GoatAutomotive
Autocross Champion
- Location
- Cedar Park, TX
- Car(s)
- 2017 VW GTI SE, DSG
EDIT: Post#1 cleaned up completely & heavily revised 11/1/22 per feedback from contributors - hope this helps!
Welcome, MQB family. This write-up will address the rear sway bar mod, what it helped or hurt, and whether upgrading the RSB end link on the Mk7 chassis is a significant improvement.
Its purpose is to help any other readers and researchers seeking better handling, and to make a confident purchase on their next upgrade(s).
As a supplement to the topic, I've included a link with a proper walk-through on how sway bars work, and how changing diameters can positively or negatively impact a car's handling behavior. This will help newcomers better grasp the basics of this upgrade: Chris Rosales - The Drive - Why sway bars should be your first suspension mod...
The above is a great read, with much better photos than I had available for my own write-up.
Chris captured live-action shots of his Mk6 GTI on track, before and after sway bar upgrades, to show the difference in weight distribution across the car and its tires.
The info and lessons shared applies to all cars, but is specifically catered to a FWD layout.
DAP also did a good article with neat diagrams explaining how different sway bars can alter or induce under and over-steer: Ask DAP! Sway bar benefits for your FWD
DISCLAIMER: I understand some folks won't want to read all the juicy content below. I get it. No harm. Click the back button.
Cliff's Notes (not a secret): "Big Bar Good." ?
But you'll have to read to learn what was good, and what was better about this little experiment.
The idea began ~3yrs ago, on a completely stock GTI w/PP and some max summer Michelin tires:
The Mk7 GTI truly handles beautifully out of the box for a production FWD. The factory LSD and Golf R brakes make it a cut above.
Real tires make it even better, like running shoes for Usain Bolt.
But for those of us who drive it hard in corners, who exploit its athleticism, what if there's a little bit more available to us in the suspension?
What if this car just needs a few “tweeks” to truly shine and be competitive, without becoming a punishing "tuner car"?
So there it was. And admittedly, some modifications in the speed game induce more harm than good to a street car. They can compromise road manners, and even fatigue other components on the car prematurely.
The rear sway bar upgrade has been touted to me by others since my Mk5 days in 2006. As one performance shop owner told me:
"Upgrading only the rear sway bar on a FWD car allows improved body control, without inducing unwanted understeer to the front axle. The front axle is still allowed to rotate in towards the apex."
Actual conversation by phone 16 years ago. Let's dive in and see if there's any truth in the statement
.
Test Car - 2017 VW GTI, SE w/DSG.
~3100lbs after full exhaust and LW wheels.
-39k miles as of this writing
-Purchased new 10/30/17
-Stock suspension
...with basic bolt-ons, "the little IS20 that could" makes 330whp/380wtq SAE, using Ed's brilliant OTS files from EQT
~3100lbs after full exhaust and LW wheels.
-39k miles as of this writing
-Purchased new 10/30/17
-Stock suspension
...with basic bolt-ons, "the little IS20 that could" makes 330whp/380wtq SAE, using Ed's brilliant OTS files from EQT
Power relevance - car flies aggressively into corners during high speed runs with my local car club. It definitely carries more speed than a stock output GTI.
This power + sticky tires uncovers many weaknesses in the stock suspension.
ABOVE: "Stormy". A stunning, low-key, bi-racial Mexi-German street fighter. On stock suspension. ...Let's change that.
Location: Central Texas. Mostly flat. Some lovely hill country outside town. Some punishing roads due to shifting land/soil and ultra-heavy commercial trucks trampling them hourly.
Vehicle use/driven: conservatively 80% of the time in daily use. Very assertively the other 20%. Carries both of my kiddos around in the back regularly.
When they're not with me, it's a personal jet pack.
Road quality: above average, but not great. Definitely not German-grade (they invest heavily in their roads and transit systems).
Our roads in TX are typically better than what the folks up north live with (I'm grateful). LEAGUES better than neighboring AR and LA.
Still, in TX we have lots of unforgiving/unexpected dips, poor construction areas, Dunning-Krueger drivers with high confidence and no skill, and horrendously, unexpectedly steep driveways that try to twist and bend lowered cars.
So suspension quality and useful travel is important.
Wheels & Tires: Since 9/2021 and ~27k miles - Neuspeed RSE10s, 18x8.5" wrapped in 245/40R18 Michelin PS4S
Prior to 9/2021, the car ran a 225/40 PS4S on stock 18x7.5" Austins, installed 10/2018, and for a tiny, narrow size: they were amazing.
Good tires solved many problems and bad manners from the OE Pirellis.
Control suspension setup:
-BONE STOCK, non-DCC suspension. Pic in the beginning shows how she currently sits.
-Stock height with no other suspension changes this entire 5-yr period, except for the RSB and HD endlinks.
For Test #1 , we went from 20mm stock rear sway bar to a 25.4mm (1") APR "hollow" rear bar.
I say it in Dr. Evil air quotes because the bar is beefy and "feels" solid. I didn't know otherwise until I revisited the product page...
No other changes at that time. Ran it in this configuration in perpetuity. Results covered below.
Test#2, upgraded the RSB end links to a higher quality, rigid steel link with greaseable joints. No other changes were made besides greasing the poly RSB bushings.
Test Notes: Body roll was essentially invisible to me for the first year of ownership, as it ran the stock 225/40 Pirellis that made me fear for my life on curving roads. I never approached the suspension's limits, as the factory tires were the weakest component in road handling.
So all of the feedback here will focus on immediately before/after the rear sway bar, and before/after the endlinks. Sticky tires were present in both scenarios.
Test #1)
I installed a 25mm APR rear sway 1/2020 @ ~19-22k miles to reduce body roll, without lowering the ride height and altering the center of gravity. Retained stock end links thinking they would keep the ride compliant while saving money.
Pics above and below showing the stock 20mm bar, which looks like a large ballpoint pen you'd hold with two fingers.
Result: Immediate improvement from the RSB, I was both impressed and smiling like an idiot. Everything I had read from others was bang-on accurate.
I wanted more curvy roads to test it on!
A New Problem:
Eventually (a year later), the honeymoon had to end. The car still felt unsatisfactory during hard corners and even simple lane changes. "Slosh" could be felt.
My driving habits hadn't changed, nor had my geography. But my GRIP had gotten BETTER from the switch to wider, lighter wheels and tires.
This added grip meant more speed was being generated and negotiated in turns, revealing additional weaknesses. And the slosh/roll drove me nuts.
Please recall: RSB installed @ 19k miles. Today we’re approaching 40k miles and 2.X years of spirited use. The car was beginning to *feel* like it was back on the stock rear bar in terms of handling and body control.
Theory: Stock rear end links were deflecting more than forecasted, and/or my I'd outgrown their capabilities.
And so, gratefully we have...
Test #2)
This past week, 10/23/22 @ 39k miles, I finally replaced the stock phenolic “plastic/nylon” RSB end links with these Moog HD units, freshly greased. These had actually been sitting patiently in a box for [longer than I will admit publicly]
Part# K750809 (x2) - Part info in detail here:
Variable: I also cleaned and re-greased the RSB bushings completely. These had had given me issues for the last 18 months, especially on cold days, and over speed bumps or dips, where the bar and bushings would creak like an old Honda in need of struts and mounts.
NOTE/CAUTION: The RSB/bushing cleaning required removing the entire RSB and its mounts, but did not require removing the wheels and tires.
Snaking it out with the catback exhaust still in place is a notable PITA, but possible if you're patient and careful, and if you remove the brackets from the bushings prior to doing so.
BE CAREFUL around the headlight level sensor on the driver's side when you are doing this!
That part is expensive and semi-fragile for folks with the factory lighting pack on their cars (SE, Autobahn & Golf R owners have this standard). It runs from the LCA to a fixed point on the rear subframe/body.
For greasing the RSB bushings, I used a thinner, proven white lithium grease this time, instead of the thick, tar-paste clear suspension grease supplied by many polyurethane bushing companies. This worked much better. More on that in #7 at the end.
Everything back together, torque verified on all fasteners, car back down on ground. Test drive time.
Test #2 Result: RSB End links
Sweet honey BBQ! Only good things to report. See below.Post-repair test drive: NIGHT and day improvement. Everywhere.
Not a placebo. I'm old, worn, and very in-tune to how a car feels and behaves.
The GTI's suspension actually softened up (from impacts and harshness) in a positive manner compared to before, when the rear SB bushings and bar were binding/restricted. I didn't realize how bad the dry bushings were on the RSB, and how much they were killing the ride quality.
Disclaimer: this added comfort and compliance has nothing to do with upgrading the end links, which are mostly passive when the car is driving straight.
The rear sway is now free to do its job without dirt, grime or moisture keeping it from rotating properly inside the bushings during normal suspension travel, compression and rebound, resulting in the compliant ride I'd forgotten this car had.
Body roll post-RSB links is insanely controlled in cornering and lane changes now, compared to the stock plastic RSB end links. Even in the presence of the stock height springs and all-stock suspension (dampers, bushings, etc. are all original).
I can be precise and controlled with corner entry; no sudden steering inputs as I set it up...or I can chuck it into the corner like an Evo X (with no occupants or loose stuff in the car), and it does what it's supposed to without losing its composure and falling to pieces.
Overall: Car feels smooth again!
Like a brand new BMW 1 or 2-series. Those who have owned or driven one of these will know what I mean: they are the gold standard, along with the Porsche Cayman and 911, for athletic handling without a harsh, punishing ride.
CONCLUSIONS, Wrap-Up: ~18k mile, 3-yr comparison...
(stock...to bigger RSB...to RSB + HD end links)
(stock...to bigger RSB...to RSB + HD end links)
1) A fatter 25.4mm rear sway bar on a FWD car with stock suspension is a HUGE improvement in handling and roll control, with little to no discernible loss of ride quality in real world subjective testing on local public roads.
2) Later, adding upgraded HD rear endlinks to the Mk7 MQB (with a larger RSB already employed) created even greater body roll control and vehicle confidence; still with no loss of comfort or compliance, and no added noises.
3) It is unlikely you will find the car's suspension limits until you have abandoned the stock all season tires, and upgraded your wheels and/or tires to something stickier.
4) The grippier your tires, the more speed you'll carry into the corners; the more weight will be transferred to the outside tires of the car; the more you will become aware of any inherent body roll through natural inertia.
...Just a tire upgrade can reveal suspension weak points.
5) Any time you run a poly aftermarket bushings or component, check it annually for wear, squeaks, binding, etc. (ed. - I won't make this mistake again!)
6) The added expense of upgrading your rear end links at the same time can be justified by the further improvements to the car's body control.
7) This upgrade does not bind the car/suspension from doing its job on normal public roads, so long as the bushings are kept lubricated.
...White lithium grease in a tub worked better than traditional "bushing paste", and is what I have always used on cars prior to the APR RSB mod.
Closing/Personal Tech Thoughts
-SuperPro and Moog have been the go-to value adders of end links for a long time on these cars. Zero NVH or harshness from users. Very good quality parts.
-Paint your Moog links before install if you live somewhere with harsh winters and salted roads.
-Don’t be afraid to do it all at once (RSB + ELs) if you can afford to! I will advise all customers accordingly moving forward.
-If you ever get rear suspension creaks or pops after a RSB mod, check the bushings first, and make sure your torqued your bolts with the suspension loaded and compressed to its resting ride height.
-The RSB did not require this preloading (as a control arm would). I simply verified it could rotate smoothly by hand, then performed a final torque to the 4 bolts holding the bracket to the rear subframe.
-To service the RSB bushings, you need to remove the bar and set it all out on the ground or on a bench, but it's completely worth it. I did not even remove the wheels for this job. If it is greased properly, hopefully you can get years of trouble-free service from your bar.
Golf R owners - please chime in with your experiences running JUST the RSB and links as your upgrade prior to doing the front SB as well.
Interested to hear your take, since you folks have AWD, 200lbs more curb weight, and a slightly different driving dynamic when chunking the car through corners and turns.
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