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Front Disc Rotor Constantly Warps (steep descents)

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Front Disc Rotor Constantly Warps (steep descents)

Old 06-24-16, 12:35 PM
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SBTurtle
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Front Disc Rotor Constantly Warps (steep descents)

I upgraded my bicycle with Shimano SLX M675 disc brakes with metal pads and Shimano XT 160mm Ice-Tech Disc Brake Rotors.

The problem I'm encountering is the front disk rotor constantly warps. I carry a heavy load (commuting) and I go down steep hills. I try to use only the rear disc brakes but I need to use the the front (even with sporadic use) to make a good complete stop. The front warps so often I carry an adjustable wrench to constantly true it after a few steep descents.

Is there an alternative rotor that I can get for the front disc (compatible with metal pads and SLX) that will resist the heavier descents?

Thank you.
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Old 06-24-16, 12:39 PM
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go to 210 rotors? thicker ones like Galfer makes ?
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Old 06-24-16, 12:41 PM
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ya sounds like you just need a heavier/bigger rotor
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Old 06-24-16, 12:46 PM
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I may be off as im a newbie to cycling but do have a fair amount knowledge from reading. It is my understanding that steep descents are a common problem for brake systems and tires because of improper braking,

Steep descents require hard short braking to keep thing from being hot for a longer period of time which could cause warping. So instead of riding the brake even lightly its better to brake hard when needed and then release to let things cool down.

Now from a metal working background if youve heated the rotor up enough to warp it, you are more likely to warp it again with less heat next time.

Now I could be completely wrong but im interested to learn as well.
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Old 06-24-16, 12:55 PM
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Thank you for the replies. Can you provide a couple of links to what models / brands you suggest? I'll show my LBS.

Thanks again!
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Old 06-24-16, 12:57 PM
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Are you giving it time to cool after the descent?

I notice my rotors tend to scrap/ping for up to 30 seconds or seconds after a steep descent but once they cool they're back to normal.

ETA: I keep riding and the rotors cool as I ride along.
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Old 06-24-16, 01:07 PM
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Yep, even time to cool. The challenge is that I have multiple descents and the rotor just gets worse by the time I am at the bottom of the hill. I've tried modulating, sudden braking, and combinations thereof but it still warps. It's really frustrating. There must be a better rotor that I can get for the front?
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Old 06-24-16, 01:30 PM
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Originally Posted by Josephcsylvia View Post

Steep descents require hard short braking to keep thing from being hot for a longer period of time which could cause warping. So instead of riding the brake even lightly its better to brake hard when needed and then release to let things cool down.

Now from a metal working background if youve heated the rotor up enough to warp it, you are more likely to warp it again with less heat next time.

Now I could be completely wrong but im interested to learn as well.
That's good advice! I will focus on your suggested method - brake real hard at the last point with the front brake.
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Old 06-24-16, 01:35 PM
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Originally Posted by SBTurtle View Post
That's good advice! I will focus on your suggested method - brake real hard at the last point with the front brake.
Well not just the front brake lol.
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Old 06-24-16, 02:16 PM
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Originally Posted by Josephcsylvia View Post
Well not just the front brake lol.
Actually, if your interest is in controlling speed, there's nothing wrong with alternating between front & rear. It's a good way to control speed while giving the rotors a chance to cool. You wouldn't want to do that for shortest stopping distance.

To the OP: you should try 180mm rotors, the extra size provides a significant boost to the braking performance.
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Old 06-24-16, 02:20 PM
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Originally Posted by gsa103 View Post
To the OP: you should try 180mm rotors, the extra size provides a significant boost to the braking performance.
Should I convert to 180 for both or is the front sufficient? I don't have problems in the back.

Also, what is the process of converting 160 to 180? Is it simply a matter of adjustment or does it require additional parts?

Thanks!
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Old 06-24-16, 02:56 PM
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Originally Posted by SBTurtle View Post
Should I convert to 180 for both or is the front sufficient? I don't have problems in the back.

Also, what is the process of converting 160 to 180? Is it simply a matter of adjustment or does it require additional parts?

Thanks!
Typically just the front. You'll need a new rotor and a 160mm to 180mm adapter piece (~$15) to set the caliper for 180mm.
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Old 06-24-16, 03:11 PM
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Originally Posted by gsa103 View Post
Typically just the front. You'll need a new rotor and a 160mm to 180mm adapter piece (~$15) to set the caliper for 180mm.
Awesome! Can you recommend a good brand / model (compatible with my setup or should I get the same but the 180 version?
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Old 06-24-16, 03:30 PM
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same adaptor is used with 2 different disc sizes on front or rear . But they usually mark them.
140/160; 160/180; 180/210
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Old 06-24-16, 04:24 PM
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Originally Posted by SBTurtle View Post
Awesome! Can you recommend a good brand / model (compatible with my setup or should I get the same but the 180 version?
It depends if your bike has IS or post-mount brakes. Just get a Shimano adapter.
https://www.bikeman.com/bicycle-repa...4mm-post-mount

IS mount (side bolts on fork): Shimano 180mm Disc Brake Adaptors > Components > Brakes > Brake Adapters | Jenson USA
Post mount: Shimano F180P/P2 Disc Brake Adaptor > Components > Brakes > Brake Adapters | Jenson USA

Here's a more detailed article from Art's Cyclery: https://blog.artscyclery.com/keeping-...rake-adapters/

Last edited by gsa103; 06-24-16 at 04:27 PM.
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Old 06-24-16, 04:49 PM
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Originally Posted by gsa103 View Post
Thank you. Do you have a suggestion for the model/brand of a 180 rotor compatible with my current setup (SLX M675 with Ice-Tech metal pads with fins)? I'll have my LBS do the conversion.
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Old 06-24-16, 07:53 PM
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Make sure your fork is speced to handle a 180 rotor before you slap one on there. A larger rotor equals more fork snapping leverage. Rotors are rotors and don't care what brakes you are running. I'd probably just get a 180mm Ice tech rotor just to keep thing matching and looking pretty.
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Old 06-24-16, 08:15 PM
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I like the Avid HSX (Heat Shedding) rotors. They have the stiff cast center that makes the rotor stiffer overall. Very quiet as well...
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Old 06-24-16, 10:26 PM
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This is the fork: https://www.bikeman.com/KON-P226D.html

Any idea how I can tell if it can handle a 180mm rotor?
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Old 06-25-16, 12:04 AM
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I didn't have any luck with google so I'd send off an email
KONA BIKES | | CONTACT US

I thought you were talking about a spindly little carbon road bike fork. A steel 26er fork wouldn't concern me too much.
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Old 06-25-16, 09:16 AM
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That fork should be fine with 180mm rotors. You can contact the manufacturer, but its generally only a concern for lighter carbon forks found on road bikes or fast commuter bikes.
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Old 06-25-16, 02:54 PM
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Picture of front:

IMG_2733.jpg

Picture of rear brakes:

IMG_2734.jpg

Near the rear brake is a black kickstand. You'll see that the rotor is very close to the frame. I'm not sure a 180 mm will fit. Will it? Is it better to keep the rear at 160mm?

I ordered the following items, based on lowest price, and membership credits that I have at Performance Bike:

Shimno MA-F-180 P/S:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Shimano XT 180mm Ice-Tech Disc Brake Rotor:

Shimano XT 180mm Ice-Tech Disc Brake Rotor

I hope I can do the install myself. Any tips, advice, or instructions are welcome.

Last edited by SBTurtle; 06-25-16 at 03:01 PM.
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Old 06-26-16, 11:04 AM
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Just keep the rear at 160mm, most of your braking is from the front. The hardest part is centering the caliper. Mount the adapter, bolt the caliper on, leaving the bolts a little loose. Then squeeze the brakes and snug the caliper mounting bolts down. Inserting a business card on both sides of the rotor can help center things.

Lastly, wear a pair of disposable gloves during assembly, you'll keep you hands clean and keep finger oils/grease off the brake rotors.
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Old 06-30-16, 09:05 AM
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Ordered the following:

Shimano MA-F Disc Brake Mounting Bracket (Black, 180-mm Post/IS Front)
Shimano XT 180mm Ice-Tech Disc Brake Rotor
Shimano XT M785 Front Quick Release Skewer: Black

The reason for the new skewer is to make sure the front wheel stays on better due to the increased braking performance. It's supposedly better designed, though a little heavier, than what typically comes with a stock bicycle purchase.

Will update when installed.

Last edited by SBTurtle; 06-30-16 at 09:08 AM.
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Old 07-15-16, 11:22 AM
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Update:

Big difference in braking power! Also, the 180 front rotor doesn't warp nearly as bad as the 160 did. It can still slightly warp but no rub. I've also followed the advice on switching back and forth between front and rear braking when going down a hill. That helped a lot.

Thank you for all the help!
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