Odometer question

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Sidecar
Posts: 272
Joined: Tue Apr 17, 2007 9:21 pm
Location: Southwestern, Pa.

Odometer question

#1

Post by Sidecar » Sat Jul 14, 2007 9:19 am

My speedo is off 6 mph it's got me wondering if my thoughts are correct on mileage. It's reading 6 mph slow btw. I thought I had the odometer figured out for actual mileage but now I'm starting to wonder. Can someone supply me with an example using the trip odometer reading and the "actual" miles traveled to see if I'm on the correct page?
Example: My trip meter is at 100 miles exactly. What is the "actual" distance that I've covered ??

Thanx
Randy



fourthgear
Posts: 1390
Joined: Mon Apr 11, 2005 1:12 pm
Location: north florida

Re: Odometer question

#2

Post by fourthgear » Sat Jul 14, 2007 5:07 pm

I don't think that it is necessarily true that if your speedo is off that your odometer is off by the same amount.
I could be wrong, but most speedos work off the principle of a spinning magnet and the odometer is direct gear drive. It's possible that there could be a problem with the magnetic drive that is causing it to read wrong but the gear drive could be correct. I would use a hand-held GPS and and compare its reading with the odometer. Most GPS will also tell you your speed so you could check your speedo too.
Just my .03 (inflation).

Sidecar
Posts: 272
Joined: Tue Apr 17, 2007 9:21 pm
Location: Southwestern, Pa.

Re: Odometer question

#3

Post by Sidecar » Sun Jul 15, 2007 12:02 pm

I hadn't thought about this before but I should have included this.
The speedo is a 2 to 1 drive running off the tranny. It read correct until I changed the tranny sprocket. I have clocked it with at least seven other vehicles to verify the speed discrepancy.
My speedometer reads 6 mph lower and the odometer always has less miles than any other vehicle on the same trip.
The more I think about this, the more it makes me wonder ?

kell
Posts: 404
Joined: Sat Jun 19, 2004 2:58 am

Re: Odometer question

#4

Post by kell » Sun Jul 15, 2007 8:33 pm

Charlie Chan say: new tranny sprocket must be bigger than old one if speedometer turn slower now!

Sidecar
Posts: 272
Joined: Tue Apr 17, 2007 9:21 pm
Location: Southwestern, Pa.

Re: Odometer question

#5

Post by Sidecar » Mon Jul 16, 2007 8:21 am

Charlie Chan say: You is correct.
It seems that the odo is 15 miles light (give or take a few) when others read 100 miles.
I was told that I was traveling 58 mph when my speedo is saying 50. (I think I'm 6 mph off though.)
I'm going down to a 24 tooth sprocket so I'll have to start the process over again real soon.
Guess I'll wait til then to figure it out.

BigMike
Posts: 111
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Bikes: 01 FLHPI
64 FLH
Various partials....
Location: SW Florida

Re: Odometer question

#6

Post by BigMike » Mon Jul 16, 2007 4:06 pm

Bottom line...... its a Panhead! if the speedo needle moves, good! if it's kinda accurate, great! if it's exact.... something is wrong and it's gonna break soon! ;D
even new bikes can be inaccurate; +- 5% is normal. If it's consistantly reading slow / short on odometer, you need one or two less teeth on your speedo drive gear, if they are available. Once you are within 5% that's as good as anybody elses. With the Pan, I don't cruise above the speed limit, (70 here interstates, 60-65 state roads) and for tracking fuel consumption, I take a quick peek into the tank once in a while.

kell
Posts: 404
Joined: Sat Jun 19, 2004 2:58 am

Re: Odometer question

#7

Post by kell » Wed Jul 18, 2007 6:08 pm

Sidecar:

For the mileage (or speed) all you gotta do is multiply the reading by the ratio between the new sprocket tooth count and the original sprocket tooth count.
The new sprocket just makes your tranny turn slower with respect to the rear wheel. So the speedo turns slower with respect to the rear wheel also.

Sidecar
Posts: 272
Joined: Tue Apr 17, 2007 9:21 pm
Location: Southwestern, Pa.

Re: Odometer question

#8

Post by Sidecar » Fri Jul 20, 2007 2:41 pm

Sidecar:
For the mileage (or speed) all you gotta do is multiply the reading by the ratio between the new sprocket tooth count and the original sprocket tooth count.


The new sprocket just makes your tranny turn slower with respect to the rear wheel. So the speedo turns slower with respect to the rear wheel also. //
Kell, you wuz right on !!!!!
I was having a rough time using your formula, because it wasn't working out correctly until................................
I had a local shop install a smaller front sprocket. All that time I was running a 26 tooth front sprocket and your formula was dead nuts on. I thought that I was running a 25 tooth sprocket !!!!!!
I ordered a 24 tooth and had that stuck on because I thought I was running a 25 tooth. Guess I have to order another sprocket now and up it to 25 teeth.
Guess I better start paying more attention to details !

kell
Posts: 404
Joined: Sat Jun 19, 2004 2:58 am

Re: Odometer question

#9

Post by kell » Fri Jul 20, 2007 8:41 pm

Good on ya.

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