theDirtyLemon

1) The symptoms you describe REALLY sound like your shift cables are a bit slack.

2) The Nishiki's shifters are rattling?? That ain't right.

​​​​​​3) Bolt-on downtube shifters can sometimes slide slowly down the frame tube, loosening the shift cable. Frames from the bolt-on component era usually have a little nub on the underside of the downtube to prevent this, but if there isn't one, a shim may help.

​​​4) SunTour Power Shifters are very good; that little clicking they make isn't just a series of arbitrary detents like you sometimes get with other brands, it's a ratchet mechanism that makes 'em easier to shift (see the link for better info).
4a) If the mounting screw is cranked down too hard it can make shifting feel stiff in one direction
4b) The bar-end shifters somebody recommended have the same guts as the downtube levers you've already got.
4c) The guts of these shifters are made up of a lot of little bits and pieces which must be stacked in the correct order. It's very remotely possible somebody did this wrong.

5) Shimano 105 levers are good too, certainly at least as good as those stem-mount jobbies.

Harold74

Obviously, I agree that proper B-screw adjustment is a component of good shifting setup. That said, my setup already shifts well. It just feels low quality to me. Is it your proposal that tighter B-screw adjustment would actually reduce the amount of cable tension force required to accomplish a shift? If so, that's not something that I'd previously considered. Park's advice on B-screw is something like "don't sweat it too much if it's shifting alright". I'm just trying to understand the nature of the proposed improvement on this. I'm happy to fiddle with my B-screw endlessly if it will help.

theDirtyLemon

Cable housings are usually lined with teflon, so you don't need added lube. Old lube/grease could conceivably get a bit gummy?

Every time I've bought cable housing it comes with end caps. They've been your basic stainless steel can-with-a-hole type, not brand specific, not plastic lined (as far as I could tell), and they work just fine.

Harold74

My understanding is that the grease in the end caps is intended to block moisture ingress through that path and prevent corrosion, not to reduce friction inside of the housing itself.

My very recent experience has been that most of the cheaper cable kits will come with plastic end caps. I'm hesitant to buy $40 shift kits on a $125 bike, as one might imagine. I'd like to be able to source the end caps separately if possible.

JohnDThompson 

I imagine so, although I've never had to service any of mine. Sourcing parts might be difficult, unless you have a donor set.

They will fit on standard Campagnolo-type bosses. If your Shimano bosses are of the non-standard "A" or "B" types, then no.

The Simplex retrofriction levers came in both clamp-on and braze-on versions. The mounting hardware is not the same, so you can't just remove the levers from a clamp-on set and mount them onto brazed-on bosses.

theDirtyLemon

Grease used as a moisture seal is, like lubing your cables generally, a holdover from the old days of unlined housings when the inside of the housing was bare steel.

Plastic end caps are fine. Metal ones are available separately from online retailers like TreeFort or ModernBike or wherever. But my point was really that an unremarkable product, in this case, should serve well enough--housing end caps aren't causing your problem.

You've gotten a lot of fairly niche advice in this thread, but I suggest not worrying about that stuff. Check the fundamentals, and also consider the Trek: it has the longest cable housings and the worst shift levers (they're FIIIIINE), and it shifts better than the other two. Which means the problem probably isn't due to your shift levers or housing length. Friction shifting works the same way regardless of where you put the lever, so downtube levers should feel more similar to stem shifters than otherwise. That pretty much leaves cable and shift lever installation/adjustment.
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clubman 

Agree to disagree. Decades of archived pictures of performance bikes just won't support that 'long housings aren't a problem". And old Campy gears are generally agreed to be mediocre.





Even modern setups have less loop.

theDirtyLemon

Sure, but the longest loop of all is on OP's Trek 730, which apparently shifts the way OP likes their shifters to shift.
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VintageSteelEU

I'm not using friction shifters these days, I switched to indexed downtube ones some time ago, but DiaCompe are servicable, you can take them apart. I haven't been using these particular shifters, but from what I can see on their website, they seem to be compatible with standard braze-on mounts (probably best to ask the manufacturer or a dealer near you). However, DiaCompe do manufacture shifter levers specifically for brazed-on mounts, so you could check those out as well (Ene Touring on their website).

Harold74

Tell me more about how you like indexed downtubes if you can. Nowadays, it seems that most of the folks interested in downtube are simultaneously friction shifting fanatics. I like friction too but, for the bikes that I ride somewhat aggressively / seriously, I still prefer the indexing. I love how indexed bar end shifters feel and perform and, rationally, I'd expect similar or better performance from indexed downtube. Originally, I thought that the reach to the downtube would be off putting for me but, having tried it on the Nishiki for a few weeks now, it doesn't bother me much at all. As it turns out, my long monkey arms are good for more than just tennis and high shelves...

steelbikeguy

you didn't ask me, but I think indexed downtube shifters work quite well.. at least as well as indexed bar ends. Not quite the purity of friction, but looks right and very quick and easy to shift... just smack it and go!

I suppose the only hurdle is actually finding them... I wonder when they were last produced? I suppose the last ones were intended for use on aero bars.

Steve in Peoria

fleslider 

How does the rear derailleur hanger look? if its bent and not aligned it will also give you shifting issues.

VintageSteelEU

When I was building my current bicycle, the frame came with FC-6400 crankset. I could go back to the original configuration, use components I already had (which was a bad idea anyway) or modernise it a bit. I decided to modernise. Partly because it would allow me to shave some weight off the bicycle, partly because my experiences with friction shifters were never that great. Probably because I never had top notch stuff. I mean all was working fine, but with the levers always being the weak point. I wasn't interested in having brifters, thumb shifters or anything on the handlebar nor any cables under the handlebar tape, so keeping the shifter levers downtube seemed like a natural choice.

As for the experience of using downtube indexed shifter levers, my arms are rather long and the hand always lands on the shifter lever naturally, I don't have to search for it. The only downside (not really) is that I switched from old and battered Shimano SL-1055 to new and shiny (though cheap) Shimano SL-R400. The old set was somewhat worn out, so didn't require more than a gentle touch. SL-R400 are new and require more strength. And on a lightweight bicycle... Well, let's just say it's one thing to remember about when changing gears. I suppose the shifters will require some breaking in. Important note: new indexed shifters might require alternative cable routing when used on older derailleur.

Performance wise... Initially I went with FD-1056, RD-1056 and SL-1055 shifters. KMC X8 chain. That worked absolutely great. Unbelievably smooth, even if you shifted gears going up hill (though ones I have in my area are not really steep), you wouldn't even hear the gear change (or it would happen very quietly). Absolute magic in both directions. Well, until the chain got soaked by torrential rain (still trying to get it back into working condition) Currently I use Shimano FD-6401, RD-6401 (to keep the drivetrain in the same group, heaven knows why), 7 speed indexed freewheel (it will be 7 speed Hyperglide casette when I get round to finishing the wheels) and Shimano SL-R400 shifters (might replace them with SL-6400) and Shimano Ultegra CN-6701 chain. I had to use alternative cable routing, but the whole setup works great too. Shifting is very smooth and fluid both ways. Not as good as it was with the previous setup, but this might be down to: 1. jockey wheels being old and not spinning as nicely as the new ones in RD-1056. They are in good condition, though I believe they still need a bit of breaking in after regreasing / relubing 2. chain being 10 speed on a 7 speed cluster. By "not as good" I mean I can hear gear shifting.

VintageSteelEU

I don't know what other manufacturers like SRAM or Campy have in their lineup, Shimano has SL-R400 8 speed shifters. Other 6-8 speed shifters, be it 105 or Ultegra, can be found NOS, though usually rather pricey (well, comparing to SL-R400). There are quite a lot of them in used condition, though things to look for: 1. cracked plastic bits of the chassis, 2. completely worn out mechanism.
When it comes to 9 speed, there are Shimano Dura Ace SL-7700. These won't be cheap. I'm not sure if Shimano made any downtube levers for more than 9 speeds. A sort of workaround with more sprockets would be getting levers which can work in both index and friction mode (SL-R400 are only index) and switching between the modes when needed (probably not that great).

OK, I found out today that new (not NOS, new) Shimano Dura Ace SL-7900 (so top tier) downtube shifters can be purchased for around £60. These are 10 speed shifters! If someone actually needed 10 speed cassette or just wanted Dura Ace level of components.