Why do brake discs/rotors warp

In addition to checking the rotor mounting surface on the wheel, take a gander at the caliper mounts/ caliper. Many were shimmed to center the caliper on the rotor and many wind up with one or both shims missing. An out of parallel caliper will try to bend the rotor when the brakes are applied hard. One indication is tapered pad wear.
 
wdietz186 said:
In addition to checking the rotor mounting surface on the wheel, take a gander at the caliper mounts/ caliper. Many were shimmed to center the caliper on the rotor and many wind up with one or both shims missing. An out of parallel caliper will try to bend the rotor when the brakes are applied hard. One indication is tapered pad wear.
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Brake pads naturally wear faster at their leading edges. Many 4-pot calipers use different sized pistons at the leading and trailing ends to help counter this.

cheers,

bazzee
 
To get the drilling pattern right you just need to flip the disc!

I remember back in the 80's there was fierce debate about cast iron vs stainless discs. CI came out top because of wet weather performance.
That was until sintered-metal pads came along and that changed the game completely.
Advantsges of Stainless:
1). Coupled with sintered-metal pads has a higher coefficient of friction.
2,).Is more resistant to warping.
3). Highly resistant to wear.
4).Tougher and less likely to crack than CI.

I bought some stainless discs from Stein Dinse, they look almost identical to the original CI discs with same drilling pattern and fit beautifully. I believe they are also Ducati Bevel fitment!!!!!!
https://www.stein-dinse.biz/product_info.php?products_id=2024
080277340.2.jpg

The stainless discs above are thinner than the cast iron original, which is one presumes a product of better warping resistance. They start off at 5.75mm and minimum thickness is 5mm. CI starts off at 6.35mm  and minimum thickness of 5.7cm.

I do like Cams warp theory, makes a lot of sense. Although worn discs are more susceptible to warping.
Anyway! My front discs never get really hot. Maybe I should do more 'banzai' stops?
 
Don't know what they use on bicycle disc rotors, but I've seen calipers that only have a single operating piston where the inside pad (movable via adjustment screw only) ends up very worn and the pad operated by the cable has to bend the rotor across to make contact with the static pad. it's incredible how far they bend - and on mountain bikes on long steep descents they get VERY hot. Pretty amazing metallurgy right there.

Of course, what's supposed to happen is that the owner brings the bike in for a one minute brake pad adjustment once every month or so - we wouldn't even charge for it. The reality? Years ... then the pads are worn at such an angle they can't be adjusted without pad drag - and even then, the rotor still has to bend the rotor to make contact with the tapered inner and outer pad. Shit system - opposing piston calipers are the only real answer, cable or hydro.
 
Was there a pattent on that, single piston sliding pin seems so stupid compared to twin piston brakes.Why would you not use the later.
 
Original fitment discs are 'handed' as there is a groove machined on one side (the outside).
If you flip the disc over there is no groove showing.
Should still work the same, just no groove.
I think that aftermarket discs are not handed.
 
Single piston sliding pin works on almost every car, and on my old cbr600 practice race bike they are not a problem, for sure not as good as opposing pistons but they have never given me any trouble, and the pads wear very evenly.
 
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