Big Rear Brakes? 2012 Jetta

[Mongler98]

I want to know how you're not braking for corners on the track. 'cause I barrel toward the corner and brake hard in a straight line right before I turn in. Sometimes, I'll brake late and still be braking on the turn in, which is when I risk losing the rear end, unless I have the portioning valve removed/blocked.

I dont waste my time with track. It's boring and the same set of turns every time. Fun yes. Boring yes. A high demand on cars wear and tear yes.
Thus why I only autocross and some times I track cross.
I brake as I would need to but going a max of 45 and some times 60.... you dont need brakes to be intensely hardcore.
Most of the time I'm carrying my speed into he next turn. Your track events can send you into a wall or worse. I am not committed enough to full send like a pro.
So have fun with a decks worth of lumber going 130 mph around a track with your insane brake upgrade.

 

[Cephyr13]

I dont waste my time with track. It's boring and the same set of turns every time. Fun yes. Boring yes. A high demand on cars wear and tear yes.
Thus why I only autocross and some times I track cross.
I brake as I would need to but going a max of 45 and some times 60.... you dont need brakes to be intensely hardcore.
Most of the time I'm carrying my speed into he next turn. Your track events can send you into a wall or worse. I am not committed enough to full send like a pro.
So have fun with a decks worth of lumber going 130 mph around a track with your insane brake upgrade.

No, steel hitches, not decks of lumber. And like I said, the M3 is my track car. The Jetta is my work car.

I don't autocross anymore. Takes way too long for very few runs and you have to work corners. It's cheap, but not really worth it. Once I started running on tracks, I never went back to autocross. Well, I take that back--I tried it again years later, but the SHO was set up for the track, not autocross. I either needed a featherweight FWD car or a RWD at the time. Didn't have the E46 yet.

 

[Paulman]

I replaced my brakes with a Zimmerman/Akebono setup.
And next, I had my TDI Guru replace the stock suspension with a Bilstein B4 on all the corners with all new mounts and hardware.
This is a magical combination.
Face it, you CAN make a MK6 VW feel like a German car again.

 

[turbobrick240]

Replacing the worn suspension (springs, shocks, struts, mounts) and brakes added more fahrvergnugen to my current mk6 than all of the more costly power enhancements I'd made to my previous mk6.

 

[Cephyr13]

I replaced my brakes with a Zimmerman/Akebono setup.
And next, I had my TDI Guru replace the stock suspension with a Bilstein B4 on all the corners with all new mounts and hardware.
This is a magical combination.
Face it, you CAN make a MK6 VW feel like a German car again.

I have progressive, twin tube, race suspension on my MK6. Helped a ton. That's the first thing I do to all of my cars.

 

[Cephyr13]

Replacing the worn suspension (springs, shocks, struts, mounts) and brakes added more fahrvergnugen to my current mk6 than all of the more costly power enhancements I'd made to my previous mk6.

See above reply.

 

[Reinout]

I wouldn't do a rear only upgrade as it'll throw off the dynamics of the car and would be more likely to, if you're in a turn and hit the brakes, cause you to oversteer (especially with weight in the back. Upgrade all around if you need better braking but you want to be biased towards the front of the car.

And when it comes down to it, don't brake in the turns, brake before the turns.

 

[Cephyr13]

I wouldn't do a rear only upgrade as it'll throw off the dynamics of the car and would be more likely to, if you're in a turn and hit the brakes, cause you to oversteer (especially with weight in the back. Upgrade all around if you need better braking but you want to be biased towards the front of the car.

And when it comes down to it, don't brake in the turns, brake before the turns.

That's what you'd think if you've never removed the rear brake bias valve or installed bigger brakes in the back, but I've removed it on several Taurus SHOs and put big brakes in the rear. SHOs are great track cars. I've had a few with nearly ever suspension mod you can get. I've tracked all of them in varying states of modification. When you remove the brake bias, you get more braking in the turns that keeps your rear from oversteer.

I have a business delivering fleet trucks so I get to drive tons of new trucks, but I used to primarily deliver passenger fleet trucks. When you have modern trucks in tow mode and the truck's rear end starts to oversteer, the truck only applied the rear brakes, and does so briefly, in order to stop the oversteer. So added braking is how you stop oversteer.

Bigger brakes in the rear, and removing the rear brake bias, has the same affect. When you take classes at the track, they teach you to push the brake and clutch to the floor if you start to oversteer. This virtually always results in a full spin. Why? Because both front and back brakes are being applied and the front end gets more braking thank the rear and the rear lifts as a result of it. When you have more braking power in the rear, the rear doesn't lift nearly as much because the front brakes aren't doing as much of the braking as they would have been doing otherwise, which keeps the rear more solidly planted.

Hopefully, I explained that sufficiently enough to be understood.

Yes, it's optimal to do all of your braking before you turn, but when you're running something like 24 hr Lemons, you don't always get the luxury of only braking in a straight line, so you better know how to brake properly in a turn and have a good setup or you're in trouble.

 

[Reinout]

That's what you'd think if you've never removed the rear brake bias valve or installed bigger brakes in the back, but I've removed it on several Taurus SHOs and put big brakes in the rear. SHOs are great track cars. I've had a few with nearly ever suspension mod you can get. I've tracked all of them in varying states of modification. When you remove the brake bias, you get more braking in the turns that keeps your rear from oversteer.

I have a business delivering fleet trucks so I get to drive tons of new trucks, but I used to primarily deliver passenger fleet trucks. When you have modern trucks in tow mode and the truck's rear end starts to oversteer, the truck only applied the rear brakes, and does so briefly, in order to stop the oversteer. So added braking is how you stop oversteer.

Bigger brakes in the rear, and removing the rear brake bias, has the same affect. When you take classes at the track, they teach you to push the brake and clutch to the floor if you start to oversteer. This virtually always results in a full spin. Why? Because both front and back brakes are being applied and the front end gets more braking thank the rear and the rear lifts as a result of it. When you have more braking power in the rear, the rear doesn't lift nearly as much because the front brakes aren't doing as much of the braking as they would have been doing otherwise, which keeps the rear more solidly planted.

Hopefully, I explained that sufficiently enough to be understood.

Yes, it's optimal to do all of your braking before you turn, but when you're running something like 24 hr Lemons, you don't always get the luxury of only braking in a straight line, so you better know how to brake properly in a turn and have a good setup or you're in trouble.

Great explanation and I do understand, but like many things, getting onto a track to actually put it into actions will actually make it make sense. How many armchair racers are out there and the explanation doesn't mean much to 99% of drivers.

Removing brake bias, or changing it, isn't for the faint of heart. A novice, which you clearly are not, shouldn't mess with their brake bias. Just like people chasing more HP but are running 2000w of stereo equipment and wheels/tires that weight 100lbs each = power waste.

While the majority of my formal driver's education was on the F1 racetrack in Zandvoort I cannot say that I have the race experience you have. You're right, not braking before the turn isn't always an option and knowing how to brake in the turn is important.

Edit: My reply to your first post was without knowing what your knowledge was about vehicle dynamics. No disrespect was intended BTW.

 

[Dannyboy]

I've got a 2010 golf tdi with the bigger 272 mm Bosch rear disc's and pads.
It is way better than the brakes on my 2014 jetta that is noticeable. They are more progressive and they bite hard without excessive pressure on the pedal that leaves you with squeaky butt moments.
I don't track mine but I do drive 'spirited'

Both vehicles both have the exact same brands, Zimmerman disks and TRW pads

 

[Cephyr13]

Great explanation and I do understand, but like many things, getting onto a track to actually put it into actions will actually make it make sense. How many armchair racers are out there and the explanation doesn't mean much to 99% of drivers.

Removing brake bias, or changing it, isn't for the faint of heart. A novice, which you clearly are not, shouldn't mess with their brake bias. Just like people chasing more HP but are running 2000w of stereo equipment and wheels/tires that weight 100lbs each = power waste.

While the majority of my formal driver's education was on the F1 racetrack in Zandvoort I cannot say that I have the race experience you have. You're right, not braking before the turn isn't always an option and knowing how to brake in the turn is important.

Edit: My reply to your first post was without knowing what your knowledge was about vehicle dynamics. No disrespect was intended BTW.

No disrespect taken. And I didn't mean any disrespect with my reply if anything sounded that way.

I still maintain that removing rear brake bias is safer for any driver. The more weight you have in the rear, the more you want those rear brakes to grab.

Think of it like this: when you're towing a trailer, and it starts to push your rear end into oversteer, the dynamic stability control only applies the rear brakes because that stops the oversteer. Applying front and back brakes at the same time doesn't stop the oversteer because it lifts the rear end due to too much braking up front and not enough braking in the back. But when you have more braking in the rear, this takes some of the work off of the front brakes and it keeps the weight from shifting forward as much, keeping the rear of the car planted better. Car manufacturers use brake bias because in a straight line, they want the front brakes to do most of the work since that's where most of the weight is transferring.

Now apply what I just described but for a car with a lot of weight in the back. When the car starts to oversteer, and you hit the brakes, you need as much braking power in the rear as you can get so that the rear of the car doesn't lift much. More lift equals more oversteer. Less lift equals more traction. You're more likely to stop the momentum of all of that weight from oversteering if you have more braking capacity in the rear to keep the rear planted.

However, if someone has manufacturer video or experience with this stuff and can show otherwise, I'm game. lol

I honestly don't see why manufacturers even bother with brake bias valves. My cars stop better without the brake bias. Makes for a more controlled, more well-distributed braking experience. But hey, I'm not an engineer, so I could be wrong. There could be something I don't know about that proves you right.

 

[Reinout]

No disrespect taken. And I didn't mean any disrespect with my reply if anything sounded that way.

I still maintain that removing rear brake bias is safer for any driver. The more weight you have in the rear, the more you want those rear brakes to grab.

Think of it like this: when you're towing a trailer, and it starts to push your rear end into oversteer, the dynamic stability control only applies the rear brakes because that stops the oversteer. Applying front and back brakes at the same time doesn't stop the oversteer because it lifts the rear end due to too much braking up front and not enough braking in the back. But when you have more braking in the rear, this takes some of the work off of the front brakes and it keeps the weight from shifting forward as much, keeping the rear of the car planted better. Car manufacturers use brake bias because in a straight line, they want the front brakes to do most of the work since that's where most of the weight is transferring.

Now apply what I just described but for a car with a lot of weight in the back. When the car starts to oversteer, and you hit the brakes, you need as much braking power in the rear as you can get so that the rear of the car doesn't lift much. More lift equals more oversteer. Less lift equals more traction. You're more likely to stop the momentum of all of that weight from oversteering if you have more braking capacity in the rear to keep the rear planted.

However, if someone has manufacturer video or experience with this stuff and can show otherwise, I'm game. lol

I honestly don't see why manufacturers even bother with brake bias valves. My cars stop better without the brake bias. Makes for a more controlled, more well-distributed braking experience. But hey, I'm not an engineer, so I could be wrong. There could be something I don't know about that proves you right.

None taken.

I think when it really comes down to it it would be interesting to have a bunch of similar/same cars with different biases and brake sizes set up.

The 4Runner forum I belong to people are always talking about bigger and bigger brakes, however that isn't always an improvement. On pavement sure, but even then there's limitations. You don't want to over-power the brakes for loose terrain.

There's no right or wrong, just preferences and then driving habits. I am also not an engineer so I can only speak to what I know and what I've done and what I know has worked for me in the past. On my old Sentra just going to cross-drilled and slotted was enough for what I did. Same with the Elantra. I'd be interested to try what you recommend with the rear wheel bias now, but I'm not going through the trouble to do it.

Or is it easy??????

Edit: One thing I'd like to get rid of, and I know some armchair drivers will cringe, is that I can't left-foot brake without the throttle kicking out. Also makes for more spirited driving.

 

[Cephyr13]

None taken.

I think when it really comes down to it it would be interesting to have a bunch of similar/same cars with different biases and brake sizes set up.

The 4Runner forum I belong to people are always talking about bigger and bigger brakes, however that isn't always an improvement. On pavement sure, but even then there's limitations. You don't want to over-power the brakes for loose terrain.

There's no right or wrong, just preferences and then driving habits. I am also not an engineer so I can only speak to what I know and what I've done and what I know has worked for me in the past. On my old Sentra just going to cross-drilled and slotted was enough for what I did. Same with the Elantra. I'd be interested to try what you recommend with the rear wheel bias now, but I'm not going through the trouble to do it.

Or is it easy??????

Edit: One thing I'd like to get rid of, and I know some armchair drivers will cringe, is that I can't left-foot brake without the throttle kicking out. Also makes for more spirited driving.

Well, it depends on the car. With Tuarus SHOs, it was easy. All you had to do was buy two plugs for the bias valve and insert them into the holes where you unplug the value lines from. That skips the entire valve, causing equal pressure to the front and rear brakes. There are more complex systems on some cars so it's probably more difficult with those. I only have experience with the SHO brake bias valves. It was super cheap and easy to increase the rear brake size, too, so it was a no brainer.

I forget if I tried it on my Maximas and I haven't tried on my E46 M3 because it's pretty well balanced for the track as is...but it's tempting. M3s are just so well balanced for the track that I hate to go messing with it. I'm afraid I'll throw off that balance.

Yeah, each car is different. Some come with undersized rear brakes and really need larger ones, where as some have pretty good sized rear brakes and don't really require a larger diameter for optimal braking. And heck, if you drive autocross, you want the brake bias because it helps you throw out the rear end to oversteer around corners that you need to oversteer around (i.e. - it's good for directing the nose and rear-end of the car for tight autocross turns).

I tried taking my old track SHO to an autocross one time and came in dead last because of the brake bias being removed, larger rear brakes, and a lack of rear wheel drive. LOL The only way I've seen front wheel drive cars win autocrosses is with massive weight reduction. I was not weight reduced, just heavily modded for road courses where you never want your rear end to oversteer. The car was basically set up for exactly the opposite type of racing. lol So there's something to be said for smaller rear brakes and brake bias valves in the right conditions. On the SHO, when you brake, your rear end body lifts (which is where the bias value is) and there's a tiny little lever on the bias valve attached to the H arms of the independent rear suspension. As the rear end raises away from the H arm, that little lever twists down a little, engaging the value to block some of the hydraulic pressure from the rear brakes is that the front brakes get more of the clamping power. That's excellent for rotating the rear of the car around tight turns. You really need that in autocross. Now imagine me out there with the opposite of that trying to rotate the rear end around tight turns. LOL My god, that car wouldn't rotate the rear end to save my life. It's was awful. I left after the first half of the day. Wasn't even worth running the second half. I was just curious how difficult it would be to compete in that car in autocross and I got my answer pretty quickly. The first place car that day was an E46 M3, which is what I have now. If you can't beat'em, join'em. Then again, I've always loved M3s and I don't really autocross anymore. It's boring once you run a road course.

 

[Paulman]

Does the native Electronic Stability Control (or whatever it's called) in the MK6 insure that you'll never spin out in tight, fast turns?

 

[Cephyr13]

Does the native Electronic Stability Control (or whatever it's called) in the MK6 insure that you'll never spin out in tight, fast turns?

That's a good question. My Dynamic Stability Control (DSC) tends to catch any wheel spin or traction loss, but I haven't tried to oversteer it in a high-speed turn to lose rear-end traction to test the DSC before. It's possible it does, but someone who's tested it will have to chime in here with real world experience. If I didn't have all of the heavy hitches in the trunk, I'd go test it right now.

I'm pretty sure the DSC is strictly for the front tires because it's supposed to simulate a positrack differential and it does a pretty decent job of it. However, that would mean it would only affect the front wheels to try and keep the rear end from oversteering, and that, in my opinion, is either dangerous or would be infuriating for someone like me who hates when a car tries to take over responsibility for traction or braking. On the other hand, though, my E46 M3, which is also German and 10-years older than the VW, cuts fuel to keep the rear end from oversteering or the rear tires from spinning when the dynamic stability control is on. I hate it. If I forgot to turn it off and I try to dart across the road in front of oncoming traffic and the car cuts the fuel due to wheel spin, that could cause an accident. So I do my best to always turn it off when I start the car. I wish my tune had it turned off as a default rather than stock, which requires me to manually turn it off. I haven't seen the VW do anything like that so far with its traction control.

Sorry I can't give you a definite answer.

 

[Dannyboy]

Does the native Electronic Stability Control (or whatever it's called) in the MK6 insure that you'll never spin out in tight, fast turns?

ESC basically uses the yaw rate sensors to detect how much force the car is over or understeering and applies the brakes to individual wheels at different rates to bring the car back to a controllable condition.

However along the lines of " ESC can't defy the laws of physics and can't be solely relied upon" is print in the manual. It holds true but to its credit ESC has got me out of a pickle several times.
I hit a massive patch of ice on a sweeping highway entrance ramp years ago and the car understeered for what seemed the longest skid in my life and then the vehicle front pulled around . Squeaky butt moment.

Answer is it tries to correct the problem but depending on the situation, may not be able to do enough in time due to speed, conditions etc

 

[Paulman]

Thanks for your reflections.
I wonder how one would test this?
Find a large, empty parking lot and go WOT while the steering wheel is locked hard in left or right?
Seems like something would break doing this.