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Rapide front brakes

danno

Well Known and Active Website User
VOC Member
Hi
Are Vincent brakes good when setup properly?
I've been riding my restored C Rapide when weather suits since last summer and find the front brakes
a bit spongey.
It's quite easy to pull the lever back to the bar so there might be some flexing happening somewhere.
Brakes are standard and haven't done much milage since restoration.

I need to spend a bit of time setting them up and any tips or info on this would be appreciated.
If there's not much improvement after that are there any upgrades available?
Dan
 

bmetcalf

Well Known and Active Website User
VOC Member
In KTB, there is a balance beam outrigger mod. Heavier cables are available, but I can never remember who sells them. Also, gussets can be added - http://www.vincentownersclub.co.uk/photos/showphoto.php/photo/2842/title/brake-mod/cat/646 and http://www.vincentownersclub.co.uk/photos/showphoto.php/photo/2843/title/brake-mod/cat/646

You can also "preload" the angle of the brake arm before tightening the brake cam nut to minimize the travel before the lining contacts the drum. It is also important to set the brake arms so the the angle of it and the cable is never more than 90 deg, the serrated washers can be rotated on the square shank for a vernier effect to enable fine tuning.
 

stumpy lord

Well Known and Active Website User
VOC Member
Hi,
you have here three different problems.

1 flexure of the fork bridge plate.

2 Flexure of the brake back plates.

3 flexure of the brake shoes.

number 1 can be cured by fitting an outrigger plate.


Number two by fitting gusset triangls to the back plates.


Number three is a lot harder to sort out due to the fact that when the brake is first applied , the first part of the shoe to contact the drum is the trailing edge, and from then on it is the shoe, due to its fixed pivot points, being forced to bend to contact the rest of the drum. Trever Southwell has a brake set up that has a cut away back plate that allows you to see the opperation of the brake, thats how I know that. The only answer that I know off is to have over size linings fitted to you brake shoes , mount them on your brake bake plates with a shim between the heel of the shoe and the cam, and turn them to suit the dimension of your brake drums.

You do not say how good your brake are ? Do you have to pull the lever right back to the bars to get a decent brake effect? or is it
a case that they are O.k. but you dont like the sponge feeling.


When I had drum brakes on the Vin I would always adjust the cables so that when the front left hand brake was just touching the drum, the right hand one was just about to touch its drum , I mention this because I have seen many members bikes where the right hand brake is trailing a long way behind the the left hand brake,
. where as both brakes should be sharing the work evenly.


with all these mods it is possible to have front brakes that will squeal the front tyre.

cheers stumpy lord.
 

Glenliman

Well Known and Active Website User
VOC Member
"Are the Vincent brakes good when setup properly?"

Well they outdo the 1st generation disc brakes on my MK3 Commando.

The link below is a dramatic reenactment of an actual Vincent braking/dog on the road event that occurred earlier that day. Sort of. With a lot of poetic license and a fair bit of plain BS. But the stop is real, and pretty quick too!

http://www.youtube.com/watch?v=amMPrwtuz2U
 
Last edited:

Glenliman

Well Known and Active Website User
VOC Member
Yes, it squishes down quite a lot from the weight transfer. I checked it afterward and it was just a bit lower than I usually keep it . It was at 23 lbs.
Pull just a little harder on the front brake lever, the wheel locks up. This happened to me a couple of times at speed until I got accustomed to the brakes.

My other Rapide has decent brakes, but nothing like this one. I guess everything is in sync.
Green Ferodo linings, Lightning type back plates , aluminum copies, not the original Magnesium type


Glen
 
Last edited:

vibrac

Well Known and Active Website User
VOC Member
Wow! well into this thread and nobody has trotted out the well used but never the less true fact
loosen the front spindle ,pull on the brakes hard, hold them on, and do up the spindle

(you can let the lever go now :)
 

danno

Well Known and Active Website User
VOC Member
Blimey! Nice stoppers.
I need to study how the brakes work as I've not worked on them before.
I've got both Paul Richardson's book and KTB.
Also not sure what brake parts Conway Motors fitted during restoration so may take a look at the drums.
 

davidd

Well Known and Active Website User
VOC Member
I need to spend a bit of time setting them up and any tips or info on this would be appreciated.
If there's not much improvement after that are there any upgrades available?
Dan
Dan,

Stumpy's reply is a good template. The best way to start is to make sure the cables are new and big (resistant to flex). All the mods are beneficial, but do the cheap improvements first to see if you are happy. A good brake lining is important. Old ones tend to be hard and slippery.

Clever Trevor discovered that the sponginess in the brakes may be due to a geometry error. The various attemps to rectify this is truing the brake linings on a lathe, the Burt Weiz floating pins mod in MPH and the Tim Kingham mentioned mod. This last mod was a favorite here in the States used Rick Voshel and Marv Kummet. They would file the axle hole in both brake plates so it was a little large. When they installed the wheel they would leave the hollow axle nuts a little loose. With the wheel still in the air they would hold the brake lever tight causing the shoes to align the brake where it should be. They would use a special thin wrench to tightn the hollow axle nuts while the brakes were on. The wrench is now made by Niel Videan in Australia (see adver in MPH).

There are three popular upgrades. The 8 inch brakes, the 4 leading shoe conversion and disc brake conversion. The first two are easily available the third you will need to do yourself. I have been told the 4 LS conversion in quite good. I use the 8 inch brakes as 4LS brakes are illegal in the racing rules I have to comply with. I find them quite good on the track. If you have Rapide drums you should consider new Black Shadow drums if you are doing the 4LS conversion. I have shattered Rapide drums.

Finally, if you are running stock springs on the front end your stopping distances will be longer because the front end does not go up and down very easily during braking. Glen's video seems to show this as his tire flattens so much. Even with low tire pressures the front springs should be compressing as the weight transfers to the front end but because the forks are seizing the springs do not compress, the tire does. Very impressive!

David
 

Glenliman

Well Known and Active Website User
VOC Member
Hi David.

After reading your post I had to view the video a couple of times to see what was happening with the front end. The part of the clip where the bike approaches the stop firstshows the front end after the brakes have already been applied. It is difficult to gauge fork action until the braking ends when the bike stops. When the bike stops, you can clearly see springs pop up and my upper body get thrown back. It looks to be quite a lot of fork action, difficult to say exactly how much.

It looks as though the springs compress about as much as they can then, as you say, the rest is done by the tire.
Glen
 
Last edited:

A-BCD

Well Known and Active Website User
VOC Member
I'm fairly sure that girder forks, and particularly Girdraulics, do not compress the springs under braking, rather the reverse, and the front end can rise and extend the springs ? Also I think Girdraulics tend to not move at all under heavy braking ?
 

davidd

Well Known and Active Website User
VOC Member
I'm fairly sure that girder forks, and particularly Girdraulics, do not compress the springs under braking, rather the reverse, and the front end can rise and extend the springs ? Also I think Girdraulics tend to not move at all under heavy braking ?
That is my point. If I run over a speed bump under full braking, my Girdraulic forks go up and down. The springs will compress under heavy braking. With stock springs the front end can only rise or go to full extension. It will not return to its static position until you release the brake. Girder forks will go up and down under full braking if you are in the middle of their range and not at the extremes. This effect alone has generated a lot of affection for the Bramptons among many owners.

David
 

danno

Well Known and Active Website User
VOC Member
Dan,

Stumpy's reply is a good template. The best way to start is to make sure the cables are new and big (resistant to flex). All the mods are beneficial, but do the cheap improvements first to see if you are happy. A good brake lining is important. Old ones tend to be hard and slippery.

Clever Trevor discovered that the sponginess in the brakes may be due to a geometry error. The various attemps to rectify this is truing the brake linings on a lathe, the Burt Weiz floating pins mod in MPH and the Tim Kingham mentioned mod. This last mod was a favorite here in the States used Rick Voshel and Marv Kummet. They would file the axle hole in both brake plates so it was a little large. When they installed the wheel they would leave the hollow axle nuts a little loose. With the wheel still in the air they would hold the brake lever tight causing the shoes to align the brake where it should be. They would use a special thin wrench to tightn the hollow axle nuts while the brakes were on. The wrench is now made by Niel Videan in Australia (see adver in MPH).

There are three popular upgrades. The 8 inch brakes, the 4 leading shoe conversion and disc brake conversion. The first two are easily available the third you will need to do yourself. I have been told the 4 LS conversion in quite good. I use the 8 inch brakes as 4LS brakes are illegal in the racing rules I have to comply with. I find them quite good on the track. If you have Rapide drums you should consider new Black Shadow drums if you are doing the 4LS conversion. I have shattered Rapide drums.

Finally, if you are running stock springs on the front end your stopping distances will be longer because the front end does not go up and down very easily during braking. Glen's video seems to show this as his tire flattens so much. Even with low tire pressures the front springs should be compressing as the weight transfers to the front end but because the forks are seizing the springs do not compress, the tire does. Very impressive!

David
Great thanks. Plenty to go on there.
I'll see if I can improve things with the current setup first.
Regarding the 8" brake upgrade, my brake drums are 8" diameter.
Dan
 

danno

Well Known and Active Website User
VOC Member
I measured outside diameter. They have a chrome surround riveted on which measures just over 8".
No air scoops so guess they're standard Rapide drums.
 

davidd

Well Known and Active Website User
VOC Member
Dan,

The measurement is the inside diameter of the brake drum. The stock drums are 7 inches. The Club shop sells an 8 inch brake that has Lightning style alloy plates and the shoes are much wider. Glen has the same type of plate on his Rapide in the video. These Lightning plates are alloy, the originals were Elektron, and are stiffer. Vincents with Lightning plates have no thin hollow axle nuts as there is not enough space with the thick brake plates. Most owners like them because they provide more stiffness while having an original racing look to them. If your drums do not have fins, they are 7 inch Rapide drums. If they had fins, they could have been 8 inch drums but they would have to have the special 8 inch Lightning style plates. The stock 7 inch racing brake plates do not use the alloy water excluders (the "surround"). On the 8 inch brakes the appearance of the water excluder is turned into the alloy plate itself.

I think you will do well if you do the simple items first. It may take a while to get used to all of the adjustments. The best brakes are always adjusted well and there is a bit of experimentation involved.

Best of luck!

David
 
Last edited:

clevtrev

Well Known and Active Website User
VOC Member
Dan,

The measurement is the inside diameter of the brake drum. The stock drums are 7 inches. The Club shop sells an 8 inch brake that has Lightning style alloy plates and the shoes are much wider. Glen has the same type of plate on his Rapide in the video. These Lightning plates are alloy, the originals were Elektron, and are stiffer. Vincents with Lightning plates have no thin hollow axle nuts as there is not enough space with the thick brake plates. Most owners like them because they provide more stiffness while having an original racing look to them. If your drums do not have fins, they are 7 inch Rapide drums. If they had fins, they could have been 8 inch drums but they would have to have the special 8 inch Lightning style plates. The stock 7 inch racing brake plates do not use the alloy water excluders (the "surround"). On the 8 inch brakes the appearance of the water excluder is turned into the alloy plate itself.

I think you will do well if you do the simple items first. It may take a while to get used to all of the adjustments. The best brakes are always adjusted well and there is a bit of experimentation involved.

Best of luck!

David
And even if they have fins, they are 7" brakes.
 

peter holmes

Well Known and Active Website User
VOC Member
And even if they have fins, they are 7" brakes.
I do not think that Trevor quite understood the point that David was making, the club 8inch brake drums are only manufactured ribbed, not plain, the original 7inch drums are made ribbed and plain, therefore if you are looking at an 8inch drum it can only be ribbed, a 7 inch drum could be either be ribbed or plain.
 

redbloke1956

Well Known and Active Website User
Non-VOC Member
I have some very good info from a club member in AJS club that has been comprehensively tested, it involves removing about 2 inches of brake shoe from all trailing edges, therefore forcing the leading edges to make contact first. Kevin
 

Matty

Well Known and Active Website User
VOC Member
Hi
This subject has been on the forum for years and has been covered in some detail on the forum at :-


Matty
 

Matty

Well Known and Active Website User
VOC Member
Hi again
Surprised to hear that there is some dive on people's Vincent forks - mine have never dipped appreciably on braking and I was always led to believe after 60+ years of ownership, that this was their greatest merit.
Perhaps it is because my brakes have never worked properly and the bike has only been used as a tourer for the last 100,000 miles or so!!
Matty
 

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