Swapped triple trees?

[Orange4]

Hi

I noticed that the triples are different between my '78 and '79

Are these stock or were they swapped and if they were swapped what are they? Both sets of forks are bottom mount axle.

On my '78



On my '79

[bikerphil]

It is hard to tell them apart from the upper trees, at least for me anyway. The lower trees are easily identifiable. The lower tree with the tube pinch bolts facing forward are for the Standard fork which is the type that sits atop the axle. The Special lower tree for the forks with the leading axle has it's tube pinch bolts facing to the side. HTH

[Orange4]

Thanks. Mystery solved.

The '79F has a special triple tree with standard forks:



Now the next question is how will this affect the handling since the bike still has the standard forks. Should I get the standard tree back on there?

[Prisoner6]

The '79F has a special triple tree with standard forks:

Now the next question is how will this affect the handling since the bike still has the standard forks. Should I get the standard tree back on there?

Hi, Orange -

It will affect the steering geometry ... someone CMIIW, but my understanding of this situation is:

Special triple trees with Standard forks will cause the fork tubes to be moved back, which will increase the trail, thus causing the steering to be heavier.

[Orange4]

Hmmm

You have made me think about this. Another way of explaining my case is the special forks would move the wheel forward in relation to the rake angle, reducing trail compared with using standard forks.

So my set up has more trail than a stock special and the most trail possible with stock parts all else equal.

Then there is the fork offset which is greater on standard trees. Greater fork offset reduces trail right?

So Standard trees with standard forks has less trail than special trees with standard forks

And standard trees with special forks would give the least trail.

The last question is the offset of the different trees.

Simplest way to put this:

Most trail: Special trees with standard forks

Standard trail: Stock

Least trail: Standard trees with special forks

Am I on the right path here?

[Prisoner6]

So my set up has more trail than a stock special and the most trail possible with stock parts all else equal.

So Standard trees with standard forks has less trail than special trees with standard forks

And standard trees with special forks would give the least trail.

The last question is the offset of the different trees.

Simplest way to put this:

Most trail: Special trees with standard forks

Standard trail: Stock

Least trail: Standard trees with special forks

Am I on the right path here?

First: Yes, Special TT's with Standard forks increases trail compared to a stock Special.

Second: Yes, Standard TT's with Standard forks = less trail than Special TT's with Standard forks.

Third: Yes, all else being equal, Standard TT's with Special forks = the least trail.

Fourth: Sounds like you're on the right track ... I'm sure you know this already, but stock Specials and stock Standards have identical rake/trail specs.

So when you start swapping them around, it affects the steering geometry.

Less trail = Lighter steering
More trail = Heavier steering

At least with your set-up (Special TT's with Standard forks), you'll get the benefit of increased upper body strength!!

Hope that helps ...

[MPittma100]

Forks

You should definitely keep the forks and triple trees matched and not mixed.

[Orange4]

Thanks for walking me through that.

[Prisoner6]

You're welcome, O ...

FWIW, I agree with Mike that the best option is not to swap TT's and forks around between Standards and Specials.

But that's just my opinion ...

[Orange4]

PO did the swap. Now that I know, I'll be going back to stock. He had a fork mounted fairing on it so maybe he wanted more stability at speed. Just a guess.

Now I can look for a stock unit or maybe I'll take the opportunity to do an XJ fork swap since its on the project bike.

[Prisoner6]

PO did the swap. Now that I know, I'll be going back to stock.

I think that's a good idea, Orange. I was chewing on this issue a little bit more, and wanted to add a short P.S.

Yamaha must have chosen to set up our bikes with the rake/trail numbers they did for a reason.

They were probably trying to strike the best compromise between styling, handling, stability, ease of steering, etc.

Swapping the components around could create some awkward handling moments, or more seriously, a potentially dangerous situation. JAT

I know some have done it and been OK (I think Fred did it to lighten the steering for his sidecar rig), but I can't imagine ever doing it myself.