xXDavidCXx
Autocross Champion
- Location
- AZ
- Car(s)
- 2017 GTI SE DSG
The number one question I see on these forums and the VW racers FB page I'm on is, "should I get a rear sway bar?".
The answer is, it depends.
First, read this thread, it's long, based on a Mk4 Golf, but much of what is discussed is applicable to the MK7 Golf.
https://www.golfmk6.com/forums/index.php?threads/ultimate-suspension-thread.239344/
Thread overview
1. What is Understeer?
2. Five Categories of the Suspension Enthusiast
4. The Autocross Suspension
5. The Road Racing and the Shine Real Street Suspension
6. The Grand Touring (Turismo) Suspension
7. Roll Centers and Weight Transfer
8. European Road Tests and Engineering
--------------------------------------------------------------------------------------------------------------------------------------
If you made it through that thread, congratulations!
Here is what I did about the issue of springs/bars and how to get my car to "handle"
When faced with what to upgrade to reduce body roll, you have essentially three options.
All of these options allow for reduced body roll but have different side effects.
1. Combination of bars and springs
2. Mostly springs
3. Mostly bars
Here is what these three options would look like on my car.
*** I used my specific corner weights, modifications and suspension measurements. I used an Excel spreadsheet to calculate these values for my car. Your results may vary. ***
My goal was to find the nominal bar or spring rate for options 2 or 3 that matched the front and rear wheel rate (WR) and front roll couple % of option 1. I find that for me and my setup/driver preference, I like 63% front roll couple. I could not find my online about what % is best for autocross, so your results may vary, but testing is required.
1. Combination of bars and springs (This is my daily setup for autocross)
2. Mostly springs (If I go back to OEM front and rear bars, I have to dramatically increase spring rates to keep the same wheel rate (WR) and keep the same roll couple %)
3. Mostly bars (If I max my current front and rear bar, then I can go down on spring rates to keep the same WR and roll couple %)
#1 is a good balance between relative comfort with the selected spring rates and body roll control,
#2 is tough to live with on the street and my shocks can't dampen the body with such large energy stored in the springs, but provides the most "independent" suspension
#3 is generally more comfortable on the street, but one wheel bumps are harsher and the front may lift a tire on corner exit causing issues with power down for non-PP GTIs, the rear bar won't help much either because of the soft front springs, the rear inside tire will be off the ground all the time in corners
Keep in mind these are not the only options for spring and bar rates, I just used what I have for this comparison. Also, I have additional modifications to take advantage of reduced body roll (more front camber) and an autocross alignment to increase rear rotation. Not everyone will want this level of rotation, but rotation is easily modified with less rear toe-out if required.
The answer is, it depends.
First, read this thread, it's long, based on a Mk4 Golf, but much of what is discussed is applicable to the MK7 Golf.
https://www.golfmk6.com/forums/index.php?threads/ultimate-suspension-thread.239344/
Thread overview
1. What is Understeer?
2. Five Categories of the Suspension Enthusiast
- A. Track-Based Suspensions: Autocross
- B. Track-Based Suspensions: Road Course
- C. Street-Based Suspensions: The 'Darter'
- D. Street-Based Suspensions: The GT's
- E. Street-Based Suspensions: Driving a Slow Car FAST
4. The Autocross Suspension
5. The Road Racing and the Shine Real Street Suspension
6. The Grand Touring (Turismo) Suspension
7. Roll Centers and Weight Transfer
8. European Road Tests and Engineering
--------------------------------------------------------------------------------------------------------------------------------------
If you made it through that thread, congratulations!
Here is what I did about the issue of springs/bars and how to get my car to "handle"
When faced with what to upgrade to reduce body roll, you have essentially three options.
All of these options allow for reduced body roll but have different side effects.
1. Combination of bars and springs
2. Mostly springs
3. Mostly bars
Here is what these three options would look like on my car.
*** I used my specific corner weights, modifications and suspension measurements. I used an Excel spreadsheet to calculate these values for my car. Your results may vary. ***
My goal was to find the nominal bar or spring rate for options 2 or 3 that matched the front and rear wheel rate (WR) and front roll couple % of option 1. I find that for me and my setup/driver preference, I like 63% front roll couple. I could not find my online about what % is best for autocross, so your results may vary, but testing is required.
| Front | Opt 1 (current setup) | Opt 2 | Opt 3 |
| Spring rate in/lb | 400 | 850 | 250 |
| Spring WR | 249 | 530 | 156 |
| Spring WR (body roll) | 499 | 1061 | 312 |
| Swaybar rate | 312 Hotchkis on soft | 160 OEM | 360 Hotchkis on hard |
| Swaybar WR | 295 | 151 | 340 |
| Spring WR (body roll) | 590 | 303 | 681 |
| Rear | | ||
| Spring rate in/lb | 650 | 1200 | 575 |
| Spring WR | 203 | 376 | 180 |
| Spring WR (body roll) | 407 | 752 | 360 |
| Swaybar rate | 842 O34 on soft | 333 OEM | 912 O34 on hard |
| Swaybar WR | 139 | 55 | 151 |
| Spring WR (body roll) | 279 | 110 | 302 |
| |||
| Front WR/Side | 840 | 833 | 837 |
| Rear WR/Side | 482 | 486 | 482 |
| Roll couple % front | 0.635 | 0.631 | 0.635 |
1. Combination of bars and springs (This is my daily setup for autocross)
2. Mostly springs (If I go back to OEM front and rear bars, I have to dramatically increase spring rates to keep the same wheel rate (WR) and keep the same roll couple %)
3. Mostly bars (If I max my current front and rear bar, then I can go down on spring rates to keep the same WR and roll couple %)
#1 is a good balance between relative comfort with the selected spring rates and body roll control,
#2 is tough to live with on the street and my shocks can't dampen the body with such large energy stored in the springs, but provides the most "independent" suspension
#3 is generally more comfortable on the street, but one wheel bumps are harsher and the front may lift a tire on corner exit causing issues with power down for non-PP GTIs, the rear bar won't help much either because of the soft front springs, the rear inside tire will be off the ground all the time in corners
Keep in mind these are not the only options for spring and bar rates, I just used what I have for this comparison. Also, I have additional modifications to take advantage of reduced body roll (more front camber) and an autocross alignment to increase rear rotation. Not everyone will want this level of rotation, but rotation is easily modified with less rear toe-out if required.
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