225/45 on a 7J rim?

Author
Discussion

havoc

Original Poster:

27,701 posts

216 months

Friday 22nd November 2013
quotequote all
Is it too wide or not?

Seen conflicting reports on the web - some saying no problem, some saying you'll get excessive sidewall flex under load (not desirable).

If it helps, it's for winter tyres...

Cheers,

Martin.

GAjon

3,544 posts

194 months

Friday 22nd November 2013
quotequote all
No expert but, I would venture a bit to wide.
I run 225 x 50 x 15 on the rear of my TVR on an 8"J rim and have run 235 but would say that was on the limit for 8".

Mroad

827 posts

196 months

Friday 22nd November 2013
quotequote all
The rule of thumb is the rim needs to be 90% of the tyre width with a +/- 1/2in leeway either side.
225/25.4 = 8.86
8.86 x 0.9 = 7.97
So a 225 should ideally be on an 8in rim but 7.5in or 8.5in would be OK.

Ideally check with the tyre manufacturer, they should list the range of rim sizes that are acceptable.
Up to you if you go outside their recommendations but if it's used on the road then don't forget insurance implications.

ging84

7,828 posts

127 months

Friday 22nd November 2013
quotequote all
what is this rule of thumb?

without taking into account the profile it seems utterly pointless
if you do that calculation on a lot of wheels with a higher profile it will come out saying the rim is too small

Monty Python

4,796 posts

178 months

Friday 22nd November 2013
quotequote all
ging84 said:
what is this rule of thumb?

without taking into account the profile it seems utterly pointless
if you do that calculation on a lot of wheels with a higher profile it will come out saying the rim is too small
Surely the profile only becomes an issue if you change the diameter of the wheel?


jagnet

3,982 posts

183 months

Friday 22nd November 2013
quotequote all
My Saab Aero uses 225/45/17 XL tyres on the original 7" wide ALU39 rims and yes, you do get a little sidewall flex under load - more noticeable on the winter tyres. On the plus side it does help reduce harshness from road imperfections. An 8" rim would be better for keeping a straighter sidewall.

havoc

Original Poster:

27,701 posts

216 months

Friday 22nd November 2013
quotequote all
Bugger. Can get a set of lightly-used winters for a good price in 225/45/17...would save me perhaps a couple of hundred quid.

BFleming

3,152 posts

124 months

Friday 22nd November 2013
quotequote all

Ennoch

371 posts

119 months

Friday 22nd November 2013
quotequote all
Theoretically it's possibly a bit touch/go but the realistic difference in tyre width over a 215 section (of which you'll find plenty on 7" rims)is minimal. While there's a lot of hearsay on the internet I've done close to 200k with 225's on 7" rims across a couple of cars and never once had issue or even viewed it slightly as a problem. As long as the tyres don't rub on your arches etc you'll be just fine. I've actually just fitted a set of 225 winters myself to the Scoob as the standard 215/45 rubber is a bit on the weedy side, and 215 rubber is like rocking horse st. Check the speedo accuracy (negligible on such a small change) and the rubbing, and crack on.

havoc

Original Poster:

27,701 posts

216 months

Friday 22nd November 2013
quotequote all
Mroad said:
Ideally check with the tyre manufacturer, they should list the range of rim sizes that are acceptable.
Up to you if you go outside their recommendations but if it's used on the road then don't forget insurance implications.
Checked that, thanks - 7.5J to 9J!

frown

underphil

1,209 posts

191 months

Friday 22nd November 2013
quotequote all
depends on the tyre - many of the manufacturers have tables on their websites with approved rim sizes listed for each tyre size

http://www.toyo.co.uk/tirefinder

lists 7.5 as ideal with 7 - 8.5 being approved for 225/45R17