[lowkick]

Hi

Has anyone tried fitting a 245/40/18 in replacement of the 255/35/18 for rears on e90/91 m sport? sorry if this sounds like a lame question but just wanted to seek some answers.

thanks people!

[lemonukas]

Originally Posted by lowkick

Hi

Has anyone tried fitting a 245/40/18 in replacement of the 255/35/18 for rears on e90/91 m sport? sorry if this sounds like a lame question but just wanted to seek some answers.

thanks people!

I don't think is a problem just leave same height 35%

[parapaul]

I'm sure some people run 245/40/18 all round as a square winter setup on staggered wheels with no issues.

Why are you asking, out of interest?

[Bungle009]

245/40/18 will be a bigger rolling radius. If you want/have to go 245 then I would suggest 245/35/18.

[lowkick]

cheers guys!

All done, I have 9.5 J rears and 20 mm spacer and put 245 40 18 on today.
No problem at all. Slightly stretched but looking very good.

[doughboy]

Lowkick,

Your new tyres have a 2.7% greater rolling radius, so your speedo will be 2.7% low.

[lowkick]

Originally Posted by doughboy

Lowkick,

Your new tyres have a 2.7% greater rolling radius, so your speedo will be 2.7% low.

Yup, in theory when the tyre isn't stretched;-) But since it is, i think I'm closer than 2.7%

[doughboy]

Stretching the tyre won't make it smaller..

It just pulls the bead outwards a little by movement in the sidewalls.

The main tread carcass will remain exactly the same rolling radius, the carcass reinforcements won't allow any change in tread circumference.

[lowkick]

cheers doughboy. I'm very careful with speed cameras so I am not too worried. Comfort factor was by far more important to me. Sooooooo tired of 19's with 30 wall.

[HighlandPete]

Originally Posted by lowkick

cheers doughboy. I'm very careful with speed cameras so I am not too worried. Comfort factor was by far more important to me. Sooooooo tired of 19's with 30 wall.

But is there much difference to ride comfort? The slightly stretched tyre on a maximum sized rim will mean you have compromised comfort to some degree, simply by using a narrow section.

To gain comfort you'd normally opt for a wider section of the same profile, or even wider on a lower profile, to hold a similar Rolling Diameter.

HighlandPete

[lowkick]

Well, I can see a big difference between 255 35 18, which I took off and replaced by 245 40 18. Perhaps I am wrong but to me width (Ive tried 255 on both 19 and 18 with 30 and 35 wall) made no difference, profile however did. I am not a specialist but a taller rubber means less bumpy ride to me.

I thought of staying with 255 but putting a 40 wall would affect the speedo by 4% in comparison to 2.7% with a 245 tyre.
Ive been driving in London today (we all know the quality of roads and the amount of potholes in the capital) and the ride is much, much better than on 255 35 18. To me it is:-)

Photos attached to get an idea of the look.

[HighlandPete]

Originally Posted by lowkick

Ive been driving in London today (we all know the quality of roads and the amount of potholes in the capital) and the ride is much, much better than on 255 35 18. To me it is:-)

You've obviously got a better ride and well pleased, that's what matters. Will you be moving up a profile on the front, to balance out the ride and get the same wall height?

HighlandPete

[lowkick]

nope, staying with 225 40 18

[UDM_2012]

I have been thinking about doing the same thing, looks like it works well.

[Gate7]

this is exactly what I was looking for, i'm also thinking of downgrading from 255/40/18 rear to 245/40/18s...

Much more tire options in 245/40 series...

[Cero ceto]

I run 225's on all four corners on my winter staggered wheels with no problems!