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Old 11th June 2024, 22:43   #1
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Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

Owners of a Standard Bullet 350 can relate to the maintenance required to keep the brakes in good condition. Granted, it's a wonderful mechanism but it also brings with it, double the headache if setup improperly. I'll take you all through a brief about the braking system and then through how I reset the brakes on my motorcycle to a near factory level of smoothness and far greater braking efficiency than it ever had.

The twin-lead brake system
With Disc brakes becoming the norm in almost all motorcycles now, the classic drum brakes have faded away into history but let's not forget the following
  1. They are simpler because they're mechanical systems as opposed to hydraulic systems on disc brakes.
  2. They're less prone to being affected by dust, water, mud etc. This is not to say they're foolproof but they're less delicate. A disc on the other hand can easily get scored by debris and start screeching.
  3. They marginally contribute to the fuel efficiency of the vehicle. Drum brakes have a higher clearance between the friction material and the brake drum. Discs on the other hand have little to no clearance when in the no-load condition. This results in a base-level friction always being present. With this friction eliminated in drum brakes, the wheels rotate a little more freely, although the difference is marginal.
These drum brake systems initially came with just one actuator and a passive hinge point to push out two brake shoes simultaneously out against the drum and provide braking force.
Later, improvements were made to make both the brake shoes push actively against the drum. This was achieved by using twin leads which were mechanically coupled. This meant that the brake system was a lot more powerful but also needed careful alignment. Otherwise, the system had a risk of one brake shoe wearing off while the other did not make contact at all.
Coming to my Bullet, the brake was in pretty bad shape. Spongy braking, little to no bite, sudden judders, brake lever getting stuck in the actuated position and so on. Service centre visits were fruitless because the only thing they knew to do was replace parts one by one. I decided to get to the heart of it.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240523_214327.jpg

Sat down in the garage and opened up the front wheel fully. I was astonished at the heaps of brake dust and muck that came out. Goes to show that the service centres never touch anything that is not instructed specifically to them - Forget customer satisfaction.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240523_214334.jpg
Apart from the spongy feedback, the more pressing issue was that the actuators did not return back to the starting position after letting go of the lever. I took apart the entire brake assembly and found out that the rounded edges of the rectangular cams that actuate the brake shoes had become flat due to wear and tear. I couldn't get images of the condition of the cams before I worked on them. This is the cam after rounding off the edges with sandpaper.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240523_214345.jpg

The flat face of the brake shoes where the cam made contact had also worn out and become full of ridges which was also a reason for the cams not returning to their starting points.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240523_214407.jpg

This face was sanded down with oil and 220 grit sandpaper to remove the ridges as much as possible.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240523_225233.jpg

The hub was also oil-sanded to a smooth finish, getting rid of all the rust spots. The pivots were greased and the entire assembly was put back. Pictures of the re-assembly were unfortunately not backed up. Here's the guy after reassembly and ready for testing.
Standard Bullet 350 | Overhauled the twin-leading drum brake system at home-img_20240524_001637.jpg

I did a couple of stationary actuations, adjusting the lever play and the cable tightness before taking the bike out for a spin.
There was no point in taking it out for a 100 - 0 kph test or anything so I just did two slower speed tests.
  1. 40-0 kmph: 6.5 metres
  2. 50-0 kmph: 11 metres
The official brake distances for the bullet 350 are nowhere to be found for some reason. However, the latest classic seems to drop from 60 to 0 across nearly 18 metres. The above values extrapolated to 60 metres seem to come close to this. However, there are multiple variables to consider here.
  1. The classic is heavier by nearly 10 kgs which can alter braking distance by a huge margin
  2. The new classic has front and rear disc brakes whereas I have dual drums
  3. The tested speeds being different play a huge role in determining the braking efficiency
  4. The engine braking levels of the old and new models vary quite a bit
Hence, a bullet to bullet comparison would only tell if mine works well or not.
However, for a general ballpark, I think the brakes are now performing quite adequately and have a good strong bite when required.
The same work for the rear brake is now on the to-do list. Already did the cleaning and sanding for the rear drum once but I did some extreme daredevil riding in a road filled with almost a foot of thick mud. God knows how I escaped without falling or getting irreparably stuck there. So yeah, the rear will also need work which is for another post, another day. Until next time, cheers!

Last edited by that_sedate_guy : 12th June 2024 at 11:32.
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Old 12th June 2024, 17:58   #2
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

Thread moved from the Assembly Line to the Motorcycle section. Thanks for sharing!

Going to our homepage tommorow
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Old 12th June 2024, 18:19   #3
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

Quote:
Originally Posted by that_sedate_guy View Post
The above values extrapolated to 60 metres seem to come close to this.
Made an error here. It's 60 kmph and not 60 metres. Apologies everyone!
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Old 13th June 2024, 12:16   #4
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

Quote:
Originally Posted by that_sedate_guy View Post
Owners of a Standard Bullet 350 can relate to the maintenance required to keep the brakes in good condition.
See if you can get a disc brake conv done, it costed me 6K some 10 years ago, converted my Taurus from the 7" dual piston to disc brake. Dont ask why a 70Kmph top speed Taurus needed the disk!

PS - Are you in any Jacpel & Co Property in Hosur? Those Red/White tiles and the grey water taper plumbing with a stack of bricks to support them is their trademark. Dont ask me how I know.
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Old 13th June 2024, 16:44   #5
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

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Originally Posted by svsantosh View Post
See if you can get a disc brake conv done, it costed me 6K some 10 years ago, converted my Taurus from the 7" dual piston to disc brake. Dont ask why a 70Kmph top speed Taurus needed the disk!
I did play with the idea of a disc conversion but I dropped it soon after because my OCD just does not allow me to live with a disc at front and a drum at the rear. Converting the rear also to a disc seemed neither straightforward, nor wallet-friendly. Hence flew away the idea.
And oh my God a Taurus! Confusing petrol station guys by asking for diesel, the loud thunderous thump, the physics-defying fuel efficiency and what not. Such an awesome bike that was. Sadly, RE never bothered improving it and kicked it out of their portfolio.


Quote:
Originally Posted by svsantosh View Post
Are you in any Jacpel & Co Property in Hosur?
Hahaha I live in a different layout in Bagalur road. Those bricks, pipes etc. are all my doing. I'm in the process of making some sustainability mini-projects at home and the pipes are for one of them. And the tiles, yeah they're commonplace but were selected individually in my case
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Old 13th June 2024, 22:40   #6
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

hi great diy, i am from hosur too, and I love DIY and wrenching, if you ever need a spanner mate or a hand with any of your projects I would love to assist you.
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Old 13th June 2024, 23:03   #7
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

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Originally Posted by that_sedate_guy View Post

Hahaha I live in a different layout in Bagalur road.
sorry posted twice because of a loading error, mods kindly delete the post. sorry for the trouble.

Last edited by adrift@life : 13th June 2024 at 23:04. Reason: internet loading error
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Old 13th June 2024, 23:03   #8
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Re: Standard Bullet 350 | Overhauled the twin-leading drum brake system at home

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Originally Posted by adrift@life View Post
hi great diy, i am from hosur too
This is really great seeing Bhpians coming around! I for one, am always on the lookout for making anything and everything for my motorcycle by myself and just the thought that someone's near and ready to take part in a common passion is always a huge comfort factor. I'll be sure to rope you in!
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