Titanium Hub?

Hey everyone,

I have a question about the Ti hub. What is the weight difference between it and the regular KH hub (08)?

Also, how much stronger is it? Is it worth it to get it if your not breaking your normal hub?

I’m not sure about the exact weight difference, but I think around half a pound. The big difference isn’t the hub itself, it’s the titanium bolts.

It’s quite a bit stronger I believe.

That’s pretty much all I know about it. Well, then of course it looks amazing :slight_smile:


Saves about 180g-190g, dont know the exact amount sry.

I may be wrong, but i think i heard Kris saying that its as strong as the normal hub.
If you have the money and want a lightweight and strong uni, then get it!

Weightweenies FTW hahaha :smiley:

According to Unicycle.co.uk

Kris Holm Titanium ISIS Hub Weight: 425g. Weighs 200g less than the 2008 KH ISIS hub with CrMo axle.

Kris Holm ISIS Moment Hub 2008 Weighs (including bolts and spacers): 644g

Nimbus ISIS Hub Weighs: 600g (635g including bolts and spacers)

Onza ISIS Hub Weighs: 600g (635g including bolts and spacers)

Kris Holm/Onza splined 36-hole hub- 2005 model Hub Weight: 680g (with bearings & bolts)

Qu-Ax ISIS Hub (red) Weighs (including bolts, bearings and spacers): 815g

Suzue Unicycle cotterless hub Weight - 530 / 525g with bearings, spacers & nuts.

According to Unicycle.co.nz

KH Moment Titanium Hub Weighs a miniscule 426g including bolts, bearings and spacers!

KH Moment ISIS Hub Weight (including bolts and spacers): 644g

KH-Onza 36-hole hub- 2005 model Weight: 500 g (bare), 650 g (including bearings, bolts and spacers)

According to Unicycle.com (USA)

Kris Holm Titanium Hub Weight: 1 lb w/hub bolts & spacers (453g)

Nimbus ISIS Hub (36-Hole) Weighs: 1.4 lbs (including bolts and spacers) (635g)

Poznanter/Profile Hub Weight 2 pounds (907g)

It weighs less than a suzue (half a kilogram) and the old best hub weighs nearly 1kg. It would be nice to have but with a price like that not everyone can afford one.

For the record, titanium is weaker than steel, and unless there is something funny about the heat-treatment process on the hubs, the ti hub should be weaker than the steel hub (possibly by a significant difference). Also, strong welds in titanium are much harder to do than in steel (much less tolerant of contaminants), so the welded flanges have a much bigger risk of breaking at the welds than the steel hubs do. I believe Tony Melton already broke a hub in this fashion.

Tony too?
You might be talking about Joe Dyson.

Thank you. Was about to say something along these lines.

how is titanium weaker than steel?

everything i’ve ever heard says that titanium is far stronger than steel by weight/strength ratios
unless titanium is far less dense…but that makes no sense, i want to see some background to what you’re saying. show me where you are getting this from.

I wish I had my old text books handy with all the properties of common metals and alloys but I seem to remember carbon steel and titanium having similar strength but titanium weighing about 60% as much as the steels.

A google search could probably verify this.

If weight doesn’t matter Ti is stronger, but on bikes and unicycles, weight matters and Titanium is used to save weight.

Is impossible to say if it’s strong or not. Depends of the weld quality and design.

Ti is lighter cause it’s strong than ALUMINIUM and you can use really thin walls. But if the walls are to thin it may breaks, like any other materials brakes. Also Ti is really rigid and don’t flex!

The amount of misinformation in the cycling/RC anything/Motosports communities is ridiculous. Any thread like this is a fine example.

Titanium is NOT rigid. It has a significantly lower modulous of elasticity than steel ( http://en.wikipedia.org/wiki/Young's_modulus#Approximate_values ), making it far flexier. I seem to remember talking to Kris about this issue when discussing whether titanium muni frames are worth the trouble. Also, since the design of the steel and titanium hubs is essentially identical, we can compare strength and make reasonable predictions. But you are right to say good design work should account for material choice therein.

Skorbro, your post makes it sound like you’ve never picked up a big chunk of titanium while expecting it to be steel. It is a dramatic experience to notice how light it is. And my source for the density and strengths of materials is Machinery’s Handbook, 27th Edition. Go buy yourself a copy if you don’t believe me.

The density of titanium is, according to my copy of Machinery’s Handbook, 27th Edition, 0.163 lb/in^3, while steel is 0.25 lb/in^3. So titanium is about 35% less dense.

In a situation where strength is the ultimate issue, and the dimensions of the part are fixed (we can’t make bigger ISIS splines), what matters are the strength to volume ratios. 6Al-4V titanium, the alloy which I believe Kris uses in the hubs, has a (0.5% ?) yield strength ranging from 120-160 ksi, depending on heat treatment. While 4130/4140 steel, depending on heat treat, has a 0.2% yield strength of 100-155 ksi. 4130 steel can be made much harder than 6Al-4V titanium. So if the titanium hub is fabricated perfectly, it can be of comparable strength to the steel hub, but it is unlikely to ever exceed the steel hub’s strength. I am ignoring spline hardness, by the way, since I assume no rider is regularly changing cranks.

Now, factor in the issues with the difficulty of welding titanium, and quality control thereof, and the titanium hub’s strength is an issue. Hence the fact that a much smaller sample of riders has already broken a titanium hub, while I, at least, have never seen a broken steel hub. If the titanium hub were machined from solid (prohibitively expensive), I would have more faith in its durability.

You would not be wrong to argue that the softer titanium hub builds a stronger wheel by conforming to the spokes better, but I don’t think that’s where a hub will be failing.

I hope this clears things up. And the answer to the original question is, the titanium hub is ONLY worth getting if you aren’t breaking the steel hub. If you are, you should either switch to profile, or get a custom built hub/crankset with a larger splined interface.

P.S. Rowan, you are right. I did mean Joe Dyson.

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Sorry I read that around here! I must find the post, but If I’m not right, someone posted that the titanium weld is also harder cause the material is harder and if the weld is weak it will not absorve much impact as aluminium does. I must find it…

Anyway both, Ti and stell are rigind materials aren’t?

About ti welding theres a site that teach many ways to make Ti bike frames. I think I have it bookmarked and can try to find. The proposed some realy interesting welds for low surface situations that I tought maybe would fit a flat frame. Until now I’m only designing the seatpost :p… Soon I will have my prototype and also an American Rider will test it :smiley:

Sorry about my error! that makes things clear!


On the hub I think, cause in other situations it would change a lot I think!

steal quality

you´re talking a lot about titan - in deed what´s with the steal :thinking:
in my oppinion the steal of the hub (not the axle!) is not very high quality.
therefor its not so difficult to build a titan hub in higher strength / lower weight.


PS: my TI KH - hub is about 210 gr les than my old KH Hub

It’s a common misconception that Titanium is “stronger” than steel, but as mentioned above it depends on how it is measured.

Ti has a stronger strength to weight ratio than steel but a lower strength to volume ratio.

It is also 60% heavier (by volume) than aluminum and has elastic properties that work well in bike frames but are not advantageous for a uni frame.

It’s also a lot more expensive, obviously.

The lesson is that no material is perfect but some are better than others for certain applications, and the challenge is to use the best material for the right location.

On a uni, my opinion is that Ti offers only marginal advantage for a frame because the flex issue requires Ti tubing with sufficient rigidity that it is only marginally lighter at huge expense.

In the case of the hub, we are of course replacing CrMo so there is significant weight savings. Since the volume of an ISIS axle is constrained by geometry, a Ti axle is slightly weaker than a CrMo axle. But while flange strength has been an issue, broken ISIS axles on a uni hub are incredibly rare so functionally they can be considered similar. Consequently the weight savings makes Ti, in my opinion, a very good material for the hub.

The elastic properties of Ti make it good for the flanges and the Ti flanges are also thicker than the CrMo flanges. So far there has been only one broken Ti flange that I know of, and it appears to have been faulty welding subject to warranty.

So in summary the Ti Moment hub is functionally similar in strength to the CrMo hub but significantly lighter.


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There are a couple of other advantages of Ti you haven’t pointed out:
-It’s expensive :stuck_out_tongue: You don’t buy an expensive sportscar because it is slightly better at getting you from A to B. You buy it because not every Tom, Joe and Mary has one.
-It looks cool
-No need to paint it (saves more weight and scratches)

As for the hub, why aren’t there any aluminium hubs? Most good bike hubs I know are aluminium, and they’re pretty strong and light.

You cant compare bike to unis here. Bikes do not come close to the amount of torque and stress which is required from a unicycle hub.

Maybe, but I ride road and XC, not trials :stuck_out_tongue:

Every single ISIS hub available to me right now except for the KH Ti is too heavy and too strong for what I use it for.

If you did the Hub from Aluminium, from what material you plan to do the Cranks then ? Aluminium Cranks mounted on an Aluminium ISIS Hub could result in some trouble I think.
Did you think you will feel the difference from 100 gramm maybe on a 36" or 29" while riding ? Didn’t the tire itself influence it much more ?

I also see to many Bike parts (which are very light mostly) brake week by week in the Hall where we do training. I love to have a trusted feeling in my hub and parts while riding a vehicle (mono, bike, moto…)

Good point. ISIS was never intended for an aluminum axle.

Weight savings can come from using a bigger hole through the axle (M15 axle bolt instead of an M12 bolt), but I’ve never offered an M15 option because the market is very small, weight savings are not that noticeable in the overall scheme of things, and it is really hard to predict what people will do with a product once it’s sold. I’d rather have something a few grams heavier that is versatile for everything.

Making flanges and hub body from aluminum instead of CrMo doesn’t save much if any weight because the flanges and hub body use thicker material; however it could provide a better flange surface and angle for the spokes. I’m working on something in that regard but won’t have anything to release just yet.


Lol, unicycle elitism. You buy it because there are not enough Titanium hubs for everyone and you are one of the few with enough money. Very typical Ken!