# Disc Brakes: Weak Stopping Power in Front????



## bowler1 (Aug 11, 2005)

Hi,
I am running Magura Louis brakes and like them a lot. However I was riding yesterday and tested them front vs. back (one was making some noise and wanted to see which).

When I did so I found that the front brake had very little power. The back was plenty strong and would love up the wheel, but not so on the front. It was significantly weaker. This is contrary to what I remember with the hold Vee Brakes. 

I cleaned the rotors and pads with some alchohol and that didn't help. 

Should the fronts be weaker? Is this something built into the newer disc brakes to help you to avoid doing an endo by braking too hard up front?

Or do you think it's a matter of needing some new pads? I've not changed the pads yet and wouldn't know what to look for in order to tell if they need replacing.

thanks

Matt


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## ljsmith (Oct 26, 2007)

If both of your brakes have the same calipers and same size rotors then they have the same stopping power. But when you brake your weight shifts forward, so that the front brake has to do about 70% of the braking. This is why your rear brake seems more powerful, because it is only having to do about half the work of the front brake. This is true with any type of brake, cantilever, v, or disc. This is also why some people run larger rotors in the front. With that said, a properly set up brake should be able to lock your front wheel. Your pads may be contaminated. You could try roughing them up with sandpaper and cleaning them with alcohol. You may also need to recenter the caliper.


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## insanitylevel9 (Sep 23, 2009)

contaminated pads


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## boomn (Jul 6, 2007)

a tangent I guess, but locking up a wheel is no true indication of power. All you need to lock up a wheel is a quick enough bite to break traction and your wheel will slide, and once your wheel is sliding it is not slowing you down as well as it could without locking up.

Note that v-brakes are often prone to locking up the wheel on steep descents where well-modulated disc brakes can stay within the limits of traction and slow you down _under control_

that said, i agree that your front brake sounds like it has a problem (but a fixable one).


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## sanjuro (Sep 29, 2004)

Locking a wheel is not braking. Controlling your speed is braking.

But when it comes to locking up your wheel, it is much easier to do with the rear wheel. When braking with either brake, your weight moves forward onto the front wheel, as well as the traction. There is not as much weight on the rear wheel, so it is easy to stop it from rotating. 

Try this as a safe example: lean way back then try each brake. You should be able to negate the weight transfer that way.

Not so safe example: go down a smooth fireroad, try just using the rear brake then compare it the power you get with the front brake. 

Final test: take your front brake off then put your rear brake on the front.


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## bowler1 (Aug 11, 2005)

they are the same size calipers. There is less power in the front for sure. I can't even lock up the wheel but can easily in the back.

I will try the sandpaper. Good idea!

Matt


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## bowler1 (Aug 11, 2005)

I agree about locking the wheel. I was using that as an example. During my testing I applied only the front brake and did so full power. If brake is working then I would think that it should have enough power to lock the front wheel up. I would never seek to lock up the wheels while riding. This was just a parking lot test. 

Matt


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## Jayem (Jul 16, 2005)

It's common for people to contaminate their pads. Do not handle te rotors with your fingers, as the oil on your hands will contaminate them/the pads. Do not get any kind of oil on the rotors/pads, be carefll when oiling your chain.

If your lever feels normal (doesn't travel excesively to the bar, doesn't feel mushy) it's probably contamination.

Contrary to popular believe, alcohol does NOT break down the oil. You need acetone for that, and the best method I've seen is a 2hr soak, followed by a rinse with acetone, followed by another 2hr soak. Any longer and you risk eating at the adhesive that bonds the pads to the backing.


Your front brake shouldbe far more effective at slowing you down than the rear, but it should be easier to lock up the rear (less weight on it).


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## krue (Dec 2, 2007)

If they are hydraulic make sure the hose is secured and not flexing on you. The volume of fluid is so small that any flex will show in reduced brake force. I learned this the hard way last week.


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## Magura J (May 13, 2009)

In my experience it plays out like this:
good lever feel + noisy braking + no power = contaminated pads every time. 
There are lots of myths about how to cure contaminated pads (and some might work), but in my experience, just clean up your rotors and calipers as best as you can with alcohol, and replace the pads.


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## sanjuro (Sep 29, 2004)

bowler1 said:


> I agree about locking the wheel. I was using that as an example. During my testing I applied only the front brake and did so full power. If brake is working then I would think that it should have enough power to lock the front wheel up. I would never seek to lock up the wheels while riding. This was just a parking lot test.
> 
> Matt


Let me repeat this again:

Locking your wheel is not braking.

Serious, go down a long fireroad, and try braking just with your rear brake.

Then go back up and try braking just with your front brake.

Tell us what which brake has more power.

NOTE: using one brake is a good way to crash.


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## pewpewpew (Oct 25, 2009)

when you slam on your front brake, do you slow down quickly?

when you slam on your back brake, does your rear wheel lock and skid and you slow down slowly?

test: go at a decent speed, lean back, slam on one brake, measure the difference. Repeat the process with the other brake.

I bet you'll see that your front brake doesn't lock up, but your stopping distance will be much less. i've always found it pretty hard to lock up the front brake on a good surface. I bet if you do finally lock it up you'll eat it.

unless there is actually something wrong with that brake, in that case i'm going with contamination.


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## Harold (Dec 23, 2003)

if you grabbed your lever enough to lock your front brake, it wouldn't skid...you'd lose control, most likely go OTB, and get yourself hurt. even in a parking lot.

but you'd have to be hauling pretty good for that to happen. if you're not going fast enough to crash, you won't ever lock up the front wheel because there's so much of your body weight and momentum gluing your bike to the ground.


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