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Rear Offset


GasMan

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The Caterham Minators 6X13 have a positive offset of 18mm the SLR& R500 6.5X13 and 8.5X13 have a postive 23mm offset. The thing to bear in mind is that once you go above 6X13 ET 18mm on the rear you will be force to locate the rear ARB on the bottom chassis rails or fit the Juno RARB which fits under the fuel tank.
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The Superlite has a min backspace of 94mm (offset neg 3 to 6mm)

 

The R500 rims have a min backspace of around 135mm so the inside edge of the rim sits 41mm closer to the didion tube and rear ARB thus causing the intereference.

 

 

You will be fine with the 7 x 13 and the sidewalls will stay just within the arches.

 

If you use the 8 x13 Superlite, the sidewalls are outside of the arches but the tread is under which might be open to interpretation in road legal terms, although I have run this setup for 5+ years with no issues.

 

Generally the 8" tyre is better suited to the widest ACB10 or CR500.

 

 

 

 

Fat Arn

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Superlite may not make any wheels at all. Their foundry went broke a few months ago and nobody I have spoken with has suggested that they have managed to recover the tooling or find a new foundry to cast the wheels.

 

If they have, the offsets available are listed on their website: www.superlite-wheels.co.uk The range of offsets particularly on the wider wheels is quite limited.

 

The other consideration regarding the caterham offsets is that they have used 18mm as a guide for years for all wheel diameters. Even the HPC wheels which have a rolling radius some 60mm larger than an R500 front uses the same offset.

 

The correct offset only applies to the front, and is related setting up the wheel so the centreline of the contact patch is absolutley in line with the kingpin (or hub pivot)angle. As the wheel diameter changes, so does the offset.

 

 

As I said Matthew, I have run with the ARB above the diff since my car was new, and I have no fouling issues. the inside edges of the tyres, using a 112mm backspace, are around 30mm away from the didion tube and the ARB.

 

Interestingly when I put Counts R500 rear on my car it fouled the didion tube, nnot the ARB!

 

My ARB hangs from below the interia reel boxes. Not sure where yours is if it hangs from the spring damper top mounting.

 

See http://www.the-webbs.com/k2rum/images/Race_rear_brakes_small.jpg for the layout of my rear ARB for comparison.

 

 

 

Fat Arn

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Arnie, I visted Superlite Wheels last week, They did not suggest there was a problem making me some wheels and quoted 14 days. My enquiry was for split rims which can be made with vertually any offset.

 

Arnie, have you mounted the RARB drop links on the inside of the shock absorber bottom mounts and on the inside face of the ARB wings. If so have you had any problems with the links/ball joints catching the ali turreting around the shock? I contemplated mounting them this way to gain extra clearance with wider wheels but thought it looked very close.

 

 

The 6.5" R500/SLR fronts are positive 23mm offset same as the rears.

 

 

Edited by - Rob walker on 20 Mar 2002 12:33:46

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Rob,

 

The foundry with the problem relates to the cast wheels. The spit rims are made elsewhere, but are so expensive the Mike Barnby ones have to be a better alternative. Of course split rims can be made with any offset, but I think Matthew is more likley in the market for normal cast wheels, where the offset ranges are pre defined.

 

I have you mounted the RARB drop links on the outside of the rear top radius arm bush where it bolst to the diddion tube, and the other end on the outside face of the ARB wings.

 

No problems with the links/ball joints catching the ali turreting around the shock, or the damper body itself (I use 2.25" ID springs on the rear). I mounted them this way as I think this is the norm for a '93 car.

 

Clearance is no issue with wider wheels except the SLR and R500 types which as you correctly point out have an uncannyily large +ve offset for a RWD car.

 

 

 

 

 

 

 

Fat Arn

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i was very pissed of with superlight a few weeks ago made an order gave all the correct details deon rear wide track front big brakes ect they still sent wrong ones when i phoned them they said they will fit duu ? i sent them back

 

i then phoned kn got a set from them fitted a dream also £14.00 a set cheaper

ok they are a heavy wheel but looks much nicer than a big silly rim. superlight are also having prob with colours you can only get silver i think. this problem may be to do with what arnie mentioned with the foundry. price from kn £255.00 incl delivery that was for a set of 6 and 7 black center polished rim

 

fredid=blue> smile.gif

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Just spoke to Superlite, the foundry that went bust, hadn't been used by them for quite a while. They now get their wheels cast at the biggest foundry in Wales.

 

So contary to what Arnie has said, all is well at Superlite.

 

 

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Casbar,

 

You are wrong. I have been told by Superlite that the foundary went bust and also that all the tooling for the ML type wheel has been lost as a result.

 

The foundary went bust over Christmas, so I think it rather hasty to suggest they have cleared the backlog already.

 

Fat Arn

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