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Front Wheel Friction


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71 Front Wheel Friction.  Disk Brake, Magnum 500.

In attempts to find my 40 MPH and above vibration, I put the front end in the air and tried spinning the tires.

Right Front, maybe a half turn after a good push.  Left Front, Possibly 3/4 Turn with the same style good push.

That seems a little tight to me.  Unsure if I have the bearings torqued down too tight, or if the pads are dragging.  I have about 400 miles or less since restoration.  All Brake components were new.(Calipers/Pads)

What are your thoughts?

kcmash

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Disc brake pads always have some contact with the rotor, as they do not have springs to retract them. The spinning of the rotor as the car moves, rotor runout, and vibrations may cause the pads to retract slightly. Any rust on the rotors will make the front wheels more difficult to turn by hand. It is doubtful if you can spin them fast enough by hand to cause the pads to back off.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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I think the important points to not over-tighten the bearings on the disc brakes are steps 5 & 6. Tighten to 17-25 ft-lbs to seat the bearings, loosen and then re-tighten to 10-15 IN-LBS. I misread that the first time when I did my bearings.

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On 12/19/2020 at 1:36 PM, kcmash said:

71 Front Wheel Friction.  Disk Brake, Magnum 500.

In attempts to find my 40 MPH and above vibration, I put the front end in the air and tried spinning the tires.

Right Front, maybe a half turn after a good push.  Left Front, Possibly 3/4 Turn with the same style good push.

That seems a little tight to me.  Unsure if I have the bearings torqued down too tight, or if the pads are dragging.  I have about 400 miles or less since restoration.  All Brake components were new.(Calipers/Pads)

What are your thoughts?

kcmash

Is the vibration continuous above 40MPH? I've had a vibration between ~43 and ~49 MPH ever since I've owned the car. At about 50 MPH the ride pretty much smooths right out. I was thinking more tire balance or something rather than bearings or brakes. I did add front discs a couple of years ago but that didn't change anything as far as I can tell.

Mike

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Vibrations can be very difficult to resolve, due to all of the rotating masses in a car. Even if it is in a wheel/tire it may not be easy to find. When a tire is rolling on the pavement the dynamics of the tire mass changes due to the tread and sidewalls flexing, which a spin balancer cannot replicate. Vibration problems can also be caused by belt overlap or gaps which can be balanced out on a balancer, but show up as a vibration when the bad section impacts the road surface. Vibrations from other tires, the engine, torque converter, clutch assembly, driveline, bent axle, etc. can add to or cancel out a tire vibration, but will usually be cyclic as the rotating masses go in and out of sinc. Engine vibration is the easiest to rule out, place transmission in neutral and let the engine idle while coasting at the vibration speed.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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One thought just came to mind when I re-read the first line, Magnum 500's!! Then I remembered that I had the same sort of issue with the set of 500's that were on my car when I bought it. What I found was at some point, my guess was that some over zealous tire changer guy got slap happy with the IMPACT wrench and probably more than once. Out of the 4 wheels, 3 had to be scrapped because the lug holes were egg shaped and as 500's are lug-centric, if the holes are not round, the wheels will never likely run true and in balance. I had to buy a new set of wheels and I NEVER use any sort of impact wrench to tighten the nuts. I do however use my electric impact to run the nuts up snug, then torque in 2 steps with the wheels on the ground. Also, these wheels MUST be balanced on a lug centric adaptor and not all shops have those. Do not ever let someone tell you otherwise as happened to me, I just told the guy to go pound salt.

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Geoff.

 I learn something new every day!

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I think I found the problem.  Now to figure out a fix.

Note the chattered hot spots on the rotor.

20201222_095215.jpg

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If you grab the rotor firmly and try move it perpendicular to its normal rotation do you have any play?
Now with no callipers on, does the rotor spins freely without any noise?

I've got wheel bearing issue on my 91 t-bird years ago, and I recall you would certainly not only have vibs at certain speed but also friction noise while driving at any, you couldn't miss it.
I don't think it's your problem as you say both wheels are hard to turn by hand. Having 2 bearings going south at same time after so little driving would get you the most unlucky person award.

I was having similar probs on my 73 not a month ago and failed tech control for that. Both sides were really hard to turn by hand, where passenger side was tiny bits less affected.
In my case, the callipers pistons were not retracting enough and the bushings had turned to some sticky material. As the piston kits were here more expensive than new callipers by NPD, ordered new ones, new bushings and hardware (changed the flexible while at it)) and the bit more agressive pads that they offer. I've put +-300kms on it since then and prob is gone.

The blue marks you have tell that the contact of the pads is uneven, so while some foreign material may have come in between, that should not affect the other wheel.
You now need new pads on both sides anyway, but somehow I don't think that it's the main problem. I'd place the pistons as suspect number one.
 

Edited by Fabrice

73 modified Grande 351C. (Finally back on the road woohoo!) 

71 429CJ. ( In progress )

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My eyes are getting bad, but not bad enough to miss that!

I bet that made for some ratty feeling brakes...

I bet those brakes squealed like a mouse...

What’s that burning smell...

 

kcmash

 

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