LT testing

I already posted this in the running section, but thought I would put it here so some other people might see it and have any other ideas. I got my Christmas present a little late in the form of a HR monitor, bike shorts, and jersey. Saturday I took the HR monitor out and did a LT test. (please, don't ever make me do that again - even though I need to do it it the bike now :eek: ). So I warmed up for 20 minutes, the first 10 pretty easy, then stepping it up over the last 10min. I watched my HR climb from the 120 range to 170 at the end of the 20min (I was going at a decent pace there). I then went all out for 20 minutes, including two pretty decent hills, and used my average HR over those last 20min as my LT, which is 181. When a friend helped me test it in October it was 177, so a little improvement.

I figured out my zones to be this for the run:

LT - 181
zone 1 - 152 or less (84% and less)
zone 2 - 153-165 ( 83-91)
zone 3 - 166 - 172 (92-95)
zone 4 - 173 - 180 (96-99)
zone 5a - 181 - 185 (100-102)
zone 5b - 186 - 192 (103-106)
zone 5c - 193+ (107+)

If you gals have any hints on better ways to do the LT, or have other ways of calculating zones, I'm all ears. Maybe I can get anything corrected that needs to be done before I do the LT test on the bike.