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 Post subject: Wheels & Offsets
PostPosted: Sun Oct 17, 2010 10:52 am 
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1275cc
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Location: Vegus, Brisvegus
To help people considering different wheels and wondering about flares let's put together some size & offset info. I'll start with three wheels:

Stock 10x3.5" Steel wheels have an offset of 28mm. These will fit with no spacer drums and not need flares.

Rover 12x4.5" Steel wheels have an offset of 30mm The outside edge of these wheels sticks out 12mm more if mounted on the same face BUT the inside edge sticks in 16mm more. This means that these wheels cannot be mounted on non-spacer drums as the tyres rub the training arms. Therefore, when mounted on 1" spacer drums or disc drive flanges the outside edge sticks out 37.4 mm more than stock 10s. Narrow flares are required.

'std offset' Contessa 10x5" alloys have an offset of EDIT: typo earlier, should read 18mm other numbers below correct. The outside edge sticks out 29mm more than a 10" steelie if mounted on the same face. The inside edge sticks in 9mm more. These are JUST ok on non-spacer drums (about 2-3mm clearance between a Falken 165-70-10 tyre and the trailing arm). So: if mounted on non-spacer drums narrow flares are required. If mounted on 1" spacer drums or disc drive flanges they stick out 54.4 mm more than stock steelies on non-spacer drums and hence need medium width flares.

I have not discussed 1/2" spacer drums as I have hardly ever come across these but the calcs are similar. Also similar are vented disc drive flanges which add another 1/2 inch to the stick-out.

Anyone else got measurements of wheel widths and offsets? We need Cooper S and 'LS offset' Contessas as a minimum.

EDIT: Clarification found.

M


Last edited by Mokesta on Thu Jun 02, 2011 9:02 pm, edited 4 times in total.

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PostPosted: Sun Oct 17, 2010 11:29 am 
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848cc
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Location: Mapleton
Sticky?

Would be a great idea to add these to the existing wheels database.

I'll measure the LS contessas when I get back to the car again.

Cheers.


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PostPosted: Sun Oct 17, 2010 11:39 am 
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1275cc
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If anyone is wondering why the dimensions seem a bit strange, it is because I am measuring to the outside edge of the wheel. The distance between the inner rim face where the beed sits (and the "width" is measured) and this outer edge is different for each of teh three wheel types I have to measure.

More info:

Stock 10s = 112mm wide total
Rover 12s = 140mm wide total
'std offset' Contessa = 150mm wide total

I measured total width (W) and the distance between the inside edge and mounting face (M).
Offset = W/2-M
Stick-out = W-M
Stick-in = M

M


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PostPosted: Sun Oct 17, 2010 8:46 pm 
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998cc
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Ok so if i'm looking at 2 sets of wheels from the uk with tyres for a good price but the only difference is the offset...

one is 0

the other is -7et

these are on 12x6 rims....

i already have 12x6 rims, is there a way i can measure my current wheels to figure out what my current ones are and figure out if i need the 0 ones or the -7 ones..?


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PostPosted: Sun Oct 17, 2010 10:23 pm 
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Offset refers to the distance between the middle of the wheel and the plane of the hub mounting surface of the wheel.

I.E. 0 offset means the plane of the hub mounting surface is exactly in the middle of the wheel.

-7 means it's further to the centre of the car - the wheel will stick out 7mm more.

So if your existing rim is exactly in the middle it's zero offset. Find the middle of the wheel and measure how far the bit that mounts to the hub is away from it.

Damn, that's hard to explain easily.

Diagram? ET = offset.

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 Post subject:
PostPosted: Mon Oct 18, 2010 3:40 am 
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848cc
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Location: Perth, WA
Here are some I measured a while ago.
All measurements are by hand with a tape measure and straight edge, so there could easily be a couple of mm error anywhere.

Standard 3.5" steel 30mm
Firsat 4.5" steel 34mm
Contesta SS 5" 18mm
Contesta LS 5" 37mm
Superlight 5" 23mm

The graph of rim profiles is relative to the mounting face (0 on the scale of mm) with outboard to the left, inboard to the right.

Whether they'll rub the trailing arm or body or protrude from the guards also depends on which tyre you choose.

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PostPosted: Mon Oct 18, 2010 8:12 am 
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998cc
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This is great. I was just thinking of this a couple of days ago & when i was restoring mine. Will measure them up tonight :)

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PostPosted: Mon Oct 18, 2010 2:27 pm 
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well done, best thread in recent memory, sticky please


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 Post subject:
PostPosted: Mon Oct 18, 2010 6:46 pm 
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998cc
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That's an awesome guide guys, i'll have to get the straight edge and tape out next time in shed,

for now i've just returned with pics of all the markings on the wheels.

bear with me

Image

they're 12x6 Watanabe's

Image

i'm assuming they were cast in april of 1997 \/ \/ \/ \/

Image

their maximum load rating is 310kg \/ \/ \/

Image

and i reckon their offset may be 5mm \/ \/ \/
but i'll have to measure to figure out if positive or negative

Image


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 Post subject:
PostPosted: Mon Oct 18, 2010 7:21 pm 
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woodwormm wrote:
and i reckon their offset may be 5mm \/ \/ \/
but i'll have to measure to figure out if positive or negative

Image


Maybe it's the spare.

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 Post subject:
PostPosted: Mon Oct 18, 2010 7:35 pm 
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Location: northern new england tablelands
10 x 4.5 jelly bean alloy: offset= -11.5mm, max width= 137mm
10 x 5.0 Mk2 Tasman alloy: offset= -22mm, max width= 154mm

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 Post subject:
PostPosted: Mon Oct 18, 2010 8:27 pm 
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to measure the offset:
step 1: Measure across the rim from outside lip to outside lip. if the measurement seems odd that because the the width is usually calculated by measuring from the inside of each of the lips(called the bead).

step2: Lay the rim face down. Lay a straight edge across the the rear of the rim & use the ruler/tape measure to measure the distance from the underside of the straight edge to the mating surface of the rim (the face that sits against the brakes).

step 3: Divide your first measurement by two. Using this number subtract the measurement found in step 2 & you have your offset.

If the offset is positive the wheel will sit more towards the body. If the offset is negative the wheel will sit further out from the body (more dish).


Here's a tool to calculate the difference between your current rims & your possible future rim, allowing you to know if you need bigger flares & the clearance to the inside:http://www.1010tires.com/WheelOffsetCalculator.asp

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 Post subject: Wheels
PostPosted: Fri Oct 29, 2010 11:09 am 
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I am fitting Cooper S flares to my MK1 deluxe
With the preference of 12" wheels what would be the Max width of the tyre allowed so it sits nicely under the flare?

We can take into consideration using Standard Drums or spaced Drums... Basically I want a reasonably FAT tyre

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 Post subject:
PostPosted: Thu Jun 02, 2011 3:46 pm 
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Old thread revival...

My first post gave a stock Contessa wheel an offset of 30mm but that conflicted with Greame H's measurement. I sold the set I measured first but now have another set. With these I measure 17mm offset which agrees with Greame's 18mm.

EDIT: Turns out I just put a typo in the original post. 18 is the number and all other numbers are right.

Now it's back to the Midland Wheels site for me :lol:

M


Last edited by Mokesta on Thu Jun 02, 2011 9:11 pm, edited 1 time in total.

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 Post subject: Re: Wheels & Offsets
PostPosted: Thu Jun 02, 2011 6:26 pm 
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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.


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