Spongy V Brakes

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Spongy V Brakes

Postby SmellyTofu » Wed Jun 27, 2012 3:40 pm

Ever since I bought the bike on my wife's flat bar, the brakes have always been spongee. 1/3 of the travel of the brake lever got the pads to touch the rim, but you could press another 1/3 more on the brake lever to get the brakes to actually work properly. Given that, I've always had to put the pads really close to the rim so that the lever doesn't go all the way down to the grips for it to do what it's suppose to do. But if I adjust the pads real close to the rim, it makes undoing the brakes to drop the wheels impossible without loosening the pads which will be a hassle should she have a puncture.

Am I doing something wrong? Is that the nature of mini V brakes? or should I change the pads?
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by BNA » Wed Jun 27, 2012 4:13 pm

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Re: Spongy V Brakes

Postby jules21 » Wed Jun 27, 2012 4:13 pm

ensure the pads are mating properly against the rim surface. if they are "hanging off" the edge and only partially contacting, they will feel spongey.
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Re: Spongy V Brakes

Postby SmellyTofu » Wed Jun 27, 2012 4:14 pm

I set the pads up where I'd clamp them tight (and flush) to the rim and then tightened the screw on the back of the pads.
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Re: Spongy V Brakes

Postby jules21 » Wed Jun 27, 2012 4:24 pm

my advice is:
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

It sounds like you want a lever that will pull more cable. Avid speed dial 7 have adjustable cable pull, I don't know if its max cable pull setting is more than the normal v-brake though.

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

So yesterday, I got my Kool stop salmon pads to go on the wife's bike and it does seem like I need more pull from the Shimano levers to the cables than what's available. The brakes themselves are mini V's but if I replace them with say LX or SLX V Brakes, would it help much? The salmon pads making it worse with the tip of the pads that is used to remove water/dirt slightly touching the wheel so that the front wheels don't roll freely. Would I solve it more if I replaced the lever or should I put in some full sized V brakes?
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Re: Spongy V Brakes

Postby il padrone » Fri Jul 13, 2012 10:11 pm

Somebody can correct me if I'm wrong but I thought mini Vs were designed for use with road drop bar levers ie. require less cable pull. If you're having problems with insufficient cable pull then V-brakes would be the worst choice with those levers. V-brakes require even more cable pull.

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.
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Re: Spongy V Brakes

Postby SmellyTofu » Sat Jul 14, 2012 12:15 am

It's a standard Cross City 2W mechanically so it wasn't parted out of something else. Only thing I've done were tyres and rims (same width rims as standard). It just seems like even when the pads touch and grip, there's an extra bit more where either the V Brake arm flexes or the cable has some spring in it.
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Re: Spongy V Brakes

Postby il padrone » Sat Jul 14, 2012 9:05 am

Hmm. Don't know what else would be the problem. Cable stretch should not be an issue, but you could always try a new cable.

Pads aligned flat with the rim? Oh, yes you did it the correct way as mentioned above.
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Spongy V Brakes

Postby RonK » Sat Jul 14, 2012 9:31 am

Standard v brakes will have longer arms and will require even more cable travel.

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

I have a Avanti Blade 4 with Tektro RX3 Mini Vs , Koolstop salmon pads and Tektro RX1.0 levers.(Well the specs say theyre RX1.0) . I dont have any problem with spongy-ness of the brakes and clearance to rims.

If you like I can measure the cable pull ratio at the lever to compare to what you have.

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Spongy V Brakes

Postby SmellyTofu » Sat Jul 14, 2012 12:03 pm

Here's the pads and how close and aligned I have them so far. As in the video, you can see the extra creaking that is the bit where the spongee feel starts.

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Re: Spongy V Brakes

Postby sturmey archer » Sat Jul 14, 2012 9:05 pm

I measured the distance from the pivot to where the cable attaches to the lever on the brake levers and its about 27 mm. The Distance from the pivot to the cable on the calipers is 85mm.
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

you dont have one of those horrible shimano spring things at the top of your v-brake noodle?

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

I ride a "mullet" Disc on the front, V on the rear. I don't use the rear brake much. Today I used it. They are "spongy" I think most cheap V brakes are spongy. I used to have LX V brakes ( the ones like the XTR models that hold the pads parallel to the rim) They worked and weren't spongy.
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Re: Spongy V Brakes

Postby SmellyTofu » Mon Jul 16, 2012 8:39 am

No spring. Just direct line and there's no slack in the cable because the pads do move with the minute touch of the lever.

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

Those brakes wearing those pads brings to mind a male model in Big W catalogue wearing bespoke high heel shoes...they look odd and they won't help the bloke walk any better.

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

in the video, it actually looks as though the calipers themselves are flexing under load(!)

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 the spring in the "brake modulation unit" you normally would not be able to see it, generally its embedded inside the ferrule type thing at the top of the brake noodle. One of these came on my giant crx4 and yours looks oddly big, but kinda hard to see.

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

SmellyTofu wrote:... there's no slack in the cable because the pads do move with the minute touch of the lever ...


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.
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Re: Spongy V Brakes

Postby SmellyTofu » Mon Jul 16, 2012 2:51 pm

http://techdocs.shimano.com/media/techd ... 608747.pdf

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.
Last edited by SmellyTofu on Mon Jul 16, 2012 3:43 pm, edited 2 times in total.
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Re: Spongy V Brakes

Postby twizzle » Mon Jul 16, 2012 3:02 pm

Sounds to me like you have true flat-bar-road-bike brake levers rather than MTB-levers. In which case... your options are to find some 80mm mini-v's rather than the 85mm ones you have, or get the "travel agent" unit to convert to full V-Brake.

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

SmellyTofu wrote:... You'd think there's a spring there but doesn't look like there is in the lever in the PDF above. ...


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 ....

Image

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

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.


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.
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Re: Spongy V Brakes

Postby SmellyTofu » Wed Jul 18, 2012 9:54 am

I wish I could use road brakes but Giant in their mind decided not to provide any hole for road bike brakes in the fork since it's running 700-23 instead of the standard 28s.

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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