Gearing Question
10-12-20 | 01:24 PM
#1
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Gearing Question
For those of you that like to exercise the grey matter in your heads and for the few of you that might know this off the top of your head, is it possible to run a 39/50 front with a 10/50 cassette? Thanks in advance,
10-12-20 | 01:33 PM
#2
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According to manufacturer's spec neither Shimano nor SRAM say it'll work. With a Shimano crank you could get chainrings as the they're all the same BCD. You'd need a derailleur with 51t of chainwrap...they don't exist. It's kind of a Catch 22 with Shimano. The double GRX derailleur has 41t of wrap but is only ok up a 34...probably work w/ a 36...but you're 10t shy of chain wrap. The single GRX will work w/ a 42t cog but only wraps 31t, so you're 20 short. I'm sure there will be plenty of guys posting soon that will say 'sure, it works great...you just can't do this, or do that'. So...according to the manufacturers the answer is a big ole no.
And obviously this post should be in 'bicycle mechanics' not GD.
And obviously this post should be in 'bicycle mechanics' not GD.
10-12-20 | 01:47 PM
#3
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Have you considered going with a multi speed rear hub similar to Sturmey Archer that uses both the internal 3-speed hub and a 9 speed rear derailleur. I have one trike with the no longer available SRAM dual-drive that expands the gear range on both ends. It's the least expensive way compared to multi-speed hubs like the expensive Rholoff speed hub and you can use a standard cassette to get the gear range you wish.
10-12-20 | 03:41 PM
#4
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This difference is calculated using the teeth difference.
In your case (50 front + 50 rear) - (39 front + 10 rear) = 51
100 - 49 = 51 teeth capacity
The rear derailleur has to be able to take up the slack in the chain for this 51 difference.
Rear Derailleurs are rated in two ways.
Capacity (in your case 51)
Max rear Cog (in your case 50)
You are going to have a really tough time finding a Rear Derailleur to meet both these requirements at the same time.
But now you know what your looking for!
All the best
Barry
Last edited by Barry2; 10-13-20 at 11:51 AM. Reason: Typo
10-12-20 | 04:59 PM
#5
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When you go from Large Front Ring & Large Rear Cog to Small Front Ring and Small Rear Cog there is a considerable difference in the length of chain needed.
This difference is calculated using the teeth difference.
In your case (50 front + 50 rear) - (39 front + 10 rear) = 51
100 - 49 = 51 teeth capacity
The rear derailleur has to be able to take up the slack in the chain for this 51 difference.
Rear Derailleurs are rated in two ways
Capacity (in your case 51)
Max rear Cog (in your case 50)
You are going to have a really tough time finding a Rear Derailleur to meet both these requirements at the same time.
But know you know what your looking for!
All the best
Barry
This difference is calculated using the teeth difference.
In your case (50 front + 50 rear) - (39 front + 10 rear) = 51
100 - 49 = 51 teeth capacity
The rear derailleur has to be able to take up the slack in the chain for this 51 difference.
Rear Derailleurs are rated in two ways
Capacity (in your case 51)
Max rear Cog (in your case 50)
You are going to have a really tough time finding a Rear Derailleur to meet both these requirements at the same time.
But know you know what your looking for!
All the best
Barry
10-12-20 | 05:46 PM
#6
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When you go from Large Front Ring & Large Rear Cog to Small Front Ring and Small Rear Cog there is a considerable difference in the length of chain needed.
This difference is calculated using the teeth difference.
In your case (50 front + 50 rear) - (39 front + 10 rear) = 51
100 - 49 = 51 teeth capacity
The rear derailleur has to be able to take up the slack in the chain for this 51 difference.
Rear Derailleurs are rated in two ways
Capacity (in your case 51)
Max rear Cog (in your case 50)
You are going to have a really tough time finding a Rear Derailleur to meet both these requirements at the same time.
But know you know what your looking for!
All the best
Barry
This difference is calculated using the teeth difference.
In your case (50 front + 50 rear) - (39 front + 10 rear) = 51
100 - 49 = 51 teeth capacity
The rear derailleur has to be able to take up the slack in the chain for this 51 difference.
Rear Derailleurs are rated in two ways
Capacity (in your case 51)
Max rear Cog (in your case 50)
You are going to have a really tough time finding a Rear Derailleur to meet both these requirements at the same time.
But know you know what your looking for!
All the best
Barry
10-12-20 | 05:48 PM
#7
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Have you considered going with a multi speed rear hub similar to Sturmey Archer that uses both the internal 3-speed hub and a 9 speed rear derailleur. I have one trike with the no longer available SRAM dual-drive that expands the gear range on both ends. It's the least expensive way compared to multi-speed hubs like the expensive Rholoff speed hub and you can use a standard cassette to get the gear range you wish.
10-12-20 | 05:49 PM
#8
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