Rotors out of spec? - 2018 KTM 790 Duke Forum
 3Likes
Reply
 
Thread Tools
post #1 of 11 (permalink) Old 02-04-2020, 11:18 AM Thread Starter
Junior Member
 
Rick's Avatar
 
Join Date: May 2019
Location: BC, Canada
Posts: 24
Rotors out of spec?

My front brakes have always had a low speed pulse but I never felt it at higher speeds. I was hoping that scuffing the rotors and dropping in EBC HH pads would help, but it didn't. With 3600km on the clock now and track days on the horizon it was time to spend the time measuring so my dealer can try to convince KTM to warranty them.

Right rotor:
Thickness variation: 0.00mm/0.000"
Runout: 0.05mm/0.002" (the limit for a car)

Left rotor:
Thickness variation: 0.01mm/0.0004" (not bad, maybe I just missed the tight spot)
Runout: 0.14mm/0.0055" at inner friction edge, 0.18mm/0.007" at outer friction edge

Bingo.

Has anyone else measured theirs?
Rick is online now  
post #2 of 11 (permalink) Old 02-04-2020, 12:34 PM

Super-Moderator

 
YoungLion's Avatar
 
Join Date: Aug 2019
Location: Victoria, BC
Posts: 140
Hey Rick!

Is there a point where KTM agree's it's sufficiently warped, like 0.10mm or something?

Just curious, so far nothing with mine but in case it happens I'll know what to look for.

Oh, and hopefully if KTM is covering the rotors they might approve an upgraded wave set from EBC for roughly the same cost but that would help you with braking and drop 4lbs of rotational mass??? Insurance companies do, somehow doubt Manufacturers would though.

My ambition outweighed my talent.
YoungLion is online now  
post #3 of 11 (permalink) Old 02-04-2020, 03:31 PM
Road to Victory
 
barbagris's Avatar
 
Join Date: Sep 2019
Location: On the edge of insanity.
Posts: 563
Garage
Quote:
Originally Posted by YoungLion View Post
Oh, and hopefully if KTM is covering the rotors they might approve an upgraded wave set from EBC for roughly the same cost but that would help you with braking and drop 4lbs of rotational mass??? Insurance companies do, somehow doubt Manufacturers would though.
With KTM selling their own lightweight rotors - I doubt it.

Small steps - Day by Day.
barbagris is online now  
post #4 of 11 (permalink) Old 02-04-2020, 10:03 PM
Senior Member
 
DaveNZ's Avatar
 
Join Date: Mar 2019
Location: Urenui/north of New Plymouth
Posts: 294
Quote:
Originally Posted by Rick View Post
My front brakes have always had a low speed pulse but I never felt it at higher speeds. I was hoping that scuffing the rotors and dropping in EBC HH pads would help, but it didn't. With 3600km on the clock now and track days on the horizon it was time to spend the time measuring so my dealer can try to convince KTM to warranty them.

Right rotor:
Thickness variation: 0.00mm/0.000"
Runout: 0.05mm/0.002" (the limit for a car)

Left rotor:
Thickness variation: 0.01mm/0.0004" (not bad, maybe I just missed the tight spot)
Runout: 0.14mm/0.0055" at inner friction edge, 0.18mm/0.007" at outer friction edge

Bingo.

Has anyone else measured theirs?
High speed pulse is usually due to warped rotors, low speed pulse and the pulse gets worse as you stop on light braking is usually due to hot spots on the rotors where pad material build up occurs. Try some wet and dry paper and give them a good scrubbing then clean with (i use electrical clearer) a good disc cleaner. Good luck.
DaveNZ is online now  
post #5 of 11 (permalink) Old 02-05-2020, 11:06 AM Thread Starter
Junior Member
 
Rick's Avatar
 
Join Date: May 2019
Location: BC, Canada
Posts: 24
Quote:
Originally Posted by DaveNZ View Post
High speed pulse is usually due to warped rotors, low speed pulse and the pulse gets worse as you stop on light braking is usually due to hot spots on the rotors where pad material build up occurs. Try some wet and dry paper and give them a good scrubbing then clean with (i use electrical clearer) a good disc cleaner. Good luck.
That's what I first thought as a mechanic, but I've scrubbed them twice now with 320 with no change. First when I put the EBC pads in, second when I measured the rotors on Sunday. I can usually see on customer's rotors where the trouble spot is, but the pad markings on these rotors look even. I pushed the pads back on the right brake to isolate side/side at first, you can feel the left get tight and free again. Again, this has happened since new, I just wanted to enjoy the bike and deal with it in the off-season.

When I first got the bike my shift rod was bent and had to get replaced, 0km. Maybe something got dingled in Austria on the left side? Who knows, haha.
J D and YoungLion like this.

Last edited by Rick; 02-05-2020 at 11:11 AM.
Rick is online now  
post #6 of 11 (permalink) Old 02-05-2020, 07:23 PM
Senior Member
 
DaveNZ's Avatar
 
Join Date: Mar 2019
Location: Urenui/north of New Plymouth
Posts: 294
Quote:
Originally Posted by Rick View Post
That's what I first thought as a mechanic, but I've scrubbed them twice now with 320 with no change. First when I put the EBC pads in, second when I measured the rotors on Sunday. I can usually see on customer's rotors where the trouble spot is, but the pad markings on these rotors look even. I pushed the pads back on the right brake to isolate side/side at first, you can feel the left get tight and free again. Again, this has happened since new, I just wanted to enjoy the bike and deal with it in the off-season.

When I first got the bike my shift rod was bent and had to get replaced, 0km. Maybe something got dingled in Austria on the left side? Who knows, haha.
As a thought, try loosening the bolts that hold the brake calibers on, do them up just finger tight, tape your brake leaver on full, then re-tighten the caliber bolts, could also try loosening the axle pinch bolts, pump the front end up and down (suspension) with brake on, then re-tighten pinch bolts. Prob may not help but will illuminate alignment and binding issues.
DaveNZ is online now  
post #7 of 11 (permalink) Old 02-06-2020, 04:00 AM
Road to Victory
 
barbagris's Avatar
 
Join Date: Sep 2019
Location: On the edge of insanity.
Posts: 563
Garage
A couple of weeks ago I was watching a mechanic doing disk runout tests on an old guzzi.

SOMETIMES it's not the disc at all - it's the hub or the mating of hub to disc carrier.

By rotating the offending disc one bolt at a time - he managed to get it decent. A bit of crud or paint incorrectly left on a mating surface will do it.

Small steps - Day by Day.
barbagris is online now  
post #8 of 11 (permalink) Old 02-06-2020, 02:48 PM
Junior Member
 
Join Date: Sep 2018
Posts: 21
Quote:
Originally Posted by barbagris View Post
A couple of weeks ago I was watching a mechanic doing disk runout tests on an old guzzi.

SOMETIMES it's not the disc at all - it's the hub or the mating of hub to disc carrier.

By rotating the offending disc one bolt at a time - he managed to get it decent. A bit of crud or paint incorrectly left on a mating surface will do it.
Very good point - it kind of goes along with KTM replacing my front wheel to solve this problem.
cster is offline  
post #9 of 11 (permalink) Old 02-07-2020, 01:15 AM Thread Starter
Junior Member
 
Rick's Avatar
 
Join Date: May 2019
Location: BC, Canada
Posts: 24
Quote:
Originally Posted by DaveNZ View Post
As a thought, try loosening the bolts that hold the brake calibers on, do them up just finger tight, tape your brake leaver on full, then re-tighten the caliber bolts, could also try loosening the axle pinch bolts, pump the front end up and down (suspension) with brake on, then re-tighten pinch bolts. Prob may not help but will illuminate alignment and binding issues.
I did that when I put on my Power RS tires at 2200km, no change. I'm used to doing that process from my DR650, and had help from a friend that evening that works on sport bikes. I re-did the caliper bolts before I measured the rotors just in case, as you also thought.

I've seen at least one here (cster and I thought 1-2 others) that had front wheels replaced due to rotor mounting flange machining. I'm hoping that's not the case here, I couldn't maneuver my dial indicator to check with the fork legs in the way. With 0.007" at the outer friction edge of the rotor and 0.0055" at the smaller diameter, it may only have to be 0.003" or less at the flange to do it and the dial indicator may fluctuate between points as the tip has to get moved back each time.

Still waiting on KTM's response.
Rick is online now  
post #10 of 11 (permalink) Old 02-07-2020, 04:50 AM
Junior Member
 
Join Date: Jan 2019
Location: Sydney Australia
Posts: 26
I had the same issue with mine. Faint pulsing around town became annoying when braking from above 100km/h. I mentioned it at the 12 month service and they found one disc runout was .25mm. KTM limit is .10mm so they replaced both front discs and pads under warranty. It was around that time we found the rear pads had worn out and cooked the disc at just 12,000km - had to pony up the cash for that. So if you ride in traffic I suggest you check your rear pads often.

Tom in Sydney
Shultz is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Warping front brake rotors yaMan KTM 790 Duke Issues And Problems 26 10-23-2019 05:39 AM
Galfer rotors shave Weight RAINDOG 790 Duke Suspension And Brakes 16 07-24-2019 10:44 AM
OverSize Brake Rotors J D 790 Duke Suspension And Brakes 2 07-23-2019 02:39 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome