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post #11 of 35 (permalink) Old 03-19-2006, 02:23 PM Thread Starter
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The TVS kit is springs and sways. It does lower the car, but very little -- less than an inch. I believe it's advertised as dropping 15 mm in the front and 19 mm in the rear. I don't currently have any issues hitting stuff with the OEM chin spoiler, however I can see it happening if you have some aftermarket bumper or spoiler.

While the hotchkis springs give a net increase in spring rate, it's pretty small so you don't notice it. However, what you do notice is an improved overall ride since they change the balance by increasing the rate up front and decreasing it in the back. It got rid of that annoying highway bounce. Of course, they also helped increase the overall handling, too.

Unfortunately, there are enough driveways and lots around here with steep approaches that at stock height, we've scraped the underside of the stock chin fairly often. It's down where it can't really be seen, but it's aggravating doing it as often as it happens now, let alone if we go lower.
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post #12 of 35 (permalink) Old 03-19-2006, 02:26 PM Thread Starter
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stiffer in front, softer in rear
By stiffening the front, and softening the rear, does that effect the under/oversteer issues at all? Seems like that would also increase the tendency to oversteer, unless they expect you to match it with the hotchkis sways on the agressive settings, where it's MUCH stiffer in the rear than the front (dialing back out the understeering)?
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post #13 of 35 (permalink) Old 03-19-2006, 02:38 PM
 
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By stiffening the front, and softening the rear, does that effect the under/oversteer issues at all? Seems like that would also increase the tendency to oversteer, unless they expect you to match it with the hotchkis sways on the agressive settings, where it's MUCH stiffer in the rear than the front (dialing back out the understeering)?
All things being equal, yes, stiffer front and softer rear will add a little oversteer, theoretically. However, by lowering the car a bit, you get more camber. And as you mentioned, the sways can work that so it's more balanced.

I felt that overall the whole package was a huge improvement over stock.
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post #14 of 35 (permalink) Old 03-19-2006, 03:08 PM Thread Starter
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All things being equal, yes, stiffer front and softer rear will add a little oversteer, theoretically. However, by lowering the car a bit, you get more camber. And as you mentioned, the sways can work that so it's more balanced.

I felt that overall the whole package was a huge improvement over stock.
So stiffer front springs or stiffer rear sways increases oversteer, stiffer rear springs or stiffer front ways increase understeer?

I think that makes sense, in a hard turn, the front outside tire won't compress as much, although it's got a lot of weight on it. Then the rear will try to pivot around that point? vs. with stiffer rear springs, the rear outside corner is more of the pivot point for the car's tendency to yaw? And if you get it just right, you get a perfect neutral 4-wheel drift?

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post #15 of 35 (permalink) Old 03-20-2006, 12:49 AM
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If one brakes into a turn, doesn't that lose control? I would think so. I think a driver has to find the medium or point of balance between throttling and slowing down to take corners well.
Only if you do it wrong.

Its a technique called "trail braking". You carry a bit of brakes into the corner to keep the front end loaded so you get more pressure over the front tyres. As long as you're not braking too hard to cause the fronts to exceed their grip threshold and plough understeer, it can also get the car to turn in a bit more sharply as the rear unloads and gets a little light. Of course, that also means you're liable to spin if you fail to control the brakes properly.

It also allows for "supa-laate boraiking technique des'ka!" (to borrow a BMI term) since you can brake a little later, and turn in a little better, than someone who does the traditional "brake only in a straight line" technique and take them up the inside.

With the stock setup as understeery as it is, trail braking is the best way to get the Z to turn in smoothly. Your biggest issue is progressively easing off the brakes and onto the throttle to not have it oversteer. Trail braking is not an easy skill, and the cost of failure can be quite high if you haven't got decent runoff. Just practice somewhere with plenty of runoff.

I used to be able to do it quite well (and the Z is quite easy to steer on brakes as well as throttle, I discovered) but I've stopped driving in anger as much as I used to, so I've lost it.


As for the original question, I think swaybars are the first upgrade if you want a bit more handling without a loss of ride.

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Understeer is when you hit the tree with the front wheel.
Oversteer is when you hit it with the back.
Horsepower is how hard you hit the tree...
Torque is how far you drag it...
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post #16 of 35 (permalink) Old 03-20-2006, 05:04 AM
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Only if you do it wrong.

Its a technique called "trail braking". You carry a bit of brakes into the corner to keep the front end loaded so you get more pressure over the front tyres. As long as you're not braking too hard to cause the fronts to exceed their grip threshold and plough understeer, it can also get the car to turn in a bit more sharply as the rear unloads and gets a little light. Of course, that also means you're liable to spin if you fail to control the brakes properly.

It also allows for "supa-laate boraiking technique des'ka!" (to borrow a BMI term) since you can brake a little later, and turn in a little better, than someone who does the traditional "brake only in a straight line" technique and take them up the inside.


If you brake too hard in a corner, it's not the front exceeding too much grip that you have to worry about.. It's the transfer of weight and unloading of the rear end. Trail braking is used as you say to out brake your opponent who is just braking in a straight line.

Braking in the right spot before the turn does in fact load up the front end with weight. No problem. However, there are only a few turns I would even worry about trail braking into. Otherwise, I'd rather be on the throttle, not the brakes. It's all about exit speed.

Good discussion.


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post #17 of 35 (permalink) Old 03-20-2006, 11:26 AM
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If you brake too hard in a corner, it's not the front exceeding too much grip that you have to worry about.. It's the transfer of weight and unloading of the rear end. Trail braking is used as you say to out brake your opponent who is just braking in a straight line.
Depends on how hard you're working the brakes. If you're braking really hard, then most of your front tyres' total grip threshold will go towards decelleration in the fore/aft plane. If you try to turn in, then there's not enough grip to do so and the nose ploughs wide. I've done it enough times on the track, and on the street a few times :( Overshot my braking point, and can't come off the brakes because I'm going too quick. Had to rely on ABS to get me around the corner, badly.

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Braking in the right spot before the turn does in fact load up the front end with weight. No problem. However, there are only a few turns I would even worry about trail braking into. Otherwise, I'd rather be on the throttle, not the brakes. It's all about exit speed.
It can also be used to drive around a car's inherent turn-in understeer. As you say, it does unload the rear and make it swing around a bit.

I know of a couple of pro drivers in Australia that use it in Porsches. They'll left foot trail brake into corners to help load the front up on a very rear heavy car, and keep the right foot on the throttle to keep the engine load up for more power once they come off the brakes.

Our local journos also bitch and moan about Audi's nanny systems, that throw a hissy fit when the throttle and brake pedals are actuated at the same time. It assumes the driver is in trouble and initiates the stability control, cutting power, when all they want to do is get the damned thing to turn in while keeping the revs / engine load up. Drives them mad.


This might be better off in the Driving Techniques forum.

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Understeer is when you hit the tree with the front wheel.
Oversteer is when you hit it with the back.
Horsepower is how hard you hit the tree...
Torque is how far you drag it...
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post #18 of 35 (permalink) Old 03-20-2006, 11:38 AM
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Depends on how hard you're working the brakes. If you're braking really hard, then most of your front tyres' total grip threshold will go towards decelleration in the fore/aft plane. If you try to turn in, then there's not enough grip to do so and the nose ploughs wide. I've done it enough times on the track, and on the street a few times :( Overshot my braking point, and can't come off the brakes because I'm going too quick. Had to rely on ABS to get me around the corner, badly.
If you are using 100% of your traction for braking, than you have nothing left to ask for. If you turn in, and the nose ploughs wide, the car is understeering. Putting all the weight forward is helping them grip more, yes. But, to me it's more a problem of what happened before that. If the nose end is plowing, there was a mistake prior to that happening. So, I understand what you are saying 100%. I teach vehicle dynamics. What I was saying, is I'd rather not have to be on the brakes. But on the throttle increasing my exit speed. Tit for tot.




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It can also be used to drive around a car's inherent turn-in understeer. As you say, it does unload the rear and make it swing around a bit.
Braking while turning is a great way to create over steer. Which is a great way for an inexperienced driver to get hurt. :( I completely understand where you are coming from.


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I know of a couple of pro drivers in Australia that use it in Porsches. They'll left foot trail brake into corners to help load the front up on a very rear heavy car, and keep the right foot on the throttle to keep the engine load up for more power once they come off the brakes.

Another reason why certain people like to trail brake and left foot brake, etc.. is to keep the turbo spooled up so when they are on corner exit, it's ready to go. Driving is technique. What's great is that everyone is different just like cars are different.


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Our local journos also bitch and moan about Audi's nanny systems, that throw a hissy fit when the throttle and brake pedals are actuated at the same time. It assumes the driver is in trouble and initiates the stability control, cutting power, when all they want to do is get the damned thing to turn in while keeping the revs / engine load up. Drives them mad.
This might be better off in the Driving Techniques forum.

Yes. I don't like the elec. gizmos unless I'm not driving. Those systems save more people that don't know, than stop more people that do.

Again, I have taught several SAE Vehicle Dynamics classes and have gone down this path of discussion over and over.. Over zealous drivers complaining about systems that can stop better than them. Yet, they complain that it is "messing them up".. When it's actually trying to cover up poor driving technique, 90% of the time. It's the other 10% that bugs me. So, I normally shut them off.

Fortunately, I've had the chance to test and plot data with and without electronic systems and ABS in place. Most of the time, they operate within their means. Certain scenarios can provide interesting results though.

This probably would be better off in the "driving forum" but at least it's being talked about at all.

Have a good evening.


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post #19 of 35 (permalink) Old 03-20-2006, 02:40 PM
 
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At Skip Barber, they tought trail braking as an advanced driving tecnique and remarked on how incredibly hard it is to use correctly and efficiently. They said we can feel free to practice it, but that we would probably have better results if we just focused on braking in a straight line.

Basically, trail braking is a great way to maximize your entry speed, but it's really easy to mess up. If you do mess up, at best you hurt your exit speed, or at worst, you lose control. So unless you are a seasoned driver, I don't recommend trail braking. Wait till you have mastered the more basic stuff first. If you can effectively trail brake, more power to you!
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post #20 of 35 (permalink) Old 03-20-2006, 03:27 PM
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All things being equal, yes, stiffer front and softer rear will add a little oversteer, theoretically. However, by lowering the car a bit, you get more camber. And as you mentioned, the sways can work that so it's more balanced.

I felt that overall the whole package was a huge improvement over stock.
Actually, just the opposite happens. Stiffer in front adds understeer. A stiffer front end means that, when cornering, most of the lateral load transfer is absorbed by the outside front tire, since the front end resists roll more. The extra load on the outside front tire causes it to slip more, hence the understeer. You can stiffen the front with springs, or with a larger anti-sway bar.

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