Checking over a pal’s bike today, I came across an unexpected knocking- turns out that the Pro 2 hub axle spacer/cap isn’t snug in the fork dropout and neither is the axle as a result.  The dropout has over 1mm of sideplay on the axle.  Anyone seen this before?  it’s like the end cap is over a millimetre too short, or the screw in axle is too long by a similar amount.  Either way, the leg of the fork can move laterally and must be causing wear.

I had this with my Fox 36s and Pro 4 front hub. Wasn’t like it from new, not sure exactly when it started. I wish I had noticed when it started as it might have identified what I’d changed to cause it.

I was running a 20mm axle when it first came about. With the axle done up with the wheel in and the pinch bolts undone, there was still a small gap between the end caps and the fork lowers. Once the pinch bolts were done up the wheel would ‘knock’ when turning and there was play when you jiggled it. Riding the bike like this shortened the life of the front hub bearings.

I tried pushing the fork legs up to the end caps before doing he pinch bolts up, but this didn’t work. Someone suggested not pressing the hub bearings all the way in, but this just made it impossible to get the end caps on.

I had the lowers changed on mine due to damaging them. I thought this would be the end of the problem… but the play was still there.  These were the newer lowers with the insert which the axle threads into.

I eventually changed to the 15mm axle and this sorted it. I’ve since replaced these 36s with another set of same age 36s and again with the 15mm axle and conversion kit in there’s no play.

In hindsight my money would be on the 20mm axle end caps needed replacing.

Has your pal’s bike got a 20mm or 15mm axle in at the moment? If it’s the latter my theories can go straight out the window.

My instincts are that the non-brake side end cap has worn for some reason and has lost about 1mm on it’s outboard side, where it should fit snugly into the dropout.

Correct- it’s an old set up, with 20mm axle.  The bike is away to it’s home again now and I didn’t have enough time last weekend to try out with another 20mm front from another bike here.  The owner is a light rider and I didn’t have time to swap out my larger discs so that’ll be the first step, try another wheel.  I’ve an older bike with a ten+ year old Bulb on it and another with a Halo Spin Doctor, one of the old ones with loose end caps.  I can try both.