Street Touring Hatchback (STH) discussion/setup

[bfury5]

You're still missing the point.

You set the shock overall length with the wheel stuffed at full bump.

If you adjust the shock height any longer then you are giving up potential uptravel.

If you adjust it any shorter you risk tire to fender(or whatever) contact.

You set the shock length with the lower ring and leave it.

You run the upper ring up or down wherever you need to set proper ride height. All that setting the shock length first does is ensure you have as much usable bump travel as possible.

You will only have as much useful droop as your spring at full extension minus whatever it is at ride height.

Also like I said, if you're corner weighting using the lower collar, your bump stops will be hitting at different times left vs right.

Having "loose" springs does not matter. You don't want preload unless your rates are so soft vs your available shock travel and lengths which may dictate it. If you're running higher spring rates and they're preloaded you are giving up some of the little bit of droop travel you already lack.

Having large amounts of preload also does other weird things because if you have a 10k spring preloaded 5mm, that means it takes an initial force of 50 kg(110 lbs) before the spring even starts compressing (in the case of a tire leaving the ground or having very little weight on it. This means the tire contact patch gets "shocked" (pardon the pun) with an undamped 110 lbs coming down onto it. Of course again this is all talking in 1:1 MR for simplicity sake, but applies to the front almost directly. The rear requires some math.

Now if you're running a 250 lb spring on a 1000 (sprung) lb corner, it will eat up 4 in of overall travel just to sit at ride height. This is a major problem if you have only 6in of travel like a lot of the cheap Chinese shocks. This means you have 4 in of droop travel, 2 in of bump travel, which will ride like crap and bottom out everywhere (remember this is also without bump stops factored in).

If you preload the spring by 0.5in, it now requires an initial force of 125 lb before the shaft starts moving. So with 875 lb left to support, the shock only compresses 3.5 in, leaving you with 2.5 in of bump travel.

Notice how the exact amount you preloaded directly gets turned into more bump travel (and less droop)? The spring still compresses the same amount, but you're using a different portion of shock travel to achieve it. If you preload it less, it'll lower your ride height, if you preload it more, it'll raise it. (Note that with higher rates the springs will be "loose" at full droop. This is not a problem, though you have the option to run helper or assist springs which is a whole other can of worms to get into).

With rates that low vs the corner weight, I would not corner weight it my method. It needs more shock travel, plain and simple. It's unusable without preloading the hell out of it, or having basically no bump travel. If you preload it by 2in, it'll do all kinds of goofy stuff too - it'll require 500 lbs to even start compressing. Lift a tire and come back down it'll be very abrupt.

I never set my car as low as it could have gone. I figured out my max bump, and based on spring rates and corner rates figured I needed 2 in min bump travel, so set my ride height about 2.75 above max bump based on roll centers (which had been corrected with knuckles, otherwise it'd be another inch+ higher).

This ensured I was running at the proper height, with as much bump travel as physically possible, and because the rates were so high, my ~1 in of sprung down travel was fine, with a bit of leftover shock travel where the spring could unseat. There's no getting around that with a 700lb spring on a 730 lb corner. The tire constraints vs shock length did not permit adding a helper/assist spring to play around with, otherwise I would have tested that.

I don't believe I'm missing a point, but for the sake of this thread I am going to bow out of this.

 

[deleteaccount]

What’s going on. I’m confused.

 

[GTIfan99]

What’s going on. I’m confused.

We're overcomplicating how to make our economy cars drive around cones.

Just enjoy it.

 

[GTIfan99]

You're still missing the point.

You set the shock overall length with the wheel stuffed at full bump.

If you adjust the shock height any longer then you are giving up potential uptravel.

If you adjust it any shorter you risk tire to fender(or whatever) contact.

You set the shock length with the lower ring and leave it.

You run the upper ring up or down wherever you need to set proper ride height. All that setting the shock length first does is ensure you have as much usable bump travel as possible.

You will only have as much useful droop as your spring at full extension minus whatever it is at ride height.

Also like I said, if you're corner weighting using the lower collar, your bump stops will be hitting at different times left vs right.

Having "loose" springs does not matter. You don't want preload unless your rates are so soft vs your available shock travel and lengths which may dictate it. If you're running higher spring rates and they're preloaded you are giving up some of the little bit of droop travel you already lack.

Having large amounts of preload also does other weird things because if you have a 10k spring preloaded 5mm, that means it takes an initial force of 50 kg(110 lbs) before the spring even starts compressing (in the case of a tire leaving the ground or having very little weight on it. This means the tire contact patch gets "shocked" (pardon the pun) with an undamped 110 lbs coming down onto it. Of course again this is all talking in 1:1 MR for simplicity sake, but applies to the front almost directly. The rear requires some math.

Now if you're running a 250 lb spring on a 1000 (sprung) lb corner, it will eat up 4 in of overall travel just to sit at ride height. This is a major problem if you have only 6in of travel like a lot of the cheap Chinese shocks. This means you have 4 in of droop travel, 2 in of bump travel, which will ride like crap and bottom out everywhere (remember this is also without bump stops factored in).

If you preload the spring by 0.5in, it now requires an initial force of 125 lb before the shaft starts moving. So with 875 lb left to support, the shock only compresses 3.5 in, leaving you with 2.5 in of bump travel.

Notice how the exact amount you preloaded directly gets turned into more bump travel (and less droop)? The spring still compresses the same amount, but you're using a different portion of shock travel to achieve it. If you preload it less, it'll lower your ride height, if you preload it more, it'll raise it. (Note that with higher rates the springs will be "loose" at full droop. This is not a problem, though you have the option to run helper or assist springs which is a whole other can of worms to get into).

With rates that low vs the corner weight, I would not corner weight it my method. It needs more shock travel, plain and simple. It's unusable without preloading the hell out of it, or having basically no bump travel. If you preload it by 2in, it'll do all kinds of goofy stuff too - it'll require 500 lbs to even start compressing. Lift a tire and come back down it'll be very abrupt.

I never set my car as low as it could have gone. I figured out my max bump, and based on spring rates and corner rates figured I needed 2 in min bump travel, so set my ride height about 2.75 above max bump based on roll centers (which had been corrected with knuckles, otherwise it'd be another inch+ higher).

This ensured I was running at the proper height, with as much bump travel as physically possible, and because the rates were so high, my ~1 in of sprung down travel was fine, with a bit of leftover shock travel where the spring could unseat. There's no getting around that with a 700lb spring on a 730 lb corner. The tire constraints vs shock length did not permit adding a helper/assist spring to play around with, otherwise I would have tested that.

We all enjoy discussing suspension setup, but if you could dial back the "you're missing the point" and substitute "In my opinion and experience, I think xyz" then we can have great discussions.

If you're discussing suspension setup and aren't open to the possibility that there's 15 ways to skin this cat, then you might not know as much as you think.

Because race engineers with decades of experience and success can completely disagree.

Keep the dialog open, we're all learning here.

 

[B1mmer]

If any of you are interested in a set of wheels, let me know:

https://www.golfmk7.com/forums/inde...d-17x9-5x112-et42-wheels.396359/#post-7791030

Thanks - AB

 

[jmblur]

It was stupid cold today. High maybe touched 43 with 15-30mph winds. Had a few squalls of ice pellets.

Also turns out R-S4s don't really like cold weather lol. Never got more than barely warm to the touch. Still fun though for first time back this year. Definitely rusty.

 

[GTIfan99]

It was stupid cold today. High maybe touched 43 with 15-30mph winds. Had a few squalls of ice pellets.

Also turns out R-S4s don't really like cold weather lol. Never got more than barely warm to the touch. Still fun though for first time back this year. Definitely rusty.

First half looked good, late on the back half with braking and turn in.

You can see the car is loose first half, tightens up last half of run.

That happens to me in early runs too, until tires get a little heat. Just that little extra heat changes the balance of the car and it's hard to adjust mid run sometimes. Tough conditions, but like like a fun course and good driving.

 

[jmblur]

First half looked good, late on the back half with braking and turn in.

You can see the car is loose first half, tightens up last half of run.

That happens to me in early runs too, until tires get a little heat. Just that little extra heat changes the balance of the car and it's hard to adjust mid run sometimes. Tough conditions, but like like a fun course and good driving.

Yeah, that was the last of 4 and they were still that cold! Grip level was definitely a guessing game. I still struggle with the right line and amount of braking for "open" corners like the one off the runway. Definitely over-braked there consistently,found myself getting back on the throttle before the apex. Feel like there's probably 1/4-1/2 a second in line choice there I'm missing...

 

[GTIfan99]

Yeah, that was the last of 4 and they were still that cold! Grip level was definitely a guessing game. I still struggle with the right line and amount of braking for "open" corners like the one off the runway. Definitely over-braked there consistently,found myself getting back on the throttle before the apex. Feel like there's probably 1/4-1/2 a second in line choice there I'm missing...

It's hard to find a rhythm when the grip level isn't consistent. I'm just now starting to get back up to speed after chasing massive understeer all last year. A year of terminal understeer under braking killed my confidence and rhythm.

One of the guys that codrives with me periodically is stupid fast and a professional driver. He brakes earlier, harder, and for less time than I do, and getting on throttle sooner, so I'm not sure braking earlier isn't the way to go, then adding maintenance throttle, until you can accelerate out.
And same with me, I'll trying to carry more speed in the high speed sections. That's where you really cut time.

Looking good for the conditions and first event of the year.

 

[mrmatto]

One of the guys that codrives with me periodically is stupid fast and a professional driver. He brakes earlier, harder, and for less time than I do, and getting on throttle sooner, so I'm not sure braking earlier isn't the way to go, then adding maintenance throttle, until you can accelerate out.

It's funny you mention this because I noticed exactly this from a few other drivers at the FIRM event when I was working. It looked very smooth and fast.

Just speaking for myself as a novice, my tendency when I have a car with lots of understeer is to try and trail brake a little and induce some oversteer. I was trying all day long to get that down but half the time it just caused me to overcook my corner entries and often understeer more as I wouldn't have the control needed to smoothly accelerate out of the corner. Overall, it just didn't leave me with a margin of error or enough control. BUT, as I've been testing out my new rear sway, I'm getting the feeling that braking a little earlier and entering the corner with more stability is going to give me more control -- It feels like modulating the throttle mid-turn lets me modulate the level of under/oversteer. Sort of a lightbulb moment for me. Whether that's truly the fastest way or not, I don't know, but just coming at this as a very very very fresh driver, I really think your co-driver is on to something. You might read this and say "Yeah no duh you're out of your depth here" and I completely accept that

 

[GTIfan99]

It's funny you mention this because I noticed exactly this from a few other drivers at the FIRM event when I was working. It looked very smooth and fast.

Just speaking for myself as a novice, my tendency when I have a car with lots of understeer is to try and trail brake a little and induce some oversteer. I was trying all day long to get that down but half the time it just caused me to overcook my corner entries and often understeer more as I wouldn't have the control needed to smoothly accelerate out of the corner. Overall, it just didn't leave me with a margin of error or enough control. BUT, as I've been testing out my new rear sway, I'm getting the feeling that braking a little earlier and entering the corner with more stability is going to give me more control -- It feels like modulating the throttle mid-turn lets me modulate the level of under/oversteer. Sort of a lightbulb moment for me. Whether that's truly the fastest way or not, I don't know, but just coming at this as a very very very fresh driver, I really think your co-driver is on to something. You might read this and say "Yeah no duh you're out of your depth here" and I completely accept that

No, you're on the right track. I dropped 2 seconds once I stopped over driving at the last event and started trying to brake earlier, shorter time, but hard, then accelerating earlier and modulating throttle better on corner exit.

We're all masochists, autocrossing a FWD car. It take so much more skill to drive one fast as a RWD or AWD car. I know, because I came from RWD and AWD with same club. I'm consistently 5 or more spots lower in PAX in FWD. I know the car is capable, professional driver can pull out 3rd raw and 2nd pax in same car same day, so it's just my driving. lol. That's a hard pill to swallow. I feel like I'm having to relearn how to drive.

 

[mrmatto]

No, you're on the right track. I dropped 2 seconds once I stopped over driving at the last event and started trying to brake earlier, shorter time, but hard, then accelerating earlier and modulating throttle better on corner exit.

We're all masochists, autocrossing a FWD car. It take so much more skill to drive one fast as a RWD or AWD car. I know, because I came from RWD and AWD with same club. I'm consistently 5 or more spots lower in PAX in FWD. I know the car is capable, professional driver can pull out 3rd raw and 2nd pax in same car same day, so it's just my driving. lol. That's a hard pill to swallow. I feel like I'm having to relearn how to drive.

Haha masochists. Indeed. "Overdriving" is a great description. I think I found that line at the last event where I need to back it off a bit.

....aaaaand then I got a rear sway bar and now it drives like a completely different car But actually it now feels a lot like my Mazda 3 did, which was a very lively chassis that inspired tons of confidence. I regret I never got to track or autocross that car...

@jmblur Thanks for the video. I thought your run looked pretty solid considering the conditions. As a newbie, I appreciate the inspiration and just watching how other drivers do it.

 

[jmblur]

No, you're on the right track. I dropped 2 seconds once I stopped over driving at the last event and started trying to brake earlier, shorter time, but hard, then accelerating earlier and modulating throttle better on corner exit.

We're all masochists, autocrossing a FWD car. It take so much more skill to drive one fast as a RWD or AWD car. I know, because I came from RWD and AWD with same club. I'm consistently 5 or more spots lower in PAX in FWD. I know the car is capable, professional driver can pull out 3rd raw and 2nd pax in same car same day, so it's just my driving. lol. That's a hard pill to swallow. I feel like I'm having to relearn how to drive.

I'm cheating with the R, this thread is just more active than the STU threads

 

[GTIfan99]

I'm cheating with the R, this thread is just more active than the STU threads

The mk7/7.5 haldex makes you an honorary FWD driver.

 

[jmblur]

The mk7/7.5 haldex makes you an honorary FWD driver.

Not to mention the open difs...