mk1-forum.net

Hi All

Does anyone know where I can find the rolling radius data for dunlop r7 tyres for calculating speedo gears?

The engine is out, so measuring it is a bit tricky as it will be unloaded .....

S

It used to be in the Dunlop catalogue, so try the online racing tyre site. the casing is so stiff, that measuring it with the engine out makes little difference

From Special Tuning 1275GT and Cooper S AKD 5096

Dunlop Tyre and Size R7 500 L10
Wheel revs per mile at 30mph 1053

But that's probably for the old tyres

from Vintage tyres
Type: RADIAL
Diameter: 488 mm
Section Width: 175 mm
Max Speed: 130 mph
Max Load: 355 kg
Weight: 5.5 kg

If the diameter is 488mm then I guess the tread circumference must be 1532mm (approx.) which works out as 1050 revs per mile. This does not allow for any tyre deflection.

Thanks guys. Surfblue is this the modern R7's?
I guess not if it's from the special tuning documentation?

I wonder if they are the same?

Cheers

Simon

Just edited my first post with details of the modern radial type. The ones in the old ST book were cross-plies I think, judging by the tyre sizing.

Thanks surfblue, very much appreciated. I found that info and was looking to work out the revs per mile with deflection.
I'm still digging but haven't found it on the dunlop site yet.

Cheers

Simon

sclemow wrote:I found that info and was looking to work out the revs per mile with deflection.

My copy of the ST manual also shows the 500 L10 R7 at 1053WRPM.

At the top of the column it states that this is "at 30 MPH".
This must therefore be under load or "with deflection", then? Ian

Dunlop, please make me some CR84s please!!!!!!

Vegard wrote:Dunlop, please make me some CR84s please!!!!!!

Why, when CR81s were better and the slick even more so.