Smiths Speedo Drive

Previously allan_brooks wrote:

Hello can anyone tell me if 2-1 is the same as 21-10 its for my 1961 es2 and its a 21-10 that come off .If its the wrong one I will have a brand new old stock one to sell

hello well all es2 were fitted with 2-1 speedo drive gearboxes and do the mathes 21-10 is one revolution faster than two to one yours anna j

Following up on Anna's instruction to "to the mathes" 2:1 is the same as 20:10. So if you fit a 21:10 it will expect the drive cable to do 21 revs for every 10 revs of the "works" but it will only be getting 20 revs so it will read 1 rev in every 10, lower. Or putting it another way it will read 10% low - on distance and speed.

Hope his helps.

George

My understanding is like Anna's that ES2s were fitted with 2:1s, so while George is correct that the 21:10 will be 10% out, it depends on what your speedo is expecting. If the speedo is geared for a 2:1 then it will be wrong. If its expecting 21:10 it will be right!

I hope that makes sense!

Dan

Your comment, Dan, reminds me of what my Irish dad used to tell me was written inside his first Highway Code booklet in Ireland: "The rule of the road is a parody quite, whilst riding or driving along. If you keep to the left your sure to go right and if you go right, you go wrong!"

BTW Allan, there should be a set of numbers printed on the face of the speedo - for example 1584. This means the speedo drive cable should rotate at 1580rpm at 60mph. You can calculate the rpm of the rear wheel knowing its outside diameter (inc tyre!). You then multiply this by 2 (for a 2:1 speedo) or 21/10 = 2.05) for a 21:20 speedo to get the expected cable rpm at 60mph and check how close it is. If you have a 3.25" rear tyre I make the answer 1592. Would be interesting to know what the figures are on the face of your speedo?

George

Oops. Apols for typo. The number on the speedo - say 1580 - means the speedo drive rotates at that rate ie 1580 rpm at 60mph.

George

If your speedo is anything like mine (even tho' it's been refurbed) it will show something between 25 and 35 Allan!

It also depends how accurate his one is..........

George

Previously George Phillips wrote:

If your speedo is anything like mine (even tho' it's been refurbed) it will show something between 25 and 35 Allan!

It also depends how accurate his one is..........

George

Those little signs that light-up with your speed as you enter a village can be quite useful.

speed related, just entering into a village i just happened to see a reflective jacket in the distance so i slowed down. as i went past a sign lit up with a smiley face and kids clapping me as i went past. it made me think

Barry