650 SS vs Early Commando Triple Trees

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Oct 28, 2009
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I am about to look through my stash of Norton bits to find a set of triple trees for a friend's 650 SS.
I think I have a mix or featherbed and early Commando triple trees.
Are they interchangeable, and if not how do I identify the differences?
 
Thanks elefantrider. Does that mean if I have a matched pair, top and bottom, an Atlas and early Commando set is interchangeable?
 
Top tree have different threads for the handlebars mount , BSF for the domie/atlas , UNF for the Cdo , bottom tree as said 26tpi vs 28 tpi , plus you could have different steering lock stop .....
 
The yoke offsets are important because too much offset reduces the trail. It causes the bike to understeer, and can cause a mishandle - the bike can stand-up under brakes and suddenly turn in the wrong direction. The trail on the steering is a combination of rake, wheel size and yoke offset. I think a Commando would have about 26 degree rake, and would use yokes with less offset than those from a featherbed. The worst yokes would be those from a Garden Gate Norton. They have a lot of offset. For a bike which is going to be ridden fast - nearly 100mm of trail with 26 degree rake and 18 inch wheels is good - but not on a two-stroke with a peaky power-band. I think the rake on a featherbed is usually 24.5 degrees, with 19 inch wheels. With 18 inch wheels, they are useless. Less trail makes the bike tend to understeer - with more trail it is possible to gas the bike harder and earlier in corners. The weight distribution then becomes more important - it needs to be well forward.
 
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When you change the trail on a motorcycle, you need to be very careful the first time you ride it after the change. If it tends to stand up very noticeably as you brake, you probably have a problem which might bite you.
 
A related question:
Since the yokes come in different widths (7" or 7 3/8") I assume the hub and brake plate need to match.
Where does the additional thickness occur at the wheel/brake end of things?
Can you mix and match? As in have wide triple trees, and narrow hub? Or vice versa?
 
I have a set of fork yokes which look as though they came off a featherbed Norton. If they were fitted to a featherbed Norton, they would probably crash the rider almost immediately. Think about what you are playing with. If you get it wrong, you might suddenly crash at high speed, when you brake. I never worry about crashing a motorcycle, but if I change the steering, I am always looking for signs that the bike might mishandle. When it happened to me, I had already raced the bike several times. A GT 750 Suzuki has it inbuilt - they can step-out while going in a straight line, even without braking.
 


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