Bent front Axle ?

[Dan E]

Trying to isolate a slight front end wobble...rebalanced the tire/wheel...was fine. rotors are flat...but when I spin the front wheel...looking from the front..it looks like the rotors are not round..the top edge appears to rise and fall slightly. The Rotors are tight, no wobble on the wheel. Pulled the axle and rolled it on a glass coffee table..seems to have a slight bend perhaps ? ever so slight ? You can hear the un-even ring as it rolls on the table, kinda like it sounds when the bike is rolling at slow speed. Anyone have this issue ?

Thanks / 2006 FZ6 / 30K

 

[Motogiro]

The axle does not turn as the wheel is turning. I would also worry if my axle had runout and I'm thinking you shouldn't see any runout. To tell the truth I wouldn't use a glass table as my only source. I would take it to a machine shop.

The rotors actually float and are moveable. Sometimes the large rivet like parts get seized and need a little TLC so they can float correctly because when they don't you can get vibes especially when braking.

You can use a little motor oil on them and gently tap the edges of the rotors back and forth using a rubber mallet. Clean any oil off the rotors with acetone or brake cleaning agent. Keep oil from getting on brake pads. You only need a little oil.

 

[ChevyFazer]

My friend who is one of the best moto mechs ive ever met swears my front Axel is bent....he was over at my house watching me fix a bend in the lip of my rim and when I put the wheel back on he noticed it barely rocking back and forth (so little that I didnt see it) as the last few threads were being tightend. He swears that means my axle is slightly warped but I have noticed no adverse affects, vibrations, or unusual tire wear. I trust him very much so we went to highschool together and he went on to mmi or something similar but I cant tell anything is wrong. He said I wont until the bearings start to go wich makes complete sense so....long story short im on the hunt for a axel

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[Sawblade]

The rotors actually float and are moveable. Sometimes the large rivet like parts get seized and need a little TLC so they can float correctly because when they don't you can get vibes especially when braking.

You can use a little motor oil on them and gently tap the edges of the rotors back and forth using a rubber mallet. Clean any oil off the rotors with acetone or brake cleaning agent. Keep oil from getting on brake pads. You only need a little oil.

I must try this! I've been getting some pulsing in my front brake.

 

[FinalImpact]

Is there some logical reason your axles would be bent?

As in "FINAL IMPACT" with some object?

IMO - worst case is it might wear the bearings sooner than a perfect axle. Beyond that a tiny curve is not likely to change anything.

PS - most glass is far from flat. Looking about my place i see nothing I would call flat when we're talking about measuring a few thousandths. . . .

 

[Jugro]

Rolling the axle on a flat surface is mentioned as the way to check it, in the service manual in section 4-3.
They don't even specify a tolerance, either of the axle or the surface required for the test.
So it is not like Yamaha is concerned with a few thousands.

 

[ChevyFazer]

Is there some logical reason your axles would be bent?

As in "FINAL IMPACT" with some object?

IMO - worst case is it might wear the bearings sooner than a perfect axle. Beyond that a tiny curve is not likely to change anything.

PS - most glass is far from flat. Looking about my place i see nothing I would call flat when we're talking about measuring a few thousandths. . . .

I dont think it was from anything I have done but rather the previous owner
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[FinalImpact]

Is there some logical reason your axles would be bent?

As in "FINAL IMPACT" with some object?

IMO - worst case is it might wear the bearings sooner than a perfect axle. Beyond that a tiny curve is not likely to change anything.

PS - most glass is far from flat. Looking about my place i see nothing I would call flat when we're talking about measuring a few thousandths. . . .

I lied! I do have this and its for sale....... hint hint hint

OK - going back to the OP's statement he says this about the rotor.

the top edge appears to rise and fall slightly. The Rotors are tight, no wobble on the wheel.

So this implies no side to side run-out but says it more of an eccentric action whereby the edge of the rotor moves up and down. I would have to say its very unlikely this form of run-out is causing an issue. Example: if he measure the difference between the hi spot and the low spot its likely very small and mass wise doesn't change anything regarding balance or braking. The pad and caliper won't care too much about this.

IF you can see the outer edge of the wheel and tire are not holing a perfect circle and are eccentric, now this could cause a vibration. But don't jump to conclusions as rotating the tire on the wheel could fix the problem. Example deflate the tire and rotate it 90degrees and inflate and test.

BUT IF you think the wheel is at fault, the tire would need to be removed to v-block the wheel and measure the bead area where the tire is seated.

Wheel Spec at the tires bead area is:
Radial wheel runout limit = 1.0 mm (0.04 in) {eccentric runout

Lateral wheel runout limit = 0.5 mm (0.02 in) {side to side wobble

FYI: just because the casting shows a little deviation on the outside, it doesn't mean the inner bead where the tire is seated is out of specification. Its the inner bead that matters although if you can see the wheel physically move, it MAY make it harder to balance but allow the tire to still run true.

EDIT: looking at the picture - I could be wrong and maybe Yama'rs measured from the outside of the wheel? Hmm - I think measuring the bead is the best bet, but that requires tire removal.

 

[Dan E]

Will lube bolts and trying nudging the rotor...with a few light taps of the rubber mallet.

I just can't believe that the Axle Bolt would have any affect, on the issue. If is is bent..it is ever so slight...and I presume the axle does not ride on the entire length..but only at two contact points.
.
Thanks for the tip on the Rotors !

 

[TownsendsFJR1300]

You should be able to put the axle on the same glass surface and rotate it in the same spot looking for light underneath it. A straight edge (part of a square) placed up against the axle should show something as well.. If there's any doubt, I'd replace it as it'll cause early wear on the wheel bearings.

Also, how many miles on the front tire? If there's some cupping on it, it can cause the wobble.

Have the steering head bearings been serviced / replaced? Their known to come from the factory without much grease and fail.

 

[FinalImpact]

I have question for those of you state that the rotor is intended to float on the rivets. How is this possible if it has no gap or free play in relation to the rivets installed fit?

That is, the inner mounting ring and the rotor are the same thickness and the thinnest feeler gauge I have will not enter either side of the rivet. So how could it possibly float?

Rivets are meant to be pressed and displaced until parts are secure and nothing moves. There is no shoulder or stop to prevent the rivet from being the same thickness as the rotor and inner mounting ring. So I'm asking, where does it say anything about it floating and/or how is it supposed to float if its smashed tight.

Referring only to the FZ6 and not other bikes.

 

[TownsendsFJR1300]

I have question for those of you state that the rotor is intended to float on the rivets. How is this possible if it has no gap or free play in relation to the rivets installed fit?

That is, the inner mounting ring and the rotor are the same thickness and the thinnest feeler gauge I have will not enter either side of the rivet. So how could it possibly float?

Rivets are meant to be pressed and displaced until parts are secure and nothing moves. There is no shoulder or stop to prevent the rivet from being the same thickness as the rotor and inner mounting ring. So I'm asking, where does it say anything about it floating and/or how is it supposed to float if its smashed tight.

Referring only to the FZ6 and not other bikes.

I would think Yamaha, when assembling the rotors, uses a machine that presses those rivets in to a certain point then stops. Their obvously not a standard rivet pressed into place..

My FJR has floating front rotors too (looks like the same balibers as well), the rears are solid mount like the FZ (as most of your stopping power is in the front). Most any high performance bikes willl have at least floating front rotors.

You may not be able to feel them move (when stopped) but when leaning on them for a hard stop (high PSI in the line(s) and very high pressure on the pads against the rotors), the floating rotors will help center the rotor and give better braking performance and less shutter.

Look at any race bike and you'll see the same set up. A cheaply made bike or non high performance will have solid rotors as their not needed...

 

[FinalImpact]

I would think Yamaha, when assembling the rotors, uses a machine that presses those rivets in to a certain point then stops. Their obvously not a standard rivet pressed into place..

My FJR has floating front rotors too (looks like the same balibers as well), the rears are solid mount like the FZ (as most of your stopping power is in the front). Most any high performance bikes willl have at least floating front rotors.

You may not be able to feel them move (when stopped) but when leaning on them for a hard stop (high PSI in the line(s) and very high pressure on the pads against the rotors), the floating rotors will help center the rotor and give better braking performance and less shutter.

Look at any race bike and you'll see the same set up. A cheaply made bike or non high performance will have solid rotors as their not needed...

I hear ya, I'm just saying it mentions nothing in the manual and I can't make mine move nor am I about to smack them until they do.

I'm not sold on the fact that this application has the means to move at all. If it did it would create wear. If something wears it needs to be checked. Also the spec for lateral movement would be difficult if not impossible to measure if the rotor moved.

How much "float" are you talking about? 0.1mm?? Lets not confuse floating calipers with floating discs. The rear of the FZ has a floating caliper as the piston is on one side only and for the pads to wear evenly the caliper floats side to side moving during brake application and pad wear. The front calipers are mounted solid as they have pistons on both sides so there's no need to float the caliper.

I'll stand firm and say the disc on the front of the FZ does not float and the rivets are there to allow for expansion and contraction when the heat escalates during hard braking. In this case it isolates the hat section to expand and contract reducing the likely hood of warping.

- just my 2 cents although it doesn't help the OP's issue.

 

[stink989]

They are floating discs and do move on the rivets. Bikes that have done lots of miles or lots of hard braking will have wear on the rivets and will have lots of movement and some even rattle. On the back is like a spring washer set up.

 

[TownsendsFJR1300]

An interesting link for reading as well re floating disc's:


What is Full-Floating?

http://www.sportbikes.net/forums/track-days/3037-what-full-floating.html

The FZ is considered, at least in this articles, "semi floaters". Full floaters rattle considerably more by design..


Also, for the original poster, I did not see any spec's on axle run out in the FZ manual, however, per my old Goldwing shop manual, the axle is checked by using 2 "V" blocks at each end of the axle and rotating the axle. Using a dial indicator you'd measure the run out (if bent it'll go up and down in the middle) as you rotate the axle in the "V" blocks. Just as an FYI, the run out for the goldwing front axle is .008"..

 

[FinalImpact]

An interesting link for reading as well re floating disc's:


What is Full-Floating?

What is Full-Floating? - Sportbikes.net

The FZ is considered, at least in this articles, "semi floaters". Full floaters rattle considerably more by design..

Thank you, that is what I wished dispelled so owners aren't trying to DO something to attempt make the discs move when they really aren't intended to. It could be the rivet assembly has a Belleville washer (spring) so its always going to have tension on it from one side and it can move during thermal changes to provide a better thermal isolation barrier by being a semi-floater.

The manual states to measure and remove it and rotate it the distance of one bolt pattern, reassemble it and re-check it. If it cant be corrected by doing this, replace it. There is no fixing it.

In short, the FZ design does not move nor should anyone expect them to move like full floaters.