Prolink Fork In Early Model Frame & Steering Damper

rbarber · Post by **rbarber** » Wed Oct 31, 2007 11:24 am

alimey4u2 wrote:HD V Rod too......

Is this a tongue-in-cheek remark

I thought the V-Rod forks were 49mm

Actually some of the larger ones out there...

alimey4u2 · Post by **alimey4u2** » Wed Oct 31, 2007 12:10 pm

rbarber wrote:
alimey4u2 wrote:HD V Rod too......
Is this a tongue-in-cheek remark I thought the V-Rod forks were 49mm Actually some of the larger ones out there...

Got a little muddled, knew it was one of them...

http://www.jpcycles.com/productgroup.as ... D047A0427D

Chris · Post by **Chris** » Wed Oct 31, 2007 1:43 pm

The triple trees from JPCyles must provide a HUGE benefit for $760.

alimey4u2 · Post by **alimey4u2** » Wed Oct 31, 2007 1:52 pm

Chris wrote:The triple trees from JPCyles must provide a HUGE benefit for $760.

But Chris, you don't have to pay anything for 90 days...

Chris · Post by **Chris** » Wed Oct 31, 2007 8:59 pm

alimey4u2 wrote:
Chris wrote:The triple trees from JPCyles must provide a HUGE benefit for $760.
But Chris, you don't have to pay anything for 90 days...

That was the first thing I saw, 90 days free. Led me to wonder.............

how the heck much do they cost when the seller needs to quote financing options?

Chris · Post by **Chris** » Thu Nov 01, 2007 11:31 pm

EMS wrote:Let me say so much, though:
I have done Prolink-fork-into-early-CBXes - conversions before. It is an easy plug-in, provided you have the Prolink triple tree. Therein, however, lies the dilemma. Honda changed the rake form 27.5 to 29.5 degrees with the Prolink models. That means, all other things being the same, the trail would increase. Now in order to keep the same trail of 120mm, Honda also changed the "offset" of the 39mm fork bridges and brought the front wheel contact patch forward and closer to the imaginary intersection between the steering axis and the road surface. This means, when a Prolink fork is being installed in an early frame, the trail will be reduced significantly. Resulting in all advantages and disadvantages of that.
The way I rode and ride my CBXes, I found it very difficult to get used to. Actually borderline dangerous in situations. I changed back. I believe the 39mm CB1100F front end is a better choice for the early CBX.

Mike,

If I understand correctly.....................

the rake change from an early model to a late model (27.5 to 29.5) was done in the triple trees?

That would mean that the steering neck angle from early to late model is the same?

If so, I should be able to change to 1100F triple trees and return the rake to somewhere nearer the early model's spec on the '81 framed race bike?

daves79x · Post by **daves79x** » Fri Nov 02, 2007 6:21 am

Chris:
That was my thought. I think the frame has the different angle. There is no difference that I can tell in the triple tree except one is 35mm and the other is 39mm. Someone would have to do a laser frame check to verify this. One degree difference is hard to measure.

Anyway, I've done the conversion as have many others without ill effect. Several others have converted 900F and 1100F front ends to the early CBXs as well with good results.

By the way, wouldn't stretching the rake (if that's what we're talking about) lead to a MORE stable bike at speed? It may just not turn as well. Most of us that do the conversions use an 18" front wheel that would offset that problem somewhat anyway.

Maybe Mike can elaborate on something I'm missing here, but the end result is that everyone I know that has done the conversion is at least satisfied with it. More opinions welcome!

Dave

EMS · Post by **EMS** » Fri Nov 02, 2007 7:32 am

According to "the books", the rake changed from 27.5 to 29.5. That was done with the steering neck.
This would result in a larger trail.
To compensate for this, they moved the fork legs forward by increasing the offset in the triple tree, thus decreasing the trail back to 120mm.
Offset is the distance between the imaginary line drawn through both clamping hole centers and the steering neck center.

A larger trail will result in a more stable straight line behavior, but if you put the triple trees with a larger offset in the early frame, you reduce the trail.

Chris · Post by **Chris** » Fri Nov 02, 2007 2:34 pm

EMS wrote:According to "the books", the rake changed from 27.5 to 29.5. That was done with the steering neck.
This would result in a larger trail.
To compensate for this, they moved the fork legs forward by increasing the offset in the triple tree, thus decreasing the trail back to 120mm.
Offset is the distance between the imaginary line drawn through both clamping hole centers and the steering neck center.

A larger trail will result in a more stable straight line behavior, but if you put the triple trees with a larger offset in the early frame, you reduce the trail.

Thanks Mike, your info is very helpful. :)

alimey4u2 · Post by **alimey4u2** » Fri Nov 02, 2007 7:32 pm

Chris wrote:Thanks Mike, your info is very helpful. :)

Yeah but his color choice of sweaters is all wrong, He's an Autumn not a Summer....

Great stuff guys, many thanks to all... Pick my forks up tomorrow & have the vernier ( dial to you youngsters..

) calipers ready....

cbx4evr · Post by **cbx4evr** » Mon Nov 05, 2007 6:33 pm

Interesting article on the subject.

http://www.carbibles.com/suspension_bible_bikes.html

alimey4u2 · Post by **alimey4u2** » Tue Nov 06, 2007 4:43 am

Good stuff, thanks Nick.....

alimey4u2 · Post by **alimey4u2** » Wed Nov 07, 2007 8:33 am

OK, Here's the skinny ( no pun intended....

)

My "A" model 1980 CBX has an offset (thank you Nick) of 46mm.

My "B,C" Prolink "Euro" model forks has an offset of 46mm.

This is measuring from the centerline of the headstock to the centerline of the forks. Haven't measured fork lengths yet as I have to take the load off the ones I have fitted.....

EMS · Post by **EMS** » Wed Nov 07, 2007 9:22 am

alimey4u2 wrote:OK, Here's the skinny ( no pun intended.... )

My "A" model 1980 CBX has an offset (thank you Nick) of 46mm.

My "B,C" Prolink "Euro" model forks has an offset of 46mm.

This is measuring from the centerline of the headstock to the centerline of the forks. Haven't measured fork lengths yet as I have to take the load off the ones I have fitted.....

Interesting. I have several different triple trees lying around and will put an early and a Prolink upper bridge on top of each other to see the difference. If Honda did not change the offset, and the fork lengths are the same, how did they manage to keep the same trail of 120mm?
One thing also, the change in the rake is NOT documented in the service or owner manuals. It is shown the same, both for early and Prolink CBXes as 27.5Â°. (or 62'30", depending on how they defined it.)

Chris · Post by **Chris** » Wed Nov 07, 2007 9:27 am

EMS wrote:Interesting. I have several different triple trees lying around and will put an early and a Prolink upper bridge on top of each other to see the difference.

I did this in my shop Mike and could find no difference other than the size of the holes for the fork tubes.