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Are all ring sets compatible with all cog sets?

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Are all ring sets compatible with all cog sets?

Old 07-30-13, 07:01 PM
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Are all ring sets compatible with all cog sets?

I'm new to all this, and frankly, am having an issue:

I just got home from the LBS. I had ordered a 36h rim because I kept breaking spokes.

Now, before we start, I'm trying to build a touring style bike on the cheap, but, want/hope for something that works.

I'm trying to learn mechanics as I go, so I ask questions and am hoping to take a class this fall being taught by a local bike mechanic/salesman.

Here's the thing, they couldn't mount my old cog set to the new rim. My bike is a Giant Revel 2 and had a 14x34 7 speed cassette. The crankset is 28-38-48.

The new cassette is a Shimano Hyperglide CS-HG20-7...a 12x32 7 speed.

When I mounted the new rim(and cassette) I found I had a fair amount of apparent chain vibration when in the big ring and small cog. This seems to disappear when I shift to middle ring or to a different cog.

Frankly, I'd love to have the smaller cog, because I'm guessing it might give me just a slight bit more road speed.

I've also read that this could be due to the chain needing adjusting(lose a link or two). However, this wasn't an issue before.

I should also note that lately, I've noticed shifting difficulties with the front derailleur which seems at times to need to be tightened only moments later needing to be loosened. Granted this could be a whole different issue.


At any rate, the vibration seems to occur in the rear derailleur pulleys. There is no apparent grinding, I can't see any rubbing and it rides okay, and frankly, I've just had a couple of days off...but it seems to ride a bit faster with the 2nd smallest cog riding like my former largest cog...

I appreciate any help, and plan to talk to the LBS tomorrow anyway...but I'd really like to...hope to, fix the problem on my own....


Thanks for taking the time to read this, thanks for any advice...Happy cycling!
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Old 07-30-13, 09:12 PM
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I don't know what would be causing the vibration, but I very much doubt that it is caused by the new cassette. The rear derailleur will need to be re-adjusted for the new rear wheel; my first guess for the vibration would be that the upper limit screw needs to be adjusted.

Changing from a 14-34 to a 12-32 cassette should not require changing the chain length unless the chain was already a bit too long before you switched the cassette.

Is the front derailleur issue new or did it happen with the old cassette too? I can't think of any reason a new cassette would cause those symptoms, but there's always the possibility.
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Old 07-30-13, 09:15 PM
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Yeah, there is a lot to learn! I don't know much myself! But if I keep working at it....

One puzzle: the cassette fits to the hub, not the rim. To get more spokes, you must have gotten a new hub also. Mostly new hubs are "free hubs" rather than the old freewheels. But maybe the Revel 2 came with a freewheel hub set-up. That would explain the incompatibility.

One idea I have: the new cassette might not be exactly in the same relationship to the rear derailleur as the old cassette. You might have to adjust both the cable slack and also tweak the adjusting screws, to let the derailleur go out a bit further. Perhaps it can't shift completely to that smallest cog. A bit of adjustment of the rear derailleur when switching the whole rear hub set-up, that seems like a first try-this.

Yeah you might need to take a link out of your chain because the cog is smaller. Actually you should really replace the chain. The old chain will have stretched to match the wear on the old cassette. Though if you only had a few hundred miles on the old set-up it is probably no big deal. But a new cassette can easily require a new chain.
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Old 07-30-13, 09:53 PM
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I've messed with the limit screw on the rear derailleur as it over shifted and lost the chain, at first.

I've also been messing with the front gear shift cable, as shortly after I bought the bike, I found that derailleur adjusted so loose I had to take up slack in the cable. Shortly, after that, the cable itself broke, right at the connection to the derailleur, leaving the system temporarily adjusted, but leaving me relatively unable to adjust tightness at that point again. I can only adjust at the shifter. Yeah, I think I ought to just give that one up and buy a new cable.

As to other adjustments, I'm aware of how the high low adjustments work on both derailleurs, but on the rear there is a third screw which seems to adjust how far the mechanism extends. What I've found online seems to indicate this adjusts/calibrates somehow with the largest cog...not the smallest. I'll adjust it a bit one way and see what happens...as I said, I'm not sure what it does, but I can always adjust it back...and this action might alleviate the problem


any other advice would be helpful...and I'm very careful on such blind adjustments as I'm very aware of the dangers of a little knowledge....
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Old 07-30-13, 10:07 PM
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definitely watch the limit adjustment that comes into play with the large cog. If you let this go too far then you can catch the spokes with the derailleur and that is a nasty mistake. Just tweaks things a bit at a time and watch closely what is happening.
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Old 07-30-13, 10:18 PM
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Chains for derailleur bikes are 1/2" pitch.. the chain for 8 or less speed is interchangeable, pretty much

9, 10, 11 speed each need their own chain width ..
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Old 07-30-13, 10:31 PM
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I'd say I got lucky, in a back handed kinda way. I messed with the limit adjustment, which did nothing to alleviate the problem. I also adjusted as far as it would go in both directions...over several different adjustments....which did nothing.

But, then again, I didn't put the derailleur into the spokes, which would have really freaked me the #### out.

If I understand fietsbob correctly, switching from 7 speed to 7 speed should mean no real difference for chain width.

I'll talk to the local experts at the LBS tomorrow and hopefully, take care of the problem.


Frankly, I'm thinking, for all of my tight budget...very tight budget, I'm ending up with a list of "wants" and "needs."

Which is a bit discouraging.... I mean who wants to spend money simply to stay in motion. It is a lot more fun to spend money to stay in motion with style!
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Old 07-31-13, 04:56 AM
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Mycoalson, Expense wise keep everything in perspective, the bike comes second to most other life items.

I think you may need a new chain. Pins on a new chain will align with a 12" span. An extra 1/16" indicates a stretched chain which seldom works properly with a new cassette/freewheel. Measure at three points of the chain. KMC and SRAM have perfectly good inexpensive chains.

Brad
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Old 07-31-13, 07:29 PM
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Bradtx, I certainly appreciate that. However, I'll be quite frank, I took the bike to the LBS. I was told it would be a quick adjustment, a matter of a couple of minutes. 2 and a half hours later I was leaving. This might initially sound like it irritated me. It did not. I ended up with a new cable for my front derailleur, I had a couple of links knocked out of my chain. I took a test spin and the bike shifted smoothly. However, the chatter or chain purring in the big ring and small cog, remained, albeit not quite as pronounced.

I honestly get along with these guys well enough and had been glad to learn something at the shop. I was also glad for the service and the price was right.

What frustrated me was getting it home and realizing it no longer shifted well on the rings. I messed with it and messed with and messed with it some more...nothing.

As to the cassette...well, the chain purring was back in full force and shifting was a difficulty.

Now, is where things take a turn for the weird....my tires are virtually new...but I noticed in the shop that one seemed to be rotating a bit oddly. The mechanic noticed this as well. The molding didn't look right to him. In the last month, I've had a flat, two broken tire belts, and several broken spokes. The sorts of things that can just happen. But, this tire didn't have a broken belt, it looks to me as if someone tried to actively twist it or wring it like a rag. Bear in mind it wasn't always like this.

Here comes the next bit: After jacking around for two hours at home, with a front derailleur that is either so tight it won't shift down, or so loose it won't shift up....I get desperate.

I look at the front derailleur and realize although there is no apparent damage or ding, it looks "wide," meaning, that if I adjust it one way, it isn't narrow enough to go the other. So, I get out a crescent wrench and squeeze it in....suddenly my front derailleur issues are resolved. I can actually adjust it so that it works.

Since, I've done everything I can to work the rear derailleur, and a bike mechanic also tried...it makes me wonder if something has been bent or done to the rear derailleur causing it to have "chain purr," on that small cog.

My point in bringing up the tire, as well as the front derailleur, at this point is, this is the sort of damage that seems pretty specific, not likely to happen given my riding habits, but so low level that vandalism seems stupid. Meaning a real vandal would just screw it up. This is the sort of thing that seems very unlikely to naturally occur, but causes real headaches trying to address.

I do believe I've irritated someone who has some knowledge of how bikes work...but, I can't swear to it, and making accusations would be ridiculous.


At any rate....chains been shortened, mechanic at lbs took a look. I was supremely frustrated upon arrival at home, but some what grateful I could at least address the front derailleur issues.
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Old 08-01-13, 04:52 AM
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https://m.parktool.com/blog/repair-he...illeur-systems

this might help
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