GOLFMK8
GOLFMK7
GOLFMK6
GOLFMKV

Beginner’s Guide / Tips for Buying a Street-Based Suspension

GTIfan99

Autocross Champion
Location
FL
Yeah bump stop / bump spring tuning is not talked about alot but is fertile ground for suspension tuning. I spent some time doing so on the rear suspension and it's a great solution having one spring rate for street and another spring rate for autocross.

I won't consider dampers with internal bump stops as it makes bump stop tuning more complex. That said, the guy Shaikh at Fat Cat motorsports has a youtube video on how to modify a Bilstein internal bump stop. IMO it's simpler on a Koni. But in your case, you might explore modifying or replacing your internal bump stop with a shorter firmer version to increase your bump travel.

You can also raise ride height with spring rubbers, but it will increase your spring rate in the process. If you only need it for track, that might be worth exploring.
I cut my front factory bumpstops after a year of getting into the stock bumpstops under braking and creating terminal understeer. Once I stopped getting into the bumpstops immendiately under braking, you could actually turn the car. Crazy how that works. lol.
 

tigeo

Autocross Champion
I cut my front factory bumpstops after a year of getting into the stock bumpstops under braking and creating terminal understeer. Once I stopped getting into the bumpstops immendiately under braking, you could actually turn the car. Crazy how that works. lol.
It's interesting that for me on B8s and H&R Sports based on my calcs in my table above, I am "in" the jaunce bumpers at rest/static ride height. They really are just part of the spring as I am looking at it. I'm only not in them at full droop/extension....not much "bumpstop-free" travel for me! If I cut them the car would sit even lower as I interpret it b/c the effective spring rate would be lower.
 

GTIfan99

Autocross Champion
Location
FL
OK, that jives with what Koni is telling me. Thanks. Would be interesting to have the OEM dampers as a comparison.
Overlay a soggy noodles dampening force and you'll have your comparison. lol.

I wish I still had my stock shocks so I could show you. You can easy compress and extend the shaft with no effort with 2 fingers. The Koni will give you a workout, even on soft.

The base shocks have almost no dampening effect even new. It's crazy.
 

tigeo

Autocross Champion
Overlay a soggy noodles dampening force and you'll have your comparison. lol.

I wish I still had my stock shocks so I could show you. You can easy compress and extend the shaft with no effort with 2 fingers. The Koni will give you a workout, even on soft.

The base shocks have almost no dampening effect even new. It's crazy.
Mine were quite firm, quite a bit more than 2 fingers. Start at about 8 min on my video here:

 

xXDavidCXx

Autocross Champion
Location
AZ
Car(s)
2017 GTI SE DSG

GTIfan99

Autocross Champion
Location
FL
Mine were quite firm, quite a bit more than 2 fingers. Start at about 8 min on my video here:

Mine had 20k miles, mostly lowered and half a dozen track days and 30 autocrosses on them, about half and half stock springs and lowering springs. They did not rebound, at all, even after cycling. Maybe VW went with cheaper shocks with 7.5's, but they were done.
 

GTIfan99

Autocross Champion
Location
FL
@GTIfan99 The human hand cannot replicate the appropriate shock speed to activate the internal valving to create the opposing force you are looking for.
The fronts were collapsing into the bump stops creating the worst understeer I've every felt in a car after about 6 months of heavy autocross and tracking. I was not imagining the change, it was drastic. Codriver felt it too.
 

xXDavidCXx

Autocross Champion
Location
AZ
Car(s)
2017 GTI SE DSG
The fronts were collapsing into the bump stops creating the worst understeer I've every felt in a car after about 6 months of heavy autocross and tracking. I was not imagining the change, it was drastic. Codriver felt it too.
Maybe I misunderstood.

You are saying you compressed the shock and it didn't rebound?
 

GTIfan99

Autocross Champion
Location
FL
Maybe I misunderstood.

You are saying you compressed the shock and it didn't rebound?
Yes. That's what I'm saying, and they collapsed into the bumpstops after about 6 months on the lowering springs. It didn't help that the apr rear springs created a lot of rake.
 

SPLR337

Go Kart Champion
Location
New York
Car(s)
2019/1997 GTI
Just got my car back from Tyrolsport.

Last year I installed Bilstein B8s, DG springs, 24mm rear H&R sway bar w/ Moog end links, TT pads in the rear. I also went with a set of 18x8 et45 Rse10 with PS4S tires in the factory size. Very satisfied but needed something more up in the front.

Had them install the Eurosport camber kit, H&R 26mm front sway bar, and their own dead set kit for the front subframe. After getting the car back yesterday, it really seemed like it was just what the car needed to feel how I wanted. In my opinion, the front sway bar was a great addition. The camber kit added no NVH (daily driven in NYC), and no clunks from the subframe. Everything works very nicely together. While it isn't a very aggressive setup, it is great for a spirited and fun daily driver. Very comfortable and quiet. I do need to add spacers to the front now due to the camber, the top of the wheel tucks a little more than I had expected.

Overall I wouldn't change a thing, and I would do this same setup a over again. I have contemplated the H&R OE Sport springs, but I am not sure if it is worth the time and effort to make the change.
 

ZERO815

Autocross Champion
Location
Köln Germany
Car(s)
2017 GTI SE DSG
I've posted this elsewhere but curious to get @Hammersticks opinion:

R.gif



So I decided to nerd-out as I do and do some suspension measurements to figure my droop and bump travel. My setup is GSW w/4Mo + DSG, Bilstein B8s, Eurosport Street camber mounts, H&R Sport springs. Beyond those primary bits, I have H&R f./r. upgraded sway bars (27mm/25mm, respectively), 034 adjustable f. end links, Moog r. end links, Superpro aluminum LCAs, and the Tyrolsport f. deadset kit and 034 r. subrame inserts. What I did was measure the static level by doing wheel lip to fender lip both f. and r. and then jack up each until the wheels were off the ground and take the measurements again. Both were the same; 3.5" so 3.5" droop/extension travel. Next I was able to contact Bilstein and get the specs on each damper including total shaft travel/length and for the fronts the internal jaunce bumper length. I was able to find the r. jaunce bumper length by part no. Then I did some video testing to measure the actual bump travel up front using a speed bump. Data below:

View attachment 258989


So bottom line is, I don't have nearly as much travel up front as I thought I would have. Would be ideal to be at a 70/30% bump to droop ratio in my mind but I'd need to be able to pre-load the springs a bit to get that travel in that range and increase my ride height a bit - the B14/16 coilovers would allow me to do that. Going with the coilover that have adjustable bodies would remedy this more easily as you can set the bump/droop with preload independently of the ride height but of course you can put the tire through the fender with those too if you go too low. I noted I lost 0.25" of f. ride height after the LCAs/camber mounts/etc. so not sure there - maybe that changes the geo enough to do that? I can't see how else that would happen as the spring rate/strut length sets your ride height. I'd happily add 0.25 back to gain a little more bump travel up front. The fact that you ride on/into the jaunce bumper is news to me but based on the info from H&R below, makes total sense...really just addes progressiveness to the coil springs. Also makes me wonder if you can tune the springs a bit more (increase the rate) by just doing some upgraded jaunce bumpers? Finally...just how far can you compress a jaunce bumper? 100% of it's length is not possible. Based on he video work I did it looks to be ~30% of it's length compresses until you are fully "bottomed out" and feel a thud.

Here's the video. I just taped a measuring tape I made to the fender and zero'd it on the lip of the wheel. Looks to move 1" and I'm assuming that the wheel movement to strut shaft movement is 1:1 for this but that may not be accurate but the math on the numbers bilstein gave me works and 30% compression of the foamy makes sense:

https://youtube.com/shorts/8NDWFYTMBXw?feature=share


Post was more informational/to spur supension nerd talk so have at it!

Some good reading from H&R on this topic here:

https://www.hrsprings.com/technical/micro-cellular-jounce-bumper

Excerpt that seems to back my measurements/that my car sits on the foamy jaunce bumpers:

Capture2.JPG



Also, Steve Dinan has some good info if your'e willing to spend the time on this podcast re suspension and jaunce bumpers:


Interesting topic. Took some measurements on my '17 GTI, and extra B8 struts I have laying around in my garage.

My car sits at 345mm center of wheel to fender. I have measured 205mm from inside of the strut tower to the middle of the sway bar link bolt at ride height, and 293mm at full drop.

--> Extended 293mm - ride height 205mm = 88mm into shock travel. Since it takes 69mm from extended to jounce bumper touch at my ride height I'm riding the bump stops by 19mm already.

- How much travel is left? I know bump stops are typically tested at 5kN for fully compressed. So did I, the 65mm jounce bumper is only 15mm long at around 5kN. --> 50mm of jounce bumper travel is available.
- Can you cut the jounce bumper? Yes, with a sharp knife. Based on my measurements approx 4mm of the chrome tube remains at 5kN compressed length. You don't want the non-chromed-section to go into the seal that's at the top end of the yellow outer tube to keep moisture out of the shock. Under 5kN the remaining jounce bumper height is only 23% of its original height. Assuming it compresses equally, if you shorten the jounce bumper by 17,4mm you gain 4mm of total travel, and the chrome tube will be still sealed (4mm / 23% = 17,4mm).
- From my own experience I know even 5mm "out of the jounce bumper" makes a big difference. As soon as these shocks go back into my car I'll try -5mm 1st, -10mm 2nd, ... . With lowering springs I'm down to 45min for uninstalling and installing the fronts. With a proper spring compressor it doesn't take long to make the bump stop adjustments ;-)

20220902_B8_JB.jpg
 

tigeo

Autocross Champion
Interesting topic. Took some measurements on my '17 GTI, and extra B8 struts I have laying around in my garage.

My car sits at 345mm center of wheel to fender. I have measured 205mm from inside of the strut tower to the middle of the sway bar link bolt at ride height, and 293mm at full drop.

--> Extended 293mm - ride height 205mm = 88mm into shock travel. Since it takes 69mm from extended to jounce bumper touch at my ride height I'm riding the bump stops by 19mm already.

- How much travel is left? I know bump stops are typically tested at 5kN for fully compressed. So did I, the 65mm jounce bumper is only 15mm long at around 5kN. --> 50mm of jounce bumper travel is available.
- Can you cut the jounce bumper? Yes, with a sharp knife. Based on my measurements approx 4mm of the chrome tube remains at 5kN compressed length. You don't want the non-chromed-section to go into the seal that's at the top end of the yellow outer tube to keep moisture out of the shock. Under 5kN the remaining jounce bumper height is only 23% of its original height. Assuming it compresses equally, if you shorten the jounce bumper by 17,4mm you gain 4mm of total travel, and the chrome tube will be still sealed (4mm / 23% = 17,4mm).
- From my own experience I know even 5mm "out of the jounce bumper" makes a big difference. As soon as these shocks go back into my car I'll try -5mm 1st, -10mm 2nd, ... . With lowering springs I'm down to 45min for uninstalling and installing the fronts. With a proper spring compressor it doesn't take long to make the bump stop adjustments ;-)

View attachment 259791
Great info! One question...if you trim the jaunce so you aren't "in" it at rest won't this cause the ride height to drop because the spring rate is now lower at the resting position?
 

ZERO815

Autocross Champion
Location
Köln Germany
Car(s)
2017 GTI SE DSG
Theoretically yes. However I guess it’s a very small added spring rate for the first 10mm - 15mm. Typically the elastomer springs have a very soft start, and then they get very progressive. As you can see the Elastomer buffer has 3 groves, they „collapse“ first very easy.
 

Boloc

New member
Location
NC
Car(s)
20’ GTI
Not sure if this has been covered, but I have a noob question.

I am thinking about lowering my GTI 0.75”-1.25” on coilovers. During the alignment, is there enough camber adjustment in the OEM suspension to correct the camber to avoid going through tires prematurely?
 

GTIfan99

Autocross Champion
Location
FL
Not sure if this has been covered, but I have a noob question.

I am thinking about lowering my GTI 0.75”-1.25” on coilovers. During the alignment, is there enough camber adjustment in the OEM suspension to correct the camber to avoid going through tires prematurely?
That depends on your coils, but minor camber changes aren't going to wear your tires. Toe kills tires.
 
Top