Mod to improve 7" front brake.

[Derek996]

Reading Janacek's post about the poor front brake on his bike reminded me that there is a mod to improve the 7" front brake  fitted to the older machines but I can't find any details about this anywhere. Does anyone on here know what the mod is?

[V500]

The simplest mod would be to change it to an 8" Single-sided brake, as I did on my Star Twin, and it's a great improvement.
That said, the 7" brake on my ZB32 works far better than the original ST one ever did. New softer linings from Villiers Services and some laborious fettling worked wonders.

[limeyrob]

Having swapped out a 7" front brake on a 55 B31 for an 8" off an A10 its a huge improvement and a very simple mod.  No parts need to be altered, the A10 brake stay and wheel spindle fit straight on and the fork lug does not clash.
The key to the 8" is that its a cast drum not a pressed one so its much more rigid and runs truer.  Over time the 7" can get warped by the spoke tension.
I wasted a lot of time on the 7" getting the drum machined and shoes etc but the 8" was so much better straight away.

[Derek996]

The simplest mod would be to change it to an 8" Single-sided brake, as I did on my Star Twin, and it's a great improvement.
That said, the 7" brake on my ZB32 works far better than the original ST one ever did. New softer linings from Villiers Services and some laborious fettling worked wonders.

I agree and having had past experince with the 8" brake I know that they are far better. However, my bike is 1948 and I would prefer to keep the original appearance as far as posible and to complicate matters it has a 21" front wheel. Changing to an 8" hub would require rebuilding the wheels with suitable length spokes. I'll be happy just to get a little improvement with the existing brake. I have made sure the shoes are centred but have no idea what linings are fitted, they came with the bike.

[limeyrob]

Then the "best" solution is to get the wheel spokes tensions right then send the wheel and brake to a specialist to have the drum skimmed and the brake shoes turned to fit with a modern high friction lining.  The problems is the diameter as you want to find someone who can munt the whole wheel. A lot of places will do the hub/drum but that means rebuilding the wheel with the risk of distorting the drum.
The common fix if its an offroad bike is to have two front wheels, the standard one and one with a modern Jap alloy brake, this will get you a nice light 6" or 7" hub/brake that works well and these are often 21" as they come off trail bikes.  I was looking at brakes a the Talmag as I have a 350 Matchless set up as a trail bike, about 50% of the pre-65 bikes had small Japanese/Spanish/Italian front hub / brake units on 21" rims

[neil1964]

I have had similar experiences with front brakes, 7"-> 8"-> and ultimately the Pearson version of Dow in A65 wide finned drum. Light years better.
However I too have a '57 competition as a trail bike with newly made 21" rimmed front 7".
I did the 'lapping' with self adhesive abrasive on the shoes and then in the drum, centred and arm adjusted correctly with decent cable. Better but still a 'slower downer' vs a 'stopper'.
I am currently modding a plate to TLS as per an article from A7/A10 forum. This requires an extra cam and cam spindle tube and splitting both fulcrums and adding them to one side of each cam. Still requires a new stay and good cable. I've lots on so slow process as I've pinched the diamond shaped plate support and spindle the off a scrap plate.  It is an experiment and of course the pressed up plate and drum are limiting factors. I'll try to find the link to the article.

[Derek996]

That sounds like a good mod Neil. I'd certainly be interested in the article if you can find it. It shouldn't be too difficult to find a use 7" brake to experiment with.
I feel that my current brake is probably as good as expected in it's current form, like your's it's a slow downer" rather than a Stopper". I like that analogy.

[neil1964]

Here is a link:
https://www.a7a10.net/forum/index.php?topic=7691.0
You may have to join the forum to see pics etc
I am using straight levers (although I have a set of cranked Triumph ones)
I've not decided whether to locate the backplate with boss or flat stay yet, to get cable run and cam angles at optimum positions.

[Derek996]

Thanks Neil. I can see all the pictures without joining the forum and will cut and paste all the pictures and relevant text into a document of my own for reference. I'll now start looking for a used 7" brake to work on.

[limeyrob]

There are other ways to do something similar:
Get two brake plates and cut them in half then weld the two halves with the bosses in to make a single TLS plate.
Get two hubs and saw then in half and join in the middle to make a double sided brake.  This has the benefit of giving a lot more heat dissipation area and is used for racing.
Adapt a new Royal Enfield 7" TLS brake plate, they are only about £60 new with shoes and levers (from India).

[Derek996]

Adapt a new Royal Enfield 7" TLS brake plate, they are only about £60 new with shoes and levers (from India).

At that price it could be worth a go.

[V500]

The quality of those is abysmal.

[limeyrob]

Yes, it looks too wide but its an ally plate and of course the shoes are ally so it may be a case of getting the saw out.  I had a look at the photos on e-bay and I think its got potential.  Perhaps you can get your hands on one and measure it? Just google "7" TLS brake" and plenty of the RE ones will come up.

[limeyrob]

The quality of those is abysmal.

As least you won't feel guilty taking a saw to it..

[neil1964]

Thanks Neil. I can see all the pictures without joining the forum and will cut and paste all the pictures and relevant text into a document of my own for reference. I'll now start looking for a used 7" brake to work on.

Suggest you crack on with it (based on my exerience this am) met two huge tractors in lane this am. Car in front slowed and stopped.  I slowed and did not stop!!