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 Post subject: Re: Wheels & Offsets
PostPosted: Thu Jun 02, 2011 8:09 pm 
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WiLo wrote:
Mokesta wrote:
These are JUST ok on non-spacer drums (about 2-3mm clearance between a Falken 165-70-10 tyre and the trailing arm).


i have std offset contessas, and when i had non spacered drums the tyres(165 falkens) rubbed on the rear trailing arm, i have heard of a few people having this problem so whilst they might not rub when stationery there must be slight contact whilst driving.


We had the same problem on our Mini K with the Contessas, a well known Mini shop supplied us with 2 thin spacers made by machining the centres out of a couple of old brake drums and used them as a spacer very thin but enough to solve the rubbing and thin enough that the nut still had plenty of thread to bite onto.


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PostPosted: Thu Feb 23, 2012 8:41 pm 
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Non-spacered drums are 4mm thick in the centre so they can be cut to make 4mm spacers. Spacers drums are 27mm thick, pushing a wheel out 23mm further than ordinary drums. Contrary to my earlier understanding, they aren't an inch wider.

From another thread. I copied it to here so this stuff appears in one place:



I have done some measurements. For the rears these number definately work. For the fronts, not confirmed yet.

If you want 10x5 wheels to fit without flares on stepped drums then they should have an offset (ET) of 37mm like the LS Contessas. These give just enough clearance to the trailing arm when using A032R 165/70/10 tyres. I measured Falken FK07E 165/70/10 tyres as being 6mm wider over the sidewalls so they would tighten the gap to the trailing arms. Even this small amount may mean they rub. Any larger offset than 37mm will lead to rubbing on the trailing arms. You could probably go a few mm less offset, say to 34mm.

If you want to run Mk2 S flares (or innocenti/rover plastic ones), which on the rear give 21mm more width at the top than the standard wheel arch trim, and you want the 10x5 wheels to fill the arches then you need an offset of 16mm. Coincidently, the 'SS' or 'standard' Contessas have an ET of 17mm.

If you want to run Mk2 S flares and the widest rims possible with the tyres not sticking out more than those above, while using stepped drums, then the size should be 5.5x10 with an ET of between 23mm to 31mm.

If you want to run Mk2 S flares and the widest rims possible with the tyres sticking out just 5.5mm more than those above, while using stepped drums, then the size should be 6x10 with an ET of 24mm.

I suggest asking a seller to give you the ET/offset for any wheel you are considering and check against the above.


Ok, so you have found a wheel and want to see whether it fits according to the rules above. Here's how you measure it.


You really need a ruler and a straight edge as a minimum. A vernier calliper makes part 2 easier. The straight edge needs to be about 280mm maximum overall to measure wheels that have tyres on them. any longer and it rides on the tyre and you can't press it agains the rim. The ruler needs to have readings starting at the end, not a few mm in from the end like old wooden school rulers.

1/ Inside the wheel. Lay the straight edge across the edge of the rim. Use the ruler to measure the distance from the mounting surface to the straight edge. In the case of an LS Contessa this reads 112mm

2/ Outside the wheel. Lay the straight edge across the edge of the rim and use the ruler through the centre hole to measure the distance out to the straight edge from the mounting surface. This can be tricky due to the chamfer on the centre hole so another short straight edge can be used (like a pencil). In the case of LS offset contessas this dimension reads 37mm

3/ Do this calculation:

Inside measurement - (inside measurement + outside measurement)/2 = Offset

eg: 112-(112+37)/2=offset
112-(149)/2=offset
112-74.5=offset
37.5=offset

Other factoids:
The rim may not say its size (width in inches). If it has a tyre fitted it is hard to measure the inside of the bead surfaces that set the width. Typical alloys are about 11mm wider per side (22mm overall) than their tyre mounting size.

So add Inside Measurement to Outside Measurement, subtract 22mm and convert to Inches.

eg: (inside measurement + outside measurement - 22)/25.4=size
(112 + 37 - 22)/25.4 = size
127/25.4=size
5=size

Happy shopping!


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