elcruxio

I can understand that some discs come out wobbly, for example all Avid discs I've had have needed some extensive truing as they come from the factory wobbly as crud. They've stayed true after the inital truing however. All Hayes discs I've seen have been straight as a bullet and have stayed that way, never a single need for adjustment. Hope addresses the heat issue by straightening and stress relieving the disc during heat treatment. Essentially it depends whether you buy the cheap stuff or not, but only the shoddiest discs should be able to go out of true even with intense heating and hard use.

Of course mech discs probably can wobbly up discs pretty easily if they are set up wrong. The inner pad should be so close to the disc that it's almost touching (you'll likely hear a bit of *schwing schwing* during hard cornering)

If the brakes are adjusted correctly initially (ie. the Hope way) sticky pistons won't be an issue and even if by some weird fluke you manage get said issue it takes less than a minute and a small flat head screw driver to correct (yes, a multitool should have a flathead)
That is of course if we're talking the ordinary sticky piston that happens with every hydro disc on the market? The other type I know of (Shimano hydro cold death) means the brakes are toast anyways.

I honestly cannot see a situation where proper braking technique with a properly adjusted brake system would warp a rotor. I've given my 203mm Avid front disc (as established, Avid discs are crap, but they're cheap and I'm poor and the problems of warping are greater with a huge 203mm disc) enough heat to burn lubricants inside the brake caliper and still it stayed true.

Me too, I totally hate all kinds of rub. That's why went to discs. Although now that I'm a seriously good wheel builder I don't see rim wobbles anymore but I'd still rather not think about rim brake wobble.
The only issues I've had with disc dragging have been with Shimano hydraulics during the winter and so I don't use Shimano hydraulics anymore.


It takes 5 minutes to true a disc to perfection and afterwards you need to crash it to create a wobble. I do not understand what you do to create said wobbles.

Hence various cool disc designs such as sandwiched alu/steel discs, Hope airflow discs, etc.

I don't know whether I understand it or not but I've done it. Cooked my fingers whilst checking the rim right after too. Wasn't fun.


Well, you can take the disc off.

And you'd need quite a sizeable crash with just the right sequence of events to achieve that 1mm bend as the disc is pretty protected. The amount of bending a disc requires to achieve even a 0.1mm correction is pretty huge.
And even if you do get a bend, you can bend it back.
But there is no way a well adjusted disc brake will heat warp a disc enough to make it clamp in the caliper. At least not if the disc is not clearly defective or some Asian pot metal copy disc. If you manage to regularly heat warp discs I question the correctness of your brake setup.

Canker

The only time I've ever seen a rotor get so bent you couldn't trail fix it to good enough was through my own stupidity. I had a rotor work 5 of the 6 screws loose and it tore itself off the hub when I hit the brake. Check those rotor bolts every now and again. That blue loctite isn't magical.

cyccommute 

So how much room does a hub mounted caliper have to wobble? A steel rotor, which is the most commonly used rotor, is only 2mm wide. The gap for the disc to travel through the rotor is only 3mm wide. The pads have to be set so that they are almost touching the rotor to be effect so that narrows the gap between the pads to a lot about 2.5mm.

Perhaps saying that a 1mm wobble would render a brake unusable was crazy talk. It's a lot less than 1mm.

DrIsotope

Every time I read through one of his posts, and feel the keyboard fingers start to get itchy, I have a mental sign that flashes in my head, which reads "DO NOT ENGAGE." Because you see, despite all of the bad advice he gives out, he knows what he knows, and is therefore immune to reason. Sure, some of his claims are absurd and almost beg to be countered, but you can't use empirical evidence to undo a well-entrenched preconceived notion.

It's like trying to swim up a waterfall.

Mr IGH

Other than my newer 5 year old MTB, everything me and my kids ride are are 9mm QR front and 10mm QR rear with BB7s. It's typical for clueless users to claim BB7 are defective by design when they don't know what they're doing. You're in the club....

Mr IGH

All I have are the cheapest Avid rotors, from 160mm to 205mm NONE have every needed truing out of the box and I've yet to bend a rotor in the field. 9 bikes, 8 MTB, one road, all BB7. Granted there's three Shimano dyno hubs with centerlock running 160mm, again with the cheapest rotors I could find.

When I worked in an LBS, all the disc bikes came out of the box with true rotors. The only bent discs I saw were from screwing up whilst mounting the wheel and forcing things.

The detractors here demand to be ignorant, there's millions of happy disc brake users in the world, they're ubiquitous on MTBs these days....

Mr IGH

Yup, I put him on ignore, it's pointless trying to reason. I mean who could claim what he says about disc brakes in 2016, as if there's not literally millions of satisfied users....

Jarrett2

Thanks plankton troll Top notch reading comprehension skills to boot.

elcruxio

Weirdly enough I've never had a true Avid rotor for whatever reason. I have a set of BB7 roads on the way so time will tell whether this next one will be true or not. I'll probably get Hope rotors as my next set since the manufacturing process seems to be one of the best out there to ensure a true disc even with massive overheating.

Mr IGH

Here's a video should you choose become educated rather than bleating out insults and mis-information :

edit: amended insult:

Leebo

4 sets of BB7's on different bikes, only 1 " defective" Managed to go too far off trail and jammed a sapling between the spokes of the front wheel and rotor. Maybe that would fall under operator error.

Mr IGH

I've had some bad crashes on my MTB but never managed to do that, nor have my two reckless sons. I always imagined that was possible but never saw it in person!

I like the cheap BB7 rotors 'cause they're very thick, good for shedding heat and resisting bending, if it does bend a replacement is cheap

SingleSpeeDemon

I would have liked to have discs back when alloy rims were hard anodized and didn't have a machined braking track. After a while when the anodizing wore through, the rims looked like rubbish.

That said, if I were to buy a new bike today, it would have disc brakes. However, my latest acquisition, my 3Rensho, has no brakes at all (but that's for a different forum entirely).

zze86

I concede. Still prefer rim brakes tho since, as my post showed I'm typically the last S in KISS.

BlazingPedals

If memory serves, BB7 specs say adjust to 1mm of clearance to the inside pad and 2mm to the outside one. One reason I like Spyre/Spyke is that I can adjust both sides to 2mm or more and the pads can both contact at the same degree of activation, and still have lever travel to spare. The bad thing about most mechanicals is that most only move one pad, and contacting both pads relies on bending the rotor. Do it hard enough the yes the rotor will become un-true. The deflection itself exacerbates squealing, too, in my experience.

Leebo

Yes, replacements are cheap. A too fast for conditions turn, I went for bushes/saplings as opposed to big oak.

Gweedo1

You just keep trying...good for you.

The thing is, when you run across limited thinkers on the interwebs, you have to understand, that they think because they can do something, that all situations are equal so they can't comprehend the infinite number of circumstance and situation permutations that exist. They be too simple to understand that maybe your situation and circumstances are such, that even the mighty they, could not have mastered the problem. Like maybe, oh, I don't know, there was something wrong with the bike or the attached components and not you and your skills.

Get yourself a good service manual, something from Leonard Zinn, some basic bicycle tools, watch a lot of related videos on line, keep hanging around forums like this, and ask a lot of "dumb" questions, and your skill level will go up as mercurially as your general bicycle knowledge. And trust me, for 90% of what an owner may need to do on her bike, it's bicycle mechanics 101, and you can do that.