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Tyre Data

by

Mike Meakin

O.E.M on 2CVs were Michelin "X", sizes and tyre diameters in mm (xπ for rolling diameter)

Tyre sizeRolling diameter= Circumference
125x15619 = 1945
135x15631 = 1983
145x15649 = 2039

Toyo/Firestone (radials) fit 2CV rims

Tyre sizeRolling diameter= Circumference
145x15616 (Toyo) = 1936
155x15624 (Firestone) = 1961

Using PMC supplied wire wheels (4") rims on centre-lock adaptors, the largest section possible, without risk of rolling tyres off the rims is 165/70x15 or PMC recommended crossplies 5.60x15

ManufacturerTyre sizeRolling diameter= Circumference
Firestone165x15655 = 2058
Jupiter165x15651 = 2046 (a budget, block tread radial that appears under various brands.)
Camac5.60x15648 = 2036 (crossply tyres)

Using PMC 19" "Skinny Rim" wheels (whether stub-axle mounted or latest "bolt-on"), motorcycle rear or sidecar tyres - block tread rather than the ribbed front - with a fair choice of makes Avon SM & SMII, Longstone, Blockley (the most expensive and Mitas (the "budget tyre) come in the following sizes:

ManufacturerTyre sizeRolling diameter= Circumference
Avon SM & Avon SMII3.50x19682 = 2143
Avon SM sidecar3.50x19675 = 2121
Longstone sidecar3.50x19669 = 2102
Avon SM (sidecar)4.00x19702 = 2206 (probably the widest section possible on the "skinny rims")

The difference between Avon SM and SMII is that SM refers to "Speedmaster" and SMII refers to "Safety Mileage".

Using the formula for calculating relative speeds, the variation of a mm or 2 doesn't make a huge difference to the final 'whole number' answer.

Mike


Go to Gearbox/Tyre/Speed calculator which uses the tyre information above and various gearboxes that can be used on Pembletons.


From Dave Parr

Ref Avon tyres
I have noticed a couple of references to Avon sidecar tyres recently also Avon Speedmaster
Just to be clear these are NOT suitable for Pembleton use.
The triple duty sidecar tyre has a poor load and speed rating ( 75mph max )
The Speedmaster is a motorcycle front tyre not suitable for a driven wheel.
So from this range, the Safety Mileage Mk11 ( 2 ) is the only suitable tyre.
Dave Parr (Silverfish)

I removed these unsuitable tyres from the Gearbox/Tyre/Speed calculator.


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