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Suspension measurements and surprising findings on my Sportwagen - B8s/H&R Sport setup

tigeo

Autocross Champion
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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:

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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:

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

 

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El_bigote_AJ

Autocross Champion
Location
Las Vegas
Car(s)
2019 GTI bunny
For some loosely unrelated reference, my “superlow” airbags have about 4” of “travel” (really just range) max when I compare full air out (fender to 18” wheel lip is at 1/8” gap,lol) to full maxed height

so yeah… it’s pretty stiff at ride height or else car would be full bashing the inner fenders.

Interesting fact I learned with the new bags - at full airout front and back the car will still roll 😂
 

tigeo

Autocross Champion
For some loosely unrelated reference, my “superlow” airbags have about 4” of “travel” (really just range) max when I compare full air out (fender to 18” wheel lip is at 1/8” gap,lol) to full maxed height

so yeah… it’s pretty stiff at ride height or else car would be full bashing the inner fenders.

Interesting fact I learned with the new bags - at full airout front and back the car will still roll 😂
Interesting and thanks for that - I don't know much about bags beyond how an air springs works from my mountainbike suspension knowledge. 4" all-in isn't much to work with. Super low looks cool but it's not going to be the highest performaning suspension.
 

El_bigote_AJ

Autocross Champion
Location
Las Vegas
Car(s)
2019 GTI bunny
Yeah, my other bags had around 5.75” of travel, just these now one have tiny air springs so the ride height can be silly low and still stiff enough to not bottom out. But it’s very much a rather jarring ride (like a shifter cart 😂) on anything but beautifully smooth surfaces.


Keep in mind 4 inch’s from this - lol. (Also that’s just max lift you can’t really drive in that cause it’s solid with not even 1/8” of suspension bump or droop travel fully aired up) I want to get a go pro and mount it to the side to really see how much movement I even get when driving at ride height

AFDFB4D2-7865-4AD1-85B9-F02745EF9AC9.jpeg

It’s stiff and yeah I know performance, clearance, comfort all are effected, I don’t have the bags cause all or any were the main priority, they all just factors in chasing a balance for the end image of my art project 😂.
 
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tigeo

Autocross Champion
Yeah, my other bags had around 5.75” of travel, just these now one have tiny air springs so the ride height can be silly low and still stiff enough to not bottom out. But it’s very much a rather jarring ride (like a shifter cart 😂) on anything but beautifully smooth surfaces.


Keep in mind 4 inch’s from this - lol. (Also that’s just max lift you can’t really drive in that cause it’s solid with not even 1/8” of suspension bump or droop travel fully aired up) I want to get a go pro and mount it to the side to really see how much movement I even get when driving at ride height

View attachment 258862
It’s stiff and yeah I know performance, clearance, comfort all are effected, I don’t have the bags cause all or any were the main priority, they all just factors in chasing a balance for the end image of my art project 😂.
Yeah I've always thought about the air spring and the more air pressure you put in the higher the ride height but also the higher the spring rate! Just like a mountainbike fork and shock. Effectively preload except on a coil spring preload doens't change the spring rate.
 
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