shimano 7 & 8 sp sprocket spacing

[3wheels]

Can anybody tell me if shimano 7sp and 8sp sprockets have the same spacing and if it is possible to use 8sp indexed shifters (down tube) with 7sp cassette.

[amediasatex]

Can anybody tell me if shimano 7sp and 8sp sprockets have the same spacing

No, they don't

5.0mm for 7sp
4.8mm for 8sp

but...

and if it is possible to use 8sp indexed shifters (down tube) with 7sp cassette.

They're close enough that you can normally get away with it depending on how picky you are. There's an argument to say you're better off the other way to whay you're intending ie: using 7speed shifters with 8speed spacing as you'll overshift a tiny bit rather than undershift, but there's not much in it.

If you're trying to make use of an existing 7 speed cassette hub/wheel you could just use and 8 speed cassette and ditch the bottom sprocket. If you buy something with an 11t small sprocket it's a good one to throw out anyway
You could also dismantle a 7 speed cassette and replace the spacers with thinner ones (or modify them).

[Chris Jeggo]

All the information you need about freewheel and cassette spacings etc is here:
https://www.sheldonbrown.com/cribsheet-spacing.html

[fastpedaller]

I use 7 speed cassette with 8 speed (bar-end) shifters no problem.

[reohn2]

They're as near as makes no difference,0.2mm over 5 sprockets* isnt anything

*top and bottom cog spacing is defined by limit screws so only five cog count

[tatanab]

As further evidence that it works, I have some old Deore thumbshifters with 7 marked positions, but also an 8th unmarked.

[gaz]

I use 7 speed cassette with 8 speed (bar-end) shifters no problem.

+1

[thelawnet]

All the information you need about freewheel and cassette spacings etc is here:
https://www.sheldonbrown.com/cribsheet-spacing.html

Well apart from the newer bits that are missing....

[Brucey]

this page is useful too

https://en.wikibooks.org/wiki/Bicycles/Maintenance_and_Repair/Gear-changing_Dimensions

cheers

[Chris Jeggo]

this page is useful too

https://en.wikibooks.org/wiki/Bicycles/Maintenance_and_Repair/Gear-changing_Dimensions

cheers

So it is; hadn't come across that. Thanks, Brucey.

Chris

[3wheels]

Thanks guy's the info was very useful.