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changing chainrings

Old 11-23-21, 07:21 AM
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dirtydozen
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changing chainrings

Hello,

I currently have a shimano 105 5700 triple chainset 50-39-30 with an 11-34 cassette.
According to the derailleurs capacity, i should have for a maximum a 32T cassette but this 34 worked well the few times i had to use it.

I would like to be sure that if I buy a 53T and a 34T chainring to make a triple 53-39-34, it wouldn't cause any problem in the capacity side of things.
I could change the 39T in something like a 42T to match the wears and to have a consistent spacing between each rings if that can help the FD.
I could also later on when changing the cassette (i believe i can get more km's out of this cassette) go for a 11-32T one

Thanks for your attention
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Old 11-23-21, 08:11 AM
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That is a lot of work and cost for such a minimal change in your low gear. Any change your big ring from 50 to 53? If you are that strong that a 50-11 isn't a high enough gear, then hats off to you. I don't think I have ever been down a hill steep enough to turn a 53-11. You'd be going like 50mph!
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Old 11-23-21, 10:15 AM
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You'd be better off with a smaller range cassette like 11-30. This will give you closer spacing to fine tune your cadence and still have the same range. This would even allow you to throw that 53 chainring on (do you often find yourself pedaling at 40+ mph?) without having to get a longer chain, because the chainwrap will still be about the same. 53/39/30 is a common setup on triples.
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Old 11-23-21, 01:10 PM
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Without knowing more about how you ride and what terrain conditions I tend to agree with urbanknight . With a 3x front I'd want a more closely spaced rear. Only exception for that would be if I rode hills where I absolutely had to have that 32 or 34 cog for getting me up them. And that's hard for me to imagine with a 30 on the front unless you regularly ride miles of 8 to 10 percent grade.

As for the 53 ring or even a 52, I'd have to ask if you are in your 11, 12, or 13 cog and the 50 ring for a lot of your riding, then maybe you do need something bigger. If it's only for wanting more pedaling time going down the backside of a hill, then maybe really think about it more if only for that. Though I like more time before spinning out going down hill. But worth the cost?

Also, if you are out of the specs for your DR's, then while it might work for many, it might not work for you. Differences between your bike and theirs still will make your out of spec changes an experiment.

Last edited by Iride01; 11-23-21 at 01:13 PM.
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Old 11-23-21, 01:44 PM
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I have the same triple chainrings and have wondered why they went with a 50 instead of something bigger. Granted I only use this setting (50/11) on flats and downhill, I do find myself spinning out.

Worth the cost? That question dooms most changes to bike gear so I donít answer it 😁
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Old 11-23-21, 02:21 PM
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i have nearly teh same setup and if inclined enough i'd be making my big chain ring bigger too. but honestly, there are only a few hills where i would really be able to take advantage of having it.
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Old 11-23-21, 05:51 PM
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I can find cheap chainrings, this operation wouldn't cost me that much.
And actually yes sometimes the 50 isn't enough, i have a lower cadence than average, i've worked on it but i'm faster that way.
Having a 30T chainring is a bit useless, 34 would be enough, and with bigger rings i would be more often mid cassette.
Last but not least, the whole bike components are black except the right part of the chainset that is gray, since i got the bike i knew it had be changed at some point down the line haha.
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Old 11-23-21, 06:02 PM
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Originally Posted by dirtydozen View Post
I can find cheap chainrings, this operation wouldn't cost me that much.
And actually yes sometimes the 50 isn't enough, i have a lower cadence than average, i've worked on it but i'm faster that way.
Having a 30T chainring is a bit useless, 34 would be enough, and with bigger rings i would be more often mid cassette.
Last but not least, the whole bike components are black except the right part of the chainset that is gray, since i got the bike i knew it had be changed at some point down the line haha.
Itís funny you say the 30 is useless. I do a lot of hill riding and find I go through all three chainrings regularly. I use the 30 quite a bit. I probably use the 50 least of all
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Old 11-23-21, 06:58 PM
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Originally Posted by Symox View Post
Itís funny you say the 30 is useless. I do a lot of hill riding and find I go through all three chainrings regularly. I use the 30 quite a bit. I probably use the 50 least of all
Well last time i went out in the mountains i used the 30x34 but it was so easy to spin and i was very out of shape as well.
A 34T ring would be enough for the next times i'm doing serious climbs.
I'm usually on the 50, and i switch to 39 riding uphill
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Old 11-23-21, 07:00 PM
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Originally Posted by dirtydozen View Post
I can find cheap chainrings, this operation wouldn't cost me that much.
Except that you're going to need a new chain and you don't know if your RD can handle the spread or not.
That being said, looking up the specs of your RD, a 53/42/34 11-34 combination only exceeds the chainwrap by 2, so you have a good chance of it working. Only one way to find out!
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Old 11-23-21, 10:27 PM
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A 39x34 is a pretty low gear without ever going in to the small ring up front. One of my bikes has a triple and I don't go into the 30 unless I can't climb something in the 39 and I only have a 28 in the back. And I'm 67 and fat.
Also, a 50x11 is high enough for most situations. I have a 52x11 on that bike and I don't use it that much. My other bike has a 50x12 and that's high enough most of the time.
All I'm saying is you already have lots of gears to chose from. If you want to try switching rings, go for it.
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Old 11-24-21, 06:47 AM
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Originally Posted by urbanknight View Post
Except that you're going to need a new chain and you don't know if your RD can handle the spread or not.
That being said, looking up the specs of your RD, a 53/42/34 11-34 combination only exceeds the chainwrap by 2, so you have a good chance of it working. Only one way to find out!
The chain is too old anyway, I have to replace it soon. That's why i thought it could be the right time to find some new rings actually.

Originally Posted by big john View Post
A 39x34 is a pretty low gear without ever going in to the small ring up front. One of my bikes has a triple and I don't go into the 30 unless I can't climb something in the 39 and I only have a 28 in the back. And I'm 67 and fat.
Also, a 50x11 is high enough for most situations. I have a 52x11 on that bike and I don't use it that much. My other bike has a 50x12 and that's high enough most of the time.
All I'm saying is you already have lots of gears to chose from. If you want to try switching rings, go for it.
Yes you are right, I know it's not going to change much and that my gearing is fine at least 90% of the time.
I just wanted to know if it would work (worst case scenario without using the 34T cog)
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Old 11-24-21, 07:07 AM
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I think the inner chainring BCD is 74mm. Make sure you can find a 34T 74BCD chainring made for the inner/3rd ring position. Otherwise, you'll have spacing issues.
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Old 11-24-21, 11:59 PM
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Is 50x11 too small for you? That's a very heavy ratio.. I would think just tucking would be fine if you find yourself spinning out on the downhill. I also don't see why you're trying to ungranny your tripple. On my bike with a tripple it bottoms out at a 28x34 which while ridiculously low sees use. I feel like you're screwing yourself by changing your setup
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Old 11-25-21, 03:20 AM
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LarrySellerz not everyone has the same motor, some of us donít need the low-low gears to up hills, and some of us spin out 50x11. BEar that in mind before you offer advice opinions about gearing based on your abilities. I admittedly struggle with this when people ask how to build a Franken-geared bike with sub-20 gear inches on the low end.

Originally Posted by dirtydozen View Post
Hello,

I currently have a shimano 105 5700 triple chainset 50-39-30 with an 11-34 cassette.
According to the derailleurs capacity, i should have for a maximum a 32T cassette but this 34 worked well the few times i had to use it.

I would like to be sure that if I buy a 53T and a 34T chainring to make a triple 53-39-34, it wouldn't cause any problem in the capacity side of things.
I could change the 39T in something like a 42T to match the wears and to have a consistent spacing between each rings if that can help the FD.
I could also later on when changing the cassette (i believe i can get more km's out of this cassette) go for a 11-32T one

Thanks for your attention
Capacity is NOT the largest cog your derailleur was designed to accommodate (which for Shimano is ALWAYS conservatively specíd).

Addressing the largest cog issue first, turning the b-screw will often allow use of a slightly larger cog, just how much larger is not universal from RD to RD, so you really need to do some research and/or experimentation. One word of caution, a tooth or two larger is usually not an issue, but 3 or more than lead to shift issues, first smoothness and potentially also skipped or missed cogs especially as you get into the higher end (smaller cogs) of the cassette.

Capacity is a function of how much chain the derailleur can wrap (rear), or how large of a gap between chainrings it can manage (front). The wrap on the rear is a combination of tooth difference from large to small on the cassette and the difference between large and small chainring. So, going to a 53 and 34 (from a 50 and 30 respectively) should be no issue, though you may need a slightly longer chain.
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Old 11-25-21, 03:41 AM
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Current low gear is 30/34 (1:0.88), high gear 50/11.

Proposed new low gear 34/34 (1:1) or 34/32 (1:1.06) and 53/11 high gear.

I suggest simply getting an other cassette. 11-30 or 11-28. That brings a 30/30 (1:1) or 30/28 (1:1.07) low gear and a 50/11 high gear. Almost exactly the same as proposed.

Unless you absolutely need the slightly higher high gear, replacing the cassette is likely cheaper and easier.
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Old 11-25-21, 11:42 PM
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Originally Posted by Badger6 View Post
LarrySellerz not everyone has the same motor, some of us donít need the low-low gears to up hills, and some of us spin out 50x11. BEar that in mind before you offer advice opinions about gearing based on your abilities. I admittedly struggle with this when people ask how to build a Franken-geared bike with sub-20 gear inches on the low end.



Capacity is NOT the largest cog your derailleur was designed to accommodate (which for Shimano is ALWAYS conservatively specíd).

Addressing the largest cog issue first, turning the b-screw will often allow use of a slightly larger cog, just how much larger is not universal from RD to RD, so you really need to do some research and/or experimentation. One word of caution, a tooth or two larger is usually not an issue, but 3 or more than lead to shift issues, first smoothness and potentially also skipped or missed cogs especially as you get into the higher end (smaller cogs) of the cassette.

Capacity is a function of how much chain the derailleur can wrap (rear), or how large of a gap between chainrings it can manage (front). The wrap on the rear is a combination of tooth difference from large to small on the cassette and the difference between large and small chainring. So, going to a 53 and 34 (from a 50 and 30 respectively) should be no issue, though you may need a slightly longer chain.
50x11 at 140 rpm is like 50 mph lol, who needs something heavier than that?
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Old 11-26-21, 01:05 AM
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Originally Posted by LarrySellerz View Post
50x11 at 140 rpm is like 50 mph lol, who needs something heavier than that?
No one is spinning 140rpm, not even Lance in his prime.
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Old 11-26-21, 09:37 PM
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Originally Posted by Badger6 View Post
No one is spinning 140rpm, not even Lance in his prime.
I'm not even good and can spin 140 RPM, track sprinters spin upward of 200 RPM. My point was that 50x11 is plenty heavy for any normal use, and you can always find yourself on a steeper hill where the lower end gears come in handy
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Old 11-27-21, 01:13 AM
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Okay, i get the mixed metaphors, but okay
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Old 11-27-21, 08:23 AM
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Originally Posted by Badger6 View Post
No one is spinning 140rpm, not even Lance in his prime.
You might rethink that one. I think most anyone can spin 140. Maybe not on a 53/11, but on another combo.
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Old 11-28-21, 03:45 AM
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Spin @ 140? Or surge up to and beyond 140 for a short bit, say for the length of a sprint?
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Old 11-28-21, 09:24 AM
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Originally Posted by Badger6 View Post
Spin @ 140? Or surge up to and beyond 140 for a short bit, say for the length of a sprint?
The latter. For some though, mashing the 53 at a cadence under 100 might be easier than spinning all the time at 100+. Excluding the short sprinting type efforts, one of my knees will start hurting/swelling if I try to spin above 95 for extended periods of time. It's related to old sports injuries, not bike fit.
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Old 11-28-21, 12:44 PM
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Yes, nobody likes to spin 140rpm for extended periods of time, but at 50mph youíd have to find a mostly straight section of road over 4 miles long just to hold it for 5 minutes.

But I get it. Some people donít want to spin 140rpm for even 15 seconds, and I wouldnít want someone with a less than smooth form bouncing in their saddle at 50mph.
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Old 11-29-21, 12:36 AM
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So, this talk about 140rpm at the cranks is ridiculous. Sure, some riders will do it for short periods of time (sprinting, or just because, I guess), but most of us (pros included) are spinning between 80-100 for most of any ride. So, to Larry's implications that "50x11 at 140 rpm is like 50 mph" is just a distraction. If we are going to do real talk about gearing and rpms, lets bound it by the "normal" ranges that we are riding in...which 140 is clearly outside of.
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