1125R and XB front end interchangablility?

[Candyman]

Hello, just working on a front end swap on a project of mine. Just wondering if someone could shed light for me wether or not the top clamp on a set of 1125R forks would be the same as a top clamp on say an XB12R? I am thinking they are but have no way to confirm.

Any help in confirming this would be appreciated.
Thanks

 

[loose1]

No, the 1125 forks are spread farther apart than an xb.

 

[Candyman]

Excellent, just what I needed to know thanks[up]

 

[FQP19]

Looking at this myself too, this helped me!..
http://www.buellxb.com/Buell-XB-Forum/Buell-1125R/Firebolt-Conversion

 

[wolfo68]

The top triple from an 1125 will work on xb forks.

 

[jetlee]

The top triple from an 1125 will work on xb forks.

As previously stated, the 1125 forks are further apart. The forks may fit into the top triple just fine, but to properly use the top triple on an XB then you also need the 1125 lower triple, 1125 axle and spacers (not sure if the 1125 uses spacers or not, to account for the extra space between fork and hub).

Then there's the issue of caliper-to-disc spacing.

 

[EricZ]

There is no caliper to disc spacing issue. The wheel and caliper both locate off the right fork lower. The only issue is the fork to fork center distance difference of the 1125 vs XB triple clamps. I did the swap on my bike.

The 1125 and XB use the same front axle and bearing spacer, too.

DO NOT mix 1125 and XB triple clamps. Use only 1125 upper and lower clamps OR XB upper and lower clamps.

 

[jetlee]

If the 1125 puts the forks further apart and uses the same axle and bearing spacer, where is the difference in width made up?

Looking at the parts manuals, I can only conclude that the difference in width is made up by the lower fork itself. In which case, using XB forks in 1125 triple clamps without an additional spacer will result in triangulation of the forks.

-EDIT-
Or are you referring to the fork offset and not the fork spacing?
Offset being the distance from the center of the head bearing to the centerline of the forks.
Spacing being the width/distance between the forks themselves.

-EDIT-
If the issue is OFFSET, instead of spacing as the earlier posts suggest:
Of the information I have found, both bikes share the 21° rake. The XB's have 83mm of trail where the 1125 has 84mm of trail. This changes the fork offset from 30mm for the XB to 29mm for the 1125, if my math is correct.

While this would keep the forks parallel with each other, it would cause a change in rake (depending which upper and lower triple is used) and likely destroy head bearings quickly.

 

[jetlee]

What I'm trying to get at is if the issue is just offset then as long as you use both triples from the same model you are fine.

But if the issue is spacing (as posts #2 and #7 indicate), then there is more geometry that needs to be taken into consideration.

 

[Negative]

.............. This post blew my mind quicker than a high dollar hooker ...

 

[jetlee]

I'm surprised this thread hasn't garnered more responses.

I brought up legitimate concerns and the discussion died.

 

[EricZ]

The 1125 right fork has a slightly wider leg where the wheel tightens against. See my post here: http://www.badweatherbikers.com/buell/messages/32777/733170.html?1394492940

 

[jetlee]

Thank you for the link.

So putting XB forks in 1125 triples without a spacer at the wheel is pinching the fork lowers 1.1mm tighter at the axle than if they were in their own triples. Conversely, 1125 forks in XB triples would be 1.1mm wider at the axle than if they were in their own triples.


If you're ok with that...



...I'm not, I'd get a spacer (or mill the fork, depending on which combination).

 

[EricZ]

I don't think you get it, jetlee..... There is no pinching that can happen. The axle floats in the left fork leg. The only issue, which is not an issue at all, is that the wheel will sit ~0.045" off of the bike's centerline if you use 1125 forks in xb triples. The only real problem is if you try to use a mixed set of 1125/XB triple clamps.

 

[wolfo68]

Just going to throw this out there.
My 1125cr top triple is 142mm across from the inside edge of each fork hole, so is the 1125R lower triple, and my XB12R lower triple.
Didn't measure the top for the 12R or 12S since the lower measured the same.

 

[EricZ]

I recommend you measure again, wolfo....It's impossible for the upper and lower triple holes to have the same distance from inside to inside for the 1125 since the upper triple holes are 54mm diameter and the lower triple holes are 56mm diameter. Your measurements would mean the 1125 triples don't hold the forks parallel.

 

[jetlee]

I work in ten thousandths of an inch tolerances every day. In my day to day, 1mm (.045") can quite literally mean death; hell it damn near cost one lady her arm (she lost about 24sq in of skin and broke two bones) a couple months ago because someone didn't build the machine to spec.

So I do "get it".

Like I said:

If you're ok with that...

...I'm not, I'd get a spacer (or mill the fork, depending on which combination).

You might be ok with it, or the next guy, or the next guy...I'm not. In other words, agree to disagree.

 

[truckinduc]

^^^^^^ actually 1mm = .03937"

I'm building a new xb triple so I've taken all my own measurements.

Xb fork center to center seems to be 195mm and offset looks to be 26.5mm