A little while ago, I wrote about how I converted my regular-joe mountain bike into something more suitable for commuting along the city streets. I was feeling quite pleased with myself for successfully swapping out the original suspension forks for a rigid set more suited to the job at hand, a tricky enough task that could have gone badly wrong. The modified bike worked well and was significantly faster along the streets than the previous configuration.
But all was not perfection. Problems surfaced. It seems I was clever, but not quite clever enough.
After a short while I noticed there was significant “play” or wobble in the new headset and forks – if I clamped the brakes on while standing beside the bike, it was still possible to rock it back and forward by quite some way. This was making the front end unstable under braking and that’s not something you want for travelling in traffic.
After consulting more knowledgeable folk on the BikeRadar Forums, I realised I’d made a couple of mistakes when fitting the new forks.
Firstly, I’d cut the fork steerer tube such that I hadn’t left enough clearance between the top of the steerer and the top of the stem where the star nut cover clamps down. This meant that the cover was butting up against the top of the stem and couldn’t clamp the whole headset assembly together with enough force to hold it as tightly as required, resulting in the wobble and play I was feeling. Simply inserting an extra 5mm headset spacer below the stem clamp gave the correct clearance and allowed the star nut to function as designed.
Not enough clearance between the top of the steerer tube and the top of the stem
At least 5mm clearance is required
My second mistake was in tightening the stem clamp before the star nut. Doing so fixed the stem in place, but again prevented the star nut from clamping the headset assembly together with the required force to hold it in place properly. Simply changing the order in which I fixed the bolts solved this little problem!
Tighten the star but before the stem clamp bolts
So, all in all, just some easily rectified beginner’s mistakes. I’d never disassembled an Aheadset before and neither of the above points were mentioned in any of the tutorial articles I’d found, so I thought it might help to have them detailed somewhere in case others had the same problem.
With it’s newly secured front end (and also a more comfortable saddle), my new commuter machine is working a lot better.
I notice that you use the star nuts inserted into the top of the fork stem. I use a more robust and removable star nut from under the fork, giving a tighter headset that minimizes loosening of the fork on the descents.
You mean a bolt through clamp type arrangement? I’d looked at those as they seemed much easier to fit than the regular star nut, but had been warned of them being not robust enough. I take it you disagree?
hmm.. I do not think that this was really your problem. Yes it is true that you need to tighten your stem cap first for proper preload before you lock down your stem. (this was probably your biggest mistake in the first place) However, you only need 2mm clearance above them steerer tube. 5mm is way too much and in some cases (off road MTB application especially) this is dangerous. Did you take the old race crown off of your old fork and put it on your new fork? If you did not, then your bearings are not properly seated on the fork and you have placed may way too much (not to mention uneven) pressure on your bearings. This caused a False positive for your fix and will end up costing you a new headset in the future.
Thanks for the advice Mike. This bike is only ever used on the road so I’ve got away with the 5mm clearance so far, but I’ll look into reducing it if I can.
I did swap the race crown to the new forks. It’s interesting that you mention uneven pressure on the bearings as it does feel the bars aren’t turning smoothly all the time, but rather in “steps” sometimes. I could imagine this is down to something being wrong with the bearing setup, what do you think?