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Misc. beginner questions about a crap MTB

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Misc. beginner questions about a crap MTB

Old 09-01-12, 09:37 PM
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Turtle Speed
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Misc. beginner questions about a crap MTB

Working on some juniors mountain bike and just want to make sure I'm doing things safely.

Firstly, I'm taking a look at the brakes on this thing and trying to get the V-brake centered. The spring adjuster doesn't look like the types I've seen before; as as matter of fact, I'm not sure I see it at all. At least I don't see the usual X-head screw that I'd expect to. Take a look at the attached photo - is that thing I have circled the screw adjuster for the brake centering (spring tension balancing)?



The little circled things feels like it can be turned with a tiny allen wrench. (2mm? I can't remember for sure, something around there.) Is it simply an alternative form of screw? Just making sure...
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Old 09-01-12, 09:39 PM
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That looks like it to me. 2mm sounds about right.
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Old 09-01-12, 10:27 PM
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Thanks so much! I'll play around with them. I want to say one side is almost bottomed out and the brake still isn't centered. The other side is quite far out, and I'm afraid to unscrew it any more for fear it'll fall out and I'll ruin something.

Sounds like I may have to get good in a hurry at bending brake springs.




........................................................................



So another problem is that the lever on one side feels "spongy" and doesn't retract sharply. Instead it makes that lame, squeaky, slower movement back after being compressed and released, and sometimes it doesn't want to retract completely at all. My understanding, through surfing old forum threads here, is that there is probably some sort of friction element involved which is keeping it from sliding back smoothly.

My tentative plan is to check stuff out. I don't think the cable is rusty or gritty because it's so new. But I'll inspect the housing shape, oil the cable, make sure it's seated properly in the lever and everything. Is this a sound plan for trying to fix this, or is there something else I should be trying first?
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Old 09-01-12, 11:09 PM
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I would take the brake arms off, and inspect the springs, and make sure that the springs on each side are in the same holes.
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Old 09-02-12, 07:57 AM
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While you are inspecting the housing check the condition of the ends to be sure that they have been cut or ground flat and the openings have been rounded out with an awl or similar. Also be sure that the correct ferrules have been properly fitted. Be certain that the housing is free to move and is not pushing your brakes to one side. The adjusting screws can only apply limited force towards centering the brakes and may not be able to counteract strong pressure from the cable.
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Old 09-02-12, 07:59 AM
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Quick and dirty way: pop the weak spring out from behind its peg and give it a tweak.

Win.
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Old 09-02-12, 08:38 AM
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Originally Posted by Turtle Speed View Post
So another problem is that the lever on one side feels "spongy" and doesn't retract sharply. Instead it makes that lame, squeaky, slower movement back after being compressed and released, and sometimes it doesn't want to retract completely at all. My understanding, through surfing old forum threads here, is that there is probably some sort of friction element involved which is keeping it from sliding back smoothly.
As with most parts of a bicycle the brakes are a system of interacting components. The lever retracts as a result of the brake caliper pulling on the cable due to the spring tension. If the lever does not retract easily on its own then there is something in the three components that is preventing that from occurring. If you compress the caliper by hand and it resists firmly and springs back you've eliminated the caliper. If the lever moves back and forth freely when you move it both ways by hand then you've eliminated the lever. That leaves the cable. If the inner wire has any significan rust on it or is badly kinked replace the cable and housing, as the housing will have problems as well. Follow instructions on the Park site, sheldonbrown.com, etc. For someone who has not done a procedure before I suggest studying several sites/videos as almost all leave something out.
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Old 09-02-12, 08:57 AM
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Originally Posted by Turtle Speed View Post
.............Sounds like I may have to get good in a hurry at bending brake springs.
,.......
Some cheaper V-brake & Cantilever brakes don't have balancing screws. Gently tweaking the arms out until they're balanced is your only choice. Not what I like to do, but what needs to be done. If one pads hits the rim before the other you will get the spongy feel. Eliminate all other causes before you start bending springs.
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Old 09-03-12, 12:02 AM
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Thank you for the advice, everyone. I will definitely put it to use the next time I'm able to poke around and really work on this thing.

Originally Posted by Kimmo View Post
Quick and dirty way: pop the weak spring out from behind its peg and give it a tweak.
That's a neat idea. Quick question if I am forced to resort to spring-bending in this matter: you would bend said spring AWAY from the centerline of the bike to make it STRONGER, is that right? NOT bend it TOWARDS? Can I just grab the things with my hands, or should I use pliers or a wrench?

Also, dumb question, the WEAKER spring is the one whose brake arm keeps wanting to settle CLOSER to the wheel, is that right? (Assuming no friction on the pivot or other complicating factors.) Cuz the stronger it is, the more it wants to spring away?
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Old 09-03-12, 12:21 AM
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Here's another dumb question while I'm on a roll... After a brake cable has the little end-cap clamped onto it (the thing that prevents the fraying of the wires at the end), is it possible to still remove the cable completely without cutting off this end-cap?

Like let's say I wanted to just remove the brake cable to inspect that it was seated in the lever correctly, maybe give it a little oil coating before I put it back in. How would I pull all the stuff off the wire (housing, brake noodle, etc) while the cap is still on the end? Do I have to resign myself to snipping and replacing it, and losing an inch of brake cable off the end in the process?
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Old 09-03-12, 02:24 AM
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Originally Posted by Turtle Speed View Post
... After a brake cable has the little end-cap clamped onto it (the thing that prevents the fraying of the wires at the end), is it possible to still remove the cable completely without cutting off this end-cap?
The end cap is known as a ferrule, and it has to come off if you want to pull the wire out again.
When I use low-end cables(galvanized), I solder the end to keep it from fraying instead. That way you have both fray prevention and the option to disassemble.
Stainless steel cables are harder to solder seal, but doable for those with the right tools and a stubborn streak. Some dribble superglue on the end instead.
If you use a proper wire cutter or a Dremel cut off wheel, fraying at reassembly becomes much less of an issue.
I've had good luck persuading the ferrule to come off by gently pinching it at opposite angles compared to the 1st pinch.
Either way, it shouldn't lose you 1". 1/3" or possibly 1/2", which should leave you with 2-3 disassembly/reassembly sequences for a cable anyhow.

Lubing is a so-so thing.
With old steel-on-steel housing it pretty much was a must, but with today's lined housings it become a somewhat questionable practise. Lube can easily become gunked up, and freeze solid when it's cold.
I still prefer to give my cables just a thin sheen of something anyhow.

Inspection should be doable w/o cutting the ferrule. Unhooking/unclamping the cable should give you enough slack to slide the housing sections a couple of inches either way to inspect seating.
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Old 09-03-12, 02:43 AM
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Originally Posted by Turtle Speed View Post
..if I am forced to resort to spring-bending in this matter: you would bend said spring AWAY from the centerline of the bike to make it STRONGER, is that right?
Right. Farther away makes the spring engage sooner.

Originally Posted by Turtle Speed View Post
NOT bend it TOWARDS?
No. Towards the centerline will make it engage later.

Originally Posted by Turtle Speed View Post
..? Can I just grab the things with my hands?
On a v-brake with exposed springs, the end is quite long. Easy to hold on to. I'd do it hands only. But I'd start with pulling the brake arm off and see if the anchor point could be moved first. It's only an Allen key away anyhow.

Originally Posted by Turtle Speed View Post
... the WEAKER spring is the one whose brake arm keeps wanting to settle CLOSER to the wheel, is that right?
Right.

Originally Posted by Turtle Speed View Post
..Cuz the stronger it is, the more it wants to spring away?
Right.

Originally Posted by Turtle Speed View Post
....Assuming no friction on the pivot or other complicating factors.
In the overwhelming majority of cases, the brake arm doesn't pivot against the brake boss directly. There's usually a bushing pressed into the brake arm that the arm pivots around. The bushing goes over the brake boss, and the mounting screw clamps it in place.
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Old 09-03-12, 02:52 AM
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Originally Posted by Flying Merkel View Post
... If one pads hits the rim before the other you will get the spongy feel.....
I don't quite agree with that.

As both arms are free to move, you can't put any real power into the system until they've both made contact.
It'd have to be one amazingly stiff, almost seized brake arm, for a dragging brake arm to introduce a spongy feel to the system.
Or an amazingly sensitive rider of course.

Spongy feeling IME, is usually more due to quality of cables, and cable installation, or simply flexy brake arms/frame/fork.
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Old 09-03-12, 09:24 AM
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Originally Posted by dabac View Post
I don't quite agree with that.

As both arms are free to move, you can't put any real power into the system until they've both made contact.
It'd have to be one amazingly stiff, almost seized brake arm, for a dragging brake arm to introduce a spongy feel to the system.
Or an amazingly sensitive rider of course.

Spongy feeling IME, is usually more due to quality of cables, and cable installation, or simply flexy brake arms/frame/fork.
Maybe I am amazingly sensitive.

There is no one cause for sponginess, which is a very subjective term. When the pads are correctly adjusted and hitting the rim properly, the brakes feel solid. If the cables are binding, the brakes have a "wooden" feel. All of these terms don't have any set meaning.

I've dealt with Shimano XT V-brakes and WallyWorld spec brakes. The cheapies are harder to get set up, but they work well enough.

Turtlespeed, sounds like you got the concept. Be gentle tweaking springs, once done, they can never be re-done. Spring bending is the LAST thing you do to the brake system when all else is tried.
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Old 09-03-12, 09:31 AM
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Super glue is a good solder alternative for sealing cut cable ends.
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Old 09-03-12, 01:37 PM
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I would trash those brakes and get V-Brakes with threaded-stud brake shoes. Even a cheap Avid SD3 V-Brake would be better than those that you have.
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Old 09-03-12, 09:37 PM
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Originally Posted by Seb71 View Post
I would trash those brakes and get V-Brakes with threaded-stud brake shoes. Even a cheap Avid SD3 V-Brake would be better than those that you have.
IME a single pressed steel V-brake of the crappest quality imaginable is strong enough to smartly pull up a seven-seater, six-wheeled 500kg behemoth, albeit at an alarming rate of pad wear.

So IMO the only reasons to upgrade v-brakes is ease of setup and bling factor.

Originally Posted by Flying Merkel View Post
Be gentle tweaking springs, once done, they can never be re-done. Spring bending is the LAST thing you do to the brake system when all else is tried.
That runs counter to my experience with V-brake springs; IME they can be tweaked as much as you like, although on some designs the brake has to be disassembled (or at least the wheel removed) to make them softer. And on the crappiest brakes where the centering mechanism often isn't worth a damn, I find it saves time to just go straight for the tweak.

Last edited by Kimmo; 09-03-12 at 09:41 PM.
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Old 09-04-12, 12:20 AM
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Originally Posted by Kimmo View Post
So IMO the only reasons to upgrade v-brakes is ease of setup
Ease of setup would be a good enough reason for me in this case, when the upgrade does not have to be expensive.
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Old 09-04-12, 10:21 PM
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Thank you, everybody, for the help. You are all incredibly patient with me, and your tips are golden. I used many of them in this very project. The theoretical stuff was extremely useful too.

The spring adjustor on these types of (slightly weird) v-brakes was indeed a 2mm allen, and it worked just as expected.

About the centering, one issue was that the brake arm on one side had been mounted into the lowest hole, so the springback power was awful. This surprised me, because the bike had a bike shop sticker on it and was in fairly new condition, and I never would've guessed they would put the brake arms into 2 different spring holes like that.

The spongy brake lever issue ended up being a huge headache. I removed, inspected, cleaned, & lubricated the brake unit itself, just for good measure and for experience, but I couldn't figure out how to get it back on the bike properly. The v-brakes are weird in that the spring doesn't travel up the body of the arm, but stays all coiled up in an alternative type of design, and it kept popping out of the hole when I was trying to get them back on the bike. I managed to snap some plastic housing in the process, but superglue to the rescue.

It was in the middle of all that confusion that I kept getting distracted by the lever issue. In testing, it would snap back sort of OK... for a while, but then 2 minutes later, it would be mushy again. Because the brake spring kept popping out of place, I assumed it had something to do with that. I worked til I was exhausted, slept on it, tried the lever in the morning... and it's working now? But then 5 minutes later, it's mushy again? Finally I had the presence of mind to take the cable all the way out again and check the free action of the lever. It felt spongy and even made quiet squeaks. Needing to run to work, I blasted some WD40 into the lever innards out of frustration.

It worked immediately. Now it snaps back like a champ.
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Old 09-04-12, 10:36 PM
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So some more dumb questions about centering the back wheel. I watch videos of people popping QR wheels back in under 15 seconds and I feel like an idiot spending 20 or 30 minutes on mine with axle nuts. And I can't seem to find any Idiot's Guide to Putting Back Wheels With Nuts On.

My main problem is getting the wheel centered properly. It seems like for this type of bike, the right dropout is always shorter than the left. If I put the wheel all the way in to the back of the dropouts, the wheel is way crooked off to the left. Am I supposed to "seat" all the way back on the right side first, and then slide the left side of the axle forward or backward in the dropout to adjust the centering of the wheel?

A complicating factor is that when I go to tighten the axle nuts, the wheel wants to squeeze to one side or the other as the tension is increased. I have a heck of a time keeping it centered while cranking up the tension.

Here are some pictures of my finished product of a centered(?) back wheel. You can see that the left nut is pretty far forward in the dropout. Is it too far forward? Is it unsafe? I just wanted to make sure I'm doing everything correctly before some kid has a massive faceplant due to my error.









Does this look right? Wrong? Should I be worried that the left nut is that far forward in the dropout? Any comments VERY much appreciated.
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Old 09-04-12, 11:06 PM
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Drop the wheel in, making sure the right side is in all the way. Snug up the right wheelnut, about double or triple finger-tight.

Grab the wheel between the chainstays, and centre it, then do up the the left wheelnut a bit harder than the right. Now crank the right wheelnut fully tight, then the left.

Derailleur claws are a PITA.

Also, if the wheel isn't centred between the seatstays, either the wheel's not dished right, or the frame isn't straight. Flip the wheel, and if it lines up in the same spot, it's the frame's fault. If the position is mirrored, it's the wheel's fault. If it's between, it's a combination of the two.
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Old 09-05-12, 03:24 AM
  #22  
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Originally Posted by Turtle Speed View Post
You can see that the left nut is pretty far forward in the dropout.
That bike, as Kimmo writes, is equipped with a derailleur claw. Means that instead of being attached via a tab that's a part of the frame, the derailleur clamps under the wheel nut, with a small retaining screw lurking in the dropout. This will automatically mean that the left nut will sit farther forward.

Originally Posted by Turtle Speed View Post
Is it too far forward?
If the right side is pulled all the way back, then that's where it needs to be.

Originally Posted by Turtle Speed View Post
Is it unsafe?
In itself, no. Has to be that way. Untold amounts of bikes have that design, and they fail to kill or maim their rider b/c of that on a very regular basis.

Originally Posted by Turtle Speed View Post
Any comments VERY much appreciated.
Well...

That design is a sign of low-end bikes. I've seen a few where the dropout plate has been so thin/soft that the slot started to widen and squish when the nut was tensioned. Not a good thing.
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Old 09-05-12, 11:04 PM
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Thanks again for the advice! Couldn't have finished this project without you guys. You are creating tons of good bike karma.
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