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Discussion Starter · #1 · (Edited)
I have just purchased some wheels from a seven and trying to fit to an 8-series. They are offset and the backs fit fine. However the fronts do not fit and hit the strut while fitting; I'm going from 17 " 235/45 IS10 to some 18" 235/50 IS20. The new wheel fouls on the strut and the base of the spring. Will a 10mm offset sort my problem or is the 18" plus 50mm tyre to tall for the suspension?

I thought that 20" were fine on an 8 so didn't think the problem would come into play. Will a spacer sort the problem?
 

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I've moved this thread into the alloy wheel section:thumbsup

In the back of the wheel you are trying to fit there should be an ET or IS numbet and two digits after it. What is this number please as it informs us of the wheel offset:thumbsup
 

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Discussion Starter · #3 ·
The wheel sizes and IS values are 17" 235/45 IS10 BBS alloys IS10 (8J17H2 on rims) which I was hoping to replace with 18" 235/50 IS20 (8Jx18 BMW 1091990).

I have also created two threads that I'm not sure how to merge, sorry.
 

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Okay first things first. The tyre size is completely wrong for your 8 series

Tyre Size..............................Diameter.............................Circumference

235/45 17.............................643.30mm............................2020.98mm

235/50 18.............................692.20mm............................2174.61mm

Difference.............................48.9mm...............................153.32mm

The tolerance allowed when changing wheel and tyre sizes must stay within +/- 2.5%

The difference between the sizes above is + 7.6%

This means that when your speedo is reading 70MPH your actual speed will be 75.32MPH:yikes








I would replace the tyres and try the wheels again as the offset range on an 8 series on an 18" wheel is ET10 - ET20 (8jx18)

You may not need spacers at all and if you do you may get away with a 3mm or 5mm spacer:thumbsup
 

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Is it the tyre or the wheel that is catching the shock???

Is it the top of the tread catching the bottom of the spring cup or is it fouling the part where the piston operates?

If it's fouling on the cup then changing to a 235/40 18 will reduce the diameter size and clear the cup.

If it's fouling the strut itself then you will need a spacer to move it away even with the change in tyre size:frown


Also, just a word of warning... The 8 series is EXTREMELY sensitive to wheel upgrades and you may suffer with balancing issues (vibration felt through the vehicle)
 

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Discussion Starter · #7 ·
Only the Tyre that's catching but the piston and spring cup

The tyre is catching both the piston and the cup to the extent that it prevents the wheel actually going on, so not sure whether the wheel would rub on its own or not.

Sounds like a new set of tyres and spacers:jaw-dropping. Do you think it worth a go (200+ I guess) or better to cut losses and sell the wheels again?
 

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The spacers alone can be dear if it turns out you need a bolt on kit.

Get into your local specialist and get them to work out what is required. If you have no joy then let me know and I will pass you on to an excellent contact that I have but is located in the South West (they do mail order):thumbsup
 

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Just to let you Know I have 8 series BBS on my e34..the et is 19 at rear with 9J..and 10 et 8J front I'm having trouble with the Small offset at the front so I asume your extra 10 is causing trouble
 

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Discussion Starter · #10 ·
Indeed the tyres sorted it so thanks A20 RYM.

Height was an issue, didn't fit at all. But also the additional bulge in the wall due to the additional height caused the problem. fitted the 235/40s and all is well. I have two nearly new 235/50s about to go to eBay unless anyone would like them.

Thanks again,
Graeme
 
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