Tech Talks: Rotor Truing, Presented by Park Tool - Video

Aug 25, 2016
by Pinkbike Staff  
Tech Talks Presented by Park Tool


Tech Talks Presented by Park Tool is a monthly video series hosted by Park Tool's own wrench whisperer, Calvin Jones. The new series will cover the A to Zs of some of the most prevalent repair jobs, with the second episode tackling one of the most annoying - and common - mechanical issues that we see: bent disc brake rotors. There's almost nothing worse than pedaling up a hill knowing full well that one of your wheels isn't spinning freely, especially when you can actually hear the rotor scraping against the pads.

A bent rotor doesn't always have to stay bent, however, and you may be able to straighten it rather than replace it. Below, Calvin shows you the tools required and runs you through the process. Watch those fingertips!


Tech Talks - How to True a Rotor


Views: 21,140    Faves: 58    Comments: 2



Need more Calvin in your life? Episode #1 shows you how to take on tubeless tire installation and conversion in two easy to follow videos that will have you feeling like a pro.

Stay tuned for more mechanical how-to videos with Calvin returning on the last Thursday of every month to show you the easiest way to get the job done. Want to know more? Park Tool's how-to section has you and your bike covered.

www.parktool.com / @ParkToolCompany


95 Comments

  • 47 4
 Handful of comments now from people saying that they just trash a rotor and buy a new one. Strange because every time PB posts a review of anything dozens of commenters whine about the price of things. "More stuff for rich dentists endure douches!"

I don't get it.
  • 7 2
 The same people are probably walking over to their bikes now with an adjustable spanner and grin on their face from simply the idea of not having to replace it!
  • 33 9
 It's called being an unpleasable, whiny hipocrite hemorrhoid of a human being. The subject is irrelevant, the only thing that matters is finding a way to whine about something so that you can find some other miserable souls to prop you.
  • 12 3
 @WAKIdesigns: yep, humans and the internet.
  • 5 4
 @WAKIdesigns: Oh. Right. I always forget that for some reason.
  • 8 1
 not so sure about that, maybe cheaper to get a new rotor in this case... all those tools must cost an arm
  • 3 0
 @Benito-Camelas: That is certainly true. However a lot of people have many of these tools for use in other applications. The only rotor-truing specific tools is the one for bending, and the gauge on the bike stand. I use an old "coe-pattern" wrench to do what he's doing, as far as bending. You also wouldn't need the gauge, anything that gives you a visual representation of where the rotor is in space would do. Like him using the caliper and pad as a reference.

I dunno, if I tossed all the rotor's I smash on rocks I certainty couldn't afford this stash of Shimano brake pads I've been hoarding over the years.
  • 17 0
 @Benito-Camelas: an adjustable wrench is pretty much the exact same thing as a rotor truing tool
  • 5 2
 When my grips are worn out I get new ones.
Same with tires.
Might tolerate a torn seat for a while.
You can buy a new rotor for the cost of grips, so why would I want to keep riding with a rotor that won't stay straight?
Sure a minor bend can be fixed but when a rotor is bent bad enough just gun it.
Ok it's 2:30, I gotta go
  • 8 2
 @kubaner: because most spiderless rotors come slightly bent out of the box. It's life.
  • 1 0
 I had a tube with 6 patches on it to get the most use out of it, heh heh. I'm curious if anybody did more. Anybody had more patch than tube left?
  • 2 1
 @Ron-C: I used 13 patches for one tube, where 7 came from one puncturing, as the tube blew right in the beginning of a very rocky bit. It was from student times where I was saving 3$ a week. My dad threw away my trophy so sorry no pic...
  • 1 0
 @mnorris122: and chainring truing tool as well
  • 4 0
 @kubaner: I see what you're saying, and I don't totally disagree. I think it's all relative though. I find that because I'm willing to try and fix things, and get as much life out of them as possible, I'm able to save a lot of money on my mountain bikes. All of my bikes are made of scavenged parts from other bikes, both mine and my friends. My friends don't throw anything away before they ask if I want it to try and fix it.

Mountain bikes are expensive beyond measure, but I find that if you're willing to get creative with how you approach the sport you can get a lot more bang for your buck than you think.

A brake rotor is just a brake rotor, but pretty soon with that attitude, everything on a bike becomes a throw away item.
  • 3 0
 @Rucker10:
The problem with PB users is that they are always looking to contradict someone and argue a useless point. My "throw it away" comment was more for the biker who's been there before dicking with a bent rotor and finally saying f*ck it, and tossin it out.
I'm not a dentist, and I don't like wasting money. And I'm also really good at fixing something someone else gave up on. But sadly I can't fix the atmosphere here on PB.
Much like giving up on a useless argument, when a part has seen its better days I get rid of it.
  • 3 4
 @kubaner: mnah, that's the problem with most human beings on planet Earthernet. I would not stick it to Pinkbike because in my search for the end of bike internet I haven't found a single established site which wouldn't have a bunch of whiny people. Try some roadie website hahah Big Grin what is typical to Pinkbike is the huge nr of comments per article, so sht is just more visible while other sites seem to keep it within the family. It doesn't mean it isn't there.
  • 4 1
 @WAKIdesigns:
Thanks for confirming my statement.
Gonna go for a ride now so I can argue with my friends in person.
  • 2 0
 @Ron-C: I had a tube for so long I was patching patches. Don't do that anymore.
  • 2 0
 @Rucker10 I agree. I wonder what they're getting bent out of shape for. Wink
  • 3 0
 @WAKIdesigns props always given for using the word "hemorrhoid."
  • 3 1
 @xprswy: and for "moist" taketh
  • 2 0
 @WAKIdesigns: Yup, I just propped you.
  • 19 2
 i hope my hot dog never gets that close to a rotor...
  • 14 2
 Worth it for the sausage at 55 secs
  • 4 0
 I came to see the sausage get sliced. Did not leave disappointed.
  • 11 0
 I just sandwich my rotors between two blocks of wood and jump up and down like a madman
  • 8 0
 Only works if you have straight wood.
  • 19 0
 @unrooted: That's what she said.
  • 3 0
 @unrooted: I have really bendy wood and it works just fine.
  • 2 0
 Funny... I used to try and straighten rotors by putting them on a finished granite counter top and beating on them with a rubber mallet. That was about 10 years ago though...
  • 2 0
 @Neechy: Michael Scott would be proud ;D
  • 7 0
 Excellent explanation. Also I like that he takes the time to point out what to check first before you start working on the rotor. Two things I'd like to add.

1. If the wobble is because not all rotor bolts are tight (as he points out in the beginning), don't just tighten the rotor bolts. Take the rotor off, clean the mating faces and only then bolt the rotor back on.

2. Use a whiteboard marker instead of permanent marker on the rotor spokes. You don't need much to wipe these clean once you're done.
  • 8 1
 Lots of variables to look out for. I had a clipper facing issue once. Never knew there exists a facing tool like they showed. I used a file.
  • 5 0
 I've found that truing rotors is a losing battle because once they get bent they usually retain a 'memory'. You can true and true and true and get it to within 1 micrometer and then as soon as you apply a bunch of heat to it (like use your brakes) then BAM its bent again. I try to buy the highest quality rotors i can so i don't have to deal with bent rotors. i find that the shimano rotors with aluminum spiders remain true longest.
  • 2 0
 Jagwire CR1 for me. I do like the shimanos which have a spider and are not ice tech(no sandwiched aluminum braking surface), but the jagwire is like that, plus cooling fins. They're strong, light enough, and cool like ice tech.
  • 7 0
 Although I'll likely never own one, I admire watching speciality tools like dial indicator in action.
  • 11 4
 So you need 400$ equipment to straighten a 30$ rotor.
  • 6 0
 Most people will be fine with just the rotor truing fork (DT-2). Only like $20.
  • 3 0
 probably why they show you how to true it on the bike, without the fancy stand & truing gauge
  • 3 0
 Old crescent wrench (wiped clean) and your caliper should be 90% as effective.
  • 2 0
 Definitely. A crescent wrench is also a great derailleur hangar truer.
  • 2 0
 @sampolicky: Indeed. I've used the diy versions of many "multi-purpose" tools on bike, on ground and in stands. I only have the "400$ equipment" (which would actually be more as depicted in the most-tooled case in the video) because I know a guy who knows a guy. Otherwise a 6" crescent wrench is possible to fit in a tool bag and definitely in your backpack if you choose to carry maximum tools on rides.

I've mentioned it before...you miss a great opportunity to learn and bond with your bike when you wrench it. If it turns out the rotor remembers it prefers to be bent then sure, replace it, but you won't have lost anything in trying to make the fix.

As for using "proper" tools on a mountain bike...go ahead. But like anything else in moderation, a tool of necessity can get the job done with patience and thought. A rock might be pushing it in this case, but rock or walk...you choose.
  • 2 0
 Anyway this is the best and most useful video ever...
  • 3 0
 I've done this a lot on many bikes over the years as that rubbing noise drives me nuts!! I just used a crescent wrench for this fix. Yeah I know........ This is the only time I will condone using a crescent wrench on any part of a mountain bike. But I have never had an issue and who doesn't have one of these lying around. Just adjust it inward so the rotor sits tight. Pro tip!
  • 4 0
 That last tool the DT-3i.2 is trick. Of course I’d need the truing stand so never mind. Lots of good tips though!
  • 3 0
 This video has very nice features and for some reason it's unbelievably relaxing
  • 4 0
 It's because of the moustache. Anyone wearing a moustache like that must be absolutely relaxed.
  • 2 0
 This post comes at the perfect time! My wife took a tumble in the trails and bent a rotor. I was getting ready to buy a new one!
  • 8 0
 Make sure you check whether your wife is ok before you bother with the rotor. She'll appreciate that.
  • 6 0
 Wife or rotor ?
  • 5 0
 @konacyril: whichever is cheaper really.
  • 3 0
 @tmcphail661: Shady business, this. Glad Calvin came along to set things straight and true.
  • 3 0
 Am I the only who just trues my rotors with my hands? (as long as they're not still hot)
  • 1 0
 I have tried that before, especially when you out on the trail and you have a spill.
  • 1 0
 The oils on your finger tips don't mix well with braking surfaces. If I were you Id use some sort of oil free, non-marring tool.
  • 1 0
 Very true but when you fall on the trail, you are stuck in a powerless situation. But mostly I have gloves on! I have to say that since I have switched to shimano from hayes brakes I have yet to have a bent rotor!
  • 1 0
 Super cool fun! I have never had great success in trying to true a rotor but this video was a great example on how to do it right!
  • 2 0
 All these tools and they didn't even include the polygraph that should be used before step 1.
  • 2 0
 That Knipex adjustable wrench works wonderfully for this. Flat jaw and strong grip.
  • 1 0
 Best video ever!!!! It is so cool and useful that there are no such words to describe it!!!! I will definitely buy one of Park Tool tools as a thanks to this video!!!!
  • 3 1
 Also, don't true with fingers after long downhill! ;0
  • 2 0
 Good stuff! Next vid should be how to true a Wheel Big Grin
  • 1 0
 Actually there are a huge amount of videos how to true a wheel on youtube... Besides you need only one 5$ tool to do this. Also it is more simple than it looks like...
  • 1 0
 I just need the lamp and my hand to fix that problem. And brake cleaner to degrease the disc finally.
  • 1 0
 perfect timing on this one maybe I can save one of these ridiculously price ice tech rotors I've some how managed to mangle
  • 1 0
 I just put the bent one on my kids bike... vwalla... great read/video.....
  • 1 1
 Hahaha reparing a disc s orientation when the deviation is so small like in the video is NON SENSE
  • 4 0
 Any contact between the pad/rotor will prevent the brakes from cooling off when you're not using them. Leading to brake fade.
  • 2 0
 @Jordanicas: also it is extremely annoying while riding. The sound of rubbing rotors causes me to cringe.
  • 2 0
 More of these please.
  • 1 0
 Mr Jones, you are a legend and a Gent. Love tech talk by Park tool!
  • 3 4
 this seems vastly over complicated...truing rotors is something anyone can do with a bit of common sense
  • 1 0
 Thats a very nice video.
  • 1 0
 Awesome!!
  • 13 16
 How to true a rotor:
Throw rotor in trash
Install new rotor
  • 10 4
 New rotors are usually not 'true'... So what you just keep throwing them till you get a straight one?
  • 2 1
 @clarky78: Gold for comment...!
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