Light rear End
06-05-2005, 09:31 PM
#1
Rennlist Member
Thread Starter
Light rear End
Was cruising through some high speed twisties up here in the Rockies and noticed the cars tendency to get light at the rear. I'm thinking the front is diving too much (body roll?) when the corner is taken allowing the rear end to rise up and become light.
Car has Michelin Pilot sports in almost new condition on all 4 corners at stock size............shocks and springs are believed to be original.
Cruising speed was +160kph in the turns; +200kph on the straights.
Perhaps the racing community would have input............thx.............Malcolm
Car has Michelin Pilot sports in almost new condition on all 4 corners at stock size............shocks and springs are believed to be original.
Cruising speed was +160kph in the turns; +200kph on the straights.
Perhaps the racing community would have input............thx.............Malcolm
06-05-2005, 10:23 PM
#5
Rennlist Member
Thread Starter
Originally Posted by mpesik
??-Hi Malcolm. How sharp are these turns and at WHAT speed!
Need more track time @ Race City to learn trail braking with the car better and when to get back on the throttle so as to minimise the suspension transitions.
06-06-2005, 04:52 AM
#6
Rennlist Member
Malcom, I'm not sure what your basis for comparison is, but the 928 has a very different feel to the rear end than a car with a live axle(older mustang, camaro) and is even more different than a conventional trailing arm or semi-trailing arm design. Under braking, turn-in is enhanced by the Weissach axle's tendency to exhibit toe-in under braking, where live axles do not change under braking and trailing arms tend to exhibit toe-out under braking.
Now, if you're saying that you've driven it this way a lot but that it's lighter than usual under the conditions you describe, then something may have changed. If what you're saying is that you haven't been driving it like this till recently and this is how it feels to you, then maybe you just need to get used to it and what it can do for you.
Now, if you're saying that you've driven it this way a lot but that it's lighter than usual under the conditions you describe, then something may have changed. If what you're saying is that you haven't been driving it like this till recently and this is how it feels to you, then maybe you just need to get used to it and what it can do for you.
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06-06-2005, 07:26 AM
#8
Rennlist Member
My thoughts perhaps echo Daves comments: it has been quite a while since I drove those great open sweepers up through Banff and Radium Mtn area, but it was my 'training ground' with some experienced hot shoes from the Wild Rose PCA chapter during club runs - back when I began my affair with the '80 
.
As the car loaded approaching a high speed apex, there was a moment of sphincter tightening lightness as the rear axle did its thing. I say "rear axle", believing it was the car - and not poor driver technique.
Past that point, the car was very neutral - and idiot proof if you paid attention to the low moaning sounds from the tires. Possibly it may be an issue to adapt to, as Dave said.
The roads are much tighter and twistier here - or I'd be tempted to do a test.
. As the car loaded approaching a high speed apex, there was a moment of sphincter tightening lightness as the rear axle did its thing. I say "rear axle", believing it was the car - and not poor driver technique.
Past that point, the car was very neutral - and idiot proof if you paid attention to the low moaning sounds from the tires. Possibly it may be an issue to adapt to, as Dave said.The roads are much tighter and twistier here - or I'd be tempted to do a test.
06-06-2005, 11:36 AM
#9
Rennlist Member
Thread Starter
Originally Posted by SharkSkin
Malcom, I'm not sure what your basis for comparison is, but the 928 has a very different feel to the rear end than a car with a live axle(older mustang, camaro) and is even more different than a conventional trailing arm or semi-trailing arm design. Under braking, turn-in is enhanced by the Weissach axle's tendency to exhibit toe-in under braking, where live axles do not change under braking and trailing arms tend to exhibit toe-out under braking.
Now, if you're saying that you've driven it this way a lot but that it's lighter than usual under the conditions you describe, then something may have changed. If what you're saying is that you haven't been driving it like this till recently and this is how it feels to you, then maybe you just need to get used to it and what it can do for you.
Now, if you're saying that you've driven it this way a lot but that it's lighter than usual under the conditions you describe, then something may have changed. If what you're saying is that you haven't been driving it like this till recently and this is how it feels to you, then maybe you just need to get used to it and what it can do for you.
I do tend to drive the car very spirited in this deserted part of North America but in saying that the car is probably faster than ever before in the 4 years I've owned it with recent engine maintenance/ performance enhancements (GT eproms, rebuilt MAF, Nology ign wires etc).
It's probably as Bill said, 'original suspension' hmmmmmmmmm!!! Time to get the chassis tuned now that the engine is performing very well.
I'm thinking of Eibach/ Bilsteins springs and shocks with greasable sway bar bushings. Thx for the input.
06-06-2005, 11:52 AM
#10
Rennlist Member
Thread Starter
[QUOTE=Garth S]
As the car loaded approaching a high speed apex, there was a moment of sphincter tightening lightness as the rear axle did its thing. I say "rear axle", believing it was the car - and not poor driver technique.
LOL Garth.............I must admit that there is a moment of 'muscle' tightening @ these speeds and perhaps a degree of driver technique that could be improved. I have little/no tyre howl leading me to believe the suspension is unloading and causing the described symptoms.
New shocks and springs with greasable sway bar bushings, set the ride height, have the car aligned again and go for another ride.
If your roads are too tight for such spirited driving we're planning a small Canadian SITM later this summer............your more than welcome to join us.
As the car loaded approaching a high speed apex, there was a moment of sphincter tightening lightness as the rear axle did its thing. I say "rear axle", believing it was the car - and not poor driver technique.
LOL Garth.............I must admit that there is a moment of 'muscle' tightening @ these speeds and perhaps a degree of driver technique that could be improved. I have little/no tyre howl leading me to believe the suspension is unloading and causing the described symptoms.
New shocks and springs with greasable sway bar bushings, set the ride height, have the car aligned again and go for another ride.
If your roads are too tight for such spirited driving we're planning a small Canadian SITM later this summer............your more than welcome to join us.
06-06-2005, 12:04 PM
#11
928 Collector
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Rennlist Member
Malcolm, I think (not necessarily correct) that you are learning about lift-throttle oversteer. One hundred-and-sixty kilometres an hour through twists is bloody fast. If you lift your foot there, you are a braver man than I.
06-06-2005, 02:46 PM
#12
There is a certain point in a curve where there is a transition, and this would be a good time to lightly apply throttle, which tightens things up. Have your suspension checked and or call one of the big three. I expect that new shocks are the ticket, and not that hard to do or get done.
06-06-2005, 09:03 PM
#13
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Thread Starter
Originally Posted by heinrich
Malcolm, I think (not necessarily correct) that you are learning about lift-throttle oversteer. One hundred-and-sixty kilometres an hour through twists is bloody fast. If you lift your foot there, you are a braver man than I.
Thanks for all the comments, springs/shox and bushings on order ASAP
