Road discs warping

Brand new 105 brakes, some very steep hills around here, and a couple of times (where letting off the brakes to cool them isn’t possible) the front disc has just crinkled up. Unexpectedly, a squirt of water from the bidon straightens it out perfectly but it’s not ideal.
We’re talking 20-25% gradients, easy enough to find another way but this never happened on my previous (c2017) 105-shod bike so I guess these discs are thinner. They’re the SM-54 160 centrelocks – Worth changing the discs to another brand?

Not on a road bike, but I melted standard SRAM rotors in the alps descending down the road from Avoriaz to Morzine on my DH bike. The rotors looked like quavers. All distorted and wavy. Upgraded to floating rotors and never had the problem again

Aren’t they the ones with the massive steel surface/spider plus tiny carrier?

If they are, either get some better cooled discs (i have some 160mm ultegra level ones with cooling fins that i’ve not managed to get to rub) or bigger ones the same (plus the adaptors).

And TBH, they all do that, to one degree or another, eventually. Just depends on how well centred they are and what the clearances are. (And how hot they get.)

I live at the top of the Rhiwr and I can turn discs blue, but not had them warp, I’d expect better.

OK, I’ll try Ultegra. They’re 30€ more expensive, but I guess I only need the front one. It’s just weird that my old bike never did this, bought new with 105 kit but just threw the cheapest replacement on when the rotors wore out. Did brakes get more powerful? Or did I get fat? Lol
https://cdn.deporvillage.com/cdn-cgi/image/h=1800,w=1800,dpr=2,f=auto,q=75,fit=contain,background=white/product/irtcl800ssi-c_587.jpg

Size of rotors? Are they 140 or 160. 160 might help.

I have 160 discs on the Vagabond and the Merlin before that. I can get them discoloured and pads glazed before, but have never warped them, and we have a few steeper / bigger descents in Scotland. And I am a portly lad with panniers…

Bigger front disc from different brand?, finned pads? Brake less ——wink emoji——

160. I have confidence in them on long fast descents. Woeful on the steep stuff.

I live at the top of the Rhiwr and I can turn discs blue, but not had them warp, I’d expect better.

Heh mine have gone through blue to light brown! Chwarae teg on having to get up that on the way home!

Well Ultegra rotor ordered, see if that cures it, I can reuse the old ones on my commuter . The pads are finned on 105 already but the rotors appear to be junk. Had more confidence on these hills when I was riding rim brakes with cork pads and explodey carbon rims.

Avoid Shimano Warp-Tech rotors altogether would be my advice, I’ve had more success with cheaper 1-piece Shimano rotors, or SRAM spider-ed ones.

I’ve had it a bit with Hope rotors – the ally spider deforms and goes a bit dished. Not helped by the breaking surfaces on mine being right close to the wear limit and I really need to replace them before winter.

The Shimano Ultegra ice tech ones on my gravelbike are woeful for going out of true and rubbing. I think its because they’re a fancy steel/ally/steel sandwich, so there’s relatively little structural integrity to them, especially once the steel starts to wear a bit. I haven’t actually properly tacoed one, mind…

160mm / 80kg / frequent steep descents in Peaks, Dales, Lakes like Winnats, Honnister, Kidstones, Park Rash etc.

Ultegra work well for me. Hopefully it fixes your issues too.

Those rotors are only for resin pads – is that what you have fitted?

My SRAM centreline X rotors have gone bronze on the thin edge from one long descent down Swinhope a couple of weekends ago – and I was trying not to drag them . They’re always going out of true too. It’s a constant battle. I don’t know why you can’t get decent brakes on a road bike. They’re either squealing or going odd colours or both…

Pah, rim brakes for the win.

As Daffy says, those are for resin pads only so if you’re using anything else, I’d expect trouble.

The resin only shimanos are just stamped steel and in your case, bolted to a small alloy carrier.

Higher spec Icetech are a full alloy core with a stainless braking surface bonded to the core.

Cheap stamped steel will warp. ‘pensive alloy/ stainless ones won’t warp anywhere near as easily so your Ultegra should fix your problem.

Do Magura still do the e-bike specific ones?

I bought some to try and fix the squealing on my gravel bike. It didn’t work but I stuck them on the MTB and I don’t think they’ve ever warped or rubbed despite some severely under-braked descending!

What actually makes those rotors resin pad only? The shape of the cutouts? Lower quality steel that pringles?

Yeah, basically lower quality steel that pringles. Metal pads are a lot more aggressive than the resin.

Just like car brakes, if you’re doing heavy stops to stationary and then sitting/track standing with your brakes on, that’s also going to case warping.  I’ve now done years of road and gravel on first 160mm Hope Floating and in the last 4-5years 160mm Shimano RT99s without any issues at all.

I recently bought some TRP 25 rotors for the commuter for a spare set of wheels as I couldn’t justify the price for Dura Ace CL900 and XTR M900 in 160mm are 4 spoke, which for some reason I can’t stand.

The TRPs seem nice, well made and look good, but initial bite out of the box seems lower than the Shimanos they replaced, but that could be due to them being slightly wider and thus less servowave coming into play before initial bite.  Time will tell, but they’re more solid in feel, so may be what you’re looking for.

(where letting off the brakes to cool them isn’t possible)

Try braking harder with one brake, then the other rather than dragging both.

Don’t quench them with water, that’s more likely to cause problems than solve them.

How can the brake pad material be the issue? If you brake, the heat is dumped onto the rotor, it’s the same amount of energy regardless of pad type. Ok a small amount goes into the pad itself (and then calliper etc), but that’s far smaller area and conducts more poorly than plain metal regardless of type. Hard to imagine it can add up to more than few percent of the total. Pads having more bite just means you don’t need to squeeze the lever so hard.

not even 105 rotors TBF. resin only deore M6000. 105 are SM-RT70. I put centre lock XT rotors on mine. only paid £20 for each of them.

Pah, rim brakes for the win.

Yeah. I’m tempted to think that, after decades of fairly hassle-free braking lol
Without turning this into rim vs disc, it does seem the big advantage of discs is to brake as fast as the disc-braked rider in front. And I largely ride alone!

Anyway, Ultegra rotor on, 50€ poorer, and we’ll see if we can warp it.

Nah, the benefit of discs is that the consumable braking surface becomes a cheap less expensive, easily replaceable part, and you can make rims out of carbon and not worry about them melting.

Pads having more bite just means you don’t need to squeeze the lever so hard.

Ah, but that’s not what happens though. You don’t fit more aggressive pads and then squeeze the lever less for the same amount of braking, you still pull the lever as hard and stop quicker as a result. Being able to pull the lever harder and get more friction out of the brake leads to more heat which is where the discs start to warp.