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Question on ride height

 
Old 01-14-2012, 02:25 PM
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BBMGT3
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Default Question on ride height

Hi all

I've gone through the forums and see that OEM ride height on 997.1 gt3 is 108mmF 133mmR.

I've been struggling with a bit of oversteer on my car for a long time, to the extent that I even tried a wacky -2.4R -2.2F alignment and still I was able to get the back to step out on entry/apex/exit, but understeer on turn-in lol. So I checked my ride height and its 100mmF 130mmR. I am 5mm over the OEM 25mm difference front to rear.

Am wondering if this really makes a noticeable difference... its akin to dropping the nose by 5mm from any car. Is it too small or would it be something you'd pick up on?
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Old 01-14-2012, 02:38 PM
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CRex
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These cars are VERY sensitive to rake changes in my own experience. A 5mm drop in the front will make the rear end nervous under heavy braking--happened to me in both 997.1 and 997.2 and the difference was enough for me to immediately go back to a "level" rake.

Last edited by CRex; 01-14-2012 at 09:37 PM.
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Old 01-14-2012, 03:29 PM
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Playing with rake can be a useful tool regarding weight transfer, kinematic changes and aerodynamic balance.
That being said, a 5mm difference with these height numbers is not so dramatic.. factory's tolerances are set at 5mm.







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Old 01-14-2012, 04:05 PM
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997gt3north
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Originally Posted by bmardini View Post
Hi all

I've gone through the forums and see that OEM ride height on 997.1 gt3 is 108mmF 133mmR.

I've been struggling with a bit of oversteer on my car for a long time, to the extent that I even tried a wacky -2.4R -2.2F alignment and still I was able to get the back to step out on entry/apex/exit, but understeer on turn-in lol. So I checked my ride height and its 100mmF 130mmR. I am 5mm over the OEM 25mm difference front to rear.

Am wondering if this really makes a noticeable difference... its akin to dropping the nose by 5mm from any car. Is it too small or would it be something you'd pick up on?
I had a car like that 1x - my rear R888s were shot - new tires and it went away.

If your tires have lots of miles on them / more than a couple of track days, then you may end up entirely chasing your tail trying to fix what is a tire issue. As the pros say, put on a fresh set of rubber and then start fixing what's wrong.

Personally, I just can't imagine 5mm of rake difference would make that dramatic of a difference - given the different shock setups and ride heights I have gone through recently, without issue, I should have run into this but didn't.

My guess is rear tires and then bars
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Old 01-15-2012, 01:15 AM
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Originally Posted by 997gt3north View Post
I had a car like that 1x - my rear R888s were shot - new tires and it went away.

If your tires have lots of miles on them / more than a couple of track days, then you may end up entirely chasing your tail trying to fix what is a tire issue. As the pros say, put on a fresh set of rubber and then start fixing what's wrong.

Personally, I just can't imagine 5mm of rake difference would make that dramatic of a difference - given the different shock setups and ride heights I have gone through recently, without issue, I should have run into this but didn't.

My guess is rear tires and then bars
Am on my 3rd set of new R-comp rubber (MPSC). Will fiddle with the rake a bit, see what happens...
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Old 02-22-2012, 01:53 PM
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Could someone please clarify or post pictures of what this point of reference is off my 997.1 GT3. I can't translate this into Spanish. Therefore, I'm having an issue allocating that point on the car.

Front
"From road contact surface to lower edge of hexagon-head bolt of cross-member threaded connection to the body."

&
Rear
"From wheel contact surface to the locating bore in the rear-axle side section (between toe and camber eccentrics)."

Thanks!
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Old 02-22-2012, 02:04 PM
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In case you missed the drawings:


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Old 02-22-2012, 02:23 PM
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Quick tip: I found when setting ride heights it was easiest for me to cut a wooden dowel (you can substitute whatever material you like here) to my desired height and used it to slide inbetween the two points instead of fiddling with other methods of measuring every time I crawl under the car.
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Old 02-22-2012, 02:29 PM
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put front to stock height and then drop the rear - car will handle much better.
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Old 02-22-2012, 03:05 PM
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Originally Posted by GT3DE View Post
put front to stock height and then drop the rear - car will handle much better.
Clark,

The suggested rack of this car is 25mm with the rear being the highest.

This is interesting what you said. The nose dives tremendously under initial braking, then when your trailing into apex the weight is still relatively in the front thus, a potential understeering situation from mid apex to exit under acceleration.

Your suggestion makes a lot more since. Keep the front stock ride height and the rear lower, by the suggested rack of 25mm (1in).

Since I don't have the manual handy. Would you or anyone else know the stock ride height of this .1 gt3 car?

I think the manual suggests for track settings:
Front 108mm (4.25 in)
Rear 133mm (5.25 in)

What would stock be?

Thanks!
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Old 02-22-2012, 03:10 PM
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scroll up your browser
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Old 02-22-2012, 03:13 PM
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Originally Posted by bmardini View Post
Hi all

I've gone through the forums and see that OEM ride height on 997.1 gt3 is 108mmF 133mmR.

I've been struggling with a bit of oversteer on my car for a long time, to the extent that I even tried a wacky -2.4R -2.2F alignment and still I was able to get the back to step out on entry/apex/exit, but understeer on turn-in lol. So I checked my ride height and its 100mmF 130mmR. I am 5mm over the OEM 25mm difference front to rear.

Am wondering if this really makes a noticeable difference... its akin to dropping the nose by 5mm from any car. Is it too small or would it be something you'd pick up on?

what are your toe settings?
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Old 02-22-2012, 03:14 PM
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Originally Posted by speedyralph View Post
Clark,

The suggested rack of this car is 25mm with the rear being the highest.

This is interesting what you said. The nose dives tremendously under initial braking, then when your trailing into apex the weight is still relatively in the front thus, a potential understeering situation from mid apex to exit under acceleration.

Your suggestion makes a lot more since. Keep the front stock ride height and the rear lower, by the suggested rack of 25mm (1in).

Since I don't have the manual handy. Would you or anyone else know the stock ride height of this .1 gt3 car?

I think the manual suggests for track settings:
Front 108mm (4.25 in)
Rear 133mm (5.25 in)

What would stock be?

Thanks!
I think that is stock. The manual doesn't make any mention of dropping the ride height I think

I don't agree that playing around with the rake is such a good idea unless you really know what you are doing. My car was running 98mmF and 135mmR for about a year. The result? Pros: A car that turned in extremely keenly and had negligible understeer. Cons: Front end was bouncy on turn in, braking suffered as the springs seemed to be overwhelmed, and oversteer on exit was something you needed to be very careful for.

When I got it adjusted back to 108/133, I did a quick test on a bridge on the way home that I like to take at speed. Old spec I could hold the speed in the loooong right turn at about 109-110 km/hr and the car felt OK, a bit on edge and not really very planted. On the OEM rake I immediately cruised through at 114 km/hr with no drama whatsoever. 4kph is mega through a long corner like that.
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Old 02-22-2012, 03:44 PM
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Too much going on. However, I like my setup (996/997) at 20mm rake.

Wheel sizes, tire sizes, tire pressures, toe, oem LSD, sway bar settings, stock springs, stock shocks, oversteer on entry, sustained oversteer, oversteer on exit? too many variables.

5mm rake makes a lot of difference. I had an oversteer problem at Daytona, dropped the rear 9mm, and immediately started lapping 4 secs faster, yes 4 seconds. I don't have adjustable sway bars, so I have to adjust understeer/oversteer by playing with rake.

I would drop the rear of your car to 120mm, reset the toe (because the 996/997 toe-out when lowered), I like 0.25 degrees toe-in per corner at the rear. Then fine adjust with the front sway bar, set it to one from full stiff with the rear at full stiff if using stock 997.1 shocks/springs. Then re-test the car.
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Old 02-22-2012, 03:54 PM
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Originally Posted by NJ-GT View Post
I would drop the rear of your car to 120mm, reset the toe (because the 996/997 toe-out when lowered), I like 0.25 degrees toe-in per corner at the rear. Then fine adjust with the front sway bar, set it to one from full stiff with the rear at full stiff if using stock 997.1 shocks/springs. Then re-test the car.
Great info and yes, this car is 100% stock. Once I sell this puppy I'm gonna come knocking at Fritz's door, lol!

So keep the front at the suggested values of 108mm?
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