Speedo question

[Whitewill1412]

I have a new old stock speedometer for a 20 inch bike. Is there any way I can make it work on a 26 inch bike?

 

[Sidewinder Jerry]

I have a new old stock speedometer for a 20 inch bike. Is there any way I can make it work on a 26 inch bike?

You need to post pictures of it

 

[Chainlube]

I have a new old stock speedometer for a 20 inch bike. Is there any way I can make it work on a 26 inch bike?

Does the cable reach the drop outs on the front wheel?

 

[Whitewill1412]

Does the cable reach the drop outs on the front wheel?

I don't know. I'll have to check that later. I'm about to go to work. Why do you ask?

 

[Chainlube]

I don't know. I'll have to check that later. I'm about to go to work. Why do you ask?

If it can reach the wheel, then it would probably work. It might be off a bit, but still give you some indication on your speed.

 

[DieselTech]

You Should be able to just change the speedo drive mechanism with a 26" wheel model.

 

[Whitewill1412]

You Should be able to just change the speedo drive mechanism with a 26" wheel model.

Yeah but where would I get just the drive mechanism? I tried search on Amazon and a lot of bike stuff came up, but not just a drive mechanism.

 

[Whitewill1412]

You Should be able to just change the speedo drive mechanism with a 26" wheel model.

I wonder if anyone here would know how to do the math to figure the difference. Like maybe it would just be like you add 5 mph or something like that. That would be something like algebra. I was never good at that.

 

[Sidewinder Jerry]

I wonder if anyone here would know how to do the math to figure the difference. Like maybe it would just be like you add 5 mph or something like that. That would be something like algebra. I was never good at that.

Sidewinder speed formula:

(Engine RPM × Wheel Diameter × π)÷(Total Reduction × 1056)=MPH

 

[Sidewinder Jerry]

If you can't calibrate the speedometer then you need a tachometer. These are very affordable on eBay. First you'd have to connect the speedometer with the cover glass removed to the back wheel and have the wheel off the ground. Paint over the old markings. Next, you'd have to figure out the minimum rpm measurements for at least every 5 mph using 26" wheels. When you hit These rpm measurements transfer marks to the painted-over speedometer display.

I could do the calculations for you if I knew what engine you plan to use and what rear sprocket you plan to use.