Brake problems

[mrbaggins]

Hey all. Not as new as I seem. I joined just before the server got rolled back, so had to rejoin. Thanks for the help so far

But today's issue.
I have a freebie bike I'm fixing back up. It's a cheap 'kmart' bike I think. I've gotten the wheels fixed up (bearings and true-edness), put tubes and tires on em, and now my bike is starting to look more bikelike. (Cost of bike to date, $48)

But I'm having large issues with the brakes. Besides not having rear brake pads (will fix this tomorrow) the front ones are causing me no end of trouble.

I started at the top, and discovered that the lever had waaaay too much give in it, so tightened the cable. But now the pads are hitting the wheel. I loosened it off to a point where they don't, but as soon as I use the brakes once, the right hand one keeps rubbing.

If I loosen the cable enough to stop this, I can't pull the lever all the way in as it reaches the handlebars before full pressure is applied.
If I tighten it, it rubs (only on one side).

I tried moving the springs to the 'higher tension' hole, so it pulls back out easier, but this didn't really help. The right one rubs, the left one doesn't. I can manually move the arms so that neither do, but on next use, they rub again.

There is a screw at the bottom of the brake arm which apparently, according the internets, is the solution to all my woes. It doesn't do anything. It appears to just be a screw I can do up or ignore at my choosing. I even removed an entire brake arm to see what it does. And while it LOOKS like it's supposed to do something with the spring arm, all it does is wind the screw in. Am I missing something?

[gregaudio]

Can you find out what brake type it is? This would help a lot. Try type into Google Images some terms like...

Bicycle caliper brake
Bicycle center pull brake
Bicycle cantilever brake
Bicycle V brake
Bicycle disk brake

and tell us which one it looks most like.

[Nobody]

The problem you are having with the (likely) V brakes usually can only be fixed with a brake upgrade for the really cheap bikes. You may have to replace both the brakes and levers. The front brake is the most important on a road going bike.

http://www.this link is broken/Mode ... delID=1237

Alternatively, a better bike would be a lot easier to deal with and likely safer too.

[il padrone]

That little screw is your answer. It sets the centering of the brakes, by fine-tuning the spring tension.

Whichever side is rubbing on the rim, tighten up the screw on that side a few turns. On the other side undo the screw a few turns at the same time. Keep playing with it until you get it right. It should work out.

If there continues to be a real problem it is possible to rebend the spring outwards to make sure the brake arm releases, but this is a bit more radical.

[scotto]

That little screw is your answer. It sets the centering of the brakes, by fine-tuning the spring tension.

Whichever side is rubbing on the rim, tighten up the screw on that side a few turns. On the other side undo the screw a few turns at the same time. Keep playing with it until you get it right. It should work out.

If there continues to be a real problem it is possible to rebend the spring outwards to make sure the brake arm releases, but this is a bit more radical.

+1

[mrbaggins]

Sorry, yeah, it's V-brakes.

I played with the screws a bit before last post, and it didn't seem to do anything. I'll give it a go again this afternoon after work with that specific advice. Then I'll stick the spring arm in the vice.

If that doesn't work, I'll buy a new set I guess.

Thanks for the help.

[familyguy]

Some of the lower end brakes just dont adjust at all. There should be three spring positions in the frame, so turning the brake arm to slot it into the tighter position might help too.

Jim

[mrbaggins]

Yeah, I'm thinking this screw is just there for show.

Will try a couple of things...

But the bigger problem is the cable/lever.

The range of movement on the lever is not enough to apply decent force to the brake without the brake pad sitting extremely close to the rim in the off state.

It's a toss up between leaving clearance, or having the lever arm touch the handlebars. Is next-to-no clearance pretty common?

[mrbaggins]

Just a big thanks to everyone in this thread and the one lost to the server rollback.

Got the brakes working. Eventually detached the entire caliper/lever arm part, which helped me work out why the tension screw wasn't doing anything. The spring is kept on a separate ring on the bolt to the actual arm, and these two parts had become separated, and the ring was able to rotate pretty much freely, so doing up the screw didn't do anything, as it had nothing to push back against when it tightened the spring.

I also managed to pick up a pair of pads for the rear, so now have a full functional brake system on the bike.

Between that and adjusting the rear derailer this afternoon, all I have left now is to adjust the front derailer and tighten the handlebars. (If you put a foot either side of the front wheel, you can turn the handlebars still)

Side question: My rear derailer is EXTREMELY difficult to get into the lowest gear. It also appears that the derailer doesn't have a b-tension screw. Is this common on cheaper rigs? It's a shimano derailer, but only on a 'kmart' bike (Dunlop Scimitar). To get onto the largest sprocket, I have to turn the shifter to "1", then push it past it to get it onto the sprocket. It will sit there happily once on though. Twisting the shifter at this point has a LOT of resistance. The cable is quite slack in 6th though. Could it be worth getting a new cable/cable sheaths for it?

[gregaudio]

Sounds like a case of cable tension adjustment. Check out this video from Bicycletutor.com

http://bicycletutor.com/adjust-rear-derailleur/

[Nobody]

It also appears that the derailer doesn't have a b-tension screw. Is this common on cheaper rigs?

Yes.

[mrbaggins]

Sounds like a case of cable tension adjustment. Check out this video from Bicycletutor.com

http://bicycletutor.com/adjust-rear-derailleur/

That's the site I was using, which led me to discover the absence of the B-tension. I'm thinking it's a tight cable/cable housings that have gone 12 months without any lube and have ceased a little. But it functions well enough for what I need (I can now get all 18 gears, it's just getting the lowest ones can be painful.

I never knew so many bits of a bike were just interchangeable. I'm considering switching the shifter style completely. These ones are like sleeves that rotate around the handle.

[gregaudio]

With the rear derailleur at the smallest cog (highest gear) and the cable tensioner(s) screwed all the way in, there should be no slack on the RD cable. If your cable is slack at this setting then you need to undo the cable anchor bolt on the derailleur and re tension the cable (making sure the gear leaver is set to the highest number). This is also a good time to set you high "dead" screw to enable the top derailleur jockey wheel to be nicely aligned with the smallest gear cog . Once the RD anchor bolt is re tightened try changing one gear position towards the lower gears. In most cases you may need to adjust the cable tensioner to achieve a clean change. If the gears are reluctant to climb to a larger cog with each shifter click then you need to back the cable outer away from the derailleur for more tension. If you adjust a bit too much then the opposite may begin to occur and the gears change to larger cogs nicely but are reluctant to come back with a reverse click, then you have too much cable tension and need to adjust the outer slightly closer back to the RD. It's generally recommended to only make a small adjustment each time so as not to "overshoot" the right setting.

It is possible to set the cable adjuster so far that while the gear indexing works nicely, the whole thing is one gear out and you can no longer get down to the smallest cog. After some time your gear cable may stretch and need to be re tensioned, this is normal and most likely where you are at right now.

Once the indexing is set correctly you should also check the low gear "dead" screw to make sure the derailleur doesn't want to take the chain into the spokes when you select #1

Watch the video again, particularly the last part about cable tension.

[mrbaggins]

It's not 'slack' so much as a lack of tension (which is what the video says should be the case).

Although I'll have another look and use your advice to go through the steps again, to see if I can get it any smoother/easier. Thanks.