Fitting stiffer sway bars that won’t ruin our GTI’s streetability?

Tom
Update by Tom Suddard to the Volkswagen Golf GTI project car
Oct 10, 2023 | VW, GTI, 034 Motorsport, Sway Bar

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Could stiffer sway bars make our GTI faster on track without hurting its street manners? In theory, yes—increasing roll stiffness to control body roll should limit dynamic camber loss and increase grip without the downsides associated with stiffer springs. As an added bonus, adjustable bars would let us tune the car’s balance to fix its tendency to understeer–but would it work in practice? Let’s find out.

For this test, we’ll be using stiffer bars from 034Motorsport. The front bar retails for $358 and includes new brackets and bushings, while the rear sway bar retails for $320 and comes with the same accouterment.

We also splurged for the company’s adjustable end links for the front and rear sway bars, totaling $324 for a set of four.

Why not just use the factory pieces? Two reasons: First, the VW’s stock rear end links are plastic, and we were worried about their durability on track with stiffer sway bars. Second, adjustable end links will let us easily solve any interference issues that come with the aftermarket bars, as well as adjust out any static preload that the car might exhibit.

Rather than throw everything onto the car at once, we decided to make one change at a time, starting with the rear sway bar. Why start out back? We were desperate to reduce the car’s understeer, and it was also the easier installation by far—20 minutes vs. a few hours.

If you’re only going to change one bar, we’d highly recommend starting at the rear of the car. This single improvement made a night and day difference in how our GTI drove, turning it from a test in patience with understeer into a car that could finally be poked and prodded into rotation when we wanted it to.

The stopwatch also agreed with this improvement—we saw lap times at our official test track, the Florida International Rally & Motorsport Park, drop from a fastest lap of 1:22.44 to 1:21.67 with the bar on its stiffest setting.

[Can a rear sway bar really make our GTI faster on track?]

Nearly a second is nothing to sneeze at, but we wondered if there was more time left in the GTI, so we installed 034’s front sway bar. The install wasn’t particularly difficult—figure a few hours on a lift—but did require lowering the front subframe and a second person’s help at a few points.

Why install a stiffer front sway bar in a car that’s already understeering? It’s a bit counterintuitive, but our theory was as follows: In a softly sprung MacPherson-strut car with a street-friendly alignment (like our GTI), we need all the negative camber we can get up front. A stiffer sway bar reduces body roll, which reduces dynamic camber loss, which increases front grip.

In theory, at least…

In practice, we went back to the FIRM and set a new personal best with the front sway bar on its soft setting: a 1:20.99 lap. Stiffening the front bar didn’t produce a faster time, but we were also working with a rapidly warming track, meaning there might be even more time left on the table.

So what did we learn? Well, we dropped nearly 1.5 seconds just from stiffer sway bars and noticed absolutely zero impact on the car’s street manners or NVH.

This puts the GTI near the top of our lap time leaderboard, slotting in right behind our own MR2 Turbo project car and ahead of a brand-new Mk8 Golf R. That’s not bad for our daily driver—but we’ll keep improving it in the next update.

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Comments
Colin Wood
Colin Wood Associate Editor
10/10/23 9:42 a.m.

Alright, twist my arm, I'll start shopping for a rear sway bar for my Fit. wink

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/10/23 9:53 a.m.

The place you're most likely to notice a change in street manners is on pavement that's uneven from side to side. The car will rock more and you'll get more lateral "head toss".

In my experience, there's usually a threshold where the bars start having more impact on the ride (har har) than they do on the handling. A mild sway bar upgrade works well, an aggressive one may not.

Also, $1002 for a set of sway bars and end links. We're selling to the wrong customer base! You can get a set of FM bars and end links for less than half that.

CAinCA
CAinCA GRM+ Memberand Dork
10/10/23 1:50 p.m.

Interesting. I tried the 25.4mm 034 rear bar on my MK6 GTI. It was fine by itself but when I installed a 26mm H&R front bar it was way too stiff. I wound up running it on the softest position all of the time. I wound up swapping it to a H&R 24mm rear bar and it was great. 

 

Also, the 034 bushings dried out quickly and had to be relubed pretty regularly. The H&R bushings were teflon lined and never squeaked.

CrashDummy
CrashDummy Reader
10/10/23 3:01 p.m.

Curious how the rates compare to the stock bars....how much stiffer is the new rear bar? How much stiffer is the aftermarket front bar on full soft compared to the stock front? 

edmagoo
edmagoo New Reader
10/10/23 3:02 p.m.

I have always wondered why sway bar manufacturers add bends in the center section when there is nothing in the way of a straight bar.

I also wonder about cutting the center section of a stock bar and replacing it by welding a DOM center section like this:

https://forum.miata.net/vb/showthread.php?t=235046

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/10/23 3:47 p.m.

In reply to CrashDummy :

Because a sway bar is only part of the roll stiffness, it takes a fairly significant change to really effect a handling change. The new bars could easily be twice as stiff as the originals. It's an easy thing to misinterpret which is why we don't publish our rates, but we'll give them to you if you ask.

In reply to edmagoo :

Sometimes those bends are used as stops to prevent the bar from sliding side to side.

I would be very concerned about putting a piece of DOM in the middle of a sway bar and how long the joint would hold up. I would be more likely to try to modify a bar from another car to fit instead of splicing DOM in the middle.

CAinCA
CAinCA GRM+ Memberand Dork
10/10/23 6:22 p.m.
CrashDummy said:

Curious how the rates compare to the stock bars....how much stiffer is the new rear bar? How much stiffer is the aftermarket front bar on full soft compared to the stock front? 

IIRC: The 26mm rear bar is something like 1.75 - 2.25x stiffer than stock.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
10/10/23 6:30 p.m.

It was my understanding that bars were made of spring steel and could not be welded.  Am I wrong?

 

Being wrong would be nice smiley

SkinnyG (Forum Supporter)
SkinnyG (Forum Supporter) PowerDork
10/11/23 2:29 a.m.

(I've fabricated quite a sway bars out of mild steel)

fanfoy
fanfoy SuperDork
10/11/23 9:58 a.m.
Keith Tanner said:

Also, $1002 for a set of sway bars and end links. We're selling to the wrong customer base! You can get a set of FM bars and end links for less than half that.

That price is pure insanity.

As for the material discussion, I see a lot of contradictory information, but an application like the GTI, there really is no reason to use any fancy alloy. The twist is so small that the stress is absolutely tiny. 

Maybe on an application that uses the sway bar to locate the lower control arm (like 80's Ford used to do), a stronger alloy might be needed? Maybe.

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