Brake THUMP

Handling, suspension, and brake tuning discussions
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ZZvroom
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Brake THUMP

Post by ZZvroom » Fri Dec 20, 2019 7:52 pm

2003 GT

So we pulled the rear rotors to look at/adjust the parking brakes.
We did so, and tightened the cable as well.

factoid: From the rear:
CW on driver's side to tighten
CCW on passenger's side...

But now when you apply the parking brake there is a loud THUMP from the RR wheel area.
Next application is quiet, unless the car moved; if it has, THUMP.

We went back on the lift, pulled the wheel off and everything looked OK except a slight amount of play between the rotor and hub; the lug holes are enough larger so there is say 0.125" of play, until of course you remount and torque the wheels again.

We're mystified as to the cause.
No noise with the service brake.

Suggestions?

zbyers
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Re: Brake THUMP

Post by zbyers » Mon Dec 23, 2019 4:14 am

I will ask a few stupid questions, because I've seen it happen with my brother lol.

Are the caliper bolts torqued down?

Are you missing any of the pins/springs that hold the emergency brake shoes on?

How are the rear pads in the caliper?

There shouldn't be any thumping noise, so I would just double check all of the work you did to ensure that nothing was missed. :D
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joatmon
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Re: Brake THUMP

Post by joatmon » Mon Dec 23, 2019 4:55 pm

If the thump happens when you apply the parking brake after it's been driven, can you get someone to pull the ebrake while you look around the suspect wheel to see/hear better where the sound is coming from?

I assume the thump happens when you apply the parking brake in a normal (non-violent) manner.

I can think of two possible causes, won't hazard a guess how probably either one is though. The tough part is figuring out what would cause something to suddenly let go with enough suddenness to cause a thump.

One is that the brake cable gets snagged on something, and when you put tension on it, it snaps free, like plucking a guitar string. Seems like you would have noticed such a thing though, and you said you tightened the cable so I seriously doubt there's enough slack to get blown around by wind to cause a snag. But in the hypothetical world, I guess it could happen.

... nah...

The other is that since you mentioned play between the rotor and hub, and space around the lug nuts, the rotor would slop around if it wasn't clamped in place by the wheel. Maybe the parking brake applies pressure on the hub in a way that would tend to push it off center. After driving, the rotor ends up in a different position than before you drove, and applying the parking brake pushes the rotor in a different direction, and it eventually overcomes the clamping of the wheel and shifts abruptly. I only ever had a base Vibe, (rear drums) but I've replaced front Vibe rotors several times, on those I pretty much had to beat on the old rotors to remove them because they were such a tight fit (and rust welded too). Without loosening any lug nuts or actually driving, try applying the parking brake, then raise that suspect wheel a bit, rotate the wheel 180 degrees, let it back down and try the brake again.

but that's all just guessing at what might be able to cause it

jolt
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Re: Brake THUMP

Post by jolt » Tue Dec 24, 2019 1:33 am

Cables do wear out and need to be replaced when bad. Jack the rear wheels off the ground, spin each tire by hand. They should spin freely. Next apply the parking brake and try to spin each wheel, they should not spin. Release the parking brake and try to spin each wheel by hand, they should spin freely. If a wheel does not spin freely after the parking brake was released, you have the parking brakes hanging up. It would most likely being a cable.

Do the wheels spin freely by hand after the parking brake is released? Did you lube the parking brake cables? Some cables are lined inside so that they do not rust and stick. The lining (plastic) does wear through over time and will bunch up inside the cable causing the cable to hangup and not release the brake properly. The thump you hear could be caused by the brakes popping loose when the tire is turned as joatmon referred too. If it is a lined cable that is sticking then the only repair is to replace the cable.

This would not be related to your other post that asked a question about the caliper sleeves?

ZZvroom
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Re: Brake THUMP

Post by ZZvroom » Wed Dec 25, 2019 12:49 pm

Shoes look fine; I'd bought a new set but they are no thicker.
We looked at all the parts before adjusting them and tightning the cable.

The mystery part is:
  • It thumps only with the parking brake.
  • It thumps again only after the wheel is rotated.
We'll be back on the lift looking at it again after the bolts & sleeves for the other side's caliper arrive from Rock Auto.

ZZvroom
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Re: Brake THUMP

Post by ZZvroom » Thu Jan 02, 2020 8:57 pm

Looked again today.

The rotor holes are a bit oversize. It does appear the cause is the rotor slipping between the wheel and hub.

We think the parking brake is recentering the rotor on the hub.
If the wheel is stationary, you hear that one thump.
If it's rotating, you hear a thump for each application.

At the moment, it seems like our approach is to not worry about it; while thinking of turning some spacers to go between the studs and the rotor.

I'm more concerned about the rust deterioration of the backplates. I understand they are made from unobtanium.

zbyers
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Re: Brake THUMP

Post by zbyers » Fri Jan 03, 2020 3:41 am

ZZvroom wrote:
Thu Jan 02, 2020 8:57 pm
I'm more concerned about the rust deterioration of the backplates. I understand they are made from unobtanium.
If you know anyone in Canada, have them buy the backing plates/dust shields from Toyota of Canada. They are a fraction of the price compared to the US.
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ZZvroom
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Re: Brake THUMP

Post by ZZvroom » Fri Jan 03, 2020 8:23 am

Tell me more! I do know someone who can help in that regard.
Part#???

zbyers
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Re: Brake THUMP

Post by zbyers » Fri Jan 03, 2020 8:44 am

GT/XRS Rear Left Backing Plate/Dust Shield: Toyota 46504-20070

https://parts.conicellitoyotaofconshoho ... dhcw%3D%3D

GT/XRS Rear Right Backing Plate/Dust Shield: Toyota 46503-20070

https://parts.conicellitoyotaofconshoho ... dhcw%3D%3D

***the 5th digit is the change in the P/N for the different sides number***
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zbyers
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Re: Brake THUMP

Post by zbyers » Fri Jan 03, 2020 8:47 am

At https://parts.scarboroughtoyota.ca/ the cost is $80 CAD ($60 USD). Even if you had to pay shipping, you're already $200 cheaper than US pricing.
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ZZvroom
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Re: Parking Brake THUMP

Post by ZZvroom » Wed Jun 17, 2020 4:26 pm

My saga continues. We tightened the cable more. (PITA since you must pull the console..)

Now get tight cable when brake handle is pulled hard.

But totally ineffective, car still rolls away.

We'll pull the rear wheels and disk/drums again, and keep head-scratching.

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joatmon
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Re: Brake THUMP

Post by joatmon » Wed Jun 17, 2020 4:48 pm

well that sucks. I almost never use the parking brake in an auto tranny car, use it every time in a manual. Kinda important.

the smartass in me wants to say you're not supposed to lube the brake shoes, but you don't need that kind of stupid joke

All I can think of is to pull a wheel and verify that pulling the brake handle results in a desired amount of brake shoe movement.

Was it grabbing better back in December when you first went to adjust the cable?

zbyers
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Re: Brake THUMP

Post by zbyers » Thu Jun 18, 2020 6:04 am

Perhaps the parking brake cables are stretched beyond use?
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ZZvroom
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Re: Brake THUMP

Post by ZZvroom » Thu Jun 18, 2020 8:51 am

Drums are a PITA since you must have the drum on to test, and then you can't see diddly.

If the cable has stretched, how'd we get it tight? [Strummed the cable just behind the parking brake level; it was tight...]

andrewclaus
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Re: Brake THUMP

Post by andrewclaus » Thu Jun 18, 2020 7:58 pm

I don't think anybody's asked yet if the brake shoes are adjusted correctly. The star wheels should be turned until the shoes are just touching the drums as you turn them by hand. Then the cable should be adjusted so the brakes are firmly on with five or six clicks of the lever.

jolt
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Re: Brake THUMP

Post by jolt » Thu Jun 18, 2020 10:27 pm

You need to post a picture of the shoes assembled on the backing plate with the drum removed so we can see if you have all the parts and that the parts are in the proper locations.

Have the drums been turned? What is the inside diameter of the drums? Do you the proper rear rotors on the cars? It should not be this difficult unless something is missing or not the right part.

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