G15 speedo

G15 Technical Guide - speedo

When the G15 was originally conceived the factory intended to use Imp front suspension, but this idea was scrapped in favour of the Triumph set up due to the cost involved in converting the front drum brakes to the Chrysler Competition disc brake assembly. It was therefore necessary to drive the speedo from the nearside front hub.

The unit fitted to the G15 is modified from a Smiths Industries part which was fitted to the back of the strip speedo used on the Rover 2000 and a few other BL cars.  Over the years this arrangement has caused G15 owners a number of problems and there are several reasons why this unit may fail.

1) The angle drive is fitted directly to the nearside front hub, so is vulnerable to dirt and grit, which will cause wear in the plastic drive gears.

There are a number of ways of reducing this problem:

• Thoroughly clean the unit and spray it with Damp Start
• Cover the complete angle drive with a plastic bag or similar to keep water and grit at bay.
• Ensure all joints are sealed with a smear of Hylomar or equivalent.

2) Failure may also be due to excessive friction in the driveline.

To avoid this problem:

• Ensure there are no kinks in the cable.
• Make sure the cable runs inside the triangle of the top wishbone and not outside it.

3) Cuts or wear in the outer cable allows dirt and grease to find its way down into the drive gears. Check it regularly.

It is also worthwhile checking that the bearing in the speedo head has not seized in its housing. This bearing can be lubricated with a couple of drops of light machine oil.