mainstreetexile 

I've heard that people have had good results running 7 speeds with the shimano 6 speed thumbies.

Anybody have any advice on this setup? Do you adjust it to put the "extra" gear at the low or high end?

I'm specifically interested in the Deore SL-MT60 thumbies with a Deore RD-MT60 rear derailleur, but I'm guessing other shimano 6 speed shifters are the same.

These guys (pictures from the internet):

verktyg 

Google is your friend...

Not to sound snarky but Google is the best way to search Bike Forums.

For example, I did a quick search on "shimano sis thumb shifters 7 speed with 6 speed" and came up with dozens of hits.

Here's one that sort of answers your question:

https://www.bikeforums.net/classic-vi...ty-issues.html


There's a lot of good info in these Sheldon Brown links too:

Mixing Brands of Shifters, Rear Derailers and Cassettes

Shimano and Shimano-compatible 7-speed cassettes

Shimano Dura-Ace Compatibility


It may be possible to shift a 7 speed cassette with a 6 speed SIS thumbie but it will be trial and error. I've been going the other way, shifting a 6 speed freewheel with a 7 speed thumbie for 25+ years without any problems at all.

The top pulley on SIS derailleurs have at least a millimeter of side to side float which allows the chain to self center on a cog.

Make sure that the bushing in the pulley is in good condition and there is no angular play which can prevent the chain from tracking straight.

SIS pulleys came in in a number of versions.

The early ones were marked "CENTERON" and the plastic part floated on the center metal bushing. Some had rubber seals.



Later ones??? had a ceramic bushing in the plastic body with a ceramic center bush. These were probably the best as far as wear goes. They had rubber seals - not shown. 2nd picture shows pulleys without the center bush.



This style had a metal sleeve inside the upper plastic pulley body. It's marked CENTERON G-PULLEY NARROW and may be off of a 9 or 10 speed RD???



I cannibalized a bunch of pulleys off of junk derailleurs. They show up on eBay from time to time. If you need a replacement pulley, measure the width of the old one and try to find one with the same width.

There may be some modern sealed ball bearing pulleys that have the same side float????

One other thing, get a good modern 6-7-8 speed chain the an SRAM PC-850 or similar style. They are latterly flexible which helps in shifting. Don't pay a stupid exorbitant price for a fancy chains, they all work pretty much the same!


verktyg

Chas.

Steeljunky

Hey there,

i just got got a new set of wheels and a new cassette. I originally had a 6 spd but then my buddy said lets just see if it works. It is totally fine. Shifts beautifully thru all gears and plenty of clearance with derailleur. Did get a new chain too.

Shimano 105 down tube shifters (got the switch for friction v. Index ) and a shimano tiagra RD. It works good even in index mode. Go for it, I'm sure it'll be fine. Good luck!

Edit...it just occurred to me that my rd is not a 6 speed...so never mind. But I'm still sure you can get it to work!

verktyg 

The RD doesn't matter much on 5-6-7-8 speed cassettes. The indexing mechanism is in the shift levers.

9-10-11 speed derailleurs have narrower pulleys and cages plus they use thinner chains too so you can run into some problems.

There are some good links in this message I posted earlier:

https://www.bikeforums.net/classic-vi...l#post18647600

verktyg

Chas.