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Old 01-31-09, 07:41 AM   #1
deweyhtucker
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Change to a bigger ring on a Compact Crank

I have installed a new Shimano R600 compact crank (34-50). It has a CBD of 110mm. I would like to replace the 50T ring with a 52T or 53T. Any thoughts?
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Old 01-31-09, 07:55 AM   #2
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What are you using for a shifter? 34 to 53 is a pretty big jump. I'm thinking you'll be pushing your derailleur and shifter capability so it'll probably be a pretty slow shift.

The other knock on 50/34 compact cranksets is the lack of overlap gears. Essentially that restricts your choices of when you can make the front shift and forces you to make 2 or 3 rear cog shifts at the same time. With that big jump between front chainrings it might turn out to be a PITA to ride.
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Old 01-31-09, 07:59 AM   #3
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+1

Try this to see what kind of difference it will make for you: http://www.sheldonbrown.com/gears/
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Old 01-31-09, 08:03 AM   #4
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9 or 10 speed?
The problem is that all the modern road rings larger than 50t will have a 130 bcd.
Sugino does make 110 bolt pattern 52-53 tooth rings but they are for 8 speed.
Theoretically it's possible but good luck finding what you want.
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Old 01-31-09, 08:06 AM   #5
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I agree with RG's comments that the gearing gap would be awfully big and the shifting could be sluggish.

However, there are plenty of 52 or 53T chaintings with a 110 mm BCD available so, if you are aware of the drawbacks, go ahead. Here is one source: http://sheldonbrown.com/harris/chainrings/110.html

BTW, what is your current cassette's smallest cog? If it's a 13T, a cassette with a 12 or 11T cog might give the higher top gear you want. A 12x50 is 112 gear-inches and an 11x50 is 122 gear-inches. Both are very big gears and seem to satisfy the pros.
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Old 01-31-09, 09:23 AM   #6
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I know it wasn't your question, but I too am puzzled as to why you would want bigger than 50? A 50t front ring is one of the best recent little innovations in road cycling. I know a few very good Cat1 racers around here (i.e. stronger than us) that have switched to 50. I love it because it is more flexible for all kinds of road riding.
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Old 01-31-09, 09:29 AM   #7
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No opinion but I have a SR 53 110 I'd be happy to trade you for a 50. It's used but decent.
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Old 01-31-09, 10:00 AM   #8
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Thanks,
I was just thinking outside the box. I was afraid that shifting might be a problem, and was interested if anyone had attempted such a project. My bike is a 1996 Treck 5000 oclv 8 speed that was purchased about 2 months ago. I went to a compact crank for the lower 34T ring. I've installed a 12-32 cassette that I made up from a combo of manufactured cassettes, its ratios are like the Shimano "P", but I could not find the Shimano, and Nasbar did not have their 12-32 cassette. I know Forte has one, but do not know anything about the brand. I live in the Smoky Mountain area, so need for low gears. Front & rear shift good, so am satisfied with results. Since the bike had a 39-53 Crankset, I was thinking about going up from the 50T compact ring. The FD is a braze-on Shimano 600 Ultegra bottom pull. I've been using Sheldon Brown's "gear calculator" in getting to where I am now. I'm a newbie to bicycling so looking for input. I'm not interested in “re-inventing the wheel”. I've built and raced boats, motorcycles, and cars. Have been successful by winning in these divisions by beating factory race teams, and have even broken a world's speed record which stood for over 20 years. So I have always been willing to try something different, and that's the reason for my original question about going from a 50T to a 52T or 53T. I have a respect for the people on this forum, and appreciate your input.
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Old 01-31-09, 10:33 AM   #9
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I ran my touring bike with a 50/34 compact shifted by a Campy Neuvo Record front derailer. It worked, but I had to be careful, the chain did have a tendency to drop at inopportune times.
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Old 01-31-09, 10:46 AM   #10
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FSA has a 52 tooth outer ring and they have a 36 or a 38 inner chain ring for the compact. Other manufacturers must also carry different chain rings.
It may be easier to change chain rings than cassettes.
Just a thought as I am still learning what works for me in this sport.
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Old 01-31-09, 10:48 AM   #11
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I'm not positive on 600, but Shimano recommends a tooth difference of only 15t between chainrings for a 6500 fr. der. In practice, this works just fine with the 16t dif of a standard compact, but with a 53t, you would have to set the cage high enough that the chain would rub on the flat perpendicular part of the fr. der. cage in low in the front and probably about half of the higher gears in back. Furthermore, even the long cage shimano road r. ders. have a capacity of only 37t (cassette tooth count difference + chainring tooth count difference,) and you're already at 36t w/ your current configuration. In short, It could be made to work, but the aforementioned "lack of overlap gears" would be seriously exacerbated by the inability to use all the gear combinations that would otherwise be attainable with a system composed of strictly compatible components. That being said, I have an older braze-on 105 fr. der. and short cage DA r. der. that work fine with my 34/50 R4550 compact crankset and 12/27 cassette as long as I'm careful, so if you're willing to deal with a slightly finicky drivetrain, go for it!
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Old 01-31-09, 10:54 AM   #12
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I'm not positive on 600, but Shimano recommends a tooth difference of only 15t between chainrings for a 6500 fr. der. In practice, this works just fine with the 16t dif of a standard compact, but with a 53t, you would have to set the cage high enough that the chain would rub on the flat perpendicular part of the fr. der. cage in low in the front and probably about half of the higher gears in back. Furthermore, even the long cage shimano road r. ders. have a capacity of only 37t (cassette tooth count difference + chainring tooth count difference,) and you're already at 36t w/ your current configuration. In short, It could be made to work, but the aforementioned "lack of overlap gears" would be seriously exacerbated by the inability to use all the gear combinations that would otherwise be attainable with a system composed of strictly compatible components. That being said, I have an older braze-on 105 fr. der. and short cage DA r. der. that work fine with my 34/50 R4550 compact crankset and 12/27 cassette as long as I'm careful, so if you're willing to deal with a slightly finicky drivetrain, go for it!
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Old 02-04-09, 10:58 AM   #13
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I emailed Sheldon Brown that "I have installed a new Shimano R600 compact crank (34-50). It has a CBD of 110mm. I would like to replace the 50T ring with a 52T or 53T. Will the TA 110 Outer Chainring in 52 Teeth (CRT052), or 53 Teeth (CRT053) work, and any potential shifting problems? Any thoughts?"
His reply, "Yes, the TA rings will work. Shifting crispness may suffer slightly depending upon the shifters used. But the shifting performance will still be perfectly acceptable unless you are in elite level competition."
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Old 02-04-09, 11:08 AM   #14
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Quote:
Originally Posted by deweyhtucker View Post
I emailed Sheldon Brown that "I have installed a new Shimano R600 compact crank (34-50). It has a CBD of 110mm. I would like to replace the 50T ring with a 52T or 53T. Will the TA 110 Outer Chainring in 52 Teeth (CRT052), or 53 Teeth (CRT053) work, and any potential shifting problems? Any thoughts?"
His reply, "Yes, the TA rings will work. Shifting crispness may suffer slightly depending upon the shifters used. But the shifting performance will still be perfectly acceptable unless you are in elite level competition."
Recently? Who is your ISP and what is Sheldon's new email addr? My ISP won't route messages that far.
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Old 02-04-09, 11:15 AM   #15
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Quote:
Originally Posted by deweyhtucker View Post
I emailed Sheldon Brown that "I have installed a new Shimano R600 compact crank (34-50). It has a CBD of 110mm. I would like to replace the 50T ring with a 52T or 53T. Will the TA 110 Outer Chainring in 52 Teeth (CRT052), or 53 Teeth (CRT053) work, and any potential shifting problems? Any thoughts?"
His reply, "Yes, the TA rings will work. Shifting crispness may suffer slightly depending upon the shifters used. But the shifting performance will still be perfectly acceptable unless you are in elite level competition."
Holy crap...they finally got internet access in heaven!
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Old 02-04-09, 01:45 PM   #16
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Dewey-
Try one of the 11T cogs you have laying around with the 50T first.
that will give you 50/11 or a 4.54 ratio.
A 53/12 will be 4.46, which is pretty close.

There's a reason they make road triples!

What RDER are you using? You currently have 36T of chain wrap. Going to a larger ring means you'll have to lengthen the chain slightly more.
IS the chain "sagging" when on the 34-12 combo? IF so, it'll get worse fast.

Last edited by Bill Kapaun; 02-04-09 at 01:59 PM.
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Old 02-05-09, 08:35 AM   #17
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The email I sent to "Sheldon Brown" was sent to order@harriscyclery.net and that is who responded. Bill, I don't have any chain sagging. I'm using the Shimano RD-580 SGS rear derailleur. After checking out your suggestion about switching the 12T to an 11T it is true that 11T/50 is as high as 12T/52. Since I have an 11T, I'll go that route. It's no cost, and simple. Thanks.
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