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-   -   Adding 26 tooth chainring??? (http://www.bikeforums.net/tandem-cycling/870970-adding-26-tooth-chainring.html)

Ludkeh 02-03-13 05:11 PM

Adding 26 tooth chainring???
 
Today I wanted to change out the 30 tooth chain ring on my 9 speed Ultegra triple for a 26 tooth chain ring. The 26 tooth chain ring is a Sugino Brand with 74mm spacing. The switch over was uneventful, but the smaller chain ring caused the chain to catch and rub on the next larger 42 tooth chain ring pickup protrusions. No matter what I did the chain would rub ever so slightly. It seems like the Sugino chain ring needs a spacer between the ring and crank?

Any suggestions? Where am I going wrong? I really want to go lower than 30 tooth if I can. The chain is a Wippermann chain.

JanMM 02-03-13 08:33 PM

Funny you should ask. I replaced an FSA 30t with a Dimension 28t today and imagine that I hear a faint rubbing (?) sound. The shapes of the two rings looked a bit different so I imagine the chain is a hair closer to the ramps of the middle ring than it used to be. I'll be looking for chainring spacers to move that inner further away from the middle. Eyeballing the three rings they look equally spaced.
Interested in advice from others.

Mr. Fly 02-03-13 11:08 PM

Do you hear the rubbing across the entire cassette or only at the high range (smaller cogs)?

Carbonfiberboy 02-04-13 12:17 AM

I've run different brands of 26T granny rings. They all worked fine, but I settled on a SS granny ring because those small rings get burrs so easily. When went to the 26T, I also went to a 39T middle ring, which makes for easier upshifts. With that combo, I only run the 26T with the four lowest cogs. That works perfectly, and there's no reason to run that ring with smaller cogs on my cassette. The smaller the ring, the greater the chain tension at a given power and thus the faster the chain wear. I also installed a chain catcher, but now I think that might be more trouble than it's worth. I'm using a Shimano 10 speed 39T ring and a Shimano 9 speed 52T ring, which also work together perfectly.

ksisler 02-04-13 10:46 AM

Quote:

Originally Posted by Ludkeh (Post 15232805)
Today I wanted to change out the 30 tooth chain ring on my 9 speed Ultegra triple for a 26 tooth chain ring. The 26 tooth chain ring is a Sugino Brand with 74mm spacing. The switch over was uneventful, but the smaller chain ring caused the chain to catch and rub on the next larger 42 tooth chain ring pickup protrusions. No matter what I did the chain would rub ever so slightly. It seems like the Sugino chain ring needs a spacer between the ring and crank? Any suggestions? Where am I going wrong? I really want to go lower than 30 tooth if I can. The chain is a Wippermann chain.

Recommend not using the granny gear with the three smaller rear cogs! Personally I reserve the granny for use with the two or three largest rear cogs. Or am I missing something with what you are trying to do? To answer your illusion to spacing out the granny mounting a bit; yes I have done that at various times for fickle rings, expecially when not the same brand and the crankset... use or make a small washer under the ring at each bolt. Don't go to stacking up a bunch of them... you will end up wiht broken bolts as there isn't very many threads to spare on a crank bolt.

Ludkeh 02-04-13 11:59 AM

The only rear cassette that it doesn't rub on is the large 32 tooth cassette. It gets progressively worse as I go down the cassette. I've got an OLD Shimano 28 tooth chainring laying around that I might try next. It's steel and doesn't have all that fancy machining on it. I'll let you know how it goes.

As far as washers go. I think all I need is one thin washer for each hole. It wouldn't take much to make it work. My worry was will the chainring be strong enough. I normally only use my granny gear with the large back cogs. As soon as I hear any rubbing I shift up to the next chainring. But, I want the extra capacity for those long climbs.

Chris_W 02-04-13 01:45 PM

When replacing the inner ring on Shimano road triple cranks, I always put 0.5 mm washers behind the new ring. The stock Shimano rings are actually offset a tiny bit, and so the washers make after-market rings line up in the same plane as the stock rings.

joe@vwvortex 02-04-13 01:51 PM

Like previous people have noted - I run the 26 in the front - but only with a 39T middle and 53 big ring. I can use 7 of my 10 rear Campy cogs but rarely go that far down the cluster.

Ludkeh 02-04-13 04:26 PM

After some more investigation I think I've found the best solution! Peter White Cycle has a very good description of the problem I'm encountering.He has a very good explanation on his website. He sells TA Zelito chainrings from France that are fully compatible with my Shimano Ultegra crankset. The chainrings have the correct spacing and require no spacers. A phone call is in order tomorrow! :)

JanMM 02-04-13 06:43 PM

For my slight chain-rubbing-middle-ring-ramps issue with new inner ring, will first try the 1.15mm washers I picked up at Lowes. (Got a digital caliper for my birthday!) Both bike shops I stopped at today only had thicker spacers.

Carbonfiberboy 02-04-13 07:47 PM

Well this is all very interesting to me. I read the Peter White chainring page. While I agree with what he says, I also agree with what he does not say, which is that a 9 speed Ultregra triple FD works perfectly with a 52-39-26 combo. This is on my FSA crankset. Perhaps different 9-speed cranksets have different chainring spacings? Doesn't seem reasonable to me, though.

I dug out my collection of inner rings. They are all flat plates, no fancy features, because they don't need fancy features. The chain simply drops on and is lifted off by the next ring up. Some have counterbores on the inside for the chainring nut, some don't. Some are thicker on the inside for some reason and have deeper counterbores to compensate. They all have more bevel on the teeth on the inside than they do on the outside. IOW their teeth shapes are all the same. The Shimano rings are simple flat plates just like all the others.

Looking very closely at my setup, there is very, very little clearance between the chain on my 26T and my 39T ring, but it doesn't rub. OTOH with my FD set up the way I like it, while in the inner ring my FD cage rubs on the chain in any cog smaller than my 4th from largest. As I say, I'm not running the stock 9-speed 42T middle ring, since that would be a 16T shift from the 26, which seems a little large. Be that as it may, the Shimano and FSA stock 9-speed 30T inner rings are simple flat plates.

So I don't see how the chain on the inner ring can rub on the middle ring on some bikes but not on others, unless there is a difference in the crankset spacings. Perhaps someone can explain.

I suppose it's also possible that the OP's middle ring is badly burred and that's the problem. The middle rings on my tandem crankset don't seem to last as long as those on my singles. They get burred or the pins break off and I toss them. I suppose it's also possible it's a chain problem. I run nothing but Shimano Ultegra 9-speed chains.

Ludkeh 02-05-13 06:17 PM

Could be the Wippermann chain that I'm running is a smidgeon thicker than your Shimano chain which is causing the problem.Like you said there is very,very little clearance and only a small difference of a few mm is enough to cause problems. I'll let you all know how it turned out.

djembob02 02-06-13 09:06 AM

I would recommend your original hunch in the OP, to add spacers, though I would use chainring spacers rather than store bought washers (simply for the precision of getting the right diameter (internal and external). It is very common to need to add spacers when customizing your chainring set. It does not affect the performance in any negative way. It would only be a problem if somehow, even with spacers, it was still rubbing; or if the spacers somehow made the distance too great for your front derailleur to get to all three chainrings. I doubt of these would happen.

ksisler 02-06-13 12:56 PM

Second thought; might be a good idea to check the chainline when in big ring + smallest cog. Maybe lay a meter stick across the outer chainright and swing it down to the cogs... It wouldn't take much of a misalignment to cause noise. Might be that the bottom bracket spindle is just a bit short on the right side or maybe dialed over to the left side a bit (if its the adjustable one).

Ludkeh 02-06-13 03:35 PM

Good idea ksisler! I'll check that. I think the final solution will be a thin washer between the chainring and crank. As a previous poster mentioned, I want to get well machined thin washers that just fit and don't stick out past the spindle spider. I tried it with some old washers I had and everything worked fine. It let me use the 4 large cogs without any rubbing. Once I got to the 5th cog you could hear a hint of rubbing. By that time I should have shifted into my middle ring anyway! So I think all will be good with the shims.


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