PDA

View Full Version : Speedometer ratios


AllanC
11th February 2012, 21:06
Does anybody know anything about speedo ratios? I'm looking at a new speedo for an 82 CB400N but I can't seem to find what ratio I need. The one I'm looking at has a 2:1 ratio but the only reference I can find is that the CB has a 2240:60 ratio however I also found something that said 19" wheels (which is what the bike has) are always a 2:1. Buggered if I know, anybody got any ideas?
NinjaNanna
13th February 2012, 08:04
hmmm don't know the answer to your question ... but is it feasible to swap the sender on the front wheel at the same time as swapping the speedo?

If it is then you just need to ensure the wheel size is the same and hey presto problem solved.
AllanC
13th February 2012, 11:39
hmmm don't know the answer to your question ... but is it feasible to swap the sender on the front wheel at the same time as swapping the speedo?

If it is then you just need to ensure the wheel size is the same and hey presto problem solved.

Don't know - will have a look on the bike tonight and see if it's feasible to do something with it. Thanks.
AllanC
13th February 2012, 12:46
Found the following on another site, does anybody know if this is correct?
"2240:60 means that the speedometer cable, coming from the front wheel revolves at 2240 RPM at 60MPH.

That's a standard in nearly all Asian bikes. The gears in the front wheel are calibrated for the stock wheel, no matter what size it is. If it's stock, the speedo cable will turn at 2240RPM at 60MPH.

Any generic speedo is made so that it registers for 2240:60. Unless you are using a non-stock wheel, it will read correctly."

Thanks,
NinjaNanna
13th February 2012, 14:33
2240rpm seems bloody fast for something that lasts so long
AllanC
13th February 2012, 14:39
2240rpm seems bloody fast for something that lasts so long

Buggered if I know, seems to be a lot of discussion around this out there but not a lot of definitive answers
NinjaNanna
13th February 2012, 14:42
http://www.dbraun99.com/technical%20index/Calculating%20TPM%20of%20your%20speedometer%20cabl e.pdf

this article seems to indicate the number refers to turns per mile, which would seem more realistic
NinjaNanna
13th February 2012, 14:46
please disregard my last post read the article further and now feel like a twit :doh: