Clamp On DT Indexed Shifters for Shimano
 

I'm continuing my 1990 Trek 330 refurbish which came with 6 speed indexed Light Action parts and wonky shifters that clamp on the handlebars (they are shimano). The shifters are goofy looking but the main problem is the thumb levers don't shift easily. I dropped some oil in them but it doesn't seem to help so I'm considering some clamp on DT index shifters for 6 speed and would like to know of my brand options - Shimano only? I saw some cheap Sunrace 6/7 speed that claim to be Shimano compliant. Any other options?

Thanks, also there are brazed on cable stops on the DT.

Does the bike have cable stops, or braze-ons for shifters? If the latter, you can find lots of NOS and used 6/7 speed DT shifters out there.

Alternately, I've had good luck with Shimano A070 shifters -- they also mount onto the tops of the handlebars.

About all of the band-on downtube shifters I've seen are friction. If Sun Race offers indexing band-on shifters they are probably the only ones.

I've seen a clamp band with generic mounts for DT shifters. You can hang Dura-Ace off gas pipe if you like.

But IMO the cable stops make some sort of bar-mounted shifter a no-brainer IMO.

If the frame's OLD is 130mm I'd stick a cassette hub in the wheel and go 8 or 9s and STIs or bar-ends (10s Shimano indexing is sketchy), otherwise I'd just bung on a 7s HG freewheel and re-space and dish if necessary, and get some 7s STIs or bar-ends.

It's possible to make do without the adjusters since there's one on the RD and a technique exists to adjust the FD tension without a barrel adjuster.

Based on the 1990 Trek catalog (http://www.vintage-trek.com/images/t...rek/90Trek.pdf ) that year's Trek 330 used a Shimano 7-speed freewheel and it's almost certainly spaced 126 mm. It did come with stem shifters but had braze-on dt shifter bosses so standard downtube shifters should fit.

If the OP's came with a 6-speed freewheel it was obviously changed by the previous owner and perhaps that's why the OEM shifters (7-speed SIS) don't work well.

Your easiest option may be to buy the SunRace 7-speed clamp-on DT shifters (which work fine in my experience) and buy a cheap 7-speed freewheel (for about the same cost again as the shifters). As HillRider points out, your shifters (if they are original) might actually be 7-speed.
A 7-speed freewheel will be wider than the 6-speed, though not by the full width of a cog (as the gears are spaced slightly closer together). But many rear wheels from that era have spacing to fit wider freewheels (or respace decrease the amount of dish on the wheelbuild). You need room for the chain to fit on the smallest rear cog without rubbing against the dropout. Here is an example of a 5-speed freewheel spaced close to the dropouts to minimize dish of the rear wheel, but not close enough that the chain rubs against the dropout when the chain is on the smallest cog.

Yeah, the other day I threw a 7s freewheel on a guy's wheel in place of a 6s one and there was plenty of room.

I bought that same bike for my wife as a wedding present! Hers has a 6 speed freewheel, 126 mm frame spacing, and cable stops on the down tube.
Having said that, a few years ago I picked up and refurbished an old Schwinn (I think LeTour?) at the swap shop at the local dump. It had indexed 7 speed down tube shifters. Looking through Bikepedia, they were probably shimano 300 EX or RSX levers. I have no idea how hard they are to come by, and they were on braze-on bosses as I recall.

Duh, I forgot the specs said 7 speed but this came with a 6 speed freewheel! Yes it has the bar mounted shifters and they are 7 speed (6 clicks), brazed-on cable stops, not shifter bosses. Its indexed shifting, shouldn't the shifters work for 6? Maybe, but the main thing is to see if I can get those shifters working well and maybe put a new/old 7 speed freewheel on the back. Then I can get the Sunrace 6/7 clamp-ons if I have to. No wonder I got this bike cheap. I'm learning.

No, 6-speed and 7-speed freewheels have different cog-to-cog spacing and a 7-speed shifter will not shift a 6-speed freewheel across more than two or three cogs before the spacing difference makes it sloppy and inaccurate.

I had the same problem on an old Trek I bought used. The original owner had put a 7-speed indexed barend shifters on bike that came with 6-speed freewheel and the shifting was so bad he was running the shifters in friction mode. A 7-speed freewheel made everything work perfectly.

Not sure if this might help, but loosescrews.com is liquidating their stock, including some indexed downtube shifters and parts:

http://loosescrews.com/index.cgi?nr=...d=422266712276