Edna Aero tyre sizes

[phoenix]

WIS says that Aero model Ednas came with 235/45/17 only, but the 2.3T  could have those or 225/45/17.

Is there any reason that anyone can think of that I shouldn't fit 225s to an Aero- I ask because I have two new 225s in stock so to speak and also 225s are somewhat cheaper.

[sgould]

I think it was just a gearing issue.  Cheaper to fit bigger tyres and wider wheels than have a change of differential ratio. 225 will be fine.

[sgould]

Just checked the WIS and 225/45 17 94 XL  and 215/55 16 are approved for the Dame as winter sizes.

[phoenix]

The gearing is only 1.4% different between 225 and 235. I've decided to go for 225s- will have Michelin Cross climates all round. Just need to get the rear rose bushes done now...

[fka]

I've been looking at the Continental All Season Contact tyres and they don't manufacture a 235 45 17 but do do a 225 45 and 225 55..
As the Edna ALU 62 wheels are 7.5", wouldn't fitting a 225 tyre mean the tyre is stretched slightly to fit the rims, which would further reduce the aspect ratio of the tyre? To maintain the same sidewall depth would a 225 55 tyre work?

[wrighar]

7J rims had a max width of 225,  The later 7.5J rims could take 235's

There is a range of section widths per J width, often 40 or 50   (so maybe 195-235 on a xxx/45*17 7.5J rim)

[fka]

As noted above, there's a difference in tyre wall depth between a 225 45 and 235 45 (4.6mm). I could be wrong but I'm assuming if you fit a 225 45 tyre to a 7.5" wheel, then the tyre wall depth would effectively be less again than if a 225 45 was fit to a 7" wheel, as the beads of the tyre are pulled a half inch further apart?
I think a 225 55 would be too much but a 225 50 gives a tyre wall depth about 7mm more than a 235 45. And if I'm right, then on a 7.5" wheel, how much farther would the wall depth be reduced?

[sgould]

There's a fitment chart in the Bridgestone databook I downloaded sometime ago.  This is their info for 45 and 40 profile tyres...

[wrighar]

I believe the Bold 'J's in the list above are the recommended J width, the others are acceptable alternates.

[carrera]

The width of the rim doesn't make any real difference to the rolling diameter. 1/2 inch is only 6mm deflection at each mounting point, do a bit of trig if you want to evaluate the negligible difference.

I believe 225/45/17 are more readily available, which will also mean cheaper.

I concur with the 1.4% difference in rolling radius mentioned above. My winter rims have 205/55/16 on them which work out to be 0.4% shorter geared in theory than standard.

[fka]

And I guess 7.5" is still less than 235 or 225mm, so you're not "stretching" the tyre at all!
Thanks all for the info.. I'm just concerned about the difference in ride quality of the shorter wall depth on the 225 and (an less importantly.) whether the 225 will look noticeably smaller in the wheel arch.

[sgould]

When you are looking at rolling diameter, don't forget that there's about 3% to 4% difference between a new tyre and a worn out tyre...

[phoenix]

I've been really happy with the Cross Climates in 225. Ride and handle well, and noise is quite low too.

[fka]

Thanks Mark, and fair point Will!
I've still got bags of life left in the rears but since getting the stage 3 map the fronts don't have a huge amount of life left in them.
As posted before, I've always had a bit of judder pulling off in 1st (number of people now have told me this is relatively normal for the 9-5) and with the remap, it's now a very fine line between pulling off with judder, smoothly or spinning the wheels, especially in the wet 
Funds allowing, I'll be changing all 4 when the fronts are done.

[collywobble]

For 225/45/17 tyres WIS states they should be W speed rating, 94 load rating AND XL rated
235/45/17 tyres only need to be W speed rated and 94 load rated, not XL.