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Post by meta82 on Oct 2, 2010 23:35:39 GMT -5
Hey all.
I bought a used Chinese scoot a few months ago and have been having some trouble with the rear brake. It does not seem to provide much, if any, stopping power. When the scoot is on the center stand, the brakes appear to stop the tire, but when I am riding the scooter, the most the rear brakes will do is
slow the bike down a little. At first I thought the drum shoes were glazed, so I bought new ones and installed them(http://www.partsforscooters.com/Brake-Shoe-Set). Same thing happens. The brakes appear the stop the scoot at very low speeds but do nothing when riding over 10mph. I played with the brake trim adjustment. I am sure the brake pads are pushing against the drum.
On a side note, my rear tire will deflate over the course of the week. I loses 4-5 psi per day and is usually flat by the end of the week if I do not put air in it. I had a new tire put on and the same thing happens. Checked for leaks and found nothing. I am thinking damaged rim?
meta82
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Post by shadowwalker on Oct 3, 2010 2:31:55 GMT -5
Ok have you tightened the adjuster for the rear brakes? It is the gold 9/16 nut that is on the end of the rear brake cable. Adjust it so the rear wheel spins freely but there is very little pull to the brake handle. These cables are notorious for stretching and loosening the feel of the brakes. The deflating tire deal sounds like you might have a ding in the rims bead area or even possibly a hairline crack in the wheel. If you don't see any obvious damage put a small amount of fix a flat in the wheel then go for a ride to distribute it evenly. This should seal any pinhole leaks you might have.
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Post by sprocket on Oct 3, 2010 15:35:07 GMT -5
Check the valve stems... the Chinese can't make a decent one... both mine leaked. I replaced them with straight stems and put on metal valve caps that seal well. Never had a problem since...
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Post by meta82 on Oct 3, 2010 19:08:30 GMT -5
Thanks for the tips. I did tighten the adjuster for the rear brakes to the point where there was little pull in the brake cable. Still, the brakes have little effect while riding the scooter. No matter how hard I pull the brakes, it just slows down a little. Should I take the scoot to a mechanic?
Right after I bought this scoot, I tried to check the tire pressure and the valve stem broke off. I replaced it with a bent metal valve stem, but dont have a cap on it. I will see if the cap prevents air leakage.
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Post by shadowwalker on Oct 4, 2010 3:10:16 GMT -5
Try sanding any glazing off the brake shoes and take a green scotch brite pad to the inside of the brake drum to roughen the surface up a bit to provide more bite for the shoes.
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Post by Bluefront on Oct 4, 2010 7:29:41 GMT -5
A damaged rear brake cable can act like this......if the outer cover is broken somewhere, or maybe if an attachment clamp came loose or is missing.
The valve stem cap is not the problem.....the valve core maybe is loose/leaking, the tire bead is not sealing properly, etc. The exact leak can usually be found with a spray of detergent and water.....over- fill the tire with air and spray it down. The leak will bubble up.....
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Post by tomcas on Oct 4, 2010 7:43:21 GMT -5
I will see if the cap prevents air leakage. It's simple to tell if the valve stem is leaking past the check valve. Just put a little spittle on the tip of your finger and wipe it on the tip of the valve so that it forms a film over the end. Any leakage will immediately form a bubble. Yeah I know to some people it's gross but it works. |
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Post by meta82 on Oct 9, 2010 15:13:11 GMT -5
Ok, I checked the rear brake cable and it looks fine. However, when I took off the rear tire, I noticed the new brake shoes were coated in a layer of grey dust. This did not come from the new brakes shoes as the pads on them are green. It also looks like only part of the brake shoe is hitting the drum when the brakes are applied. Should I sand part of the pad down so they hit the drum evenly? Here are a few picture of the brake pads.   Here is the inside of the drum..  |
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Post by sprocket on Oct 9, 2010 17:05:04 GMT -5
That's the way they should look. The brakes are hinged at the top or bottom and the just touch on a small area.
The rear brakes aren't designed to stop the bike. You should be using the front and rear brakes together. The fronts do about 90% of the stopping and the rear brakes simply drag (10%) to prevent the rear of the scooter from sliding out sideways...
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Post by meta82 on Oct 9, 2010 17:23:06 GMT -5
But I should be able to lock up these brakes right? The brakes dont seem to slow the bike down at all.
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Post by sprocket on Oct 9, 2010 20:14:04 GMT -5
Nope ...the brake that does the work is the front brake. The rear brake does very little except stopping the back end from breaking loose...it should bring you to a stop at about 5 mph, that's it...
They don't lock, they barely work actually...
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Post by meta82 on Oct 10, 2010 7:28:32 GMT -5
Wow, I guess the brake is working fine then. I didnt know the back brake is not supposed to lock. Thanks for your help.
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Post by voorhees on Oct 10, 2010 10:29:04 GMT -5
Yes, unlike bicycles you can't lock up the rear brake on a scooter (mine anyway). Bikes weigh around 20 lbs. whereas most scooters are at least ten times that.
Just get used to applying both brake levers with about the same pressure in most circumstances...
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Post by sprocket on Oct 10, 2010 14:10:25 GMT -5
Hi voorhees
Right on.. nice to see another Canuck!
Even on cars there is a valve that routes 80% of breaking power to the front discs and only about 20% to the rear...
When we build racing cars we actually use an adjustable valve, so you can tune the braking between the front and rear brakes. Some drivers like more or less rear brake...
On scooters it is about 85% front and 15% rear.
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Post by voorhees on Oct 10, 2010 19:06:50 GMT -5
Hey what's shakin' fellow Canadian bacon? LOL
Happy Thanksgiving...
What's your ride and your twenty?
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Post by sprocket on Oct 10, 2010 19:22:14 GMT -5
Lifan _ Van
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Post by voorhees on Oct 11, 2010 21:21:13 GMT -5
I envy your extended riding season...
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Post by Bluefront on Oct 12, 2010 3:37:28 GMT -5
I'm somewhat puzzled about some of these posts. Certainly the rear drum brake on a Chinese scoot won't be as powerful as the front disk brake.......and I guess some rear drum setups won't be as powerful as others. But to call the rear brake "almost useless"......very misleading. My Eagle 50 and my Roketa 50 both have an identical-looking rear drum brake. Each will lock up the rear wheel if necessary, when used with the front brake. Using the rear brake by itself (I weigh 235) won't lock up the wheel......but it will stop the scooter fairly well. My guess....there really is a problem with the rear drum brake, that needs to be figured out. FWIW......my first scoot was a '57 Cushman Highlander. It only had a rear drum brake. It stopped ok (I'm still alive).....and would lock up the rear wheel even when riding double. That's why I'm still around.....  |
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Post by sprocket on Oct 12, 2010 17:31:30 GMT -5
The front brake does the stopping the rear brake stops the back of the scooter from coming round, in other words it stops in a straight line... Other than a broken brake spring, or worn brake cam, defective manufactured shoe etc there isn't much that can go wrong... perhaps they need to be adjusted more? You might check that the brake cam actuator is not rotating on the brake cam pin and not fully opening. This can be seen from the outside of the wheel... Attachments:
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Post by meta82 on Oct 13, 2010 10:37:29 GMT -5
I checked the cam and brake cable, both are working properly. I clamped the two brake shoes together and tried to squeeze the rear brake.. It wouldn't budge. Now, I noticed the grey powder on the brake pad is coming rubbing off from the inside of the drum. Is this supposed to happen? I thought the brake pads are supposed to wear, not the inside of the drum..
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Post by Bluefront on Oct 13, 2010 11:26:20 GMT -5
Humm....I doubt you're seeing any dust from the drum itself. I'd be tempted to find a new set of shoes. Perhaps the composition of the friction material is too hard for whatever reason, and not gripping properly.  |
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Post by meta82 on Oct 13, 2010 12:55:04 GMT -5
Nope, I am sure its from the drum. The brake pads are made of a green material. I tried sanding the inside of the drum with fine sandpaper to roughen it, and the same gray dust that is on my brake pads came off from the drum. It feels as if this powder is causing the brakes to slip, but I cant be certain as I have not ridden another scooter that I could compare rear brakes with.
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Post by sprocket on Oct 13, 2010 17:05:50 GMT -5
I agree with bluefront for what they cost.. just replace the shoes...could be a bad production run or something...
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Post by meta82 on Oct 13, 2010 18:50:23 GMT -5
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Post by sprocket on Oct 14, 2010 14:57:05 GMT -5
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