V Brake Pad Cemtering
Originally posted in Hybrid section but was suggested I move to this forum. My V Brakes on rear of cycle have an issue with one side pad dragging. I have unscrewed the barrel adjuster, released pinch bolt tension, and then holding calipers together at the rim pulled cable through pinch bolt and tightened, then tightened the barrel adjuster, I hit brake lever and one pad releases and the other hugs the rim. I have re done the above process numerous times to no avail. I removed both calipers, cleaned all up and put all together and the same result. The caliper arm spring tension screw has little effect, I just cannot get enough pressure on the dragging pad to get it off of the rim. My spring tension rod has no real setting as it is located behind a post and the only adjustment I can see is to bend the rod (away from im I assume to increase pressure). Also is the any site that shows the workings of the spring tension, mine is a plastic piece with an arm that goes into the caliper hole with cutouts on one side that I assume take the little arm on the spring so it can be tensioned. All suggestions gretfully accepted.
Have you tried backing off the tension on the non-dragging side of the calipers?
Make sure that the cable housing is free to move and is not forcing the arm toward the wheel, despite what the spring is trying to do. You might detach the cable and housing entirely and see whether the springs and arms move freely on their own.
On many of the V brakes , bending the straight spring works OK
to make the return pressure on the weak side, stronger.
Well I freed up a bit more cable length and took both caliper arms off one more time. I did discover that the housing for the spring with pin is designed to fir in one of three verticallly aligned holes in the frame so that is where my initial spring tension should be focused, I assume top hole is least pressure (am I correct). Please bear with me, I am old and just adjusting from Coaster Brake and single Speed crank technology. Stay tuned for my next installment.
Nope, top hole is more spring force. Have you tried greasing the brake bosses? Excess friction between the boss and the brake arm can cause the problem you're describing.
Really? I've never seen a v-brake pivot straight against the boss, although I've heard they exist.
Originally Posted by Airburst
All I've seen have had a bushing pressed into the brake arm. Bushing goes over the boss, is held in place by the screw, then the arm moves against the bushing.
But a bit of lube will almost guarantee and easy removal later.
happy bike wishes
It's good that you discovered that your frame has 3 different holes in which the spring pin can fit through. Like Airburst said, the top hole will get you the most spring tension on that side (for snapback action, pulling away from the rim), and the bottom hole the least. Having the two sides in different places (top vs. middle vs. bottom) can result in a massive difference in spring tension, resulting in one side getting overpowered and dragging against the rim. Check to make sure they're in the same hole set - sometimes someone will just throw the bike together and have them in different holes. The problem could be as simple as fixing that.
I second the idea of making sure everything is free of grime and rust, as well as properly lubricated. Sheldon Brown says, "First, remove the arms from the studs, and make sure the studs are free of rust. Coat the studs liberally with grease (this is VERY important!)" My understanding is that the V-brakes pivot against their own internal bushings, but nevertheless I've had old bikes with crud all over the pivot points which managed to gum things up to the point of not working.
What I've also seen happen on some bikes is that, when the screw goes in to hold the brake unit into one side, sometimes the washer gets deformed or smashes up against the brake unit somehow and it causes massive friction. I usually grease both the screw threads and the washer for rust resistance anyway. As you reassemble and are putting the screw in, re-seat the spring, and check to make sure that the arm can move freely as you finish tightening the screw. If it starts to bind up as you tighten the screw, try flipping the washer around 180 degrees. If that fails, try to tighten the screw only as far as you can without restricting the motion of the arm on that side. (Or try a different washer if needed!)
When everything's put together, keep the brake's quick release disconnected, and simply feel the springback tension on both sides. Just push in with your hands and feel the resistance, let spring back, repeat a few times. It should feel roughly even on both sides. If it isn't somewhere close, there's no point in even reattaching the quick release yet, cuz something is goofed up.
If you can get the tension somewhere in the same neighborhood, you're good. Like HillRider said, you can then micro-adjust the tension with the spring adjustors on each side. You can make one side stronger (to pull away farther from the rim) or accomplish the same thing by making the other side weaker - unscrew on the other side to make it move closer to the rim.
A last resort is bending the V-brake springs. Even very good bikes sometimes need spring-bending to be properly set up. Try everything else first and get back to us if you need suggestions on how to do that.
I have, mostly low-end ones. For some reason it seems to be more common in conventional cantilevers.
Originally Posted by dabac
V Brake Centering
Thanks to all. After removing both calipers, cleaning and lubing all components, relocating the spring tension pin (more pressure hole) and freeing up a bit of cable from the brake lever to the pinch bolt and reassembling all. I have a non-dragging brake system, I wish I had a bit less cable travel as I brake, but I can live with the current situation.
As Willoy Sang On The Road Again.
happy bike wishes
Congrats on getting the brake units centered!
What do you mean by you wish you had less cable travel? Do you mean you have to pull the lever pretty far before the brake pads engage on the rim? Ideally, you want to start getting braking action at an early point in the pull, maybe at 1/4 or 1/3 of the range of motion of the lever, and then it should eventually come to a complete halt in motion well before the lever bottoms out against the hand grip, no matter how hard you squeeze it. Of course, stuff may need some tweaking before you can get everything to that point.
Originally Posted by VABEAR
Was that your issue? Do you want/need tips on anything else?
Old guy back. Here is where I am. I popped the sheath for the brake cable out of the frame bracket (my bad) to get a bit more cable at the pinch bolt. I have inserted the cable sheath in the frame bracket and the little gusset that the cable comes out of is now well South of the frame bracket and I do have a ton of cable at the pinch bolt. When I took the brake arms off to clean everything up a washer fell out and I am unsure of where it goes as I have no diagram for the workings of the spring tension assembly.
the spring tension assembly has 1. A plastic cassette with a arm on the backside that I assume goes into one of the frame holes to determine spring tension. 2. Wells on the opposite side with a cavity for the small arm on the spring and of course the tension screw.
I am wondering if the washer with a slot in it goes on top of the cassette and the spring then rides on it a with the spring arm through the slot in the washer and then into the cavity in the cassette. Again remember you are dealing with coaster brake mentality here.
Any suggestions greatly appreciated.
She lives. After too many hours adjusting and readjusting cable and cleaning and reinstalling brake levers I took a close look at the wheel and Voila she had a broken spoke. Took wheel off, replaced spoke and made sure the wheel ran true, put her back together and we are good to go, Again, thanks to all for your advice.