LAMBRETTA Riders

Yes they do.

You can raise or lower your gearing easily by fitting a different profile tyre.

A 100/90:10 tyre can be used to raise the gearing and a 3.50:10 or 100/80:10 can be used to lower the gearing. The difference can be likened to raising or lowering your engines front sprocket.

Yes, if you use a 100/90:10 or a 3.50:10 which has a similar diameter and rolling circumference and your scooter struggles in 4th then try a lower profile 100/80:10 tyre on the rear. Altering a tyre size on the front makes no difference to gearing only handling. (But could effect how accurate the speedo may read)

It depends how you look at it.

This is the correct way:

High gearing is when the gearbox and drive ratio have a low number, the worst case is a GT200 gearbox with a drive ratio of 4.44:1. A low ratio in the worst case is a GP125 with 6.14:1.

This means for the GT box in 4th gear, the crankshaft has to turn 4.44 times to spin the rear wheel once, whereas the GP125 crankshaft has to spin 6.14 times per one wheel rotation.

Every engine is different. Various factors affect gearing:

1. Engines pulling power, expressed as torque. (i.e. a torquey engine)

2. The weight the Scooter needs to carry.

3. Tyre diameter and rolling radius.

4. Gear ratio.

Tyres are basically the same except for some rolling radius (see tyre charts) There is only so much rubber that will fit between the engine, hub and mudguard. Usually a large capacity engine with a lot of torque can pull higher gearing. An engine made to rev and produce power high up in the rev range may not have the low down torque, so a higher revving gearbox may be required and the same could apply to a gutless standard engine.

Extra weight will always put a strain on a Lambretta engine.

In the grand scheme of things a Lambretta is not a very powerful engine so by adding another body the engine will naturally find it harder to pull, especially up hill, into the wind and if you are out of the engines power band.

For these reasons, gearing is very important and a tyre effects gearing so much.

If you find you are happy with the gearing driving on your own, but the engine doesn't like two up riding why not keep a spare tyre with a lower profile!

It is much easier to change a tyre than it is to change a gearbox or sprocket sets. A lower profile tyre gives less drag or load on the engine and allows the engine to spin more freely as the overall gear ratio is lowered. Changing the tyre profile is a much easier job to do than splitting your gearbox to change gear ratios.