Triple clamp mismatch

cbertozz

cbertozz

Hero member
Location
Australia
So I?ve managed to get a top and bottom triple clamp for the Jota.

When I took off the top one and compared it to the new, I could see that the steering head stem hole sits further back than the ones that are currently fitted.

So here?s a few questions for you good folks...

1. Which one looks like an ?original?? I have an inkling the new ones might have been off an SF2.

2. Can I fit them?

3. I?d so what?s the impact of the
change e.g rake etc?

All help gratefully appreciated as usual.
 
Oops

IMG_2705.JPG

 
Ok, if both same hole size it looks like they are both Ceriani.
So, the top one is for a 1000 and the bottom is for an early 1200.
Bear in mind the 1000 yokes steering stem holes were not bored parallel to the holes for the stanchions, whereas those for the 1200 were.
So, independent of the offset I think they would not match your lower yoke.
 
If your bike was originally fitted with Ceriani forks, then I think that the top/new yoke is correct.    So, you'll need a corresponding bottom yoke to match the increased offset of the new part.
I recall that there was an earlier thread about your yokes.

You also need to be aware that the Ceriani yokes came in two versions.  The first was the so called offset version that was fitted to most factory triples.  This version had the steering stem offset by a couple of degrees, with the top yoke to match the increased offset.  The other version looked very similar, but did not have the offset stem, and the top yoke had less offset.  This version, the so called SFC yokes, resulted in less trail and slightly faster steering.

Be aware that if you fit an original pair, regardless of which version, you'll end up with different (ie more) trail and that this will result in different handling characteristics.  Fitting a set of 38mm Marzos is an alternative option and will give you trail figures closer to you current yokes. 

Tom   
 
The concept of 'more offset' can be confusing with these triple clamps. Basically, on the ones with 'more trail' the forks are steeper than the steering stem (ie they aren't parallel).

It's a weird concept that i never particularly liked. I think you're much better off going with a parallel setup. You can find Marzo clamps with varying amounts of offset (eg Ducatis) so i'd go for parallel clamps with the most offset (to decrease trail and quicken up your steering a tad). i think my Marzo 38s have 45mm of offset. Bought them from Gowanloch decades ago.
 
Grant said:
Ok, if both same hole size it looks like they are both Ceriani.
So, the top one is for a 1000 and the bottom is for an early 1200.
Bear in mind the 1000 yokes steering stem holes were not bored parallel to the holes for the stanchions, whereas those for the 1200 were.
Click to expand...

What was the (likely) thinking behind this difference, Grant? Was there an intended handling difference for the 1200s over the 1000s, and how would the handling differ from one setup to the other?
 
As PB2 said, it was their attempt to play with the steering angle.
Obviously not a roaring success as it was soon abandoned.
 
cbertozz said:
So you?re saying that even if I use the new top and bottom triple clamps that it won?t fit the frame.
Click to expand...

Provided you bought a top and bottom clamp as a set that belong together, they'll fit the frame. Which is pretty much what Tom said in his first paragraph. Put them on and see what happens. What could possibly go wrong?

The acid test is when you slide the forks in. If they slide nicely through the bottom and top yokes, it's good.

The clamps with the greater offset will give less trail and quicker steering than ones with less offset, at the expense of straight line stability. (I'm talking about the distance between the fork centreline and the steering head, not angular offset).

As for the angular offset, I'm with Quentin (PB2). Not a fan of the triple clamps that are bored at a different angle to the steering head. It creates a whole lot of headaches from an engineering point of view. For one thing, it means the trail dimension changes with fork compression. I reckon it must have been an afterthought by the factory to give the early 3Cs a bit more stability. Surely nobody would design it that way from the outset.
 
Ducati 750 GT Ceriani yokes were parallel with the big offset AKAIK.

So if whatever you got is parallel then you should be able to easily on-sell if not suitable handling.
 
helicopterjim said:
Ducati had the built in rotatable yoke that changed rake and trail ....... but not wheelbase. I really didn't understand until I owned one.
Click to expand...

The Ducati system for changing the steering rake was a bit of a mystery to me too when it first appeared, but it's actually pretty simple.

As I understand it, the steering headstock is a tube housed inside another tube that's fixed to the frame. The inner tube (not to be confused with the thing inside a tyre) has the steering bearings slightly offset to give a 0.5? angle between the steering stem and the tube. You loosen a few bolts and rotate this tube inside the outer tube (which is the bit welded to the frame) and it changes the steering angle. Obviously the offset has to be aligned with the centreline of the bike otherwise the steering would be angled off sideways. So there are only two positions (180? apart) that you can set it to, allowing a 1? change in rake angle (23.5? - 24.5?)

The difference between the two positions only changes the trail by about 6mm. Not a lot in the scheme of things, but if you're into fine tuning for racing, it might be useful. Ducati calls the long trail position strada (road) and the short trail position circuito (track).

The fact that the wheelbase remains the same had me scratching my head for a while, but it's all in the detail design of the offsets in the headstock tube.
 
I couldn't have said it better myself ........


Dellortoman said:
The Ducati system for changing the steering rake was a bit of a mystery to me too when it first appeared, but it's actually pretty simple.

As I understand it, the steering headstock is a tube housed inside another tube that's fixed to the frame. The inner tube (not to be confused with the thing inside a tyre) has the steering bearings slightly offset to give a 0.5? angle between the steering stem and the tube. You loosen a few bolts and rotate this tube inside the outer tube (which is the bit welded to the frame) and it changes the steering angle. Obviously the offset has to be aligned with the centreline of the bike otherwise the steering would be angled off sideways. So there are only two positions (180? apart) that you can set it to, allowing a 1? change in rake angle (23.5? - 24.5?)

The difference between the two positions only changes the trail by about 6mm. Not a lot in the scheme of things, but if you're into fine tuning for racing, it might be useful. Ducati calls the long trail position strada (road) and the short trail position circuito (track).

The fact that the wheelbase remains the same had me scratching my head for a while, but it's all in the detail design of the offsets in the headstock tube.
Click to expand...
 
Dellortoman said:
I reckon it must have been an afterthought by the factory to give the early 3Cs a bit more stability. Surely nobody would design it that way from the outset.
Click to expand...

Not so sure about that - SF2s came with the same design, probably the exact same triple clamps.
 
Possibly a cheap measure to increase high speed stability and gaining agility, without the need to alter the frame geometry.  More trail without increased wheelbase, something that would suit the twins just as much as the triples!

piet
 
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