9-speed to 8-speed conversion

[tykeboy2003]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

So, can I easily convert?

Fitting an 8-speed cassette shouldn't be a problem - might need a spacer?
The derailleuer shouldn't be a problem - anyone know different?
Obviously I'll have to replace the shifters because of the different cable pull required. I suspect the shifters on my touring bike are badly worn anyway (done 12,000 miles on it) as the changes are all over the shop despite everything else being setup properly - hanger is straight and properly aligned etc, the only thing I've not looked yet at is the shifter. I might look at the cable pulls and put the measurements on here later.

So, is it feasible?

[LollyKat]

According to 531colin you can use an 8-speed chain on a 9-speed block. I’ve tried it and it works fine.

[531colin]

I only tried 8 speed chain on a 9 speed bike because all the rest of my bikes are 8 speed, so now I only need to keep one sort of chain in the "spares" drawer.
It works fine, with the caveat that the bike is friction front shift; I don't know how well it would work with front indexing and trim.

However, I don't expect 8 speed chain to be any more durable than 9 speed.
8 speed rollers are wider than 9 speed rollers.
But, the wear thats important is the wear between the inner cage plates and the rivet, because thats the wear which alters the pitch of the chain, and its the altered chain pitch that wears the sprockets in such a way that they won't work with new chain with the proper (half inch) pitch.
I don't know that the bearing surface between the inner cage plate and the rivet is any bigger in 8 speed chains than 9 speed, I would guess it isn't, or at least not consistently.
A chain with better hardening/surface treatment should last longer than one without.....but just binning the chain before it has a chance to wreck the cassette works. See this thread viewtopic.php?f=5&t=116834&start=15 where I have finally thrown a cassette away after something like 10 years use.

[tykeboy2003]

According to 531colin you can use an 8-speed chain on a 9-speed block. I’ve tried it and it works fine.

That sounds like a solution! I'll give it a try, my partner's bike is an 8-speed so I'll borrow the chain.

[tykeboy2003]

Thanks for the replies, I've measured the cable pull at the derailleuer with a micrometer and the results are consistent with what I observe whilst riding; if i'm changing one way (up or down) successive changes are good, however, as soon as I change back the other way it takes 2 clicks of the shifter to change gear. I think I could do with new shifters. Not sure why at the end of the exercise the length is different though, may be something to do with the fact that I removed the chain on the biggest sprocket (gear 1 in the picture) and did the measurements with the chain off. That would suggest some latency in the cabling...

[531colin]

Cable pull per shift for 9 speed is written down somewhere....by Brucey on here, if not by Shimano.

The shifters are simple in concept, if not in execution....there is a ratchet and a pawl (or two) and a "release" lever, so you can dis-engage a pawl and pay out one increment of cable, pulled by the mech. spring. (changing to a higher gear at the back)
The things either work or not; there isn't a mechanism by which they can shift varied amounts of cable.

What you describe is typical of cabling which needs replacement or servicing, and possibly excessive wear in the mech. pivots.

Check for frayed cable in the shifters and at the mech. Lubricate the cable; check that the ends of the outer are cut clean and square, and are fully "home" in their stops.....moving the levers without un-taping the bars is a classic.

[slowster]

Per Chris Juden's Shimergo article (https://www.cyclinguk.org/cyclists-libr ... s/shimergo) Shimano 9 speed rear shifters pull 2.5mm per click and the 9 speed sprocket pitch is 4.35mm, and for 8 speed it's 2.8mm and 4.8mm respectively.

Before going ahead it might be advisable to check on the availabilty of suitable 8 speed cassettes in the ratios that you are considering, and if you have not already done so, to compare the 8 speed gear range and intervals with your current 9 speed gearing. One less sprocket will mean either sacrificing a gear at the end of the range, i.e. top or bottom gear, or increasing the tooth gap between two or more sprockets.

[NickJP]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

This turns out not to be the case. Have a look at the graph below, from a chain wear test article at https://cyclingtips.com/2019/12/the-bes ... cy-tested/. In a test of 8, 9, 10, 11, and 12-speed chains, the 8-speed chain was the least durable and the 12-speed lasted the longest:

[tykeboy2003]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

This turns out not to be the case. Have a look at the graph below, from a chain wear test article at https://cyclingtips.com/2019/12/the-bes ... cy-tested/. In a test of 8, 9, 10, 11, and 12-speed chains, the 8-speed chain was the least durable and the 12-speed lasted the longest:

Very interesting and completely counter intuitive.... maybe I'll stick with the 9-speed then.

[tykeboy2003]

Cable pull per shift for 9 speed is written down somewhere....by Brucey on here, if not by Shimano.

The shifters are simple in concept, if not in execution....there is a ratchet and a pawl (or two) and a "release" lever, so you can dis-engage a pawl and pay out one increment of cable, pulled by the mech. spring. (changing to a higher gear at the back)
The things either work or not; there isn't a mechanism by which they can shift varied amounts of cable.

What you describe is typical of cabling which needs replacement or servicing, and possibly excessive wear in the mech. pivots.

Check for frayed cable in the shifters and at the mech. Lubricate the cable; check that the ends of the outer are cut clean and square, and are fully "home" in their stops.....moving the levers without un-taping the bars is a classic.

Thanks for that, I did recently move the shifter without untaping the bars but only by a very small amount. I don't thing the derailleuer pivots have significant play in them so it looks like the cabling etc.

[Tompsk]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

This turns out not to be the case. Have a look at the graph below, from a chain wear test article at https://cyclingtips.com/2019/12/the-bes ... cy-tested/. In a test of 8, 9, 10, 11, and 12-speed chains, the 8-speed chain was the least durable and the 12-speed lasted the longest:

However, the 8speed chain is a low grade hg40 and the quality level seems to go up as you increase the number of speeds through ultegra and on to xtr. Admittedly a true like for like comparison wouldn't be easy.

[Norman H]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

This turns out not to be the case. Have a look at the graph below, from a chain wear test article at https://cyclingtips.com/2019/12/the-bes ... cy-tested/. In a test of 8, 9, 10, 11, and 12-speed chains, the 8-speed chain was the least durable and the 12-speed lasted the longest:

However, the 8speed chain is a low grade hg40 and the quality level seems to go up as you increase the number of speeds through ultegra and on to xtr. Admittedly a true like for like comparison wouldn't be easy.

Yes,that chart looks less convincing if you plot durability against cost.

[tykeboy2003]

Cable pull per shift for 9 speed is written down somewhere....by Brucey on here, if not by Shimano.

The shifters are simple in concept, if not in execution....there is a ratchet and a pawl (or two) and a "release" lever, so you can dis-engage a pawl and pay out one increment of cable, pulled by the mech. spring. (changing to a higher gear at the back)
The things either work or not; there isn't a mechanism by which they can shift varied amounts of cable.

What you describe is typical of cabling which needs replacement or servicing, and possibly excessive wear in the mech. pivots.

Check for frayed cable in the shifters and at the mech. Lubricate the cable; check that the ends of the outer are cut clean and square, and are fully "home" in their stops.....moving the levers without un-taping the bars is a classic.

Today I removed the cable and thoroughly checked, cleaned and greased it before reassembling. The inner and outer cables were all absolutely fine, I rechecked the derailleuer pivots which had no sideways play in them and checked the hanger alignment which was fine. After reassembly the gear changes were no better, actually slightly worse. I'm starting to be convinced that the problem is in the shifter. I bought the bike new in 2012 and have done over 12,000 miles on it so it's seen plenty of use. Are the shifters repairable?

[nsew]

Which shifters are you using? 12000 is nothing for 9s Dura Ace. Reads like a slack cable.

From the Park Tool website;

If there are two front chainrings, stay on the largest chainring. If your bike uses three front chainrings, shift to the middle. On the rear, start on the smallest cog. Pedaling at a normal riding cadence, shift the shifter only one indexed click, not more than one click. We want this one click to shift one, and only one gear. If the chain did not make it to the next gear, return the shift lever to the outermost click, and turn the barrel adjuster one full turn counter-clockwise. Try the shift again and repeat the process until it makes the shift. If you have un-threaded the barrel adjuster that it has come out, or has nearly come out, thread the barrel back in fully and then out one or two turns. Make sure that you are on the furthest outward shift position and the smallest cog, then remove the slack from the cable at the pinch bolt. Contd....

https://www.parktool.com/blog/repair-he ... adjustment

[nsew]

One for the experts on here.

I have 2 bikes, both 9-speed and I'm getting rather fed up with the chains wearing out and sometimes (if not closely monitored) the sprockets as well. I know that 8-speed and below, the chains are slightly wider and thus in theory should last longer.

This turns out not to be the case. Have a look at the graph below, from a chain wear test article at https://cyclingtips.com/2019/12/the-bes ... cy-tested/. In a test of 8, 9, 10, 11, and 12-speed chains, the 8-speed chain was the least durable and the 12-speed lasted the longest:

Who would of thought a garbage chain doesn’t hold up in comparison to a quality chain. I get between 4000-5000 out of a Wipperman Connex 808 (8sp) while loaded touring in all conditions, using a toothbrush head, various rags and chain oil. Never miss a shift and my mix of TA rings are far from shot. A year or so ago the chains were about £10 a pop from Germany, now they’re £25 but at least we’ve taken back control, inflation is rampant and the shelves are half empty. Foreseeing an impending disaster I had picked up a dozen in 8s and 9s, together with a pile of other consumables. Though should of bought a couple of Velocity rims for a lockdown build. Next pandemic I won’t be caught out. What’s that got to do with an exercise in confirmation bias? Not much.