FF: Forks Modified Steering Stem

bmetcalf

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I tried about six different super-duper glues and none of them kept the piece of radiator hose on for more than one try. I finally got around to having 1/4" thick steel pads welded to the feet of the stand. The report is that it works well now.

With the longer eyebolts, I find that my Hills centerstand leaves both tires touching the floor. I'll write to him to let him know. His request for measurements when ordering would account for that. I guess 1/4" thick wear pads welded on the feet would be enough, but that is easy enough to check.

Dave Hills sent me these thoughts in response to my question:

" You are of course not the first one who has altered the suspension on his bike and then found that the stand is too short. I have seen several ‘mods’ to the stand to achieve a slightly greater leg-length. One idea-probably the easiest one is to cut a section of hard rubber from either a tyre or an old rubber boot and use something like “Gorilla Glue” to stick this to the sole of the feet. A 3/16” thick piece of rubber is probably all you need. An added advantage to this ‘mod’ is that it gives the bike a lot more grip especially when parking on steel plates as encountered on cross channel ferries .But I guess that you are unlikely to do this living in USA but a frequent journey for us living on a little island.
Another idea is to drill and tap the feet up into the hollow leg and then screw in a extra large headed bolt. Quick and easy but not such a good idea if you park on wooden boards or ‘posh’ tiles.
Probably the best way to get a bit more leg length is to carefully cut off the ‘heel & toe’ of both feet, then round up the ‘stump then weld on a pair of new feet. Using ¼” plate this will give you about 7/16” more ‘lift’ at the back wheel. Do remember that by increasing the leg length by ¼” lifts the rear wheel by about 3/8” or more. A good way of calculating the exact amount of increase you need is to slide thin pieces of plywood under the legs before you start altering things. Using thin plywood you can get the ideal height that suits you and then measure the plywood to get the increase you need."
 

Gary Gittleson

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Finally, I have been able to give this setup a reasonable trial. It's as good as what others are saying. Besides the primary purpose of dramatically reducing the ever-looming threat that the original design presents, this mod improves the overall road-worthiness of the Girdraulic fork. Anyone who does now or plans to ride a Girdraulic-fitted Vincent rather than store it behind glass, should give this mod serious consideration.

The roads around here are pretty rough after a hard winter. There was plenty of opportunity to see how she'd handle the bumps. As others with this mod have observed, the freedom of movement of the forks is amazing. If I didn't have an LED headlight bulb, I'd be thinking about suspending the headlight for fear of breaking a filament. It was in constant motion, with hardly any of that transferred to the handlebars. I also noticed a considerable improvement in cornering. It tracks smoothly and predictably and drops into the turns much more freely. That latter point I assume is due to a reduction in trail. I believe that the stock setup has a lot of trail over much of the path of axle movement. It also has the unfortunate feature of varying the trail considerably depending on the degree of compression or extension. In an case, I always thought that the stock setup gives a battleship-like response to the initiation of a turn. No longer.

I will have to take the words of the experts in regards to the increase in safety. I have no desire to put this to the test. The other benefits alone make this job worth the work and expense, both of which are well within reason.

There are a few options that Norman offers with this kit. I chose to retain my Thornton shock, to include the ball-bearings for the lower link and the hydraulic steering damper. The latter item by the way, works very nicely and I have set it toward the stiff end without experiencing any low-speed wondering.

Norman mentioned earlier in this thread that I had cut the springs down by 1/2". To check the result of this, I placed a cable tie high up on the damper rod (a Thornton) before the ride. After the ride, rests about 1/4" from the rubber bump stop at the bottom. I am thinking of adding a 1/4" spacer atop each spring. I have some nylon washers of that exact size. So I do have two questions for Norman. Should I do this, and would that material be appropriate? If I do, maybe I should put a steel washer between the spring and the nylon to prevent the spring from mauling it.

P.S. Three cheers for John Emmanuel, Norman Walker and the several others who added much time and expertise to this project.
 

timetraveller

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Thanks to Gary for his kind comments. Regarding packing with a nylon washer; there are different grades of nylon so I cannot be sure that the one which Gary has access to will last. It would certainly do for a test and probably a steel washer between the nylon and the spring itself would help. This leads to an interesting matter regarding pre-load and spring rate. Gary removed half an inch from each spring which is the equivalent of removing one inch from one, i.e. 36 lbs of pre-load. The pre-load with the full length 36 lbs/inch springs is 216 lbs so a reduction of 36 lbs is 16%. Removing half of the one inch spring length reduction is going to reduce that to 8%. That kind of adjustability is why I designed the adjustable length inner spring box but, as above, I have still failed to find a supplier of the correct tube. I wanted to use stainless steel and at the GCM I asked Ian Savage who it is that supplies the Club Shop with these items. It turns out that it is Colin Taylor, who lives in Italy, probably uses metric tubing and who's name is not in the Confidential Admin List. I guess he is not a member. At the moment the best that I can come up with is to buy tube with the correct inner diameter, just over one inch, and then cylindrically grind the outer down to the correct size. I can find people to do that but there really ought to be an easier way.
Remember, it is only by this kind of feedback that the system can be improved so thanks to all who have provided feed back.
 

Dave61

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Thanks to Gary for his kind comments. Regarding packing with a nylon washer; there are different grades of nylon so I cannot be sure that the one which Gary has access to will last. It would certainly do for a test and probably a steel washer between the nylon and the spring itself would help. This leads to an interesting matter regarding pre-load and spring rate. Gary removed half an inch from each spring which is the equivalent of removing one inch from one, i.e. 36 lbs of pre-load. The pre-load with the full length 36 lbs/inch springs is 216 lbs so a reduction of 36 lbs is 16%. Removing half of the one inch spring length reduction is going to reduce that to 8%. That kind of adjustability is why I designed the adjustable length inner spring box but, as above, I have still failed to find a supplier of the correct tube. I wanted to use stainless steel and at the GCM I asked Ian Savage who it is that supplies the Club Shop with these items. It turns out that it is Colin Taylor, who lives in Italy, probably uses metric tubing and who's name is not in the Confidential Admin List. I guess he is not a member. At the moment the best that I can come up with is to buy tube with the correct inner diameter, just over one inch, and then cylindrically grind the outer down to the correct size. I can find people to do that but there really ought to be an easier way.
Remember, it is only by this kind of feedback that the system can be improved so thanks to all who have provided feed back.

Hi Norman,
I made new lower spring boxes using a couple of end fittings that Dave Hills kindly supplied me.
I had a real struggle to find Imperial size tube so ended up using thin walled metric tube that was very close to original size.
Cheers
Dave
 

vibrac

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Thanks to Gary for his kind comments. Regarding packing with a nylon washer; there are different grades of nylon so I cannot be sure that the one which Gary has access to will last. It would certainly do for a test and probably a steel washer between the nylon and the spring itself would help. This leads to an interesting matter regarding pre-load and spring rate. Gary removed half an inch from each spring which is the equivalent of removing one inch from one, i.e. 36 lbs of pre-load. The pre-load with the full length 36 lbs/inch springs is 216 lbs so a reduction of 36 lbs is 16%. Removing half of the one inch spring length reduction is going to reduce that to 8%. That kind of adjustability is why I designed the adjustable length inner spring box but, as above, I have still failed to find a supplier of the correct tube. I wanted to use stainless steel and at the GCM I asked Ian Savage who it is that supplies the Club Shop with these items. It turns out that it is Colin Taylor, who lives in Italy, probably uses metric tubing and who's name is not in the Confidential Admin List. I guess he is not a member. At the moment the best that I can come up with is to buy tube with the correct inner diameter, just over one inch, and then cylindrically grind the outer down to the correct size. I can find people to do that but there really ought to be an easier way.
Remember, it is only by this kind of feedback that the system can be improved so thanks to all who have provided feed back.
Nice to know in the feedback if its a twin or a comet (and perhaps the riders weight?) soon I hope to get back to sorting my comet from the ground up talking over the winter it would seem the first culprit of my rsultant solid conversion is the too stiff new AVO damper.
 

timetraveller

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Gary's bike is a twin and, from memory, his weight is about 180 lbs. He will correct that if it is wrong. On your (vibrac's) Comet I would try a short run over a bumpy road without a damper. If that works, and it should only take minutes, then we can sort out the damper.
 

Gary Gittleson

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Yes, it is a twin. It's a D Rapide. I probably weigh about 180 lbs fully geared up.
The nylon I mentioned seems quite hard. I'll give it a try. My homemade spring compressor makes the job quite easy, so I don't mind doing it a few times.

Gary
 

andrew peters

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A few months back I bought the complete kit, with bearings for the lower link and Norman’s steering damper.. I also put in new steering head balls and cups. It took a while to complete the work on my Rapide but I’ve been doing a lot of other things on the bike preparing the bike to be ridden a lot.. I have rebuilt both wheels with new bearings and fitted a pair of disc brakes on the front. (See thread on disc brakes on a C) I also reprofiled the front fender and made a new bracket and new support struts, this was partly in case the fender hit the exhaust and engine now the fork moved in a different arc but I never really liked the way the fender sat so high with the 19” wheel, the clearance under the fender made me think it looked like a dirt bike...
Back to the steering head mod.. originally Norman had suggested 45 lb springs and a heavy AVO damper but when I got the bike on wheels it was obvious to me that the fork was going to be too firm and uncomfortable, not Norman’s fault really, I had told him I would like the fork to be firm as I would be 2 up with luggage much of the time.. however, as we’ve read on this thread, much has changed in the way of opinions and experience.. as soon as I told Norman I found I may want softer springs and damper he had new parts winging their way to me.. Thank you Norman for that!
This is my resulting set up:
My weight 210lb wife 150lb (ish.. I guess?) saddle bags and rack for big bag.
36lb springs, no modifications at all
AVO damper, normal. minimum setting
Norman’s hydraulic steering damper set 7 clicks (I did find I needed to modify the arm to clearance the engine, but Norman now specifies this)
Ball bearing lower link
Ball race steering head
AVO coil over rear shock, a lot of preload (for this trip) and damping about half way
19” wheels on Roadriders
Powerful twin discs...
one other modification I found necessary, although probably peculiar to my bike, I had to fit slightly higher wider handlebars as the new fork action meant the top link could come into contact with my brake master cylinder.. I’m content with the new riding position although I really liked the Vincent flat narrow bar.
I had the bike ready just in time for my trip to The Quail in California, I took the bike around the block and packed on the luggage for the first ferry from Victoria in the morning.. Was I prepared for my first long trip on a freshly built bike? Was I sure I had the suspension set up satisfactory? Well time was up, I was as prepared as I could be.. I had gone through everything more than once, I had read and re read the forum threads etc.. I was satisfied and confident, at least l knew the bike was as good as I could get it..
2800 miles later I have to say a big thank you to Norman for his help, also to the many posters that chipped in with useful tips and advice, even if sometimes it was heavy, technical and maybe a little bit over thought out. (gulp)
So my experience with the steering head mod could be just luck, it worked for me right out of the box. I will pass on this tip though, careful assembly! Mainly the pivot bolts and lock pad bolts, over tightening will cause stiff action and although it’s obvious now I’m saving it if you just tighten everything up it doesn’t work properly, if it’s loose then your steering and suspension will feel ‘loose’
I know I still have some riding to do with less weight on the bike and maybe I’ll want to modify or adjust things.. so far though I’m very happy with the handling and comfort, easily as good as my BMW R90S that I’ve been riding for 40 years! The Vincent tracks straight and corners smoothly with no weaves or wobbles at all.. I’m sure the steering mod is essential with a more powerful brake although I admit I have no experience of a bad handling or poorly brakedVincent.. why would anyone put up with that? Haha
So thanks again Norman, of course John Emmanuel for the development, and you guys for your input and encouragement.. I will continue to try to improve my Vincent and I guarantee to keep riding the bloody thing..
 

andrew peters

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2800 mile test ride
 

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