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Replacing the inner chainring with a different size - Shimano 5700 Compact

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Replacing the inner chainring with a different size - Shimano 5700 Compact

Old 08-10-15, 12:13 AM
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kmcrawford111
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Replacing the inner chainring with a different size - Shimano 5700 Compact

Hello Everyone,

I would like to try replacing only the inner chainring on my crankset, which is a Shimano 105 5700-series compact. I understand that my BCD is 110mm. What I would like to be able to do is install a larger ring there, something like 38 or 39 tooth. I know I could get the standard double crankset, but it would be nice to be able to swap the 34-tooth ring back in if I want to later - plus changing just one ring would be cheaper.

It seems that this isn't an option with Shimano parts, but does anyone else make chainrings that are compatible with my drivetrain? I see that other manufacturers make rings in the teeth and BCD I am looking for. What I don't know is whether they're compatible with what I have now - I want to be able to use my front der.. still.

Many thanks.
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Old 08-10-15, 12:29 AM
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Big pain, small gain, IMHO.
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Old 08-10-15, 02:48 AM
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Vuelta offers what you want and it won't cost much at all. I have some chainrings from them and they're perfectly fine.

SE Chain Ring, 34 - 60T, Bolt Center Diameter: 110mm
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Old 08-10-15, 05:48 AM
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If you look at OEM rings, they are matched in sets of inner and outer teeth. This is done to optimize shifting as the best tooth profile, ramps, and lift pin locations on the outer ring depend on the relative phase between the inner and outer ring going around the ring. Non-matched rings will certainly work, just not as well.
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Old 08-10-15, 08:31 AM
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I'm probably not the right one to answer as I use un-ramped/pinned chainrings. That said, if you are only swapping out the inner ring, I would think you can find a lot of 36/38/39/40 inner chainrings that will work. Will they be matched? No. But we are talking about an inner chainring so I really don't see an issue.

Go to ebay and search for a 38t 110mm. You can find SRAM and Sugino for less than $20.

John
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Old 08-10-15, 08:37 AM
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Your FDER is optimized for your current set up.
Likely, it will jam into the larger inner ring unless you raise it. That would likely result in poorer shifting.
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Old 08-10-15, 08:44 AM
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Originally Posted by Bill Kapaun View Post
Your FDER is optimized for your current set up.
Likely, it will jam into the larger inner ring unless you raise it. That would likely result in poorer shifting.
That's a good point! Look at the inner blade of your front derailleur. If it's very deep it will hit your brand new 38 or 39 tooth chainring when you try to shift up to the 50.
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Old 08-10-15, 10:29 AM
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Yikes!

Based on these comments, I can't imagine how anyone was able to shift with a 39/53 setup back in the 80's.

John
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Old 08-10-15, 10:43 AM
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OMG. Somebody asks a simple question about deviating from the stupid norm of the 50/34 gearing and gets pounded with everything but the answer.
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Old 08-10-15, 10:59 AM
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The answer is to go buy a 38t/39t 110mm chainring. Mount it, adjust the derailleur and ride.

John
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Old 08-10-15, 12:12 PM
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the inner of a double does not need ramps and pins, the middle of a triple may.

changing the inner may not even need a FD adjustment . jump in and Swim.
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Old 08-10-15, 12:33 PM
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Originally Posted by 70sSanO View Post
Yikes!

Based on these comments, I can't imagine how anyone was able to shift with a 39/53 setup back in the 80's.

John
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Old 08-10-15, 12:42 PM
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Poked around on the Shimano site and it looks like they spec'd the same FD (5700) for standard and compact cranks, the 5703 for triples. As long as your bike doesn't accidentally have the triple FD installed, you should be fine with the 38/39T inner ring.
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Old 08-10-15, 01:38 PM
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Originally Posted by 70sSanO View Post
Yikes!

Based on these comments, I can't imagine how anyone was able to shift with a 39/53 setup back in the 80's.

John
dig out a front derailleur from the era and compare it with one from today. Modern double front derailleurs don't look very much different but triple front derailleurs frequently have a deeper inner blade and won't shift close ratio chainrings. that's why I suggested the OP check his front derailleur before spending any money.
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Old 08-11-15, 10:23 PM
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Thank you all, for responding. I like those Vuelta rings that Eric S. linked to - they even look like they'd fit with the look of 5700. I see they also offer ramped and pinned rings, but they are listed as working with only up to 9-speed. Must be thicker, I guess.

I rarely use my FD - it's not even connected right now, serving only as a chain guide - so losing some front shift performance is not a big deal. 95+% of my riding is regular commuting routes, and I like the concept of using just the 39T ring. This route will allow me to swap the 34T back in if I need it for a hilly event ride, and I can still use my 50T ring if I need to by the same token.
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Old 08-12-15, 05:53 AM
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Quite a few bikes I'm shopping come mid compact, which is 52/36 ? So the fd must work fine with that anyway. The 105 bikes are often 50/34 and the next grade up is often ultegra and mid compact.
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