stopping power for a Lambretta isnt limited to hydraulics

[marktheskin]

so the only chances of the front brake completly locking up are if your shoes are badly worn or not adjusted up properly right?

[victor]

so the only chances of the front brake completly locking up are if your shoes are badly worn or not adjusted up properly right?

Doing reverse pull is like getting stronger grip... without going to the gym... So IF it can happen it can happen in either case, and I believe that would require some extensive braking...

Even if the "cam locks" it doesnt really matter. If it locks, you'd be unable to stop breaking. If it locks with the wheel locked (not rotating), the wheel would have locked up before the cam HYPOTHETICALLY would have locked up anyway (as the amount of braking is increased linearly), and you'd have released the pressure on the lever, thus never allowing the cam to lock up.

If the shoes are that badly worn that the wheel do not lock up when the cam hypothetically locks, then you still don't have any problem as you'd just continue braking controllably until you reach stop.

Difficult to describe, but the bottom line is, regardless of whether it's possible to "lock the cam" or not, keep your brakes safely adjusted and you needn't worry

[purple_pill67]

Will all these tricks work on a scootrs inboard that judders the headset more than slows me down?
I tend to use my back brake anyway but would be nice to have a front brake that does something.
(I got the inboard as my remade drum was knackered when I got knocked off so needed a new front hub and that anyway)
I guess sintered pads help?
And replace the speedo drive as the mph needle works if a little juddery but i have done no miles riding it daily to work for the past few months since being back on the road.

[dirtyhandslopez]

When you set up a reverse pull on a drum be careful.
As the suspension allows the links to move upward because of the braking force, the cable applies more pressure to the brake arm, increasing the braking power, then the suspension lets links go up more, ad nauseum, etc, etc. Before you know it, the brake locks up.
Ran a drum set up like that for many years but it was definately hairy.

[coaster]

When you set up a reverse pull on a drum be careful.
As the suspension allows the links to move upward because of the braking force, the cable applies more pressure to the brake arm, increasing the braking power, then the suspension lets links go up more, ad nauseum, etc, etc. Before you know it, the brake locks up.
Ran a drum set up like that for many years but it was definately hairy.

There's supposed to be a reason why reverse pulling a front drum brake isn't a good idea but I'm feked if I can remember what it is now

Thanks Lopez I new there was a reason, just couldn't quite remember what I'd been told.

With the standard front pull the inner is pulling through a cable with a 180 ish degree curve. As the cable tightens the friction will increase and the harder you pull the lever, the lower the pull will be on the brake for a given effort. This would mean that the point of lock up is reached very gradually. The same suspension dipping mentioned by Dirtyhandedlopez will increase the radius of the cable and further increase the resistance. The drum barake SHOULD work fine without resorting to the reverse pull which is only a bodge to get around a more fundamental problem imho. I would say using a good quality nylon lined cable routed as Innocenti intended and some properly fettled shoes should give you a decent brake. The one on my Jet was fine and the standard brake on my T5 was good enough around London on its own through one winter when the rear pedal siezed up

[dirtyhandslopez]

Twas pleasure.

I reckon the official term might be a servo effect taking place. Or something like that.

[victor]

When you set up a reverse pull on a drum be careful.
As the suspension allows the links to move upward because of the braking force, the cable applies more pressure to the brake arm, increasing the braking power, then the suspension lets links go up more, ad nauseum, etc, etc. Before you know it, the brake locks up.
Ran a drum set up like that for many years but it was definately hairy.

I really do not believe this to be correct.

If you hold a cable with it's inner fitted in your hands and bend it, the length of the inner will not "decrease" and and exactly the same length of the inner cable will be visible outside the outer no matter how much you bend it or roll it.

The amount the cable is bending during diving is neglectable and since the outer and the inner cable are attached to the same part, with the distance between the attachment-points being constant during suspension unless the lever is pressed, there should be no effect due to the suspension moving.

This can be proven easily by fitting a reverse pull to a scooter without the fork springs fitted and moving the drum up and down.

[Muppet]

Twas pleasure.

I reckon the official term might be a servo effect taking place. Or something like that.

iremember reading this in one of the old crumby 60' motorcycle/scooter mags i did the conversion on my disc it was fantastic had braking power in heaps; did it to a drum brake the fecker locked up to easy an threw me off twice the outer pushes down more as the suspension moves up under braking this increasing braking power which adds to the suspension movement with increased braking; the suspension movement on its own dont efect the cable unles the brake is being pulled; sort of servo assist when its needed; for me an those with slower reflexes never on a drum brake,
muppet,

[victor]

Twas pleasure.

I reckon the official term might be a servo effect taking place. Or something like that.

iremember reading this in one of the old crumby 60' motorcycle/scooter mags i did the conversion on my disc it was fantastic had braking power in heaps; did it to a drum brake the fecker locked up to easy an threw me off twice

Correct, servo effect, it's as if you are stronger so you might be able to lock the brake. The front brake on my SS is ridiculously sensible and locks up for nothing when it's humid outside. Phasing of the edges of the abrasive material on the shoes made it a lot better though.

the outer pushes down more as the suspension moves up under braking this increasing braking power which adds to the suspension movement with increased braking; the suspension movement on its own dont efect the cable unles the brake is being pulled; sort of servo assist when its needed; for me an those with slower reflexes never on a drum brake,
muppet,

And this is where I believe the misconception is lying; if the outer cable was attached to another part than the drum, say the forks, and the inner cable to the drum/brakepivot arm, then this would be correct.

But as they are attached to the same part the suspension does not at all affect the amount of braking. If this was the case, this would happen with normal routing too, independently of whether the cable is attached from the front or the rear of the drum

I fully believe it's easier to lock up the front drum brake with reverse pull as you get the "servo effect" with shorter and straighter routing, but the suspension does not affect this. Drum brakes are generally easy to lock up and offer little sensibility and graduation between 0 and full/lock up braking power, and the ease obviously increases as you are able to operate the brake with more power.

Still, I repeat, it's unrelated to the movements of the fork links.

I also agree that a properly adjusted front drum brake with good shoes and a nylon lined cable should be enough to have decent braking power.

Remember also that during braking, about 80% of your grip is on the front wheel (with other word 80% of your ability to brake without skidding), so having a good front brake is fundamental.

[ducksta]

can you reverse pull a vespa px drum brake?