Threaded freewheel width and compatibility

[pishta]

I looked high and low for the dimensions of freewheels when looking for one that would fit a 26" Ebikeling hub motor. FYI these common retrofit rims only take a 29.5 mm thick 'most' 6 speed or a 24mm 5 speed threaded freewheel with spacer only (or anything >30mm) as the smooth part of the axle ends exactly at 30mm from the base of the threads. I mistakenly bought an 8 sp freewheel to match the 8sp rim I removed from a Mongoose Tech 4 but found the 8sp is ~35.4mm thick and would not even fit between the dropouts of the frame when mounted as the standard MTB bike hub is more narrow than the hub motor. I'm bummed as the SRAM index shifter is set up for a 8sp. I did find this chart here that helped considerably and I would like to share this so others won't have to look far for it.

3.2. Table 1​

TABLE 1	Dimensions are in millimetres
Cassette type and number of sprockets	Cassette Pitch	Sprocket Thickness	Spacer thickness	Total width
most 5-speed	5 – 5.5	1.85 – 2	3.5	24
most 6-speed	5 – 5.5	1.85 – 2	3.5	29.5
Shimano, SRAM Hyperglide 7-speed	5	1.85	3.15	31.9
Freewheel 7-speed	5	1.8 – 1.85	3.15 – 3.2	32.4 – 32.8
Shimano, SRAM 8-speed	4.8	1.8	3	35.4
Shimano, SRAM 9-speed	4.35	1.78	2.56	36.5
Shimano, SRAM 10-speed	3.95	1.6	2.35	37.2
Shimano, SRAM 11-speed road **	3.74 **	1.6	2.14	39
Shimano, SRAM 11-speed MTB **	3.9 **	1.6	2.3	40.6
Campagnolo 8-speed	5	1.9	3.1	36.9
Campagnolo 9-speed	4.55	1.75	2.8	38.2
Campagnolo 10-speed	4.15 on average *	1.7	varies *	38.8
Campagnolo 11-speed	3.85 on average *	1.6	varies *	40.1
SRAM 12-speed MTB	3.65	n/a	n/a	n/a
Shimano Dura Ace 6-speed	6.07	n/a	n/a	n/a
Shimano Dura Ace 7-speed	5.52	n/a	n/a	n/a
Shimano Dura Ace 8-speed	5.3	n/a	n/a	n/a

Thanks for the info!

 

[BikeGremlin]

I looked high and low for the dimensions of freewheels when looking for one that would fit a 26" Ebikeling hub motor. FYI these common retrofit rims only take a 29.5 mm thick 'most' 6 speed or a 24mm 5 speed threaded freewheel with spacer only (or anything >30mm) as the smooth part of the axle ends exactly at 30mm from the base of the threads. I mistakenly bought an 8 sp freewheel to match the 8sp rim I removed from a Mongoose Tech 4 but found the 8sp is ~35.4mm thick and would not even fit between the dropouts of the frame when mounted as the standard MTB bike hub is more narrow than the hub motor. I'm bummed as the SRAM index shifter is set up for a 8sp. I did find this chart here that helped considerably and I would like to share this so others won't have to look far for it.

3.2. Table 1​

TABLE 1	Dimensions are in millimetres
Cassette type and number of sprockets	Cassette Pitch	Sprocket Thickness	Spacer thickness	Total width
most 5-speed	5 – 5.5	1.85 – 2	3.5	24
most 6-speed	5 – 5.5	1.85 – 2	3.5	29.5
Shimano, SRAM Hyperglide 7-speed	5	1.85	3.15	31.9
Freewheel 7-speed	5	1.8 – 1.85	3.15 – 3.2	32.4 – 32.8
Shimano, SRAM 8-speed	4.8	1.8	3	35.4
Shimano, SRAM 9-speed	4.35	1.78	2.56	36.5
Shimano, SRAM 10-speed	3.95	1.6	2.35	37.2
Shimano, SRAM 11-speed road **	3.74 **	1.6	2.14	39
Shimano, SRAM 11-speed MTB **	3.9 **	1.6	2.3	40.6
Campagnolo 8-speed	5	1.9	3.1	36.9
Campagnolo 9-speed	4.55	1.75	2.8	38.2
Campagnolo 10-speed	4.15 on average *	1.7	varies *	38.8
Campagnolo 11-speed	3.85 on average *	1.6	varies *	40.1
SRAM 12-speed MTB	3.65	n/a	n/a	n/a
Shimano Dura Ace 6-speed	6.07	n/a	n/a	n/a
Shimano Dura Ace 7-speed	5.52	n/a	n/a	n/a
Shimano Dura Ace 8-speed	5.3	n/a	n/a	n/a

Thanks for the info!

For anyone reading this, here is the original table from my website (I do my best to keep info in one place, so that I don't miss updating it - when the same info is in several places, it is more difficult to keep track of any updates):

https://bike.bikegremlin.com/3573/bicycle-cassette-rear-chainrings-standards/#3.2

Most of my articles (and even videos for that matter) are designed so one can easily find and even copy-paste share links to particular parts of articles, for easier reference.

 

[pishta]

Thanks! I did find this very helpful and would like to add to my original post that these hub motor rims could take thicker freewheels but the Mongoose Tech 4 dropouts were exactly 133mm (?) where the hub motors threads started thus needing a thinner than 30mm freewheel. If your dropouts are wider you could take 7-10 speed I suppose.

 

[BikeGremlin]

Thanks! I did find this very helpful and would like to add to my original post that these hub motor rims could take thicker freewheels but the Mongoose Tech 4 dropouts were exactly 133mm (?) where the hub motors threads started thus needing a thinner than 30mm freewheel. If your dropouts are wider you could take 7-10 speed I suppose.

I presume that the nominal ("aimed-for") size is 132.5 mm, which makes it possible to mount both road (130 mm OLD), and MTB (135 mm OLD) hubs.

The number of speeds that fits depends on hub flange design - to accommodate more speeds (i.e. wider cassette), right hub flange is moved towards the centre of the hub.

This makes for a weaker wheel because of greater disbalance between the right and left flange mounted spoke tension. More about that:
How the number of speeds affects rear wheel strength (video)

Freewheel (as opposed to freehub) hubs have poor support for the axle, so 8+ speed freewheels often have axle breaking problems. I explained that in more detail here:
https://bike.bikegremlin.com/158/bicycle-rear-hub/#4
7 speed freewheels are neither here or there, but that extra unsupported length to accommodate for the wider freewheel also doesn't help the axle's strength.

 

[pishta]

>>Success!! (read last part)<<< Thanks again, I am hamstrung by what I can do with this hub motor and the frames drop out spec. I can't fit the 8sp freewheel as its 35mm (5mm too wide), about 138mm total, I can't alter the axle as its integral into the hub motor and has a wire harness inside and the dropouts can't be expanded to 138mm as its a 4 link style and the pivot points would not remain parallel (?)..AND the only cogs that fit the threaded hub must be 30mm or thinner (5sp or 6sp) to fit within the 133mm dropouts...AND the SRAM X4 8sp index shifter wont index to the larger 6sp cog spacing so now I must get a 6sp shifter to operate the X4 derailer. Haaha, lots of work to get this electrified!

>>OR-----take the 4 link apart: Widen the swing arm 5mm and then widen the floating link bar 5mm and massage the plastic bushings the link pivot pins go in, grease them up good and you end up with a ~138mm dropout width and a rather tight fitting hub motor with all the stock 3x8 speed stuff still in place! Sometimes brute force trumps re-engineering....This is the rear setup that I was working with minus hub motor.