Very stupid question

[Arch]

This is probably a very stupid question, but I've nobly decided to post it here rather then PM someone who won't laugh at me, at least not to my face.

I'm going to need a new rear mech for my Galaxy rebuild. I've looked on Wiggle and CRC, just browsing, and all the mechs seem to say 9 or 10 or 11 speed, (or not specify). Mine's a 7 spd and I haven't seen any that specified 7. Is the 9 or 10 etc a maximum, or specific? How wrong could I get it?

Also, for some of them, HOW MUCH!!!!!

 

[gavintc]

I am no expert, but using my simple mechanical brain, it should work. A rear mech has no understanding of how much it should move each time it receives message from the STI/Ergo. Therefore it will move in accordance with the pull it receives and will move correctly for 7 (or more) cassettes. I 'think' the only thing you need to consider is long or short cage. but, I am sure an expert on these matters will be along soon enough.

 

[Black Sheep]

firstly, I could be wrong.

I believe that 9 and 10 speed chains are narrower than 7 speed chains and so you may not be able to run a 7 speed chain through them.

my wife's bike runs a 7 speed cassette with an 8 speed mech lined up so that the 8th speed of the mech lines up with the 7th cog of the cassette. this stops it having a redundant position on the shifter.

hope this helps.

forgot to say, i've used a 9 speed mountain bike mech on a 5 speed on my road bike for the past two years

 

[phil_hg_uk]

And what about Medium Cage, Long Cage and Wide Link options what are these ?

 

[Arch]

And what about Medium Cage, Long Cage and Wide Link options what are these ?

Yes, any advice would be welcome.

I can just look at what I used to have and try to match that, of course.

It's probably good for me to have to work all this out, the trouble is when you've had people who enjoyed doing it all for you, and then you don't any more, you realise how little you know.

Good point about the chain width, I hadn't thought of that.

 

[gavintc]

And what about Medium Cage, Long Cage and Wide Link options what are these ?

The cage descriptions describes the distance that the 2 jockey wheels are separated by a 'cage'. On a triple, you need a long cage. If the cassette has a large sprocket, you may need a medium cassette and for compacts/doubles with normal road cassettes you can use a short cage.

Wide link - ? don't know that one.

 

[GrasB]

iirc you need a one that's specced for 8 speed. To this end you may well better off looking at the MTB rear Deraileur section. Something along the lines of the Acera. You'll probably be looking at the lower end parts as most parts are 9 or 10 speed now.

 

[Arch]

iirc you need a one that's specced for 8 speed. To this end you may well better off looking at the MTB rear Deraileur section. Something along the lines of the Acera. You'll probably be looking at the lower end parts as most parts are 9 or 10 speed now.

oh, thanks for that, and not too pricey. It's a triple, so I'll need long cage then.

Spanner in the works - any reason why that one linked to won't work with a 7spd twist grip shifter? (I'm trying some different bar ideas) (you see, I really am a bear of very little brain about all this, thank you for being gentle with me)

 

[ChrisKH]

Try not to use components with different speeds together if you can help it. I've had no end of trouble with a nine speed shifter with eight speed components for example. Everyone says it should work which it does. Intermittently. Now looking for a new shifter.

I would also like to congratulate you on the use of the word 'nobly' which could have been misinterpreted but was carried off with some aplomb.

 

[peanut]

what is the number of teeth on your largest cassette sprocket Arch ? if it is 27 or less a short cage will suffice 28+ will generally require a medium cage. Most rear mechs will be rated for the max recommended sprocket size it will cope with,

A 9 speed rear mech will cope well enough with an 8 speed chain I used a Campag 9 speed Mirage front and rear mech with 8 speed chain and cassette for years without problem.

If you tell us the size of your sprockets we'll hunt down a bargain rear mech for you

 

[phil_hg_uk]

I am thinking of upgrading my front and rear mechs as my rear is a Deore and the front is a Tiagra and I want all 105 as the Brake Levers/ Gear Changers and front chain wheel is a 105.

Anyway I was just lookin on CRC and they have a 105 long cage rear mech for £30.00 less than half price here -> http://www.chainreactioncycles.com/Models.aspx?ModelID=13595 dont know if it would suit yours arch

 

[Arch]

what is the number of teeth on your largest cassette sprocket Arch ? if it is 27 or less a short cage will suffice 28+ will generally require a medium cage. Most rear mechs will be rated for the max recommended sprocket size it will cope with,

A 9 speed rear mech will cope well enough with an 8 speed chain I used a Campag 9 speed Mirage front and rear mech with 8 speed chain and cassette for years without problem.

If you tell us the size of your sprockets we'll hunt down a bargain rear mech for you

Thank you! I'll have to go home and write down all the details and throw myself on the forum's mercy next week. I'm fairly confident I can fit the damn stuff, it's just knowing what to buy!

Stand by for similar howlers about cantilever brakes soon.

Chris: I regret to admit, I had to spellcheck nobly, I typed nobley to start with.... I appreciate the advice about matching stuff, the trouble is I learned most of what I know (or more likely, what I've forgotten) from someone who revelled in getting mismatches to work out, so I always have this nagging idea that it ought to be ok, somehow.

 

[Arch]

No, hang on. I made a note of the cassette in my diary a while back for some reason.

It's 13-30, does that sound right? I don't know what the triple will be, I've been offered a freebie and can't remember the details.

 

[swee'pea99]

As a general point, rear mechs are one of the things you can often get off ebay for a good price - the bling boys go for an upgrade, after barely using the perfectly good stock unit that came with their new £600 bike. (Or you can go for something like an old 600 series - excellent units that last for ever, and you can pick them up for a fiver.) Do make sure you google any candidates tho' - there are duds out there.

 

[peanut]

I would always recommend buying a brand new rear mech . The trouble with used is that so many rear mechs get bent or bashed or pulled out of alignment by crashes or shipping the chain or just careless storing of bikes in sheds and against railings etc.
precise alignment of the rear mech is so critical to smooth changes and proper operation I would say that its simply not worth the risk buying used.

You cannot tell if a mech is bent even when fitted unless its a gross misalignment