Originally Posted by seypat

Looking at the brochures, those frames have different geometry dimensions. Still, if you duplicated your critical fit measurements from the Trek to the IM, you should be okay. Take a couple of measurements from the Trek and make sure the are the same on the other frames. Start with the saddle in the middle, then micro adjust. For myself, I use 3 measurements.

Center of BB along ST to top of saddle.
Center of BB in a straight line to center of handlebars.
Front of saddle to center of handlebars.

I get those measurements the same from bike to bike and they all fit. I can ride 52-58 frames that way. However, the 52 has too much seatpost showing and the 58 has too little. Some of my bikes have longer/shorter stems than others. Some have more/less saddle to bar drop. They all fit though. The brand, year or even tubing set doesn't really matter. I've never really had a ill fitting bike. The oldest 2 are a pair of 1972s. One is a 56 racing frame. The other is a 54 sport tourer. The youngest is a 1990/91 52cm racing/crit bike. In this particular case, I have an 82 22.5" Trek 412, an 85 56cm IM and an 87 56cm Japanese market IM. I notice a little differences in the tubing, but that is about it.

Same for saddles. Give me some type of upper level sport touring saddle/not racing saddle design from the 80s and I can ride it all day long. I don't even need a test ride. Those reissued Selle Turbos that are out, Sweet! I don't even break out cycling shorts for rides shorter than 20 miles. I have ridden SOTR every year except the first and this year. Every year except for 2, I have ridden on a different bike. Every one of those years except for 2, I have only had a shakedown ride on the bike before the event. They all fit and felt good.

In summary, if the fit on the Trek really works, duplicate it on your other bikes. You might have to change out some stems. If you've already done that, I don't know what to tell you.