offset

[catastrada]

I need to buy a new set of wheels for my Duratec R (narrow chassis) for slick tyres.

For several reasons the tyres are Michelin (Radial) 16/53/13 front and 23/57/13 rear (Formula Renault tyres).

 

I should go for a set of compomotive CXR, 7'' front and 8,5'' rear (ongoing bulk buy).

 

Could those who have fitted CXR 7' and 8,5'' tell me the offset of their wheels please?

 

[Rob Walker]

The Mich 23/57/13 rears are too wide for the S3 caterham they rub both the wings and the radius arms/watts linkage arms under hard cornering no matter what offset you order or how stiff you set up the car.. The 16/53/13 are ok and will fit nicely on a 6.5" rim with offset ET-19.

 

Rob

[elie boone]

I don(t have experience nor with those tyres and wheels but if they rub everywhere you need longer studs a spacer for the wheel and wider rear wings. job done

 

[Rob Walker]

If you run without rear wings this can also help or you could inflate the tyres to 100 psi stop them distorting or drive slowly through the corners.

[catastrada]

If we exclude the mentioned tyre sizes, what should be the offset of 8,5'' rear wheels please?

 

Edited by - Catastrada on 17 Nov 2009 14:16:12

[Rob Walker]

ET 24 for the 8.5" rims and I would recomend ET19 for the 6.5" I have tried the standard Caterham ET24 on the fronts and 185 tyres rub the wingstays ET 19 are perfect. Deal direct with compomotive you should be able to haggle some discount, good quality wheels that are both round and run true unlike others I am not allowed to mention.

 

Rob

[catastrada]

Thank you Rob

 

Today we will try to fit the Mich slicks on CC wheels (6 ET24 / 8 ET24) to check if the tyres are rubbing, and if not to estimate the right offset for the rears.

 

0,5''= 12.7mm => 6.35mm each side => offset to avoid inside rubbing could be 24-6=18.

 

Edited by - Catastrada on 18 Nov 2009 07:24:09

[catastrada]

We fitted the Mich slicks tyres on CC 8 spokes wheels (6 front and 8 rear).

There is no trouble at all.

To be sure I did 15 laps yesterday with those wheels fitted on my Duratec R and no rubbing problem.

 

(Set up need to be adjusted: camber front from 0 to max, rear Dedion ears from 0,25 to 2°. Michelin is suggesting 4.5 to 5° camber).

 

The tech spec from those slicks mention 5.5'' to 8'' for the front wheels and 8.5'' to 11'' for the rear wheels.

I'm still wondering if I go for 6.5'' / 8.5'' or 7'' / 9''...

[catastrada]

For record purpose I add the weight of the CC 8 spokes wheel (without tyres).

6x13 => 5.2 kg

8x13 => 5.4 kg

 

here a pic of my Duratec R with the "big" MIchelin slicks fitted

 

 

Edited by - Catastrada on 23 Nov 2009 13:24:01