KH36, split washers in the bearing cups and a disconcerting rattle

My KH36 arrived on Monday; I gleefully put it together in the office and rode it home. This is my first 36er and its incredibly fun to ride. I must be among the lucky ones, because free mounting isn’t presenting a problem at all. However…

When putting it together I noticed after attaching the wheel to the frame, that the wheel could wobble/rattle side to side somewhat. Upon closer inspection, it appeared that one of the bearings was slightly loose inside the bearing cups. The bearing cups were tight, sandwiching the split washers between the cup halves. At first I thought maybe this bearing was smaller than the other but later confirmed with a vernier caliper that they are both 42mm in diameter. So I removed the split washers from the side with the loose bearing cup. This removed the wobble and I could no longer see any movement of the bearing inside the cup(s) - shaking the uni vigorously showed no unexpected rattle/movement.

As I rode over bumps on the way home, I observed some rattling which could be felt by my hand on the seat bumper (but not my feet). I figured this was just loose screws on the seat/bumper and didn’t think much of it. I tightened every screw on the seat when I got home. But the rattle remained during my next ride.

This morning before riding, I removed the frame from the wheel and inspected the bearings more closely. They both look normal, cosmetically (albeit a tiny amount of blue paint has rubbed off on them). When reattaching the frame I did not use the split washers in either bearing cup. The rattle has now significantly reduced, but is still perceptible. I don’t want to tighten the cups any more than I have.

Anyone got a clue? Is this something to be concerned about?

My KH29 has the split washers in the cups and I’ve never noticed any rattle like this. Should I compare the bearing cups on the 29er with the 36er to see if they are the same size? Or swap them over to see if that results in a fix for the 36er or a rattle with the 29er?

Washers between the cup halves? One of us is doing it wrong. Mine fit pretty tight with just a tiny bit of room to spare with no washers. When I got it the washers were on the bolt at the head, not between the cups. I could very well be doing it wrong though. But I don’t think any washers would fit between on mine.

It’s still not tight even without the washers between the cups? Sounds odd.

Yeah, the washers go on the bolt head, not between the cups. Did you check to see if the adjustable seat post could be what is rattling?

There are washers on the bolt heads. There are additional washers - upon googling these appear to be called “spring lock washers”. I had assumed these go between the bearing cups to avoid over tightening - this is where I’d put them on the KH29 as they’re not mentioned in the instructions for putting the machine together.

When I leave these washers out, the cups look and feel tight. I can hold a crank with one hand and the frame with the other, shake the uni, and I get no movement. But drop down a curb, or go over a bump and I feel something.

I have gone over all the bolts in the seat, seatpost and bumper. They are definitely all tight.

My split washers are under the bolt heads along with the regular washers. The rattle could be a free spacer moving around on the hub. Give your spacers a poke and see if they move.

The spring washers are only functional as a lock washer when immediately adjacent to a rotating part (i.e. the bolt head). In between the two halves of the bearing holder, they are just serving as a spacer. This spacer function is probably preventing you from properly tightening the bearing holder around the bearing, so the bearing is wobbling around. I note that on my KH frame, the two halves of the bearing holders almost touch when tighened, maybe with 1/2mm in between, not enough to add a washer.

After removing those washers, try tightening your cranks and pedals, which seem to be common sources of noise - particularly cranks when new.

Ok, I put the spring lock washers under the bolt heads and tightened the bolts. I can’t get the bolts tight/loose enough that the wheel spins super freely and there is no movement over bumps. So I’ve tightened just a bit more than I would prefer. The wheel still spins freely, but it looks like its relying on the rotational inertia of the wheel to do so. Its certainly not spinning as freely as with the frame upside down just resting on the bearings cups.

But I don’t feel any rattle over bumps/curbs now, so I’m happy. Thanks all!