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FF: Forks Modified Steering Stem

greg brillus

Well Known and Active Website User
VOC Member
Hi there to all interested in this subject, just wanted say that I have just installed this kit, along with the change from the large lower link eye bushes to sealed bearings, to a friends Comet. In fact it is the bike belonging to Neal Lowe who lives not far from me here on the Gold Coast, and has a write up about his two bikes in the latest MPH. So he has had a taste of the difference between the Girdraulics on his Comet verses the Brampton's on his "B" Rapide. Well the conversion process went very well, only hold up was getting the link eye's honed out to suit the 32 mm OD bearings, but that was not too difficult, and I soon had all 4 bearings pressed into the link and installed on the new stem, which we had fitted the day before. I ordered one of the new Kawasaki type steering dampers to be installed in the next few days. I had a small batch of attachment brackets made as per Norman Walker's design from 6 mm 6061 alloy, and these bolt straight on with two 6 mm Allan headed cap screws. Ok the final part was what springs to use, and I had already had some 40 Lb springs made at two different lengths, but these were too long, and even the short ones when installed in the front of my Rapide, was topping out and I could not press the suspension down at all...!!!! In the end on my bike I used a pair of David's springs of the red version which are 75 Lb's each. These work quite ok, and still probably a bit heavy still, but not unacceptable. Ok .....Back to the 40 Lb springs.......We decided to use these and chop them down in increments and see what happens, first we cut 25 mm off and tried this, but it felt too heavy, so we chopped another 25 mm again, and this felt quite good. The right side spring box felt very harsh, so I removed it and thoroughly washed it out to remove any grit and old grease, reassembled, and refitted the front wheel. We hooked up the front brake cables, adjusted the brakes and tightened the front axle. The front end felt very good, and dived with the front brake held firm. It was time to go for a ride......It fired up first kick, and I took off up my drive way, and off down the hill and around the block. The bike felt absolutely fabulous, the font end rising on acceleration as I changed up through the gears, followed the bumps and divets in the road with a nice soft ride, no harshness at all, back off the throttle and touch the front brake, and the front dives nicely....Not too much, but just as it should. I returned up my street where Neal was waiting for the news......I handed him my helmet and sent him off for a test ride. When he returned he could not believe the transformation, and he agreed as I did, that it actually felt better than the Brampton's on his "B" Rapide. All in all I felt very happy with the spring choice, though I will try some of the ones Norman has made up in the front of my Rapide, as mine still feels a bit stiff. The springs really take some experimentation to get right dependent on the rider and the bike itself. But by todays efforts, I can honestly say that Neal's Comet feels better than any other I have ridden, and I think from Neal's reaction that he would totally agree. Now he has plans to upgrade the rear suspension as well, and as we know these things can be a work in progress. But given this is the first Comet I have carried out this modification to, I can say with absolute confidence that it is most definitely worth the while. Big Thanks to all who contributed to this outcome, especially Norman and David. Cheers for now...............Greg.
 

timetraveller

Well Known and Active Website User
VOC Member
Hi Paul, John Emmanuel who developed the modified steering head had fitted taper roller head races but told me that he did not think it was necessary. I can get this done for you by a local engineer who borrowed three different steering heads from me in order to make the jigs to make this relatively easy. The steering head has to be removed from the oil tank which is actully easier than most people think. My own feelings on this are that if you have cup and cone bearings which are still in good condition then there is no need to do this. However, if the cup and cones are worn or their housings are loose or damaged then the best way to go is to convert to taper rollers. Apart from handling they have the big advantage of not having ball bearings being loose and falling out all over the floor the steering head has to be dismantled. The alternative,if you want to do it without getting the steering head machined there is the VOCSC taper roller conversion, which is based upon a German design and that requires no machining of the steering head.
Hope this helps
 

greg brillus

Well Known and Active Website User
VOC Member
Taper rollers are nice, but there is little advantage in using them unless the original races are loose like Norman suggests above.........With the original races it is most important that they sit firmly home in their pockets, flat and square........The lower one can be tricky to change in situ and can end up crooked in its pocket (this is the one in the steering head not the stem itself) A race that is crooked will make the bikes handling feel absolutely horrible.......It may be a symptom that is more common than not, and perhaps for this reason.
 

highbury731

Well Known and Active Website User
VOC Member
I have looked at the races for my bike. They appear unworn. If they pass inspection again, I will retain them - I just have to transfer the lower race to my shiny new steering stem... thanks Norman.
 

timetraveller

Well Known and Active Website User
VOC Member
Read the intructions carefully and get the race hot before putting it onto the new stem. The taper helps. If it goes sideways and you tap it it will fracture as they are very brittle. You can guess how I know!
 

davidd

Well Known and Active Website User
VOC Member
I loaned David Tompkins my taper roller stem for a season and then sold him a new stem (for stock bearings) which he machined for taper roller bearings. The reason I built some taper roller stems was that my bike had a problem with the lower race moving around. I solved this problem by replacing the lower bearing again and had no issues. Despite this, I made a drawing to have two taper roller stems made. David, on the other hand, had to adjust his steering head several times and found that the bearing broke. The replacement broke also. He used my taper roller stem and had zero problems.

The lower bearing gets pushed really hard on a road racer, so it is unlikely a design issue. I believe it has to do with the fit of the lower bearing race in the steering head, which is often compromised. I checked with Carleton Palmer and he never had a problem with his race bikes, so I think it is the luck of the draw.

The taper rollers do not affect the handling unless you are breaking lower races. I would not opt to do the conversion for fun, but I would normally install taper rollers on a racer that is being built to make it more reliable.

If you want taper roller bearings, get them from Norman while you can. It is best to have the new steering stem and taper rollers do require a machined stem, which the stock Vincent does not have (although they vary).

DSCN4394 01.jpg

The stock modified stem on the left and the taper roller on the right. The taper roller stem is machined to hold a bearing steady at the top and when seated at the bottom, like a modern fork stem. I also left the stock damper design on the stock modified stem on the left but removed it from the racing stem.

David
 

timetraveller

Well Known and Active Website User
VOC Member
I went to see the local engineer who can do the taper roller conversion this morning to check the latest price. Machining, supplying and fitting the bearings comes in at about £170 plus P&P. Compare this with a price of about £260 for a pair of cup and cone bearings and you can see at least one advantage. I also learnt that it is possible that there are two ali steering head lugs available, fitted with taper roller bearings. Someone has expressed interest in these so they might not be available but they are about £1,000 each complete with bearings, Both are of the type with the forked lower end which fits over the cylinder head bracket.
 

timetraveller

Well Known and Active Website User
VOC Member
OK. Chaps. I now have orders for 17 so have ordered 20 to be made. The reason for this note is that I am drawing up a spread sheet of all the parts I need and rather than contacting you all individually I thought it would save time to put a notice here. I need to know the following details from each of you before I can order the parts so here is a list of questions. Some of you have aleady provided the information and you will know who you are so you can ignore this. For the rest could I ask you to email me on enw07@btinternet.com with the answers to the questions.
1) Is the bike a twin or a single and what is your weight? I need this to specify the springs.
2) What do you intend to do about the lower link? I know some are waiting for new ones and I am told by VOCSC that a new batch will be available within a week or two. Those who have given me this information can relax. I think that you will all be using the Greg Brillus bearng mod, which I highly reccomend, so all I need to know is whether you just want the bearings.
3) Do you want a front AVO damper with the kit?
4) Do you want a hydraulic steering damper kit to go with the rest of the kit?
5) Do you want me to supply a rear AVO coil over with the rest of the kit?

Please note that the prices for all the items are in posting #1,208 above.
Thank you
 

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