Road Disc Brakes- Rotor Choice

[pdlpsher1]

Are you sure your fork accepts only 160-180mm rotors? When I switched the front rotor from 160mm to 140mm - I used an adapted between the caliper and the body of the fork.

Yes. I have the Specialized Diverge Comp. The adaptor says 140mm or 160mm, but the 140mm is really for 160mm and 160mm is for 180mm. I watched a YouTube video of another Diverge owner explaining the confusion. The fork is drilled for 160mm or 180mm only. The adaptor is offset by 20mm so it can work either with 140/160 or 160/180. Shimano won't bother re-marking the same adaptor just to avoid confusion. I knew about this before I bought the XTR rotors. I didn't even bother trying it as I believe the YouTube video content 100%. If anyone knows of a special adaptor to mount a 140mm rotor on holes drilled for 160/180 please let me know. Thanks.

[hartmannce]

Are you sure your fork accepts only 160-180mm rotors? When I switched the front rotor from 160mm to 140mm - I used an adapted between the caliper and the body of the fork.

Yes. I have the Specialized Diverge Comp. The adaptor says 140mm or 160mm, but the 140mm is really for 160mm and 160mm is for 180mm. I watched a YouTube video of another Diverge owner explaining the confusion. The fork is drilled for 160mm or 180mm only. The adaptor is offset by 20mm so it can work either with 140/160 or 160/180. Shimano won't bother re-marking the same adaptor just to avoid confusion. I knew about this before I bought the XTR rotors. I didn't even bother trying it as I believe the YouTube video content 100%. If anyone knows of a special adaptor to mount a 140mm rotor on holes drilled for 160/180 please let me know. Thanks.

That is an unfortunate reality of cycling manufacturing. My Merida had stock 160mm rotors, and the calipers were installed onto Merida's custom heatsinks/adapters, and I had to consult with Merida customer support whether I can install front and rear 140mm rotors.

[jonathantompson]

Hi all! Long time forum stalker, first time poster here I just finished getting through all 32 pages (quite the read) and I'm much better versed in all things rotors now!

I'm having a huge amount of trouble with my 160mm rear dura ace SM-RT900 rotor warping on long descents (I'm 6'6" and a lean 260lbs), so I really need to find a replacement. FWIW: I've replaced and tuned more or less everything else except the rotor at this point, so it's definitely the rotor. I think between the thermal expansion one would expect from an Al core and the use of a 4 spoke center binding results in a lot of deformation. Seems a lot of the posters in this thread seem to agree.

The Campagnolo AFS 03 rotors (https://www.campagnolo.com/WW/en/Compon ... o_rotor_03) look awesome (solid steel and 6 pin hub)... but they're out of stock everywhere.

The XTR rotors share a number of design priciples with the dura ace rotors I'm trying to replace, so I'm not entirely sure they'd work for me.

People really seem to like Galfers rotors (and I hadn't even heard of them!) but those are also out of stock (the road version).

Although not many have mentioned it here, I do hear good things about swisstop's catalyst rotors (https://www.swissstop.com/catalyst/), but these are also out of stock.

What other options am I missing? Or should I just wait until things come back in stock?.... although who knows when that might be

[jmechy]

Give the XTRs a try. I've found that the warp significanlty less than the ultegra rotors I had on before. I used to have pinging rotors the entire time I descended my go-to climb with ultegra rotors, now with XTRs I have no rubbing at all.

[Schadenfreude]

Give the XTRs a try. I've found that the warp significanlty less than the ultegra rotors I had on before. I used to have pinging rotors the entire time I descended my go-to climb with ultegra rotors, now with XTRs I have no rubbing at all.

160mm XTRs also seem really hard to come by at the moment.

[jonathantompson]

Yeah, I can't seem to find any. Unless I want to spend $150 per rotor on ebay

Oh well, I guess I'll just have to wait.

[jonathantompson]

please delete

[andreas]

When people talk about the XTR rotors, is it the old SM-RT99 with 5 arms (160mm version) and a wave-pattern in the fins, or the newer RT-MT900 with 4 arms (160 mm version) and a flatter pattern in the fins?

[Hexsense]

Default is RT-MT900.
We default to current model, not the obsoleted models since 2018, unless it is specifically specified.

[ooo]

There are some rotors on ali:
$82 €70 link RT-MT900 160 mm XTR
$37 €32 link RT-MT800 160 mm XT

[jonathantompson]

Well that was lucky....

I vaguely remembered seeing an old rotor at the bottom of my messy "box of old biking stuff"... Turns out it was an older SM-RT99 rotor! It was horribly untrue, which is not overly surprising given that I had shoved it in the bottom of a box of heavy biking parts... But I trued it up and took it out for a decent climb today (~900m) and the descent was So. Much. Better. Night and day. No pinging. No rubbing. Perfect. I did notice some minor brake fade about half way down, but if I'm being honest I wasn't overly careful about cleaning it before putting it on the bike, or doing a proper bedding run. I hadn't even cleaned the pads

Conclusion for me: Dura Ace SM-RT900 just don't work for my body weight on these north california hills. They're probably great at dissipating a lot of heat but my guess is they just don't have enough heat capacity to avoid warping. Note that I did try swapping out the dura ace rotor for another dura ace (which in retrospect was a terrible purchase), so it wasn't just a faulty rotor. I also completely cleaned out and took apart the rear caliper and I tried both swissstop disc45 exotherm2 and Shimano pads. It was definitely the rotor (the last thing I suspected).

I'm guessing folks happy with the ultegra and dura ace rotors are just significnatly lighter than me (which is not hard...) or live in a flat area.

[snaxez]

Give the XTRs a try. I've found that the warp significanlty less than the ultegra rotors I had on before. I used to have pinging rotors the entire time I descended my go-to climb with ultegra rotors, now with XTRs I have no rubbing at all.

160mm XTRs also seem really hard to come by at the moment.

You can get 160 XT ones from bike24 in stock https://www.bike24.com/p2317187.html
I know the grey fins look ugly, but there was another thread where someone painted them red with success. So I suppose you could paint them black and they would be 99% XTR

[jadedaid]

An update on the Galfter rotors, after having put ca. 1500km on them in the hills around Girona and Malaga. I'm not a fan and will be going back to SRAM Centerliner X rotors which I've never had a single issue with, other than them being really hard to get these days.

• Warping. They keep warping. I've had them straightened and a few long descents later they're warped again.
• Fading. They fade. Never experienced this on a road bike before. I changed pads and bled the brakes twice to make sure it wasn't fluid or pad related, and they still fade.

[spdntrxi]

^ bummer on the galfers... I just got some ( not installed ) maybe I'll just pop them on the TT bike where the brakes are not used as much.

How many KG's if you dont mind me asking ?

[BZE]

An update on the Galfter rotors (...)

Was this with Galfer pads?