Bigger width tires on C300 AMG LINE PLUS EDITION

[MR08AMG]

Hi all I have read the tires chart on the thread but unfortunately it does not answer my question/ worries. I was advised from the lad at Kwik fit to make sure and check with MB forums community considering the vast experience here of doing similar upgrades on tires.

my C300 AMG LINE PLUS EDITION tires spec:

Front:
Pirelli P ZERO/ MOE/ PZ4/ RUN FLAT
225/40/R19 93 Y

Back:
Pirelli P ZERO/ MOE/ run flat
255/35/ R19 96 Y

I want to increase tire width by 10 mm taking it to 265/35/19 on rear (being a rare wheel drive BHP 320 & not a 4MATIC) to increase the rear end grip and for bit more protection on the rims as well as upgrade to 245 on the front from 225 so 20 mm increase so no more understeer in the wet! I hit the tire last month at corner while turning and front tire tore a bit. The rims are 19 inches and aspect ratio is 40 in front and 35 at the rear so we we not changing any of that, keeping it all the same as it is just increasing the width.

Now quickfit technician we did a quick check turning the front wheels full rotation either side and it appears enough room so with bigger tires rubbing on wishbone should not be an issue, gentleman at quick fit who seemed quite knowledgeable assured me. He said that you can order in and we do a fitting and test and if any issues we can take out the new one and put old one back but hopefully it will be all ok which was quite reassuring guarantee in case they dont fit! But before ordering in he advised to check on forums as others have done the similar upgrade to absolutely make sure we good. So any advice form the rich experience here would be most helpful.

The tires I am looking to order are Merc OE x 4

Front: Michelin Primacy 3 245/40/ R19 98Y XL
Rear: Michelin Pilot SUPER SPORT 265/35/R19 (98Y) MO1

Another thing they are NOT MOE so the run flat for 30 odd minutes is not there but I am not fussed about that. The car is only used for daily locally commute to town, gym etc. If I am going long distance than M240i is used. Does merc cause any issues over it when taken in for servicing I wonder as I have a service contract with them ? They refused to put bigger width quoting me the standard manufacture line that they will only put exact same ones where as a new c43 is being sold today has the same rim and aspect ratio as my c300 and comes with bigger wider wheels so in my research as much as I could find it wont be an issue at all just increasing the width by 10 mm at the rear and 20 mm in front.

Please could u advice if you got similar upgrade and share your experience any issues etc. Thanking you all in advance. Cheers all.

 

[Srdl]

Can’t specifically answer your question but I have never seen the words “Kwik Fit” and “knowledgeable” used together before!

 

[Blobcat]

Keeping the aspect ratios the same as original means the new front tyres will be 2.3% larger and the rears 1.2% larger. That difference between axles will likely lead to ABS and traction control issues as the speed sensors detect a difference between the axels.

Use any of the tyre size comparison sites and they’ll show you the difference and how it will affect the speedo reading.

You can go with pretty much anything that’s written in the manual or fuel flap. If you deviate from that your insurance will need to be advised.

 

[LostKiwi]

More width does not equal more grip. It just changes the shape of the contact patch, increases rolling resistance and possibly make the care more fidgety.
Likewise increasing front width will not reduce understeer 8n the wet - if anything it will increase it. Wider tyres are more prone to aquaplaning than narrow ones.
On the front 245/35/19 is the correct MB C63 fitment not 245/40/19. That would give a 1.3% error in the wheel speed which with 265/35/19 rears giving a -1.05% error gives a total front yo rear error of 2.35% which may upset ABS, reaction control and cruise. A 40 profile front reduces the error but is not a standard MB size for your car and prove problematic with insurance.
If it's a lease car or PCP it may invalidate your agreement.
Finally, you will need to inform insurance as it's a modification.

Frankly your benefits of doing it are minimal and it could create a world of pain.

 

[Rotorhead500]

Also, you can't really compare the C43 fitment as it'll have suitable alloy size (including width & offset) to accommodate specified tyres. (Unless you're planning a wheel change too).

 

[brandwooddixon]

Be cautious of using a static check to determine whether tyres will foul body work or suspension on the front when turning.
All tyres will flex under cornering, by the same token they expand in diameter by a small margin as speed of rotation increases.

I would suspect that running run flat tyres will have a bearing on any understeer that you're experiencing.

Also Pirelli P Zeros aren't what they used to be, I would suggest looking at other tyres, I find the Continental SportContact 7 and 6 to be good. Michelin Super Sports are very grippy but they don't last long (around 6k miles in my experience).

 

[Woodleigh]

Also Pirelli P Zeros aren't what they used to be,

Agreed, PZero's gave me nothing but trouble....tyre skipping and excessive wear on the shoulders.
Continentals are the way to go IMO.

 

[MR08AMG]

More width does not equal more grip. It just changes the shape of the contact patch, increases rolling resistance and possibly make the care more fidgety.
Likewise increasing front width will not reduce understeer 8n the wet - if anything it will increase it. Wider tyres are more prone to aquaplaning than narrow ones.
On the front 245/35/19 is the correct MB C63 fitment not 245/40/19. That would give a 1.3% error in the wheel speed which with 265/35/19 rears giving a -1.05% error gives a total front yo rear error of 2.35% which may upset ABS, reaction control and cruise. A 40 profile front reduces the error but is not a standard MB size for your car and prove problematic with insurance.
If it's a lease car or PCP it may invalidate your agreement.
Finally, you will need to inform insurance as it's a modification.

Frankly your benefits of doing it are minimal and it could create a world of pain.

Hi there mate many thanks for your valuable input. Indeed at the front 245/35/19 is the correct fit for MB c63 standard . I wonder why on my C300 AMG edition they put 225/40/19 because at the rear they kept the aspect ratio same as c63 which is 35 so my C300 rear tires are 255/35/19 . So what could be the reason MB put 40 aspect ratio in front and kept rear at 35 ? If they followed same as C63 fitment would that make a difference i wonder ? cheers

 

[MR08AMG]

Also, you can't really compare the C43 fitment as it'll have suitable alloy size (including width & offset) to accommodate specified tyres. (Unless you're planning a wheel change too).

Hi there mate thanks for your input. I dont know much tech details regd this but I simply thought well if I got 19 inch rims and C43 got 19 inch rims so strapping the bigger tires on mine wont be an issue but looks like it will be with the other systems. cheers

 

[MR08AMG]

Keeping the aspect ratios the same as original means the new front tyres will be 2.3% larger and the rears 1.2% larger. That difference between axles will likely lead to ABS and traction control issues as the speed sensors detect a difference between the axels.

Use any of the tyre size comparison sites and they’ll show you the difference and how it will affect the speedo reading.

You can go with pretty much anything that’s written in the manual or fuel flap. If you deviate from that your insurance will need to be advised.

Many thanks for your input matey. I did a comparison on tire ratio and all on different sizes vs mine and this came up. Now my brain is ADHD and I have math dyscalculia so my brain works maths differently in a work it works for me to tackle it and understand the best it can. thanks


so according to the calculator my C300 spec is:

Comparing 225/40R19 against 255/35R19

Width Profile Rim Diameter Diameter
Tyre 1 225 40 19 662.6mm
Tyre 2 255 35 19 661.1mm
FITMENT OK!
The percentage change is 0.23% and the circumferece change is 1.5mm.

and below are different specs

Comparing 245/40R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 245 40 19 678.6mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 1.57% and the circumferece change is 10.5mm.


Vs

Comparing 245/35R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 245 35 19 654.1mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 2.1% and the circumferece change is 14mm.

Vs

Comparing 225/40R19 against 265/35R19
Width Profile Rim Diameter Diameter
Tyre 1 225 40 19 662.6mm
Tyre 2 265 35 19 668.1mm
FITMENT OK!
The percentage change is 0.82% and the circumferece change is 5.5mm.

 

[Rotorhead500]

Hi there mate thanks for your input. I dont know much tech details regd this but I simply thought well if I got 19 inch rims and C43 got 19 inch rims so strapping the bigger tires on mine wont be an issue but looks like it will be with the other systems. cheers

Width of alloy will determine if the tyre sits on the rim correctly - too narrow for the tyre and the tyre either won't seat & seal properly, or it will roll off in a corner; too wide (the dreaded "stretch" look, or worse) and the tyre won't seat and seal. The offset determines how/where the wheel sits within the wheel arch - if outside of manufacturer's tolerances, can either rub on body work and/or suspension & chassis components.

If it helps, my W204 C63 (previous gen C-Class), was on 235/35R19 front and 255/30R19 rear, and I didn't have a problem with understeer in that car!

 

[mioba]

Any mon factory mod needs to be provided to the insurance co. They go by the vin if in an accident. They ask this question every renewal.
So if you are in an accident, they will check and if your tyres/wheels not spec - insurance invalidated.

 

[MR08AMG]

Any mon factory mod needs to be provided to the insurance co. They go by the vin if in an accident. They ask this question every renewal.
So if you are in an accident, they will check and if your tyres/wheels not spec - insurance invalidated.

Tfhanks for your input mate. so when you tell them about say a MAP or tire spec change do they just make a note or charge you extra for it because a change was made ? Would like to know what experience comrades here have with insurance companies on these matters. cheers

 

[MR08AMG]

Comparing 255/35R19 against 255/35R19

	Width	Profile	Rim Diameter	Diameter
Tyre 1	255	35	19	661.1mm
Tyre 2	255	35	19	661.1mm

FITMENT OK!
The percentage change is 0% and the circumference change is 0mm.

Hi all so looks like AMG gods listened to my sorrow over this and while I was in the driveway getting stats from tires this evening for all you nerds and geeks here my neighbors son who is always friendly came in to visit family in his always roaring majestically pocket rocket with 4 x 2O inch wheels and he saw me messing with my tires and only than I found out he is a mobile tire fitter himself and he works for blackcircles! As he offered to help I explained all to him and he said as you have 255 on the rear so why dont you put the same sizer 255 in front but drop the aspect ratio in front from current 40 to 35 matching the rears which is 35. So basically 255/35/19 all across.

He suggested Michelin Pilot Sport 4s and I too had them in mind in my couple of choices in brand and model so I was well pleased to hear that. He said 255 will look rather good in the front matching the rear as I wanted bigger heavier looking tires and they good for all weather conditon. Ofcourse there is no change in this setup but I did the calculator to workout the diameter which is 661.1mm.

He also quickly called his mate to check who too got different spec width supplied from MO when he got his C63. His fronts were smaller width and rear bigger so his was a mismatch too direct from Merc. His mate swapped them later in this manner keeping all 4 same and its working great. He get 30-40 percent discount on black circles staff discount so he said he can get them really cheap on staff discount for me and he will bring them here and fit them. Happy days!

So what does the comrades here think of this fitment ? Please share your thoughts. Plus I found them on MO1 fitment so Merc cant say they unofficial when I take them for servicing next time as they did say when I emailed them that they got to be MO approved if I was to get them done outside so that keeps them happy.. There is literally no change on rear and mine pulls power from rear anyway so going forward its just change of brand/model. The idea of putting 255 on front will make them look great he said as I wanted bigger tires. Matching what comrades said to me here he too said that due to rim beads sizing we should not put bigger tire as advised here due to my J sizing being smaller to handle 265 so we not messing with that which you all said cause all sorts of issue. I had originally thought of putting 265 on rear from 255.

4 x 255 all across in Michelin Pilot Sport 4s now I am exited!
He is going to message me tomorrow for price after his discount.
I am really hoping I get a green thumbs up from you all on this and no trouble news. thanks you all.

 

[rorywquin]

Agreed, PZero's gave me nothing but trouble....tyre skipping and excessive wear on the shoulders.
Continentals are the way to go IMO.

I've only ever had PZeros on my SLK (40k miles) & recently sold SL (25k miles) and no problems at all.

 

[Gazwould]

People are still incorrectly using these tyre wheel calculators for % / mm increases even seasoned forum veterans can get caught out as this is what they have been saying for years and all they know .

Tyres are not the width and aspect ratio you think they are !

What happens with a calculator Vs real world can be massively different .

Best stick with the manufacturer recommended sizes , if a wider tyre is preferred find which manufacturer !

 

[ioweddie]

go for goodyears...

 

[JBell]

Hi there mate thanks for your input. I dont know much tech details regd this but I simply thought well if I got 19 inch rims and C43 got 19 inch rims so strapping the bigger tires on mine wont be an issue but looks like it will be with the other systems. cheers

But the C43 has wider bodywork as well to cater for the wider wheels / tyres

 

[MR08AMG]

People are still incorrectly using these tyre wheel calculators for % / mm increases even seasoned forum veterans can get caught out as this is what they have been saying for years and all they know .

Tyres are not the width and aspect ratio you think they are !

What happens with a calculator Vs real world can be massively different .

Best stick with the manufacturer recommended sizes , if a wider tyre is preferred find which manufacturer !




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My good noble man many thanks indeed this is so helpful in decision making for someone who wanted a bigger tire looks as I already called Merc service and the tire dept guy who left message for me had left as it was at so I am going to be asking him on monday to book me an app next week to put all the same as they are 255 at the back and 225 in front from the factory so no change just swapping Pirellio Pzeros to MPS4S and they come with MO1 fitment so like u said just the brand change & it achieves the enhancement I am looking for. I am going to tag in a post other 2 gentleman who raised a debate in the service provider of this tyre industry which is quite a serious ''SAFETY'' concern I would like to have a English debate shall we.. When I get to merc Centre next week I would love to see this difference there and will snap a picture like that excellent comparison. god speed to you. this spiffingly satisfies the objective I am looking for. This has been such a awful upgrade experience unlike I ever experienced.

The most sound advice came from car forums here where as thats something I see as a serious lack in salesmanship of the tyre service providers who lacks serious fundamental safety knowledge and cant give straight answers or telling wrong info and I have to check on my own and make sure. would it work would it not work would it be safe and thats their day job. I am many things one of that being a sports physiotherapist. I am one of the best sports physio in the country people rely on me to get back to game imagine I start people telling bend that way not that way when I am consulting someone and start giving wrong safety rehab advice but when I go to the shops professionals the useless tire sellers cant tell me no that will make it unsafe if u change size and that will be it as I would not want to pursue that upgrade anymore then how simple is that.

I am advising people with their bodies neck backs shoulders do this dont do that but when i go out to seek a service the tyre sellers cant do that and send me to forums and I being labelled idiot for not knowing things which are clearly safety which I reason as a tyre service provider they should know. what you told me here is what I reason is a tire sales key knowledge a tire salesman should know as fundamental basic because to answer cm question if someone asks hey I just want bigger tires for looks and he can tell me it will work or not atrocious safety advice. The good English service is dead.


Best stick with the manufacturer recommended sizes , if a wider tyre is preferred find which manufacturer !