Brake issue after front wheel bearing replacement.

[virginiasand100]

Brake issue after front wheel bearing replacement. We have a 2019 (200 Series) and had to have new front wheel bearings at 77K. I found that very odd, however I had the LC back to the dealer two more times after the repair due to the drastic change in brake pressure and brake pedal travel (increase) to stop the vehicle. Before the wheel bearing job, and since the vehicle was new, the brakes were sensitive. Now, my wife and I have had few close calls with a lack of response when stopping. Brakes feel spongy as well. The Toyota dealer does not seem to think anything is wrong but clearly something is not right. Any thoughts? Is something else going on?

 

[doru]

Hubs themselves have nothing to do with brakes.
Replacing the hubs should not have affected the brakes, but we do not know what the dealer has actually done.
The usual causes of your issues are air in the system and/or pads contamination. Assuming the old parts were reused.

 

[TeCKis300]

Brake issue after front wheel bearing replacement. We have a 2019 (200 Series) and had to have new front wheel bearings at 77K. I found that very odd, however I had the LC back to the dealer two more times after the repair due to the drastic change in brake pressure and brake pedal travel (increase) to stop the vehicle. Before the wheel bearing job, and since the vehicle was new, the brakes were sensitive. Now, my wife and I have had few close calls with a lack of response when stopping. Brakes feel spongy as well. The Toyota dealer does not seem to think anything is wrong but clearly something is not right. Any thoughts? Is something else going on?

Very possible they did not preload the hub bearing properly or something is going on with the hub assembly.

What it sounds like you're experiencing is brake pad knock back. Basically, due to play in the bearing/hub, it's allowing the brake rotor to flex/runout (especially with turns) which pushes the brake pad and brake piston away from the rotor. When you press the brake pedal, it's using some travel to bring the pads back to the rotor before applying friction.

Is there a difference in brake feel/travel when applying the brakes back to back. Versus after some maneuvering and turns?

 

[Sandroad]

It’s extremely unlikely both (or even one) front wheel bearings were bad at that year and miles. What were the symptoms that led to that diagnosis? Maybe there is a clue to the brake issue?

I wonder if the tech fully removed the calipers instead of just hanging them up out of the way? If so, a full brake bleeding is needed and would fix the soft pedal. It’s also possible some very greasy hands reinstalled the rotors and everything is contaminated. Anyway, between bleeding, cleaning, and bearing adjustment check, I bet the brakes will end up ok.

 

[bloc]

asically, due to play in the bearing/hub, it's allowing the brake rotor to flex/runout (especially with turns) which pushes the brake pad and brake piston away from the rotor. When you press the brake pedal, it's using some travel to bring the pads back to the rotor before applying friction.

This would be my suspicion.

 

[virginiasand100]

Very possible they did not preload the hub bearing properly or something is going on with the hub assembly.

What it sounds like you're experiencing is brake pad knock back. Basically, due to play in the bearing/hub, it's allowing the brake rotor to flex/runout (especially with turns) which pushes the brake pad and brake piston away from the rotor. When you press the brake pedal, it's using some travel to bring the pads back to the rotor before applying friction.

Is there a difference in brake feel/travel when applying the brakes back to back. Versus after some maneuvering and turns?

You got it. I took it to another dealer and after I told them of your possible diagnosis they confirmed you are correct...but only after looking at me as if I were crazy and hours of diagnostics. They had to redo the job from the other dealer on one of the bearings and that fixed the brake pedal issue. Thank you for your help!!

 

[TeCKis300]

You got it. I took it to another dealer and after I told them of your possible diagnosis they confirmed you are correct...but only after looking at me as if I were crazy and hours of diagnostics. They had to redo the job from the other dealer on one of the bearings and that fixed the brake pedal issue. Thank you for your help!!

Great to hear you're back to enjoying the rig!

 

[mark71]

Very possible they did not preload the hub bearing properly or something is going on with the hub assembly.

What it sounds like you're experiencing is brake pad knock back. Basically, due to play in the bearing/hub, it's allowing the brake rotor to flex/runout (especially with turns) which pushes the brake pad and brake piston away from the rotor. When you press the brake pedal, it's using some travel to bring the pads back to the rotor before applying friction.

Is there a difference in brake feel/travel when applying the brakes back to back. Versus after some maneuvering and turns?

What does it mean to “preload the hub”? Torque it down, back it off, and then torque to spec?

Replacing my own hubs soon, so very timely thread!

 

[nwfl4runner]

What does it mean to “preload the hub”? Torque it down, back it off, and then torque to spec?

Replacing my own hubs soon, so very timely thread!

Yup -
148 tighten
Loosen
250 tighten

 

[GrouchyTech]

Yup -
148 tighten
Loosen
250 tighten

The 200 does not need to have the axle nut preload set. The 100 and earlier, yes.

 

[nwfl4runner]

The 200 does not need to have the axle nut preload set. The 100 and earlier, yes.

I thought FSM called for that sequence? At least on my LX it does

 

[GrouchyTech]

I thought FSM called for that sequence? At least on my LX it does

Yes, does call for 148, then back it off, and then 251. I think that is mainly to draw and set the CV stub.

But in practice—

 

[nwfl4runner]

Yes, does call for 148, then back it off, and then 251. I think that is mainly to draw and set the CV stub.

But in practice—

Six ugga duggas

 

[GrouchyTech]

Six ugga duggas

My Milwaukee goes clack clack clack. Not nearly as satisfying as a pneumatic ugga dugga.

I just run those unit hub axle nuts in with power setting #1 and then put a torque wrench on it.

 

[TeCKis300]

What does it mean to “preload the hub”? Torque it down, back it off, and then torque to spec?

Replacing my own hubs soon, so very timely thread!

The 200-series uses a unit bearing. Should be much harder to screw up versus older style taper bearings (a la 100-series). The CV spindle nut on the 200-series probably still serves some pre-load function at 251 lb-ft. The older LC100 bearings was only 50 lb-ft IIRC.

For modern sports cars that use huge pizza sized rotors, having enough hub stiffness can be a challenge. That's where I'm familiar with pad knockback, when combined with grippy rubber on road-courses. Fortunately I've not experienced any of it on the 200-series even with large 37 tires, overlanding weight, and hard mountain driving.

 

[GrouchyTech]

The pad knockback is a thing, and it reminds me of some of the strange approaches to diagnosing a problem. I experienced a brake repair problem when I was first starting out that I always thought was interesting. I machined a pair of front brake rotors on a Corolla or something and forgot to do a finish/slow cut. So I ended up with something like a vinyl record— basically a rotor with a threaded face.

When I test drove the car, I kept hearing this rapid clackclackclack sound. It turns out the “threaded” rotor face would rapidly move the pad in the caliper bracket, which made a corresponding clacking sound.

 

[mark71]

251 ft-lbs? And I thought the LCA bolts were tight! But at least these are in a better location for garage mechanics without a lift to torque down.

Pad knockback…learned something new, thanks guys.

Love this forum!

 

[TeCKis300]

251 ft-lbs? And I thought the LCA bolts were tight! But at least these are in a better location for garage mechanics without a lift to torque down.

Pad knockback…learned something new, thanks guys.

Love this forum

340 lb ft in the car half the size for the 200 series. That one put up a fight untorqing.

 

[bloc]

340 lb ft in the car half the size for the 200 series. That one put up a fight untorqing.

View attachment 4180088

I had what I assume was the same jack that eventually crapped out.. but kept the handle for the exact same purpose.

 

[linuxgod]

I suspect it's less a function of preloading the nut at 148, and then loosening and retorquing but far more about getting to the actual torque spec. My gut says the first shop just hit it with the air gun, which probably torqued it to ~100-120# like they would on a lug nut and then called it a day.

FWIW I had the same issue (due to CV re-booting) and despite the shop claiming they torqued it correctly I was getting the same brake issue the first press after turning. Too many mechanics skip the torque wrench or specs and just go by feel...