Ironfish653

Building more miles, and trying to get a little more functionality out of my old Bridgestone without breaking the bank.
Right now it's a single (53-17) while I get the rest of the driveline sorted out.

1975~Bridgestone Superlight (JDM) 10-speed Suntour V-GT driveline.
The original (shimano) freewheel was full of shrapnel, so it's not going back. A primordial Megarange 14-36 5-speed.

Adding D/T shift levers, replacing the knackered stem-shift, and I see 6-7 spd index capability, or friction mode. Levers will either be the Sunrace clamp-on setup, or if I can get something from the vintage LBS on a ProblemSolvers mount.
5-speed freewheels are cheap, but having the extra step, (or a megarange) would be nice on longer rides.

what else needs to be factored besides the levers and derailleurs when trying to stuff an extra gear in?

randyjawa 

You will need a longer axle, a couple of spacers and the six cog freewheel that is compatible with your rear hub's thread pattern. You will probably also need a longer rear skewer, assuming you are using quick release hubs. You might even have to spread the stays a wee bit but chances are you can get away without doing so, if you get lucky (your five speed FW will fit into 120mm drop spacing while the six speed will seek 125mm, but it is often close enough to not worry too much about. My opinion, of course.

CliffordK

There are a lot of variables.

What is the rear spacing on the bike now?
How much space is there to the right of the small sprocket?

A lot of old freewheels were mounted with so much space to the right that one could drop a chain between the freewheel and the chainstays/seatstays. One really doesn't need much space. So it is quite possible that one could just screw on a 6 speed freewheel. Maybe even 7 speed.

Rather than lengthening the axle, one may need to move washers and spacers from the left side of the hub to the right. But technically, one should also re-dish the wheel at the same time.

nfmisso

The V-GT may not work with indexed shifters - which were not even thought of when the V-GT was designed in the late 1960s/early 1970s.

I would purchase a 6 speed freewheel and do a trial fit, does not cost much.

Salamandrine 

Going for 5 to 6 speed is typically pretty simple and is unlikely to present a problem. If you want to go to 7, you may have some issues fitting in the 7 speed freewheel, even though they nominally both use 126 rear spacing.

To do this properly the frame needs to be reset (bent open). When this is done and the alignment checked either with string or an alignment tool, the dropouts need to be realigned also so that they are parallel. The frame alignment will typically go out because right chainstays bend easier than left chainstays.

Yeah, you can simply force it open. This is fine for testing purposes, but if you ride a lot it will break axles and you have no guarantee of frame alignment.

Unless you want to buy new derailleurs too, it's probably going to be easier to simpy keep it friction shift. I'd highly recommend some old DT suntour powershifters. You should be able to pick some up cheaply.

Lascauxcaveman 

Ditto. I've done this on a couple of early-70s bikes and it was a straight swap, no muss no fuss no re-dish. The reason is the original 5-speed freewheels on those hubs had more than enough space between the small cog and driveside dropout to accommodate the slightly taller 6-speed cluster. All I had to do was adjust the hi-lo stops on the rear derailleur and I was done. @Ironfish653, post a close up pic of your rear cluster on the bike, shot from behind, and we could make an educated guess if that would work for you.

The right seven speed freewheel could possibly slip right in there too, but getting indexing to work with the old RD would be pretty hit-and-miss. Mostly miss, I'd wager.

davester

There are two ways to go here:

1. Buy an old Suntour Ultra-6 freewheel which is the same width as a standard 5-speed freewheel. This will require an 8-speed chain...readily available.

2. Spread the stays from 120mm to 126 mm OLD spacing. IMHO this is not simply a case of putting spacers on the axle and bending the stays apart. Doing so will result in slightly nonparallel dropouts which will put stress on the axle, probably resulting in eventual breakage and possibly ensuing dropout damage. If you have the stays spread then the dropouts need to be realigned so that they're parallel. My understanding is that this is not a common problem with freehubs but is a significant issue with freewheel axles. Also note that while many frames can be spread without issue, some can't and it is possible that spreading will result in breaking the brake bridge.

Edit: As I was typing, Salmandrine was posting about the same issue.

randyjawa 

I wondered about this, myself, but managed to use Suntour Accushift with a seven cog freewheel, on this old Bianchi Touring...





The nice thing about the set-up is the option to go indexed or friction, with the flip of a thingy.

eschlwc

i don't really mind my ird 5-speed freewheels. they're both 14-28t, and are smooth and quiet.

as i don't race, the only difference between the 5- and my ird 6-speed freewheel is i tend to shift a little less with the 5-speeds.

i rode one yesterday and pushed the bike hard. unless i'm ascending in the small ring, i tend to be in the second-highest gear. that's about an 85" gear (52x16).

old's'cool

+1

Be prepared to iterate. I recommend you start with cheap and incremental changes, and go to more drastic and expensive changes as you become more confident in exactly what you want, and the path/trade-offs to get there.

BTW, many of us have surplus equipment in this category, that we would be willing to part with on reasonable (or better than) terms, if we happen to have something that will help you directly.

Ironfish653

Thank you, guys.
The rear axle does indeed measure out at 126, which is good, since the rear triangle on this bike is alloy, not steel.
Lots of extra room between the FW and the frame, too, and the V-GT has enough travel to go all the way in to the spokes, so it looks like this should work.

Time to go to the co-op and look for some shifters.

eschlwc

^ the rear axle measures 126mm, or the dropouts are 126?

whatever the dropouts measure, the axle should be a little less than 10mm more than that.

Ironfish653

It's Alive! I ended up with a Shimano 14-34 Megarange 6-speed and a set of NOS Shimano SL-434 clamp-on DT shifters. The SL-434's have a 'micro ratchet' on the friction setting that works very well with the old V-GT deraliuers. The big jump to the 34 cog takes a bit of patience and finesse, but it does go.

Interesting to note, that the 5-speed Sunrace i picked up as a plan-B fits much closer to the spokes than the Shimano. I had to make a 2-mm longer axle spacer to keep the chain from rubbing the seat stay on the small cog/big ring line.

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Pompiere

I'm currently using Shimano SIS on a 1970s Sun Tour Seven derailleur to shift 7 out of 8 on my Paramount. I figured I could live without the 53-11 combo here in the flatlands.

bulldog1935

With 126mm rear axle, you can run 7 in the rear

This is a Suntour Winner 12-32t 7sp on Phil freewheel hub, asymmetric rear Synergy rim, which lets you do this without a radical wheel dish.

You can also find 126mm cassette hubs that will let you run 7sp cassettes.

The biggest advantage of more gears is when you're riding with friends with more gears and narrow gear steps.
If you have a cliff step right where they're riding, your lower gear has you spinning too fast trying to keep up, and you higher gear may be straining your knees trying to keep up.

ollo_ollo

"So it is quite possible that one could just screw on a 6 speed freewheel"
That's what I did with my Centurion Pro Tour 15. Don

bulldog1935

that's what our OP did in post 13, as well.