Spongy V Brakes
- SmellyTofu
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Spongy V Brakes
Postby SmellyTofu » Wed Jun 27, 2012 3:40 pm
Am I doing something wrong? Is that the nature of mini V brakes? or should I change the pads?
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Re: Spongy V Brakes
Postby jules21 » Wed Jun 27, 2012 4:13 pm
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Re: Spongy V Brakes
Postby SmellyTofu » Wed Jun 27, 2012 4:14 pm
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Re: Spongy V Brakes
Postby jules21 » Wed Jun 27, 2012 4:24 pm
1. set the pads up close to the rim
2. set them up with the barrel adjuster on the lever screwed out a fair way. when you want to drop the wheel out, you can tighten the barrel adjuster (which loosens the cable), which will give you enough slack to pop the cable housing out of the caliper mount (which allows the caliper arms to spring free).
my wife's bike has the same problem and that's the solution i settled on.
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Re: Spongy V Brakes
Postby eeksll » Wed Jun 27, 2012 11:14 pm
I have finally got my v-brakes set up the way I want them, and I need to do barrel adjuster wind in to get the v-brake loose. I dont have the 1/3 hit rim, then 1/3 more before brake working issue though.
Just thinking here, not sure if it will work, If a flat is the only reason for removing the wheel, you might be able to deflate tyre before removing the wheel, this should not require yo to undo the v-brake. Just make sure you put the wheel in before you pump up the tyre.
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Re: Spongy V Brakes
Postby SmellyTofu » Fri Jul 13, 2012 9:34 pm
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Re: Spongy V Brakes
Postby il padrone » Fri Jul 13, 2012 10:11 pm
Having said all this, it seems strange. Most modern flat-bar levers have the longer pull required for V-brakes. Was this bike supplied as is from the shop, or is it a 'bitzer'? Have you altered the brakes in some way?
If you do change to V-brakes be sure to get the brakes and the levers to match - then you're starting off with the complete set.
"An unjustified and unethical imposition on a healthy activity."
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Re: Spongy V Brakes
Postby SmellyTofu » Sat Jul 14, 2012 12:15 am
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Re: Spongy V Brakes
Postby il padrone » Sat Jul 14, 2012 9:05 am
Pads aligned flat with the rim? Oh, yes you did it the correct way as mentioned above.
"An unjustified and unethical imposition on a healthy activity."
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Spongy V Brakes
Postby RonK » Sat Jul 14, 2012 9:31 am
If the frame is flexing you may need a v brake booster to reduce the flex.
It's also important to ensure you have the pad spacers correctly placed. When the pads contact the rim the arms should be parallel at the point adjacent to the rim. This usually means the tops of the arms are canted outwards slightly.
But what you are describing sounds like the levers don't have enough pull and the mini-v's have been fitted as a compromise.
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Re: Spongy V Brakes
Postby sturmey archer » Sat Jul 14, 2012 9:49 am
If you like I can measure the cable pull ratio at the lever to compare to what you have.
- IanC
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Spongy V Brakes
Postby SmellyTofu » Sat Jul 14, 2012 12:03 pm
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Re: Spongy V Brakes
Postby sturmey archer » Sat Jul 14, 2012 9:05 pm
I take up about about 1/2 the movement of the lever back to the bars before the pads touch the rim (I really should adjust that) and there's a bit of spring in the lever and the calipers after that point, but there's no way I can get it back to the bar without using a huge amount of force.
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Re: Spongy V Brakes
Postby eeksll » Sat Jul 14, 2012 9:13 pm
edit: one of these do-whats they contain a spring to "modulate" the power. I don't know, they might work when new ...
edit2:
the other things that can take up slack is:
a kink in the inner cable, between the end of the noodle and the pinch bolt most likely caused by the pinch bolts previous position.
and also tight outer cables can cause the noodle to hang at a angle different to when under pressure.
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Re: Spongy V Brakes
Postby mitzikatzi » Sun Jul 15, 2012 10:07 pm
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Re: Spongy V Brakes
Postby SmellyTofu » Mon Jul 16, 2012 8:39 am
Mind you the tekro on my flat bar that I don't ride much work fantastically (not mini-v brakes) but given that it will be the family tow bike for a trailer, I'd prefer the better brakes stays on that bike.
Should I be considering new levers before considering new V brakes?
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Re: Spongy V Brakes
Postby silentbutdeadly » Mon Jul 16, 2012 8:49 am
Invest another $30 is a set of Shimano Deore V's or a little more in the previously suggested LX. There's also not much wrong with the simialr Avid versions either. The better return springs inside each side of the V will help no end. No need to replace the lever.
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Re: Spongy V Brakes
Postby jules21 » Mon Jul 16, 2012 1:05 pm
tofu, i think you'll find there is a 'wire' spring on the inside of the caliper arms.
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Re: Spongy V Brakes
Postby eeksll » Mon Jul 16, 2012 1:33 pm
Regarding what to buy, I'd say avid sd7 levers first since it looks like you already have a brake lever unit by itself. I replaced my levers with sd7's, still using the original v-brakes and using nokon cables. The lever stops dead. I now run the "mullet" system with a BB7 disc brake up front (sd7 and nokon cable) and this is spongier than the v-brake setup.
this probably has something to do with the fact that I use the sd7's wound all the way in ie enough pull for the longer v-brakes, (if in fact the longer v-brakes require more pull) I am using this "longer" pull on a mini-v-brake.
I doubt the v-brake arms are the cause of the issue, as I may have alluded to above, my v-brakes are nothing special they came on the bottom of the line giant crx4 3-4 yrs ago and I can get them setup to have less spongy feel than bb7's.
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Re: Spongy V Brakes
Postby eeksll » Mon Jul 16, 2012 1:37 pm
The slack I speak of is caused by a kink and will usually not get taken up till full pressure is applied, not at the start of the lever pull. The way to see if this might be a cause of the issue, is just pull the v-brake arms apart with however much force you deem suitable and see if you can pull them apart any further than the resting position.SmellyTofu wrote:... there's no slack in the cable because the pads do move with the minute touch of the lever ...
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Re: Spongy V Brakes
Postby SmellyTofu » Mon Jul 16, 2012 2:51 pm
You'd think there's a spring there but doesn't look like there is in the lever in the PDF above.
I'll try pulling it apart when I get home to see if there's any slack there.
EDIT: In the meantime, I have put in order for new v brakes F&R (XT given they were only $3 more over LX). Will update here when I've got them and fitted them up. Thanks all for the help.
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Re: Spongy V Brakes
Postby twizzle » Mon Jul 16, 2012 3:02 pm
For 80mm mini-v's, TRP makes them (pricey), the Tektro side of the business used to have some options at 80mm ("BMX") but they don't seem to make them any more.
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Re: Spongy V Brakes
Postby eeksll » Mon Jul 16, 2012 3:39 pm
the spring thing I speak of sits at the top of the v-brake noodle. See below (the black thing in the top left of the picture), the bit where "jagwire" logo is written. Its actually in that black section ....SmellyTofu wrote:... You'd think there's a spring there but doesn't look like there is in the lever in the PDF above. ...
NOTE: my mini v-brake arms are 85mm too.
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Re: Spongy V Brakes
Postby twizzle » Tue Jul 17, 2012 1:57 pm
Without a Problem Solvers "travel agent", those brakes won't work at all. I spent a fair bit of time researching how to convert my cross canti's to mini-V's - you will only be making your problem worse with full size (long arm) V brakes.SmellyTofu wrote:EDIT: In the meantime, I have put in order for new v brakes F&R (XT given they were only $3 more over LX). Will update here when I've got them and fitted them up. Thanks all for the help.
...real cyclists don't have squeaky chains...
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Re: Spongy V Brakes
Postby SmellyTofu » Wed Jul 18, 2012 9:54 am
I have a feeling you're right but with the hidden spring which I think it has, new levers wouldn't solve the problem either. Also I can't believe when you buy levers, there isn't a compatibility table showing what sort of brakes it is suited for. I could have bought brake levers but I have no way knowing if it is suitable for long or short arm Vs.
No big loss with the XTs since I do have a flat bar with full length Vs to fit them to. I might in the end have to transfer the brake systems over to fix it.
eeksll, I couldn't pull the Vs apart when they were at the resting position.
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