An Unholy Union III: WP 4860 USD Forks on an Airhead

The offset on my KTM is even smaller.

Sorry, the springs are not marked, that's the (main) reason that I haven't ordered softer srings.

Just read about another ADVR getting custom wound 0.65 springs from this place:

http://www.sonicsprings.com/catalog/

I've seen off the shelf (non-custom) springs available from .36 all the way up to .70 for 4860s.

These measurements seem to be consistent for the dirt bike models. However I was missing data on the 950/990 models, but as luck would have it someone on their way south on a 990 adventure is crashing at my house for the next couple days. I measured his forks and got a very different measurement between clamping areas:

65mm upper clamp area
175mm gap
92mm lower clamp area

I used a crappy tape measure and judging by anton's avatar, his numbers for the clamping area lengths are probably better than mine, but the gap between the two is obviously MUCH bigger on the 990 I measured - not sure what year - so much so that they probably wouldn't work on an airhead. :eek1

Does anyone have a KTM dirtbike to pull some measurements off of? Could you measure the center to center of the diameter of the hexagonal brake rotor bolt pattern? I'd like to compare them to the pattern from a 990 adventure which uses dual 300mm floating rotors as stock. The 990 rotors use no lateral offset, so if the rotor bolt pattern is the same, I might be able to use a 990 rotor with dirt model forks.

EXC400, 2006, +-2mm:
Straight accross (center to center) 125mm
One hole to the next (center to center): 65mm

Thanks for that, but DAMN. Not the same as the 990 which is about 143mm. Back to the drawing board. Maybe if I start with a 690 enduro hub. Hmmm...

EDIT: OK, after a bit more checking it looks like the 950/990 adventure, the 950 super enduro, and the 690 enduro all use the larger 143mm rotor bolt pattern. While the 950/990 adventure use the larger 30mm, the super enduro and 690 enduro use the same 26mm axle as the RFS model. I might have to start with a 690 enduro or 950 superenduro front hub. I'll also need a different caliper holder if not an entirely different caliper.

Measurements ripped off of metalgear's website:


Measurements (mm)
Outside Diameter: 300
Inside Diameter: 124
Bolt Hole CTC Diameter: 143
Bolt Hole Qty: 6
Bolt Hole Size: 6.5
Thickness: 5.0
Minimum Thickness: 4.5
Offset: 0.0

Metalgear makes some nice rotors at pretty reasonable prices too:



$189AU

I just finished my bike, rode it yesterday. (88GS} Short story, new cnc offset trees using stock SM forks and radial mount brakes. Shortened KTM stem turned down to fit BMW stock bearings. I used both KTM calipers and the stock KTM brake lines. The brakes are great, not too much as on the SM. I used a 16 mm BMW master cylinder and all my stock switchgear and throttle work fine on the KTM fatbars that are mounted in the stock rubber isolators. The stock springs in the 06 USD seem to be about right for me at 190 pounds.

I'm not too good a posting pictures. I will share if one of you send me an email address.

I was inspired by all of these unholy reunion threads and had to take action. Thanks !

Check your PMs.

Here you go. That's one hell of a big offset in the triples. I guess that's necessary in this application as the SM forks are non-leading axle. Have you shortened the travel at all? If not, it looks like you could bottom out your front wheel in the fender.

That is quite the offset. I left the clamps pretty thick, they are strong enough to set a house on. I have done some real hard braking while testing the rig, no issue yet on tire to fender clearance. I made sure the axle location is real close to stock, the geometry seems to be spot on.

I bet. Those brakes look like they'd stop you like a brick wall.

Are you sure about this measurement? I had a manufacturer of aftermarket KTM hubs tell me that the front rotor bolt diameter on ALL KTMs 125+ is 143mm. He said that 125mm is the diameter of the rear rotor bolt pattern on a lot of the dirt models.

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Aaarggh, you are right, it is 143 mm. I have a lot of trashed parts and picked a rear one. Sorry.<o></o>
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Hey, no prob. That makes my life a lot easier.

Any updates from the other 5 guys who bought triples to fit 4860s?? I'd have mine slammed together by now, but I'm still waiting to get my frame back.

Busy ridin' sorry... But who knows, there may be a parcel waiting patiently at home...

I looked into this and have satisfied myself that although the 26mm axle is a hollow aluminum tube, it was designed for bikes as heavy as the 950 super enduro which are about 430 lbs. It's the same part number used on all of these bikes:

» KTM 125 SX 2011
» KTM 125 SX 2012
» KTM 125 SXS 2006
» KTM 125 SXS 2007
» KTM 125 SXS 2008
» KTM 144 SX 2008
» KTM 144 SX 2007
» KTM 150 SX 2010
» KTM 150 SX 2012
» KTM 150 SX 2009
» KTM 150 SX 2011
» KTM 150 XC 2010
» KTM 150 XC 2011
» KTM 150 XC 2012
» KTM 200 XC 2007
» KTM 200 XC 2009
» KTM 200 XC 2008
» KTM 200 XC-W 2009
» KTM 200 XC-W 2012
» KTM 200 XC-W 2011
» KTM 200 XC-W 2007
» KTM 200 XC-W 2010
» KTM 200 XC-W 2008
» KTM 250 SX 2010
» KTM 250 SX 2012
» KTM 250 SX 2011
» KTM 250 SX-F 2009
» KTM 250 SX-F 2010
» KTM 250 SX-F 2011
» KTM 250 SX-F 2012
» KTM 250 SXS-F 2008
» KTM 250 SXS-F 2006
» KTM 250 XC 2012
» KTM 250 XC 2007
» KTM 250 XC 2008
» KTM 250 XC 2010
» KTM 250 XC 2011
» KTM 250 XC 2009
» KTM 250 XC-F 2011
» KTM 250 XC-F 2009
» KTM 250 XC-F 2008
» KTM 250 XC-F 2012
» KTM 250 XC-F 2007
» KTM 250 XC-W 2011
» KTM 250 XC-W 2007
» KTM 250 XC-W 2012
» KTM 250 XC-W 2010
» KTM 250 XC-W 2009
» KTM 250 XC-W 2008
» KTM 250 XCF-W 2009
» KTM 250 XCF-W 2008
» KTM 250 XCF-W 2012
» KTM 250 XCF-W 2007
» KTM 300 XC 2009
» KTM 300 XC 2012
» KTM 300 XC 2011
» KTM 300 XC 2008
» KTM 300 XC 2007
» KTM 300 XC 2010
» KTM 300 XC-W 2007
» KTM 300 XC-W 2008
» KTM 300 XC-W 2011
» KTM 300 XC-W 2009
» KTM 300 XC-W 2010
» KTM 300 XC-W 2012
» KTM 350 EXC-F 2012
» KTM 350 SX-F 2011
» KTM 350 SX-F 2012
» KTM 350 XC-F 2012
» KTM 350 XC-F 2011
» KTM 350 XCF-W 2012
» KTM 400 XC-W 2009
» KTM 400 XC-W 2010
» KTM 400 XC-W 2007
» KTM 450 EXC 2007
» KTM 450 EXC 2011
» KTM 450 EXC 2009
» KTM 450 EXC 2010
» KTM 450 EXC-R 2008
» KTM 450 SX-F 2010
» KTM 450 SX-F 2011
» KTM 450 SX-F 2012
» KTM 450 SX-F 2009
» KTM 450 SXS-F 2008
» KTM 450 SXS-F 2007
» KTM 450 XC 2007
» KTM 450 XC-F 2008
» KTM 450 XC-F 2009
» KTM 450 XC-W 2009
» KTM 450 XC-W 2012
» KTM 450 XC-W 2007
» KTM 450 XCR-W 2008
» KTM 500 EXC 2012
» KTM 500 XC-W 2012
» KTM 505 XC-F 2008
» KTM 525 EXC 2007
» KTM 525 XC 2007
» KTM 525 XC-W 2007
» KTM 530 EXC 2010
» KTM 530 EXC 2011
» KTM 530 EXC 2009
» KTM 530 EXC-R 2008
» KTM 530 XC-W 2009
» KTM 530 XCR-W 2008
» KTM 540 SXS 2006
» KTM 690 Enduro 2008
» KTM Champion Edition (250 XCF-W) 2010
» KTM Champion Edition (450 XC-W) 2010
» KTM Champion Edition (530 EXC) 2010
» KTM Preseries (505 SX-F) 2007
» KTM R (690 Enduro) 2009
» KTM R (690 Enduro) 2010
» KTM R (690 Enduro) 2011
» KTM R (950 Super Enduro) 2007
» KTM R (950 Super Enduro) 2008
» KTM R (950 Super Enduro) 2009
» KTM Six Days (250 XCF-W) 2011
» KTM Six Days (450 XC-W) 2010
» KTM Six Days (450 XC-W) 2011
» KTM Six Days (530 XC-W) 2011
» KTM Six Days (530 XC-W) 2010

Your post is a little scary to me. I'm refering to the part about the larger gap between clamping areas on the 950/990 4860's.

I have the 4860's from a 950, and was planning on using them on my GSPD. I am going to take some measurements and post what I find, since this is the USD to Airhead problem solving thread (from post one.) I've been dragging my feet a little in getting started on this project as I find my GSPD in it's current state to be super fun. It will also be super fun to make it better, and your thread is getting me more motivated to do that.

So much about using the WP4860's from a 950/990 seems desirable for a GS swap to my thinking. Especially notable are the amount of travel, dual caliper mounts, and larger axle size, which I assume (blindly?) must be stronger. Although admitedly less important an item to consider for fork swap potential because it is so easily changed, even the initial spring rate and damping in the 950/990 forks should be at a good starting point, judging by the similar weight of the two bikes.

These are the reasons for my fear that the gap between the clamping areas on the fork could end up being a dealbreaker, well, those reasons and the fact that I already paid dearly for the forks. :eek1

I wonder if the machined clamping areas on the forks are especially reinforced or thicker to stand up to the clamping force of the triples, as opposed to the rest of the fork tubes. ?

I also wonder how big of a deal it would be if the lower triple clamp was clamping half on and half off of the machined clamping area on the fork. ?

OK... measuring time and homework to do... just measured gap at 175mm...
uh oh :huh