter filled up the wheel gap nicely.

threeMBs

I believe I told you that (245/35-20 max, safely) as soon as you posted the question. And yes, with 255/35-20 on 9" wide you will rub not only against that bolt, but also on wheels' lining. 245/35-20 on 8.5" with correct offset (mid-high teens to low-mid 20s) is in my experience the way to go.

95viper

Yes you did but I had to try it myself. I have exhausted this research.

Now to decide if I want to spend that much money to have HRE re-barrel the fronts and run these 245/35/20. Or I could run a 30/25 setup which is what I wanted to avoid all along.