Sprockets

[whitehillbillies]

Good evening.
What is the largest 428 Gearbox Sprocket I can run on a 32a motor.
I am going to put my 24TCS back on the road on Historic Plates.(AUS)
Primary is STD, 60T on the rear. Wondering If I can leave the 60T on and run a larger Gearbox one.
JW has mention suitable road ratio's, but what does this mean with number of sprocket Teeth.
Thanks for the feed back.

whitehillbilly

[John Wakefield]

The primary ratio is fixed 2.15:1 so to achieve around 5.8:1 overall top gear (which would be suitable for road riding) you need 18 on Gearbox and 50 on the back wheel, best to change rear sprocket as that is easiest to change. So if you have a smaller say 17T gear box sprocket you would need to reduce rear sprocket by a couple of teeth. To get the same ratio with 60T rear sprocket you would need a 22 gearbox, but I dont think they are available or would fit. The final drive ratio needs to be in the region of 2.7 : 1

[johnrunnacles]

Largest one for gearbox listed by Villiers Services is 20 teeth.

[John Wakefield]

Largest one for gearbox listed by Villiers Services is 20 teeth.

A 20T to 60T combination would give 6.45 : 1 The 20DC roadster had a top gear ratio of 6.6 : 1 so 6.45 : 1 would be about right for a 250cc

[whitehillbillies]

Thanks for the replies and comments.
I still have a near new 55T 428 rear sprocket. Found it yesterday.
I am running a Wide ratio Trials gearbox.
Guess a 18T would suit. Happy to poke along at 45/50mph.

whitehillbilly