Front hub mod

[Mark911]

I got tired of buying KTM front wheels when using KTM triple clamps so I counterbored 3mm off the rotor ears. Now it'll work with both triples (using 3mm spacers with the Alta clamps). There's still plenty of thread engagement.

 

[Fod]

Hey Mark!
How come you didn't machine the hub so it supports the rotor? Take some of the shear off the bolts and also aid it the less thread engagement.

 

[Jon]

Hey Mark!
How come you didn't machine the hub so it supports the rotor? Take some of the shear off the bolts and also aid it the less thread engagement.

Machining precisely enough to contact the rotor is really hard. Plus, when you replace the rotor the new one will be slightly different (within it's tolerance range) and would not fit with your original cuts.

Mark did it right.

 

[Mark911]

I guess I didn't state it clearly. Yes, I machined the HUB, not the rotor. The counterbores you are probably seeing are for the rotor screws, that's the way this rotor comes. Look at the HUB and you'll see where I cut the hub (which is a flush surface stock).

I used a counterbore, V block, bushing plate, home made counterbore guide (a modified 6mm screw), the axle, some axle spacers, and two clamps for my setup. Kept things orthogonal, centered, and controlled my depth of cut. After I was done I had one location that needed a .003 shim and runout was less than .007. I could have turned it on my lathe but I was too lazy to de-lace/re-lace the wheel!

 

[Fod]

Did you do the machining on a mill? If so I think I would have just taken down the whole hub to that depth....counting grams on the electric bike!

 

[Mark911]

Nope, just the items listed. Essentially a fixtured free-hand! I should have taken a picture.

 

[Rainmaker]

Enlighten us (pardon the pun) about why KTM triples are good options? Are you playing with different offset or what?

 

[TCMB371]

Enlighten us (pardon the pun) about why KTM triples are good options? Are you playing with different offset or what?

He's playing with 52mm Cone Valves

 

[Mark911]

There are some among us that feel the stock Alta triple clamps are soft (material wise) and lack tight tolerance machining. When making adjustment to your tube height, is it easy to move the tubes? When you fall, even a small plop-over, does your front wheel get all wacked out of alignment? When you straighten the front wheel do the tubes squeak? Do the clamp gaps keep getting smaller every time you torque the pinch bolts?

 

[OneLapper]

There are some among us that feel the stock Alta triple clamps are soft (material wise) and lack tight tolerance machining. When making adjustment to your tube height, is it easy to move the tubes? When you fall, even a small plop-over, does your front wheel get all wacked out of alignment? When you straighten the front wheel do the tubes squeak? Do the clamp gaps keep getting smaller every time you torque the pinch bolts?

eeerrrr..... ummm.. Yes, yes, yes, ah yeah, and yes I noticed that... crap

 

[snydes]

I’ll keep tabs on the gap. The clamps on my MXR were definitely not easy to move the fork tubes in, in fact they were more difficult then they should have been to move the tubes in. Maybe there was a manufacturing change in 18.

 

[Silent But Dirty]

There are some among us that feel the stock Alta triple clamps are soft (material wise) and lack tight tolerance machining. When making adjustment to your tube height, is it easy to move the tubes? When you fall, even a small plop-over, does your front wheel get all wacked out of alignment? When you straighten the front wheel do the tubes squeak? Do the clamp gaps keep getting smaller every time you torque the pinch bolts?

Soft, you say?

 

[Philip]

Perhaps those who do not want KTM fenders or wheels could upgrade their triple clams to MXR/EXR clamps.

 

[Trialsman]

I noticed on my '17 MX the clamps had a part number inscribed with the alloy 6061. On the '19 EXR was the same number except for the last digit and the alloy was 7075 ( about 30% more tensile strength). Alta apparently made a lot of changes in the bikes if only the material they used. Mine also came with an o-ring Regina chain.

 

[snydes]

Well, my 18 MXR has the 6061 clamps, so apparently the change didn’t happen till later.

 

[revoltlution]

Soft, you say?

Oh dear lord... How are they both opened up? *How did you get the zipper above the balls?

 

[Redwolf]

Oh dear lord... How are they both opened up? *How did you get the zipper above the balls?

I just snorted whiskey through my nose!

 

[Duncan]

On the subject of fitting KTM wheels on the Alta I just put the wheels from my '19 350 EXC ICE bike on my Alta EX as follows:

Rear: bolts on as-is, no mods required.

Front: I used the Alta spacers and I placed 7mm washer shims between the caliper and its bracket and I used bolts about 7mm longer to mount the caliper.

I used a combination of stainless and steel washers to get close to 7mm.

Regarding the front wheel it is interesting to note the following:

1) The bearings are spaced same KTM v Alta, about 97.5mm outside to outside of bearings.

2) Due to different triple clamps the Alta fork is spaced 14mm wider than the KTM, thus the wheel spacers are 7mm thicker each on the Alta

3) The rotor is about 7mm further inboard (towards centerline) on the KTM v Alta wheel, otherwise the wheels are the same, thus I had to insert the 7mm spacers behind the caliper.

Mark911: nice machining job on your Alta wheel above. You took 3mm off the hub thus moving your rotor 3mm inboard. Same as putting 3mm shims behind the caliper. But I am confused because I measured and came up with 7mm needed, not 3mm. (7mm is coincidentally the difference in KTM spacer thickness v Alta spacer thickness, but not related). If I did 3mm instead of 7mm my rotor would be rubbing the caliper. Any explanation?

Philip came up with 7mm also in the "Rim Shattered" thread. Philip, how did you get 7mm? And please let me know how to rotate my 3 photos 90 degrees clockwise like you did for me last time!

In any event, for those wishing to use KTM wheels on their Alta, I believe the summary in bold above works, unless I am missing something...

 

[Philip]

Philip came up with 7mm also in the "Rim Shattered" thread. Philip, how did you get 7mm?

Alta sources, measurements, experiments with KYB SSS forks, common sense, a confirmation from ex-Alta guys.

And please let me know how to rotate my 3 photos 90 degrees clockwise like you did for me last time!

I have an add-on that I use every time I see a rotated picture. @snydes can use it too. I'd release it for common use, but using it incorrectly would cause more trouble than it solves. I may release it eventually with more disclaimers and a mandatory training. In the meantime just ask me in case you need something rotated. And hit Ctrl-F5 to do a hard refresh, or clear your mobile cache to see the changes. See... I told you it's complicated.