Sprocket adapter size

Capnspaldin

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May 15, 2019
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I posted this in the correct section but nobody replied....let's try here

So my hub is exactly 4" around and that calculates to 1.27323954 thickness and the only chart I've seen is the one on Manic Mechanics site and no adapter goes that high so what I'm asking is does anyone know if I go with the highest one which says it's for a chopper and I have a BMX is that close enough would that work? Or is there a better option out there? Thanks
 
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indian22

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Dec 31, 2014
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Capn the 3 bolt sprocket/hub adapters are available in 1.25" which is as close to your measurements as you'll find. All of these are designed specifically for 36 spoke wheels and fit through the spokes without forcing or alteration to wheel or adapter. They work great when installed properly and tight. Blue (medium strength) thread locker is a good idea on the sprocket bolts and some guys, I don't, use medium locker on the hub clamp threads.

If you are using a coaster brake the 3 hole sprocket is best bought as a set with the hub adapter because the axle hole in the sprocket has to be quite large to clear the coaster brake lever. The stock brake lever which is pretty much straight has to have a slight double bend to clear frame and sprocket as well. I might have an bent brake lever and if so I'll post a photo of it compared to a straight one. I know they can be purchased but I bend them in a vise using a big F hammer. Quite exhilarating!

As with a lot of things that we do to convert bikes to gas and electric power buying parts is just the start many need additional alterations in order to function safely and properly.

Rick C.
 

allen standley

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Oct 22, 2011
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Capn the 3 bolt sprocket/hub adapters are available in 1.25" which is as close to your measurements as you'll find. All of these are designed specifically for 36 spoke wheels and fit through the spokes without forcing or alteration to wheel or adapter. They work great when installed properly and tight. Blue (medium strength) thread locker is a good idea on the sprocket bolts and some guys, I don't, use medium locker on the hub clamp threads.

If you are using a coaster brake the 3 hole sprocket is best bought as a set with the hub adapter because the axle hole in the sprocket has to be quite large to clear the coaster brake lever. The stock brake lever which is pretty much straight has to have a slight double bend to clear frame and sprocket as well. I might have an bent brake lever and if so I'll post a photo of it compared to a straight one. I know they can be purchased but I bend them in a vise using a big F hammer. Quite exhilarating!

As with a lot of things that we do to convert bikes to gas and electric power buying parts is just the start many need additional alterations in order to function safely and properly.

Rick C.
Excellent, Thanks Rick. Also, I can verify the 3 bolt Hub adapters will fit nicely on the new 29" 48 spoke coaster brake wheels.
 
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indian22

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Good info Allen on wheel and spoke sizes. I tend to ignore the larger wheels and shouldn't. The 36 spoke info is valid for both the 24" & the 26" wheel. The 24" is a snug fit but adapter goes on without forcing.

Rick C.
 
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Capnspaldin

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May 15, 2019
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I have a Mongoose Grudge so it's a fixed gear with linear pull brakes. But I think I'm going to buy the set anyway so I can run a 40 tooth sprocket. I thought the 1.25 would work just wanted to be sure. Thanks guys as always great info.
 

waynesdata

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Jul 10, 2017
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The hub sprocket adapter is incomplete the way it is designed. Over time adapter will move bend your spokes. Look the bike in the bike berry youtube install. Even that bike has bent spokes. A notch and keyway are needed between the hub and adapter.
 
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allen standley

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Oct 22, 2011
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The hub sprocket adapter is incomplete the way it is designed. Over time adapter will move bend your spokes. Look the bike in the bike berry youtube install. Even that bike has bent spokes. A notch and keyway are needed between the hub and adapter.
A notch and keyway would be a great idea but they don't machine them in yet. The heavier the spoke the better. I only use wheels with big11 and 12 guage spokes not skinney spindley spokes.
Just like everything else. Use blue LocTite, lightly fasten it down, eye it's tracking, When you got it where it is tracking dead on then tighten as best as possible. Watch steadily over the next few miles tighten when possible. Although I've installed many of these (more than 20) all on coaster brake hubs, the only time I had one slip, it was my own fault. I didn't tighten it down or pay attention as I should have. Yes it was a multi speed hub with skinney spindl;ey spokes. After this early experience I stopped using multi speed hubs and advise others not to use them. Multi speed hub offers less surface area to clamp onto --so yes may be a concern with that type hub.
https://motorbicycling.com/media/slipped-adapter.10944/
 

indian22

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If installed correctly a well machined adapter won't slip on coaster hub. I'm not against a keyway, but not necessary for holding the adapter in place. Don't buy the cheapest price adapters. I favor the Sportsman Flyer as the best adapter out there, but I've used Manic and others that don't slip and I've got two bikes that are 12 + hp and 14.5 hp respectively that don't slip into the spokes... these are 125cc 4 stroke Honda 5 speed wet clutch motors that really torque. No reason a China girl or even a 212 Predator, under 15 hp should. If your adapter slips take some personal responsibility for buying cheap and installing wrong.

Extreme riding wheelies, power shifts (with real motorcycle transmissions) etc. with powerful motors really should use a moped style wheel and hub with minimum10 gauge spokes and quality sealed bearings, and not bicycle coaster parts. Common sense used to match riding styles with engine power and appropriate parts.

Allen's 20 + builds and my dozen builds both of us doing this close to ten years now know a few things that work!

Rick C.
 
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Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I posted this in the correct section but nobody replied....let's try here

So my hub is exactly 4" around and that calculates to 1.27323954 thickness and the only chart I've seen is the one on Manic Mechanics site and no adapter goes that high so what I'm asking is does anyone know if I go with the highest one which says it's for a chopper and I have a BMX is that close enough would that work? Or is there a better option out there? Thanks

Can you post some pictures of your hub? That will help us give some advice.
 

waynesdata

Active Member
Jul 10, 2017
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I trust the advice of indian22. Some of his builds have many more miles than mine. I was using a cheap china sprocket.

Upgraded to disc break mount attached sprocket adapter at around 4k miles. The build posted by TheNecromancer13 is a good example of disc break mount. The sickbikeparts looks good at first glance. I have no first hand knowledge with shift kits. Building my first shifter now.
 

indian22

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Dec 31, 2014
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Wayne I've also used the disk brake mount style sprocket hub, like you changed over to, & disk rotor mount combination on a build and it's preformed well. No chance these will tear up spokes and that's fact. Quite often builders find good alternatives that work for their builds & you've shown three alternatives that actually work and that's a good thing.

One of the things I love about building one off designs is solving problems. Each build unique in many ways and similar in others, but all demanding solutions to problems both large and small. Hobbies are supposed to be fun, but not necessarily easy, if that were so most would score well on the golf course...but few ever do, yet spend many hours and $$ trying to do better. Most still think it's fun & love it.

Using moped hubs, wheels & brakes is another great upgrade from bicycle parts and they are great alternatives, especially for the high power bike builds, as are custom machined hubs and wheel sets designed for prolonged running at highway speeds over long distance. Wider rear drop outs are usually required for setups running moped hubs/ brakes.



Rick C.
 
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