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Cassette sizing

Old 08-19-19, 04:02 PM
  #26  
WhyFi
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Originally Posted by Princess_Allez View Post
Good to hear. I've been told to avoid cross-chaining, so I avoid going big-big, small-small and the next up/down combination. This essentially makes the bike a 16-speed instead of 22; go figure
Learn how to adjust your trim positions.

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Old 08-19-19, 11:36 PM
  #27  
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Originally Posted by WhyFi View Post
Learn how to adjust your trim positions.
Not a bad suggestion. Are you saying that it's possible to setup the front derailleur without cross-chain rub? I noticed when I'm cross chaining it rubs the cage. I figured that's just how it is when it's properly setup. My lbs does my adjustments. It feels correct. It's fast and shifts everytime.
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Old 08-19-19, 11:50 PM
  #28  
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Originally Posted by Princess_Allez View Post
Are you saying that it's possible to setup the front derailleur without cross-chain rub?
Long ago, shifters were not indexed. Instead of having two positions, a front shifter would have a continuous range of motion. To shift, you moved the shifter until the derailleur bopped the chain to the other ring.
If the chain started rubbing the front derailleur after you made a rear shift, you could use the front shifter to nudge the front derailleur over so that the rubbing stopped.

Obviously your R7000 front shifter doesn't have a continuous range of motion like this. But it does have more than two positions. When you're on a chainring, you should be able to lightly click the shifter between two "trim" positions without shifting to the other ring. If everything is set up well, and you know how to make use of the trim, this should allow you to minimize rubbing.
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Old 08-20-19, 07:04 AM
  #29  
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Originally Posted by Princess_Allez View Post
Not a bad suggestion. Are you saying that it's possible to setup the front derailleur without cross-chain rub? I noticed when I'm cross chaining it rubs the cage. I figured that's just how it is when it's properly setup. My lbs does my adjustments. It feels correct. It's fast and shifts everytime.
You shouldn't have any trouble using all of your cogs when in the big ring. In the small ring, my chain will rub the inside of the big chainring if I'm cross-chaining, but a) this rarely happens - I use the big ring 95% of the time, going to little ring only as necessary and getting back out as soon as possible b) I don't have a Shimano crankset; their current cranksets space the chainrings slightly further apart to mitigate this, IIRC.

Edited to add: many aren't aware of the trim positions and your FD may very well be set up properly. Try it out on the next ride or just give it a tap while it's on the stand and see if the FD nudges over a bit.
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Old 08-20-19, 05:16 PM
  #30  
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Originally Posted by WhyFi View Post
You shouldn't have any trouble using all of your cogs when in the big ring. In the small ring, my chain will rub the inside of the big chainring if I'm cross-chaining, but a) this rarely happens - I use the big ring 95% of the time, going to little ring only as necessary and getting back out as soon as possible b) I don't have a Shimano crankset; their current cranksets space the chainrings slightly further apart to mitigate this, IIRC.

Edited to add: many aren't aware of the trim positions and your FD may very well be set up properly. Try it out on the next ride or just give it a tap while it's on the stand and see if the FD nudges over a bit.
Will do. Thanks for the advice. FWIW, the front derailleur cage has a plastic insert to guide the chain in case of rub. That's the piece that rubs when I cross-chain. It's not a bad thing, but it's audible.
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Old 08-20-19, 10:02 PM
  #31  
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Originally Posted by WhyFi View Post
Learn how to adjust your trim positions.
...
Or go 1X

Chain drop/over shift is an issue at all levels.
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Old 08-21-19, 02:07 AM
  #32  
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Shimano sti front shifters have four positions. up/down shift and two trim positions.
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Old 08-22-19, 05:35 PM
  #33  
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I took the plunge and am having my lbs install an 11-34. Hopefully the gear spacing is to my liking. It appears it's evenly spaced until the last 3 cogs, which I can see myself liking. The last cog is for after my legs have blown, and the 2nd to last cog is still a 30, which is better than the 28 I've been using.
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Old 08-22-19, 05:49 PM
  #34  
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Originally Posted by Princess_Allez View Post
Hopefully the gear spacing is to my liking. It appears it's evenly spaced until the last 3 cogs
It is not. 11->13 and 25->27 are both 2-tooth jumps, but 13/11 is more than twice as wide a ratio as 27/25. Because the number of teeth on cogs must be integer, it's almost impossible for the spacing to be even. For instance, a 3-speed cassette with cogs of 12-18-27 would have even spacing, because each cog is 50% larger than the previous.
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Old 08-23-19, 12:20 AM
  #35  
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Originally Posted by HTupolev View Post
It is not. 11->13 and 25->27 are both 2-tooth jumps, but 13/11 is more than twice as wide a ratio as 27/25. Because the number of teeth on cogs must be integer, it's almost impossible for the spacing to be even. For instance, a 3-speed cassette with cogs of 12-18-27 would have even spacing, because each cog is 50% larger than the previous.
Sorry. What I meant is that each cog increases by a count of two from 11 to 27.
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Old 08-23-19, 01:14 AM
  #36  
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In the "most used" range 15-25 the 11-34 is exactly the same as 11-28. And it gains a 27 and 30 reachable from the big ring, but looses the 14 and 12. Imo thats a good trade off for many recreational riders.

Bicycle Gear Calculator

Last edited by Racing Dan; 08-23-19 at 01:17 AM.
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Old 08-23-19, 05:18 PM
  #37  
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Originally Posted by Racing Dan View Post
In the "most used" range 15-25 the 11-34 is exactly the same as 11-28. And it gains a 27 and 30 reachable from the big ring, but looses the 14 and 12. Imo thats a good trade off for many recreational riders.

Bicycle Gear Calculator
That's reassuring. I just picked up the bike up. I'm looking forward to testing it out. I'm a recreational rider so it sounds good to me! It sounds like I should have been on this cassette from day 1.

Edit: I went out for a ride today. The difference in shift-speed is slightly slower, but completely acceptable. I'm glad I went with the 34 cog. I don't think I'd even notice a 30 or 32. The 34 is just enough of a change for my legs to take note. I feel like I'm a wuss now when I select the 34 and spin up a hill I was getting used to getting out of the saddle or powering the 28.

Last edited by Princess_Allez; 08-23-19 at 10:55 PM.
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