Bicycle Mechanics - Front wheel locks up due to brake problem
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08-09-10, 08:21 PM
I am currently using a Motobecane Mirage from the mid 70's (I think). It has Weinmann 610/Vanqueur 999 brakes. Before I was able to safely ride this old bike, I had to take it into the shop where the replaced the brake and shifting cables and installed new brake pads in the rear.
It worked very well for a while but now a new problem has arisen. Be forewarned that I don't know a lot about bikes so I might not be describing the problem accurately. On the brakes there is a sliding mechanism which moves in place when I apply pressure to the brakes. Look at the pictures below. In the rear, there is a red plastic piece which keeps the mechanism in place, but on the front, this cap has come off and the sliding piece is outside of the socket.
The problem with this is that when I turn front of the bike too sharply, the entire front wheel locks up and doesn't turn, which could be very dangerous. There is also some metal scraping off of the brake due to the misalignment.
If it makes a difference, the wheels say Chromage Superchromix, Rigida, 27x1¼ (HP), Made in France. The tires are Bell Streetsters.
At this point I have had such problems with these brakes that I wonder if I should get an entirely new system. If I do so, what do I look for in a new (but cheap) brake system? As in, what would fit this bike?
But, of course, if I could simply salvage what I have without having to spend the extra money, that would be great. Any suggestions?
08-09-10, 08:56 PM
Some guy on Yahoo Answers just said my link doesn't work (I can't respond to things on there so I'll do it here). I'm not sure what that means. Could someone clarify?
08-09-10, 09:13 PM
The link to the pictures works fine for me.
First off what you have there are called center pull caliper brakes. The center pull signifies the way the cable pulls on the V straddle cable to move both arms at the same time. The caliper part signifies that it's a one bolt style mount vs post mount center pull brakes. Just something to lock away for next time.
The red ball or roller is a gizmo that aids in the two arms moving in a more coordinated manner. But lots of center pull brakes work just fine without this little "trick". The key is to set the caliper and the straddle cable up so that both arms move evenly as the center cable pulls. You do this by altering the angle of the fixed arm that the bolt secures to the bike. That'll alter how the return springs tension the arms. Just loosen the attachment nut slightly, twist the whole assembly and then re-tighten. Test for proper and even operation and try again if it's not quite right. Along with this you'll want to slide the straddle cable back and forth in the connector plate if it's not pulling evenly. You may need to straighten some kinks in the cable to do this but don't get carried away. If you start to snap strands in the straddle cable then you'll need to find a new one.
Now your other issue of the wheel locking up is a different one. Obviously your front brake cable is becoming bound up in some way and the cable is tightening. There is supposed to be a hanger where the housing stops and the cable extends down to the joiner plate for the straddle cable. If that hanger plate is not turning in unison with the handlebars then the bike shop put things back together wrongly and you'll need to take it back and have them correct this. Or if all looks well but the cable is hanging up on some other part that does not turn with the front wheel then again you'll need to correct that.
Perhaps add some new pictures of the front end assemby showing the whole path of the housing and cable from the front brake lever all the way to the caliper. Something may pop out if you still need help.
The link works for me.
Take it back to the shop? - maybe they have an old centerpull brake to replace yours.
You could release the cable from the brake and see if you can move the arms around to realign them.
Don't know if the alignment nub will function correctly without the plastic cover.
08-09-10, 09:27 PM
I'd take them off and see if they move well around their 2 pivots, well, independently of everything else .
short of that see that the bushings [of red plastic] are intact ant hey get a drop of oil once in a while ,
Phil Tenacious oil stays in place well .. I even use it in my 3 speed hub.
is the cable hanger at the top of the fork moving, if it does, the distance to the the brake for the cable has to go further, and would pull up the short cable on the caliper..
picture 4 0f 6 shows there is the end of the main cable the end of which is between the arms .
take it out of there .
it may be interfering with the motion of the arms . there is a pin on the back of the Front arm, and a slot in the front of the back arm. they are supposed to fit together..
08-09-10, 09:50 PM
.....is the cable hanger at the top of the fork moving, if it does, the distance to the the brake for the cable has to go further, and would pull up the short cable on the caliper..
Um..... it is SUPPOSED to move. Or did you mean moving on it's own so it wanders back and forth? It needs to be locked to the fork motion so it turns with the handlebars and keeps the distance from the hanger to the caliper the same.
09-13-10, 02:21 PM
So it turns out the cables that go to the gears were too long and were being caught on the arms of the brakes. Pretty simple now that I know! I took it into the shop and they simply put shorter cables on it. Problem fixed!
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