Good conversation!
Have you ever looked at a R100RS top clamp? It's a piece of sheet metal --
The forces on the top clamp are pretty much forward and aft movement, the bottom clamp handles all up and down forces.
And it flexes. people who ride "gummikews", German for rubber cow. People who liked to go fast typically added a pinched top triple. CC products and San Jose among others sold them. I have one on my 74 R90. Definite improvement.
I am struggling to see any advantage of a fully straight stanchion over a top taper, a taper is used in engineering to increase the grip between 2 parts, hence the difficulty in getting the engine sprocket off the crank and its use in the locating of crankpins on roller big ends.
The problem I see in this design is the taper bolt is not set up to properly tighten the tube top. It has an O-ring to seal the the tube. The fork twists fore and aft and sideways. A typical taper fit does not have an o-ring included. Crank pins have to be pressed in- That's a different scenario with the crank always turning in one direction and much tighter fit.
Set up properly, there is absolutely nothing wrong with the way a Norton handles. If there is a problem, fix what you've got, don't go searching for an answer to a non existent problem.
That's the same thing you hear from the BMW guys.
Yet there are problems with the Roadholders-topping and bottoming out for example. They are an old design
First introduced in 1946 and then modified in 1953, Roadholder fork construction stayed relatively constant until the end of Norton production in the mid-1970s.
Motorcycle classics, How to rebuild Norton forks. I understand the Lansdowne kit really upgrades the fork action.
The reason I ask the question is because I have modified three of my motorcycles with 35 mm forks and noticed a positive reduction of flex riding fast and in rougher conditions.
-BMW R90- CC Products triple clamp-has a taper that clamps from the side and top, fork brace also very common modification. I had upgraded the brakes and noticed significant twisting when applied hard especially in a corner. Significantly better after installation
-Triumph T140-I rebuilt the forks and rode around with it. Harsh jarring ride didn't feel that stable when cornering. I decided to put a set of Betor forks and triples on the front end. Cost me $50 for the set at a swap meet. Lightened the front end, stiffer side to side movement. With this setup I was able to install cartridge emulators and get a cushy yet firmer ride. Note, I like to ride the Triumph fast on rough curvy roads common around western NY.
-CZ400- I race vintage motocross. This too has taper top triple clamps. When I first got the bike I wasn't very impressed with the handling. Motocross is rough terrain, certainly more extreme than road riding. I machined and welded pinch points below the top taper creating a clamp similar to the BMW. What a difference!
Try this test- stand in front of you bike and grab the front wheel between your knees. Twist the handlebars from left to right. My stock bikes would typically deflect an inch either direction. Try that with a more modern bike -much less deflection.
