Wheel Size Advice

UK forum for general and technical discussion about the Z3 roadster
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waynerp
Joined: Sat 21 Jun, 2014 19:37
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  Z3 roadster 2.8
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Wheel Size Advice

Post by waynerp »

Hi All

OK i have made quite a few school boy errors over the past few days and hope someone can point me in the right direction.
I purchased a set of second hand wheels and only checked the spacing, ie: 5 x 120 and didnt take into consideration the offset, and the new wheels stick out way to far.
I guess the only way i can get these to fit is if i get the backs of the wheels sliced off a few mm. i know this can be done, but dont know how it would affect the safety / strength of the wheel.
Do you know if there is any other way that these would fit on ie: a different wheel hub?
I have had a look on the back of the original Z3 wheels and can not see the ET / offset so does anyone know what dimensions i need to be looking for when looking for new staggered wheels?
any advice much appreciated.

New wheel
Image
Image

standard wheels
Image
waynerp
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
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  Z3 roadster 1.9

Re: Wheel Size Advice

Post by BladeRunner919 »

The specs of all the BMW wheels can be found here:

http://www.bmwstylewheels.com/
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waynerp
Joined: Sat 21 Jun, 2014 19:37
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Re: Wheel Size Advice

Post by waynerp »

excellent thanks.

Wish i'd asked this question before jumping and wasting my money!
waynerp
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c_w
Joined: Thu 19 Aug, 2004 16:50
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  M roadster S50

Re: Wheel Size Advice

Post by c_w »

I wouldn't take any material off the back of the wheel face, it's a set thickness regardless of the offset. The amount they're sticking out I wouldn't bother trying to make them fit, just sell them on. They are likely for a 5-series.

And you standard wheels look better! even better if they were silver :P
Mugs
Joined: Wed 07 Aug, 2013 01:26
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  Z3 roadster 1.9

Re: Wheel Size Advice

Post by Mugs »

any idea what size and offset those wheels are?
do the fronts fit ok or do they stick out too?
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waynerp
Joined: Sat 21 Jun, 2014 19:37
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Re: Wheel Size Advice

Post by waynerp »

Hi
Fronts are 8.5j et15
Rears are 10j et17
I have only put the back on but will put the fronts on at the weekend
waynerp
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beerbelly
Joined: Fri 07 Feb, 2014 20:12
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  blank

Re: Wheel Size Advice

Post by beerbelly »

them offsets are far to low the fronts will stick out too far as well sorry
Jaxx_ZA
Joined: Tue 30 Oct, 2012 18:36
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  Z3 roadster 3.0i

Re: Wheel Size Advice

Post by Jaxx_ZA »

c_w wrote:
And you standard wheels look better! even better if they were silver Image
This. One of my all time favourite 'retro' wheels (after style 42 of course Image). Get them refurbed back to silver, and forget about non-OEM.

Image
Last edited by Jaxx_ZA on Fri 29 May, 2015 19:39, edited 2 times in total.
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Brian4
Joined: Mon 19 Dec, 2011 19:02
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  Z3 roadster 3.0i
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Re: Wheel Size Advice

Post by Brian4 »

Looks as if those wheels were off a 6 or 7 series as they are the oly ones with an offset that low.
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littlefeller
Joined: Sun 28 Apr, 2013 18:06
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  blank

Re: Wheel Size Advice

Post by littlefeller »

just stick em on ebay and get your money back :) you never know you may make a profit. always try breakers yards first there's bargains to be had there :)
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waynerp
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Re: Wheel Size Advice

Post by waynerp »

Thanks for the advice guys.

I have bitten the bullet and chucked them back on feebay.

Will do a bit more research next time!

I do like the standard wheels, but there is something about having a wheel style that shows the deeper wheel on the rear, i think they call it deep dish!
waynerp
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Brian4
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Re: Wheel Size Advice

Post by Brian4 »

Deeper dish means smaller offset. The ///M has it as the rear half shafts and trailing arms are different to the 2.8 and facelift cars. In effect the rear is from the narrow body car but in a wide body shell. if that makes sense.
Brian
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2000 E36/7 Z3 3.0i
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Mugs
Joined: Wed 07 Aug, 2013 01:26
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  Z3 roadster 1.9

Re: Wheel Size Advice

Post by Mugs »

agreed, i have done a wide arch conversion on a 1.9 and i have to use that size and offset on the rears to fill the arches. the trouble is the fronts stick out of the arches too far so i have standard Z3 fronts and matching rears from a 7 series (just having them refurbished before fitting)
all other z3's (apart from M's and coupes) have a wider rear axle so you can't use that low offset on them.
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waynerp
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Re: Wheel Size Advice

Post by waynerp »

Got to be honest it is confusing me a little. So the wheels i have bought have a smaller offset than the originals et 15 front and et17 on the rear, the original bmw wheels are et41.
but the new wheels with the smaller offset stick out to far.
waynerp
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David
Joined: Mon 16 Sep, 2013 18:33
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  Z3 roadster 1.9i

Wheel Size Advice

Post by David »

I've tried to put this in my own words to help you out...

The offset of an alloy wheel is the measurement (in millimetres) of how far from the centre (inside edge to outside edge) of an alloy wheel the back of the bolt holes are.

Therefore a lower offset means the bolt holes are closer to the centre of the alloy compared to a higher ET number. This means that the 'barrel' appears to stick out further.

E.g. ET15 means the back of the bolt holes are 15mm away from the centre of an alloy in the direction of the outer edge of the wheel.

...very complicated to word, but I hope this helps
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Brian H
Joined: Tue 16 Dec, 2008 19:55
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  Z3 roadster 3.0i

Re: Wheel Size Advice

Post by Brian H »

Pictures say a thousand words, have a play around on the website linked below, for simplicity add the following details for your exiting setup and your new setup, then play around with the offset value and it will show you the effects.

Width - 225
Profile - 45
Diameter - 17
Width - 7.5
Offset - keep your existing setup at 41 and then play around with your new setup offset.

The diagram on the right shows the effect of changing the offset value

http://www.willtheyfit.com

Hope the helps :)
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waynerp
Joined: Sat 21 Jun, 2014 19:37
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  Z3 roadster 2.8
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Re: Wheel Size Advice

Post by waynerp »

Excellent website
Many Thanks for the advice
waynerp
Web Design & Optimisation http://www.neden.uk



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