Subaru Forester Owners Forum banner

Man, measured tire tread width/section width can vary a lot by manufacturer

2K views 9 replies 6 participants last post by  jstawgn 
#1 ·
Just a PSA...

With 17x7.5 ET48 Rota Torques, stock struts + Swifts on my 07 XT:
  • 245/45 Kumho Ecsta ASX fit with no issue.
  • 235/50 Cooper Zeon RS3-A heavily rub the struts in the rear.
The Coopers have the same listed section width as the Kumhos did (9.6") but they are visibly wider - it's hard to measure precisely, but I think the Coopers are at least 1/4 inch wider - certainly not what you'd expect from the specs!
These are both "UHP All Seasons" so it's apples to apples - I'm pretty sure the Kumhos are just relatively narrow for a 245.

I only went with 235/50 because 225/50 happened to be out of stock when DTD was running an online promo - I thought they would fit based on tire size calculators and the fact that 245/45 were not a problem.
I later found several threads where people have had issues with 235/50/17, so I don't recommend that size on an ET48 wheel unless you know that particular tire runs on the narrow side.

Luckily I had some 3mm spacers laying around - the Coopers now just barely clear in the rear (by 2mm or so), so I'll have to stay on top of my pressure and perhaps check to see if the camber can be adjusted next time I get an alignment. :smile:
 
See less See more
#4 ·
I really think it just comes down to the tire. I thought the same thing - overall diameter (height) is the same as stock, and 235 should be narrower than the 245 that I ran without issue. In this case, it just didn't work out that way - I think it's the combination of the height plus the width that put me on the strut.

It's possible the Swifts contribute to the problem as well, but mostly I attribute the rubbing to the width of the Coopers. Even at stock height I think you'd be awfully close to the struts with an ET48 wheel. And like I said if you have too much negative camber that would also make the problem worse - I don't think I do, but I can't remember where I had it set last time.
 
#7 ·
That would mean... should mean, that the Cooper tire would look great at 225/50!

Any chance they'd let you exchange the 235 for 225 when they're in stock? :confused:
I don't think they carry these in-store yet, unfortunately, only online, so there would be lots of shipping costs involved. Ultimately this is mostly my fault anyway, so I'm just going to make do. :smile:
I'm not crazy about using a spacer but 3mm is not too bad - I still have tons of bite on the lugs.
 
#9 ·
Youre telling me

I went from 275/35/18 on my 08 Sti to 285/35/18 and wow there is a difference. I checked the manf. specs as well but its a bigger difference then what they claimed.

Main thing is you gotta remember every tire brand and model sizes out differently...they all seem to fit different even if you had the same exact size Dunlop compared to a Yokohama and so forth
 
#10 ·
I have 235/50R17 Kumho Escta 4X on 17x8 ET47 with -1.0 rear camber and no rubbing.
The section width was 9.6 on 7.5" wheel so its about 9.8" on my wheel.

I almost went to 245/50R17 of the same tire but it would not fit.

Tires sizes are definitely different between each manufacturer or even between different product line.
If you know your clearance and alignment setting you could play with the spreadsheet on this link and measure your expected clearance.
 
You have insufficient privileges to reply here.
Top