Modifying gears

[rgsupergrover]

I had a thought the other day about some custom gears.

Would I be able to change my 8 spd rear to a 3?
I am pretty sure that it would just be a matter of adjusting the cams so that on the the first/last 3 gears work on my shifter.

Has anyone ever tried this before?


Moreover, has anyone ever chucked gears on a suburban? Or is that a bit kosher....


Cheers.

 

[Live2DieTrying]

They come with a derailleur mount, so why not.
It should be pretty easy. Buy or make some spacers to replace the gears you remove, and adjust the high and low screws on your derailleur

 

[timhill]

you could use a 3 speed front derailleur shifter if you don't mind changing gears with your left hand.

 

[mtbforever]

you could use a 3 speed front derailleur shifter if you don't mind changing gears with your left hand.

Doubt that would work as the front derailleur pulls through more cable than the rear derailleur as the gears are closer spaced together at the rear than the 3 front chainrings....well thats what i would imagine anyways...bit of trial and error wouldnt go down badly...

Just play around and see what you work out...

A bit like this set up...Jared Graves bike of coarse...

 

[RYDA]

PM Burrito Boy...

OR

Look at his PYR thread...

http://www.rotorburn.com/forums/showthread.php?t=189835

 

[wombat]

you could use a 3 speed front derailleur shifter if you don't mind changing gears with your left hand.

Nah, mtbforever is right, that's not going to work, indexing is pretty wrong

As mentioned, best bet is to set up the derailluer so it'll only reach the 3 sprockets you have/want. Might need to find some longer screws to use for the limit stops, but that'd be about it.

 

[rgsupergrover]

Thanks for all the input guys! Would it help at all with reducing my gears going out of tune?

And I flicked burrito boy a pm.

he has a sick stp!

 

[Reubs]

So i was thinking about this after initially reading the thread the other day....
Here's how i would do it-

Put the 3 cogs you want so they are as far inward as possible (ie 1st 2nd & 3rd gear) and fill in the rest of the cassette with plastic spacers. Now using an 8 speed shifter, put it in 6th gear and conect the cable up as usual. This will mean you are now using positions 6,7 & 8 on the shifter as your gears. By reaching the last available gear on your shifter, the rear derailier will not be able to move past the 3 gears you have installed (the setscrew will not go in that far so the shifter needs to stop it instead.) and then you use the other setscrew to stop it shifting into the spokes. Since (in that position) the derailier would be pulling against the setscrew, to shift futher it will feel like an end stop. You could essentially do this with any number of gears on any shifter.

Now you will have 3 gears without any slop, cable slack or "no gear" positions on the shifter.

 

[mtbforever]

So i was thinking about this after initially reading the thread the other day....
Here's how i would do it-

Put the 3 cogs you want so they are as far inward as possible (ie 1st 2nd & 3rd gear) and fill in the rest of the cassette with plastic spacers. Now using an 8 speed shifter, put it in 6th gear and conect the cable up as usual. This will mean you are now using positions 6,7 & 8 on the shifter as your gears. By reaching the last available gear on your shifter, the rear derailier will not be able to move past the 3 gears you have installed (the setscrew will not go in that far so the shifter needs to stop it instead.) and then you use the other setscrew to stop it shifting into the spokes. Since (in that position) the derailier would be pulling against the setscrew, to shift futher it will feel like an end stop. You could essentially do this with any number of gears on any shifter.

Now you will have 3 gears without any slop, cable slack or "no gear" positions on the shifter.

That all sounds well and good... but you didn't consider chain-line...???

frames vary... so what your saying to do, by running the gears in the 6, 7, 8th gearing the chain-line might not necessarily be straight therefore meaning the shifting quality may still be poor... and I'm sure the last thing you want to be doing out of the gates is snap your chain or slip through gears...

It wouldn't matter where you put the 3 cogs (or however many) on the rear, you just have to adjust the limit screws so that the chain cannot jump off the 1st or last gear of the 3 cogs (or however many) on the bike...

It takes a fair bit of time, in taking the wheel off and on to get the perfect chain-line with spacing the cogs right but the difference between a bad chain-line and straight one is noticeable...

My 2 cents anyway

 

[Reubs]

No, the gears are in positions 1,2 & 3 not 6, 7 & 8(thats what the shifter will display)

i dont think chainline is that much of an issue but no i'd not considered it. Given that Supergrover is currently running single speed I would assume that the chainring is in the middle position on his cranks or close to it (if they are bmx style). It would be possible to set this whole thing up in reverse (cogs closest to frame and shifter using 1,2,3) but that would be less asthetically pleasing (it would look gay) but may solve chainline issues if the chainring sat further outboard.

I dont like the idea of just using limit screws as this still allows the shifter to have positions that are useless (ie you shift and there is no result) and this is more likely to fuck you up

Oh, RGsupergrover, you do realise that you will have to run something up front (chainguide or front der.) to keep the chain on. even with a dead straight chainline you will lose the chain at some point.

 

[wombat]

i dont think chainline is that much of an issue but no i'd not considered it.

What's the point of using limited sprockets if you're not going to tune your chainline?

Seriously, set the sprockets where they're going to give you the best chainline, limit the derailluer's throw with the limt screws (get longer ones if you have to), and tune the shifter to function there using whichever positions you want (6-7-8 probably isn't a bad choice). It's all pretty simple stuff.

 

[t]

I had a sponsored athlete who tried this last season, the problem with running the cogs at the back and spacers in front is that the top jockey wheel ends up so far away that the shifting is really laggy.

this B-tension issue totally trumps any chain line issues your gonna get.

we switched his around, put the spacers on first, then the 5 small cogs and then a lock ring. to set the cable tension, you click the shifter through 4 clicks in this case, then set the cable. the shifter runs out of clicks on the biggest cog so you can't over shift onto the spacers (unless you bend the derailleur)

 

[rgsupergrover]

Cool! Thanks a lot for the help. I will be running a guide on the front. Or I might just go single

 

[philw86]

*snip*

I had a sponsored athlete who tried this last season, the problem with running the cogs at the back and spacers in front is that the top jockey wheel ends up so far away that the shifting is really laggy.

this B-tension issue totally trumps any chain line issues your gonna get.

we switched his around, put the spacers on first, then the 5 small cogs and then a lock ring. to set the cable tension, you click the shifter through 4 clicks in this case, then set the cable. the shifter runs out of clicks on the biggest cog so you can't over shift onto the spacers (unless you bend the derailleur)

Chainline is measured at the 4th smallest cog in the back (usually). With most DH/FR/etc style riding, you don't use the lowest 2 gears unless you climb.

For my slopestyle/4x/dual rig, I removed the largest 3 cogs in the back (weight savings = 187g off a cheap steel MTB cassette). Use cassette spacers like Graves did, and use an M4x20mm socket head cap screw for a limiter.

As mentioned above, this will keep your derailleur functioning almost exactly the same, and your shifter will stop before hopping the derailleur onto the spacers. The derailleur also now has nearly no chance of getting jammed into your spokes.

Graves is a powerhouse; drivetrain parts can't last very long with the way he muscles around.

cheers,
philip