Anyone?

Ta

The indexing or whatever you call it will be out of sync. I think. Different amount of cable pulled by the shifter for 7 vs 8 speeds.

Isn’t the the physical space between the gears different on a 7 and 8 speed which is why 7 speed chains are wider than 8 speed and on.

And this would mean that you couldn’t use an indexed 8 spd shifter.

Ta.

You could use an 8 speed cassette with one sprocket missing?

http://sheldonbrown.com/speeds.html

has it really been that long since folk dealt with 7 speed that they have forgotten

shimano 7 speed will work with shimano 8 speed

spacing between cogs is the same the freehub was made wider to accomodate the 8 speed system as oppose to on the 9 speed system the spacing between gears was reduced to fit onto the same freehub body

an 8 speed cassette will not fit on a 7 speed freehub but a 7 speed will fit on an 8 with a spacer

the last click on your 8 speed shifter will do nothing

Isn’t the the physical space between the gears different on a 7 and 8 speed which is why 7 speed chains are wider than 8 speed and on

I asked a similar question once and was told chainwidth and tooth width were not the issue.

I was asking whether a 7 or 8 speed setup would last longer due to there being more metal involved.

The space between the sprockets is the crux if you’re trying to mix and match 7/8/9 speed shifters/cassettes.

EDIT: just read trailrat’s post. I did not know that. Every day’s a schoolday…

“spacing between cogs is the same”

I think there is actually a .2mm difference or something tiny but it can be set up to work fine as you say. 7 and 8 speed chains are the same.

TJ,

Check this crib sheet:

http://sheldonbrown.com/cribsheet-spacing.shtml

If your 7-speed is HG, no worries.

The minute differences in sprocket thickness and spacers is not going to mess up the indexing, especially if you have an XT or better mech with the floating ceramic/cartridge bearing guide pulley.

As for the chain, KMC guarantee their 9-speed works with 8-speed cassettes, so may work with a 7-speed HG.
Worth a try if you have one available.
I would be interested in the result.

PaulD

Trail rat has it. I though people used to do this all the time? …And using the ‘lost’ click’ on old 7 speed shifters too?

6/7/8speed systems all take the same width chain (and chainrings too, but you can use narrower 9 speed chainrings with 7/8 speed too).

The only oddity i remember is that a front mech for 8 speed has a slightly narrower cage than one for 7 or 9 speeds. (which are reputed to be the same width iirc)

Ta chaps – I actually ended up in a shop that had the chart showing the 0.2 mm difference and the mechanic swore it would work – so we set it up. Works on the stand, awaits a test ride

My esteemed Institute of Physics pal Crikey has it, there is a tiny difference and I’ve been told it works but I’ve not tried it.

used to work fine for me..

found it best to set the indexing up on the middle gears though

then its only slightly out at each end with the tiny differences in spacing.

Wot Trail Rat said.