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Replacing Deore chainring with a larger chainring

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Replacing Deore chainring with a larger chainring

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Old 07-12-18, 02:07 PM
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sbe171
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Replacing Deore chainring with a larger chainring

Hi,


I have a bike with Deore XT 11-42 11 speed cassette, and Deore XT 28/38 chainring.
I ride mostly roads and paths, so I don't need to go so low, and I sometimes would like to go a little higher than this.

Is there a way to replace the big chainring to a slightly bigger one?
What's ideal for me would be something like 32/44.
Can I just change one chainring? Where can I find suitable ones?
I understand any chainring or chainset I install must be for specifically 11 speed chain and from Shimano?

Can I install a Shimano Ultegra FC-R8000 2 x 11 speed 50-34T 172.5mm? Sounds like if it is 11 speed and Shimano and two chainrings, it should work with the chain, derailleur and shifter that I have installed.
Or Shimano 105 5800 11 speed chainset (compact 50/34, cranks 170 mm) crankset?
Can I install a Shimano XT M8000-3 11-Speed Mountain Bike 40/30/22t 175mm - can the derailleur be readjusted or derailleur and shifter must be replaced?


Thanks,
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Old 07-12-18, 02:15 PM
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you grasp the bolt circle measurement idea? 110 & 130 are 2 common 5 bolt patterns.
130 minimum is 38t for 34 t you need a 110, for 32 t, it has to be smaller yet,
can't be smaller than the bolt pattern that holds it on.
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Old 07-12-18, 02:37 PM
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sbe171
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Originally Posted by fietsbob View Post
you grasp the bolt circle measurement idea? 110 & 130 are 2 common 5 bolt patterns.
130 minimum is 38t for 34 t you need a 110, for 32 t, it has to be smaller yet,
can't be smaller than the bolt pattern that holds it on.
Thanks for your answer.
I'm actually not familiar with any of this, that's why I asked the question.
What I was able to understand from what you said, it seems you were talking about a smaller chainset, but I wanted to install a bigger one.
I haven't taken the chainset apart yet so I don't know what the bolt situation looks like.
This is what Shimano puts in their website:
Use: MTB Cross Country / All Mountain
Group: XT
Model: FC-M8000-2
Gradation: 38-28T
Crank Arm Length: 175mm
Q-Factor: 176mm
Threaded BB shell width: 68 / 73mm
Gear: 11-speed
Construction: Hollowtech II
Compatible Chain: HG-X 11-speed
PCD: 96 / 64mm
Chain line: 48.8mm
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Old 07-12-18, 02:50 PM
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You're asking two different questions. Changing chainrings comes down to the rings being compatible with the crank and having derailleurs with the capacity to jump the chain from 28 to 44. Your specific derailleurs have listed capacities that can be looked up by specific model year and version.

Using an Ultegra crank is a problem because your frame may be too wide for a crank with a road width spindle.
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Old 07-12-18, 02:57 PM
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sbe171
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Originally Posted by Kontact View Post
You're asking two different questions. Changing chainrings comes down to the rings being compatible with the crank and having derailleurs with the capacity to jump the chain from 28 to 44. Your specific derailleurs have listed capacities that can be looked up by specific model year and version.

Using an Ultegra crank is a problem because your frame may be too wide for a crank with a road width spindle.
This is the derailleur spec:
MODEL NO FD-M8020-E
SERIES SHIMANO DEORE XT M8000 Series
Color Series color, -
Average weight 120 g
Remarks * Compatible with the special crankset which chainline is 3 mm outboard.
Action_Side Swing X
Angled stroke adjust bolt X
Cable route type_Front-Pull exclusive X
Chain line (mm) 48.8*
Chain stay angle 66-69
Compatible chain HG-X11
Link bushings 6
Mount_E-type without BB Plate X
Speeds_Front 2
Speeds_Rear 11
Top gear teeth 34-38T
Total capacity 10T

Does it have the required capacity?
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Old 07-12-18, 03:05 PM
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Originally Posted by sbe171 View Post
This is the derailleur spec:
MODEL NO FD-M8020-E
SERIES SHIMANO DEORE XT M8000 Series
Color Series color, -
Average weight 120 g
Remarks * Compatible with the special crankset which chainline is 3 mm outboard.
Action_Side Swing X
Angled stroke adjust bolt X
Cable route type_Front-Pull exclusive X
Chain line (mm) 48.8*
Chain stay angle 66-69
Compatible chain HG-X11
Link bushings 6
Mount_E-type without BB Plate X
Speeds_Front 2
Speeds_Rear 11
Top gear teeth 34-38T
Total capacity 10T


Does it have the required capacity?
44-32= 12 total capacity.
Top gear 44, top gear max 38.

No, not compatible. A different derailleur might be, or this one might work despite the warning.
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Old 07-12-18, 03:19 PM
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Originally Posted by Kontact View Post
44-32= 12 total capacity.
Top gear 44, top gear max 38.

No, not compatible. A different derailleur might be, or this one might work despite the warning.
So the contention point, if I understand correctly, if the difference between the two rings, which should not be more than 10?
I was able to find on eBay Shimano XT chainrings 32T and 42T - so that would be 10T difference - this is safe?
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Old 07-12-18, 03:32 PM
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That's a little tough. You have the largest chainrings Shimano intended for that drivetrain. The bolt pattern for that crank is not the absolutely most common and there probably aren't larger rings that will fit. The front derailleur is not designed to shift a larger ring and few if any double mountain front derailleurs will. Also Shimano front derailleurs are incompatible between road and mountain. Your best bet is to get a road crank, front derailleur, and front flat bar road shifter.

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Old 07-12-18, 03:52 PM
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Originally Posted by sbe171 View Post
So the contention point, if I understand correctly, if the difference between the two rings, which should not be more than 10?
I was able to find on eBay Shimano XT chainrings 32T and 42T - so that would be 10T difference - this is safe?
That and the max rings size I also pointed out is 38 and you want larger than 38.
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Old 07-12-18, 04:01 PM
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So the bottom line is this crankset can't be enlarged any further.
In my initial question I asked about installing an Ultegra crankset, and one of you said "Using an Ultegra crank is a problem because your frame may be too wide for a crank with a road width spindle."
I don't understand what part of the frame would be too wide. How can I tell if Ultegra crankset, or 105 crankset, or different one, can be installed on my frame or not?
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Old 07-12-18, 04:11 PM
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Originally Posted by sbe171 View Post
So the bottom line is this crankset can't be enlarged any further.
In my initial question I asked about installing an Ultegra crankset, and one of you said "Using an Ultegra crank is a problem because your frame may be too wide for a crank with a road width spindle."
I don't understand what part of the frame would be too wide. How can I tell if Ultegra crankset, or 105 crankset, or different one, can be installed on my frame or not?
The width of the BB shell - usually 68mm road and 73mm mountain, and the width of the chainstays where the chainrings and crank ends pass, and the chainline of the cassette.

These days components have fairly specific operating parameters, and there is more differences between road and MTB standards than there used to be.

There is likely some combination of parts that will make your bike, designed to be ridden in a certain way, work a completely different way. But have you considered why your bike came with that gearing and whether you are riding the bike as intended? Trying to make a bike that is perfect for one thing do something completely different is often a painful learning experience.
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Old 07-12-18, 06:46 PM
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Originally Posted by sbe171 View Post
So the bottom line is this crankset can't be enlarged any further.
Probably not without significantly more effort than simply bolting a larger ring onto the crank.

Another obstacle might be if your front derailleur attaches to a permanently fixed mount point, rather than a clamp that can be freely moved on the seat tube to accommodate different diameter rings. Most permanently fixed front derailleur mounts only offer a centimeter or less of vertical adjustment. If your preferred ring falls outside that range, it won't work.
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