speedo drive and wheel size By skikman (Read 916 times)

[skikman]

hi.i need a speedo drive for my chinese 50cc scooter with a size 13 wheel on the front.i can get a speedo drive that looks the same off another scooter but with a size 12 wheel.will it read right on the clock?

[Bashan]

Well, they don't read right anyway but that's not your point. The radius from the axle to the outside of the tire will determine how many turns of the wheel occur per unit of distance. A bigger wheel will turn fewer times per mile than a smaller wheel. So yes, size matters once again! There's different gear sets for different applications. Rich

[gatekeeper]

From what I've seen, the gearing on these speedo drive units of a certain type are all geared the same whether they are mounted on 10 inch, 12 inch, 13 inch or 16 inch wheel. As long they all fit the same size axle shaft it should make no difference on your speedometer readings. Wheel and tire size are usually the determining variable in speedo gear ratios.

[Bashan]

So if the gears are the same for a 16" wheel and a 10" wheel, where do the different speedo systems adapt for the difference in the rotation speed? Is the speedo head specific for a certain size wheel so it reads correctly? A 10" wheel is going to turn a helluva lot more times in one mile than a 16" wheel. Rich

[gatekeeper]

Aug 10, 2011 14:17:44 GMT -6 Bashan said:

So if the gears are the same for a 16" wheel and a 10" wheel, where do the different speedo systems adapt for the difference in the rotation speed? Is the speedo head specific for a certain size wheel so it reads correctly? A 10" wheel is going to turn a helluva lot more times in one mile than a 16" wheel. Rich

If a 10 inch wheeled scooter and a 16 inch wheeled scooter use the exact same speedo drive hub, then the compensation would have to be in the speedometer head.

What I was trying to tell Skikman was that if the drive unit he was looking at was the exact same as his old one it wouldn't change the reading on his speedometer regardless of the one inch difference in wheel size.

Sometimes I see what I want to say in my head but it doesn't come out clearly.

[skikman]

Aug 10, 2011 15:49:48 GMT -6 gatekeeper said:

Aug 10, 2011 14:17:44 GMT -6 Bashan said:

So if the gears are the same for a 16" wheel and a 10" wheel, where do the different speedo systems adapt for the difference in the rotation speed? Is the speedo head specific for a certain size wheel so it reads correctly? A 10" wheel is going to turn a helluva lot more times in one mile than a 16" wheel. Rich

If a 10 inch wheeled scooter and a 16 inch wheeled scooter use the exact same speedo drive hub, then the compensation would have to be in the speedometer head.

What I was trying to tell Skikman was that if the drive unit he was looking at was the exact same as his old one it wouldn't change the reading on his speedometer regardless of the one inch difference in wheel size.

Sometimes I see what I want to say in my head but it doesn't come out clearly.

well i did put one on of a honda cm125 and it was reading way to fast 70mph +.i was just wondering about the 1" difference

[gatekeeper]

I would imagine that something designed for a Japanese motorcycle would have different gearing than something designed for a Chinese scooter. It could fit but throw your readings off. What I said above was directed at Chinese scooters.

[Bashan]

Sometimes I see what I want to say in my head but it doesn't come out clearly.

The voices in my head tell me what to say........redrum Rich