from 9 down to 7 sprockets

[Xiorell]

The bike I am working on, has 9 sprockets. It's pretty clear from what I can tell, it isn't supposed to -

The shifters stop at 6
the front mech is ooooooold
the rear mech is just as old

However the wheel takes the 9speed cassette fine (alexrims MX18s)
It looks to me like someone just lobbed a 9spd cassette on there with no thought as to the rest of the drivetrain.



I took of the cassette today, the smallest 2 sprockets just fall away. They do fit on the rest of the cassette they just don't seem as "stuck together" as the other 7.



Can I just NOT put these two small sprockets back on? Rather than buy a load of crap to propperly convert to 27spd? I don't need all those gears anyway, 21spd would be fine for what I am doing.

Is it OK to do this and will I need a spacer of sorts to fill in the gap on the wheel where they used to be?



(I can always buy 27speed stuff later if I want)

 

[Zoiders]

You can stick a 7 speed cassette on, just add a spacer behind it.

You can't strip the 9 down to 7 as it won't index properly, you would still have to space it anyway.

My concern would be who you got the bike off and where it came from, chop shop bikes fill me with unease.

 

[Xiorell]

Hmmm



What are the chances of the old stuff working for 9spd?

Also, incase I DO use the 9spd cassette, could anyone point me to basic mechs that are up to the job? (cheap, this is a cheap project! lol)

 

[RecordAceFromNew]

Xiorell I hear you saying the mechs are old, but the question is how old, which model etc?

Most Shimano rear mechs that are old still have the same cable pull ratio as their 9 speed rear mechs today. The only significant ones that were different were the Dura Ace prior to 1997, but they are pretty rare. This has the relevant table - chance is yours is within the white boxes.

Assuming its compatibility is within the white box, no matter what Shimano might say I am pretty sure it will index properly with a modern 9 speed chain, 9 speed cassette and 9 speed shifter. Comparing a cheap Shimano 5/6 speed Tourney and a 9 speed XTR rear mech recently I saw no reason why they wouldn't be totally interchangeable in practice.

Although you did not specifically say so I presume your rear shifter is 6 speed indexed, but since you did not provide details it is impossible to tell whether it is capable of friction shifting (some downtube and thumb shifters have a switch for that). The reason I am mentioning this is with a friction shifter you can successfully shift pretty much any speed with any rear mech at the back.

Assuming your 6 speed shifter is indexed only, the trouble of having 7, 8 or 9 speeds or cogs at the back is they will not index properly with that shifter, the reason is the 6 speed shifter (in conjunction with a "common" Shimano rear mech) is most likely to require a rear cog spacing of 5.5mm at the back to index, and no cassette or freewheel above 6 speed will have that. Since you said you want cheap (why not?), if the 9 speed wheel/cassette is fine, or even if you wish to change the cassette to something else in the future, the cheapest shifting solution is to change the rear shifter to a friction one. Something like this, for the princely sum of £5.99 incl p&p, is imho hard to beat, and it is as future/change proof as can be.

Although cheap, similar Sunrace shifters are recommended by the knowledgeable folks at Rivendell.

Good luck!

 

[Zoiders]

A cheap original old 5/6 speed tourney mechs (and I mean old) wont run on 9 speed, they wont run with 8 either in a lot of cases.

It's not so much sprocket compatibly or even capacity but the fact they just don't swing far enough at the knuckle to reach the very largest sprocket of the 8/9 speed cassette.

 

[Xiorell]

Cheers for that, Record, I'll have a look what I've got at home when I get in.

Youy're correct about the shifters, 6spd ones, I think they are SRAM but can't remember right now. They need replacing anyway, knackered.

 

[Xiorell]

here we go, this is what the mechs look like. These are not the mechs that came off the bike (which is finally stripped ready for paint tomorrow) but pretty similar



The rear is more or less like this

And the front alot like this, but not an Ultegra

I'm assuming these aint gonna do 27gears? I seem to remember having mechs like these when I was a kid on an old MTB

 

[RecordAceFromNew]

As I mentioned before, chance is good that the old rear mech will index successfully, especially if it is a Shimano unit. If it doesn't for whatever reason, since you said you want to spend very little, this is a good replacement* for the money that should have no problem indexing 5, 6, 7, 8 or 9 speed at the back, and for pretty much any tooth range cassette money can buy.

Regarding the front mech, if a replacement is needed for whatever reason, the choice will be dependent on a) whether it is indexed or intend to be indexed and if so whether it is a mtb or road set up - they require different cable pull - the shifter's make/model may give a clue, and b) how the mech is fixed on the seat tube, via brazed on or clamped, and if clamped what size is the seat tube outside diameter.

* worth checking whether you need a version that needs a hanger or not