etherhuffer 

Setting up rear derailleur and my low limit screw is all the way in, yet it seems dicey. No rattle as I shift. Afraid it might jump over. Can I reduce the 4.5 mm spacer behind the cassette for better adjustment on the big cog?

BobFishell

You're mounting a 7-speed cassette on an 8-speed hub? I don't know of any way to move the cassette inward towards the hub. If you used a smaller shim, you wouldn't be able to tighten the lock ring. Maybe you could jury-rig something between the lockring and the outermost cog, but I would not trust it. You should not be using your big ring with your innermost cog, anyway.

ThermionicScott 

If this is for an old bike, why not replace the freehub body with a 7-speed unit?

Bill Kapaun

Longer "L" screw?

fietsbob

As I recall , 7 speed used a screw on small cog , not a lockring, so driver needs have outside threads..

Retro Grouch 

Check the derailleur hanger alignment. On a bike that age, that's always a good bet to be out of alignment. On a 7-speed you can do this yourself.

1. Shift into a gear combination that makes the derailleur arm point straight down.
2. Stand your bike up vertically and look at the derailleur from the back.
3. If the derailleur arm seems to be pointing toward the wheel - there's your problem. It should point straight down. That's why you need so much low limit screw adjustment.

If you decide to bend it back yourself, be sure to do it with the derailleur or something else filling the derailleur mounting hole. Otherwise you can ovalize the threaded hole and that's bad. 7-speeds are easy to eyeball the alignment. 9 and up I'd recommend using the proper alignment gauge.

BobFishell

I have one in my junk box somewhere, but I think they use a lockring, same as the 8-speed bodies. There are a few pictures on line.

zjrog

I just did this on my 1992 Trek 1400, Went to an 11 to 28 cassette in the process. I used a 4mm spacer.

Nice and crisp shifting. New KMC chain but 27 year old 105 1055 group.

I swapped a wheelset with 105 5600 hubs.

etherhuffer 

Might be the cheap fix of the day!

etherhuffer 

I am a Luddite, newer Long Haul Trucker with 8 speed hub, 7 speed shifters/cassette. Chainline issues in the setup

Wilfred Laurier

Recollection incorrect!

Well, perhaps there was a short time that Shimano was making cassettes like that (UG era?), and many 7sp freehub bodies have threads on both the ID and the OD, but since my first job in a bike shop in 1990, 7 speed cassettes have the same separate lock ring as higher gear counts.

rccardr 

Key date in your response is 1990, by which time all Shimano cassettes and freewheels were HG.
However, deep in the bowels of time (or at least prior to 1988 when HG was introduced) everything was UG and used a locking first cog.
So Dura Ace 7401, Tricolor 6400 and 105/1051, all 7 speed setups, used a locking first cog.
Later 1055/56 105, 6402, and later 7403 used primarily HG with a lockring, but even those freehubs had both internal and external threads and could accommodate either UG or HG cogs.

fietsbob

OK dont own one , so no purpose in archiving the history part numbers etc..

obviously others go in for that .

Maybe OP went to one of Seattle's bike shops for professional help.

reads like 7 of 8 was just because they cant get the stroke width between limit screws far enough .


free was inadequate advice ..

etherhuffer 

So.... I had several sets of seven, all NOS. prefer 7 over higher numbers. On a 8 hub, I can get the low chainring and big sprocket to work. But now, the big chainring, small cog is out. Very small tolerances, most from front cage width. The local shop helped a lot, unlike many other locals who cannot count below 9. The fetish of 3x>7 is odd to me.

Kapusta

This is the first thing I would look into. Cheap and easy to try. Might not work, but it is the best AND easiest solution if it does.

fietsbob

Did you put a spacer* on 1st, then slide your 7 speed cassette , yet?

* Thickness, equivalent, to that 8th cog..

ThermionicScott 

You're supposed to trim the front derailleur as you sweep from one end of your range to the other.

Kapusta

Yes. Read the OP.

Troul 

add a spacer between the frame & hanger if you cannot find a thicker hanger.

etherhuffer 

So this ended up being a spacer and FD line up issue. It is still really tight on clearances. Local bike shop fellow had way better 3D vision than I do. Sometimes it pays to pay for good work.

HillRider

I installed a 7-speed cassette on an 8/9/10-speed freehub body using the needed 4.5 mm spacer. Normally the spacer goes behind the largest cog but the cassette I used was held together with thin hex head bolts and the bolt heads interfered with the spacer. I could have filed clearance grooves in the spacer but, instead I installed the spacer between the smallest cog and the lockring. Worked just fine.