Bicycle Tutor

I want to move the downtube, indexed shifters to the handlebars of my circa 1990 Lotus road bike. Drivetrain is Sun Tour 52/42 biopace chainrings and 6 speed (14-28) rear derailleur.

Will 7,8,9 speed Rapid Fire shifters work?

Does anyone have a better way to move downtube shifter to handlebars for under $100?

Also, I want to replace 42 tooth chainring with a 34 tooth. Will the old derailleur handle it?

The first problem you'll have with Rapid Fire shifters is whether they can clamp to your current handlebars. They are designed for mountain bike handlebars, not road bike drop handlebars. I have no idea whether they can pull your drive train because I don't understand your drive train (Biopace+Sun Tour, huh?).

You can transfer your down tube shift levers to your current drop down handlebars using Paul Components Thumbies but that's pricey.

You might also consider bar end (handlebar) mounts using your current down tube shift levers and current handlebars. But that's pricey too.

I think there are still bar shifters out there (Sun, Sun Race?) for road bars but they are probably low quality and friction (not that there's anything wrong with friction shifting!). You might try bikeusa and bikepartsusa, Google them.

On the Biopace mod you have in mind, to understand this abandoned technology:

http://www.sheldonbrown.com/biopace.html

So I wonder why you want to do this and can you find the right bcd?

Maybe the bike, the way it is, just needs the components removed and cleaned? And put back on and tuned?

(Jun 6, 2012 01:34 PM)Tim M Wrote:  On the Biopace mod you have in mind, to understand this abandoned technology:

http://www.sheldonbrown.com/biopace.html

Not an abandoned technology. I saw pro riders with elliptical crank sets one their bikes during the Criterium du Dauphine just a couple of days ago.

I agree with Tim, Rapidfie/STI shifters weren't meant for drop handlebars. Mixing and matching newer shifters with older freewheels and cassettes can work if the sprocket centre to centre spacing is the same, for example: http://forums.bicycletutor.com/newreply.php?tid=4110, a Shimano 7 speed shifter may work with a Sun Tour "Ultra" 6 speed Freewheel. However, for this you'd have to find some old 7 speed shifters and an old 6 speed freewheel and it might be a lot of hassle.

Some more info: http://sheldonbrown.com/k7.html

I would be inclined to either stick with the current drivetrain and downtube shifters, or go the whole hog, buy a new rear wheel with a modern 10sp cassette compatible hub and the road mechs and shifters to suit. Even though I think that the ever increasing number of rear sprockets has more to do with marketing than real world performance, the sad fact is, that you can now only buy used or lower end drivetrain and shifter components with anything less than a 10 speeds for road bikes.

Low end thumb shifters like these:
http://www.amazon.com/Falcon-friction-ATB-thumb-shifters/dp/B0025UH44I could work because the clamp can be spread to fit around the drop bars and then retightened. You can't do that on shifters with cast clamps. They are friction, but your probably going to have to stay with friction on an older 6 speed drivetrain regardless.

Note that you'll also need cable stops to replace the downtube shifters. Something like this: http://www.amazon.com/Shimano-Housing-Stop-Down-Tube/dp/B001JH9KUY/

Another option is shifters that mount on the handlebar stem. Something like this: http://www.cycleandsurf.com/road/9582-shiftersunracestemdtslr397xfriction.html
Google "stem shifters" for more options

One big question is where you usually have your hands on the bars. If in the drops, bar end shifters are better. If up on the top flats, stem or thumb shifters may work better.

Thanks much to all who replied. A little clarification: I mistated my chainring design; they are Sugino Cycloid, not Biopace. I'm not sure if they use the same technology as Biopace, but they are definately eliptical and I like them a lot. I still want to replace the 42 ring with a smaller one (34 to 36 tooth), but I need to figure out what will work. I assume I'll have to go with a round chainring.

Thanks to your input I found Sunrace 6 speed thumb shifters (indexed like the ones on the downtube) and am ordering today, along with cable stops. They look to be ideal.

By the way, even though the bike is 20 some years old, it is only has 4k or 5k miles on it and all the drivetrain works like new. I'm only looking to get the shifters up off the downtube. It's a great bike with a more laid back geometry than my Schwinn Fastback (only 4 years old) so I still ride it quite a bit.

Again, thanks to all who replied.

I have an MTB triple chainset with Biopace rings. When I replaced the middle chainring, it was with a plain round one without any problems. However, it was the same number of teeth as the original biopace ring.

As far as I know Cycloid is very similar to Biopace, just a different brand name, but the same principal.

(Jun 8, 2012 07:49 AM)yloyak Wrote:  Sunrace 6 speed thumb shifters (indexed like the ones on the downtube)

Huh, non-shimano 6 speed indexed. Who knew.

Shouldn't be a problem mixing oval chainrings with round. You just need to get the right bolt circle diameter and watch out for chainrings that are flat versus ones that are offset from the mounting points.