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Bayonet fork coming loose
I've posted about this before, but I have continued having problems with the Bayonet fork on my 2008 Felt B2 Pro coming loose. I think I have finally solved the issue for good and just wanted to pass the info along to others; also, if anyone from Felt is on this board feel free to offer other tips or things to watch for. I would also suggest that you make sure that your dealers understand how to install and adjust this system! My bike has big spots rubbed through the carbon on the head tube because my dealer (a very famous West Coast tri shop) did not set this up correctly.

When I first bought the bike, the front 2 countersunk machine screws that attach the front of the adjustable stem top cap to the fork were not tightened properly by the shop and came loose within the first week. Not being familiar with the bike, I just thought that it didn't handle well going downhill (the front end would shudder under braking and turning). However, when I noticed that the decals on the sides of the head tube had been rubbed off, I started to suspect that something might be loose. A little internet digging turned up the Felt video on how to install and adjust the system. I took everything apart, re-assembled it, and all was well for several months.

Well, everything was well again until about halfway through the bike course at Wildflower, where I noticed a different symptom. The bike would creak under heavy pedal load, especially while climbing. Downhill braking and turning seemed okay, so I didn't suspect that the fork was loose. After the race, I loosened/re-tightened the seat, the handlebars, the seatpost, and the pedals (all the usual creak locations) thinking that would take care of it. Since my next race was Alcatraz, I switched to the road bike and forgot all about my TT bike.

After Alcatraz, it was time to get ready for SD International, where I would use the Felt B2 again. I rode it a couple of times and the creak was still there. Weird. I got on the bike in a stationary position and practiced weighting a pedal and pulling up on the handlebars as happens during climbing. It still seemed like a pedal or bottom bracket or something wasn't quite tight but loosening/re-tightening all of the usual suspects had no effect. I then noticed that when sitting on the bike with the front brake applied and pushing forward, I could feel the front end give a little bit. This time the rear bolt through the adjustable stem top cap had come loose. This one secures the back half of the adjustable stem top cap to the steerer tube that runs through the headset. So the fork was effectively only secured at the front end, not the back. I then noticed that the rubbing on the sides of the head tube had gotten even more severe, and now you can even see some carbon strands exposed since the clear coat is all gone.

It is now just a couple of days before the race, so I disassemble the whole thing again and re-assemble it, this time being careful to apply threadlock to all 3 bolts that secure the adjustable stem top cap to the fork and steerer tube. While tightening the front 2 machine screws though, I accidentally round out the hex drive when the key twists under pressure (this is very easy to do). Also, the top cap specifies 20N/m for these. I have found that these screws are so easy to strip I can't advise using a torque wrench on them. By the time you get to 10N/m you will get twisting and round out the hex drive like mine had ended up. Also, the shape of the top cap makes it very difficult to get any sort of hex driver in there other than a plain key or T-handle. So...

It's the day prior to SD International, and I decide to get the machine screws replaced with ones that aren't rounded out, so I stop at Ace Hardware and get a set of T-handle hex drivers and some new machine screws. I remove the handlebars and stem, the back bolt that secures the top cap to the steerer tube, and set to work on the machine screws -- unfortunately they have become so rounded out that not even the T-handle hex drivers can remove them. Now the real fun begins.

When it is the day before your most important race of the year and you have to put on safety glasses so that you can drill out screw heads on your bike, you'll start rethinking this whole triathlon business -- trust me. Anyway, after much drilling and several bit changes on my drill, the heads of the machine screws finally come off and I can remove the top cap from the fork. Now in most other cases involving drilling off screw heads, this is a time to celebrate -- you can just use your fingers to back out the screw shaft. Unfortunately in this case I had needed to use threadlocker to keep these screws from coming loose (remember the beginning of the story). These things are glued in place so it's back to Ace Hardware I go for screw extractors and pilot hole drill bits.

When it is the day before your most important race of the year and you have to put on safety glasses so that you can drill tiny pilot holes in the screw shafts of the glued-in machine screws that you had to drill the heads off of to remove, you'll start rethinking this whole triathlon business -- trust me. Not knowing which extractor size was appropriate, I got the 2 smallest ones and 2 drill bits for each. I started with the smallest, put the drill bit in the drill and started drilling. Snap. Broken drill bit. Well, that's why the spare is for. Changed it, started drilling. Snap, broken again. Okay, let's move on to the next size extractor. Change the bit, start drilling, bit doesn't break, keep drilling, keep drilling. Try to put in the extractor but the hole isn't deep enough. Resume drilling, keep drilling, put pressure on the drill but not too much, keep drilling, keep drilling. Re-try the extractor -- boom, it grabs and the broken screw shaft comes out. Now one more to go -- repeat on the other side, and success! Both of them are out.

Anyway, I finally got the whole thing back together and I didn't round out the hex drive on the screws in the process (because I used T-handle drivers instead of keys or a torque wrench). I was able to get my bike checked in (bike check in ended at 3pm) and my race went great. The bike handles very, very well when the Bayonet system is installed correctly and everything is tight. For those of you who have this bike, here are my tips to installing the top cap.

1) Watch the Bayonet assembly video from Felt.

2) Use ONLY T-Handle hex drivers when installing/removing the 2 front countersunk machine screws. Do not attempt to tighten them anywhere near the 20N/m specified on the top cap, you will round out the hex drive and soon be drilling screw heads off.

3) Use threadlock on both the 2 front machine screws AND ON the bolt that secures the back of the top cap to the steerer tube.

4) If you notice any strange handling on your bike (shuddering, twisting, creaking), inspect and re-tighten the system.

5) If you notice rubbing on the sides of the head tube, inspect and re-tighten the system.

Again, if anyone from Felt reads this -- please make sure your dealers understand this system and that they use threadlock where it needs to be applied! My bike had no threadlock on any of these fasteners, so it's no surprise that they came loose. I only wish that my great $5K+ bike didn't have to be needlessly messed up (head tube rubbing through to the carbon weave) because of bad assembly. And I'm sure mine is not the only one to have this issue.
Last edited by: need4speed: Jun 29, 09 9:09

Edit Log:

  • Post edited by need4speed (Cloudburst Summit) on Jun 29, 09 9:09