Bottoming Out - how to tell?

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x08

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Hey guys... How do u tell if ur car is bottoming out? I'm not very good at the whole analysis thing... and how do u tell if it's the front or back?

And yes - I know the fix is to either stiffen the springs or to raise the car...

tx
 
This is a good question, and something i found myself wondering quite a few times. After playing for a long time i thought of an even better question: how much does bottoming out affect performance? Everyone knows that lowering the car greatly improves cornering, and i found that most of the time i never noticed the car ever being too low aside from rarely bouncing way in the air when clipping an apex or something. The only other thing i can think of that would make me raise the car up some is Nurburgring, with all its weird bumps, but even then, who knows? I haven't raced anything with a super low ground-clearance like the minolta or the 696b on the ring. Heck i might even venture to say that on the average track if your bottoming out someplace, your probably making up the time lost (if any) through the other 99% of the track.


-Shmak
 
I think that bottoming out is what's causing a lot of increased rear tyre wear on my minolta when I'm running on Le Sarthe. I think the rear is pushed down by the wing at high speed the car bottoms out and the back wheels spin momentarily.

Trash_Master has made a great suggestion about looking for sparks and I'm goign to try that when I get home.
 
It is possible to bottom out by two different methods:

1.) Suspension bottoming ( hitting the bump stops )
2.) Chassis bottoming ( obvious sparks, etc. )

# 1 occurring will cause the following:

• Spring rate will rise to infinity, thereby eliminating all spring / shock compliance to the tyre. Typical driving feel symptoms brought by this can be described as a "darty, squirrly car."

You know #1 is happening when the front of the car will exaggeratingly steer almost on it's own when the suspension is under hard compression ( in a dip for example ).

# 2 occurring will ( or should, GT4 isn't perfect for this ) cause the following:

• Temporary but complete loss of downforce on both front and rear ends of the car.

You know #2 is happening when nearly all aero grip is lost in a high speed corner and you go sailing off the track!
 
I have experienced a condition where a car which I thought to be nicely tuned uncontrollably darts to one side while traveling at speed over terrain changes, like the cross streets at Seattle. I took steps to remedy chassis bottoming and the condition subsided. On another occasion I had a car that also seemed to have a nice tune until it crossed terrain that had repeated bumps like washboard or rumblestrips; the car would get very steady and skitter across the obsticle like it was ice, for this car I did things to reduce suspension bottoming which seemed to help greatly.
 
Funny that something so easy to to see in real life (ya gotta have some pretty loud music or something to miss tire rubbing on the wheel well or a big ka-chunk over a bump) is so difficult to find in the game. At least for me. very rarely did i ever run into problems like this and if i did i don't think i ever attributed it to bottoming out. well now i know what to look for aside from the very obvious =] Thanks for teh info


-Shmak
 
Suspension bottoming happens when the suspension has exceeded its travel. When this happens, the load on that tire will deform the contact patch of the tire causing a loss of grip.
 
On some cars I drive I notice during accelleration the rpms "jump around" as if the car is bouncing. Is this caused by the springs bottoming out??
 
TS1AWD: I would suspect thats more related to traction than suspension bounce but I could be wrong.

I wonder if anyone else has experienced this but have a BMW M5 all tricked out. have reasonably hard suspension settings and isn't super low but about 4-5mm off rock bottom. I am still trying to get the thing to handle nicely. My problem though is that under heavy braking (end of the Fuji straight for example) it skitters, it feels basically like ABS working, thats the best description of it.

Is this fairly normal or might it be related to the fact there's not actually enough suspension travel available to take up the forward weight transfer and it's bottoming out?
 
TS1AWD
On some cars I drive I notice during accelleration the rpms "jump around" as if the car is bouncing. Is this caused by the springs bottoming out??
Click to expand...


No, however it is suspension related. It has to do with irregularities in the track surface, causing your car to 'lift' off the ground a bit. If the suspension is stiff enough, and the rebound is high enough, the car can begin oscilating a bit. What I believe is happening is as the suspension compresses and decompresses, it is putting a little bit of strain on the driveshafts, and thus making the motor work slightly harder while the suspension is compressed, thus giving you uneven acceleration.

There's a road near my house where I can simulate this behavior with while running it full throttle ;)

The other explanation is that your traction control is on ;)

-a
 
CV joints are used to keep what you just said from happining.

the reason the RPMs skip is because the car is skipping over the bumps.

the car will bounce weight off of the tires, then back on, off, on, off, etc untill just after you are clear of the bumps. if this weight transfer is enough to actually pick the wheel up away from the pavement, it doesnt even need to be off the ground, the tire will loose traction and this is what causes the sudden rise/fall of the rpms.
this means the damper is not letting the spring expand fast enough to keep the tire(s) firmly planted on the ground.... however, sometimes you have to sacrifice a few seconds of traction for the sake of the rest of the track.

this also happens when launching a car (espically FWD), but then because the engine twists in the mounts and causes wheel hop.
 
I've been wondering about the same thing since I have been dropping every car I have recently. I have never experienced anything wierd until today, well, 5 minutes ago, while playing around with the lotus Carlton. It made a strange noise that sounded like it could have been tire grinding. The car was also pulling to the right in one instance. I raised it a couple mm and stiffened the suspension a couple clicks and am about to try it again right now.

Other than the slight pull to the right the couple times, the car wasn't that much harder to control. If it gets much better with the change in settings I will be very surprised.

my setup now (after the changes) is:
rate: 7.9 8.4
height: 90 90
shocks: 8 all around
camber: 3.3 1.4
bars: 3 4
downforce is 22, 23

visually, it doesn't look like it's bottoming out. I don't think that's that important though. When I dropped my stratos it looked like the wheels should have been popping out of the hood but it didn't show any signs of weird handling that could have been bottoming out, unless I am missing something.
 
Are we seeing more "bottoming out" problems because there are so many more bumpy tracks in GT4 than GT3? Perhaps we need to be more aware of it in this game.
 
d3p0
Suspension bottoming happens when the suspension has exceeded its travel. When this happens, the load on that tire will deform the contact patch of the tire causing a loss of grip.
Click to expand...

It'll just overload that tire and break traction that way.


If you listen carefully, you can hear your suspension bottoming out when going over bumps in the road, like on Nürburgring.

It sounds like a hollow thud pretty much.

The chassis bottoming out might make a similar sound, but if you watch the replay, you'll see the sparks.

:ill:
 

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