Advice on rear derailleur repair/replacement

[neilbags]

I picked up an old road bike which seems to run well except a piece is broken off the rear derailleur. Im not sure what the part is called, but it goes over one of the cogs and holds the chain on. Without it the chain falls off right away.

I want to fix it on a budget but I'm not sure I will be able to find a replacement part. I'm happy to buy a new (budget) derailleur but I'm not sure how to figure out what would be compatible. Any advice on this would be greatly appreciated.

The first photo shows the derailleur - Shimano RS. The second photo shows the broken/missing part. Thanks in advance.

[P!N20]

Looks like your missing a jockey wheel and the cage is mangled. I reckon your best bet is to source a replacement derailleur. Online trading sites are your best bet or post an ad in the 'wanted to buy' section of this forum's marketplace - if/when you have access.

A quick ebay search turned up this: https://www.ebay.com.au/itm/Shimano-RS- ... SwQcJaCbEQ

[neilbags]

Can I fit a new cheap derailleur instead of a replacement vintage one?

[10speedsemiracer]

Can I fit a new cheap derailleur instead of a replacement vintage one?

Yep, just make sure to get one with an integral derailleur hanger, like this :



This one is $10 at Pushys https://www.pushys.com.au/sunrace-m2t-6 ... lleur.html, but maybe someone here will have something lying around in their parts box, or even your local bike shop may have something floating around in the back (very possible). I'm fairly sure I have a 1970s Shimano Eagle II with hanger somewhere, will do 5/6sp friction.

[neilbags]

Thanks!

I suspected as much but I wanted someone to say it before I wasted my money! I've got to order a bottom bracket for my partners bike anyway so I might just tack on a derailleur as well. I was looking at this before - the one you posted is from the mountain bike range - is there much of a difference? Also wondering about shortcage/longcage - i'm guessing short is ok because its only 5 speed?

Thanks for the education

[10speedsemiracer]

Was just an example, they also have a Shimano Tourney with hanger (I think $15 or $16) which may be more applicable

[neilbags]

hi, so do you know if either of these will work or not?

i understand that i need one with a hanger, but what else do i need to take into consideration?

[twowheels]

Thanks!

I suspected as much but I wanted someone to say it before I wasted my money! I've got to order a bottom bracket for my partners bike anyway so I might just tack on a derailleur as well. I was looking at this before - the one you posted is from the mountain bike range - is there much of a difference? Also wondering about shortcage/longcage - i'm guessing short is ok because its only 5 speed?

Thanks for the education

Re short/longcage. This isn't to do with number of gears. Longcage req'd if largest sprocket goes past a certain number of teeth/diameter, thus to clear the teeth of the gear.
Better explanation here https://www.mountainbikesdirect.com.au/ ... ge-length/

[neilbags]

Re short/longcage. This isn't to do with number of gears. Longcage req'd if largest sprocket goes past a certain number of teeth/diameter, thus to clear the teeth of the gear.

Gotcha. From what i've been reading, it seems that a mountain bike derailleur should be fine on a road bike with shifters this old, because differences in pull ratios only came in more recently. Does that sound right?

[AUbicycles]

(I began writing, there there was a series of followups)

It is not really a hanger as such as it attached directly onto the axle. Nice info from twowheels... generally the derailleurs should be fairly interchangeable.

To get it on and the chain threaded, you can break the chain (so would need a chain breaker) but a far easier approach is to actually unscrew the bolts on the cage (of the new derailleur) and thread the chain through then rescrew on the cage. So you don't actually have to buy a chainbreaker.

Apart from that, I highly recommend a solid clean of the chain and cassette up back and chainring up front. Degradable (enviromentally friendly) degreaser and a bit of scrubbing. When it is nice a clean, some lube.

To setup the derailleur, you will need to set the limit screws (to align the max and min with the inner and outer cogs) and adjust the cable tension to get the shifting just right... there is plenty of info on the net for that.

[neilbags]

(I began writing, there there was a series of followups)

It is not really a hanger as such as it attached directly onto the axle. Nice info from twowheels... generally the derailleurs should be fairly interchangeable.

To get it on and the chain threaded, you can break the chain (so would need a chain breaker) but a far easier approach is to actually unscrew the bolts on the cage (of the new derailleur) and thread the chain through then rescrew on the cage. So you don't actually have to buy a chainbreaker.

Apart from that, I highly recommend a solid clean of the chain and cassette up back and chainring up front. Degradable (enviromentally friendly) degreaser and a bit of scrubbing. When it is nice a clean, some lube.

To setup the derailleur, you will need to set the limit screws (to align the max and min with the inner and outer cogs) and adjust the cable tension to get the shifting just right... there is plenty of info on the net for that.

Thanks for the solid reply! I'll definitely be giving it a good scrub and re-grease. And i've adjusted limit screws before, so thats all good. Really just wondering about the compatibility of rear derailleurs because i dont want to spend too much on this bike

[bychosis]

Keep it on a budget. That style of derailleur (axle mount) is indicative of a low end bike. Of course, probably perfectly serivicable, but nothing special.

[find_bruce]

5 speed rear means pre-indexing, so pretty much any 5, 6 7 or 8 speed shimano or similar derailleur will work just fine.

If you stick with axle mount you will pretty much guarantee both cheap and compatible.

Whereabouts are you ? As 10speedsemiracer said, plenty of us will have something suitable hanging around waiting to find a new use.

[neilbags]

Pottsville NSW

Happy to pay shipping as well or drive a little way. But as I said I've gotta order something anyway so it's not a big deal to buy a cheap one as long as it's going to work.

[10speedsemiracer]

It may be a really good idea to investigate whether there is a cycle co-op anywhere near you, somewhere you can take the bike, have access to all sorts of parts and tools, and maybe fix it there with support if required. There are one or two here in Melb that do this, notably an excellent establishment in Port Melb, but I don't know anything about Sydney.

If I were closer, I'd offer to come over and fit the Shimano unit that I have, and wrench on the bike with you, but is a bit of a drive...sorry

[neilbags]

It may be a really good idea to investigate whether there is a cycle co-op anywhere near you

yeah i used to go to one all the time when i lived in sydney. i dont there is any around here but maybe ill look harder!

[Duck!]

Thanks!

I suspected as much but I wanted someone to say it before I wasted my money! I've got to order a bottom bracket for my partners bike anyway so I might just tack on a derailleur as well. I was looking at this before - the one you posted is from the mountain bike range - is there much of a difference? Also wondering about shortcage/longcage - i'm guessing short is ok because its only 5 speed?

Thanks for the education

Re short/longcage. This isn't to do with number of gears. Longcage req'd if largest sprocket goes past a certain number of teeth/diameter, thus to clear the teeth of the gear.
Better explanation here https://www.mountainbikesdirect.com.au/ ... ge-length/

INCORRECT!!.Cage length has more to do with the number of chainrings than anything else. More rings need more chain to cover the range, more chain needs more derailleur to take up the slack. Large sprocket clearance is determined by the geometry of the main body of the derailleur.

MTB derailleurs have a longer main body to cover bigger cassettes, and a longer cage to work with triple-ring cranks. Although newer models have grown to suit bigger cassettes, many will simply not fit under anything larger than a 28-tooth sprocket, even in long form; the long cage enables the extra chain length needed for a triple.

[twowheels]

Thanks!

I suspected as much but I wanted someone to say it before I wasted my money! I've got to order a bottom bracket for my partners bike anyway so I might just tack on a derailleur as well. I was looking at this before - the one you posted is from the mountain bike range - is there much of a difference? Also wondering about shortcage/longcage - i'm guessing short is ok because its only 5 speed?

Thanks for the education

Re short/longcage. This isn't to do with number of gears. Longcage req'd if largest sprocket goes past a certain number of teeth/diameter, thus to clear the teeth of the gear.
Better explanation here https://www.mountainbikesdirect.com.au/ ... ge-length/

INCORRECT!!.Cage length has more to do with the number of chainrings than anything else. More rings need more chain to cover the range, more chain needs more derailleur to take up the slack. Large sprocket clearance is determined by the geometry of the main body of the derailleur.

MTB derailleurs have a longer main body to cover bigger cassettes, and a longer cage to work with triple-ring cranks. Although newer models have grown to suit bigger cassettes, many will simply not fit under anything larger than a 28-tooth sprocket, even in long form; the long cage enables the extra chain length needed for a triple.

Do u mean mtb direct info is incorrect? I did say their info had more detail, which does cover chainrings.

[neilbags]

[
INCORRECT!!.Cage length has more to do with the number of chainrings than anything else. More rings need more chain to cover the range, more chain needs more derailleur to take up the slack. Large sprocket clearance is determined by the geometry of the main body of the derailleur.

MTB derailleurs have a longer main body to cover bigger cassettes, and a longer cage to work with triple-ring cranks. Although newer models have grown to suit bigger cassettes, many will simply not fit under anything larger than a 28-tooth sprocket, even in long form; the long cage enables the extra chain length needed for a triple.

Thanks for the clarification. In your opinion would a cheap hanger-mount MTB derailleur work for this bike? Its only 5-speed.

[bychosis]

Do you have council clean-up in your area? Wouldn't take long to find a replacement if you did. Just about every dept store BSO will have one. Alternatively, you might even find a local 2nd hand junker for $0-20 on Gumtree that'll have a suitable derailleur.

[Duck!]

Re short/longcage. This isn't to do with number of gears. Longcage req'd if largest sprocket goes past a certain number of teeth/diameter, thus to clear the teeth of the gear.
Better explanation here https://www.mountainbikesdirect.com.au/ ... ge-length/

INCORRECT!!.Cage length has more to do with the number of chainrings than anything else. More rings need more chain to cover the range, more chain needs more derailleur to take up the slack. Large sprocket clearance is determined by the geometry of the main body of the derailleur.

MTB derailleurs have a longer main body to cover bigger cassettes, and a longer cage to work with triple-ring cranks. Although newer models have grown to suit bigger cassettes, many will simply not fit under anything larger than a 28-tooth sprocket, even in long form; the long cage enables the extra chain length needed for a triple.

Do u mean mtb direct info is incorrect? I did say their info had more detail, which does cover chainrings.

The article completely ignores the critical factor of derailleur body geometry being the limiting factor regarding sprocket size. It's also wrong on a couple of minor points too.

Cage length dictates the overall gear range that can be accommodated, both chainrings and cassette, within the confines of the largest sprocket that the derailleur can handle. If a short cage model won't fit under a partricular sprocket size, the long version of that model won't either, but will enable an increase in gear range either by the addition of a third chainring, or a wider-spaced double set. When getting to the modern huge-range cassettes, increasing the front gear range from 1x to 2x, or 2x to 3x dictates a reduction in cassette size in order to remain within the total capacity of the derailleur, sometimes despite increasing the cage length.

[Duck!]

[
INCORRECT!!.Cage length has more to do with the number of chainrings than anything else. More rings need more chain to cover the range, more chain needs more derailleur to take up the slack. Large sprocket clearance is determined by the geometry of the main body of the derailleur.

MTB derailleurs have a longer main body to cover bigger cassettes, and a longer cage to work with triple-ring cranks. Although newer models have grown to suit bigger cassettes, many will simply not fit under anything larger than a 28-tooth sprocket, even in long form; the long cage enables the extra chain length needed for a triple.

Thanks for the clarification. In your opinion would a cheap hanger-mount MTB derailleur work for this bike? Its only 5-speed.

Yes, one of those will work.