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Discussion Starter · #1 ·
Hi all,
I have a 2014 CLA 250 4Matic with the sport package. My car currently has the 18” AMG rims with run flats (225/40 R18 92H). I am not a fan of the run flats due to the ride quality so going to switch to conventional tires hoping it will help the ride quality. My question is: I am planning on going with a slightly bigger sidewall/profile in order to have a bit more meat in the tires so it will also help the ride. Has anyone ever gone down this route? So basically doing a 225/45 R18 92H. So 45 instead of 40. Does anyone know if there is enough space? Hoping that the combination of the conventional tires and the wider sidewall will help the ride quality.
 

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Discussion Starter · #4 ·
Great. Thanks for the feedback. I know this topic on ride comfort has been beaten to death, but I love my CLA so trying my best to make the ride as comfy as possible.
 

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I replaced the Bridgestone runflats with Michelin PSS, quickly replaced them with A/S 4, and intend to try a Michelin Grand Touring tire next if the clearances allow. It seems to me that a higher profile will deliver a smoother ride.
 

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Discussion Starter · #6 ·
Thanks 2katman2. I currently have Bridgestone runflats. They are marginally better than my previous runflats but not by much. I am sure the better solution is to go with smaller rims but that is a much bigger investment. Spoke to a friend that works at a dealer. He spoke to a tech and the tech told him that no one that he knows has ever done it but he thinks there is enough room to do it. He also said that the speedo would not be affected although I tend to agree more with @jmc that it will be affected by just a little bit.
 

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The dealer should be able to correct your speedo after the tire change. It’s a simple perimeter change in the ecu.

Also, I’ve had a lot of trouble with run-flats on our CLA 250 4matic Ed. 1 with the AMC 18” wheels. ( see my thread about this). We changed from the OE Goodyear RFs to Continental RFs. Sure we’ve still had a few problems due to road quality and road hazards, but the ride is quieter and a little improved and have had much less problems than with the Goodyears.


Sent from my iPhone using Tapatalk
 

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News flash: If you try higher profile tires, apparently it creates issues with the computer that controls the suspension as well as throwing off the speedo. The only solution is to maintain overall tire height by going to smaller wheels if you up the sidewall size.

Rats.
 

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News flash: If you try higher profile tires, apparently it creates issues with the computer that controls the suspension as well as throwing off the speedo. The only solution is to maintain overall tire height by going to smaller wheels if you up the sidewall size.

Rats.
The suspension is controlled by a computer in the 2014?
 

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Hi all,
I have a 2014 CLA 250 4Matic with the sport package. My car currently has the 18” AMG rims with run flats (225/40 R18 92H). I am not a fan of the run flats due to the ride quality so going to switch to conventional tires hoping it will help the ride quality. My question is: I am planning on going with a slightly bigger sidewall/profile in order to have a bit more meat in the tires so it will also help the ride. Has anyone ever gone down this route? So basically doing a 225/45 R18 92H. So 45 instead of 40. Does anyone know if there is enough space? Hoping that the combination of the conventional tires and the wider sidewall will help the ride quality.
Did you end up putting larger profile tyres on your cla250. looking at doing the same to soften ride and increase clearance on cla200. 45 profile would give about 10mm more clearance and 50 would give about 20.mm more. 50 may be little too big
 

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I have pondered this change for a while.

The 50 is a no no. Also a wider 235/40/18 will hit the leg of the strut. You could go 235/40/18 with a small spacer such as 10mm.

In theory i think 225/45/18's could work. Only thing that it could hit is the bottom of the shock.

As they say the proof is in the pudding. I may get my local garage to have a test fit of a 45 profile if they will let me try
 

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stock rim 18x7.5_52 with 225/40-18 has lots of clearance - will sustain 235/40-18 as it is a factory option
i use 18x8_48 with 235/40-18 now and there is a lot of room all around for even wider tires (if only they made 245/38-18)
 

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stock rim 18x7.5_52 with 225/40-18 has lots of clearance - will sustain 235/40-18 as it is a factory option
i use 18x8_48 with 235/40-18 now and there is a lot of room all around for even wider tires (if only they made 245/38-18)
Yeah the 235/40/18 has a lower offset wheel on the CLA45

The stock AMG Line / sport package has ET52 alloys and the inside of the rim is very close to the shock. I read before another member tried 235 on the front and it rubbed against the shock.

From myself looking at it with a 225 there is not much gap to the shock at all
 

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in stock form with the 18s and 225 you can put your fingers between the tire and strut or ~15mm spacing
that's the first thing i checked years ago when i first looked at the front suspension at the dealers
hence the 235 works for most tires if you call for that option (the ones that dont have overly protruding rim beads)
also the factory gearbox cal is accurate for 235/40 not 225/40 ... drive data bears that out in terms of distance and speed errors (that 1.24% error drove me nuts)
if folks are getting rubs then something else is awry?
 

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Watch tyre test videos and see how much the sidewall flexes left to right when giving it some round a bend

Just going by what i read on here from another poster.

I believe there is also a lot of discrepancies between say a 235mm wide from one manufacturer and a 235mm from another manufacturer
 

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though the flex is at the contact patch with lots of surrounding space

the tire to strut clearance is mostly static unless the circumferential rotation rate exceeds the rubber deformation recovery time scale

so lets say typical 60mph or 1mpm and typical tire size yields 850rpm or 14rps or 72ms per rev or 36ms per half rev
thus the tire flex/bulging has to recover within 36ms presuming a 1g cornering move at 60mph and full friction no slip so max sidewall deformation
36ms is roughly 40% of your typical human reaction time … and the typical elastic deformation shape recovery time for a good tough sidewall is of course faster than 36ms or roughly 27~28Hz … else all of us will have scrubbed interior sidewalls from normal driving

even accounting for damped oscillation type recovery kinetics the flex/bulge is gone by the time the tire rotates from ground to strut

qed
 

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though the flex is at the contact patch with lots of surrounding space

the tire to strut clearance is mostly static unless the circumferential rotation rate exceeds the rubber deformation recovery time scale

so lets say typical 60mph or 1mpm and typical tire size yields 850rpm or 14rps or 72ms per rev or 36ms per half rev
thus the tire flex/bulging has to recover within 36ms presuming a 1g cornering move at 60mph and full friction no slip so max sidewall deformation
36ms is roughly 40% of your typical human reaction time … and the typical elastic deformation shape recovery time for a good tough sidewall is of course faster than 36ms or roughly 27~28Hz … else all of us will have scrubbed interior sidewalls from normal driving

even accounting for damped oscillation type recovery kinetics the flex/bulge is gone by the time the tire rotates from ground to strut

qed
Yeah thats what i thought 🤯
 

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take a ball hammer
start a video at very fast frame rate
hit the sidewall (at say 3 oclock) hard and grab that video
play it back at max slo mo
watch the rubber recovery
observe the compensated frame rate timestamps

(but do miss your rim … protect with carpeted plywood or something)
 
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