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.

 

[markjay]

Welcome.

Are you planning to use wider tyres on the existing rims? If so, what's the rims' width (e.g. 9J or 9.5J etc)?

 

[markjay]

(Also, whatever you end up doing, don't forget to declare the modification to your insurer)

 

[Scooby_Doo]

You can't ( well you can , but it's wrong) increase tyre width and leave the aspect ratio the same. On the front your increasing the overall wheel/ tyre diameter by 16mm.The Kwikfit fitter knows shi*e.

 

[BTB 500]

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.

This is presumably a hybrid (C300e or C300de)? There's no C300 with 320 bhp AFAIK (unless tuned/modified of course).

As already mentioned if you increase the width and leave the aspect ratio the same then the sidewall height (and therefore overall diameter) will change, which is not good news. You could almost certainly improve wet grip and rim protection by just picking different tyres (make & model) in the stock sizes?

 

[Rigby]

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.

Hi, this is what I had on my W205 C250d 4MATIC AMG Line Estate with 19" Multispoke Rims

Front Axle: 225/40 R19 - 93Y - XL.
Rim: 7.5 Jx19 Item number: A20540113007X23
Tyre: Continental Sport Contact 5 - Runflat -
225/40 SSR MOE - Rim Protection (FR)

Rear Axle: 255/35 R19 - 96Y - XL
Rim: 8.5 J X 19 Item number: 20540114007X23
Tyre: Continental Sport Contact 5 - Runflat -
255/35 SSR MOE - Rim Protection (FR)

 

[DSM10000]

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.

To be blunt you seen to misunderstand some of the basic principles how tyres work.

Increasing the width of the front tyres will not automatically reduce understeer.

Suspension alignment , tyre pressure, tyre compound etc will all have a bearing plus how you are driving.

If Mercedes thought that your car needed these tyres then they would have supplied them as standard.

As others have said that you should not change tyre width without a change in the aspect ratio to keep the rolling circumstance between front rear matched otherwise you may cause the tractiom control , stability control and other safety systems to work less effectively.

 

[Bobby Dazzler]

Personally I would not change the sizes of the tyres; instead I would change the tyre manufacturer and type to a one which is suited to your car, type of driving and conditions.

Pirelli PZero are rarely well rated in the UK, and unfairly get slated as being a poor tyre. They’re not, they’re just designed for use as a high performance tyre in a relatively warmer climate and so they need heat in the tyres which is difficult to achieve and maintain on the road in a cooler climate, and especially in cold and/wet conditions.

Michelin Pilot Super Sport are good tyres, but you will find a similar issue, but for a different reason. As a high performance tyre with a relatively old design, the operating range is relatively narrow compared to modern tyres meaning that you may find that they’re also difficult to keep in the right temperature range on the road.

Both the Pzero and Supersport should be switched to a winter or all season tyre in the colder/wetter months as they will never be up to temperature even on a spirited drive. To expect them to perform to an acceptable level is asking too much, it’s like wearing ballet shoes to climb a mountain and then be surprised that they don’t perform:

You need to choose a tyre with wider and/or lower operating temperature range, not a wider tyre with lower profile! A Michelin Pilot Sport 4 S has a remarkably wide range for a high performance tyre. Or you could buy any tyre which is more road/comfort orientated and find that it performs better than a high performance tyre in every day conditions.

Ultimately the superduperist ultra high performance tyre - designed for warm dry weather - will perform very poorly when popping to Lidl to check out the centre aisle on a rainy Saturday morning in January, but taking the long route on the country lanes to enjoy the drive there and back. It will be absolutely awful.

If you have the right tyres for the conditions and - it’s still struggling with grip, understeer, etc - then there’s likely a problem (eg tyre pressures, geometry, etc) or you’re likely to be driving too quickly for the conditions.

 

[Kudly]

Personally I would not change the sizes of the tyres; instead I would change the tyre manufacturer and type to a one which is suited to your car, type of driving and conditions.

Pirelli PZero are rarely well rated in the UK, and unfairly get slated as being a poor tyre. They’re not, they’re just designed for use as a high performance tyre in a relatively warmer climate and so they need heat in the tyres which is difficult to achieve and maintain on the road in a cooler climate, and especially in cold and/wet conditions.

Michelin Pilot Super Sport are good tyres, but you will find a similar issue, but for a different reason. As a high performance tyre with a relatively old design, the operating range is relatively narrow compared to modern tyres meaning that you may find that they’re also difficult to keep in the right temperature range on the road.

Both the Pzero and Supersport should be switched to a winter or all season tyre in the colder/wetter months as they will never be up to temperature even on a spirited drive. To expect them to perform to an acceptable level is asking too much, it’s like wearing ballet shoes to climb a mountain and then be surprised that they don’t perform:

You need to choose a tyre with wider and/or lower operating temperature range, not a wider tyre with lower profile! A Michelin Pilot Sport 4 S has a remarkably wide range for a high performance tyre. Or you could buy any tyre which is more road/comfort orientated and find that it performs better than a high performance tyre in every day conditions.

Ultimately the superduperist ultra high performance tyre - designed for warm dry weather - will perform very poorly when popping to Lidl to check out the centre aisle on a rainy Saturday morning in January, but taking the long route on the country lanes to enjoy the drive there and back. It will be absolutely awful.

If you have the right tyres for the conditions and - it’s still struggling with grip, understeer, etc - then there’s likely a problem (eg tyre pressures, geometry, etc) or you’re likely to be driving too quickly for the conditions.

Spot on! Especially your last point about driving for (road and tyre) conditions.

 

[Rigby]

Pirelli PZero are rarely well rated in the UK, and unfairly get slated as being a poor tyre.

I had factory-fit PZero's (Summers) when I bought my W205 from new. Frankly, they were the worst tyre I have had; I was getting major issues with tyre skipping on full lock and excessive wear on the outer edges of the fronts. After complaining to Mercedes they fitted a new set of Contis FOC and never had another issue and I am now on my second set of Conti Contact 5's.

As an aside, I have Pirelli Winter SottoZero's on 18-inch rims and they are excellent; so much so that I was passing Range Rovers during the "Beast from the East"

18 Inch Winter Rims / M+S Run Flat Tyres

Front Axle: 225/45 R18 - 95H - XL.
Rim: 7.5 J X 18 M.B. Part Number: A20540111007X23
Tyre: Pirelli Winter SottoZero 3 XL - Runflat
25/45 R18 95H - M+S - MOE - Rim protection (MFS)

Rear Axle: 245/40 R18 - 97V - XL.
Rim: 8.5 J X 18 M.B. Part Number: A20540112007X23
Tyre: Pirelli Winter SottoZero 3 XL - Runflat
245/40 R18 97V - M+S - Rim Protection (MFS)

 

[MR08AMG]

Welcome.

Are you planning to use wider tyres on the existing rims? If so, what's the rims' width (e.g. 9J or 9.5J etc)?

Thanks mate Yes that was the plan but looking at the advice I have received here it does not look it as a sensible thing to do!
Rims width 19 inches

(Also, whatever you end up doing, don't forget to declare the modification to your insurer)

sure will do many thanks. cheers

 

[MR08AMG]

You can't ( well you can , but it's wrong) increase tyre width and leave the aspect ratio the same. On the front your increasing the overall wheel/ tyre diameter by 16mm.The Kwikfit fitter knows shi*e.

haha that quickfit fellow is here on this forum! Hope he is not reading this. He told me to join and check with the Merc mavericks! I am glad I joint. should have done years ago!

So from what you saying there that I cant leave the aspect ratio the same if width is increased so we can drop the aspect ratio in the front to 35. I dont mind. Is that a big job for the fitter I wonder ?

like for example standard c63 spec both front and back are 35 aspect ratio (Front tyres: 245/35/R19 Rear tyres: 265/35/R19
where as mine is Front tyres :225/40/R19/93Y Rear tyres : 255/35/R19/96Y so what if we drop it to 35 on front or that will cause a big mess in another way with other systems alignment and traction control ? cheers

 

[BTB 500]

You are looking to keep the overall diameter of the wheel plus tyre (AKA 'rolling radius', or 'rolling circumference') the same as stock. If the front & back are different then the wheels will be turning at different rates which will affect cruise control, ESP, etc. If they are the same but different to the stock measurement then your speedo (and odometer) will over or under read.

Plug the wheel/tyre details into any of the online calculators e.g. this one:

Tyre Calculator | AlloyWheels.com

Buy alloy wheels from AlloyWheels.com the biggest alloy wheel retailer! Free delivery, finance available, best prices guaranteed.

alloywheels.com

As mentioned though MB know a bit about setting cars up and it's unlikely you can 'improve' things by changing to non-standard sizes.

 

[MR08AMG]

This is presumably a hybrid (C300e or C300de)? There's no C300 with 320 bhp AFAIK (unless tuned/modified of course).

As already mentioned if you increase the width and leave the aspect ratio the same then the sidewall height (and therefore overall diameter) will change, which is not good news. You could almost certainly improve wet grip and rim protection by just picking different tyres (make & model) in the stock sizes?

Hi matey many thanks for your input. Yes sorry I should have mentioned in the first post its mapped by DMS.. top speed was delimited and it got to 321 bhp to be precise. its been running the map for over 2 years now. Rather incredible job they did. Made a huge diff from 260 bhp. Glad I drove to Southampton for it. Rear wheel drive full petrol.

Ok what if I tell you I shared a lie with you there which I told myself to convince MYSELF just to put fatter wheels
I really did not think slapping some fatter tires would be such an huge issue with the rest of the cars dynamics. So as rear two had their age ( did 7 K miles) and was due for change I was told at the MOT few months ago and now the front one ripped in the corner so I thought this is best opportunity to change all 4 and put fatter tires to make me happy. Men as a species are neither happy in bedroom nor in garages and we are so very accommodating unlike women that we dont even mind if ''things'' stick out!

So can I drop the aspect ratio in the front to 35 same as this c63 example i posted above all have all 4 x 35 aspect ratio and then would it work I wonder? My knowledge is limited on this I must confess. I tend to usually check with mod shops and local mates and from there. I always felt later I wanted bigger tires and T tech in saint Albans mod shop suggested me to put spacers on to make them stick out but I did research on it and found it was quite a dangerous idea so did not go with it and here we are.
Much appreciate you time with this. cheers

 

[Scooby_Doo]

haha that quickfit fellow is here on this forum! Hope he is not reading this. He told me to join and check with the Merc mavericks! I am glad I joint. should have done years ago!

So from what you saying there that I cant leave the aspect ratio the same if width is increased so we can drop the aspect ratio in the front to 35. I dont mind. Is that a big job for the fitter I wonder ?

like for example standard c63 spec both front and back are 35 aspect ratio (Front tyres: 245/35/R19 Rear tyres: 265/35/R19
where as mine is Front tyres :225/40/R19/93Y Rear tyres : 255/35/R19/96Y so what if we drop it to 35 on front or that will cause a big mess in another way with other systems alignment and traction control ? cheers

You got to look at it like a maths question:-
Front - 225/40 means that the height of the tyre is 40% of the width so for 225/40 height = 225 X 0.4 = 90mm
So your 19" wheels are 482.6mm dia + 90mm of tyre top & bottom giving you a total dia of 482.6+90+90 = 662.6mm
Front - 245/35 means that the height of the tyre is 35% of the width so for 245/35 height = 245 X 0.35 = 85.75mm
So your 19" wheels are 482.6mm dia + 85.75mm of tyre top & bottom giving you a total dia of 482.6+85.75+85.75=654.1mm
The difference in dia now is only 8.5mm which I think is fine.

Just had a look online and C63 Coupe runs 255/35 fronts ( gives you a tyre height of 89.25mm which is nearly the same as your 225/40) on 9J alloys and your Coupe runs on 225/40 tyres on 7.5J fronts, so your proposed 245/35 look a bit wide for 7.5J fronts. Life is never easy. Merc knows best.

 

[Scooby_Doo]

haha that quickfit fellow is here on this forum! Hope he is not reading this. He told me to join and check with the Merc mavericks! I am glad I joint. should have done years ago!

On this forum or not, he still not knowledgeable about tyres. I've put it a bit nicer this time.

 

[Smiley]

A kwik fit tyre fitter who does not know that increasing the width of a tyre whilst maintaining the same aspect ratio will increase the diameter of the tyre, and by inference, how to calculate the increase.
Whatever next.

 

[MR08AMG]

Personally I would not change the sizes of the tyres; instead I would change the tyre manufacturer and type to a one which is suited to your car, type of driving and conditions.

Pirelli PZero are rarely well rated in the UK, and unfairly get slated as being a poor tyre. They’re not, they’re just designed for use as a high performance tyre in a relatively warmer climate and so they need heat in the tyres which is difficult to achieve and maintain on the road in a cooler climate, and especially in cold and/wet conditions.

Michelin Pilot Super Sport are good tyres, but you will find a similar issue, but for a different reason. As a high performance tyre with a relatively old design, the operating range is relatively narrow compared to modern tyres meaning that you may find that they’re also difficult to keep in the right temperature range on the road.

Both the Pzero and Supersport should be switched to a winter or all season tyre in the colder/wetter months as they will never be up to temperature even on a spirited drive. To expect them to perform to an acceptable level is asking too much, it’s like wearing ballet shoes to climb a mountain and then be surprised that they don’t perform:

You need to choose a tyre with wider and/or lower operating temperature range, not a wider tyre with lower profile! A Michelin Pilot Sport 4 S has a remarkably wide range for a high performance tyre. Or you could buy any tyre which is more road/comfort orientated and find that it performs better than a high performance tyre in every day conditions.

Ultimately the superduperist ultra high performance tyre - designed for warm dry weather - will perform very poorly when popping to Lidl to check out the centre aisle on a rainy Saturday morning in January, but taking the long route on the country lanes to enjoy the drive there and back. It will be absolutely awful.

If you have the right tyres for the conditions and - it’s still struggling with grip, understeer, etc - then there’s likely a problem (eg tyre pressures, geometry, etc) or you’re likely to be driving too quickly for the conditions.

Bobby thanks for your valuable input mate. Well received.
I have checked for data from the tires and traction is rated AA and treadwear 280 and temperature is rated A. many thanks

 

[MR08AMG]

You are looking to keep the overall diameter of the wheel plus tyre (AKA 'rolling radius', or 'rolling circumference') the same as stock. If the front & back are different then the wheels will be turning at different rates which will affect cruise control, ESP, etc. If they are the same but different to the stock measurement then your speedo (and odometer) will over or under read.

Plug the wheel/tyre details into any of the online calculators e.g. this one:

Tyre Calculator | AlloyWheels.com

Buy alloy wheels from AlloyWheels.com the biggest alloy wheel retailer! Free delivery, finance available, best prices guaranteed.

alloywheels.com

As mentioned though MB know a bit about setting cars up and it's unlikely you can 'improve' things by changing to non-standard sizes.

Many thanks for your input matey. So I did a comparison on tire ratio and all on different sizes vs mine and this came up. Now my brain is ADHD build 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 thats why I cant work it in my head like comrades doing here if this increases and that increases than that too increases, that whole mental picture of it my frontal cortex cant visualize step by step as brain struggles to comprehend. as soon as its numbers. My apologies as I come across daft in math's department. Calculators helps with ADHD mind greatly.

The least change I can see is the bottom spec vs 1st spec which is what I got on right now so 1.5 mm vs 5.5 m is the least difference and that was achieved if I drop the front aspect ratio to 35 from 40. I dont know why MB kept 40 aspect ratio in front on mine and 35 on rear where as standard C63 for example is 35 in front and 35 in rear. What possibly could be reason or advantages for this mismatch MB did I wonder 40 in front and 35 rear. Thinking about it now perhaps 35 in front and back all the same would have been better you think ? Please share your thoughts. many thanks again.

so according to the calculator link you send me for 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.

 

[MR08AMG]

You got to look at it like a maths question:-
Front - 225/40 means that the height of the tyre is 40% of the width so for 225/40 height = 225 X 0.4 = 90mm
So your 19" wheels are 482.6mm dia + 90mm of tyre top & bottom giving you a total dia of 482.6+90+90 = 662.6mm
Front - 245/35 means that the height of the tyre is 35% of the width so for 245/35 height = 245 X 0.35 = 85.75mm
So your 19" wheels are 482.6mm dia + 85.75mm of tyre top & bottom giving you a total dia of 482.6+85.75+85.75=654.1mm
The difference in dia now is only 8.5mm which I think is fine.

Just had a look online and C63 Coupe runs 255/35 fronts ( gives you a tyre height of 89.25mm which is nearly the same as your 225/40) on 9J alloys and your Coupe runs on 225/40 tyres on 7.5J fronts, so your proposed 245/35 look a bit wide for 7.5J fronts. Life is never easy. Merc knows best.

Thanks for doing this for me matey much appreciate it. The thing is my brain is ADHD build 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 thats why I cant work it in my head like comrades doing here if this increases and that increases than that too increases, that whole mental picture of it my frontal cortex cant visualize step by step as brain struggles to comprehend as soon as its numbers. My apologies as I come across daft in math's department. The comrade here kindly provided a calculator so i worked different spec on it and have posted it.