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 In need of an opinion

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mikecanz
Carlotto
Carlotto
mikecanz

Posts : 26
Join date : 2019-05-11

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PostSubject: In need of an opinion   In need of an opinion Icon_minitime1Sun Jul 12, 2020 9:11 pm

I've been trying to chase down a pulsation/drag on my front brakes for a while now. The dealer I have it under warranty with ended up replacing RH rotor and getting the hub surface machined saying that only the one side was out of round, but seeing as I still have the same problem something is surely not right.
Being in automotive it feels as if the disc is out of parallel. As you brake only with the fronts you feel like bike bucking like a horse or like a caliper is dragging on the high spot of the rotor. I've checked the bobbins and there is lots of free play and they move nicely. Before I reluctantly send it back to the dealer for warranty I'm looking for suggestions as to what I may be overlooking.

I'm going to pinch off a hose tomorrow and see if I can narrow it down to one side.

I appreciate any input! Thumbs Up
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Bill Hagan
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Bill Hagan

Posts : 1382
Join date : 2014-07-03

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 4:26 am


All the "fixes" so far seem to focus on the rotor(s).  That is, of course, where most such issues are found and resolved.

Is it possible, however, that the RH caliper (and thus pads) is somehow a bit misaligned?  Hard to imagine how that could be if both bolts torqued to spec, but there you have a likely useless offering meeting, at least, your "any input" standard. cheers

Bill
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GuzziSteve
Fra Cristoforo
Fra Cristoforo
GuzziSteve

Posts : 353
Join date : 2016-04-14

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 6:08 am

Maybe the forks are not parallel, Did the dealer box the front end before tightening the pinch bolts?

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eeyore
Grignapoco
Grignapoco
eeyore

Posts : 148
Join date : 2016-09-09

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 6:33 am

Another possibility - usually a car related problem but it may also happen on bikes.
After a high speed emergency type stop and the brake pressure is not released after reaching a halt then a very fine coating of pad material gets transferred to the disc. This gives the feeling of a warped rotor but when checked with a vernier everything appears to be within tolerance.
Probably more common in the UK with excessive traffic. Seems to affect big luxury German barges (high power, weight and usually auto).

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hipower
Carlotto
Carlotto
hipower

Posts : 37
Join date : 2020-06-06

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 10:02 am

Buy a dial indicator and see how out of round the rotor is. It should be a floating rotor so I'd check the parts that mount on the hub.

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paulbrice
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paulbrice

Posts : 897
Join date : 2015-01-04
Age : 59

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 2:51 pm

In case it helps (or gives something else to check !) I had similar problem with car discs a few years ago....Basically I bought new front discs and pads from MrAuto using registration/model details and fitted them no problem & drove it fine....... Several hundred miles up the road started getting weird rubbing and sensation with brakes (different than steering wheel waggle & judder you get with warped discs)...turned out the 'cheap replacement discs' were smaller than standard & disc pads were running higher than top of disc outer lip. As soon as pads started wearing they were rubbing top of the rotors which weren't (not even supposed to be) perfectly round......
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mikecanz
Carlotto
Carlotto
mikecanz

Posts : 26
Join date : 2019-05-11

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Mon Jul 13, 2020 9:30 pm

Thanks for all the responses gents. After pinching off each caliper and riding the bike, the worst drag ended up coming from the side that was recently machined and had the rotor replaced. I took both calipers off and did a little service to the pads, greased up the slides and the pistons. I removed both rotors from the hubs and cleaned the mating surfaces. I ran brake cleaner through all the bobbins and torqued the rotors on the hub. I also bled the fronts. I'm happy to say the drag or bounce is much less apparent now and I'm probably on the right track. I find it hard to believe the other rotor is out of round now or the hub isn't perfect on that side.
Just to re iterate I do not feel anything in the lever itself only in the bars. I would equate it to hitting moguls when you come to a slow stop. If this was a vehicle I'd be machining rotors or flat out replacing but car rotors and motorcycle rotors (especially these kind) are two very different animals.
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bahamazoo
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bahamazoo

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Tue Jul 14, 2020 3:14 am

aaaaand don't forget to check the bobbins for 'free play'....
they are supposed to move in their slots and allow the disc the 'adjust' for 'imperfections'....
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Omnis
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Omnis

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Join date : 2014-10-06

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PostSubject: Re: In need of an opinion   In need of an opinion Icon_minitime1Tue Jul 14, 2020 12:24 pm

I had exactly the same issue (like hitting moguls coming to a stop). Ended up replacing both rotors.
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