I know in the past a few buggy people have talked about running a pushbike speedo as a car speedo for their car. At the end of this month I will be doing a touring road event and for the nav sections I need a trip meter accurate to the nearest 100m, as I run smaller front tires and also only have a odometer, I was looking at alternatives. A terra trip would be nice, but time and money….

How do ppl hook up there bike speedo’s do you put the trigger on the wheel and suspension arm? or does this upset balance How accurate are they? Can you just set a specific wheel diameter?

Or is a GPS the go? How well do these work while inside a car and travelling at upt o 120km/hr? are they able to keep up?nn[ Edited on 13-7-2005 byBiX ]

I'm pretty sure this came up a while ago, so may be worth doing a search. Pushbike speedo's can be set for a wide range of diameter wheels, and are quite accurate. Not sure what speed they are good for, but know they are good to atleast 100kph

Mount the magnet to the inner CV (Gearbox end) and mount the sensor (hall effect device) off the gearbox clutch tube bracket bolts.

The trick with those bike speedos is to keep the speed of the magnet slow enough that the sensor has time to see it, so mounting to the CV keeps the speed slow and inbound away from suspension travel etc.

GPSs don't work real well if they can't see the sky. I used a GPS while trouring around tassie. I mounted to the dash at the bottom of the windscreen (with a suction cup) on an late model Falcon. Thanks to the highly sloped windscreen this gave it a good view of the sky. It worked OK most of the time but roads with trees along side or over hanging make the GPS drop out for extended periods.

In a beetle the view of the sky would be somewhat restricted due to the upright nature of the windscreen.

Cool, well i will investigate. how easy is it to extend the cable, as i will need to mount the speedo on the dash of the beetle. but mounting on the CV joint sounds the go. Thanks for that mike.

The cable (or wire) is just 2 core. It can be extended a bit without an issue. Just cut and graft in another bit of 2 core. 2 core speaker wire would be ideal.

make sure when you extend it, that you use a good grade oxygen free copper wire.
these things use a very low voltage, so you can't afford much voltage drop.
the other option is a wireless computer, but you are lomited to around 70-80cm range from the sender to the head unit.
Most computers are good for at least 199kph, some depending on brand will read to 299kph and are accurate to +/- 2m

If you put the pick up on a drive wheel you will not get accurate data due to wheel spin. Try mounting pick up off front caliper mount and magnet inside the back of the rotor.

Most cars run the speedo off the gearbox. So they are all effected by wheel spin. It's not really going to be a problem unless you are driving sideways on dirt allot. And if you are on dirt you will probably be locking the fronts wheels up occasionally on a dive into the corners, so you can't really win.

Well i had a look and i can borrow a terra trip, but need to purchase a new sender for about $100 and the terra trip has no instruction book, and have only 2 weeks to sort it out. I also talked to one of the other rally guys last night, who used to run bike cumputers before he got a terra trip and he said that he found that off the front wheel was good, he araldited (?) a ferroous magnet(stong) to the rim and ran the trigger on the strut. Said it worked pretty well, as he found the driveshaft had a lower speed past the trigger, where as the wheel goes past faster. So i was thinking i might go and get 2 cheaper ones (make sure they read over 100) and then install on one thr front left wheel and one on the drive shaft, so that way it should check itself. I will go and see a mate who is a Microelectric engineer, and make sure i get some good wire. Cheers for your help.

Cool, let us all know how you get on.

A bit late but…

I had a cheap $20 huffy from kmart in/on my buggy for a while. It showed average speed, to speed, odo, speedo, timer but no clock. I have drums all round so I liquid nails-ed the magnet to the rim of the RH front brake drum and 5min epoxied two wire loops onto the top overlap lip of the brake backing plate so I could mini cable tie the pickup to.
Leangthed the signal wire (with left over speaker wire as mentioned above and walla. It worked. Have since taken it off and fitted it to the MC, could have bought another I spose.

A trick is while you have the wire cut, run it inside some thin, flexy but strong hose or sheath for protection. And of course cable tie everything up out of the way.

A friend has a trek cycle computer with all the functions in his baja. He found a little nook for the magnet on his disk front end and 5 min epoxied it in and also somewhere to cable tie his pickup too. It works fine and has done so for 1000s of Ks.

cool, i will have a play on sunday, as i will be putting new cobra seat and harness in on sat. I talked to my micro elec engineer mate, and he said if i told him earlier he could have done a custom one for me... with any features i wanted

mabye i should get the wire replaced with a bluetooth system.....

Ok well the verdict is in.

For speed readings its fine,

for a trip meter its a piece of S&^t!!!!

we found on the runs that at slower speeds of up to 70km/h it would be accurate up to 15km travelled but once wetravelled more than 15km or went above 70km/hr the trip would be highly in accurate. This was not good when you are trying to nav and want it to be accurate to the nearest 100m or even 500m, but on the final 80km leg, was out by 25%.

So

good for getting an averaged speed, bad for getting a accurate trip reading.

Terra trip here i come.

Maybe it is the quality of the bike speedo you're using. A lot of the motorcycle racers use the BC800, which is supposedly good for 200km/hr

it was a good brand with a rated top speed of 299km/hr

the speed wasn't the problem but the trip meter. i think it trys tio average out speeds and stuff like that to work out the trip meter therefore in-accuracy.