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Thread: F355 - OEM Fitment 225/40/18 front, 265/40/18 rear. Mismatched profiles?

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    Default F355 - OEM Fitment 225/40/18 front, 265/40/18 rear. Mismatched profiles?

    Standard tyres 225/40/18 at the front, 265/40/18 at the rear. As most will know, the profile is a percentage of the width, therefore the profile is larger on the rear compared to the front? Any ideas why?

    I ask as there seems to be a great selection of tyres of size 265/35/18 and was thinking of going that route?

    Any thoughts?

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    Quote Originally Posted by Mark999 View Post
    Standard tyres 225/40/18 at the front, 265/40/18 at the rear. As most will know, the profile is a percentage of the width, therefore the profile is larger on the rear compared to the front? Any ideas why?

    I ask as there seems to be a great selection of tyres of size 265/35/18 and was thinking of going that route?

    Any thoughts?
    I wouldn’t really call the profiles mismatched as they are the same %
    You will have lower gearing, poorer ride, the rear will sit lower, nose up will do wonders for the aerodynamics at speed, slightly change your caster angle and almost certainly be detrimental to your handling.
    Unless you go 35% on the front as well the tyres will behave differently adding to the above. The front is low enough anyway.
    Bad idea in my view.
    Get some Michelins
    Last edited by Ian355; 25-05-2022 at 07:36 PM.

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    Thanks for coming back to me. Profile is a percentage of the width, ie 40% of 265 will be a great profile than 40% of 225. But as you suggest, this must be by design so I'll leave it alone. Just really limits the tyres that are available, most modern tyres are not produced in that size.

    Which model of Michelin are you recommending? I've got Sport 4s on another car, really like those, but again, not available in these sizes.

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    If they fit the rim width you could perhaps try 295/35 x 18 as they give a very similar overhaul diameter.
    Going for a lower profile with the same 265 width tyre will lower your gearing so the mileometer will read high as will your speedo.
    Frankly I would try and get the OEM size.
    "When Lance "cries" on Oprah , spare a thought for all of those genuine people who walked away with no reward just shattered dreams. Each one of them is worth a thousand Lances"

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    Its actually the front tyres I need to replace, but trying to think ahead with a view of matching the full set when the rears need replacing, ie buying a make/model that I know I can get for the rear later on. Choice for the rears, in any sizes from 265-295, is really limited. You can get a 275/35/18 in a Michelin PS4, you can then get a 235/40/18 in the same. In the US it seems quite common to go up to a 235 on the front, also been advised it can improve some of the steering feel and reduce some of the lightness in the steering you get with the 225, that makes sense. So I'm definitely tempted to put 235's on. Maybe I should just get the best tyres I can for the front and cross the bridge for the rears when I need to replace them.

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    Quote Originally Posted by Mark999 View Post
    Its actually the front tyres I need to replace, but trying to think ahead with a view of matching the full set when the rears need replacing, ie buying a make/model that I know I can get for the rear later on. Choice for the rears, in any sizes from 265-295, is really limited. You can get a 275/35/18 in a Michelin PS4, you can then get a 235/40/18 in the same. In the US it seems quite common to go up to a 235 on the front, also been advised it can improve some of the steering feel and reduce some of the lightness in the steering you get with the 225, that makes sense. So I'm definitely tempted to put 235's on. Maybe I should just get the best tyres I can for the front and cross the bridge for the rears when I need to replace them.
    If my maths are right then the sizes in PS4 you are suggesting will give your car almost 14 mm nose high attitude which cannot be good.
    I’ve just put a set of PS4s on my 355 in original sizes. Previously I had Pzero then Bridgestone. Pzero seemed better than the Bridgestones around a track but the Michelin seem more forgiving than both on the road.

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    Quote Originally Posted by Ian355 View Post
    If my maths are right then the sizes in PS4 you are suggesting will give your car almost 14 mm nose high attitude which cannot be good.
    I’ve just put a set of PS4s on my 355 in original sizes. Previously I had Pzero then Bridgestone. Pzero seemed better than the Bridgestones around a track but the Michelin seem more forgiving than both on the road.
    Going from a 225/40/18 to 235/40/18 increases height by just 4mm, so it's negligible.

    Can I ask where you sourced PS4s in OEM sizes? I can only find PS4

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    Quote Originally Posted by Mark999 View Post
    Going from a 225/40/18 to 235/40/18 increases height by just 4mm, so it's negligible.

    Can I ask where you sourced PS4s in OEM sizes? I can only find PS4
    Yes but the 275/35/18s will drop the rear 9.75 mm so that gives a total of 13.75 mm. With the clearance under the car only about 100 mm then that 13.75 mm might have a significant effect on the air flow.

    PS4 s ( plural) which is what you seemed to be referring to? I did ask for PS4S but that’s what the car came back with. Rears came direct from Michelin, fronts from my local fitters normal supplier.
    I’m not so worried about ultimate dry grip now anyway, it gives me ear ache.

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    I nearly killed myself on a trackday at Goodwood by fitting 235 tyres on the front of mine. Changing ride heights front to back isn't just about clearance, you change the car's rake (angle) and weight distribution

    I'd also avoid switching from directional tyres on the front and Asymmetric at the rear, Ferrari spent an age getting the 355's handling spot on after all the (many would say unfair) criticism of the 348

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    Quote Originally Posted by F355GTS View Post
    I nearly killed myself on a trackday at Goodwood by fitting 235 tyres on the front of mine. Changing ride heights front to back isn't just about clearance, you change the car's rake (angle) and weight distribution

    I'd also avoid switching from directional tyres on the front and Asymmetric at the rear, Ferrari spent an age getting the 355's handling spot on after all the (many would say unfair) criticism of the 348
    The 235 made that much difference? It's only a 4mm change from 225, that change to the height of the car is less than the difference between a new tyre and a worn one.

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