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Old 10-04-05, 06:58 AM   #1
btadlock
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learned something new today, as I was riding a downhill section, approaching a switchback, I went to brake, and horrible noise and braking was almost non-exisitant, missed the switchback and went off the trail before I could bring it to a stop, with a little flintstone asisit.
Looked at my rear rotor and it was completely destoryed, seperated at the cooling holes into two pieces, bent all up and jammed into my spokes.
I guess the 1900+ miles had worn the rotor so thin, that when I applied the brakes, hard, that the rotor was stopped cold and was thin enought to crumple under the load.
with all the various discussions around disk brakes, I had no heard of this, but it seems logical.
To make matters worse, I had t remove the rear disk assembly so that the rear wheel would turn, and I hung it on my camelback, stapped down thu the part of the rotor that was wedged into the brake. The rotor was really sharp, ( I sliced both index fingers trying to get the thing off my bike), that with the bouncing on the ride down, it cut the strap and is lost forever.
So, now I need a new six inch rotor and rear disk brake assembly.
BTW, Hayes Mech on the bike since new in 03, with over 1900, ( closing in on 2k), miles on the bike.
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Old 10-04-05, 07:55 AM   #2
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Is this a DH bike? I have almost 15,000 km (9k mi) on my rear hayes 6" disc on my freeride bike (mostly trail riding), and although it feels a little thinner in the middle of the brake track, I still have a ways to go before I wear through it. Wearing through a rotor is not unheard of though, especially on DH rigs that basically brake all the time.

Pad material is probably a factor. I use soft pads in the back caliper, and use the sintered pads for the front only. I did replace the front rotor a few years ago, but it wasn't worn too thin at that point.

Either way it's certainly an improvement over the V-brakes that eventually wore through the rim sidewalls. That sucked.
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Old 10-04-05, 09:37 AM   #3
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Originally Posted by ghettocruiser
Is this a DH bike? I have almost 15,000 km (9k mi) on my rear hayes 6" disc on my freeride bike (mostly trail riding), and although it feels a little thinner in the middle of the brake track, I still have a ways to go before I wear through it. Wearing through a rotor is not unheard of though, especially on DH rigs that basically brake all the time.

Pad material is probably a factor. I use soft pads in the back caliper, and use the sintered pads for the front only. I did replace the front rotor a few years ago, but it wasn't worn too thin at that point.

Either way it's certainly an improvement over the V-brakes that eventually wore through the rim sidewalls. That sucked.
Not a DH bike, just a XC hardtail, doubt my hayes are the same model as yours, (the iguana only cost me $582.00 in '03). I was running Aztec pads, but the last two sets were Hayes. I have been going thru 3-4 set of pads on the rear each year, the front holds up for much longer.
I am bit on the heavy side, now riding at 245lbs, down from 265lbs when I got the bike, and weight is a braking factor. Sucks that I lost the whole rear assembly, but it was petty well trashed, probably not re-usable.
in regard to V-brakes, I have blown tires, (twice), from overheating the rims. I think that my riding and my weight, (4 years ago, up to 287lbs), and my riding style and choice of trails, is hard on the component levels that I currently have. I broke the arch on my first Manitou, was breaking spokes every 3rd ride on the original. I gotta spend more on the next bike.
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Old 10-04-05, 11:46 AM   #4
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Just got back from my LBS, ordered a new rotor and brake assembly, should be back on the trails by end of the week.
The owner, 18 year experience as a wrench and now owner, said he had never seen anything like that, bent rotors yes, but never one that was sheared into two seperate rings at the cooling holes.
Well, at least it was unique.
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Old 10-04-05, 01:13 PM   #5
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shimano claims that their disks can go untill they are .5mm thickness before they need to be replaced.

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Old 10-04-05, 01:39 PM   #6
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[QUOTE=harris]shimano claims that their disks can go untill they are .5mm thickness before they need to be replaced.

wow, that is pretty thin, I have no idea how thin mine had gotten, but I know that we I touched it, it sliced both fingers like a razor, quite surprising how much it bled.

Last edited by btadlock; 10-04-05 at 01:49 PM.
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Old 10-04-05, 02:09 PM   #7
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shimano claims that their disks can go untill they are .5mm thickness before they need to be replaced.

harris
Do they make that claim in regards to the rotor, or the brake pads? I would think the pads. A rotor at 0.5mm is more of a weapon than anything else.
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Old 10-04-05, 02:22 PM   #8
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Definitly find out what the minimum thickness is for your rotor. It is not a problem you here about because most riders get ride of the bike before the rotors wear out.

I believe that the Aztec pads are a sintered compound. Meaning they have more metal in them which helps with stopping power but it eats through rotors very quickly and produces a lot more heat then a standared pad.

You should also check with Hayes if your rotors can be used with sintered pads. A lot of disc systems can not handle the sintered pads and if you do use those pads you need to check the rotors more often.


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Old 10-04-05, 05:38 PM   #9
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We wore out custom titanium rotors on our tandem in about 220km. Bad idea. Our Shimano XT 203mm ones show no signs of wear after almost a year of use.
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Old 10-05-05, 12:39 AM   #10
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Quote:
Originally Posted by harris
shimano claims that their disks can go untill they are .5mm thickness before they need to be replaced.

harris
Yeah they were talking about the pad material (not including the backing plate) not the rotor itself. A stiff breeze would fold a 0.5mm thick rotor
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Old 10-05-05, 08:27 AM   #11
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If the material on the pads is harder than the disc, the disc will eventually be destroyed by abrassion. Other explanation might be the lack of a proper heat treatment on the disc, so it didnt have the required hardness.

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Old 10-05-05, 08:30 AM   #12
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You guys are going to send me out to the garage with calipers now... trying to picture 0.5mm thick, pretty sure I have more than that left.
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Old 10-05-05, 10:00 AM   #13
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Quote:
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Yeah they were talking about the pad material (not including the backing plate) not the rotor itself. A stiff breeze would fold a 0.5mm thick rotor
uhh.... oops, thats what i meant. i thought .5mm was a little thin. it would buckle under the braking power.


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Old 10-06-05, 12:28 AM   #14
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uhh.... oops, thats what i meant. i thought .5mm was a little thin. it would buckle under the braking power.


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Considering that the nominal width of any new bicycle brake rotor sold is 2mm I'd be a touch scared to ride with only 25% of it left
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Old 10-06-05, 01:00 AM   #15
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another issue to take into account if you are running hydrolic brakes, is that the brake pad material acts like Heat Isolator for the pistons and at the end up the jorney the brake fluid that in extreme cicunstances can voil and then losse efficiency in a drastic manner..

so try to keep the brake pads in order(not super thin or Glaze) to avoid this fenomenum from happening.
many manufactures of brake pads for motorcycles
have "heat shields" to decrease the heat problems, also a few provide small "Fillers" (small pieces of "Noisy" metal) that makes you aware of the brake pads becoming to thin.

avangard companies like HOPE go even to the point of Ussing Titanium for their pistons on the super highend calipers and also design the calipers with the maximum amount of Expose area so they can optimize the "Heatsink" effect like in this example were all this little "Rippes" (waves whatever you want to call it) are machine to expose the most amount of material possible.


I will say to BtadLock that if you are wearing your brake pads on a 3 to 1 rate you need to relearn a little how to use the brakes and start to use the Front brake as your main brake, since the load transfer is far more efficient to the front wheel.
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Old 10-11-05, 02:40 PM   #16
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For Avid mech disc rotors, 1.55mm is the minimum thickness.

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