Nate Gibson

1. Your chain line is probably off. A chain catcher will only help if the chain falls off the inner ring.

2. A TT bike should have a minimum of 54-55T in the front and an 11 in the rear. Anything smaller than that and the TT gods will be so angry they'll make your bike not shift. If the TT has downhill(like cascade) you're gonna need to go even bigger.

Stewart Campbell

So I've been building and working on my bikes for years and only once have I dropped my chin (inside.)  I just finished building a TT bike and when I shift to the big ring and down a couple of cogs, my chin will drop to the inside.

Now before I get all random answers...my derailleur is dialed in perfectly with the L screws, height and rotation.  My chain is the right length and RD is working fine.  

The only problem that I can see is with the rings.  I'm running a 34/50, I know that it is weird for a TT but I am a spinner and it works for all local TT races with the cassette that I prefer 12-21.  BUT, this is where the problem might be...two different brand of rings.  The inner is a sram red and the outer is an aero KCMC, maybe the KCMC is only ramped for a 36T ring? I did the same ring combo all last year on my old bike but both rings were sram red and it worked fine.

I'm going to play around with it a bit more in the morning before I throw on a chain catcher (one that monts to the FD allen screw.)

Any thought about this?  As any other home bike mechanic ever just have a combo that just does not wont to work?

Thanks,
Stewart