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PostPosted: Tue Sep 19, 2017 2:41 am 
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Joined: Fri Jan 04, 2013 7:17 pm
Posts: 226
Location: UT/TX/PA, USA
FWIW...it may not be the rotor. What about your caliper? Not sure which caliper you are using, but the pistons of some calipers don't retract very well. I've been having issues with my front RS685 caliper. Bled the brake and it is now better, but not quite perfect.


MoPho wrote:
I haven't had much luck with the ice-tech rotors. For some reason I was getting an issue where the pads were pulsing and scraping over the vent cut-outs on the rotors as I got below 20mph under harder braking. Changed pads and it would go away for a little while, then come back. Same if I changed rotors and/or cleaned and sanded the pads. Tried both RT99 and RT81 140mm and 160mm. Same thing every time. Seems I am the only one with this issue as none of the other disc guys around here are experiencing it with the ice tech.
Now trying the Sram Centerline and the issue has gone away seemingly because of the shape of the venting, but not sure yet if the braking is as good with them. Already had a hard stop from 40-0 mph that overheated the rotors, may have been an anomaly.
:noidea:



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PostPosted: Tue Sep 19, 2017 3:15 am 
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Joined: Mon Jul 24, 2017 12:02 pm
Posts: 490
I don't think it's the venting...it's the shape of the rotor's outside and inside edge. If you look at the various Ice Teh rotors, they are severely notched on the outside. The RT-99 and RT-900 are also severely notched on the inside where they mate with the heatsinks. I've had this problem with the Ice Techs and have since switched to SRAM Centerline X and also tried the new Campy H11 rotors.

TBH the SRAM rotors are the best in terms of braking noise. The H11s make a "cool" noise under braking with their aggressive venting. Some rub after strong braking is kind of the norm. Once the rotor, pad, etc. cool down, the contact goes away.


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Posted: Tue Sep 19, 2017 3:15 am 


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PostPosted: Tue Sep 19, 2017 3:54 am 
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Joined: Sun Jul 10, 2011 7:48 pm
Posts: 330
Location: NorCal/SoCal
justaute wrote:
FWIW...it may not be the rotor. What about your caliper? Not sure which caliper you are using, but the pistons of some calipers don't retract very well. I've been having issues with my front RS685 caliper. Bled the brake and it is now better, but not quite perfect.


I have the RS805. I had not considered the pistons not retracting because it happens when the brakes are being applied firmly, but something to look at.






TobinHatesYou wrote:
I don't think it's the venting...it's the shape of the rotor's outside and inside edge. If you look at the various Ice Teh rotors, they are severely notched on the outside. The RT-99 and RT-900 are also severely notched on the inside where they mate with the heatsinks. I've had this problem with the Ice Techs and have since switched to SRAM Centerline X and also tried the new Campy H11 rotors.


Yes, you are correct it seems to be the outer notches causing the issue. Glad to hear someone else has had this happen. No one around here has experienced it, which you would think it would happen to all of them :noidea:


Quote:
TBH the SRAM rotors are the best in terms of braking noise. The H11s make a "cool" noise under braking with their aggressive venting. Some rub after strong braking is kind of the norm. Once the rotor, pad, etc. cool down, the contact goes away.


When I was on the 140mm ice tech there would be that rubbing after a hard brake event for a few seconds till they cooled, interestingly I did not get it with 160mm rotors. I have to do some more testing with the Centerline

The centerlines look great on the bike though :mrgreen:





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PostPosted: Tue Sep 19, 2017 4:55 am 
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Joined: Mon Jul 24, 2017 12:02 pm
Posts: 490
Let me know if you get sharp pings on your Centerlines after long hard descents. It seems to be the result of the alloy carrier and steel rotor expanding and contracting at different rates. It's the only issue I've had with the SRAM rotors and it's not performance related.


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PostPosted: Tue Sep 19, 2017 5:58 am 
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Joined: Mon Jul 24, 2017 12:02 pm
Posts: 490
TobinHatesYou wrote:
The H11s make a "cool" noise under braking with their aggressive venting.


Video/audio example on a descent today.


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PostPosted: Tue Sep 19, 2017 6:35 am 
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Joined: Sun Apr 24, 2016 11:02 am
Posts: 54
TobinHatesYou wrote:
TobinHatesYou wrote:
The H11s make a "cool" noise under braking with their aggressive venting.


Video/audio example on a descent today.

Awesome! What speeds were you doing?


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PostPosted: Tue Sep 19, 2017 6:45 am 
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Joined: Tue Apr 25, 2017 11:12 am
Posts: 194
Location: Christchurch New Zealand
TobinHatesYou wrote:
TobinHatesYou wrote:
The H11s make a "cool" noise under braking with their aggressive venting.


Video/audio example on a descent today.


Was it the brakes or was Chewbacca in the saddle :D


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PostPosted: Tue Sep 19, 2017 7:23 am 
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Joined: Mon Jul 24, 2017 12:02 pm
Posts: 490
lwk wrote:
Awesome! What speeds were you doing?


Max speed was probably around 45mph / 72.5km/h. On some other segments I touch 50mph / 80.5km/h, but the roads here aren't usually steep and straight enough to go faster than that. Also I'm fairly light, so I don't pick up speed when the air is particularly dense like it was today.


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PostPosted: Tue Sep 19, 2017 8:07 am 
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Joined: Sun Jul 10, 2011 7:48 pm
Posts: 330
Location: NorCal/SoCal
TobinHatesYou wrote:
Let me know if you get sharp pings on your Centerlines after long hard descents. It seems to be the result of the alloy carrier and steel rotor expanding and contracting at different rates. It's the only issue I've had with the SRAM rotors and it's not performance related.



I haven't had that happen yet.
Are you ceugene on the other forum?



Quote:
Video/audio example on a descent today.



NorCal?



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PostPosted: Tue Sep 19, 2017 8:27 am 
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Joined: Mon Jul 24, 2017 12:02 pm
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MoPho wrote:
I haven't had that happen yet.
Are you ceugene on the other forum?

Quote:
Video/audio example on a descent today.

NorCal?

Yes and yes.


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PostPosted: Tue Sep 19, 2017 9:35 am 
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Joined: Sun Jul 10, 2011 7:48 pm
Posts: 330
Location: NorCal/SoCal
TobinHatesYou wrote:
Yes and yes.


Well I guess you're not the 2nd person I've found that has had this issue LOL



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PostPosted: Tue Sep 19, 2017 11:50 pm 
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Joined: Tue Apr 22, 2008 4:31 am
Posts: 385
Interesting MoPho - what calipers are you using ? I'm on the 4 piston Zee, so with the bigger pad, it may be a very different result.

I have also used Avid HSX and had overheating problems on some descents that I never had with any other rotors (same pads and speeds). They got binned real quick.


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PostPosted: Wed Sep 20, 2017 2:24 am 
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Joined: Wed Sep 20, 2017 2:17 am
Posts: 1
I think SM-RT900 is the best disc rotor for road-bike.


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PostPosted: Wed Sep 20, 2017 2:56 am 
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Joined: Mon Jul 24, 2017 12:02 pm
Posts: 490
chaks wrote:
I think SM-RT900 is the best disc rotor for road-bike.


They're all about the same weight...hovering around 120g for centerlock rotors. The only major difference is the fins and the aluminum middle layer. I don't think it's a big deal, and it definitely wasn't worth dealing with the weird pulsing issues resulting from its shape.


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Posted: Wed Sep 20, 2017 2:56 am 


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PostPosted: Wed Sep 20, 2017 3:32 am 
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Joined: Sun Jul 10, 2011 7:48 pm
Posts: 330
Location: NorCal/SoCal
MichaelB wrote:
Interesting MoPho - what calipers are you using ? I'm on the 4 piston Zee, so with the bigger pad, it may be a very different result.

I have also used Avid HSX and had overheating problems on some descents that I never had with any other rotors (same pads and speeds). They got binned real quick.


I am using the RS805 and I think the smaller pads have a lot to do with the issue.
Are you using the Zee calipers on a road bike? Disc naysayers often use lack of traction as an argument but I feel like I could use even more power in the dry, 4 piston brakes would be interesting. :twisted:



- -

Did a good 5 mile technical descent today and the centerline rotors seemed to hold up well, including a panic stop when a deer ran out in front of me. :shock:


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