jimmuller 

Wrong about what? It has already been proven that folks here didn't know you meant SIS, and you didn't post any correction to help out.

As for chain length affecting the shift range of the RD, that of itself still makes no sense. There may be secondary effects, for example how the guide pulley's vertical position is changed with the amount of chain take-up with pulley cage like a Campy Rally. This could possibly make it so high it strikes the largest sprocket, or so low that it won't generate enough angle for the chain to catch the smallest. But by itself it doesn't affect the lateral range.

ksryder

Your original question was vague and your explanation doesn't clear anything up, yes we're being wise guys but only because no one knows what you're asking.

So if the original question was supposed to be "how does chain length affect shimano index system?" That still doesn't make sense, SIS refers to the overall drivetrain configuration and there are several ways to interpret that. Naturally everyone assumed you were referring to the indexing itself, because that's really the only thing that sets indexed shifting apart from friction.

If your question is "will a too short chain prevent me from shifting into the big cog" then yes, it could prevent the big-big combo. Exactly the same as it does with friction.

BUT.... I feel like now we're glossing over a really big detail you just dropped on us, which is that you're butchering classic bikes by cutting off the downtube shifter braze ons, and brazing on a FD tab.

If these are crappy gas pipe bike boom Raleigh Records and such, then fine. But if these bikes are in any way decent and desirable, then what you're doing is a war crime. Stop ruining classic frames.

There's no reason to do that even if you're doing a brifter conversion. They make cable stops that bolt on to the downtube shifter braze on and you need that anyway to keep the shifter cables from flapping all over. And virtually every front derailleur is available in a clamp on version in addition to braze on.

Kontact

The above highlighted section doesn't actually make any sense. "SIS" is a way the shifter moves to a precise location, but limitations on the derailleur due to chain length have nothing to do with indexing since chain length normally has nothing to do with the lateral movement of the derailleur that the shift lever position influences.

"SIS" is not a legacy product, it is just a label that for a current product that doesn't get much use because it means "Shimano Index Shifting" and there are no qualities to indexing or shifting in general that are peculiar to Shimano any more. So you used an oddly specific brand name to ask a very general question about how derailleurs function, and you expected people to make sense of your question without the complete abbreviation of a largely unused phrase.

johnggold

Here is the Wikipedia definition of legacy when applied to computer systems

"In computing, a legacy system is an old method, technology, computer system, or application program, "of, relating to, or being a previous or outdated computer system." Often a pejorative term, referencing a system as "legacy" means that it paved the way for the standards that would follow it."

Sounds pretty accurate to me. Not only that, but SIS has become generic rather as hoover is used for all vacuum cleaners.

As to the purpose of the original post, which was to investigate an empirically proven link with no obvious explanation, clearly that investigation is less important to you than picking at terminology. This is a forum for discussing bicycles not words.

Hopefully, others will look at the question more directly.

jimmuller 

Bikes aren't computer systems and legacy actually has other meanings that are not perjoritive at all.

As for SIS, try convincing Shimano's lawyers their copyrighted name is generic.

Kontact

It isn't a legacy system - SIS is exactly what virtually all Shimano bicycles have.

SIS is not a generic term either. The generic term, as I already pointed out, is "indexing".


And the problem you didn't really describe was discussed on the first page by myself and several others, so I don't know why you are pretending it was not. Are you just being dismissive?

There is no "empiracally proven link" between indexing function and chain length. Since you claim to hardly work on indexing bikes, what are you basing this link on?

HTupolev

No it hasn't.

I had to look this up. I don't think I've ever heard someone call a non-Hoover vacuum a "hoover." A quick google search indicates that it's a regional UK thing?

We need to know what about bicycles you're discussing in order to have the discussion. That requires using words that people understand.

The responses saying that they didn't know you meant "SIS" were not joke posts.

madpogue 

As mentioned in another recently-active thread here on C&V, "Two countries, separated by a common language"....

And +1 ^^^^^; a simple "Oops, I meant SIS" as post #3 would have increased the signal-to-noise ratio of this thread significantly.

johnggold

Maybe I should point out that my post described an empirical test that showed a link. I could not explain the link hence the post.

Noone has offered an explanation only to say that there is no link.

I know that the only change made was chain length.

As to experience I have been building bikes for 50 years and whilst I restore vintage bicycles I regularly repair modern bikes for friends and family.

SIS has become synonymous with click gearing. I never hear the term indexing used in the specialist cycle groups I work with. The terms SIS STI are common.

Maybe you dont get out much.

I am currently checking the geometry of the derailleur. I suspect that this will yield the explanation as I am not getting anywhere with this post unless someone else chips in.

Kontact

If SIS is such a common term, why did this thread go into multiple pages without a single person guessing that's what you meant?

I've been a shop mechanic since 1990 and participate on four cycling forums. Do you really think I'm unaware of what I'm talking about? Where is it you're hearing "SIS" all the time?

Anyway, you had a problem with shifting that changed when you changed your chain length, but since you disappeared, no one could ask you if you also adjusted B tension as you would after a change in chain length with a Shimano double sprung derailleur. Because we don't know more, we couldn't possibly say if the chain was important or if you simply failed to complete the adjustment. Additionally, if you have a hangar alignment issue, top pulley distance will exacerbate the problem.

So you didn't have empirical evidence of a correlation, but a mechanical mystery you haven't attempted to fix. Many shops install chains at max length to avoid problems should the customer switch cassettes later. It normally isn't an issue if the rest of the set up is correct.

noglider 

@squirtdad, I'm an old unix head. I work at a university in Electrical Engineering. Now even the young professors don't know vi. I still love it. I know lots of keyboard shortcuts, and you'd be amazed at how fast I am with it.

squirtdad

@noglider as a cobol guy who worked hard to get to GUI, I could not get the preference of the unix guys for command line.....I even had to build a command line interface to a perfectly good out of the box GUI application. Of course part of it was VI and I did not get along well. I do understand the attraction, I remember doing command line CICS...... but let me see the unix types break down a COBOL dump over the phone at 2 am I manage now, so the coding world is safer

noglider 

COBOL!? Ew! Ick!

CLI/GUI is a matter of preference. I'm a heck of a typist, and I'm an awful mouser. I've been using a mouse since 1988, and I'm still terrible with it. I click the wrong things frequently.

johnggold

It just goes to show how little you read of my original post, since you were so caught up in your own agenda.


"

I adjusted the angle in case the derailleur was hitting the cogs". There is only one way to do this - using the B tension screw. With your experience you should have known that. I also made it clear that I isolated the fix to a single action - reducing the cable length by 4 links.


So, for those of you who need it spelled out in simple terms, I fixed the problem with a single change - removing 4 links. All other variables including B tension screw were not touched. This should not have worked, but it did. The question is why it worked. I believe it has to do with the geometry of the derailleur being altered by the chain, but I can't work it out.


As to other comments, I appreciate that the USA is isolated from the rest of the world, but it is wrong to assume that what happens in the USA is reflected elsewhere. Hoover - a USA company still gives its name to the device in every English speaking country apart from the USA, despite having lost its world market share to a UK company - Dyson.


SIS is not a registered brand name - it is very difficult to use a pnemonic, and SIS is in use in other markets. Shimano had to add a word in 2003 to register "SIS INDEX" as a copyrighted brand name.


As to leaving extra links just in case down the line the bicycle changes - thats just shear laziness. We have a UK store that does things like that, largely because they have minimally trained staff.


Finally, as to disappearing, unlike some I have to work, plus there is a time difference, plus frankly there was little to respond to. If people won't take the trouble to read a question properly, then it is unreasonable to expect a response.

johnggold

I do use Quick links, but only on modern bikes. It is a pain the old way, but I invested in a Park tool, which seems to need less effort to push the rivet back.

Bigbus

I just assumed from the start that OP meant Single Index Shifting vs Dual Index Shifting. I have 2 bikes with one system on each. I prefer the Dual Index for a much snappier shift up and down the gears for road riding, while I like the Single Index on my MTB because you can feather down gears and they snap back up. Riding a friction shift bike is similar to driving a truck with a non-synchro trans-you gotta feel it.
I use missing link chains and I reuse pins when I have to. Never had a chain come apart on me yet (knock on wood).
I also thought the OP stated a very good question and after reading this entire thread including all the juvenile comments, I still haven't heard any specific reason for it even though I have experienced the same and always just assumed it was because the RD fell too far from the cogs to get a tight shift action out of it.

Kontact

Again, it is hard to help someone that doesn't know how to say what they adjusted because they use oddball terminology and then flee their own thread.

And when they do come back, acts like a know it all, even though they still don't know anything more than when they first asked. You're awesome.


People here call them "vacuums", not "hoovers". People in other countries call indexing "indexing", and I know that because this and many other forums have plenty of non-US members.

Is it? On a 10 speed chain, how do you add links back on? With more quick links. Not a pro look.

If normal derailleurs (not your's, clearly) works 100% at a longer chain length, why run it shorter? Because some guy who doesn't know why his bike isn't working is convinced chain length is the underlying issue? No, that would be stupid.


You started the thread 8 days ago. Do you work on a submarine?