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I'm replacing the rear shifter on my old Kona mountain bike from the late '90's. It has an 8-speed rear cassette with a Deore XT derailleur. I got a basic ST-EF500 8-speed Shimano shifter/brake combo, but I was having a bear of a time indexing the gears. After about 10 minutes of messing with it, I realized that on the large cog, the display showed gear 2.

So, I went back to the small cog and counted the stops on the way up to the large cog. Sure enough, it was 6 steps on the shifter to travel 7 cogs from the bottom to the top (and the shifter wouldn't go further, which is probably a good thing since I don't want to shift into the spokes). I disconnected the shifter to make sure that it actually had 8 distinct stops and wasn't defective and it functioned as advertised.

It appears, then, that a distance of 6 stops on the shifter matches nearly perfectly the distance of 7 cogs from top to bottom of the cassette even though they are both Shimano. Is this a known thing? Were there special narrow cassettes for mountain bikes in the '90's that I just didn't know I had?

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  • What was wrong with the old shifter? Can you refurbish it and reuse it ? – Criggie May 22 at 23:43
  • The thumb lever would slip without some significant off-axis force. Possibly, I could disassemble the shifter and fix it, but since I'm not familiar with the internal workings of this style shifter, the effort would almost certainly exceed the $40ish price of a decent replacement. – Aubrey da Cunha May 23 at 14:07
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Sounds like you bought the wrong shifter. The "ST-EF500" is available in both 7 speed and 8 speed

A 7 speed shifter has 7 resting positions, and will click 6 times across its range.
ST-EF500-7R4A

Likewise, an 8 speed shifter will click 7 times.
ST-EF500-8R4A

If your cassette has 8 cogs total, then you need an 8 speed shifter.


If you're totally stuck with these parts, you could make them work somewhat by ignoring one outside cog. The inter-gear spacing between 6/7/8 speed is the same, and the cassette gets wider as gear count increases.

Conversely, 8/9/10 speed cassettes are all the same width, but the inter-cog spacing decreases.

You could choose to disregard either the top or bottom gear, and index the other seven. If you never spin out while riding, then exclude the smallest cog. If you never ride up hills and need a low gear, then exclude the largest cog from indexing.

This is not an ideal solution - the correct shifter would be best.

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  • Surely the OP would have noticed that his/her shifter display had "7" as the highest numbered gear rather than the desired "8" were this the case, no? There's also this quote " I disconnected the shifter to make sure that it actually had 8 distinct stops and wasn't defective and it functioned as advertised." – Armand May 23 at 0:32
  • @Armand fair point. You could post an answer of your own on that basis. – Criggie May 23 at 2:29
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The only thing I can think of is that maybe the various adjustments are set so initially you are barely on the 8 side of gear 7/8 and after 6 steps you are barely on the 1 side of gear 1/2. It's worth examining your rear derailleur closely to make sure the hanger is straight and the derailleur itself isn't binding or damaged.

I would go through the full recommended setup steps for both the shifter and rear derailleur from the beginning, after making sure that all cable/stop junctions are fully seated, any cable "adjuster is initially tightened to the point where it is 1 turn loose of the fully-tightened state.", the cable loops up front aren't binding when the handlebars are turned full left or right, etc.

Here's the link to the "dealer" installation manual for your shifter/brake lever combo: https://si.shimano.com/api/publish/storage/pdf/en/dm/MBST001/DM-MBST001-01-ENG.pdf

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  • Related to this idea - the limit stops on the derailleur may come into it as well - if one is set a whole cog inward that could make the shifter not click to the last position. – Criggie May 23 at 5:55
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    I did go through all the checks in your second paragraph, since that was my first thought, but I hadn't considered the possibility that the derailleur itself was damaged. Given the number of times I have wrecked on this bike, a real possibility. – Aubrey da Cunha May 23 at 14:02
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    With respect to limit stops, I also checked that the low stop was directly below the large cog and the high stop was just a hair outboard of the small cog, since that was my second thought. – Aubrey da Cunha May 23 at 14:03
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    @AubreydaCunha Yes, you sounded like you had some wrenching knowledge. Please post the result once you figure it out -- it's a real puzzler! – Armand May 23 at 14:28
  • Upon closer inspection, the derailleur isn't damaged and moves smoothly, so that theory is out. – Aubrey da Cunha May 27 at 1:27
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Have you checked that your derailleur hanger is straight? You’d need a hanger alignment gauge like the Park DAG or Shimano TL-RD11, etc. there are lots of different options from different bike tool suppliers, but it’s always my first step with any rear derailleur adjustment, to check the hanger. I also find most of the bikes I see are at least a little bit off. If the hanger is bent inwards, that could cause 7 (or even fewer) gears on an 8 speed shifter to cover an entire 8 speed cassette.

If you don’t have a derailleur hanger tool and don’t want to buy one, you could have a local shop straighten it, use one at a local bike co-op, or, if you have a good relationship with your bike shop of choice, you might be able to borrow theirs if they have an extra one or an empty stand when they’re not busy. I did that once at a bike shop near my college campus (straighten the hanger at the shop, finish the adjustments at home), but that was before COVID.

If you don’t know what you’re doing, you could ask the shop to only check the hanger alignment, and then go through the rest of the adjustment steps yourself. You will have to re-check the rest of your derailleur adjustment after straightening the hanger.

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