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I am trying to diagnose why a 2009 Toyota Venza's parking brake is not holding the vehicle securely. On any incline the vehicle will slide in N, never mind D or R.

After taking the rotor off, I observed that the shoes barely move when the parking brake is applied. Short videos of engaging/disengaging parking brake with wheel and rotor removed: https://imgur.com/a/YcCgV76

Is this the expected range of motion?

The brake cables where changed (one OEM, one non-OEM), as were the brake shoes and most of the parking brake hardware, and later the rotor/disc/drums as well. It was adjusted several times by multiple mechanics. The parking brake pedal has tension as soon as it starts moving and feels quite firm when fully pressed to 6-8 clicks and even before.

EDIT: After fully taking apart the parking brakes to inspect, clean, lubricate, and reassemble, I noticed:

  • The non-OEM cable might be slightly shorter than the OEM, because when applying the parking brake with the disc/rotor off, the parking brake lever reaches the metal stop on the dust shield, indicating full travel, and then jumps sideways past the stop. That is the loud "click" sound in the videos above. When it is inside the rotor it might not be able to make that lateral motion. The OEM cable on the other side brings the lever to the stop perfectly and no more. I wonder if this imbalance can cause some problem in the force applied or if the equalizer can manage this. Also, the non-OEM cable is clearly of lower quality: the head is smaller, the cable is thinner, and a few strands are already broken, probably from when a technician was trying to install it. It's a pain to work with compared to the OEM cable.

  • The parking brake's stopping power is not the same in the forward and reverse directions. With the parking brake engaged and the vehicle jacked up, I can't manually turn the wheel forward, but with moderate effort can turn the wheel in reverse.

  • The brake shoes do not appear to be making full contact. There are patches where some wear from contact is visible (shiny, metallic appearance), and the rest of the area has a matte dusty look. When I put the shoes inside the drum to check shape and tolerances, there seemed to be very slight imperfections which allowed me to rock the shoe to make contact with different sections. Very slight, but perceptible. Perhaps bedding in the shoes will wear them to match the drum and make full contact. I wonder if that would provide enough friction to hold the vehicle. The service manual includes a bedding procedure (step 24), and I highly doubt it has been done.

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  • Has anyone looked at the diameter of the parking brake drum to see if it is within spec? Or that the shoes are actually going out enough (even fully adjusted) to contact the drum surface? Were the rotors replaced near the time you noticed the parking brakes weren't working? Aug 13 '21 at 13:58
  • @Pᴀᴜʟsᴛᴇʀ2 The rotors were recently replaced as part of trying to fix the parking brakes. The previous rotors' parking brake drum diameter was 1mm over spec, but the current ones are new. How can the shoes' travel be adjusted? It appears not to be moving much/enough, but I don't know what the correct travel should be.
    – adatum
    Aug 13 '21 at 14:27
  • Have you actually measured the new rotors? It could be the wrong ones were installed or they weren't in spec to begin with. Aug 13 '21 at 14:29
  • @Pᴀᴜʟsᴛᴇʀ2 Good point. Yes, with a ruler (I don't have 12 inch calipers unfortunately) I checked the rotor is at 190mm which is the new diameter specification according to the service manual (new 190mm, maximum 191mm).
    – adatum
    Aug 13 '21 at 14:31
  • So the parking brake shoes act on the 190mm?
    – Solar Mike
    Aug 13 '21 at 17:00
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Several things can limit the shoe travel. Make sure all the cables are fully extended. Don't rely on the spring to move the cable, grab it with pliers and yank on it. If it moves any distance the cable is binding in the sleeve. Another issue is the top spreader bar being worn at the shoe contact points. This causes the shoes to seat to far from the drum. Low quality shoes can also cause issues. They can be lined with material that is too thin or not evenly round causing less than full contact. Some manufacturers did a poor job of designing early versions of disc brake parking brakes. Hence the change from "Emergency Brake" to "Parking Brake". Some models are marginal at best. Anything less than perfect, results in less-than-ideal performance. My state requires the brake to hold to 1200 rpm. My early 2000's Chevy Silverado with all new parts would roll at 1250 RPM. This may not be your issue but the days of the Parking Brake keeping you from driving away are long gone.

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  • Good tips, I'll check next time. If the cables are not fully extended, wouldn't that cause brake drag and not poor parking brake force? The "spreader bars"/shoe struts look the same as the original that I still have, but I'll measure carefully next time. The shoes definitely don't make full, even contact, and while bedding them in helped a bit, it's still not enough. I'd be happy if the parking brakes hold the parked vehicle securely on an incline. At 1200 RPM right now the parking brakes have zero chance of having any effect. It's a coin toss if it can even prevent rolling at idle.
    – adatum
    Jan 13 at 0:15
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http://www.tovenza.com/parking_brake_system-659.html

https://www.toyotanation.com/threads/is-2009-venza-parking-brake-adjustable.1008002/

Your rear brakes are drum style using brake shoes. Apparently the repair shop doesn't know how to adjust the star wheel that's adjusted after repairs are made then follow up to check on park brake operation. Perhaps the two links above can help you understand drum brakes and parking brake adjustment that go hand in hand as the rear drum brakes are the parking brakes. Many without knowledge of drum brakes are easily confused by the numerous parts used but forget or ignore drum brakes were the first brakes used since 1900 before disc brakes improved on braking in the 60's. When rear drum brake shoes are adjusted correctly by a competent mechanic or diyer, brake shoes drag slightly on brake drums. Applying the parking brake lever or pedal simply engages either a cam or other lever to force brake shoes against drum. When adjusted correctly, braking is better and engaging the parking brake should force the brake shoes against the drum to hold a vehicle from moving. Perhaps using the suggested links to Toyota forums can help you or search for other Toyota Venza forums for help. As a diyer, I'm familiar with drum brakes and maintained them in the past. As safety items, brake service isn't for anyone unfamiliar with servicing drum or disc brakes. I'm not surprised that your repair shop isn't capable of performing a complete rear drum brake service including park brake operation. No hydraulics are involved as this is all mechanical.

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  • Yes I am aware of the star wheel, which is what the mechanics used for adjustment. Unfortunately, even expanding the shoes to the point where the parking brakes started clacking loudly on the highway was not sufficient have the parking brakes hold the vehicle. My latest thought is that the shoes need to be bedded in, since it appears only small patches are making contact with the drum.
    – adatum
    Aug 14 '21 at 3:25
  • New drums and brake shoes should be matching their contours with only initial star wheel adjustment. Without being there in person, it's difficult to determine why these drum bakes aren't able to serve as parking brakes. This is the responsibility of the repair shop since they did the work. Loud noises from these brakes seems to be something this repair shop overlooked. When new, drums may require machining to remove minor imperfections to mate to new brake shoes for minimal break-in period like a new car needs breaking in on new brakes and engine.
    – F Dryer
    Aug 14 '21 at 20:53
  • Wouldn't the drums already be machines, and the shoes be expected to have minor imperfections? The service manual's installation instructions include a bedding procedure (step 24) which I doubt has been done: tovenza.com/reassembly-643.html Btw, I think the star wheel is installed backwards, not that it should matter. Also, most of the work was done by a Toyota dealer. Another independent garage that tried adjusting also had no luck.
    – adatum
    Aug 15 '21 at 16:03
  • Star wheels, threaded for left and right hand threads work with the brake pawl. Anyone not knowing this should not be working on brake systems. This is basic knowledge of drum brakes. The incorrect star wheel on the wrong side simply screws by pawl operation, retracting brake shoes. This has the effect of more brake pedal travel to move retracted brake shoes and disable the parking brake. Experts in brake shops determine whether or not a new drum is warped, requiring machining or not. Experts, not diyers without dial calipers or more than average knowledge of brake systems.
    – F Dryer
    Aug 15 '21 at 20:06
  • Sorry, I don't understand your comment. What do you mean by the brake pawl? The star wheel (parking brake adjustment) just looks like a double sided-fork with a (regular, not reverse) threaded section to set the distance between the forks, which is effectively "pre-tensioning" the parking brake by adjusting the resting distance between the shoes and drum. The threading direction shouldn't make a difference. Am I missing something? Also, I updated the OP/question with pictures of the brake shoes. Does the contact patch pattern tell you anything? Would it benefit from bedding in?
    – adatum
    Aug 16 '21 at 1:43

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