I’ve just built a 36" wheel with this hub (https://www.unicycle.uk.com/unicycle-parts/hubs-bearings/nimbus-isis-disc-steel-hub-36-hole-125mm.html), and then I saw a review saying that there is a problem with fitting cranks to this hub.
Has anyone had any experience with this hub? Were there any problems? Did you solve the problems?
The review:
This hub looks good and strong but is somehow out of tolerances. It cames with 6mm spacers but they cannot not be used with Venture2 cranks since the bolt is bottoming before the crank hits the spacer. I destroyed one pair of Venture2 cranks before I recognized the issue. Both bolts were tight but the cranks became floppy. I have now installed brand new Venture2 cranks with 6.6mm spacers and will see if it works. I cannot use thinner spacer since otherwise crank - spacer - bearing will not be tight. If it’s not working then only option is to grind the axle (voids warranty?) and use 5mm spacers. (Posted on 18/04/2018)
UDC sells extra long crank bolts. Would this solve the issue you quoted?
I think it’s the opposite: Shorter bolts or wider spacers is needed. I thougt all the ISIS hubs were the same but maybe not.
I just bought a spacer “kit” from UDC with a variety of spacers from 1-6mm. Mostly, I’m buying the kit for the narrower spacers. I am currently combining two different width spacers on my 26" muni, because I don’t have every size of individual spacers. So far, this doesn’t seem to be a problem. I think it’s important to use the right width of spacers. Too narrow and there’s a gap or the cranks are pressed too hard against the splines, causing the crank interface to deform. If the spacers are too wide, there will be play in the interface. Recently, I have minimized the distance I press the cranks onto the hub…while maximizing the amount of torque on the hub bolts. This, I think, may be better for the life of the cranks. However, it’s important for me to check the tightness of the hub bolts frequently. If there is a tiny amount of play, along the axis of rotation, in the setup…because I haven’t pressed the cranks far enough along the splines…I think this is still okay, as long as the spacers are present and any side-to-side wiggling of the cranks is avoided.
It’d be nice if UDC shipped a couple extra spacers, perhaps of a lesser width, with their new unicycles. Also, some educational materials about the ISIS interface would be helpful, as there seems to be a lot of general confusion about the spec, with bad results.
Roger (UDC UK) suggested 8mm spacers (I have 6,7, and 8mm). I’m familiar with ISIS, but I am wondering if this hub is differnt from other hubs. I have used Venture cranks with 6mm spacers on other hubs without any issues earlier (well, maybe som creaking). This hub has no room for spacers inside the bearings which i beleive my other hubs has. I’ll try with different spacers as soon as I get a new Foss tube in the mail.
It is a combination of different tolerances.
Long ISIS interface on hub + small width crank (short ISIS interface) > it can happen that the carnk bolt will touch the hub axle before the crank is thight.
In addition it depends on the axial diameter of the ISIS interface. If you have a large ISIS hole in crank and smallish ISIS axle, crank will mover further on axle (and vice versa).
To my experiance the new VCX cranks have a thight fit (axial) and they are quite wideish (for crank roll tricks). Then you typically need 7 or 8mm spacers instead of 6mm to get a proper fit.
I decided to go with 7mm spacers as 8mm just looked very wide. I tightened the bolts, and went for a 15 km ride without any problems. I checked it afterwards and everything seems fine. I’ll report back if there’s any problems later.