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FF: Forks More Brampton Woes


ogrilp400

Well Known and Active Website User
VOC Member
G'day All,
Another problem has presented with these Bramptons. This one I have not encountered before but some one in Australia did ring and ask me about this same same problem. Sorry I can't remember who it was. Have a look at the angle of the fork links. The forks are as near as to full extension. There is only a very small clearance between the fork and the stem cross piece. These are new Bramptons What is going on here? I have been for a very short ride and the fork action is very pliable. My guess is that the spring is too long and/or is a sidecar one. Ideas?

Phelps
 

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Robert Watson

Well Known and Active Website User
VOC Member
Go and look at many sets of Bramptons and see just how many hit the back of the rear down tubes on the stem cross piece.
Any one for a survey?
 

genedn

Well Known and Active Website User
VOC Member
Top nut on most is stamped either 180lb or 160lb. I believe without looking the solo spring should be 9 7/8” long. KTB has all the spring details.
 

davidd

Well Known and Active Website User
VOC Member
Phelps,

That looks like way to much spring in there. With the stock Brampton unladen the lower link should be no higher than parallel to the road and laden it should look a little "saggy".
1947The_Motor_Cycle_1.jpg

1947SpitfireRapideSmall.jpg


David
 

Albervin

Well Known and Active Website User
VOC Member
G'day All,
Another problem has presented with these Bramptons. This one I have not encountered before but some one in Australia did ring and ask me about this same same problem. Sorry I can't remember who it was. Have a look at the angle of the fork links. The forks are as near as to full extension. There is only a very small clearance between the fork and the stem cross piece. These are new Bramptons What is going on here? I have been for a very short ride and the fork action is very pliable. My guess is that the spring is too long and/or is a sidecar one. Ideas?

Phelps
Is that on side stand, with a rider on it or on rear stand. It looks way too extended either which way.
 

Albervin

Well Known and Active Website User
VOC Member
When you say new> Do you mean Mike Breeding forks? They are the only NEW ones I know of. I have a set of his on my Rap and they are nothing like this. He does buy in the spring and other hardware so it is not down to Mike that it is sitting like this.
 

Oldhaven

Well Known and Active Website User
VOC Member
My Bramptons on the '48 Rapide have obviously been up against the stem cross piece before and are dented there. I see one new chip in the dent area but when my brother repainted the forks long ago the dent was there then. Also in this picture you can see the white mark or chip where the steering stop is hitting above the rib, so there you have another data point for that discussion.

IMG_1709.jpg

I have an 180 pound original spring on it now, but for most of its life since my rebuild it has had a Thornton (Works) spring over conversion, and it also has a Patzke taper bearing conversion to complicate both matters. The Thornton had a 1/2" internal stop added to limit its travel so that it just cleared the crosspiece on full extension, though it could get quite close. This leads me to believe that the standard spring was the culprit during an earlier life. The original spring is constrained at both ends and should limit travel but could extend enough to do this I suppose if the unsprung weight was rapidly accelerated from full compression to full extension during a jump or from a hard dip in the road. Both the Thornton and this spring are close to level when I am in the saddle.
 
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Cyborg

Well Known and Active Website User
VOC Member
Go and look at many sets of Bramptons and see just how many hit the back of the rear down tubes on the stem cross piece.
Any one for a survey?
One for each column. The one with the dents is closely related to Oldhaven’s.
I just look at the dents the same way as the ones in the touring fenders.
 

oexing

Well Known and Active Website User
VOC Member
Just thinking, maybe a steel rope inside the spring could help to stop the girder from excessive extension ?

Vic
 

ossie

Well Known and Active Website User
VOC Member
my forks only have a very short travel and do get close up on the rear stand they also miss the limit stops side to side.
 

MSVH Y3

Well Known and Active Website User
VOC Member
My forks do not show any signs of contact on the fork tube or on the stops. I do have to be careful as to where the valve lifter is located so as to not whack the tank, I am heavy, usually travel one up fully loaded and have hit the occasional pothole and speed bump hard enough to jar my teeth.
 

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greg brillus

Well Known and Active Website User
VOC Member
Looking at your steering stops, the travel is too much, this is what Ken was asking about in his first post about the steering stem being too low to contact the stops on the head lug correctly. I think it is common problem perhaps an over look by the factory, as I have had the same issues with bikes I have done, including replacement forks assemblies in the last couple of years. leaving out the FF 36 washer (if one is present) can help out a little here. Of course it is possible on the aftermarket forks, this issue could be worse. On the new "A" twins built here the steering head bearings were taper rollers, and the stops had to be cut back quite a lot to get the correct travel lock to lock. It is a funny problem not unlike the early bikes whereby the front fuel tank lugs seem to be too close together........A common problem that cannot be isolated to just one or two bikes.....strange going's on.
 

ogrilp400

Well Known and Active Website User
VOC Member
Is that on side stand, with a rider on it or on rear stand. It looks way too extended either which way.
It is on the rear stand unladen. If I put it on the side stand then the for will go to full extension and the rear tube rest against the cross piece.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Greg points out an important note where he mentions FF36 washer. This washer was never fitted on the Bramptons (Series A & B) and looking in the Vincent parts book this washer and the felt seal is not listed or shown in the diagram MO30 either. I have checked my early B copy and later B/C copy and both agree. This is more relevant to the other Brampton discussion so I have posted it there as well.
 

genedn

Well Known and Active Website User
VOC Member
Looking again at the image there is something funny about the spring. I could be wrong it just seems long.
 

Dinny

Well Known and Active Website User
VOC Member
Simon is correct with the differences between the series A & B, the A has a shorter headstock and so the spring is shorter. Both my bikes with Brampton’s have the bottom link almost horizontal when sat off the stand.

I also agree there is something wrong with the spring and it looks too long. Both my A & B have no indications that the fork tubes have ever hit the bottom yoke and even with the weight off the front wheel the spring stops it even getting close.

Cheers
Mark
 

Dinny

Well Known and Active Website User
VOC Member
Forgot to add, neither have the large washer under the bottom yoke bearing and so niether have a felt seal and no problems with the steering stops.
 

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