Bernard sent in the following question:
“I have a steel touring bike from 1984. I love the bike because of the all-day comfort these old frames offer, but the 6-speed freewheel/Suntour XC “elliptical” chainrings and prototype index/friction downtube shifters combination don’t work that well, as it tends to want to slip out of gear. Is it a practical alternative to swap in a modern indexed shifting system?”
The bike in question — on tour in France:
Good news, Bernard…this is an entirely feasible process. Luckily, just about anything is possible in converting an old bike into something more modern — there are quite a few companies out there who make specialized adapters and such to resurrect an old friend and to teach him new tricks!
To set up modern indexing shift systems on an older bike, there are a couple things to consider: dropout spacing and how many speeds you want in the finished bike (deciding now can really simplify the conversion process, as we will see).
After speaking with Bernard, I learned that he is willing to do the full upgrade — shifters, new rear wheel, derailleurs and new chainrings. The chainring part is easy. Merely swap the old Suntour OvalTech chainrings for modern 8- or 9-speed specific rings…no crank replacement required!
Dropout spacing is really the only tricky consideration. On one- through 5-speed bikes, the rear dropout spacing was typically 120mm. With six speed systems and early “ultra 7” systems, the dropout spacing jumped up to 126mm. Modern 9- and 10-speed drivetrains have 130mm spacing. Since Bernard indicated that he currently has a 6-speed freewheel, the frame’s spacing need to be pushed out an additional 4mm. I’ve covered doing this in another article, but if you’re not comfortable doing it yourself, any competent bike shop should be able to help. Again, luck is on Bernard’s side, as the frame in question is steel. Don’t try this on an aluminum or carbon frame!
The only specialized equipment needed to modernize the shifting system on this bike (aside from the new components themselves) are downtube-mounted cable stops such as these:
These cable stops simply bolt to the downtube shifter bosses and provide the anchor (and adjustment) for the shifter cables. If you don’t have brazed-on shifter bosses, there are band-on models available as well.
I won’t go step-by-step into the conversion itself, but after the rear dropouts are spaced correctly, simply bolt on the new components, slip the new wheel in, string your shifter cables and adjust everything so it shifts cleanly.
Here’s a handy trick if you’re strapped for cash or don’t want to do the full-tilt conversion…and the reason I suggested deciding on the number of gears needed before you run headlong into this conversion project: if you have a seven-speed freewheel (Shimano still makes Hyperglide-compatible 6 and 7 speed freewheels in limited quantities!), you can make it work as a modern indexed system with 8-speed indexed shifters (readily available on the secondhand market, such as Ebay). No new rear wheel or rear derailleur required! You’ll just have an extra “ghost click” on the shifter. The only kink is that sometimes there’s not quite enough clearance between chainstay and smallest cog, but that is easily rectified by slipping a couple spacers under the drive-side hub locknut (2 or 3mm is all it takes). Sometimes simple is best…
Finally, the last consideration is not to mix brands. There are adapters to make Shimano components play nice with Campagnolo or SRAM, but it’s better to “keep things in the family” for precision’s sake.
It is really fun and rewarding to breathe new life into an old friend — you CAN teach an old dog new tricks with a little tinkering. Bernard, be sure to tell us how it all works out, and happy riding!
Have a cycling-related question? Just Ask Jack! Click on the link in the right-hand column to send me your questions.