Is there another crank standard that would be better than ISIS?

So here’s my gripe:

The ISIS standard has been mostly forgotten by the mountain bike and trials/BMX world, so unicycling is uniquely united under this standard, but it may be that ISIS was abandoned for good reason.

Consider the problems we have with crank creep. Though it’s less of a problem with steel cranks, most of us are using aluminum cranks, so in time the cranks slip further and further onto the splines until they can no longer be tightened and are trash. This is a real problem for the new crank mounted discs brake systems.

So what ever happened to uni cranks/hub interfaces that had a fixed position, ie one where the crank has a hard stop and is tightened onto the splines by a clamping sytem incorporated into the cranks? This appears to be the norm in high end mountain bikes and jump bikes, and from what I can tell these cranks are plenty strong.

Here’s an example of what I’m talking about:

Notice these cranks are splined, but the removeable crank arm has two bolts in opposition that draw the crank tight against the splines.

And yeah, as to my gripe, I have some 150 moments that are on ther verge of being trash, also a couple other cranks that are ready for recycling, all because the aluminum gets worn from repeatedly being tightened onto the cranks without any way to maintain the crank spline I.D.

So, can the ISIS standard be combined with the bolt tightened crank design, then place a “hard stop spacer” that would sit at the spline “ramp” between the cranks and bearing?

ISIS is a public standard. So any manufacturer can use it. Once ISIS was popular for bikes, there were plenty of low-cost manufacturers producing ISIS crap parts. Customers who suffered from combining crap cranks with high-end bottom brackets for instance, for sure blamed the bike manufacturer for that, not the crank manufacturer. So most of the high-end parts producers abandoned ISIS and setup their own proprietary spline systems that are protected from low-cost manufacturers. In addition they benefit from the forced customer loyalty, as those systems are only compatible with their parts.
So the punch line is, ISIS itself is not bad (which does not mean there can’t be even better standards). It only turned out that too many crap stuff was available in the market. That is not (yet) the case with unicycle parts.
Additionally, unicycle parts are way cheaper than respective bike parts. If you compare KH moment cranks with the bike crankset you posted, you can get a couple of spare cranks before you hit the monetary break even point.

ISIS was abandoned by trials? There are some other options now but ISIS is still by far the most common design on trials bikes.

Anyway, back to the issue.

ISIS was less then ideal for bikes because it was implimented with a larger diameter axle inside the standard bottom bracket shell, and therefore required smaller, less durable bearings. This isn’t an issue with unicycles. Many of the new bicycle cranksets use external bearing cups that allow for larger bearings. These designs tend to use removable axles. Since the axle has to be held in the bearings by the cranks the pinch bolts used on one of the crank arms are actually there to allow the crank to be tightened without putting too much pressure on the bearings. It is the antithesis of having a crank stop.

Speaking of crank stops. ISIS has those. It is part of the specifications on the standard. Unicycles use spacers so that the bearings don’t have to have a overly large inner diameter to fit over an integrated stop. I don’t remember if this technically qualifies them for the standard or not. But it works seemingly as well.

Some people don’t use the spacers… but that their thing and not ISIS.
Have you developed play in your cranks while using a properly sized spacer? I suppose frequent removal could lead to some play in the cranks in which case the pinch bolt idea might work. However that is not the way it works on those bikes and I’m not sure given the necesscity of specific tolerances for the spline interfacing that adding that element would be a real improvement. People would likely not have the pinch bolts adjusted just right to get the splined at the proper pressure when hitting the crank stop. There would be adjustability but also more wear and tear that put demands on that adjustability. Using an ever so slightly thiner spacer for a crank stop would allow for some adjustability. Not much would be needed if you were in fact always using a crank stop. I suppose it depends on how often you change your cranks.

It is a really interesting engineering problem. I’d love to hear from some non-cycling experts… i.e. experts:)

The reason we have crank creep is that we don’t implement the ISIS standard properly. The ISIS standard requires a crank stop; the torque of the crank should be against the stop, not against the splines. We have ISIS-like cranks where the torque is against the splines. The angle of the splines is 1 degree rather than 2 degrees so this becomes more of a problem than it is with standard square taper cranks.

We didn’t want to implement the ISIS standard properly, mostly because to implement it properly requires much larger bearings than we’re used to using. (Probably 25x47x12 as opposed to the 22x42x12 that we’re currently using). But it probably would be better to have a 25x47x12 bearing, a real crank stop, and a frame with a larger bearing holder than a 22x42x12 bearing and a system without definable tolerances.

That is, in fact, the ISIS spec; you don’t need to combine it with anything. You just need to make the bearing (and thus the bearing holders) big enough to fit over the crank stop.

Thanks Tholub, I am remembering some of your points from some other threads.

So really what we need is to do ISIS correctly, which makes sense, but it doesn’t seem like this is going to happen.

What really got me thiking about this is a problem I am having with the Oregon hub and the Venture II cranks. I am on hub #2and crank #3. The problem is that cranks go onto the splines so far that there is barely enough spline remaining to get them snug. I have a wide variety of spacers and have gone spacerless, though going spacerless is a good way to get bearing shift. I try to balance the spline “tightness” with crank to spacer “pressure”. The problem is that spacer pressure alone is not enough to keep a crank from creaking, though it does prevent creep.

The first crank set on the Oregon, a 165 Venture II, I could never get tight enough, they creaked constantly, so I switched to some qu ax street chromoly which worked fine. I wanted shorter cranks, so I switched to some Venture II 150 and the crank creeped over a a couple rides and became creakers. So then I ran some Moment 150, which was better, but they also maxed the spline depth. This same pair of Moments were already maxed on my Nimbus wide standard hub, so I knew that would be a problem. So then I installed some brand spankin new Venture II 150 and they maxed the spline depth as they got tight. I know that if they start creaking, then that set of cranks is done as well.

KH and Nimbus use the same mfg, so I can’t imagine that I’m the only one with this problem. The problem is on both of my Nimbus hubs, which are the 2011 redesign standard wide 100mm and the Oregon super wide 125mm. I don’t think I had this problem on older kh or nimbus hubs.

The steel cranks have been the best, but they are hard to find and kinda heavy, but that’s where I’m headed; QuAx 145 chromoly street cranks to replace the 150 ventures.

I’m just kinda frustrated because it seems like this should be an issue resolved during design.

Maybe take a micrometer to those things and see if there is an difference in some measurement.

Could you clean the crank surfaces and then shim then with a thin sheet of metal to artificially build up the contact surface? I am thinking aluminum foil. It would be a kluge, but if you could securely mount your nice cranks for another year it might be useful. It would be aluminum on aluminum on steel, which does not sound that bad.


Something sounds off. I have been running a nimbus hub with either KH moment or Sinz cranks for 2 years and I’ve only had to replace the bearings once for maintenence reasons. My cranks don’t creak or creep. Could it be an issue with the ventures?

The Ventures are pretty soft aluminum, so they’re more prone to deforming than the Moments.

justtysen and tholub said what I was going to say. I’ll just add that even with soft aluminum cranks (Ventures and Qu-Ax), they should still be fairly durable when installed properly. Cleaning the interface and using a torque wrench when installing the cranks can make a big difference in crank durability.

The Ventures crank spline may be too large and the Nimbus hub splines (Oregon and Nimbus Wide) may be too small. Like Tirving I didn’t have a crank creap or creak problem until the newer hubs and cranks.

I must have taken my Moments on and off the older Nimbus and KH hubs dozens of times and never had a problem; well there were some hub issues… The QuAx and K1 cranks are not a problem that I can tell. I always grease the splines well per ISIS specs.

Nimbus unis are often supplied with a thick spacer and it’s suggested that toqueing the crank into the spacer is sufficient to keep the cranks tight, but in my experience that is not the case. If the crank is not drawn far enough onto the splines, it will be tight against the spacer but will develop rotational play on the splines; makes sounds like creaking.

So no one else is having this problem?

The last images I saw of KH’s prototype disc brake (outboard mounted) G26 showed a crank with what looked like some allen tightening bolts that would clamp the crank onto the splines to stop the creep.

i have been riding most days and beside some scratches and lots of mud and some pedals! no creaking!

Really? Do you have a link to those pics? I think that would solve some problems, esp for folks using disc brakes on Gunis.

Is there a way to machine a thick steel washer (2-3mm) that goes over the splines, but won’t ride up onto unmachined portion of the spindle? Maybe combine the “machined” steel washer with an aluminum spacer to prevent bearing slippage

What I’m thinking is that one side of the washer is machined straight for the spline, the other side is angled so it smoothly rests against the “ramps” where the splines diminish.

I don’t understand how that would be any different than what we have now with a spacer that fits between the crank and inner race of the bearing.

I used to ride without spacers and switched cranks lots, now I generally (not always though I should) use spacers and don’t have any problems with the cranks that I space properly.

If the supplied spacers are too large I use a stack of thin C-clips instead. No spacer is probably better than a spacer that is too large.

I have seen a trail side repair where someone put a candy wrapper between their crank and spindle. Eliminated slop and at least lasted the ride.

I use PVC pipe for my spacer it work very well :smiley:

@ nurseben- The picture of KH’s prototype was in the ‘pictures of your latest ride’ thread, with some searching you might be able to find it.


Yeah, in a sense it would be no different, BUT, how much side load can the bearings take ,AND, what happend if the bearing pressure cause the spindle to move in the hub? They are just pressed into the hub.

The idea I’m getting at is that this “washer” would be a hard stop, as if it were machined onto the spindle.

If KH is making his cranks with pinch bolts, then I’m not the only one who has worked this out. I wonder when his cranks will be available…

There isn’t any side load on the bearings as the inner bearing race is pressed against the step on the hub before the spoke flange and the spacer then pushes onto the other side of the inner race, there is no side load onto the ball bearings / retainer itself.

The spacer solution works but as has been said the alternative solution would be larger bearings to facilitate a machined stop in the correct place on the axle for the crank to be torqued against as per the ISIS specs. Although unlike spacers you would/could still get bearing so again we go back to the current setup which with correctly sized spacers is actually probably the best solution?:stuck_out_tongue: :thinking:

I always loctite my crank bolts on once the crank has settled as I have trashed too many expensive cranks on my bikes from a lose bolt and literally one hard up hill slog (I ride single speed). Uni parts are so cheap compared to what I used to spend on my MTB that I am not to fussed if I have to change “stretched” cranks a few times a year :stuck_out_tongue:

ok, I think I can answer some of the things here with reasonable authority.

First I will say that I believe that the ISIS standard is great for unicycles. Here are some of the reasons why it does work for us.

  1. the shaft size is relatively small, so this keeps the bearings down in size, hence reducing the weight without major loss in the bearing properties.
  2. It is tolerant to the shock treatment that is common on unicycles.
  3. The use of spacers has 2 functions, it not only gives a hard stop for the cranks but also holds the bearings in place.
  4. The standard is established with unicycle manufacturers and this gives considerably greater choice to the users.

Here is the ISIS standard (it looks like the main site is down).
The Unicycle manufacturers actually work together on this (this would be unheard of in the bike industry). They follow the standard for the tolerances on the splines and all its basic principals. Although if you do the calculations on the tolerances you will find that the ISIS does not work as written (and never has); so they agreed to tighten the standard, working to less than half the specification tolerance! The “male cranks stop” is replaced with our spacers and are critical to the design, but even with our tighter tolerances, we have found that we need to supply different size spacers with different products and allow for creep if cranks are taken on and off regularly.

I can not say why Nurse Ben is having so many problems with his fitting of the ISIS cranks. It is not the norm, by any means. The vast majority of riders have no problems with creep or creaking.

Lets clears some things up.

  1. There is no torque setting in the ISIS standard.
  2. Venture 2 cranks are the same material and harness as the Moment cranks, it is also the same material and speciation used by some of the best of the mountain bike cranks… it is also considerably harder than most.
  3. Using a pinch bolt on deep splines as ISIS is not a standard solution.