Electronic speedo for multiple tyre sizes

[Tommo]

Not sure this should go in the Fab section... but it involves glue so I spose that counts...

Got 31s, 33s and 35s? Need a speedo which will do ALL at once?

I have 31s right now, but when they wear out a bit more I'll go 33s or maybe bigger. I never had the speedo calibrated for the 31s to start with, and there's no point if I'm going to go bigger soonish. And even when I go 33, I might get a nice aggressive tread pattern which I swap OFF again for road use - with a change in size at the same time. I use my GPS at the moment, but I don't always like leaving it on the dash, depending on where I'm parked, and it's a pain to keep disconnecting it and locking it away all the time.

I don't know much about speedo gears, but they cost $x and for me would then cost another $y to get them installed. How long does it take to change them? Is it easy to do? Maybe I'll get it done with the next set of tyres.

So I needed a speedo that would change with my tyre size, and would be cheap and unobtrusive.

So I got myself a wireless bicycle speedo cheap off the net.
A bit of liquid nails.
I put the sensor on the flywheel thing at the back of the transfer case, where the tailshaft comes out, cos it's raised up a bit and a bit protected compared with putting it on a wheel rim. It's also closer to where the receiver bit is in the cab, with a straight line distance of less than a metre.
A little bit of calibration using the GPS to tell the real speed and altering the 'rim size' entry in the bike computer, and it works like a charm!
HEY PRESTO!
Quickly and easily changable electronic speedo, spit timer/odometer and speed alarm!

And as ugly as it may be, you can't see it anyway unless you're looking at my transfer case.

You could probably use a wired bike speedo too, and take the wire up through the gear lever rubber, if the wire was long enough. You can get one from d$ckless smith for under $10 if you wanted to give it a go.

[Steve F]

I bought a kit from Jaycar, I've put it together but haven't wired it in to the sender yet. It lets you adjust your stock speedo in 1% increments. Mine is currently out by 8% but I may also go up a size in tyres next time.

Cheers
Steve

[wizbang]

Nice work Tommo, one of the little things stopping me from going to larger tyres.
Thanks.

[Fat Chili]

Just for info - a speedo correction gear costs around $80 (sometimes less) and takes about 5 - 10 minutes to install. The hardest thing to do is getting under the Jeep, really simple (getting under the Jeep is taken into account in the time frame).

[Tommo]

$80? Wow. My cheapo solution was based on it costing $50 installed, which I thought was too much.

Here's the jaycar speedo corrector:
http://www.jaycar.com.au/productView.asp?ID=KC5380


These cost $45, then you solder it together, then install it. It would be tidier than my option, a bit more $$, and a bit more technical. But you don't have to pay another $80 for another gear when you change sizes again! Good idea Steve.

[Gildo]

Nice one dood, thinking outside the box has solved an out of the gearbox problem!
I guess once you have established the settings for different size tyres, it will be a couple of button pushes to swap it to the correct speed.
The Jaycar one sounds cool too, any more info?

[Steve F]

The good thing about the Jaycar kit is it adjusts the output from the sender at the gearbox. So like the gear replacement it means the computer is also geting the modified signal which in turn means the transmission on the XJ will shift at the correct speeds etc etc. Not so critical in the TJ where the auto is not electronically controlled.

Cheers
Steve