So, long story ... I wanted to get some lower gears to climb with since I bought my bike years ago in Ontario but now live in BC in the heart of the Rockies. I switched my 9spd 13-25t cassette to a 9spd 11-28t cassette and also switched my crank to a smaller 34t ring on front.

My rear derailleur is a Shimano 105 5800 small cage , so I think it should be able to handle a 28t cog. I measured my chain against my old chain and added links to account for the extra 3 Teeth on the 28t cog. After adjustments, all shifting is OK except the 28t cog which makes slight contact with the derailleur cage wheels.

If the front is on the small 34t ring, this is worse. I think my chain may be too long/short Or perhaps I need some adjustment on the B screw?

Any suggestions are welcome. This is my first major job on my bike.

Thanks.

Larry

I always size new chains to the bike, and NOT to the old chain. Reason being I rarely know if the old chain was sized just right or a tad off in either direction.

With that said, contact between pulley wheel and sprocket is usually fixed by adjusting the B-screw.

Points taken ... So what's the best way to size the chain to the bike? I have seen a few different calculations and the rule of thumb - put it on both big cogs, not through the derailleur + 2 half links, but not sure if that is the way to go.

I tried fiddling with the B screw but then it got dark and I wasn't quite sure of the correct procedure. Any pointers on B screw adjusting?

Thanks,
Larry

Different people prefer different methods.

I don't do it often enough to require the absolute peak in efficiency.

Never bothered with those.

Usually I do about that. But I run the chain through the derailer while I'm at it. Tension the chain. Check the angle of the derailer, notice where to break the chain and go at it.

Once I faffed about with pieces of string, or shallow hooks of old spokes to hold the chain together as I worked on it. Wasn't really worth the time.

A Half link is a different beast. see here:https://www.google.se/search?hl=sv&s...75.XfMDckje7co
Normal chains consist of alternating inner and outer plates. Whether inner or outer plates, one link is defined as a part holding a pin at each end.

If the top pulley doesn't clear the sprocket, turn the B-screw in. Some setups may requre replacing the B-screw with a longer one. Any with the correct thread will do. Another option is to take the screw out entirely, and thread it back in reverse. The head will act as extra length.

Adjust the B-screw for clearance while on the biggest cog, then check it across the cassette; on occasion it will need to be readjusted to clear all of the cogs. This will often occur in a situation like yours where a cassette with a wider range is fitted. The cage moves down and over at an angle optimized for a certain cassette tooth range and a different range may necessitate a different adjustment to clear.

Probably has nothing to do with chain length. Use the B-screw adjustment to push the upper jockey wheel a little further away from the cassette so it will clear in the 28T.

Thanks for all the replies. I'll have another go at the B-screw this evening. Wish me luck.

How are you making an 11 speed RD work with a 9 speed cassette? That is not a compatible combination.

Maybe the missing info is that the OP has friction shifters... Bet not though.

The compatibility aspect aside the first thing I thought of was that the OP did two changes which will make pulley knock more likely. Both a larger rear cog (and that it's about at the der's limit of size, why do we push the limits of der capacity and then question the results) and the smaller ring will make the upper pulley ride closer to the large cog's underside.

When sizing a chain and if the der capacity hasn't been exceeded I place the chain on the small/small combo and see how long the chain can be and not have any chain/cage contact or droop. then I add a link. Cut the chain here and trial fit on the big/big. Then see how many links can be removed before the cage is too far wound out. My final cut is somewhere between these two lengths. Yes it's a judgment thing. But I would rather have one more link then minimal then run at the shortest length limit. Andy.

Not that I am aware of. This bike, 2010 Devinci Silverstone SL3, came with 13-25T cassette 9Spd Shimano 105 5800 and was working fine. Just having difficulty with adjusting the new larger 28T correctly.

OK, I'm going to by psychic here and tell you that your RD is really a 5500 9spd or 5600 10 spd, not 5800 then...

That means you have exceeded the capacity of the RD which is only 27 teeth as the largest cog and a total capacity of 29 for the SS. A GS version of the 5500 still has a max cog size of 27 but just has a larger capacity.

As others here have asked... "why do we push the limits of der capacity and then question the results?" I can't answer that question.

Tiagra shifter - indexing which works fine but it could be a combination of B-screw and chain a bit too long. First will try the B-screw.

I suspect you have 5600 105 parts. 5800 wasn't available back in 2010. Andy.

Couldn't you do some trickery with the DR cable clamp to compensate for different pull of the 11 speed DR? That's the only incompatibility right?

Yes, could also be the 10spd 5600 RD with the 9 speed Tiagra shifters, that combo worked.

How could I tell for sure? The spec sheet for my bike clearly states 5800. Vélos DEVINCI

As the other Andy said, 5800 didn't exist then.

Take a look at the back of the RD. Shimano stuff is always clearly stamped. You will see FD-5xxx somewhere there.

spec sheet for my bike: Vélos DEVINCI

2009 model came with Ultegra 6600 RD. SILVERSTONE SL3

Unless I'm trying to shave grams, I use as long of a chain as I can get away with. A too-long chain might rattle in some combinations or be slightly more prone to falling off -- NBD. A too-short chain can break parts if you shift into the wrong combination.

And with modern chains that require special pins or quick-links to be closed safely, I'm reminded of something my old barber always told me, "I can always take more off, but I can't put it back."

My 2013-2014 Shimano catalog only goes up to 5700.
The 2015-2016 catalog lists the 5700 & 5800.
I guess Shimano lies?

You are the experts. I will check the back of the RD but I am sure that you are correct. I found a link for a 'printer ready' spec sheet which was easier to read (bigger) for these aging eyes and it shows 5600.

So ... assuming it is a 5600, is the 28T within spec and can I make it work with the 28T rear and 34T front?

Thanks.

I found the spec. 27T is the max. Is there any way to get around this limit? I am a little miffed at the bike shop that sold me these parts - they should have known better as they did look at the spec sheet of my bike's components.

If the 5600 can't be made to work, will another model work on the 9spd that will work with the current shifters - tiagra 4500?

You might as well ask "What's the best religion?" but here's how I do it:

1. Wrap your chain around your biggest front chain ring and your biggest rear cog.
2. Figure out the shortest place that you could rejoin your chain. There's wide links and narrow links and you need one of each. Quick "master" links always take the place of a wide one.
3. Add one inch of chain (2 links onto that).

That will give you the shortest chain that will safely work with your gear combination. Your derailleur arm will be pulled almost straight forward in the big/big combination.

The expert WRT a bike's spec is the person owning the bike. My comment about pushing a component's capacity to it's limits (or slightly beyond) relates to your question of "can I make it work"?

IIRC the 5600, short cage, rear der has a 27T cog max spec. and a wrap of about 29T. The 11-28 cassette and the 34-"50" (not yet mentioned but assumed as is the typical compact crank set up) both exceeds the cog size and the wrap ( at 33T). So will it work, sure but there can be some issues that might crop up.

The rear der's ability to wrap the chain in every combo might not work, however limiting the actual combos in use can mitigate this. Pulley knock can happen. But trial and error chain length choice and "B" screw adjustment can also work around this.

So my answer is sure it can work but with more set up discovery and solving as well as some rider shifting behavior limits. Andy.

I found the spec. 27T is the max. Is there any way to get around this limit? I am a little miffed at the bike shop that sold me these parts - they should have known better as they did look at the spec sheet of my bike's components.