mis-u-jerr

Hey,
Still haven't gotten new rears yet, wanted to go wider, but not to 18's. Just found out that there are 255/40/17, guess I didn't see them before on the tirerack site. According to my calcs:
[(245*.45)*2/25.4]+17
245/45/17 = 25.68' diam
255/40/17 = 25.03

Close enough, right?

Also, for alignment, (needed anyway) I don't need to go to an MB shop right? The reason I ask is that I am taking it in for service in a couple days.
Thanks

Jano

I know that 255's work even though I have 18 inch versus your 17's. But with your V-8 engine, you really should go with more rubber on the road. 10 millimeters can make the difference in extreme cases. Plus you will be able to better feel the road since the 255's have a lower profile wall height (although not by much)and are wider. They might cost a little more, but there worth it.

Luke@tirerack

let's look at the actual facts .... first of all you do not have a 245/45-17 on the rear of a C43 ... it is a 245/40-17 (or atleast that's what it is supposed to have) .... the 255/40-17 would be slightly taller than the proper 245 ... and I would not recommend going to the 255 because you would have more sidewall deflection in the rear tire when compared to the side wall deflection of the front tire and that would adversely effect the handling of your car ....

mis-u-jerr

D'oh!:o
Luke is correct as always... I had a mental lapse in saying that they were 245/45, they are indeed 245/40. So, 245/40 is even closer in size to 255/40, (24.72 vs 25.03, a 1.0% diff).
But since the oem is already 40 rear/45 front, and the difference in back is approx. 1%, would that a noticeable change? The 255/40 are approximately the same size as 255/35/18 (25.031 vs 25.028)
Soooo, out of all of this, is there ANY way to get wider rubber in the back without going to 18's?
Thanks, as always, for your help.

speedybenz

I have been running 255/40/17 sized tires on my C280 for over a year and now have that size on my C43. They work very well.

I also run a 235/40/17 front tire and this seems to help the car understeer less and feel more solid going into corners.

But I have not put that tire on the front of my C43 yet. Currently it's running with 245/40/17 in the front. t of my car need an anglinment really bad so I can't comment on the front tires at this time.

Jeff

mis-u-jerr

Hey thanks Jeff!
Man, those are some big A... tires on the front. If you are running rears on the front, what are going on the rear, 265's?
Thanks
To Jano - Yeah, that is exactly why I wanted more rubber on the road. If it is true that the OBD writes a code every time the traction control comes on, I'm gonna have quite a printout:p
And I don't even race, that is just how I drive...

Jano

Your welcome Mis-u-jerr,

I am running 255/35ZR18's all around on Brabus Monoblock type IV wheels 18x8.5!! That way I can rotate my tires. Although I am not using the best tire brand. I am currently using a good tire, namely Dunlop Sport 9000's. I would have liked to use Bridgestone S-03's or Continental Sport Contact 2's, but I have been stuck buying Dunlop tires since I have been buying in pairs and I don't want to mix tire brands on my car.

Right now I feel that I have all the rubber grip :p in the world since my car has only adequate power from a 2.4 liter V-6 (170 hp).

mis-u-jerr

18 X 8.5 fit in the front without compromising turning? Day-um, that's huge...
After Jeff's post about running the 245's in front, I was also thinking, hmmm, if I did that, I could rotate...
When I took the car in for service yesterday, (still under warranty), the service person said the SO-3's were directional and I couldn't rotate side to side so it looks like I am stuck with one tire, one corner (if she is indeed right, I'll have to get confirmation).
I'm running mixed brands now, S0-3's in front, still have the oem Conti's in back (32K miles!). They have definitely reach the end of their useful life though...
Thanks, Greg.

speedybenz

I forgot to mention that I am running SSR Comp's which are 17"x9.5" in the rear and 17"x8.5" in the front.

My C43 is running the stock ride ht at this time and the front is really high. So I dont know if the 245/40/17 fronts will rub hard once I get the car to the correct ht. However measureing things up, it looks like I will only get some very minor rubbing if any even if I stay with the 245's in frt.

Jeff

Jano

To Mis-u-jerr,

Turning is not compromised, and I even lowered the car with an H&R suspension cup kit. 2 inches in the front, 1.5 inches in the back...

And if S'03's are directional, you can still rotate by changing the front tires to the back, and the back tires to the front. That is what I used to with my Goodyear Eagle GS-C's, because they too were directional. When doing this, directional tires will remain on the side their suppose to stay on. For example a left front tire stays on the left side when rotated to the back left. The same applies to the right tires...

However this rotation for directional tires can only apply when all four tires and wheels are the same size on a given car.

mis-u-jerr

Thanks for the tips Jano. Speedy, I figured that you must be running 8.5's in the front.
Even though the 255 are less than a 1/2" bigger, still running an inch bigger in back? That reminds me of an article I saw once that said if the wheels were just a bit bigger than the tires, the handling would be better, know anything about this? Hmm, so I guess there just isn't any way to get bigger rubber in the back without going to wider wheels, whether 17 or 18", eh? Grrrr, looks like 245's here I come...

How are those SSR's working out? I love the idea of saving 60 lbs of unsprung weight over the monoblocks, maybe someday I will do the deed...
Thanks.

speedybenz

The SSR Comp's are great. You can really feel the difference in the weight and the car handles the bumps better. You can also feel the car seems to be a little faster with the lighter wheels.

And the wider width also helps stabilize the tire sidewall so the car turns in faster and is more stable at the limit.

Big improvement over the AMG Mono's.

Jeff

mis-u-jerr

Thanks.
Looks like I may have to stay 245's if I don't wanna change anything else at this time Probably have to go to new wheels if I was going 255's, either 17's or 18's. I'll report back when I get confirmation on this.
Thanks, Greg.

nukblazi

just a thought on the sidewall deflection.

I have 225/45F and 245/40R S-03s, (17x7.5 on 4 corners) on uneven road surfices the car jounces around a bit, sort of dances if you will.

However, the 245/40s in the rear seem reduce the likelihood, and to increase the predictability of the **** sliding out. Does the "pinch" and the lower tire pressure to keep the wear even "help" when cornering? (Luke?)

43Volts

Luke,

How about this question??? Could I run 245/40-17 in the front and 255/40-17 in the rear?? Would I have any major problems?
I have stock 1998 C43 17" rims.
thanks,
ttt