7-speed shifter, 8 speed wheel, can the shifter make it to the easiest gear?
 

A bike has a 7 speed indexed shifting set up for the rear. The rear wheel broke and I picked up a cheap 8 speed wheel in the used market. When I tried to set up the the drivetrain, I had hoped to use the all the easier gears and leave out the hardest one because I am too casual a rider and just chill on the way down instead of pedaling.

Can't get it to work though, I can't screw in the derailleur deep enough so that it would stop at the second hardest gear, and the shifter just can't hit the biggest gear consistently. This is by design right? But I didn't seem to have this problem when I did a similar thing on an old 6 speed bike bike with a 7 speed wheel, I used the friction shifter to do 1~6 on a 7 speed cassette.

If this is indeed by design for the indexed shifting, I wonder if I can go get a spacer so I can do a 7 speed like 1~6, 8, and skip the 7th gear.

Cassette or freewheel? A 7 cog cassette can fit onto an 8 cog freehub body but wants a 4.3mm spacer behind the large cog. Is this your set up?

Perhaps when you talk of an 8 speed wheel you mean a wheel with an 8 speed cog already on it? Do know that 7 and 8 speed indexed systems are not meant to interchange. The cog to cog spacing is slightly different and after a few shifts this difference catches up with clean shifting and quiet chain running.

A bit more description will help us help you. Andy

7 speed trigger shifter, acera derailleur, 8 speed cassette and compatible freehub wheel, cannot do a 1~7 setup ignoring 8th gear, was only able to do 2~8 ignoring the 1st gear, I did reach clean shifting, but it sucks not having access to the easiest gear going uphill.

8th gear is the easiest gear? Why when the bikes I've owned with gear indicators on the shifters do they label the easiest gear as the 1st ?

All my life it's been understood that 1st gear on any thing with a multi speed gear train is the easiest gear ratio. I'll push back on any thoughts that we should describe the easiest gear as 6, 7, 8, 9, 10, or 11 depending on how many cogs are on the rear.

If the question was more about replacing a cog instead actual use of the bike, then maybe you could convince me that the big cog on a 8 speed stack is the 8th gear.

So what happens If you unhook the wire and move the derailer by hand, will it swing across the whole cassette then?
Have you backed out the limit screw all the way?
IME, it should work. Only time I’ve run out of reach was with an old clamp-on derailer and a newer wheel.

That's what I was thinking too when I wrote that message.

can you actually take out the 7th gear in an 8 speed cassette and turn it into a 7 speed cassette? Or would the cassette not work because the spacing issue or the flow is not continuous anymore?

the derailleur has no problem reading the largest gear on its own. To attempt 1~7, the h screw was all the way in and the l screw was falling out of the socket, but the shifter still can't make it go to big gear consistently. So I had to give up on that.

Not all Shimano ders are intended to swing the amount needed OR maintain the pulley travel amount per lever click across 8 cogs. This and the slop that can work into used lower end ders (pulley bushing, der parallelogram link pivots and B and cage pivots) can mean the system is not optimal at it's extreme.

And then there's what I mentioned before. That the 7 cog indexing spec is different from the 8 cog one. Shimano never intended the two cog counts indexing to be interchangeable. Shimano use to claim reverse compatibility for ders but not forwards. So an 8 speed rear der should work with a 7 cog lever and cassette but a 7 cog der won't with an 8 cassette and lever. The mix match will shift for a few cogs just fine before the .2mm cog C-C spacing difference adds up and the upper pulley won't be under that next cog with the next shift. Andy

OP: You need to spend a bunch of time on SheldonBrown.com to understand your predicament. Friction shifting is very forgiving and works with a number of different speeds. Indexed shifting is very specific and you can't mix speeds between shifter and cassette/freewheel. If there is a bike coop where you live you might find someone who will spend the time to explain.

Don’t make things difficult for yourself.

Go online and buy a cheap 7 speed cassette with the gearing you want. It doesn’t have to be Shimano, only Shimano compatible. That will narrow it down to 99.99% of all 7 speed cassettes.

Buy a 4.3mm spacer Andy mentioned above, to put on the freehub body behind the 7 speed cassette.

Adjust the high/low limit screws and the B screw if necessary.

I might be the odd man out, but I was taught the first position is always the first cog from the dropout. I will gladly accept as much pushback from anyone, but first go online and try to buy a first position cog for a multi-speed cassette or freewheel. You’ll find a lot of 10-12, a lucky few 13t, and for older riders, and juniors, the grail 14t.

John

His site is what makes me come here and ask for help in layman's terms. It's very technical and the stuff usually goes over my head most of the time.

If you can't learn by reading then the LBS is the next better step to find out. Andy

I'm sorry but I have to disagree. This is the most layman's terms place you can get that actually tries to teach you something.

Old style site, creator long deceased, hard to navigate/find what you really want and some content has been lost. But it holds up well for useful info. Keep reading it and maybe you'll have a epiphany or a-hah moment.

ParkTools will be my next site to look for specific info on adjusting and replacing components, but they don't go if for making two dissimilar things work together.... IE 8 speed rear with 7 speed everything else. Sheldon liked to discuss such things.

https://www.sheldonbrown.com/speeds.html

If you look at S.B.'s crib sheet for cassettes/FW's you'll see that 8 speed is wider overall than 7 speed.

https://www.sheldonbrown.com/cribsheet-spacing.html

Many of the 8 speed also have a different spacing. Will it be an issue? Maybe, maybe not. Depends on a lot of things. But you'll simplify your issues if you get 8 speed shifters and maybe an 8 speed rear DR if your current DR will not make the required travel from one side of the stack to the other.

While I suppose you could handicap yourself and not use the full range of cogs, I wouldn't. If that's what you want to do, then that's more your specialized skill you'll have to develop on your own.

The Sheldon Brown site can be overwhelming and is difficult to navigate. Start with this article: https://www.sheldonbrown.com/free-k7.html . There are links toward the end that you can branch out to. Good luck. An alternative would be a local bike coop or a friendly local bike shop.