dust cap, coaster brake, drive sprocket mounting questions

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andy b.

New Member
Jul 14, 2010
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PA, USA
I am installing my Grubee on a Schwinn Delmar. Once the coaster brake arm is off there is a metal cap that I would call a dust cap that sits under the brake arm. It is held on by the brake arm and just appears to be a cap to keep dirt out. On the Grubee kits, does the drive sprocket go on the axle, and then the dust cap and then the brake arm? I put the dust cap on, and then the sprocket, and then the brake arm and once tightened the sprocket seems to be pressing on the dust cap and the brake arm is no longer free to turn. Also, do I need the thick rubber gasket under the drive sprocket? The installation instructions say you may not need it, but it looks like if I don't use it then the sprocket sits almost even with the tire and I'm sure the chain will rub the tire.

Thanks for any advice.

andy b.
 
KCvale

KCvale

Well-Known Member
Feb 28, 2010
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Phoenix,AZ
andy b. said:
...and then the brake arm and once tightened the sprocket seems to be pressing on the dust cap and the brake arm is no longer free to turn.
Click to expand...
The brake arm doesn't need to spin Andy, that's why you attach it to the chainstay.
As long as the wheel itself tightens down properly with no side to side wobble you are fine, just attach the brake arm to the chainstay before you tighten up the wheel nuts.
 
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DudeZXT

New Member
Jun 20, 2010
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Lexington, KY
I motorized 2 bikes with coasters and used tinsnips and a dremel to cut the deep lip off from around the cap, so it wouldn't interfere with rotation of the wheel. I felt more comfortable at least keeping some sort of cover to keep the bearings protected, somewhat, rather than leaving the cover off altogether (which I'm sure you could do instead).

My dust covers fit inside the hole of the new rear chain sprocket and I had to tighten the brake arm in order to hold them from just falling off..
 
Venice Motor Bikes

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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It's important to keep the dust cap on the wheel (after trimming the edge) because it also provides correct spacing to properly tighten the brake arm! ;)
 
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andy b.

New Member
Jul 14, 2010
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PA, USA
Thanks guys!!! I wasn't sure if it was called a dust cap or not, so I didn't even search before asking. I searched on sprocket mounting and a few other phrases, but they weren't what I was looking for. Anyway, once I searched for "dust cap mod" in the several threads I found, it seemed the choices were to trim the dust cap, or make the bore of the sprocket larger. I have a lathe, so it was actually faster for me to just make the sprocket bore larger. The sprocket is now securely mounted! :) Everything seems to work as it should on the rear wheel. I mounted the bare motor earlier in the day and hopefully I'll get the rest installed tomorrow morning (well, this morning now, since it is 1am) and fire it up!

andy b.
 
tudorvintiloiu

tudorvintiloiu

New Member
Apr 19, 2010
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Romania
So did you use the rubber ring when mounting the sprocket, or did you just put it against the spokes?
I'm having the same issue with my coaster brake. If i use the rubber thing it pushes the sprocket so far out that i can't mount the brake arm.
Could you post a pic? that would be helpful. Thanks!

T.
 
F

FreeWheeler

New Member
Jun 22, 2010
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Maryland
Sounds like you need to bend the brake arm in a vice to get some clearance. Somebody sells custom brake arms which are already shaped to clear the sprocket bolts, but a vice is what I used. It wasnt exactly a precision operation, just chuck it up in the vice and estimate the bend needed.
 
A

andy b.

New Member
Jul 14, 2010
55
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PA, USA
On my cheap Schwinn here is my mounting order:

Inner three-piece metal ring
rubber ring (pieces of old tires is more like it)
spokes
next rubber ring
two-piece metal ring
big drive sprocket

Then I put the bolts through everything and tightened it down. I tightened it until the lock washers crushed down flat, so I have no idea how many ft-lbs it is. I didn't use a 18" ratchet though, just some normal box wrenches.

I have to say, the Chinese engine seems like a big piece-o-junk to me since it refuses to run, but the sprocket mounting arrangement seems quite sturdy.

EDIT: I forgot to mention, I didn't have to bend my coaster arm, it just barely fits.

andy b.
 
Last edited:
C

Chalo

Member
Aug 10, 2010
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Texas
KCvale said:
The brake arm doesn't need to spin Andy, that's why you attach it to the chainstay.
Click to expand...
The brake arm does not need to turn once installed, but the sprocket that is attached to the wheel does need to turn-- thus the problem when it smashes into the dust cap. This is the main issue I have dealt with as a bike mechanic troubleshooting other people's MB builds.

I send my customers to a machine shop to have the sprocket bore enlarged to 1.75". This is enough to clear the stationary components of the coaster brake hub and allow the rotating assembly to rotate.

Chalo
 
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bandit143728

New Member
Aug 12, 2010
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Daytona Beach Florida
I just received a new rear sprocket from piston bikes . com It is for the coaster brake set up as it has a 2" center hole haven't tried it yet but it looks like it will clear the arm just fine also came witha new rag joint assembly not bad for 20 bucks Ill let you know when I install it and how it works.

Good luck:-||
 
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moonlake3

New Member
Jun 16, 2010
16
0
0
Florida
My brother is trying to change his rear sprocket to his new bike build. He is telling be that the rear hub would need to be dissembled in order to get the rear sprocket off. (Coaster brake Huffy. ) He does not live by me and I'm trying to help him long distance. He has taken the sprocket off the old bike and is afraid to put it on the new bike because he doesn't want to take the new rear hub apart. Is this correct. Doesn't the brake arm come off the axle. I have looked around here and get the idea that the rear hub does not need to come apart to mount the sprocket. He claims the brake arm does not come off the axle. From doing online search, it looks like it does. Maybe the nut is just really tight. thanks for some input.. I can't seem to locate a picture like I need to see. After all if you had to bend the brake arm to make it clear, it must come off. Left hand threads? Or just tight. thanks...flg.
 
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moonlake3

New Member
Jun 16, 2010
16
0
0
Florida
Thanks for the great info and pictures. It is all clear now.Thanks for your time for taking and posting the great series of pictures. Also the dust cap series of pictures...

.flg..spr.
 
Leviathan

Leviathan

New Member
Aug 8, 2010
2
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0
Greene County, MO
Hey guys, i was trimming down my dust cover, and a wasp stung me on the back. I jerked my hand, and took a little chunk outta the side of the cover (thank the Motorbicycling Gods My hand was ok). Anybody have a line on where I could order another one? I have checked with most of the shops around, and nobody seems to have one.

Thanks a lot!

p.s. that wasp is now dead.
 
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