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Under hard braking, car gets “floaty”.

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Old 01-28-2022 | 11:19 AM
  #16  
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Agree but putting it at # 1. of 3 possibilities is considerably different from 'not ruling anything out'.
Old 01-28-2022 | 11:25 AM
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Read what I wrote again. Just a list of possibilities to review bud. Unless we review the components in question and drive the car, tough to know.
Old 01-28-2022 | 11:27 AM
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Last year I noticed that the ABS tended to come on at really low speeds, in the front. Michelins only had 1000 km on them. With more experience, I realized it was happening on rough pavement.
Another issue was the rear end "wallowing" in some situations - most often accelerating through a gradual uphill curve (like an entry ramp). I didn't do anything about either, planning on first addressing the significant bore scoring...
When I had the engine done, I got new engine mounts. Some of that wallowing was addressed. Then I did the shocks all around and both issues were gone. I'm replacing other suspensions bits gradually, but the new shocks made the biggest difference.

I like the motorcycle analogy - whenever I felt twitchiness under hard braking, I would first blame the mechanic before questioning my technique. No matter what, it always seemed to be my own fault...
Old 01-28-2022 | 11:41 AM
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Originally Posted by Emefef
Last year I noticed that the ABS tended to come on at really low speeds, in the front. Michelins only had 1000 km on them. With more experience, I realized it was happening on rough pavement.
Another issue was the rear end "wallowing" in some situations - most often accelerating through a gradual uphill curve (like an entry ramp). I didn't do anything about either, planning on first addressing the significant bore scoring...
When I had the engine done, I got new engine mounts. Some of that wallowing was addressed. Then I did the shocks all around and both issues were gone. I'm replacing other suspensions bits gradually, but the new shocks made the biggest difference.

I like the motorcycle analogy - whenever I felt twitchiness under hard braking, I would first blame the mechanic before questioning my technique. No matter what, it always seemed to be my own fault...
Good info. Especially on the motor mounts. I am replacing mine in 2 weeks. Curious as to how the overall dynamics change since I am running the original mounts (57k) Then I will do the same with the transmission mount at a later date. Curious on any changes to car dynamics that each component has on the street and track. Hence staggering the replacements.
Old 01-28-2022 | 01:56 PM
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OP - Welcome! First suspect is always tires. Only contact patch with the ground. What’s their story? Brand, type, pressure you’re running, age, etc. If it brakes straight and is controllable, I’d start there. Might want to take it to Protech if you get stumped. They rebuilt my engine years ago.

Last edited by hatchetf15; 01-28-2022 at 01:59 PM.
Old 01-28-2022 | 02:54 PM
  #21  
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Originally Posted by Nate.Evans;[url=tel:17935204
17935204[/url]]It doesn’t pull to the left or right, it just feels super vague and floaty under HARD braking. Think slowing down as quickly as possible from 100 down to 30.

If you’ve ever ridden a motorcycle, the biggest analogous explanation is like if the head angle is too steep, it all of a sudden feels twitchy when you brake really hard.

The car exhibits no other odd symptoms, it feels nice and tight when accelerating and in corners, but HARD braking just feels sketchy. Under normal braking there’s no issues.

I’m guessing it’s an alignment issue or maybe a blown shock? I got a look under the car and in the fender wells and the shocks don’t appear to be leaking or weeping.
There’s probably nothing wrong with your suspension or shocks or anything. Your car is acting normally. HARD braking should be done in a straight line. And your suspension and shocks have nothing to do with that after initial bite, and before brake release. Unless the road is uneven. If you try to turn the wheel at all during super hard braking, the rear end is going to feel like it’s on ice, so that’s why people trail brake in slow corners at slower speeds in this car, and not hard braking at high speed.

Yes, alignment, tire pressure have more to do with this than the suspension.

The 911 floaty feeling is what gives you pinpoint control over where you want the car to go next in a turn.

Btw, the front end of your car could also feel floaty under WOT in anything other than a straight line. Some people come and post about this, and yes, alignment and tire pressures are mostly the issue, but the road is next, especially elevation changes combined with turning at high speed.


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Old 01-28-2022 | 03:34 PM
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Originally Posted by hatchetf15
OP - Welcome! First suspect is always tires. Only contact patch with the ground. What’s their story? Brand, type, pressure you’re running, age, etc. If it brakes straight and is controllable, I’d start there. Might want to take it to Protech if you get stumped. They rebuilt my engine years ago.
They're the one doing the alignment on the 7th...kinda just bracing myself for the worst case scenario.

Originally Posted by Mike Murphy
There’s probably nothing wrong with your suspension or shocks or anything. Your car is acting normally. HARD braking should be done in a straight line. And your suspension and shocks have nothing to do with that after initial bite, and before brake release. Unless the road is uneven. If you try to turn the wheel at all during super hard braking, the rear end is going to feel like it’s on ice, so that’s why people trail brake in slow corners at slower speeds in this car, and not hard braking at high speed.

Yes, alignment, tire pressure have more to do with this than the suspension.

The 911 floaty feeling is what gives you pinpoint control over where you want the car to go next in a turn.

Btw, the front end of your car could also feel floaty under WOT in anything other than a straight line. Some people come and post about this, and yes, alignment and tire pressures are mostly the issue, but the road is next, especially elevation changes combined with turning at high speed.
Yeah, I've driven a few before, but this is just the first that's mine. The hard braking is definitely done in a straight line, being done before approaching the corner and it just feels really vague and the rear end feels wallowy....kinda hard to explain. Conversely, I hop in the Macan turbo and jam on the brakes and it feels PLANTED. I'm hoping this is is just an alignmen thing.....

Originally Posted by GC996
Good info. Especially on the motor mounts. I am replacing mine in 2 weeks. Curious as to how the overall dynamics change since I am running the original mounts (57k) Then I will do the same with the transmission mount at a later date. Curious on any changes to car dynamics that each component has on the street and track. Hence staggering the replacements.
I'm probably going to replace those here before the alignment just because...simple enough job...then when my IMS solution gets installed on the 14th, have them replace the transmission mount.
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Old 01-28-2022 | 06:06 PM
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You didn't tell us whether you waited for the snow to clear before these tests...or did you do them on the slippery concrete in the underground parking garage?
Old 01-28-2022 | 07:26 PM
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😂 there’s no snow on the ground.
Old 01-28-2022 | 07:38 PM
  #25  
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Originally Posted by hardtailer
You're most probably experiencing small and varying toe-change due to worn rubber bushes in the suspension control arms combines with the high longitudinal braking forces

I always think of this video. Bushings are still on my list because of it.

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Old 01-28-2022 | 08:15 PM
  #26  
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Originally Posted by Nate.Evans;[url=tel:17936472
17936472[/url]]They're the one doing the alignment on the 7th...kinda just bracing myself for the worst case scenario.



Yeah, I've driven a few before, but this is just the first that's mine. The hard braking is definitely done in a straight line, being done before approaching the corner and it just feels really vague and the rear end feels wallowy....kinda hard to explain. Conversely, I hop in the Macan turbo and jam on the brakes and it feels PLANTED. I'm hoping this is is just an alignmen thing.....



I'm probably going to replace those here before the alignment just because...simple enough job...then when my IMS solution gets installed on the 14th, have them replace the transmission mount.
Sounds like something is broken then, as you seem to know this stuff better than most. You’re onto the right clues: alignment, shocks, tires, etc.
Old 01-28-2022 | 08:21 PM
  #27  
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OP - What shoes are on your car? What model, dates, depths and pressures at all 4 corners? What you describe could mostly be tires and/or pressures. This question just to help rule them out as a primary. For example, if your rears are set at drifting pressures, then guess what. Things like that.

Last edited by hatchetf15; 01-28-2022 at 08:25 PM.
Old 01-29-2022 | 10:27 AM
  #28  
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Originally Posted by hatchetf15
OP - What shoes are on your car? What model, dates, depths and pressures at all 4 corners? What you describe could mostly be tires and/or pressures. This question just to help rule them out as a primary. For example, if your rears are set at drifting pressures, then guess what. Things like that.
All 4 tires are brand new Sumitomo Z5s, 50psi all around per Sumitomo’s tire chart. Tire dates show all 4 tires are all less than 9 months old.
Old 01-29-2022 | 10:34 AM
  #29  
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Originally Posted by Nate.Evans
All 4 tires are brand new Sumitomo Z5s, 50psi all around per Sumitomo’s tire chart. Tire dates show all 4 tires are all less than 9 months old.
Porsche PSI recommendations are more important than Sumitomos.

I don't believe it's causing your issue, but man 50psi square is not ideal.
Old 01-29-2022 | 10:35 AM
  #30  
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Don't know the tires, but thats a lot of tire pressure.


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