Photograph by Buzzbo, Flickr. Vespa PX front brake lever.
Following our recent link to the excellent tutorial from the folks at scooterlounge.com, it’s appropriate that I’m also currently in the process of installing new drum brake shoes front and back on my ’84 Vespa PX.
Those of you with disc brakes should thank your lucky stars. The front drum brakes on vintage Vespas (and only slightly less so on Lambrettas) are notorious for being poor; but with proper care the brakes can be optimized to perform at their peak and can better the braking of a semi-hydraulic disc set up.
Remember the front wheel should provide 70% or more of the overall stopping power of your scoot so you want to make sure that your front brakes in particular are well cared for. However, generally because your foot can apply more (and more even) pressure to the back brake pedal, back drum brakes tend to be less problematic, but even they should be tuned regularly.
Fortunately, there are a number of key things you can take care of to improve drum brake performance on a vintage bike:
Actuation
First, let’s talk about a thing called the brake actuator. The actuator is generally a two-part mechanism. Outside the wheel hub it’s the move-able linkage that connects the end of the brake cable to an internal cam which in-turn pushes the brake shoes against the inside of the drum brake. That’s the essence of the entire braking system right there.
First, let’s talk about a thing called the brake actuator. The actuator is generally a two-part mechanism. Outside the wheel hub it’s the move-able linkage that connects the end of the brake cable to an internal cam which in-turn pushes the brake shoes against the inside of the drum brake. That’s the essence of the entire braking system right there.
The front brake actuator and linkage on a Vespa PX.
You should make sure that all the slack is taken up in the cable at the linkage so that any force you apply at the brake level or pedal immediately pulls the linkage without any movement wasted in slack. Some vintage models include a threaded nut that allows you to tighten the slack relatively easily. On other models you’ll either need a friend to help you pull the cable tight while you lock down the linkage with a wrench, or use a fourth-hand tool. Either way, keeping an eye on this slack should be part of your regular maintenance routine. Cables new and old will stretch during regular use so you need to keep on top of this every week or two.
Taking a look at the actuator, pull the linkage arm toward the axle by hand. It should only need to travel a very short distance before you feel the brakes engage inside the drum. If you need to pull a considerable distance before anything happens it’s a good indicator that the brake shoes are worn down and need to be replaced.
If when taking up slack in the front brake cable you find that it is necessary to pull the actuator part of the way closed just to take up any limpness at the brake lever or pedal then your brakes really need inspecting.
Cables
If you haven’t done so as part of recent maintenance, you should also consider using this opportunity to replace your brake cables and better yet, the cable outers. You want to ensure the smoothest transference of energy from depressing the brake lever at the handlebar (or foot brake) to the brake actuator linkage and lever at the hub. Any cable fraying can catch inside the cable outer and impede the braking process.
If you haven’t done so as part of recent maintenance, you should also consider using this opportunity to replace your brake cables and better yet, the cable outers. You want to ensure the smoothest transference of energy from depressing the brake lever at the handlebar (or foot brake) to the brake actuator linkage and lever at the hub. Any cable fraying can catch inside the cable outer and impede the braking process.
Look for Teflon-lined cable outers when replacing them. These ensure the smoothest possible slip between the outer and inner cable. And don’t forget to oil the new cable throughout.
Inside the hub
Now that you’ve done everything you can outside the hub, it’s time to get inside the wheel. Scooter Lounge’s tutorial covers this so I won’t go into detail, but I will re-iterate their words of warning:
Now that you’ve done everything you can outside the hub, it’s time to get inside the wheel. Scooter Lounge’s tutorial covers this so I won’t go into detail, but I will re-iterate their words of warning:
Old brake shoes release dust, which can contain asbestos, and you should do everything in your power to protect yourself. Before opening the hub make sure you have a dust mask that’s graded for asbestos. A disposable sawdust mask is not sufficient. You should also keep an old rag with brake cleaner handy so you can moisten the dust and wipe it away without releasing it into the air around you. Dispose of the rag when you are done. You might also want to use latex gloves.
First, the obvious – the drum brake shoes: These should be inspected and potentially replaced every 3,000 miles. It should be clear when you open up the hub if the shoes are ready to be replaced if you’re down to a thickness of less than 3mm on any part of the shoe. Scoring or marking on the existing shoes could also indicate a need to replace.
Some scooterists also recommend taking a hacksaw or Dremel tool to your new shoes to cut diagonal grooves into them about 3/4” apart. These grooves allow water and dust to escape freely from the shoes during braking. Be careful however to make sure you don’t cut the grooves too deep or you can compromise the structural integrity of the braking surface and cause the brakes to collapse in use. Not good.
Second, the not so obvious – the brake actuator cam: The two brake shoes sit snugly in the cam that is turned by the linkage outside the hub. As it turns, the cam pushes the shoes outward toward the drum. Push the actuator lever outside the hub with your hand and you’ll see what I mean.
Make sure the edges of this cam are square. They often become worn with wear and the corners begin to round. If the edges round too much, the cam looses effectiveness at pushing the shoes to the drum because the distance it can push them is reduced.
If you know that it’s been a few years since you replaced the cam then do so now and while you’re ordering replacements, order a couple of spares. They’re becoming harder and harder to find as modern Vespa clones switch to disc brakes.
Third: As you replace the shoes make sure you add a small dab of grease to the pivots that the shoes attach to. You should also grease the actuator cam where it turns inside the hub and where it makes contact with the new shoes. This grease will ensure that the cam operates smoothly and the brakes push and return smoothly.
Greasing the axel, brake cam and brake shoe pivots.
Be careful not to overdo the grease however. Any loose grease is in danger of being flung out to the drum as the wheel turns and you do not want grease anywhere near your brakes.
Finally, glazing: Past braking will usually leave residue inside the hub where the shoes meet the drum in the form of a glaze that further inhibits effective braking. You want to get rid of this crud.
Left: Glazing and brake dust. Right, after cleaning, sanding.
Take a look at the above side-by-side. On the left you can see the glazing residue inside the drum of my front brake. On the right is the result after sanding the glazing away with some 120 grit sandpaper. You should use anything in the 100-150 grit range and it should only take a couple of minutes of hand sanding to get them clean. Anything harsher could damage the roundness of the drums; anything lighter would be ineffectual. Again, watch out for the dust. Make sure you’re in a well-ventilated area and wearing your mask.
Wrapping up
With new brake shoes, turning on greased pivots, actuated by a square greased cam, with no cable slack, a clean drum surface and new brake cables you have done everything in your power to maximize the effectiveness of your brakes. Addressing any one of these issues individually should make a positive difference to your stopping power. Addressing them all at once should make your braking feel like night and day.
With new brake shoes, turning on greased pivots, actuated by a square greased cam, with no cable slack, a clean drum surface and new brake cables you have done everything in your power to maximize the effectiveness of your brakes. Addressing any one of these issues individually should make a positive difference to your stopping power. Addressing them all at once should make your braking feel like night and day.
As with anything to do with brakes and the front assembly of your scoot, take it easy on your first test drive. Test the brakes as you power walk the bike before getting up to speed and when you do brake, do so carefully at first. Keep your tool kit handy for at least the first couple of outings. Expect to tighten a nut here or there and pay particular attention to the cables, which will stretch more at first before they settle.
As should always be the case with braking, apply even firm pressure, don’t clamp down on them hard with either your hand or your foot. Your new brakes might surprise you in their effectiveness, and you’re opening yourself up to locking your brakes and flying off your bike. New shoes can be more prone to locking if they are slightly out-of-round until they have worn in.
That said, get out there and have fun with you new stopping distances. But don’t have too much fun.
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