I read about the possiblity of using bicycle computers in place of rally computers and I thought I'd ask who has had experience with them and what came of it.

There is no room in my car for a full fledged rally computer and the speedoneedle covers an entire digit of the tripmeter 80% of the time.

(I did hear about using a Topeaks Panorama once apon a time for a rally computer but I'd sooner experiment with a cheaper model if it's worth trying at all)

Suggestions??
Thanks, Anthony

We used three bike computers all wired up to the same sensor for a couple of events in our car.  Two in front of the driver (average speed and distance displayed) and one in front of the navigator for distance).  

You can run as many computers as you want off of one sensor.  I ran my sensor off the rear diff, using silicone to attach a rare earth magnet to the driveshaft.  The next sensor I mount will be to the front diff, as I tend to spin those tires less.

I used a Trek computer, as it had the biggest display numbers I could find. The speed values went up by 1km per hour up to 100km/h.  Then the speed values went up by 5km/h.  If you can find some way old (6yrs) Vetta C10 or C15 computers, they'd be the best.

Advantages: Cheap. Reliable. (if you set it up right).

Disadvantages:
- Hard to read, you may think the numbers are big...but they aren't.  
- No backlight. I didn't think it would be a big deal, but they are tough to read. Annoyed the heck out of me. #1 reason why I wouldn't use them again.
- Difficult to re-set.  It's not impossible, but it ain't easy!  If I was going to use them for more then one event, I would've pulled them apart and wired in a larger reset switch (mounted elsewhere in the car).


HTH,
-Dave

I thank you for the input.  based on this and other info I took the experimental plunge and ordered the Topeak Panoram Bicycle computer to mount on the Miata.  
($66.99 from www.bikecanada.com)

It is a wide format computer (if you can use that teminology) which displays all of time, Speed and Distance at once (or Average speed, distance and time.. depending what you choose) up to 200KPH
AND
It has an Indiglo style backlit display.

I plan on making a permenant mount for the sensor around or on the caliper but leave the sensor itself easily removable + unplugable so as to not subject it to unnessary wear between events (which living in North Bay it can be a while between such happenings)

I'll let you know how it all works out.
If I'am lucky It will be done for the Discover Ontario!

Thanks, Anthony