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Rear Derailleur standards questions

Old 06-17-22, 10:18 PM
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CrimsonEclipse
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Rear Derailleur standards questions

Wasn't sure what terms to search for, so new thread.

I use friction thumb shifters for my bikes that are generally MTB's

My older drive train is in need of overhaul and possibly upgrade.
The goal is a 1x with 8 or 9 rear cassette around 46t to 50t and front of 30t to 34t
(still pondering gearing)
Weight is not a concern.
Price is a concern.
I ride Easy to moderate trails and consider myself average skill level

1. Do I need a short, medium, or long cage for a 1x and how do I determine this?

I know there is a cable pull ratio difference between manufacturers. 2:1 Shimano and 1:1 SRAM (or is it reversed?)

2. Is there a reference or chart that shows the cable pull ratio of each manufacturers?
2a. is there a better terminology than 'cable pull ratio'?

I've seen people refer to off brand (to me) manufacturers of derailleurs like Box, Microshift.

3. Are these manufacturers worthy of consideration?

4. I think I have a Shimano Altus rear hub currently with an 8 speed cassette. Am I right to believe that the spec sheet will allow a 10 sped cassette?

Also, if my terminology is incorrect, feel free to correct me.

Edit:

And capacity!
Is there an easy way to determine capacity (cassette size? T size?)
Some advertisements seem to lack indication.

Edit #2
Also, is a derailleur clutch necessary?

Thanks!

Last edited by CrimsonEclipse; 06-17-22 at 10:28 PM.
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Old 06-18-22, 07:58 AM
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I’ll try the short answer version and then let the more expert advisors re-direct as needed:
1) if you are staying with friction shifters, then really any 8/9/10 rear gear cluster count is going to be just fine (the width of these cassettes are ‘largely’ the same and that is what your shifter (and rear hub) needs to be able to handle. Sometimes 10 can be a bit of a stretch so go with a nine set up—usually cheaper anyway).
2) if a 1x, your rear gear range will determine how long a cage you need—since you are mtb and 1x you will want a very wide range (you mentioned as much in your post) so you will indeed want a long cage rear derailleur (and specifically one designed for that application.)
3) Not all riding requires a clutch but I think most of the super-wide range derailleurs come with a clutch, no? It helps keep the chain on, so only helps
4) I love cobbling things together…but the drivetrain combo (specifically shifter, derailleur, cassette) is one exception—you’ll want to get it as a unit if you can. Box makes a really nice ($200) 9-speed 1x set up that is robust and very functional.
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Old 06-18-22, 08:28 AM
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Originally Posted by CrimsonEclipse View Post
I use friction thumb shifters for my bikes that are generally MTB's

My older drive train is in need of overhaul and possibly upgrade.
The goal is a 1x with 8 or 9 rear cassette around 46t to 50t and front of 30t to 34t
(still pondering gearing)
Weight is not a concern.
Price is a concern.
I ride Easy to moderate trails and consider myself average skill level

1. Do I need a short, medium, or long cage for a 1x and how do I determine this?
There's really no downside to having too long of a derailleur cage, besides a couple extra grams, so err on the long side.


I know there is a cable pull ratio difference between manufacturers. 2:1 Shimano and 1:1 SRAM (or is it reversed?)

2. Is there a reference or chart that shows the cable pull ratio of each manufacturers?
2a. is there a better terminology than 'cable pull ratio'?
Cable pull is only an issue if you're going to indexed shifting. It makes no difference with friction shifting.

And capacity!
Is there an easy way to determine capacity (cassette size? T size?)
Some advertisements seem to lack indication.
Go to the manufacturer's web site for specifics like this.

Edit #2
Also, is a derailleur clutch necessary?
No. Unless you're in the habit of shifting while stopped, at least.
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Old 06-18-22, 08:37 AM
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The "off brand" manufacturers, meaning not Shimano or SRAM, IMO are very acceptable for the price you pay. Especially when SRAMano want 2x $ to accomplish the same task. I wouldn't bank on 25k miles in splendid luxurious smoothness like those guys, but it's a bike. You'll probably change it for something better before it breaks anyway.

For 1x you need a derailleur rated for the smallest to biggest cog on the cassette. The reason is as much the slope the parallelogram operates on as much as it is spring tension & stress at the various pivot points & pressure on the jockey wheels. (I can't tell you how many cracked/broken jockey wheels I've come across. It does happen. )

A clutch is preferred. It help prevent chain bounce that could/would cause a chain drop. In a 2x you have a derailleur that does double duty. Shifting gears, obviously, but also keeping the chain where it is supposed to be.

A Narrow/Wide chainring is especially designed to better hold the chain than conventional chainrings which are designed to let go of the chain for better shifting. A Narrow/Wide virtually eliminates dropped chains in it's own right. It's well worth it.

It's pretty hard to beat a Narrow/Wide combined with a clutch.

SunRace makes more than adequate cassettes in just about any range you could ever want.

Some of the new Trek Marlins are coming with 7 speed freehubs. So in this case, the presence of a cassette does not guarantee a conventional 8/9/10 speed upgrade path. A new wheel may very well be the start of that journey.
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Old 06-18-22, 10:06 AM
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Good information guys, thank you.

Cable pull ratio is still a concern for me. Even with a friction shifter.
The diameter of the barrel(?) seems to limit the shifting range so a different ratio pull makes a difference
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Old 06-18-22, 10:22 AM
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For some time now (since SRAM “1:1” up to 9 speed and later “X-actuation” 11-12 speed, and Shimano 10-12 speed) most nicer MTB derailleurs have needed more cable per shift. The leverage ratio of the derailleur is about the same between speeds and brands. At least close enough I’ve made functioning systems with a Shimano derailleur, SRAM shifter, and Sunrace cassette. There have been a few oddballs, notably SRAM 10-speed

Old thumbies sometimes don’t pull enough cable for new derailleurs in friction mode. But some new thumbies have a friction mode. And yes it’s the size of the barrel. It’s not the first time either… old school down tube shifters like Campagnolo sometimes can’t pull enough for Shimano SIS

You also need to choose a unit that’s suitable for 1x. These may have a larger parallelogram or front knuckle to reach the biggest cog while the cage might be shorter than for a double or triple because there’s less chain to wrap. Don’t worry, it’s all in the paperwork and east to figure out.

you always want some kind of chain retention but it can be quite basic. Inexpensive seven speeds often come with a chain ring that’s sandwiched between two bash guards

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Old 06-18-22, 11:22 AM
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"rear shift ratio"

Shimano standard – 1.7
SRAM 2:1 – 1.7
Shimano 10 MTB – 1.2

Apparently there are a ton of other standards.
I thought it was SRAM vs Shimano only. (oopse)

Long story short, using Friction thumb shifters, close to 1:1= good. 1.7 to 2.0:1= badAlso just learned this:
(#t biggest chainring − #t smallest chainring) + (#tbiggest cog−#t smallest cog)=Drivetrain capacity

So for 1x it's really:
(#tbiggest cog−#t smallest cog)=Drivetrain capacity

46-11= 36T

Some sources indicate around 36t for a medium cage and 45+ for a long cage.
So I'll go with a long cage to keep my options open.

Then there is a MAX cog limit. which seems to vary with manufacturer, model, and time of day apparently.

TL;DR:
1:1 (or close) pull ratio
long cage
Possibly Microshift

Thanks again for the assist!
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Old 06-18-22, 11:34 AM
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Edited prior post. SRAM “2:1” hardware is Shimano SIS compatible (Shimano MTB up to 9 speed and road up to 10 speed). But that’s not going to be an issue as none of those will reach a 46 or 52 cog. They topped out at 36.

SRAM 1:1, SRAM X-actuation, and Shimano Dyna-sys are all about the same leverage. I suspect so are 1x8/9 speed Microshift and Box. Maybe or maybe not Sunrace.

Here is the shifter
https://www.microshift.com/models/sl-m11-r/

SRAM “Exact Actuation” was only on MTB at 10-speed and matches their road shifters. Which is good to know if you want low gears on a SRAM 20 speed bike but not for your project.

don’t worry about the Shimergo stuff. It’s out of date and poorly sourced. The really important fact from that era is that 10 speed Ergos will run a 7/8 speed SIS system, and 11 to 9. For a while it was really cheap to get some Campy Athena or Centaur Ergos from Britain to fix up a 1990s Shimano bike because the Shimano brifters were all dying of old age and crusty grease, and ebaying at a premium.

One last thing. Let me recommend an 11 speed cassette. The shift spacing is really normal through the whole thing. I am pretty happy with 11-42 but obviously enough people weren’t that they made it bigger later. The Shimano 11-42 cassette has slightly nicer shift spacing than the SRAM NX or the Sunrace. On the other hand the Sunrace 11-46 cassette has much nicer shifts than that big granny jump on the SLX cassette.

For the really light cassettes you need a special hub and a fat wallet. But they really are nice.

Last edited by Darth Lefty; 06-18-22 at 12:09 PM.
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Old 06-18-22, 01:35 PM
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Originally Posted by Darth Lefty View Post
The really important fact from that era is that 10 speed Ergos will run a 7/8 speed SIS system, and 11 to 9.
…Can you clarify what you mean here?
I occasionally run a Shimano training wheel (w DA 10 speed cassette) on my Campy 10 equipped bike…top and bottom gears are fine but indexing is a bit off for the middle gears….but are you saying if I throw on an old DA 7 or 8 cassette that it will index thru the gears? “And 11 to 9” meaning? Many thanks!
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Old 06-18-22, 02:11 PM
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Originally Posted by Sonofamechanic View Post
…Can you clarify what you mean here?
I occasionally run a Shimano training wheel (w DA 10 speed cassette) on my Campy 10 equipped bike…top and bottom gears are fine but indexing is a bit off for the middle gears….but are you saying if I throw on an old DA 7 or 8 cassette that it will index thru the gears? “And 11 to 9” meaning? Many thanks!
it means the pull per shift of Campy 10 speed Ergos is about the same as Shimano 7/8 speed brifters or down tube shifters so you can put 10 speed Ergos on a Shimano 14 speed that had like RSX or Exage

Last edited by Darth Lefty; 06-18-22 at 02:15 PM.
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Old 06-18-22, 02:23 PM
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Great to know!!! Thank you!
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