mgoltsman

So I have a 2x9 Sora road bike that until today had a 12-27 cassette. I finally broke down and decided that 11-32 will be more realistic for my lousy shape. Swapped out the cassette (also Shimano), tried shifting with the bike suspended - everything feels smooth, all gears are immediately accessible. Took a quick ride around the block - all smaller gears have a definite growl. Still accessible, no shifting errors - but definitely doesn’t feel like the buttery original cassette.

Do I need to re-adjust the derailleur after replacing the cassette? I presumed that the same manufacturer with the same number of gears would fit identically. No cassette replacement videos on YouTube mention the need for retune… could it be just new cassette needing to be “broken in”? Kinda reluctant to put a dozen miles on this setup to “see what happens”. Any ideas/suggestions would be appreciated.

Rolla

How's the chain length and condition?

DiabloScott

Yeah probably the B screw at least. Also maybe chain length is too short now. Also maybe chain was worn out/worn in to your old cassette and you need a new one anyway.

mgoltsman

Chain is original, but likely well under a thousand miles. Certainly stretched more than before by the larger gears (in fact I worried the derailleur might be too short) but the sound only occurs on smaller gears - so I imagine chain length shouldn’t be an issue?

mgoltsman

Huh. I had a Sora tuning manual somewhere. I’ll try that first before swapping out the chain…

Rolla

Yeah, hopefully. But going from a 27 to a 32 might necessitate a couple more links. And as DiabloScott pointed out, the B-tension might need adjustment. Is there tension on the rear der when you're in small/small combo?

dabac

Smaller sprockets means fewer teeth engaged, fewer teeth sharing the load. It may well be a chain wear issue.

Kai Winters

You should always check the hi/low limit screws...never count on a replacement cassette being the "exact" replacement. It may, sounds likely, be a fraction off causing the chain to rub the gears.
check the alignment of the limit screws...hi/low and "B".
Check and if necessary adjust the cable tension for the rear derailleur. That should eliminate the "growl" which is likely chain rub.
I always check the rear derailleur hanger first but it is unlikely you have an alignment tool. If the above doesn't help, take it to a shop and have them check the rear der. hanger then start over with the limit screws and the cable tension.

KerryIrons

Yes, but why the "may" question. Just measure the darn thing and know if it is beyond 0.5% elongation. If it isn't, then the chain and new cassette cogs will wear in pretty quickly and likely the noise will abate.

mgoltsman

SO.

Looks like I found my problem. The cassette I installed is a Shimano CS-HG-900. It’s a HyperGlide MTB cassette. I installed it on a road bike with a Sora derailleur. It is probably close enough to hit all gears, but far enough to cause vibrations on the smallest gear where the load is highest.

So, a question for the experts - am I restricted to Sora cassettes, or is it possible to find cassettes that are compatible? Largest 9-speed Sora cassette appears to be 11-30. I could live with that, but more teeth is better.

MudPie

1. I doubt the mountain cassette matters, as only the chain interfaces with the cassette, not the derailleur. Dimensionally, chains (edited) * of the same speed* are created equal.

2. You're not limited to a Sora cassette. Personally, I run SRAM cassettes, Ultegra derailleurs & chainrings, and KMC chain. They all play nice together.

mgoltsman

Good to know. I read somewhere that 9, 10, 11, etc. chains have different widths, so was wondering if the indexing distance varies between derailleur families, brands, or road/MTB products. Everything I read so far indicates that MTB cassette are just marketing speak for cassettes with larger range, and overall I should have no compatibility problems with the setup I created. Which, I guess, means that i better work harder on finding the correct indexing position.

Or maybe HG-900 is just less smooth than the Sora cassette I’m replacing and I will have to get used to the new growl.

MudPie

Let me clarify my statement about chain dimensions. You are correct. I meant to say chains of a given speed are dimensionally the same. For example, 9 speed Shimano, SRAM or KMC chains are compatible. 9 speed chains are not compatible with 10 or 11 speed chains.

timdow

9-speed road and mountain are the same. This is not the problem.

When you are in the largest cog in the cassette (smallest gear), you should be in the small ring in front. If this is the case, it's probably not the chain being not long enough. This would be a problem in big-big combination, but that is a gear combo that you shouldn't be using, anyway.

This is what I suspect the issue is:
When in biggest cog on the cassette and the small ring in the front, is the chain squished between the derailleur pulley and the cassette with no gap? This is why folks are asking you about the "B" screw, which will adjust this.

Does cranking the "B" screw fix the issue?

mgoltsman

Right, I avoid going more than one past the middle without switching chainrings - so not likely to hit chain size limitation. Though I think I accidentally got to that position while tuning the indexing, and the chain didn’t break.

The issue shows up when I use the large chainring and becomes more pronounced as I shift towards the smallest sprocket (highest gear?) on the cassette. So the derailleur is way too far from the cassette to pinch the chain. That’s why I suspect it’s either indexing slightly off or the actual feel of a different cassette.

B screw is a bit of a mystery to me. It doesn’t seem to be doing anything! The YouTube videos show the derailleur visibly and obviously moving towards and away from the cassette sprocket as the B screw is adjusted. I have completely removed the B screw (by mistake), then screwed out all the way in to the stop, and I have to talk myself into believing that I can barely see the derailleur roller moving up and down. Still trying to figure out what’s going on there… But the chain isn’t pinched by the roller to the best of my understanding, and it would happen in low gear anyway, not in high gear where I actually get the growl.

timdow

OK so I have misunderstood... Your problem is in the smaller cassette cogs. If this is the case, most common cause is derailleur adjustment, although cable binding and/or lubrication could be in-play. Yes, your indexing may be off.