TCH Brake Issue - Page 2 - GreenHybrid

ToyotaGoblin · #11 (**permalink**) 06-21-2007, 10:50 AM

I'm looking into the TCH but I am a bit concerned about the brakes. When I test drove about a week ago I did notice that every stop felt like a jerk. The brakes were definately way too sensitive. With a 97 Camry I can drive it where the passengers might not notice when I'm accelerating or when I'm slowing down to stop.. but I have a feeling with the TCH it would never be that smooth.

Some of the things you guys say sound pretty dangerous too.. esp in situations where you want it to stop quickly and it doesn't. I'll keep watching this thread!

timohapi · #12 (**permalink**) 06-21-2007, 11:24 AM

My experience with Brakes is the same, as many of you, but remember that we have Brake assist system that controls all 4 wheels and grabs the road to keep car steady, that why you feel vibration and car is stiffer. This is normal operation. My previous car was Infiniti Fx and the brakes on my TCH are a lot better then on Infiniti.

mikieboyblue · #13 (**permalink**) 06-21-2007, 11:41 AM

Quote:

Originally Posted by ToyotaGoblin

Some of the things you guys say sound pretty dangerous too.. esp in situations where you want it to stop quickly and it doesn't. I'll keep watching this thread!

There are a few things going on here. First, the mechanical breaks do not kick-in (under normal load) until you hit 6mph or so. Because of that you will feel the breaking a bit more around that threshold. This would cause a jerking sensation. Also, when I test drove the TCH I to thought the breaks were super sensitive. I have since then got 110% used to them and I figured (at the time) it was because I was driving a POS with bad brakes before.

Also, I have not had it ever be a problem that effects the stopping ability. The car has never not stopped and in one situation where it was icy it stopped very well.

Quote:

Originally Posted by Ookpik

I had something similar happen the other day but I was driving for a while at low speeds through the neighborhood and came to a slow stop with little pressure on the brake and it felt like the ABS kicked in very hard. This was dry pavement,sunny day etc. Never happened again. Any thoughts?

I do not have it happen everyday but it is usually one of the first few stops of a trip. It doesn't have to be raining or wet outside and the pavement has not made a difference. I usually feel it out of one side. Most of the time I would say is it the passenger side but I have felt it on the driver front and back at least once.

I plan to take my TCH to the dealer for the first checkup and will ask about it but according to others on the forum what happens to me appears to be normal.

Mike

Ookpik · #14 (**permalink**) 06-21-2007, 01:38 PM

I do not have it happen everyday but it is usually one of the first few stops of a trip. It doesn't have to be raining or wet outside and the pavement has not made a difference. I usually feel it out of one side. Most of the time I would say is it the passenger side but I have felt it on the driver front and back at least once.

I plan to take my TCH to the dealer for the first checkup and will ask about it but according to others on the forum what happens to me appears to be normal.

Mike[/quote]

Thanks Keep us posted. Surprising this has not come up before!

spiff72 · #15 (**permalink**) 06-21-2007, 04:38 PM

I have noticed this issue during semi-aggressive braking on bumpy roads (Michigan is notorious for having ridiculously bumpy roads).

I think the explanations given here make perfect mechanical sense to me - both the ABS intervention due to wheel rotation variations, and the regenerative braking dropping out as the ABS intervenes seems like it would manifest itself in this way too...

gandyfire · #16 (**permalink**) 06-21-2007, 07:21 PM

You have to realize the braking functions are controlled by the ECU. In a standard vehicle, pushing on the brake pedal increases the force on the brake fluid and increases the braking force unless the ABS senses a skid.

On the TCH we have brake assist or ECB (electronically controlled brake system) which when pushing on the brake pedal the brake fluid pressure suggests to the ECU how we want to stop. If the ABS is activated the slip indicator light on the dash should light up momentarily according to the Chassis manual under Brakes. There is a pump motor to increase brake pedal pressure if indicated by the computer and sensors on all four wheel cylinders. There are three basic functioins, pressure increase, pressure hold and pressure decrease which all work in conjunction with the regenerative braking in addition to 4 speed sensors.

This can all be found on the Tundra Soultions web site. For a small annual fee of $20 all manuals includinig the chassis manual can be downloaded. I obtained and studied them while waiting two and a half months to get my TCH last July.

Hope this helps

rmorrow · #17 (**permalink**) 06-22-2007, 06:16 AM

Quote:

Originally Posted by ToyotaGoblin

I'm looking into the TCH but I am a bit concerned about the brakes. When I test drove about a week ago I did notice that every stop felt like a jerk. The brakes were definately way too sensitive. With a 97 Camry I can drive it where the passengers might not notice when I'm accelerating or when I'm slowing down to stop.. but I have a feeling with the TCH it would never be that smooth.

Some of the things you guys say sound pretty dangerous too.. esp in situations where you want it to stop quickly and it doesn't. I'll keep watching this thread!

My own experience has been exactly the opposite. Both my wife and I have remarked on how smoothly our TCH stops compared to most other cars we've been in.
Now, I haven't yet tried a really hard stop - in bumpy or any other conditions. I'll have to play with that a bit and see if that changes anything.

Droid13 · #18 (**permalink**) 06-22-2007, 07:58 PM

I think generally we are talking about different affects from the same cause. Regen braking giving way to mechanical braking (either from poor traction to allow ABS to function, or just because your speed as dropped below regen operating limits) which can result in either more or less braking effect. Why? Well affects of regen braking can be reasonably calculated by the car's computer and is for the most part probably very consistent. Problem with mechanical brakes is the computer has no idea what temp the brake pads or rotors are at, how damp the pads might be at the moment, condition of the pads, just been thru a cash wash, etc. It simply doesn't have the Enterprise's scanners to detect the exact condition of the brakes or what the road conditions are going to be 0.5 seconds in the future. When regen gives way to mechanical braking, the computer has to do a best guess at how to perform a transition and it's not going to be perfect everytime (but in reality, 99% of the time it is really good).

I am well familiar with the sudden extra stopping that happens just before coming to a stop, during the first 1 or 2 stops especially in the morning or after a rain (as the regen braking gives way to first time use of damp brakes) As has been said before, but for benefit of new comers this doesn't happen on a regular car because the brakes typically get applied sooner at higher speed where the affect is a lot less noticeable and the moisture is heated away a lot faster (ie throwing away perfectly good energy). It definitely can be annoying, but certainly not a safety hazard (unless you consider stopping 6 inches sooner than planned a safety issue). As it only happens the first time or two and only on certain days, doesn't bother me much.

I am also well familiar with the regen braking giving way and having braking force drop a bit (the rough road or some loose dirt on the road causing the need for ABS seems reasonable to me). This is probably a bit more annoying because for 0.1 seconds it feels like the brakes have given out. It's about the equivalent effect of 1.5 cups of coffee. Most people have a tendency to apply a bit more brakes when they feel less braking then desired and in the end the actual safety aspect is null (unless you have the opposite tendency to remove your foot from the brake if you feel less braking, maybe should not be driving if that was the case).

So yes, this is an annoying reality of this vehicle, but it actually doesn't happen very much (for me, 1% of the time) and the effects can vary from barely noticeable to quite noticeable when it does happen. It doesn't make me regret the car in the least. If you are shopping around, and are (or spouse is) a bit of a nervous driver or expect perfection in this area, this may be an issue for you. Something to think about...

REV800X · #19 (**permalink**) 06-22-2007, 09:16 PM

Quote:

Originally Posted by Droid13

I think generally we are talking about different affects from the same cause. Regen braking giving way to mechanical braking (either from poor traction to allow ABS to function, or just because your speed as dropped below regen operating limits) which can result in either more or less braking effect. Why? Well affects of regen braking can be reasonably calculated by the car's computer and is for the most part probably very consistent. Problem with mechanical brakes is the computer has no idea what temp the brake pads or rotors are at, how damp the pads might be at the moment, condition of the pads, just been thru a cash wash, etc. It simply doesn't have the Enterprise's scanners to detect the exact condition of the brakes or what the road conditions are going to be 0.5 seconds in the future. When regen gives way to mechanical braking, the computer has to do a best guess at how to perform a transition and it's not going to be perfect everytime (but in reality, 99% of the time it is really good).

I am well familiar with the sudden extra stopping that happens just before coming to a stop, during the first 1 or 2 stops especially in the morning or after a rain (as the regen braking gives way to first time use of damp brakes) As has been said before, but for benefit of new comers this doesn't happen on a regular car because the brakes typically get applied sooner at higher speed where the affect is a lot less noticeable and the moisture is heated away a lot faster (ie throwing away perfectly good energy). It definitely can be annoying, but certainly not a safety hazard (unless you consider stopping 6 inches sooner than planned a safety issue). As it only happens the first time or two and only on certain days, doesn't bother me much.

I am also well familiar with the regen braking giving way and having braking force drop a bit (the rough road or some loose dirt on the road causing the need for ABS seems reasonable to me). This is probably a bit more annoying because for 0.1 seconds it feels like the brakes have given out. It's about the equivalent effect of 1.5 cups of coffee. Most people have a tendency to apply a bit more brakes when they feel less braking then desired and in the end the actual safety aspect is null (unless you have the opposite tendency to remove your foot from the brake if you feel less braking, maybe should not be driving if that was the case).

So yes, this is an annoying reality of this vehicle, but it actually doesn't happen very much (for me, 1% of the time) and the effects can vary from barely noticeable to quite noticeable when it does happen. It doesn't make me regret the car in the least. If you are shopping around, and are (or spouse is) a bit of a nervous driver or expect perfection in this area, this may be an issue for you. Something to think about...

Wow, Your are very good for Toyota at damage control... Hard to believe my problem could eliciet this response...

SPL · #20 (**permalink**) 06-23-2007, 10:27 AM

I agree with timohapi that this is probably just the Brake Assist function, which initially thought that this was a "panic stop" and so boosted brake pressure, but revised its opinion when you eased off on the brake pedal after your initial fast brake application.

Stan