After years of riding (and suffering) with ski boots I finally stepped up to the plate and bought a pair dedicated hard boots. I picked up a pair of UPZ RTRs and was excited to try them out. What I didn't realize that UPZ boots don't work very well with the TD1s.
THE PROBLEM:
I took a good look at everything and it appeared that the channel on heal of the boot was too high for the bail on the TD1s. This causes the bail to be angled upward slightly while trying to engage. The bail (right where it bends) hits the sides of the heal before the top of the bail engages. As the boot slides back, the bail gets knocked down.
My first thought was that I might be able to bend the bail so that it would be properly lined up with the channel. The problem is that it would probably still be too short/low and it might weaken the bail if I bent it too much. My second though was to lengthen the bail by threading the lugs out further, but I had read that it's not a good idea to have the threads exposed.
So I emailed Dan Yoja at UPZ to see if he had any info. I had read that some people used a dremel tool to open up the channel. (It also looked like it would be possible to grind down the shell on either side of the heal so that the sides of the bail could pass by and allow the back of the bail to reach it's destination.) He felt that most people worked with the bails and recommended that I contact Bomber to see if they had any ideas.
The response from Bomber was that they don't recommend UPZ boots with their bindings due to possible failure and they don't have any parts available that fit the boot. They did mention that they have a binding that will fit the UPZ boots better than the TD1, but they can't recommend it. They were very helpful and offered a lot of useful advice on boots. They gave me the heads up on the possible safety issue. I found Tex's thread and will be T-nutting the toe pieces just to be safe!
My options were to buy a new binding that will fit the boot (not in the budget), sell the RTRs and buy another boot that will fit the binding (I would hate to take a bath on a new boot), or figure out a way to solve the problem without compromising the safety of the boot or binding.
MY SOLUTION:
Sand down base of the replaceable rubber sole (just he heal!)
It lowered the back of the boot enough so that the bail will fit in the channel.
Back to back:
I didn't have to modify the boot's shell or the binding and the sole can be easily replaced if I change bindings or want to sell the boots. It also seemed like the safest thing to do in this situation.
I'm not sure how many TD1s are still out there, but hopefully this will be helpful if someone else makes the same mistake I did.