mazultav

So I got my fathers 70's Motobecane Grand Tourning. I was just riding around the neightborhood and the rear derailleur broke. I think I "overshifted" the friction shifters, if thats possible.

I was looking for a suitable replacement, does anyone know what type of suntour was on that bike?

Also I would like to know about rear derailleur compatability. Are they made for indexed or friction only, is the number of speeds important. I would like to get some indexed shifters too if anyone knows a cheap alterantive, Im not looking for new or flashy just something that works. I really like the bike if I could get it working.

cuda2k

Nearly any indexed friction rear derailleur will work with your friction shifters. Shimano and SunTour derailleurs from the mid-80's are plentyful on ebay and can be had pretty cheap.

Indexed shifters can often also be had fairly cheap, but ensure you're getting a complete and working set. Some early Shimano levers (6speed in my experience) often came in many many small parts that had to be put together in the right order. Easier said than done. Also you have to make sure that you have the right type of brazed on bosses for the shifters. Shimano SIS shifters require a specific design of boss to mount to.

Lastly - if you decide to get indexed shifting, know that the rear derailleur you buy will need to be compatable with it, and the freewheel too (# of speeds and brand). Actually, that should be the first thing considered. In any case, decide if you want indexed shifting, then replace the derailleur and possibly freewheel after that decision is made.

Others will likely be able to tell you more of what is possible with your specific bike, as I am unfimilar with your bike. Good luck.

n4zou

Rear derailleurs come in two ratios, 1:1, which covers everything up to 8 cogs and 2:1 ratio for 9 and 10 speeds. With the introduction of the 9 speed cassettes 2:1 derailleurs had to be used due to the very close spacing of the cogs. The ratio is the travel the derailleur is pulled versus the rotation of the shifter. The space between the cogs is the same for 5 and 6 speeds and then changes for each of the 7, 8, and 9/10 speed freewheels/cassettes. A 5 speed index shifter will work fine with a 6 speed cog set as you may simply press the shifter lever up past the last index mark and get the sixth cog without any problems as long as you properly set the low limit stop on the derailleur as not to go to far and crash the chain into the spokes. Pretty much any index shifter for the number of cogs on the freewheel or cassette that matches the number of indexed shifter will function fine. Example: a 7-speed SRAM grip shift will work fine on a 7-speed Shimano freewheel or cassette. A 7-speed shifter will not work properly on a 6 or 8 speed freewheel or cassette.

stronglight

° If that was the original rear derailleur... I know of two combinations which that model definitely used during the late 1970s:

1.) SunTour V-GT Luxe rear derailleur ~ 5-spd freewheel (14-32 cogs) ~ 40-52 chainrings

2.) VX-CT rear derailleur ~ 5-spd (14-32) ~ 36-44-52 chainrings.

These both were matched with Suntour downtube ratchet (friction) shifters. There "were" some indexed 5-spd and 6-spd thumb-shifters available later, but these may be VERY difficult to find now.

Most modern "touring" bikes I've seen basically use mountain bike rear derailleurs. Any modern MTB derailleurs can be used with just friction shifters as well as with their intended indexed shifters. And, even the cheaper models among Shimano's broad range of MTB derailleurs will probably shift better than most older derailleurs did.

Buy a new chain too!

I commonly run 8-speed chains (preferrably SRAM) with my old 5-speed components and they always seem to work fine. An 8-spd chain will easily glide through pretty modern rear derailleurs and your local bike shop may even have some perfectly good "demo" or very lightly used derailleurs which were simply changed out for a customer who wanted something more fancy. These are usually sold really cheap - just so the shop is not stuck with dead stock.

I would suggest you replace the freewheel, or at least look for one, now. They do wear eventually, and 5-speed freewheels are becoming more difficult to find all the time. IF you can still find one with a comparable range, a simple 5-spd replacement freewheel will save you from having to change the rear spacing of the frame to fit a longer rear axle - which a greater number of rear sprockets would require.

Perhaps someone else can tell you specifically what you should definitely NOT use. But, you really can get by VERY cheaply.

cudak888 

Have you tried this before? I have, with results less then satisfactory.

-Kurt

Grand Bois

That's an understatement!

That's not the only misinformation in that posting, but it's been a long day and I'm too tired to argue.

stronglight

n4zou: "...Rear derailleurs come in two ratios, 1:1, which covers everything up to 8 cogs and 2:1 ratio for 9 and 10 speeds. With the introduction of the 9 speed cassettes 2:1 derailleurs had to be used due to the very close spacing of the cogs..."

--- SRAM's current "ESP" 7, 8, & 9-spd derailleur/shifter systems are 1:1 specific. ~ They will not shift well with Shimano units. ~ Their cassettes are compatible. ~ The ratios used has nothing to do with the spacings of 9 and 10-spd cogs.

"...The space between the cogs is the same for 5 and 6 speeds and then changes for each of the 7, 8, and 9/10 speed freewheels/cassettes... Pretty much any index shifter for the number of cogs on the freewheel or cassette that matches the number of indexed shifter will function fine...."

--- It is impossible to get a 7, 8, 9, or 10 speed Campagnolo shifter to shift correctly on a Shimano 7, 8, 9, or 10 spd cassette, and vice-versa. The cogs on their cassettes are spaced differently.
--- And, each of their 9 speed cassettes are also spaced differently than on their own 10 speed cassettes.

Sorry, about the digression, this is all totally off the track...

--- @¿@ --- I think that the fastest, easiest, cheapest way to get the bike back on the road would be to:
1.) Go to a Local Bike Shop and spend around $15-25 on perhaps a Shimano "Tourney" rear derailleur (which are solid workhorses, good for up to 7-speeds), or another basic traditional "top-normal" (not "rapid-rise") derailleur.
2.) A good time to replace the derailleur cable(s) and replace the rear cable housing with a modern "compressionless" (SIS-style) loop [all for just a few bucks anyway].
3.) Buy a new chain [$10-$15] (since the old one has probably stretched greatly during the past 25-30 years, anyway or was possibly damaged when the derailleur jammed). A worn chain will tend to slip gears on your freewheel.

Perhaps even consider a new freewheel [for maybe $20] - Shimano, Falcon and Sunrace all still make 5-spd, 14-28 tooth freewheels. They all work. But, Don't let the shop try to squeeze on a standard 6-speed freewheel just because they happen to have one. It will stick out too far over your axle.

If you still want to get indexed,... Shimano ALSO still makes CHEAP and INDEXED "Tourney" handlebar mounted thumb shifters [model TY-22 or TY-15] which you can clamp onto the tops of your handlebars... last time I ordered some (2005) they were under $15 for a pair. But, I suspect your LBS would no doubt have to order a set, since they really cater to newer components and replacements for more modern broken toys. You can always add something like these later.

Remember, if you do want MORE than 5-speeds, you will need a new (longer) rear axle... AND,... you will have to re-dish your wheel... AND,... you will then also need to re-space and align the rear of your frame from 120mm to at least 126mm. Your LBS will charge you insanely for any/all of this.

Dad's derailleur "exploded" on you because the chain jammed somewhere back there. Make sure any replacement has its limit screws adjusted properly. If so, the chain really shouldn't ever get thrown.

Also, have someone check the rear derailleur hanger and dropouts to be sure everything is straight so everything shifts smoothly together. If a derailleur hanger is not straight (parallel with the frame), you'll always have problems with shifting or a chain slipping gears. If the dropouts are not parallel to each other you can also have problems with your hub bearings and axle. These are very fast and very easy adjustments to make on a steel frame, but they can make a big difference. They both require simple but specific shop tools.

And, lastly, just make sure there are no excessively long bolts or nuts from a poorly mounted rear rack or fender getting in the way of the chain when it is shifting onto or off of the smallest cog. - Yes, I've seen someone jam up a brand new drive train because they had put on a rack and the chain got snagged by a long bolt poking just above the freewheel.

Good Luck. Those were very nice bikes. You should have little difficulty (or expense) getting everything spinning very smoothly once again.

infinityeye

rubbish!

Poguemahone

As you can no doubt tell by now, converting to indexing means converting the better part of your drivetrain. Although there is something to be said for indexing, that something does not include "cross-manufacturer compatability" and "upgrade/maintanence ease".

A nice, long cage suntour vx or vgt or whatever is prolly the simplest, most headache free solution, although as many have noted, most any derailleur should do-- as long as you keep your system friction.
For decent range, you want a long cage mech.

Stronglight's advice re: derailleur hanger alignment, derailleur limit screws, etc. is excellent and I really have nothing to add.

luker

wow. channeling Sydney, looks like. BTW, I have found that 10 speed shimano and 10 speed campy are very compatible, because their differences in spacing are just too tiny to cause a snafu. Must cause the shimano and campy camps much lost sleep, thinking how they are going to lose market share because they can no longer design in incompatibility...

stronglight

•¿•
–-– Hah! ~ That's great, and also very funny news. I'll bet there are already dozens of Japanese engineers scrambling to come up with an 11-speed cassette before the Italian opposition beats them to marketplace.

Center-to-center spacing on Campy 10-spd cogs is 4.12 mm. and Shimano's is 3.95 mm. I guess that with the ever diminishing gap between the two brands, as more and more cogs were squeezed into the same allottment of 130mm dropout spacing, it would be inevitable that the differences would eventually matter very little - given the blessedly simple century old technology of bicycles.

To review the score: Shimano released 8-spd in 1989... both had 9-spd in 1997... Campy lunged ahead releasing 10-spd in 2000 (beating Shimano by 4 years)... I wonder how long it will be before one or the other has 11 and then 12-spd cassettes perfected,... prehaps using parchment paper as spacers between the cogs.

It all reminds me of a gag in the satyrical 1984 movie "This is Spinal Tap" where the rock band guitarist selects one amplifier over another because the knob on one goes all the way up to "11", while the other brand's is only marked to "10".

cudak888 

No, they'll use standard spacers and cogs made out of parchment paper.

Then they'll proceed to charge 10 times the current (and ridiculous) price for individual cogs.

-Kurt

mazultav

Thanks everyone. It was the Suntour V-GT. I think Im just going to find a good replacement on ebay, set the limits right and learn to use the friction shifts. The thought of switching to indexed was mainly cause I thought the limits were set and was afraid of killing another derailer

n4zou

The next upgrade requiring you to purchase a new bicycle will be the CVT or Constantly Variable Transmission. One system is contained in a sealed hub and consists of two cones with a drive ball between them. Here is a link to this system.
https://www.varispeed.com/news.htm
The other system consists of a large disk and drive cone. This system is exposed to the elements and is unsuitable for MTB applications and must be kept very clean for proper operation. The only advantage with this system is its cost compared to the sealed hub system.
https://www.cvtsystems.com/gearphot.htm

n4zou

Yes, I am running SRAM grip shifts with an old Shimano SIS derailleur and Shimano 7-speed freewheel. All your doing is pulling the derailleur over a specific amount of travel for each cog of the freewheel or cassette. As long the shifter twist pulls the cable the correct amount to line the derailleur up with the cogs it must shift correctly. If you're having trouble then something is incorrect with your shift system. A common problem that can effect the shifting greatly is cable drag due to excessive friction. Pull your cable casing off and look at the cut ends. More likely than not there is a small bur that is dragging on the cable that needs to be removed. I use a very small blade on my multi-tool pocketknife used to punch holes in leather and other materials to remove that bur. Proper dressing of cable casing is a must that no one does and causes so many shifting problems. You must also cut the casing the proper length between the shifter and derailleur where casing is required. Too long can be just as bad as too short! Worn out or dry (dried up lube) index shifters also cause problems. Grip and thumb shifters must be lubricated at least once a year. You can test your shifting system by removing the chain and putting a dial indicator on the derailleur. This allows you to measure the derailleur travel for each click of the shifter which should equal the spacing of the cogs on the freewheel or cassette. This can be done on a workbench if you just want to test a shifter and derailleur before you go to the trouble of installing the parts on a frame. If you know how to use a dial indicator then you also know how to set it up! It's nothing more than a simple pantograph after all.