[Shotimes] Vibration or picky...again

[cmichaelo@optonline.net]

Leigh,

The 3 sets of wheels are all different rims and different tires.

The rotors are 12.5" Baers. They are not warped.  No noise or vibration during any type of braking.

Did the car ever hit a curb?  No, but it did hit a pothole once which caused a bent inner rim on the front right side.  The rim was also warped resulting in a lateral runout. I wasn't driving the car at the time of the accident, so I'm not exactly sure what happened.

But the fact that the rim was warped means that there must have been a significant lateral force at the time of the accident, which, I suppose, could furthermore have bent the hub just enough to cause a problem.  Though, after the rim was fixed (at the wheel collision center in PA), there was no vibration whatsoever.

If the rotor seat properly on the hub, you ask.  I think so. Though there is room for the rotor to rotate a bit. Radially, it hardly moves.

What do you mean with a belt shifting in the tire?  Do you mean the tire slides on the rim, e.g. during heavy braking?


Michael
94MTX,green,BOS+,Koni/Intrax,Baer,Corbeau
SHO items for sale: http://hometown.aol.com/cmichaelo/for_sale.html

----- Original Message -----
From: Leigh Smith <leighsm@comcast.net>
Date: Wednesday, February 16, 2005 4:47 pm
Subject: Re: RE: [Shotimes] Vibration or picky...again

> Michael:
> ..
> 3 Sets of wheels = not it
> Q: Tires ? same set? or different ones?
> Max Lateral tire runout spec (Ford) = 0.080 in. (1/16 in) (shoot 
> for half)
> Max Lateral Wheel runout spec = 0.080 in.(ditto)
> Max Lateral rotor runout spec = 0.003 in
> Max Lateral hub face runout spec = 0.002 in.
> ..
> If the tires were always the same, I would check carefully for a 
> shiftedbelt in the tire, which seems likely since you said it goes 
> away when you
> put them on the back. These are pretty common.
> ..
> Otherwise, Based on the specs and what you said, I'd check for hub 
> or rotor
> issues. Warped rotors are very common, but a vibration in a 
> staight line
> during cruise? That doesn't sound like a warped rotor symptom. A 
> bent hub
> could cause all the above.....but has the car ever hit a curb? 
> Does the
> rotor physically seat properly on the hub? I have heard of some 
> issues with
> certain rotors, but don't you have Baer?
> ..
> Good luck & let us know what you find. See below
> Leigh
> 
> > I've had the vibration problem up front for over 3 years now 
> with 3
> different sets of wheels.  It basically started, around the time 
> that I
> changed rotors up front.
> >
> > Wrt the radial runout of but the hub centerbore and the rotor, 
> it is less
> than 0.015".  The rotor though has to be mounted carefully to 
> achieve this.
> If I do it sloppyly, the radial runout can be as high as 0.025" 
> (which is
> probably still acceptable, no?)
> >
> NO - that sounds too high - see above
> >
> >  Radially everything looks good.  Laterally, there is a slight 
> but clearly
> visible wobble in both rim and tire.  I'll measure this weekend.
> >
> Anything more than 1/16 in could mean a shifted belt - but only if 
> the wheel
> is straight - I recently had one with 3/8 in wobble & a mean 
> vibration - but
> if your rim is wobbling also could mean a bent rim, or deeper problem
> >
> > Another thing that tells me that the wobble is most likely in the
> hub/rotor is that when spinning the wheel slowly by hand, the 
> rotor scrapes
> against the brake pad a certain spot on every revolution. 
> Sometimes, though,
> it's only on every second revolution (go figure???).
> This may mean a rotor width variation, which should also be 
> measured -
> and/or rotor resurfaced - but I don't see how that would cause a 
> vibration>