Tolerence on warped rotors?


Fastfrog007

Donating Member
Registered
#1
I've got me at least 1 maybe even a pair of warped front rotors. I can fell it under braking, so this isn't about if 1 is, but if both are?
I checked em with a dial indicator and one came up as 28thousandths worth of wobble, the other around 15thousandths. I replaced the worse one with a locally sourced rotor, which and up being 40thousandnths worth of wobble.

So,what, if any is accepted wobble?

Ps- someone sell me some rotors at a good price. :laugh:

Indicator used, I just stuck it to a metal stand, put it against the outside of the rotor and spun the wheel gently after I took of the calipers.


ForumRunner_20130505_220352.png

ForumRunner_20130505_220352.png
 

880jedi

Registered
#2
I'd buy 2 new ones, and measure them as soon as they're mounted. If they're perfect, that would be great, but I'm sure they will be off a very small amount and that will give you a baseline to gauge them.
 

rubbersidedown

BUSA-RIDIN'-BASTID
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#3
Personally I wouldn't be able to stand any pulsing thru my brake lever. Also,check calipers to make sure they aren't sticking,wheel isn't slightly warped,etc and causing the over heating...before installing new one's. yer manual will have exact run-out figures,but who cares right,the constant heat build up will wear pads faster,lead to brake fade,warp new rotors,blah blah blah. Big Harleys like my bagger (900 lbs,unloaded?) like to chew up rotors,so I whent with good quality floaters,so it never happens again.

RSD.
 

Tufbusa

Track Coach / TufPoodle Coach
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#4
Rooster man, your test methodology does not mean you have a warped rotor. The rotor floats and is rarely true when you test it with a dial indicator.

You would not the first to "Think" you have a warped rotor only to find the dial indicator did not like the new one directly from the factory.

Before you shell out the $$$ be sure you are doing so wisely young grasshopper!
 

Fastfrog007

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#5
Rooster man, your test methodology does not mean you have a warped rotor. The rotor floats and is rarely true when you test it with a dial indicator.

You would not the first to "Think" you have a warped rotor only to find the dial indicator did not like the new one directly from the factory.

Before you shell out the $$$ be sure you are doing so wisely young grasshopper!

Thats why I post here Sensi Tuf :laugh:

I felt a rhythmic pulse while braking last weekend that I thought was a warped rotor. I know the rotor was mounted properly and torqued to spec as of the begining of the season. I was able to get one rotor locally, so it become a game of which one to replace. Got the indicator out hoping it would give me a clue. I changed the rotor that moved the indicator the most, made sense to me. The replacement rotor was worse, a very noticable swishing sound as it passed through the caliper. I took that one off and put my rotor back on, still have a pulsing when braking. I changed out my brake master cylinder to the stock unit again last night and bled it, I had an 09 GSXR1000 master on there that just never bled right and was always squishy. So at this point, I can only think its a rotor issue, as the pads were new this season aswell.

Any methods to check which rotor is warped?


My bike seems to just hate me this year :down:
 

rubbersidedown

BUSA-RIDIN'-BASTID
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#6
I used to have access to a thick slab of machined steel. Perfectly flat. Applied pressure to the center and stuck a feeler guage in between the two surfaces I was checking for warping. The other method I would use was to mount a brake rotor to a metal lathe,then use the dial indicator. But as Master Po above mentioned it is harded to do with todays floating rotors. A pulsing brake lever almost always means warped rotors,but could also be other things. A pulsing brake pedal in a car can just mean worn out or mis-adjusted wheel bearings etc.

I would hit up the nearest Busa Buddy and swap out wheels for a test,probably the fastest, easiest way to your answer.

RSD.
 
#7
What I thought was a warped rotor actually turned out to be a slightly bent rim. I like the idea of swapping wheels to compare. If you conclude it's the rotor, I would replace as a set.
 

Tufbusa

Track Coach / TufPoodle Coach
Registered
#8
If your rotor is warped it will push the pistons back into the caliper housing causing the lever to travel farther the next time you apply the brakes. That's why I ask how many times you had to pump the lever to get brakes.

Take your bike for a ride and return to the garage (Check the axle torque before the ride. Loosen the pinch bolts first.) Put her up on the stands so the wheel will spin freely. Turn the wheel by hand slowly. If a rotor is warped the wheel will have considerable drag for the first revolution. Then the wheel will turn freely yet drag in one particular spot. At this point check your free play in the brake lever. if the rotor has pushed the pucks back there will be considerably more free play in the lever. If the rotor is bent severely the lever may need to be pumped more than once just to get brake pressure.

Another true test is to take the beast up to triple digits and apply the brakes heavily. If the rotor is bent the front will chatter at high speed while under heavy braking.

You can check ten bikes with a dial indicator and 9 of them will show one or both rotors are out of sink.

At this point, if you are still convinced you have a bent rotor, put the dial indicator on the center carrier which is aluminum. Unless you have pinched the outer (Steel) rotor in the tire machine or has a serious front end impact the outer steel ring is not bent, it's the aluminum carrier. The inner carrier is rigid and has no movement so it's easy to check.

And lastly, don't go spending big bucks on wave rotors thinking they will give you better brakes. They won't!
 
#9
I had this problem 2 weeks ago on my B-king. I thought my rotors were warped but they were weren't. The problem was that the buttons that attach the rotor to the fixed part of the disc on the rim were basically seized. On modern bikes like ours we have what is called floating rotors. The buttons are designed to allow the outer disc to move minimally side to side as the brakes get hot and expand. If the buttons are seized from road grime and brake dust, the floating part of the disc becomes fixed, and gives the feeling in your lever that the rotor is warped. A member on another forum sent me a link which I am unable to upload from Youtube that shows how to clean the buttons and allow them to move freely again. Go to YouTube and look up "Cleaning Motorcycle Rotors" it comes up and I can attest that it really worked. It only took about 20 minutes on each side and my brake pulsating is gone. This may or may not be your problem but it was in my case and it saved me tons of cash, about $425 to be exact.
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
#10
I made the same mistake and assumed my rotors were bad when they were 'chippy' about a year ago. How long since you had new bearings, as that was my problem, not the rotors....but I like that bobbin trick (minus lube) and think that makes for a good idea to try first....
 

Fastfrog007

Donating Member
Registered
#11
Bearings are a year old, came already installed on the CZ wheels.

Thanks for all the tips guys, ill start with the easiest, least invasive thing and work my way in. :thumbsup:
 

_WOLFMAN_

Canuck Ground Pilot
Donating Member
Registered
#13
Check your wheel bearings I have CZ Wheels on my Gen 1 and my buddy has them aswell on his Gen 2 and both of us had to replace front wheel bearing because original ones installed by Carrozzeria went bad within a couple riding seasons.
 

Fastfrog007

Donating Member
Registered
#14
Check your wheel bearings I have CZ Wheels on my Gen 1 and my buddy has them aswell on his Gen 2 and both of us had to replace front wheel bearing because original ones installed by Carrozzeria went bad within a couple riding seasons.
Good to know, I'll keep an eye on em,,good so far!
 

Fastfrog007

Donating Member
Registered
#15
Update time!


Mo'Busa sent me a pair of rotors to try out, and sure enough, it feels much better. I've still gotta try em at higher speeds later on tonight when traffic clears,but 80 and below feels much better.
Just for fun, I put the dial indicator against the new rotors the same way I had with the old ones, these spec'd out at between .004-.005 each. My old ones were .030 and .015 on either side.

I'm not sure how useful any of this is to know, but it I figured I'd post it anyway.

Now to work out some pricing with Mo, I'm hoping he'll accept a jumping high five as full payment. :lol:
 

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