I've just joined the club :)

[StoatWithToast]

I thought the frequency of the rebuilds was rather a lot too; I've not heard of it on any other car, and having another owner say the same reaffirms that. Hopefully this will be the last, if not I'll have to source a new one to see if we have any more luck with that.

I think the diff is fine - looking at the RPM to MPH ratio in 4th and the top speed, they matches quite well, so I think it is just a speedo fault. I'm starting to think each rebuild has slightly pushed the calibration out to the point it is at now, or somebody recalibrated it badly during one of the rebuilds.

We've just used a man (JDO) to calibrate the speedo on the XI, if now works as as good as his service then he'll be getting the speedo from the Elan soon enough. He turned the speedo for the XI around in less than 48 hours, including postage both ways! Speedy Cables said it'd take 3 weeks AND the dealer let them have a go at the Elan speedo before we took ownership; they didn't fix it and actually made it worse so they'll not be getting any of our money.

[curly type 26]

Welcome stoat, the x1 is great car we built the very ist one using a L2d dry sumped big valve twink, did it go you could take your hands off the wheel at 130 plus & still went arrow straight, enjoy Curly ( still got pair of unused front shocks if required)

[msd1107]

There is a down loadable spreadsheet at elan-f15/updated-spreadsheets-t18445.html that lets you determine the proper speedometer drive gear for the transmission given the tire size, differential ratio and speedometer turns/mile figure. This sets the odometer calibration properly. From there they can calibrate the speedometer properly.

Keep in mind that during the years, the Elan and +2 had 5 tire sizes, 4 common differential ratios, 3 transmission speedometer drive gears, and three speedometer turns/mile figures. The 3 transmission speedometer drive gears did not accommodate all the variations. If your car is one of those, the spreadsheet allows you to determine the pair of gears in the speedometer for optimum calibration. Most places that rebuild Smiths speedometers can give you an odometer with the correct pair of gears for the nearest turns/mile figure and then calibrate the speedometer around that.

If your speedometer keeps losing calibration with no changes otherwise, then there is something wrong with the coiled spring that establishes the speedometer reading. Pretty soon, the maintenance charges to recalibrate the speedometer exceed the cost of a NOS unit.

David
1968 36/7988

[Heuer]

You can use this calculator to check gearing and rpm: http://wahiduddin.net/calc/calc_speed_rpm.htm

Great little tool!

[msd1107]

Heuer,

Interesting little calculator.

There are many like it on the web. However, they suffer from a significant inaccuracy. I used to email these people pointing out the problem, and some possible enhancements. 45 years ago, I made the same mistake. I was using a slide rule to calculate and didn't know any better.

The previously referenced spreadsheet has an internal database that returns the manufacturer specified rev/mile figure for their tires. The user can inspect the data to see if it appropriate for their particular tire (especially if they have the manufacturer data for that specific tire).

All default or calculated figures can be over ridden if the user has the need to do so. It may take awhile to read the help text, but the results are well worth it. With 35 years of usage, probably you can feel confident in its results (This is a decendant of the original program written in Fortran and running on main frame). The first version was briefly used by a F1 team (they didn't have a computer on which to run the program).

So pick and choose as you wish. The worksheet RPMGear gives you a two dimensional display and printout of speed for up to 15 gearbox ratios and 75+ rpm figures. There are 5 more worksheets to give you a 2 dimensional tabular output of all the combinations.

Have fun, and maybe learn something.

David
1968 36/7988