Alloy wheels keep breaking! Options..

[thsale]

Hi there,

I drive a family Mercedes 2013 C250 estate. It has low profile tyres, with different sizes on the front and back, they are 225/40R18 Y92 on the front and 255/35R18 Y94 on the rear (the rears are wider). I have been using Goodyear Eagle F1 tyres all round.

Anyway, we live in the country and there are plenty of potholes, its hard to avoid them even though we try. I have now cracked three alloys, over the course of three years, with the last one being a few days ago in Cornwall, where we woke up to a flat tyre (thank goodness for the space saver!!). I ended up getting them all welded each time it has happened, but I think its time to consider other wheels. Basically you end up with a flat tyre, usually overnight, and on investigation you usually find a crack in the alloy.

Could I simply drop a wheel size and go from 18 inch to 17 alloys but retain the width at the rear? Would I need to do anything else? With 17 inch wheels, could I use a tyre which is not so low profile? There is not room now in the wheel arch to add a tyre with more rubber?

Could I have defective or sub-optimal alloys? Are there 'stronger' alloys?

Any tips or advice gratefully received!
Thanks

[Pica-Pica]

You should check the tyre label to see what is the minimum wheel size you can use. That will also give you the appropriate tyre sizes. You could try forged alloys, very expensive, or steel wheels.

[sparkyhx]

smaller rims bigger tyres, it will make it more comfy as well.

[JD]

As a previous owner of a BMW with 30 profile run flats.

You cant win, they will break wheels, I tried a different set of wheels and broke 3 of them in under a year.

Only option is getting something with a bit more sidewall height and give.

See if you can find the size down from the same model, then it will still look OK.

[impprobable]

When I worked in Zambia the locals used to joke " you can spot a drunk driver easily because they make no attempt to avoid potholes "
I hope this helps....

[KTMsm]

In the old days I used to increase wheel size to make cars more sporty

But for the last 20 years I generally decrease them by an inch or two to get some comfort

As long as smaller wheels clear the brakes then that's fine and yes you increase the profile to maintain the same rolling radius - lots of online tyre calculators for this reason

[joropug]

I have a 2013 c class on 18 inch AMG wheels and Goodyear eagle f1s. The car is on 86k and no evidence of welds.

Perhaps your wheels are aftermarket reps.

My tyres are:
2 x Goodyear Eagle F1 Asymmetric 5 225/40 R18 Y (92), Reinforced, Asymmetrical
2 x Goodyear Eagle F1 Asymmetric 5 255/35 R18 Y (94), Reinforced, Asymmetrical

Edited by joropug on Wednesday 4th August 11:19

[Swervin_Mervin]

Are you on run flats?

[otolith]

Does this give you the range of tyre/wheel sizes fitted as OEM to your car?

https://www.michelin.co.uk/auto/browse-tyres/by-ve...

[Pica-Pica]

OP. In truth you need a sidewall (free) height of at least 100mm, ideally towards 110 or 120.
225/40 is 225x0.4, so 90mm sidewall free (unloaded) height. I went from that to 225/45 (so 225x0.45=101mm. That was the best I could do on my BMW335d. My rears went from 255/35 to 255/40
Try here to see what will give the same rolling circumference (RC) as your current wheel and tyre set up, but check they will fit over your brake calipers.
http://www.wheelcalc.com/

[SuperPav]

As others have said, go down a wheel size to add some sidewall.

But before you do that, are you 100% sure you're on genuine Merc wheels and not replicas or aftermarket wheels? If they're not genuine merc wheels, that would be why they keep cracking. The testing/standards of OEM wheels result in them being much much more robust than 99% of the aftermarket ones (some specific rally wheels excluded).

[Dog Star]

SuperPav said:

But before you do that, are you 100% sure you're on genuine Merc wheels and not replicas or aftermarket wheels? If they're not genuine merc wheels, that would be why they keep cracking. The testing/standards of OEM wheels result in them being much much more robust than 99% of the aftermarket ones (some specific rally wheels excluded).

I totally disagree - as soon as I saw the title of this thread I thought to myself "I bet it's a Merc". They're notorious for it on bigger rims.
In fact I wouldn't be surprised if aftermarket replica jobbies were stronger, they usually look similar but are a lot heavier.

[Paddymcc]

Had problems a few years back with a CLS and cracked 19" AMG III rims. Went through 2 sets before chaging to aftermarket alloy wheels and never had a cracked wheel again. The Mercedes was the only car ive ever experienced cracked wheels driving the same roads to work in various cars with 19" and 20" wheels.

Im currently driving a E Class Estate with 17" wheels and have not suffered any cracked alloy wheels.

My advice would be go good quality aftermarket if you wish to keep the size at 18" or 19" or if you wish to go OEM and increase the comfort go for the Mercedes 17" wheels. You would find a set of those on facebook marketplace.

[KTMsm]

My wife's Jag on 18's punctured 2 sidewalls and cracked one wheel on potholes so I downgraded to 17"

It happens so frequently that I sold the remaining 3 individually on ebay, for a very good price

[ettore]

My old 535D on runflats went through 5 (OEM) wheels during the time I had it, so it’s not unique to Mercedes.

If only they were the only things that went wrong with it!

Edited by ettore on Wednesday 4th August 15:46

[thsale]

Thanks for all the replies! Its really helpful.

I have been doing some research, but firstly, just to say I think the wheels are genuine although I can't be sure. I purchased the car in 2018 and the wheels were already on. They are black and silver and marked with 'AMG'. Is there anyway to check so I can be sure?

They are not run flats.

I like the idea of moving to a 17" wheel I think. As said, I have a Mercedes C Class S204 Estate. Looking online at genuine mercedes wheels, for example, it says the front wheels as: 7.5Jx17 ET47 and the Rear Wheels: 8.5Jx17 ET58. Does this sound correct?

So tyres would be 225/45/R17 for the front and wheels of 7.5j and the rears would be 255/40/R17 with wheels at 8.5j?

Thanks again for help!

[Pica-Pica]

thsale said:

Thanks for all the replies! Its really helpful.

I have been doing some research, but firstly, just to say I think the wheels are genuine although I can't be sure. I purchased the car in 2018 and the wheels were already on. They are black and silver and marked with 'AMG'. Is there anyway to check so I can be sure?

I like the idea of moving to a 17" wheel I think. As said, I have a Mercedes C Class S204 Estate. Looking online at genuine mercedes wheels, for example, it says the front wheels as: 7.5Jx17 ET47 and the Rear Wheels: 8.5Jx17 ET58. Does this sound correct?

So tyres would be 225/45/R17 for the front and wheels of 7.5j and the rears would be 255/40/R17 with wheels at 8.5j?

Thanks again for help!

8.5j sound right for 255, for 225 then usually 8 or maybe 7.5” works. There is a site that states what tyres for what rim, if I find it I’ll post it.

[SuperPav]

Dog Star said:

I totally disagree - as soon as I saw the title of this thread I thought to myself "I bet it's a Merc". They're notorious for it on bigger rims.
In fact I wouldn't be surprised if aftermarket replica jobbies were stronger, they usually look similar but are a lot heavier.

I take it back then! my experience is mainly with some other brands, perhaps Merc are a bit rubbish in this regard.

[InitialDave]

thsale said:

So tyres would be 225/45/R17 for the front and wheels of 7.5j and the rears would be 255/40/R17 with wheels at 8.5j?

That sounds about right when sizing down from what you described in your first post, yes.

If you're not bothered about having the nicer appearance of alloys, and you can get them in the right size,steel wheels donate the advantage that they'll bend rather than crack.

[Pica-Pica]

InitialDave said:

thsale said:

So tyres would be 225/45/R17 for the front and wheels of 7.5j and the rears would be 255/40/R17 with wheels at 8.5j?

That sounds about right when sizing down from what you described in your first post, yes.

If you're not bothered about having the nicer appearance of alloys, and you can get them in the right size,steel wheels donate the advantage that they'll bend rather than crack.

Indeed, I wish someone would promote decent looking steeliness more. My last two previous cars, I deliberately had steel wheels, I have seen cracked alloys on test tracks. On my previous E36, I bent a steelie when going over an unlit divider kerb. Just hammered it back into shape at home (didn’t even take the tyre off, just used a 2 pound club hammer). Oh, unless you pay a fortune, steels are usually a bit lighter than alloys, it’s all a con, really.