Originally Posted by
T-Mar
I suspect that you have a 1991 Boardwalk that was purchased or manufactured in very late 1990, as the 1990 was spec'd with Shimano, while the 1991 version was spec'd with Sun Tour XCE and XCM. I susect the problem is that the shift levers are SunTour's index Accushift X-Press. With indexed shift systems, the derailleurs have be designed to travel the correct distance for a given cable travel. SunTour's indexed system used a different cable to travel ratio that Shimano's SIS, which is the current dominant standard. Different manufacturer's index systems are not always compatible. Mixing components is met with varying degrees of success but is a trial and error process.
The easiest solution would probably be to install a Shimano front derailleur (the Boardwalk used a top pull model) and mate it to a friction thumb shifter, bypassing the Accushift X-Press levers.
Originally Posted by
T-Mar
Alternately, start checking Ebay for SunTour ATB derailleurs of the era. Be aware that there are two clamp sizes.and both top and bottom pull versions. Prospective models include XC Comp, XCD, X-1, XCE, XCM and XCT.
So I popped over to the LBS this morning, to find that the doctor had just done exactly what you described. He'd found a top pull Shimano Acera in one of his boxes o' stuff and mated it with the existing SunTour thumb shifter, which now works on friction. The only unresolved issue was that it didn't quite fit with the existing 28-year-old plastic fender. Since I'm retired and no longer care about the niceties of commuting, I told him to just ditch the fender. I took it for a short ride and it works great.
Your knowledge of Bianchi models is impressive. In point of fact, I purchased this baby in the Spring of 1991. I just assumed it was probably the previous years' model.
Thank you!