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Discussion Starter · #1 ·
Seems like every rear rotor of mine gets warped. They have all been 160mm. My recent rotor is warped after 4 hours of ride time. It's an Avid G2.

I am 200lbs and ride a Intense Spider 29er. The front is a 180mm and rear is a 160mm. The narliest downhill section I ride is 3 miles @ -5% grade according to Strava. Strava also shows me at 20mph down to 3mph and back up. There are a lot of tight turns where I need to slow down really quick and then speed back up. I use the front and rear as I approach the turn and then the rear only for any final adjustments.

Do you think I need a bigger rotor or better quality? Something like these?

Shimano Rt86 Shimano RT86 6 Bolt Rotor | Shimano | Brand | www.PricePoint.com

Hope floating rotor Hope Floating Disc Brake Rotor | Hope | Brand | www.PricePoint.com
 

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I've used stock 160s with BB7s, stock with Strokers, Alligators at 160 and now Ice Techs 180 front 160 rear. I've never warped a rotor, and I regularly descend 2000 to 3000 feet in Utah. Also, I wear the fronts way more than the rears, so I wonder if there is something more to the wear you are getting, such as using the rears more than you realize or something about how they are mounted?
 

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OP, do you true your rotors?
Define "warped".
Slight wobble?
Most side to side can be trued.
What can be difficult to fix is a bent rotor due to rock strike, impact etc.
When you mount a new rotor to your hub does it appear true?
Sometimes a fresh rotor can go out of true early in its service life, but truing it back up usually provides a permanent fix.
 

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You need to go better, although bigger will help. I used 203mm rotors, RT98 front and RT86 rear for about a year, never an issue handling 350-400 Lbs. I haven't done any super long downhill grades, but one of my favorite roads has a 1500m 5% grade, and I typically brake hard (10-15s) at the bottom to stop at the creek, and have not had any issues. A quick adjustment during initial set-up was the only time I've had to use the truing tool.

I'm on Formula's 2-piece rotor now in 180mm F/R and no troubles with them. The braking surface is thick and the aluminum body is stiff and carries off heat well, just like the two Shimano rotors. I think at 200Lbs you will be well served by a 203/180 setup just for the extra braking power for the fast stops. A 180/160 setup with those rotors would end the warping issue, but going larger lets you lay down more anchor with less effort. If you've ever felt your braking control was beginning to suffer because of finger fatigue, go up a size.

If you go for the shimano rotors, make sure you have decently long brake pads. The pads in my Avid Elixr 1's chattered a bit on the front because of the long slots in the Shimano braking surfaces.
 

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Another thing to consider is this; there is a certain technique to braking properly.
 

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I weigh more than you, and run a 180 front and 160 rear - Ashima Airotors, both. They weigh less than 100g each. Why is that important to this conversation you ask? Because mass is what allows rotors to dissipate heat. If I can drop off 3000 foot descents and not even blue my rotors, you should be able to use something as heavy as a G2 effectively on your rides. If you want to go bigger, go for it, but I don't think it will help as much as adjusting your braking technique. Keep in mind a larger rotor in the rear will make it grabbier, and effectively make the rear much more difficult to use on your "fine tuning" through the turn. In fact, the most effective way through a turn is not to brake in the turn at all, get your braking out of the entirely before the turn, then let off and blast out of the turn.
 

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If you're warping rear rotors on a 5% downhill grade it's a technique issue. Whether you're aware of it or not, you're dragging the rear brake too much and not using the front brake enough.
 

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Discussion Starter · #8 ·
Thanks for all the great responses. Let me change my braking technique to see if that helps. I raced sport bikes on road courses for a few years so I've got the mindset of using fronts over rear. But, I think being in the dirt with less traction makes me more cautious of using the fronts more as I approach a turn.
 

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I would also check your caliper alignment. If you are heating up the pads/rotor and then lock up the wheel, this will stop heat dissipation and magnify the heat in one area for a longer time. That can cause warping as well. Setup and technique as others suggested. 5% downgrade should not require a larger or more expensive rotor.

This coming from someone who does drag his brakes more than i care to admit. No warps here.
 

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Discussion Starter · #11 ·
Update: Rode today and really focused on using front more. I forgot my gloves at home which turned out to be a blessing in disguise. Without the gloves I could "feel" the brakes a lot better. I was able to control the front brake and didnt feel like I was going over the bars. Got home and rear is still true. Thanks again for the help folks.

cent frum my fone so don't cumplane about spelling or grammer
 

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Good to hear it worked! It does take some getting used to at first since a front wheel lockup on dirt is not a fun thing to have happen, but you do get a feel for it after some practice. After enough rides you'll know how hard you can use the front brake without locking up the wheel, sliding out, or going over the bars.
 

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I find it easier for me to control the bike on a twisty downhill when using only the rear brake (braking while steering). Am I putting my brake rotors in danger of getting warped?
 

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Discussion Starter · #14 ·
I find it easier for me to control the bike on a twisty downhill when using only the rear brake (braking while steering). Am I putting my brake rotors in danger of getting warped?
Depends on how hot you are getting them. Try and get into the habit of using fronts as you approach the turn. You will get a lot better braking from the front anyway.

cent frum my fone so don't cumplane about spelling or grammer
 

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I find it easier for me to control the bike on a twisty downhill when using only the rear brake (braking while steering). Am I putting my brake rotors in danger of getting warped?
See car bone's post above.

You are likely to skid more with the rear bias in your technique. I see it on my my local trails very often--skid marks at the front of nearly every turn because someone is using only or mostly their rear brakes as they steer with the front wheel (and maybe their skidding rear), thinking they are using a controlling technique. Creates erosion, brake check holes and bumps, ruts, generally annoying trail features.

Use both, please. Don't be a skidiot.
 

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So if you do find your rotors warped, what is the best method to tru them back up?
Gut instinct tells me to loosen the bolts and torque them, check, then apply additional torque as needed ?
 

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See car bone's post above.

You are likely to skid more with the rear bias in your technique. I see it on my my local trails very often--skid marks at the front of nearly every turn because someone is using only or mostly their rear brakes as they steer with the front wheel (and maybe their skidding rear), thinking they are using a controlling technique. Creates erosion, brake check holes and bumps, ruts, generally annoying trail features.

Use both, please. Don't be a skidiot.
That's what I used to do. But it causes me to lose control of the bike because both wheels would skid. In my experience so far, using only the rear brake to slow down tends to prevent skidding.
 

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beginner, that may work only if your speed is fairly slow. At higher speeds, rear braking only is nearly impossible without some skidding, at least at the speeds I tend to travel, and I'm not über fast.

If you are losing control using both, your technique is faulty and needs work. More modulation is needed which means more slowing without lockup or trading braking traction for cornering traction. Off the saddle to move the bike under you so your weight is flexible enough to move front to rear, rear to front, and side to side as needed. There are some decent braking technique vids on YouTube. Might wanna check them out.
 

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beginner, that may work only if your speed is fairly slow. At higher speeds, rear braking only is nearly impossible without some skidding, at least at the speeds I tend to travel, and I'm not über fast.

If you are losing control using both, your technique is faulty and needs work. More modulation is needed which means more slowing without lockup or trading braking traction for cornering traction. Off the saddle to move the bike under you so your weight is flexible enough to move front to rear, rear to front, and side to side as needed. There are some decent braking technique vids on YouTube. Might wanna check them out.
Yep!
 
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