Shimmy on the Hiwy

Joined
May 25, 2005
Messages
15,636
Location
ROCHESTER, NY
2015 Altima in my signature(~60K miles).

My car tracks nice and straight & smooth at all HIWY speeds just like new. So, I know my BRAND NEW tires are in good balance and front end is sound & aligned(checked).

However, I do have a slight pulsation while braking(which I've known) and I will in fact be changing the rotors in a few months.

Since the rotors aren't too awful bad yet, I thought I'd remove them(this warm day) and clean'em up, lube the sliders and bleed the system. Doing this often removes the pulsation(in which it did this time too)...probably for those few months till I order new rotors.

HOWEVER! I have NOW created a shimmy at those HIWY speeds(various speeds) as if there is a tire out of balance. I went back through my work and removed & reinstalled everything that I had done earlier. I also made sure all mating surfaces are good & clean(Rotors to Hubs, Wheels to Rotors) and everything is torqued properly.... You know what I mean?

Well, this has helped with the shimmy somewhat but, it didn't get rid of it completely.

*WHAT DID I DO, WHAT IS GOING ON?
 
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Rotate the tires front-to-back?
How worn is the tire tread?
Also, if Rochester roads are like Detroit area potholes, it doesn't take much to throw a curve in the vehicle alignment. Lastly, I keep my tire pressure 5-10 lbs above what's written on the door panels for the vehicle. Both of my Korean models are new and they carry 10lbs more than what's written/recommended. I can deal with a little firmer ride. I consider it a trade-off against increased chance of steel wheel damage and soft tire steel belt damage.

We have the worst roads, of any major travel route-areas in the USA.
 
First question: are all the surfaces of the hub to rotor and wheel to rotor clean? We're in the salt belt too and see a lot of corrosion especially on the back of the wheel mount that can do odd things.

My suggestion is change the rotors and pads out now and see what changes. The brake pulsation should go away and if the shake while driving persists then you know it's a tire or rotating component issue. If new brake parts don't change the brake pulsation then what I'd do is run the on car brake lathe to eliminate any hub/rotor variation and check the tire balance (preferably roadforced) to eliminate any tire issue.
 
Tires are brand new and have had them for 2 + weeks now. The tires have been fine, as I did test them for balance at several HIWY speeds upto ~80 mph after installing them. Only since messing with the brakes has this shimmy occured.

It is possible that due to not marking the rotors & hubs and putting the rotors back on exactly how they were removed(over the same lugs) that I may not have the exact mating surface(s)???

ATMOF, I had the car on the HIWY earlier that same day(prior to messing with the brakes) and the tire balance at 70+ mph was perfect.

Only after scuffing up & cleaning up the rotors and taking a test drive to see if the brake pulsation was still present, I NOW have a shimmy.

As mentioned earlier, I came home from said test drive, removed & reinstalled my previous work, took another test drive and it was a little better but, noticeably. However the shimmy is still present
 
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The rotors are running out . That's why vehicles with disc brakes should have the lug nuts torqued with a torque wrench.
 
Originally Posted by KGMtech
Any chunks of rotor rust stuck in the rotor vanes?

Oh yeah! Lots of rust in the vanes but only a tiny bit under the rotor hubs. The wheel hubs themselves are perfect. I greased them, where the rotors seat over the hubs bach when the car was new.

Originally Posted by tig1
The rotors are running out . That's why vehicles with disc brakes should have the lug nuts torqued with a torque wrench.

I only use a torque wrench on my lug nuts(80 ft.lbs). Always have!
smile.gif
 
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We had this issue on our Liberty. Tried several different things but wound up the front rotors were severely warped and would shimmy slightly above 50mph and severely under braking. New rotors, pads, and a caliper and all is smooth. Rust buildup prevented the pads from retracting and totally screwed everything up. All the new parts got ant-seize or brake lube to prevent it in the future.
 
Originally Posted by SubLGT
Measure rotor axial runout with a dial gage. Typically it should be under .002 inch.

Thank you but these rotors are going in the trash bin. If the rotors were newer I would check thecrunout. But, they're the OE rotors, rusty, not worth measuring nor turning and the pulse when I brake.

It's the wheel shimmy that I suddenly got while driving on the HIWY after tinkering with the brakes as I was trying to reduce this brake pulsation.

Originally Posted by Delta
We had this issue on our Liberty. Tried several different things but wound up the front rotors were severely warped and would shimmy slightly above 50mph and severely under braking. New rotors, pads, and a caliper and all is smooth. Rust buildup prevented the pads from retracting and totally screwed everything up. All the new parts got ant-seize or brake lube to prevent it in the future.

I think this is my only resolution.
 
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Make sure you are not dealing with a bad suspension bushing, ball joint, steering end link or something similar. I chased a similar problem for months on a SUV, only to find it was a bad bushing on the front lower a-arm.
 
Originally Posted by silveravant
Any chance you knocked a balance weight off when removing/replacing the wheel?

Nope, I looked at the wheels & the driveway. Although they're stick on weights, they're all good & clean. Nothing missing.

Originally Posted by rubberchicken
Make sure you are not dealing with a bad suspension bushing, ball joint, steering end link or something similar. I chased a similar problem for months on a SUV, only to find it was a bad bushing on the front lower a-arm.


Thanks, I checked. Everything is tight.

I think I have a little brake work to do.
 
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Update:

Tires(Pirelli Cint P7 A/S +) were purchased from the TireRack. Had a reputible local installer mount & balance them.
Today, these tires have less than 400 miles on them.

So, I brought the tires/wheels back to the installer yesterday to check for imbalance and sure enough, all 4 tires were out of balance(they said) on the insides. I would say that it was an installers issue. The checked the front end parts and all is tight.

The Tech also said that one tires has a high spot that they noticed while spinning. I'll call the TireRack today and see what they say.
 
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