Can you use a 7 speed shifter on a 6 speed cassette?

[dalifnei]

Following on from my previous post about my problem shifting...

I've been donated a 7 speed shifter
Do you think I can use it on my 6 speed cassette?
Or would it be problematic?

Thx!!

[cycleruk]

The "numbers" say they don't match.
http://www.ctc.org.uk/cyclists-library/ ... s/shimergo

The cable pull of a 7 speed is less than a 6 speed so, though a couple of cogs might work, the rest will gradually not.

[fossala]

Can you switch it to friction mode? If so it will work with anything.

[Urticaria]

Why don't you give it a try? You might find it is alright, or at least you can regain most of your gears.

Using the figures above, the difference between 6 & 7 speed sprocket spacing is 0.5mm per step, so if you were to set up the rear derailleur so that it is spot on when over sprocket 3 or 4, at worst it will be 1.5mm out when hovering over the extreme inside or outside sprockets; the sprocket spacing is 5.5mm, so it is out by about about 1/4 of a spacing. It is still going to work, but it might be a bit noisy.

[fossala]

Why don't you give it a try? You might find it is alright, or at least you can regain most of your gears.

Using the figures above, the difference between 6 & 7 speed sprocket spacing is 0.5mm per step, so if you were to set up the rear derailleur so that it is spot on when over sprocket 3 or 4, at worst it will be 1.5mm out when hovering over the extreme inside or outside sprockets; the sprocket spacing is 5.5mm, so it is out by about about 1/4 of a spacing. It is still going to work, but it might be a bit noisy.

I couldn't get a 7 speed shifter to work on an 8 speed cassette (using limiting screws to stop it before the last cog) It would skip near the smallest cog and if I got it set up so it wouldn't it would to the same at the large end.

[Brucey]

if you mount the cable on the other side of the pinch bolt on the rear mech, this will increase the throw of the rear mech per click and this will usually allow a 7s shifer to work a mech on a 6s cluster.

hth

cheers

[Urticaria]

Sheldon has a picture here to illustrate what Brucey has suggested. You can see that the cable in position B is shifted by about a diameter from where it was originally, and this increases the lever ratio and hence the distance the derailleur moves per click.

[Mr_average]

Many years ago when 6 and 7 speed were the norm I had this 7 speed lever on a 6 speed drivetrain setup. All the literature said it should work, and every bike shop I went to confirmed this. But it never did - until one shop said 'ah, that's because it's the first shift that you should be wasting, not the last'. After that it worked way better, but IIRC still not as we'll as the proper 7 speed setup I moved to shortly afterwards.

[Brucey]

this is the shimano/sheldon illustration of how to revise the cable mount and make the mech move further per click, as per Dura-Ace 'old' vs 'new' pull ratios;



However not all mechs give the same increase; you are (for running a 6s system on a 7s shifter) looking to increase the throw of the mech by about 10%. To do this, the distance from the left outer sideplate pivot to the cable mount needs to be reduced by about 10%.

On some mechs you get this change right off the bat with the alteration illustrated. With others, the alteration isn't quite enough, unless the tab washer is modified slightly. For example filing the tab smaller can work, or simply bending it outwards slightly, (so that it can be rotated further ACW) can make enough difference too.

Needless to say a 7s shifter with no cable mount adjustment on a 6s system will just be rubbish otherwise.

cheers

[gaz]

.

[JohnW]

Can you switch it to friction mode? If so it will work with anything.

..............absolutely - friction down-tube gear-change levers are the way forward for cycling. I don't know why the manufacturers haven't thought of it.....................er, well I do actually.

[blackbike]

I love bar end friction shifters and have fitted them to all 4 of my main bikes.

The Dia-Compe ones are superb. I use them on 7, 8 and 9 speed set ups.

[BigG]

Back in the day, when Mr Shimano made 7 speed bar end shifters, they came with a little plastic sleeve to fit in the groove where the cable wraps around the shifter barrel so they would index with 6 speed. Increasing the barrel diameter pulls more cable per click.

If the shifter is bar-end, thumbie or down tube it may be possible to experiment with some insulating tape wrapped around the inner cable after it's been poked through the hole in the shifter.

Not only bar-end shifters, but my 7-speed Ultegra downtube shifters have the same insert. It works fine on a 6-speed freewheel.

[JohnW]

[quote="BigG.............my 7-speed Ultegra downtube shifters have the same insert. It works fine on a 6-speed freewheel.[/quote]

Attaboy, BigG - tell 'em............