# Harsh downhill = squeaky disc brakes?!



## capoz77 (Sep 14, 2006)

Hey guys, 

Did some long flowing downhill which at some points required a lot of dragging the rear disc brake to slow down my speed. Towards the bottom of the hill a squeaking noise started form the rear disc, like the pads were rubbing. 

After burning my hand on the red hot disc trying to investigate  (is it normal for them to get this hot?) I couldn't figure out what was the problem. 

For the rest of the ride the rear disc continued the annoying screech :madman: 

Also after todays ride when spinning my front wheel off the ground my front pads are rubbing.

I have Hayes Hydraulic HFX-9 XC on my 2005 Kona Coiler. 

Only advice I could find was below which sounds great although I don't understand how this would work since there is no play in the disc itself to push the pads in?

"Here's a simple hydraulic disc brake adjustment procedure for the savvy mechanic. Squeeze the brake lever with one hand and push the brake rotor side-to-side first toward the spokes and then toward the fork leg by grasping the rotor with a clean hand at or near the caliper. This forces both brake pads to follow the moving rotor and relocate in the caliper. Where you let off the brake lever is where the pads will newly reside. This is an easy way to make subtle adjustments in order to stop errant pad rubbing and noises."


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## keen (Jan 13, 2004)

capoz77 said:


> Hey guys,
> 
> Did some long flowing downhill which at some points required a lot of dragging the rear disc brake to slow down my speed. Towards the bottom of the hill a squeaking noise started form the rear disc, like the pads were rubbing.
> 
> ...


 If you really overheat the pads and rotors they can squeal. Try de-glazing the pads / rotors w/ some light sanding then an alcahol cleaning. First use the front brake to slow down , rear for turn control. 2nd. if you have 6" rotors consider 8's.


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## SHIVER ME TIMBERS (Jan 12, 2004)

lightle sand the rotors and pads......learn to lay off the brakes more


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## f0ggy (Jul 5, 2006)

Thoes breaks arnt ment for dh, try upgradeing your breaks to hayes mags, or avid juicy 5's or somthing along the dh line.


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## XSL_WiLL (Nov 2, 2004)

That's how brakes work. They convert mechanical energy into other forms such as heat. Disc brakes get hot. If you don't believe me, touch your car rotors after romping around the block for a few minutes.

Learn to brake in intervals and only when neccesary.

Larger rotors will help to dissipate heat more quickly.


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## brokenbikes (Oct 3, 2006)

Also, if you find the rubbing is only on a certain section of the rotor, and not a constant whine, you may have slightly buckled the rotor (DH riding/braking is quite stressful - especially for XC brakes). You can carefully bend back the trouble spot on the rotor using an adjustable wrench if thats whats happened...


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## capoz77 (Sep 14, 2006)

some great advice thanks!

Never feel safe using the front brake first on a DH, convinced myself it will send me over the handle bars  (any tips on this?)

Any particular grade of sandpaper to use? 

Do i also need to clean the pads themselves?

Finally  Is there a way to adjust the pads on my brakes so they dont rub, via an allen key, or the method i copied and pasted?


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## skatetokil (Apr 27, 2004)

As for the front brake thing, if you drag your brake all the way down, yes, you will go over the bars. You need to plan your braking and do it in short hard bursts. To do this you need to get your weight as far back on the bike as you can to hold your back wheel down. Practics doing panic stops in a parking lot with your front brake. You should be able to apply full pressure and stop dead without doing an endo if your butt is far enough behind the saddle.


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## MTB-AHOLIC (Oct 8, 2005)

capoz77 said:


> some great advice thanks!
> 
> Never feel safe using the front brake first on a DH, convinced myself it will send me over the handle bars  (any tips on this?)
> 
> ...


You want to use both your brakes in a smooth even fasion. Don't lay all the pressure on your rear brake. make sure not to suddenly jam on your rear brake and have a death grip on it.

use fine sand paper. don't grind and tear up your pads with any heavy duty sand paper. heres another tip, use rubbing alchol on your roders and pads.(they might be contaminated with some other cleaning substance.)


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## Ace1 (Jun 14, 2004)

Brakes usually squeal if the pad compound is too hard.

Instead of creating friction and wearing down as they should they create vibrations that cause the squealing. 

As has been said, if your pads or disc are contaminated then this will have the same effect and cause vibrations.

As for not using the front brake first... I've heard from a few people who do this (even on their motorbikes!) and I can't understand how they ever stop! I use my front brake way more than the rear and as long as you don't just grab it all at once and you don't jerk forward at the same time as sqeezing then you won't go over the bars.

Try just going down a road really quickly then practicing using just your front brake to stop as quickly as possible...


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## avalanche165 (Aug 7, 2006)

go with 800grit sandpaper, and i always wetsand. just get a bowl of warm soapy water, dish detergent works good, get the bike on a workstand, spin the wheels and sand the rotor. clean it with budweiser and then test it out. repeat if necessary.


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## Raptordude (Mar 30, 2004)

I think that if you are REALLY heavy on the brakes for a constant amount of time, your brakes will begin to squeal regardless. A downhill near my hometown offers harsh braking conditions during the entire DH, so at the end of the ride, my rotors are like...black...

Like others have said, clean up the rotors. Sand paper 'em, get the black grit off with rubbing alcahol. Let them dry for a long time (even though alcahol will evaporate instantly really....) but I'm always paranoid.....I let em dry overnight, tear it up the next day.


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## fred.r (Sep 8, 2005)

To get the pads to stop rubbing take your wheel off, then pads, and push the pistons back into the caliper with a small insterment (I've used alens to flat head screwdirvers) Just becareful you don't break the little metal piece in the center that sticks out a bit (sorry can't think of what it's called)


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## X-Vert (Jan 22, 2004)

clean concrete works in a pinch...


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## capoz77 (Sep 14, 2006)

I'm off on Friday if anyone see's a mountain biker doing break neck speeds in the supermarket carpark and slamming the front brake on its me! 

Ok so ive got some fine grit sand paper already, i'm going to use rubbing alcohol first - then lightly sand the discs and also give the pads a quick rub?

I hope the screeching isnt caused by metal on metal! Surely I couldnt have worn out the pads on one harsh downhill 

I'm liking the idea of 8" discs, as mentioned earlier to dissapate the heat better and provide better stopping.










"V8 Rotor

The Hayes V8 Rotor is our most powerful rotor option. V cut design has more power and increased pad contact area.Pefect for Downhill and Freeride.

Weight: 204g."

I like the look of the above, would this mean i'd also need a new mount? or can they be adjusted to accomadate a 8"?

Thanks


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## MPauB1386 (Jun 16, 2005)

Im looking at 8inch rotors as well and in my case I just have to buy a $15 adapter.


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## capoz77 (Sep 14, 2006)

MPauB1386 said:


> Im looking at 8inch rotors as well and in my case I just have to buy a $15 adapter.


hopefully it will be that easy!


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