30/70 Gearing
Cruiser
Joined: Sep 2025
Posts: 167
Likes: 55
From: New England, Maine
Probably not. A 30/70 is a much bigger change than it looks. The belt will sit higher and the guards likely won't line up with the new belt path. You'll probably have to run without them or get custom ones.
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Road Master
Joined: Apr 2023
Posts: 944
Likes: 1,326
From: South of Heaven
Yup, I think the biggest you can go and still use the guards as they are is a 68.
I have heard you can crank the top guard up and get it to work with a 70 but the lower guard is a no go...?
I have heard you can crank the top guard up and get it to work with a 70 but the lower guard is a no go...?
Seasoned HDF Member
Joined: Mar 2010
Posts: 20,951
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From: Poolville
What year and model??
On my 2013 FXDB I went with a 70 on the rear without issue.. I did have to go to a larger belt because I kept the 32 front..
On my 2013 FXDB I went with a 70 on the rear without issue.. I did have to go to a larger belt because I kept the 32 front..
Last edited by 98hotrodfatboy; Sep 23, 2025 at 02:09 AM.
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Road Master
Joined: Apr 2023
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From: South of Heaven
2011 Fat Bob. I have a 68 on there now as it was the biggest that would fit with the 32 and 131 belt. I need to change the belt and will be putting in a 30 while I'm in there.
Not clear if I should just keep the 68 (will be able to keep the 131 belt at 30/68) or go to the 30/70 with a 133 belt. If I have to mess with the guards then I will stay with the 68 but it seems like a 70 will work?
Not clear if I should just keep the 68 (will be able to keep the 131 belt at 30/68) or go to the 30/70 with a 133 belt. If I have to mess with the guards then I will stay with the 68 but it seems like a 70 will work?
Seasoned HDF Member
Joined: Mar 2010
Posts: 20,951
Likes: 7,483
From: Poolville
If you're doing a 30/70 you don't need to change the belt.. it should be a fit without any problem for every one tooth you go down on the trans pulley you can go up 2 on the driven pulley.. So two down on the front is four up on the rear with the same belt..
Edited: Before doing a deal to a 30/70 check out Nighrider gearing calculator..
http://www.nightrider.com/biketech/calc_gearratios.htm
Edited: Before doing a deal to a 30/70 check out Nighrider gearing calculator..
http://www.nightrider.com/biketech/calc_gearratios.htm
Last edited by 98hotrodfatboy; Sep 24, 2025 at 07:05 PM.
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Road Master
Joined: Apr 2023
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From: South of Heaven
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3rd Gear
Joined: Apr 2023
Posts: 7
Likes: 3
From: Iowa
I have done 30/66 and 30/70, and was able to keep everything else stock. I thought for sure I was going to like the 70 rear, but I swapped it back to 66. Pm me if you want my 70 rear, it’s a stock one off an ‘06. My bike is a 2010 FXD
Seasoned HDF Member
Joined: Jan 2015
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From: Sandy Eggo's North County
Each gear will be shorter, so you'll have to shift more often. And, then, when you're rollin' on the freeway, you'll be revving higher than you do currently. Using add'l fuel and shortening your range.
Wearing out the topend likely won't be a concern, unless you rack up serious miles. Forget about making this an "Ironbutt mount."
Wearing out the topend likely won't be a concern, unless you rack up serious miles. Forget about making this an "Ironbutt mount."
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