Roaring coaster rear end - success at last

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RatRodDad

RatRodDad

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I bought a cheap single speed bike a couple of months ago and I noticed that when you are riding it and stop pedaling and let it freewheel, it makes a fairly loud roaring noise.

It doesn't make noise when you are pedaling or when you are braking - just freewheeling.

I pulled the coaster brake rear end apart today to see if I could see what was making the noise.

The inside piece with the threads in it - that has the brake pieces around it - has a couple of ridged places on it, and apparenlty one of them - the one on the end I think - is rubbing on something as the wheel turns and making the roaring noise.

I don't know if those ridges are something that has to be here to make the brakes work, or if I could grind them smooth and stop the roaring. Maybe they make the brakes grip better or something, I'm just not sure.

So if anyone knows about these rear ends and what I can or can't do on it, let me know. Thanks.

IMG_1749.jpg
 
Re: Roaring coaster rear end

hay i had the same issue with my second WWC bike. cracked it open looked for wear and anything out of place. nothing!!! greased the crap out of it put it back together and it was worse. thought maybe i made it to tight. nope swaped out the part you got in the pic for a old one i had and bingo cured it..

oh and yes the ridges are for the brake so you need them
 
Re: Roaring coaster rear end

Thanks, WT. If anyone else has seen this issue let me know how you resolved it.

I'm also thinking about maybe slightly sanding down the lower ridges on that piece to see if it will at least lessen the noise. It it's a little bit smoother maybe that will help.

The bike is basically new - probably being ridden 5 or 6 times total, so maybe that area normally wears down with some riding. Or maybe the ridges on that piece are deeper than normal or lower down on the piece than normal.
 
Re: Roaring coaster rear end

mine was fresh out the box and made the same noise. think the casting or turning is off when they make them. haven't rode # 3 yet but the first one i got the hole for the crank isn't in the center of the cog :? (chain) loose tight loose tight smoked the crank bearings :x
 
I've seen quite a few of these hubs lately....

My charity work on the week-ends is to fix up abandoned bikes and lend them out to folks who need sturdy transportation. As a result, I see a LOT of different bikes, and what wears out on them. In the last year I've seen quite a few of these cheap hubs with internal problems. All of them were on low-end bikes that came from bulk-discount stores.

Judging by the one's I've fixed, the problem stems from less-than-precise machining, and a lack of suitable quality control which results in some parts being either over-sized or under-sized. Depending on which part is defective, some of these hubs can be fixed temporarily. Some of them are hopeless.

IF the forcing cone or other removable part is the culprit, you can replace it IF you can find the part. (Most bike shops do not carry them, since they tend to dislike Walmart bikes.) OR you can turn the defective part on a lathe, which is what I've done with a few. OR you can disassemble several hubs, and play mix-n-match until you find a combination that doesn't roar. But to be honest, these hubs are not worth the effort. Even if you do fix it, the bearings are so poor that they'll soon wear out, causing other problems.

If the shell is defective there's not a lot you can do about it other than to replace the hub.

This is a case of "you get what you pay for". Face it, when you buy a bike for less than $100 you must expect that some of the components are going to be garbage. In this particular case, the only truly reliable fix is to replace the hub with something of higher quality.
 
Re: Roaring coaster rear end

TD, thanks for the input.

The wheel / rear hub is on an $80 bike that I bought used for $40, so I obviously don't want to spend a lot fixing it.

I may try sanding that part down a bit - as if it wore some from use - and see if that helps. If not, I guess I will just live with the roar - or as you said, swap out the whole hub on it assuming I have one that's the same diameter.
 
Re: Roaring coaster rear end

You can try to adjust the tension on the bearings. Sometimes this problem turns up when the cones inside hub are tightened to much on the bearings. The hub then rattles like it's gonna break when you're freewheeling. Maybe a usefull tip? I hope this helps. :D

PS: This problem has nothing to do with cheap ... parts or something. Every hub can have this problem when you tighten it to much. That is, if this problem is what you mean :idea:
 
Re: Roaring coaster rear end

Actually, old Maxxx..... it has everything to do with cheapo parts.

I spent some time in the Netherlands last year, and did not see the same lowest-end bikes on the road or in the stores there. My guess is your consumer protection laws prohibit their importation..... and thus the hubs you are working with are not the one's we are talking about.

Unfortunately, here in the US the mass-market bikes use sub-standard parts to keep the costs at very low levels.... and these hubs roar/stick/grab/ and sometimes fail outright because of it.
 
Re: Roaring coaster rear end

Maxxx, just to let you know, I had the same thought. I tried tightening the hub some - and then loosening it some - and it still made the same noise.

When you are pedaling it's fine, and when you push back on the pedals to brake it's fine. The only time it makes noise is when you stop pedaling and let the bike freewheel along.

I know the gear inside this part either tighens up to brake, or loosens up to drive, so it's the in between that's the problem.

I'm thinking maybe those grooves are just off or maybe too high in one spot and as that spot gets rotated to a certain position the spinning hub is then rubbing up against them - making the noise. So hopefully if I sand the ridges down a bit that will let it clear and not rub. We'll see.

It might wear and get quiet in time, but I don't think I want to wait for 2 years of riding to have that happen! :lol:
 
Re: Roaring coaster rear end

i know that when freewheeling that spring inside gets pushed back thats what disinguages the brake shoes. maybe stretching it a little so there is a bit more tension as well as file the grooves a bit? hey at this point whats the worst that is going to happen?
 
Re: Roaring coaster rear end

I've got a virtually brand new Shimano coaster that does what Maxxwell describes, but only after barking hard, when I tear it down nothing looks wrong, grease it put it together and it's OK until the next hard braking episode. The cog sort of skips while getting this metallic rattling that sounds like something is about to go. I don't believe I overtightened the bearings since I do all my hubs the same without a problem, but it may be a good place to experiment.
 
Re: Roaring coaster rear end

I played around with it a little more today. I sanded on the groves on that part to make them slightly smoother and then put it back together and tested it again.

It seems like when you back pedal - as if to brake - that pushes the groved part higher in the hub and I think those groves on the top part eventually rub against the edge of the brake shoes - which appears to be what makes the grinding or roaring noise. I think the noise is actually that rough ridged surface rubbing against the inside edges of the brake shoes.

As Kafer mentioned, maybe stretching that spring some will keep the part from going up as high and rubbing the brake shoes, or maybe I just need to do some filing on the top edge of that part to smooth out those ridges and see if that will help.

I will play around with it and let everyone know if I do finally figure out something that takes care of it.
 
I played around with that piece out of the rear hub again today and finally got it quiet.

I figured out that the piece moves left and right in the hub when you either pedal or brake. So as you were braking it was moving towards the outside of the hub and right before it began to brake those grooves on the end of the piece were rubbing up against the inside of the hub and making the roaring noise.

So I used my bench grinder and ground those end grooves smooth - not the ones in the middle of the piece - just the end ones. I put it back together and the noise is gone. It still pedals okay and brakes okay.

I think those grooves were there to help with the braking, but either they were too deep or the hub was too small or something, so they rubbed on the turning hub just enough to make noise when you were in that freewheel position. Getting rid of them - and the noise - doesn't seem to have affected anything else.

So now I have a nice quiet ride.

Thanks for all for your input.
 
do you have a pic of the part after grinding?
(probably not if you got it all back together... if so, dont worry about it :wink: )
 
Hugo, sorry about that but I didn't think to take additional pictures as I was trying things. I would do something, put it back together, spin it and see if it was quite, and if not, then pull it back apart and try something else.

I wasn't sure if it was the brake shoes rubbing on the grooves in the center part of the piece that was making the noise, or if it was the end grooves rubbing on something, or what. So I kept sanding on the grooves on each area trying to decide if anything I did was making it any quieter.

I finally figured out that when I stuck the piece into the hub by itself and held it with my finger and turned the wheel I could already feel it rubbing on the inside of the hub and vibrating. So it was already happening even without the brake shoes or bearings installed. So that told me it was actually the grooves on the end of that piece that were rubbing on the inside of the hub and that's what was making the noise.

The hub was actually tapered on the inside and I guess as you applied the brakes and that piece moved into the tapered area it began rubbing and making the noise. I think the grooves were designed to help the braking - since they would eventually get tighter and tighter in the taper as you applied the brakes harder. When you were braking it was okay and didn't make the noise. It was just when you were in the freewheel position where they were just beginning to make contact with the hub that it made the roaring noise.

So I held that piece up against my bench grinder and slowly spun it around and ground down the grooves on the end completely - until it was perfectly smooth. Once it was smooth that took care of the problem and everything else still worked okay. It still stopped fine - even though maybe having those grooves on the end of that piece would have made it stop a little better because they would have grabbed the inside of that tapered area when they got tight. I really couldn't tell the difference, though, and it still stopped like the other single speed bikes I have.

So it was nice to finally figure out what was happening - and to also better understand how those coaster brake hubs work.
 
Re: Roaring coaster rear end

TornadoDave said:
Actually, old Maxxx..... it has everything to do with cheapo parts.

I spent some time in the Netherlands last year, and did not see the same lowest-end bikes on the road or in the stores there. My guess is your consumer protection laws prohibit their importation..... and thus the hubs you are working with are not the one's we are talking about.

Unfortunately, here in the US the mass-market bikes use sub-standard parts to keep the costs at very low levels.... and these hubs roar/stick/grab/ and sometimes fail outright because of it.
Click to expand...

I guess you're right. I was wondering why I see that much low-end bikes on US sites... I mean, you guys can buy a complete new bike for 100bucks :mrgreen: But still... We do have a lot of trash bikebrands over here too :roll:
 
RatRodDad said:
So I held that piece up against my bench grinder and slowly spun it around and ground down the grooves on the end completely - until it was perfectly smooth. Once it was smooth that took care of the problem and everything else still worked okay. It still stopped fine - even though maybe having those grooves on the end of that piece would have made it stop a little better because they would have grabbed the inside of that tapered area when they got tight. I really couldn't tell the difference, though, and it still stopped like the other single speed bikes I have.
Click to expand...

Just wanted to say thank you to RatRodDad (nearly 14 years later)! Grinding down that inside piece totally worked. Thanks again!
 

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