This is How a Rear Sway Bar Will Unlock More Speed | Mk7 GTI
Summary
TLDRIn this video, the host demonstrates the installation of a larger rear sway bar on a Mark 7 Volkswagen GTI, explaining its benefits for track performance. The host uses a Miata antenna as a model to explain how sway bars function, reducing body roll and improving suspension dynamics. By increasing rear roll stiffness, the GTI can achieve a more neutral or oversteer-biased handling, reducing understeer. The video also covers related components like urethane bushings and adjustable end links. Overall, the modifications aim to improve the car's track performance without sacrificing daily driving comfort.
Takeaways
- 🔧 The video focuses on installing a larger rear sway bar on a Mark 7 Volkswagen GTI to improve track performance.
- 💡 A sway bar acts as a spring, resisting body roll by connecting both sides of a car's suspension.
- 🚗 The rear sway bar increases roll resistance, helping to reduce body roll and improve cornering on a track.
- 🔄 Installing a stiffer rear sway bar reduces dynamic negative camber loss, which keeps more tire traction during cornering.
- 🔧 The stiffer rear sway bar also helps correct the understeering nature of the GTI, shifting the handling balance towards oversteer for better cornering.
- ⚙️ The sway bar works by redistributing cornering loads between the front and rear of the car, which enhances grip and performance.
- 🔩 Adjustable end links ensure the sway bar remains neutral and doesn’t affect the car’s suspension when stationary.
- 🛠️ The use of urethane bushings reduces binding in the sway bar, making it more efficient and predictable in operation.
- ❗ Increasing spring rates by stiffening the sway bar reduces compliance, meaning the car will be less smooth over bumps.
- 🏁 The modification is aimed at improving track performance without compromising much on daily driving comfort.
Q & A
What is the purpose of installing a bigger rear sway bar on a car?
-A bigger rear sway bar increases rear roll stiffness, helping control body roll and shifting the car's handling balance from understeer towards oversteer, which can improve performance, especially in front-wheel-drive cars like the GTI.
How does a sway bar function in a car's suspension system?
-A sway bar acts as a spring between the two sides of the car's suspension. It allows for little resistance when both wheels move together but resists when one wheel moves independently, adding roll resistance and helping manage body roll during cornering.
Why is reducing body roll important for track performance?
-Reducing body roll helps minimize dynamic camber changes, especially on cars like the GTI. This ensures the tires maintain better contact with the track, improving grip and handling.
What is dynamic camber change and why is it undesirable?
-Dynamic camber change refers to the gain or loss of negative camber as the suspension moves through its range. It’s undesirable because it can reduce the contact patch of the tires with the road, reducing traction.
Why is increasing rear roll stiffness particularly useful for front-wheel-drive cars?
-Increasing rear roll stiffness can shift more of the cornering load to the rear of the car, reducing the load on the front, which helps mitigate understeer—a common issue in front-wheel-drive cars like the GTI.
What is the function of sway bar bushings and why are urethane bushings used in this project?
-Sway bar bushings allow the bar to rotate freely. Urethane bushings are used because they reduce binding and deflection compared to stock rubber bushings, ensuring more predictable and efficient performance from the sway bar.
What role do adjustable end links play in the sway bar setup?
-Adjustable end links connect the sway bar to the suspension and allow fine-tuning so the sway bar doesn’t press on the suspension at rest. This ensures the sway bar operates evenly without biasing one side.
What are the potential downsides of increasing spring rates with a stiffer sway bar?
-The downside of increasing spring rates is the reduction in suspension compliance, which can make the car less able to absorb bumps and changes in the road surface. However, in this case, the trade-off is expected to improve track performance.
How does a stiffer sway bar impact daily driving comfort?
-While a stiffer sway bar reduces suspension compliance, in this project, it is not expected to significantly affect daily driving comfort despite the increase in roll stiffness.
Why was a demonstration with a Miata antenna used in the video?
-The Miata antenna, acting as a spring in the demonstration, was used to visually explain how a sway bar functions. It shows how the sway bar resists twisting, illustrating the spring effect that helps control body roll in a car.
Outlines
🔧 Introduction to Rear Sway Bar Upgrade for the GTI
The video begins with a focus on upgrading the rear sway bar of a Mark 7 Volkswagen GTI, explaining how this modification can improve performance on the track. Although the primary focus is on front-wheel-drive cars like the GTI, the advice applies to most vehicles. The presenter starts with an illustration using a Miata antenna to explain how sway bars function, comparing them to springs that act rotationally. This demonstration leads to an explanation of the sway bar’s role in reducing body roll and increasing roll resistance, which can be fine-tuned separately from the main suspension spring rate.
🚗 Sway Bar Mechanics and Its Role in Handling
The next part discusses the sway bar's function as a spring that connects the left and right sides of the car’s suspension. When one wheel moves, the sway bar resists that movement, creating roll resistance that helps reduce body roll during cornering. This section goes deeper into the benefits of having a sway bar in the rear suspension, explaining how it can independently adjust roll resistance and improve the car’s handling, making it faster or more comfortable without compromising ride quality.
📏 Upgrading to a Bigger Rear Sway Bar for GTI Performance
The presenter shifts focus to the upgraded sway bar for the GTI, a front-wheel-drive car. The larger sway bar is expected to control body roll, reduce negative camber loss, and enhance traction in the front tires during cornering. The main reason for upgrading the rear sway bar is to reduce understeer and help the car handle more neutrally or even slightly oversteer. This is achieved by increasing the rear roll stiffness, which shifts some of the cornering load from the front to the rear, improving the car’s overall cornering ability.
🔩 The Importance of Free-Moving Sway Bars
The focus turns to the parts surrounding the sway bar, specifically the sway bar bushings. Ideally, these bushings should allow the sway bar to move freely without adding resistance, but stock rubber bushings often bind and are poorly lubricated. To fix this, the presenter plans to install urethane bushings from 034 Motorsport, which are greasable and stiffer, allowing the sway bar to move more predictably and without deflection. Adjustable end links will also be installed to ensure that the sway bar is not biased toward one side when the car is at rest, ensuring better handling.
⚖️ Downsides of Increasing Rear Roll Stiffness
Although increasing the rear roll stiffness offers many performance benefits, it comes with the downside of reduced compliance. Anytime spring rates are increased, the car becomes less able to absorb bumps and variations in the road, which can affect comfort. However, the presenter believes the trade-off will be worthwhile, as the sway bar upgrade should make the GTI faster on the track without significantly affecting its drivability in daily use.
🏁 Final Thoughts and Call to Action
The video wraps up with a summary of the anticipated benefits of the sway bar upgrade and a call to action for viewers. The presenter mentions that the next step is to install the upgraded parts and take the GTI to the racetrack. Finally, viewers are encouraged to like the video, subscribe for more content, and visit the Grassroots Motorsports website for additional resources, supported by CRC Industries.
Mindmap
Keywords
💡Sway Bar
💡Roll Resistance
💡Spring Rate
💡Dynamic Camber
💡Understeer
💡Oversteer
💡End Links
💡Body Roll
💡Compliance
💡Bushings
Highlights
Introducing the Mark 7 Volkswagen GTI project and the plan to install a bigger rear sway bar for improved track performance.
Explanation of how changing the size of a sway bar can impact a car's performance, with a focus on front-wheel drive vehicles like the GTI.
Demonstration using a Miata antenna as a simple model to explain how sway bars function like a big spring, resisting rotational movement.
The role of sway bars in reducing body roll by increasing roll resistance, which is crucial for maintaining better tire contact during cornering.
Discussion on how sway bars can be used to tune suspension independently of the spring rate, offering more control over a car's handling characteristics.
Description of the basic design of a sway bar, highlighting its straight part and two levers, and how it interacts with the suspension system.
Installation of zero three four Motorsport rear sway bar on the GTI, emphasizing the bar’s design to fit the vehicle while maintaining its fundamental function.
Detailed explanation of how a stiffer rear sway bar helps in controlling body roll and reducing dynamic camber loss, particularly beneficial for the GTI’s front suspension.
The primary reason for installing a bigger rear sway bar: to increase rear roll stiffness, shifting the car's balance towards oversteer, which enhances turn-in and cornering stability.
Discussion on how altering roll stiffness at the rear of a front-wheel-drive car like the GTI can reduce understeer, leading to more neutral handling.
Importance of sway bar bushings and end links in ensuring the sway bar operates without resistance, binding, or unintended spring rate changes.
Advantages of using urethane bushings for the sway bar, which reduce deflection and enhance predictability in handling.
Introduction of adjustable end links, which allow for precise tuning of the sway bar's effect on the suspension, ensuring balanced performance.
Discussion of the trade-offs involved in increasing roll stiffness, such as reduced compliance and the impact on comfort versus performance.
Conclusion highlighting the expected benefits of the rear sway bar upgrade in terms of track performance and the minimal impact on daily driving comfort.
Transcripts
okay we're back in the garage working on
our Mark 7 Volkswagen GTI project car
and today we're going to be putting a
bigger rear sway bar on the car now
before we do that though I wanted to
talk a little bit about uh kind of what
changing the size of a sway bar on a car
can do and why it's going to at least
theoretically help our GTI on track and
while most of this video is going to
deal with sway bars in the context of a
front-wheel drive track car it's fairly
Universal advice that you can apply to
any car so before we talk about the sway
bar on our GTI though I wanted to talk
about this Miata antenna which uh yes
it's off our old lemon's car but it's
just a piece of spring steel and it's a
good way to start talking about how sway
bars work so I'll put this in the Vise
here grab the other end with a pair of
vice grips here and all I want to
illustrate here is that this is just a
Big Spring
when you twist it it bounces back just
like a coil spring on the car except
it's working rotationally here and it
Springs back so why does this matter
because a an anti-roll bar is basically
just a Big Spring let's take that to the
next logical leap and go ahead and bend
it into the shape of a basic suite and I
went ahead and did that here so as you
can see we have a straight part and then
we have two levers on each end so I'll
turn it so you can see it and when you
twist one lever it tries to spring back
here
so um we've gotten the basic shape of a
sway bar in a car let's go ahead and get
sway bar bushings now and uh I've just
got two little nuts here so I can go
ahead and slip them on like this
and now we have an easy way for our sway
bar to rotate so I can put that in the
Vise so now that I've installed kind of
our little Miata antenna sway bar onto
the bench here you can really start to
see how it works in a car so we still
have our two levers we still have the
actual springy part of the bar and when
you move one up or down
see you can twist
and you're getting that same spring
action so why do we put these on cars
what does this do for suspension so if
you connect each side of the sway bar to
the suspension the spring rate is
basically zero when both wheels are
moving at the same time but when one
wheel tries to move while the other
doesn't it creates resistance so we call
this roll resistance in a car and
basically a sway bar is one of the
tuning Tools in a suspension system to
change the roll resistance at each end
so what's the benefit of having this
third spring in the rear suspension
that's only acting on body roll
um a couple different reasons to do this
first of all it lets you change roll
resistance independently of spring rate
so where you might optimize spring rate
to help with power down or to go over
bumps in the road this can is just
another tuning tool to make a car faster
or more comfortable okay so I've talked
about my little bench test sway bar
that's just a big Square here how do we
actually package that into a car and
that's when you start to get sway bars
like this front bar from zero three four
Motorsport designed to fit our GTI and
you can see it's got a couple extra
little bins in there just to go around
different parts of the car but even
though this is bent and has some extra
you know kind of features it's still
basically a straight bar with two levers
on each end and it will act like that
next I want to talk about what it does
to the car and what specifically going
bigger in the rear sway bar can do to a
front wheel drive car so the first thing
it's going to do to our GTI is it's
going to help control body roll now body
roll is basically when the body of a car
leans over in a corner everybody's felt
it when they've taken a corner at any
speed body roll is not really something
you want on a race track normally
because body roll leads to Dynamic
camber change especially on our GTI so
Dynamic camber change is basically a
gain or loss of negative camber when a
suspension Cycles through a train's
range of motion and we want to lose as
little negative camber as possible on
our GTI especially up front with the
struts
so by putting a stiffer rear sway bar on
our GTI it should reduce body roll which
should reduce Dynamic negative camber
loss which should give the tires more
traction to work with but that's not the
main reason we're doing it sure it
controls body roll which is nice we're
actually trying to increase the rear
roll stiffness in the back of our GTI
um why do you want to increase rear roll
stiffness on a track car especially a
front-wheel drive track car because it
understeers like a pig right now there's
those camber plates we put up front
definitely helped it does have more
front grip but the car is still kind of
an understeering nose heavy car so we
would like the car to handle more
neutrally or even bias towards oversteer
to help it turn in and to help keep that
front end from washing out on every
corner so increasing the rear roll
stiffness can be a good tool to do that
roll stiffness changes at one end of the
car are a way to shift the balance of
load in a corner between the front and
rear so for our GTI by increasing the
rear roll stiffness we should be able to
force the rear of the car to take more
of the cornering load which forces the
front of the car to take less of the
cornering load in theory that biases
biases it more towards oversteer than
towards understeer and should help it
handle better let's talk a little bit
more about the parts that surround a
sway bar or at least that should
whenever you install one on your car as
you can see here on my little mihada
antenna model again it has absolutely no
drag from the sway bar bushings these
two nuts here and that's what you want
you want the sway bar to be able to
float around completely free of any
resistance or binding when it's in the
car when it's not connected to the
suspension that's not usually what
happens with stock bushings they're
rubber they tend to bind they're not
lubricated that well so we're going to
go ahead and put a set of zero three
four Motorsport
urethane rear sway bar bushings on the
car and these are greasable they're also
a little stiffer So in theory these
should let the sway bar move up and down
without any binding or Extra Spring rate
introduced and the urethane should mean
that the entire bar twists around less
and has less deflection again we're
trying to isolate all of the force into
that sprung part of the bar to to keep
things predicted able oh we're also
going to be putting on adjustable end
links end links connect the the sway bar
to the suspension these are basically
just a solid Rod that translates a
motion from the wheel into motion at the
sway bar we put adjustable end links on
wherever possible because you don't want
the sway bar to be pushing on the
suspension when it's just at static ride
height at rest when both wheels are in
the same spot and by being able to
adjust the the length of these
individually we can make sure that the
sway bar isn't biased towards one side
of the car or another or starting to
press on the suspension when the car is
just parked these are also a handy tool
you can use sometimes when you're Corner
waiting that sort of thing but that's
pretty Advanced I'm not going to get
into that on this project I should talk
about the downsides and the downsides
are a loss of compliance so anytime
you're increasing spring rates anywhere
in a suspension you are reducing the
amount of compliance in the car and the
ability of the tire to press itself over
little bumps and changes in the asphalt
that sort of thing so we think the
upside is drastically out with downsides
here we think that this is going to make
the car faster we don't think it's going
to have really any effect on its daily
driver Comfort potential Etc but it's
worth noting that anytime you increase
spring rate you reduce compliance so the
only thing left to do is uh put it on
and go to the racetrack so if you like
this video please make sure you like And
subscribe until next time I'll see you
at the track
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