Warped Front Rotors- machine or replace?

[Mtbjay]

At appx. 13,000 miles I detected a slight vibration with mild front brake application. I suspect it's a warped rotor. I'm surprised by this and am wondering if, A) others have experienced this and, B) if it would be better to have the rotor turned or replaced (I'm at 15,000 now). If replaced, is there a better, more durable, rotor to install? Would a different pad compound be recommed?

I live in the often wet northern Oregon and ride the bike quite aggressively at times. I am riding one-up 99% of the time, tour 2-3x/year and ride dirt-gravel only 10% of the time.


Ignorant in Sherwood


(P.S.I had the bike inspected @12k, so presumably it's not a loose head bearing.)

 

[Harry Dresden PI]

Not sure of the cost of new rotors ... but I know when you grind a rotor thinner it is more prone to heat warpage ... so if you ride the brakes the same way the ground rotors would likely warp sooner than OEM new rotors

 

[yz454]

If you want i could come up and check them out , I,am in Newberg .
.

 

[markjenn]

As I understand it, motorcycle rotors are made of stainless steel and can't be "turned" like car rotors which are made of cast iron. They can be ground but they seldom have enough extra thickness to meet spec afterwards. If they are out of spec, replacement is what is usually recommended.

- Mark

 

[offcamber]

Agreed I don't believe they can be turned, best bet is to replace them. Check the run-out on them before you replace, to make sure they are warped. Should be a spec in the service manual. If you don't have it many of us here do we can look it up for you.

 

[2112]

If you do decide to replace the disc's don't be tempted to replace them with anything from China.... They seem a bargain but are utter poo.

 

[Lutsie]

I can check the specs in my service manual but I would be surprised if you could turn them, and still be thick enough for use. Have you checked for hot spots on the rotor? You can also easily check to see if they are warped by taking a straight edge (ruler would work)putting it under the rotor, parallel, as close as you can get with out touching and spin the tire any warpage (enough to be concerned about) you will be able to see, repeat for the opposite side. If no warpage is found treat for hot spots

 

[barkingllizard]

replace.....

 

[BravoBravo]

replace.....

Yep. ::026::

 

[TO Eagle]

Similar experience.

I wouldn't describe myself as a 'heavy' braker, but had to replace the front rotors at around 7000 miles after the telltale low speed vibration set-in.
This was while touring two-up through the Rockies.

Was kinda surprised and disappointed at the time, but hey, sh1t happens. Cost of replacement wasn't too bad even in price inflated Canuckistan.

 

[~TABASCO~]

REPLACE.... with stock or maybe Galfer

 

[ejy712]

Woody's Wheel Works straightened my rotors after an accident. They did a good job...

 

[Derekj]

Always replace.

 

[EricV]

Replace.

FWIW, we all experience heavy braking during some ride. What can easily warp a rotor is coming to a stop, and sitting there with the brake applied. It warps the rotor because there is no air flow and the area where the brake pads are clamped to the rotor will stay hotter than the rest of the rotor. Most folks that have done track days know this as it's one of the things they teach you coming off the track, don't set the parking brake on a car, don't sit stopped with the brakes applied on either car or bike. It takes surprisingly little time to warp a rotor if it's hot enough. Like the duration of a loooong street light at the bottom of a mountain pass as you came into town.

 

[twinrider]

30,000 miles on my S10, rotors are fine. Mix of commuting and touring, I do use a lot of engine braking...

 

[Don in Lodi]

It would have to be a pretty heavy bend in the rotor, or a hot/hard spot. If I understand the whole floating rotor thing right, the pucks allow the rotor to run true to the hub even if the rotor isn't true by itself on a straight edge. Seized pucks? Warped rear? Non floating rotor there, floating caliper.

 

[Lutsie]

Floating rotors allow for natural flex from the front end including the hub, rotor mounting, and the flex from the forks under breaking and the lateral flex while leaned over all within spec/the reason floating rotors are a benefit but when a rotor is bent it forces it straight when it passes threw the caliper(the caliper which doesn't want to flex, ie monoblock calipers) which translates into the bars as stearing head shake, warped and hot spot rotors create uneven surfaces that allow the pads to jump translating back into stearing head shake.

The straight edge at the bottom of the rotor will show you if it flexs/waves to the left and right which means it is warped, if it flexes to the left or the right it is bent. If there is no noticeable flex it could just be hot spots.

Learned ask about this when my brother in law bent both front rotors mounting a front tire with the rotors on, on a hydrologic vehicle tire mount.

 

[Mtbjay]

Thanks for all the replies! Considering the cost of rotors, I'll have to wait. I've not attempted to measure anything yet. Can a hot spot be removed? What's a hot spot anyways? I know my dog is prone to them...

 

[Don in Lodi]

High rotor temps and uneven cooling will give hot spots, metallurgically, they are really hard spots in the metal. The hard spots are resistant to wear and become high spots in the surface of the rotor. When a pad hits the high spot you get a pulse. On a well polished automotive rotor they show up as one or more dark patches reminiscent of a leopard skin pattern. On an MC rotor you don't usually get the high polish, just an LP record set of grooves so they really don't show up well.

 

[Lutsie]

Mtb - try taking a scotch brite pad to the rotors all the way around in a circular motion, wipe down with brake cleaner and a microfiber cloth. The idea is it will ruff up the hot spot and allow for proper friction for the pad.