swampyankee2 

Looking at my options for upgrading the much-derided Simplex plastic derailleur on my 70's Dawes. I'm looking into the vintage derailleur market and I find them advertised as "long cage" "short cage", and even "medium cage". I would assume this refers to the derailleur's range of motion, the short cage spanning fewer gears. Being as my bike is a 10 speeder with only 5 cogs to shift across, a short or medium cage design should suffice. Or is the cage size a more modern thing and any derailleur made in the bike boom era ('70's-early '80's) suffice?

Sierra

I think it more refers to how much excess chain it can wrap.
The wider your gearing range, the more you will need to wrap.

Retoocs

Cage size determines the derailleur's capacity. The capacity is the difference in the number of teeth of the big and small chainrings + the difference in the number of teeth of the big and small cog of the freewheel/cassette.

Long cage have more capacity than short cage.

ollo_ollo

j.e. 34tooth biggest freewheel cog = Long Cage

swampyankee2 

Ah yes, that makes sense. In my velo-illiteracy I thought cage was refering to the parallelogram-thing which would allow more movement across a larger cassette. But a "long" cage would be able to take up more slack in the chain when going from largest to smallest sprockets.

So a measely 10 speed would not need alot of range and a sort cage derailleur should suffice.

nlerner

It's not a matter of speeds or number of cogs, but the size of the largest cog. The longer the cage, generally, the better to deal with large (30-teeth on up) first cogs. That's why touring bikes and other stump pullers have long-cage RDs along with "mega-range" freewheels or cassettes.

Pompiere

Long, medium, or short refers to the amount of chain the derailleur can take up. You take the difference between the largest and smallest cogs on the freewheel and add it to the difference between the chainwheels to get the total capacity. For a common 14-28 freewheel (14 teeth) and 52-42 crankset (10 teeth), the minimum capacity is 24 teeth. A longer cage is needed when you have a triple crank with a small granny gear because the difference between large and small jumps to 20-30 teeth. Not enough capacity will allow the chain to hang loose in certain gear combinations and risk dropping off.

Velobase is a large database that has specs for almost any derailleur you may want to use. https://velobase.com/Default.aspx

dedhed

Before deciding on derailleur, decide on what you want to accomplish with gearing.
Generally base that on intended use of the bike, what terrain you frequent, what is compatible with the frame design, and what your body can handle.

verktyg 

swampyankee2 Short, Medium and Long refers to the cage length and the amount of chain the derailleur can wrap.

Classic 1970s - early 80's "published" derailleur capacities:
Short cage derailleurs can usually only work with a 24T to 26T large sprocket - for example Suntour V and Cyclone RDs, Campagnolo R/NR/SR/GS 26T+ (think racing)
Medium cage can usually handle up to 30T - Simplex Prestige and Criterium were rated at 28T but will handle 30T+ Suntour VT 30T, Shimano Crane and later models 30T
Long cage - also called long arm, up to 34T - Suntour GT, Shimano GT and so on (think touring and MTB)

Your 70's Dawes most likely came with "Alpine" gearing: 5 speed 14-28T freewheel with 52T-36T/40T/42T chainrings.

You probably don't need a long arm RD unless you want to use a 32T-34T freewheel. There are lots of options.

Many indexable derailleurs from the mid 80's on have a floating upper pulley that allow the chain to self center on the sprockets which makes shifting easier, especially with the later bushingless chains that have a lot of lateral side to side flex. Those Rds work great with standard non-indexing friction shifters.

If your Dawes still has the plastic Simplex shift levers, replace those too.

BTW, contrary the opinions of some forum member's who like to try and spend other people's money, you don't need a fancy wiz-bang RD to have fun on your bike. Good used RDs are plentiful and can be cheap. Make sure all of the moving parts - pivots and parallelogram - are not loose and worn out and the pulleys don't wobble.

verktyg

bamboobike4

I concur with the initial need to determine your riding needs.
I also concur with getting your gearing in place first.
I also concur with:
.... finding an RD to do what your gearing needs
.... after you get gearing to do what your riding needs.

There are lots and lots and lots and lots of RD's out there.
If you're running 2x5, tons of RD's will work for you.
You are just pulling cable, after all.
They do what they're told.

No need for a bigger boat.

CliffordK

Just put on your 52/42 chainrings and 14/21 freewheel, and don't worry about the derailleur cage length.

The Golden Boy 

It's a touch more complicated than "34 tooth cog means long cage." Independent of chain wrap- some derailleurs pair up with different derailleur hangers/dropouts to allow larger cogs. As anyone who's had a cog grinding on a jockey pulley will tell you.

There's also the size of your front chainrings- which also adds into how much chain the cage is going to need to take up.

But, cutting to chase- Get yourself a Suntour V-GT Luxe for your Dawes. The greatest all purpose friction derailleur ever. Shifts excellent. Bulletproof. Relatively lightweight. Excellent range. Done.


Suntour V-GT Luxe by Dave The Golden Boy, on Flickr

squirtdad

just to note short, medium, long are not precise terms like understood by all like british BB vs Italian BB.

swampyankee2 

I'm looking at a set of Huret Challenger derailleurs. My go-to for info is Disraeli Gears, which seem to have a good opinion of the Challenger range (which says alot since he seems to be pretty critical). Any opinions here about these? Remember, I'm upgrading from Simplex Prestige plastic so I can only go up from there.

SurferRosa

Pretty simple: the further apart the pulley wheels on a rear derailleur, the longer the cage that holds them.

swampyankee2 

Thanx, I believe I understand the diff now. I was looking for an opinion as far as the Huret Challenger in particular. Maybe I should've started another thread

philbob57

I haven't looked for rear ders for a couple of years, but when I was looking, I saw a lot of Suntours and virtually no Hurets. Besides, even in France, Suntours may be cheaper than Huret Challengers. BTW, my V-GT and Cyclone GT (1st gen) both handled 7 speed freewheels with ease.

John E

SunTour rear derailleurs are the best. The only reason I have Campags. on the Capos and the Bianchi is for brand correctness.

bamboobike4

I just got this.

SurferRosa

Road Fan

There are two criteria. The size of the largest cog is part of what drives the length of cage. An additional criterion is the chainwrap capability, which depends (as has been said) on the difference between the largest and smallest chainrings and between the largest and smallest rear sprockets. These two numbers are added together. For example, with a 52/42 and 14/28, the chain wrap requirement is 10 + 14 = 24 teeth. This is in the range of many short-cage rear derailleurs, but a medium-cage is not wrong. If you had a 14/34 megarange in the rear, you would have wrap of 10+20 = 30 teeth wrap and a maximum cog of 34, but the 34 may need a longer derailleur hanger to clear the big sprocket. Shimano had some rear derailleurs which were matched to those freewheels when they came out.

martl

It is less the size of the largest cog, but the Delta in "required chain length" between the combination largest rear - largest front and smallest rear - smallest front. The first job of the cage is to take up the slack in the chain, a longer cage can take more. if one hypothetically used a back 34-32-30-29-28-27-26-25-24-23 or such which doesnt exist, one could use a very shortt cage, but would need a longer parallelogram part.

When one pays attention not to use the extremest positions, one can get always away with a smaller cage. People who learned to ride in the era of unforgiving chains in 2x5 drivetrains naturally avoid these, I rode a Chorus triple crankset on a short record RD and it worked fine for years.

jdawginsc 

Find out what you want in gearing...are you using the same rear wheel the bike came with? What is the range of freewheel teeth. Most older touring/sport bikes came with 14-28 freewheel, and a 52-42 (or 40) crank/chainrings. If you are keeping a double up front, any rear derailleur will do...even short cage. Add a triple and it becomes tricker.

As for Huret Challenger, they were decently well regarded as bullet-proof, but I have never seen one in action.

Some folks swear by Huret, other swear at them.

JohnDThompson 

The Challenger is a decent derailleur. Much sturdier than the plastic Prestige. The pulley cage has two mounting options: one for 24T or smaller cluster, the other for 28T cluster. If you need a larger cluster than that, look for a Duopar derailleur.

N.B. the Success is essentially the same as the Challenger, but using titanium.

swampyankee2 

Thanx for the comments. I don't plan to change any gearing on this bike. Certainly not the cassette, and I was hoping to keep the 52-42 sizes even if I convert to cotterless. This will be a vintage tourer. If I need more versatility for terrain I can always ride one of my newer bikes.