speedometer on doodlebug?

I went on Ebay to look for one....................

I found some for under $10 !!!!!! But they only work with tires that are 26" or larger.

I did some math and found that I could use one and trick the computer into thinking my tire was twice as big.

That means that what ever speed the Speedo was reading would need to be divided in half....
If your db is stock, I wouldnt put a speedo on it. :thumbsup:
Exactly... A Wind Sock may be more accurate. :lol:

The bicycle computer would be your best bet. I do not know what brand you need to look for, but there are some models that will adjust down to a tire on a 4" rim. Nice thing about the bike computers is some of the other features. Like keeping track of your overall miles or hours of operation for maintenance reasons.

You may also be able to adapt something from a pocket-bike.


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We used the Schwinn speedo from Walmart. I think it was just under 20 dollars. In the instructions there is a formula for wheel sizes. I will go down really small. Its not 100%. We used a GPS after to further calibrate. You can change the number that you input by going up or down one number. The Speedo is better now only off when you go above 50mph. But only 1mph according to my TomTom.
I also has a magnet for the wheel sensor so we used double sided sticky tape to but it on the inside of the rim. We may later drill a small hole thought he rim to attach it better for wet conditions.
The cheap Bell bike computer works great on my mini. You program the computer at setup for the circumference of your tire in milimeters. It comes with a chart for standard bicycle sizes, but if you can measure your tire, and convert to mm's, then you are set.

The only question is whether the sensor and magnet setup on the DB will work...
So can I use it as a tach on the crank too?
I am glad you guys have done this I thought about doing the same thing a long time ago but was too lazy and cheap to buy the thing.
No you cant use it as a tach. I had one that has the 2 sensors I thought about it also. Tried it and no go. Anything more than idle it would stop reading. I believe its a POS hall effect sensor. If you want a tach you should just buy the gokart speedo/tach setup
Hell I never thought about doing that. I tried using one computer to do both. It failed. That's a great Idea. Thinking I'm going to get another one for a tach now.

Thanks for images. They sell these Schwinn 12 Function Computer @ local WAL*MART for $9.96. Did not know if they would work for a mini bike. I am going to get one of these for a speedometer. Thanks.

Anytime,when you get it,just make sure the sensor is close enough.Its hard to see in the photo but I put a piece of chrome molding that I had laying around and stuck it to the fork and then put the sensor on that with zip ties,works great!