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Old 07-12-2013, 02:40 AM   #1
ontic OP
Joined: Jul 2008
Location: Melbourne
Oddometer: 1,070
Eh? KTM front wheel hubs- help please

I am trying to build a 19" front wheel and am trying to figure out what hub I have.

This front wheel will be for a WP50mm extreme (WP5060) front end (on a bmw airhead).

I have a 21" wheel that came with my front end, it has a 17mm axle.

I bought a bare ktm hub that was sold as being for a 17mm axle for a bike of the same vintage (that the forks came from), but today when changing the bearings in the 21" wheel and comparing the hubs side by side there are some important differences.

To go with these descriptions below there will be photos.

The 21" hub takes two different sized bearings- a 35mm OD 10mm deep bearing on the rotor side and a 40mm OD 12mm deep bearing on the other side. On the rotor side once the bearing is in there is space for a 35mm OD oil seal in the same bore. On the other side once the bearing is in there is a larger bore for a 52mm oil seal.

The bare hub I have takes two 35mm OD bearings the same size, and at 10mm deep there is no room for oil seals on top. The bearings are also further apart so will require a longer spacer between them. The spoke holes on this hub (from one side to the other) are also a little bit further apart/wider (approx 4mm).

some photos,
the old hub on the 21" wheel
rotor side

other side

the new bare hub I have.
Rotor side

other side


1. With this bearing set-up does anyone know what bike/year/range this hub would be from?

2. Is the 35mm OD 10mm deep bearing the right one for this hub? If so, is this hub meant to have a oil/hub/shaft seal on top? How?

3. Depending on what hub this is, what year etc, can anyone tell me if this is a Japanese or European spoke pattern? (my 21" wheel is Japanese). (I don't know how to tell with a bare hub what pattern it is).

I have a Jap pattern 36H Excel 19X1.85 rim ready to go and am trying to figure out what spokes to use to try to lace these together. Not sure if an off the shelf set of spokes will work or if I need to get some custom spokes.

Today, pulling out the bearings on the old wheel to check out the internal spacer, I was in a friends machine shop ready to start machining the internal and external spacers... then with the bearings out we figured out the hubs are different.

Machining up spacers will be no problem. Figuring out a way to get seals on as well was looking a lot more complicated. My bearing guy told me I could run these double sealed Nachi bearings I've bought without a seal/cover, as they are already very well sealed, and if required just replace them sooner....? This 19" wheel will be for a set of road oriented dual purpose tyres, for general road riding and commuting and touring... dirt riding and dirt oriented touring will be done on the knobby 21" set of wheels.

If there are any other measurements or photos or anything else required, let me know, I am trying not to make this post too long

1974 R90/6
1981 R80G/S
1994 XLR250R
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