SeaCoupe

I think I knowmy answer, I just want to check other opines.

I may have a deal on some 245/45 17 Contis. I currently run a 245/40/17 on my rear. Any thoughts I should consider other than the tire being slightly taller?

Thanks,

Ed

fookoo303

i did the exact same thing you did with conti dws tires. I actually like it better with the taller tires. Its rides more comfortably and seems to grip better in the snow. It does look a little bulky but not by much. I can post a pic you'd like to see it a sedan.

Sorry for not having a technical response in the matter.

Glyn M Ruck

Aside from the obvious speedo under reading it could trigger the ESP - rotational variation back to front. ESP calibration is not all that accurate on these cars. I've seen it trigger at under 2% variation in rolling circumference on some cars but not others.

SeaCoupe

Oops that is not good. Would driving with the ESP off cure this?

I run 17" staggered CLK rims on my car. 225/45 front and 245/40 rear.

Hmm, Maybe I should stay with the 245/40 size.

splinter

<---not a guru

Our ESP can easily accommodate up to an inch of OD fore/aft variance; I’ve done just that with no untoward machinations.

Budgeting to **** away yet another $1000 at the local Michelin dealer next month. They’ll be true and sticky miles though.

fookoo303

Ive been running the 245/45/17 in the rears in conjunction with the 225/40/17 up front for the past few months in the unpredictable colorado weather and I have had no problems with esp. My esp works just as it always has in slippery conditions.

Glyn M Ruck

Ed - go for it. If you ever have a flashing ESP light you know why. As I said above I've found some cars sensitive & others not. splinter & fookoo have good experience.

I openly admit to always trying to do the right thing & sometimes being pedantic in that regard. You are not going to break anything.

Save some bucks.

phister

i'm running 215/45/17 front and 245/40/17 rear and I've had no ESP issues so far...

fookoo303

Sorry Glyn, I wasn't trying to disregard your statement, I'm sure you are correct (since you're very rarely wrong ) . It's always hard to say with the electronics in the w203, with what kind of tolerance each vehicle tends to have. Many things seem to be sporadic in fact.

The safe side is to stick with the recommended specs from the factory, but just wanted to input the experience I'm having. But, it also seems my car doesn't fall into the "norm" with the disaster streak that early 203's hold since I've had absolutely none of the common, major problems that has been published here.

seagel1000

I switched to 245/45/17 in the rears for the past two or three tire changes. Never had an issue with it. It actually makes the rear look a bit lowered since it takes the gap away with the extra rubber filling in the fenders

Glyn M Ruck

Good heavens - No problem at all - One thing I don't know is if there is a way of changing sensitivity of the ESP with STAR. People are most welcome to disagree with me - I'm not sensitive about such things & I learn. I still have much to learn about Benz cars.

UK-C200

Glyn, you are rarely wrong! :-) Couple of things I've noticed, the variances seem to be software related as much as hardware, and also seem to be more common on cars with low-line TPMS, which makes sense to me, as MB uses rotational variance to detect a "low" tire.

You can adjust tire size in Star to make sure that your speedo remains accurate, but I've not seen a supported way to program front/rear variance. I've been told, but had no reason to play with it, that in dev mode you can set a variance.

ESP has saved my bacon a couple of times, and is considered part of the safety systems, so I'm loath to play around with it much.

ohlord

225/45/17 front and 245/40/17 I would believe no issues they are taller than oem but within 3% per mile of being the same.
You listed "245/45/17 in the rears in conjunction with the 225/40/17 up front"
and no issues? The front tires would be spinning 55 more times per mile
864 vs 809 than the rears. You either have your profiles mixed up or the car has serious issues.
A % difference that large in rolling circumference will affect abs,cruise,and can harm the transmission. Something is not right.

Someone said to just try them no harm can happen?
Yes harm can happen The transmission can be damaged,ABS can trigger and cause control issues,limp mode.
Match f/r to under 3%

d1no

40 series to 45 isnt all that crazy different. Im sure your car wont break down from this. I plan on running 225 40 18 and 265 35 18 on my rims in a few weeks.

On my old car I ran 205 65 15 and stock size was 195 65 15 and my car was lowered so it rubbed a tad on bumps but nothing else happend.

Honestly I doubt the car is that sensitive that such a slight difference in tire diameter will trigger stuff and harm your car.

splinter

Your conjecture is unfounded given the C’s relatively antiquated electronics.

MB anticipated and has allowed for such variables. Trust you’re aware tire manufacturers are permitted by law up to a 3% differential within the same ostensive sizing nomenclature. When you have a spare moment, calculate the overall diameter difference between a new tire’s ~11/32” tread depth with when it’s worn to its TWIs, ascribing particular emphasis on rotations per mile. Multiply by two to account for front and rear stack-up. Combined with the aforementioned manufacturing discrepancies, what does your arithmetic show? Regardless, I’ve exploited those same permissible differences (during daily driving) to suit my specific tire preferences with absolutely no ill effects. Its ECU/EGS/TCU, ABS, BAS, ESP/ASR and cruise control continue to function as delivered. Tangentially, COMAND asks for not only tire size, but also whether they’re “new” or “used” during its initial programming. Somehow my $10 handheld GPS is more accurate.

Certainly wouldn’t have suggested SeaCoupe give ‘em a go if I believed they would harm his car in any way.

ohlord

mentioned are over 1.6 inches different in dia. display tire wear or inflation that would allow for that difference.
3% is not over 7% last I looked and that is the difference in using a
"245/45/17 in the rears in conjunction with the 225/40/17"
my observation was on that members(fookoo303) statement.
Your's is on an entirely different tire set up.
The op going from a 225/45 front and 245/40 rear to a 225/45/17 front
and 245/45/17 rear would be within the correct error margin.

Unless fookoo303 transposed his tire width and profile he is not running without issues,no matter what convoluted logic you can toss out.
BTW any abs optioned car with tire width and profiles that had 1.6 inches difference in diameter front to back would have the abs bucking like a bull. I am sure the antiguated electronics on the C are far more sensitive.
Wait till fookoo303 checks in with his relook at what tires he has and the sizes before you condemn my conjecture.


d1no
Revs per Mile: 829.3
Revs per Mile: 822.1
your profiles are in range

however if you think going from one profile to another makes no difference
try a 225/35/18 on the front and a 265/40/18 on the rear and see what happens.
Revs per Mile: 859.5
Revs per Mile: 789.6
Do you sense a problem? or still doubt "That such a slight difference in tire diameter will trigger stuff and harm your car."
in effect that is what fookoo303 thinks he did and which I content he has his numbers transposed

splinter

^ You be backpedaling?

Your “match f/r to under 3%” admonition has been proven spurious by several who’ve altered their W203.
Wouldn’t condone it with a 4Matic though.

I’ll concede fookoo303 may have a 45 aspect ratio up front. ;)

ohlord

The op is at going from a 225/45 front and 245/40 rear to a 225/45/17 front
and 245/45/17 rear within the 3% and no issues.
55 revs per mile difference is an issue and when the member that transposed his numbers posts the correct info We will see why he has no issues.
He's not running lower 40's up front and 45's on the rears that's why.
And in your past experience you were not running tire width and profiles that were 55 revs per mile different either or you would have had issues.
That's 359 feet per mile that the tires front to rear need to be catching up. ABS is going to think the car has lost traction,skidding under braking,or speed sensors have gone wonkers.
At least we agree on one thing he has 45's on the front

Glyn M Ruck

Let's get one thing straight - you are not going to damage anything. Not brakes & certainly not the transmission. The worst you can do is trigger a few lights. Triggering limp is highly unlikely & even in that case you would not damage anything. The worst I have seen with a bad mismatch is an ESP light flashing ocassionally. I think that UK-C200 has a point with cars that have passive TPMS activated.

The 4Matic is a different issue for very obvious reasons.

fookoo303

ohlord i believe you are correct. I made a mistake and think i have a 45 series up front in conjunction with a 45 in the rear. My front tires are the suggested oem size and my rears are 45's. Good catch.

ohlord

That had to be the situation.
Now if I can get Glyn M Ruck to check with any qualified mechanic or MB technician that knows what he is talking about( for certainly Glyn is not qualified) A normal non 4matic as well as a 4matic transmission can be damaged after prolonged use of tires that are out of error range and not only trigger lights but alternate braking with abs to try to compensate for the difference. The 4matic would be damaged more.
Your esp would revolt,your cruise control would not activate,and if the worst he has seen in a case of mismatched tires front to rear is an "occasional" ESP light he has not seen a real case of mismatched tires.Nor drivin on a set of "bad" mismatched tires.
Even the kid down at the corner tire store knows that you don't install tires of badly different diameters (front vs rear )on an ABS/esp/bas equipt car
"Let's get one thing straight " is a bold statement when not qualified to make such. A few revs per mile fine. The strain on the drivetrain 55 revs per mile (359feet)mismatch or any "bad mismatch" and you keep driving, something is going to give.And if you did keep driving with the way the car was acting up you would deserve the mechanical damage encountered. Although you would most likely crash the car the first time you ran into a hard braking situation so that would be the least of your problems. Some people might not consider that not damaging anything
Any tire dealer that would install badly mismatched tires front vs rear would be negligent.
Only noobs and those without the knowledge make that mistake.
So when Glyn does his homework all will be well with the world.
Now that the transposed tire size issue has been resolved

Glyn M Ruck

I understand the Merc Auto tranny intimately & the Bosch ABS system.

Tyre mismatch back to front places zero strain on the transmission on rear drive vehicles - there is no conflict. Gross mismatch across the rear axle will ultimately cause differential troubles because the planetary set runs constantly. In reality mostly an issue on trucks & busses. (especially Merc busses)

Mismatch of tyres will not in anyway damage the braking system. Gross mismatch can cause erratic performance from the ABS system - Yes. Likewise gross mismatch back to front will cause erratic behaviour from the ESP & BAS. Gross mismatch will not damage the vehicle mechanically. It could certainly make an accident more likely under extreme conditions. That is not the question here plus we are not talking gross mismatch.

Any sane driver would immediately sense something wrong if the ESP became unstable as a result of the implausible input from the various speed sensors. It would firstly back off the throttle and then intervene in braking appropriate wheels on the car to try & regain stability. This would all be extremely obvious.

I respectfully suggest that you do some homework.

I was the one suggesting an over cautious approach on this thread. splinter et al is correct in this matter of one profile size change on most W203 RWD's.

ohlord

I made was on the post fookoo303 made 55revs per mile is gross mismatch and would lead to part failure.
He cleared it up as I suspected by taking a look at his tires and seeing that his profiles were mistated.
You can beat the dead horse all day and you would still be dead wrong about damage to the car at his original misquoted tire sizes.
My homework has been done a long time ago.
From another recent post........
Might I suggest you also bone up on your lack of knowledge on O2 sensors. Rear o2's get replaced at 100k Mile intervals. They get lazy and also if left till they fail and throw a code as you suggest can get frozen into the pipes and cost far more than replacing at the factory interval of 100k miles.
For a guy who claims to have a lot to learn about Mercedes and open to learning more you sure pass out a lot of poor information

Glyn M Ruck

I fully understand O2 sensor cycling rates becoming slow. I have done a lot of work with Bosch during my career. Let me assure you that O2 sensors can become "frozen" in their receptacles long before 100K miles.

Suggest you read some of my previous commentary on O2 sensors. Far more detail than said thread.

My comment was one of humility rather than lack of knowledge & most here know that. I don't require to beat my drum.

splinter

My intent in this thread was to share firsthand experience with tire fitment in an effort to help SeaCoupe get a “deal” on some Contis.
In hindsight, the cabernet sauvignon and I got a little too frisky on the keyboard last night. Regret having set an inappropriate tone.

Everyone who’s posted here has contributed significantly to this forum over the years, so there’s no need for personal attacks. Thanks.