Rotor float. How much is too much?

DBragg

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Oct 31, 2005
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Hi I have been lurking a while and have found most of what i need for my 01 220. However, I havent been able to come up with search results regarding the amount of float in the rotor.

I can tell the the rotor is floating and it almost seems like too much. Just eyeballing the play, the float in the rotor allows the wheel to move 1/8th to 1/4th of in inch as measured at the outer diameter of the tire. It also makes an audible click (or light clunk) at the limits of the movement. This is as measured on the stand with the front brake depressed, while moving the wheel fore and aft by hand.

Intuitively, I would think that I shouldnt get any free play when moving the wheel by hand. How much free play should the rotor be allowed.

Am i being paranoid? Or do i have a legitimate gripe?
 

julien_d

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Oct 28, 2008
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"rotor" could mean two things. The flywheel, which is behind the stator cover, or the brake rotor on the wheel. I think neither refers to what you are talking about. If you have it in gear, and the rear wheel is able to rotate slightly forward and back, this is normal. Think of all the components that are in between.
 

IndyMX

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Jul 18, 2006
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julien_d said:
"rotor" could mean two things. The flywheel, which is behind the stator cover, or the brake rotor on the wheel. I think neither refers to what you are talking about. If you have it in gear, and the rear wheel is able to rotate slightly forward and back, this is normal. Think of all the components that are in between.


Since he did mention the tire and front brake in the post, it's pretty safe to assume he's talking about the brake rotor.
 

julien_d

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Oct 28, 2008
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Yes, that's what I assumed.

Remember, the chain has slack, plus there is some small clearance between the transmission gears and also the main gears on the clutch side. So yes, some movement of the back wheel is normal.
 

IndyMX

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julien_d said:
Yes, that's what I assumed.

Remember, the chain has slack, plus there is some small clearance between the transmission gears and also the main gears on the clutch side. So yes, some movement of the back wheel is normal.


I think he's talking about the front wheel, as he did mention the front brake..

I don't think it's got anything to do with the chain and whatnot..

My guess is the rotor is roached. It should have a little play side to side, but I don't believe front to back movement is a good thing.
 

_JOE_

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May 10, 2007
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I'll play!

I ran this one through the KDX Speak Translator and it said- there is approximately 1/8 to 1/4 inch of rotational movement in the front tire/wheel assembly with the brakes applied and the front wheel off the ground.

My guess, in the above described situation, would be slight movement of the brake pads in the caliper bracket. Its also possible the bracket or caliper could be loose.
 

_JOE_

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May 10, 2007
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Now if the hub is turning as the caliper holds the rotor it's a whole different ball game. That's probably gonna be loose or worn mounting bolts/holes.
 

_JOE_

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May 10, 2007
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DBragg, go do this again and pay close attention to the hub and caliper. Do the hub and rotor turn as a unit? Does the rotor feel solid side to side? Any cracks? Does the caliper move slightly as you turn the wheel? If so, does the bracket that bolts to the forks also move?
 

julien_d

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Oct 28, 2008
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Front wheel then, huh?

I'm going to refrain from making any more pointless guesses until the OP clarifies what he is talking about. Seems to me that it would be obvious that the rotor is bolted directly to the hub, and not cushioned in any way, and so should not move freely from the hub in any amount.
 

dirt bike dave

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May 3, 2000
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Not 100% sure about the 220, but I know many bikes have a floating front rotor.

What he is saying is when he holds the brake on, he can spin the front tire forward or backward 1/8" to 1/4", as measured at the tread of the tire.

While I have not measured one in such a fashion and don't know what normal is, IMO a little play in a floating rotor is how it is designed, and not something to worry about.

As to the clicking, also normal. Many bikes will do this if you take the bike off the stand, hold the brake on and try to roll it.

With a floating rotor design, the braking surface of the rotor is free to move around a little, so when the pads try to grab it, the rotor will align to make the best contact with the pads. Also, less vibration from the braking is transmitted to the tire, and less heat is transmitted to the hub and bearings.

You could remove and inspect the rotor for peace of mind, but I doubt if you will find anything wrong.
 
Last edited:

dirt bike dave

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May 3, 2000
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julien_d said:
I am 100% sure that the kdx does not have a floating rotor. As I mentioned above, the rotor is bolted directly to the hub.


If the disc is two peices, with an inner section and an outer section, and the two sections are connected by little insulating 'buttons', it is a floating disk. The inside portion does indeed bolt directly to the hub, but the little buttons allow the outer portion to move a little and 'float' from the inner portion.

I know the KLX has a floating disc, and I'm pretty sure the H series 220 and 200 have one as well.

FWIW, I checked the parts fiche at www.buykawasaki.com I put in for an '03 220 and the picture was of a floating disc.
 

julien_d

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Oct 28, 2008
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Good to know. My E series rotor is def one piece. I'll have to double check the H, i was sure they used the same part. Wouldn't be the first time I was wrong. :)
 

DBragg

Member
Oct 31, 2005
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I apologize for the vague nature of the original post. I could see exactly what I was talking about, in my mind's eye, hehe. I guess you guys are not mind readers.

The front brake rotor is that part I am talking about. The movement, and my estimated measurement, were made with the front brake applied and the front wheel off the ground. However, the movement is noticeably felt with the bike on the ground while rocking the bike back and forth with the front brake applied. Yes the 220 has a floating front rotor. Its a two piece rotor, an inner and an outer piece, coupled by large round “rivets” or "bottons," as previously observed.

Its rotational movement of the front wheel, as described in a previous post. However, the brake caliper and/or pads are NOT the culprit. I can see that the outer part of the rotor is not moving (its clamped by brake), whereas the inner part of the rotor is slightly rotating with the hub when applying rotational force to the front wheel. It does NOT appear to be play in the hub and or spokes. The rotation (play?) is observed at the “rivets” of the rotor. The amount of movement at the “rivets” is small but translates to approximately 1/4th of an inch of travel as measured at the tire.

Clear as mud?

Thanks for the replies thus far. This board rocks!!! heres a nana for you guys :yeehaw:
 

julien_d

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Oct 28, 2008
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Aha. So your floating rotor is floating, and that is bothersome? I do not know how much it should be able to move. I would not think 1/4" at the outer diameter of the wheel would equate to a very large amount at the rotor.
 

DBragg

Member
Oct 31, 2005
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julien_d said:
Aha. So your floating rotor is floating, and that is bothersome? I do not know how much it should be able to move. I would not think 1/4" at the outer diameter of the wheel would equate to a very large amount at the rotor.

Bothersome? No. Concerning? Yes. All components that are subject to wear typically have wear or play limitations. Generally speaking, when something is worn beyond (generally well beyond) it's service limit, it fails. The failure of a front brake rotor has the potential to be catastrophic, particularly on a steep, loose, and rocky downhill.

The amount of play in the front wheel, caused by the rotor, is not something that I have seen before. I have also never owned a dirtbike with a floating front rotor. Thus I asked the question.
 

_JOE_

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Interested to hear if this is normal. You'd think there shouldn't be any movement in that direction.....
 

julien_d

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Oct 28, 2008
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Right, more of an in/out than a forward/back, I should think. There's a kx125 out in the shed that has the same type of rotor, I will have a look at that. My neihbor has to H series KDX's as well, so I can have a look at those this weekend.
 

OldDirtKDX

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Dec 14, 2004
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Within normal parameters

As desribed, the movement you are seeing is normal. Given the manufacturing tolerances in the in the "Buttons" between the fixed center and the floating disc rotor coupled with the play in the caliper holders, the movement at the outer circumferance of the wheel/tire assembly will be as you described. When holding the brake on and moving the wheel assembly back and forth. Just a few hundreths of play will be multiplied exponentially. Fortunately, the braking forces are in one direction. Therefore it isn't noticeable while riding. The "clicking" is just the result of the play.
If you really want to freak yourself out, check the play and the resultant noise after a "hard on the brakes" ride. The Outer, floating disc expands as it gets hotter, more so than the center and buttons causing quite a bit more play and noise.
Don't worry, you wont hear the noise or feel the play while you're riding. Ride hard, brake hard!
 

sr5bidder

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Oct 27, 2008
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just checked my 98 200 and it does the same thing. had it for 4 years and never took note!! the movement is so small at the brake ring you can hardly see it but at the out side of the tire it moves 1/8th to a quarter.

I checked the service manual and it has no info on the rotational service limit only the run out ...spec is .2mm or less / service limit is .3mm

front rotor bolts toque 16.5 ft. lbs with non perm. thread locker
 

DBragg

Member
Oct 31, 2005
32
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Thanks OldDirtKDX and sr5bidder

Ahhh... its good to know that its not just my rotor. Having no specified play limit in the service manual is what had me worried. My assumption was that if there is no play limit, then there should be no play.

I may just go ahead and grab a solid rotor when my cash flow allows. It depends on how comfortable (uncomfortable) i am with the rotor in time.
 

sr5bidder

Member
Oct 27, 2008
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DBragg said:
Thanks OldDirtKDX and sr5bidder

Ahhh... its good to know that its not just my rotor. Having no specified play limit in the service manual is what had me worried. My assumption was that if there is no play limit, then there should be no play.

I may just go ahead and grab a solid rotor when my cash flow allows. It depends on how comfortable (uncomfortable) i am with the rotor in time.


mine has the same play as yours does and I am not going to worry about it and I am not going to buy a new rotor, it has probably always been like that. I will however check it in a few years and see if there is more play.

the way i see it the rotor should be backed up againsts the innnerhub 98% of the time and only shift the other way when hitting the front brakes while sliding backwards down a hill or when you are unloading it.
 

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