Help me decipher car wheel numbers ...

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Batman

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Topic # 198967 29-Jul-2016 18:43

So I understand BCD/PCD, rim diameter, offset.

Now I have 2 questions

1 - Why does my wheel print say "7 1/2" inch rim width but my tape measure says 8.5" ?

2 - is centre bore relevant for modern vehicles?

Swype on iOS is detrimental to accurate typing. Apologies in advance.

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Reply # 1600982 29-Jul-2016 18:52

1. Where does it say 7 1/2? Is it "7 1/2 JJ"? Rim width is measured from inside the bead.

2. Very. These days it's the centre bore that holds the wheel, well, centred, as well as taking the weight. As opposed to the old days you'd make sure all the nuts were in their holes properly.

Edit, if I changed wheels to a later model rim on my old car, I'd have to use hub rings to take up the difference.

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Reply # 1600985 29-Jul-2016 18:58

blakamin:

1. Where does it say 7 1/2?

Subaru stock wheel.

Engraved on the wheel "18x71/2J"

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blakamin

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Reply # 1600989 29-Jul-2016 19:02

I just edited my first post.. It's measured from inside the beads.. So measuring from outside to outside will give you a larger number.

blakamin

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Reply # 1600991 29-Jul-2016 19:04

If you're looking at aftermarket rims, make sure they have the same or larger centre bore, and if larger, get hub rings.

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Reply # 1600996 29-Jul-2016 19:11

Ah ok. Maybe I'll search wheel width for particular tyre width ... trying to source a set of rims coz I managed to buckle 2 wheels over a large unsighted pothole ...

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blakamin

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Reply # 1600998 29-Jul-2016 19:14

joker97:

Ah ok. Maybe I'll search wheel width for particular tyre width ... trying to source a set of rims coz I managed to buckle 2 wheels over a large unsighted pothole ...

Most online tyre shops have a calculator for that biz.

What size tyres?

I know how you feel... I did the same in my last car. That's when I found out Fulton Hogan do roads here in Adelaide

blakamin

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Reply # 1600999 29-Jul-2016 19:19

Or a Suby forum...

I have this guide for my car, it'll give you a basic idea, but mainly aimed at BMW owners.

http://www.meeknet.co.uk/e31/timms_bmw_wheel_and_tyre_page.htm

EDIT: Actually, if you look down the bottom, the e31 - e32 bit is pretty much normal tyre widths.

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Reply # 1601001 29-Jul-2016 19:19

225 45 18 ...

thinking of 225 50 17 for more room for the next pothole ... !

don't want wider (need clearance for snow chains)

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Reply # 1601006 29-Jul-2016 19:24

225's will fit on a 7.5in rim. The profile (50) will change your speedo and possibly your guard clearance, but not by much. It seems Subaru fit fairly comfy tyres as standard!

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Reply # 1601055 29-Jul-2016 21:13

It came with Ferrari tyres (Potenza RE050A) ... rigid sidewalls ... wasn't comfortable at all! Maybe I'll look out for holes once I find wheels and tyres ... what tyres do you run on your beemer?

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Reply # 1601094 29-Jul-2016 22:04

I have 235/60 16s on it.. The ride is very comfy

On the one I wrecked the rims, 235 45 17.

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Reply # 1601100 29-Jul-2016 22:20

One person supports this post

those sound like formula 1 tyres

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Reply # 1602409 1-Aug-2016 18:08

Sorry for being a little OT but there are obviously some pretty knowledgeable folks here when it comes to wheels/tyres.
I took an Subaru Outback for a test drive and was a little surprised by a vibration / shudder most noticeably at between 75 and 95 km/h. Not worse or better under acceleration and nothing noticeable in tight turns so possibly not the CVJs. Online investigation suggested that the wheels may be out of balance, or the tyres out of round. As far as the out of balance goes there is no associated steering wheel shimmy but I am unsure as to how much direct connection there is these days between the steering wheel and the front wheels. I guess there is a possibility of out-of-round tyres, but it's not one I have struck before. My main concern is that if it's not the wheels then the next thing is an out of balance driveshaft.
So anyone (particularly Subie owners) have any comment about other possibilities of if Subarus are prone to this sort of problem?
The salesman said if I buy the car they will fix the problem. To which I replied, if they fixed the problem I would take it for another test drive and might consider buying it. A wheel balance is a cheap fix, but four new tyres, or replacing part of the drivetrain doesn't sound cheap at all.

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Reply # 1602417 1-Aug-2016 18:24

"vibration at 75-95kph" It could be anything :(

So it disappears at 110kph?

How many Ks has it done?

Maybe start another thread to get more participation ...

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Reply # 1602518 1-Aug-2016 20:44

Yes. I do apologise for the hijack. Ended up being a lot more long winded than I intended. Just wanted a comment from the obvious Subaru owners here on any common tyre problems. Will consider a new thread.

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