‘Hydra’ Hydraulic rear brake conversion for Lambretta | NEWS
A simple bolt-in hydraulic conversion for the Lambretta rear drum hub is Tino Sacchi’s latest project and quite an exciting one.
Why is it needed?
There are those who say that rear brakes are not important if you’ve got a good front brake. Quite frankly this is a load of poppycock spouted by those who listen to motorcyclists too much.
On a motorcycle you have a high centre of gravity and the vast majority of the mass of rider and bike end up on the front tyre so that is the tyre you need all the braking power on while the rear brake does very little.
Scooters are not motorcycles. Scooters – and particularly Lambrettas carry much more of their weight directly over the rear tyre. This is why many scooters have the same sized brakes on the back wheel as the front. So, if you want to stop fast, the rear brake is just as important as the front because the rear tyre still has lots of weight on it under braking. That weight translates to unused grip for slowing down if you only have a strong front brake.
Sadly, when upgrading scooter brakes everyone seems to ignore this fact and we end up with double fandabidozy discs on the front wheel and a poorly set-up cable drum brake on the rear.
Why upgrade a Lambretta drum brake
I’m repeatedly told that excellent Lambretta rear drum brakes do exist in the wild, but they are rare beasts. Mostly, they tend to be as effective as a tent in a tornado. Some of the problem is that the design is poor. Another is that the spare parts are equally poor (why else would Innocenti produce a ‘brake shoe skimming tool’?). On top of a poor design and poor spares we also have the situation where SIL managed to drill the brake shoe pin holes in many casings off centre so that only one shoe touches the hub. Until you use a brake shoe skimming tool at least.
The theoretical advantage of a hydraulic rear brake is not simply one of mechanical advantage over the very crude cam system, it is also one of adjustment.
How does it work?
Tino’s Hydra rear brake system uses special brake shoes which are forced apart by an opposed piston hydraulic slave, much like that of the Piaggio Ape or Vespa Cosa. With hydraulic actuation, both brake shoes will inherently be forced against the hub with equal force, even if the pins for the shoes are misaligned. What is more, the hydraulic system should be capable of self-adjusting to cope with brake shoe wear.
The Hydra kit will come with a clever cable-operated master cylinder that bolts directly to the rear floorboard strut with a special clamp on mount for the fluid reservoir to attach behind the top rear shock mount.
When will it arrive?
At the moment it’s too early to say, or indeed what the price will be. Franco – the designer – has one of these systems already operational in his Lambretta but Tino wants it to undergo more miles of testing before putting the product on the market.
Hopefully, we’ll be able to bring you a report on how it works very soon.
New products always in development…