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Bullet-Proof_Biscuit said:
shalmaneser said:
I was surprised that the oe settings for the 996 front is zero camber. I guess the cayster setting is similar?
IIRC it's to reduce the 'widdow makery-ness' of the handling, and getting geometry set a bit more sporty is the first order on improving the drive of the 9x6 models, not sure on 9x7 though, assume similar.Boxsters have Macpherson struts. They LOSE negative camber during roll. I.E. the harder you push it, the worse it gets.
That is the fundamental limitations of a Macppherson strut over a double wishbone.
ETA - Note, that above is based on the wishbones being flat, or upward at ride height - which they are, particularly on car as low as that Red 986 pictured.
The short wishbones are great for packaging but not great for geometry.
This is also why the starting point fornegative camber on a 986 is always
"As much -ve camber as you can possibly get"
Because its always going to fade away as the car leans over.
That is the fundamental limitations of a Macppherson strut over a double wishbone.
ETA - Note, that above is based on the wishbones being flat, or upward at ride height - which they are, particularly on car as low as that Red 986 pictured.
The short wishbones are great for packaging but not great for geometry.
This is also why the starting point fornegative camber on a 986 is always
"As much -ve camber as you can possibly get"
Because its always going to fade away as the car leans over.
Edited by snotrag on Tuesday 30th June 14:19
Edited by snotrag on Tuesday 30th June 14:22
shalmaneser said:
Any links or suggestions for a more sporty geometry for a c2 3.4 on m030? When I had my e46 m3 someone had written up a good article with some decent suggested numbers.
this is based on my experience with 3.6 c2.On standard suspension i had:
- front: toe 0.01 each side, camber 0.25
- rear: toe 0.11, camber 1.35
This was good for normal driving but on a track day had terrible tyre wear on the outside front (not enough camber).
Currently on lowered KW v3 suspension:
- front: toe 0.01 each side, camber 1.35
- rear: toe 0.11, camber 1.50
I find this is not too much camber for the road though it does follow the shaper of the surface more than stock.
Front toe i find makes a very big difference to how "pointy" the car feels. CLoser to 0 = very pointy and more toe feels more "dull" to me (but also less twitchy on motorway, etc.).
Anyone gonna make a sneaky bid on this classic Porsche?
...only 125,000 made.
I think she's air cooled too !!!
6 figures easy...
https://collectingcars.com/for-sale/1959-porsche-d...
...only 125,000 made.
I think she's air cooled too !!!
6 figures easy...
https://collectingcars.com/for-sale/1959-porsche-d...
My 987 Cayman is setup similar to the above (-1.2 camber front, 0 toe, -1.5 camber rear, 3 minutes of toe) at standard ride height. On a smooth road it is great but on the cambered, cratered roads near me in rural oxfordshire it can sometimes be a bit twitchy. For me the pros outweigh the cons (especially on track) but if it were a daily driver I think I would probably want more toe in up front.
anonymous said:
[redacted]
It's kind of hard to explain but if you take a look at this video you can see the issue.https://www.youtube.com/watch?v=e2D0BHUm2BI
Yeah although I suspect that in reality that movement is not quite as extreme as it looks in the video. Somebody more knowledgeable than me will know...
It's really hard to get your head around how suspension geometry changes dynamically and when you lower it but if you draw the triangles and then begin "adjusting" parts of the triangle it makes it much easier to visualise.
In general the perceived wisdom appears to be than 20mm lowering on a 986/987 (and I guess the 99X equivalents) is around optimal. Lower than that and the control arm point upwards and the roll centre is below the ground. You can counteract this with stiffer springs etc but then it all gets really complicated and way beyond my comprehension
It's really hard to get your head around how suspension geometry changes dynamically and when you lower it but if you draw the triangles and then begin "adjusting" parts of the triangle it makes it much easier to visualise.
In general the perceived wisdom appears to be than 20mm lowering on a 986/987 (and I guess the 99X equivalents) is around optimal. Lower than that and the control arm point upwards and the roll centre is below the ground. You can counteract this with stiffer springs etc but then it all gets really complicated and way beyond my comprehension
Cmoose - that youtube animation was exactly what I was trying, and failing to find!
As stated, it all depends on the starting point and whether the control arms at ride height are downwards or upwards.
This is why they dont like being very very low.
Ref the 'pivot' at the top of the strut - yes, thats why you have a bearing aswell as a rubber bush. There is very little movment - but it needs to be there.
Again, another limitation of Macstrut - your damper piston and seals etc are taking lots of sideways, twisting loads etc. Creates stiction, binding etc. Thats why they are fairly large diameter.
On a double wishbone the damper assembly does nothing except move in and out.
It sounds like I'm slating the cars - I'm not, mine was good fun on track. But they are not a layout you would start with if you were building a ground up racer.
(Course the flip side is all the space in the front and rear boots through having slimline suspension and at the front especially, that low profile, simple front subframe.
As stated, it all depends on the starting point and whether the control arms at ride height are downwards or upwards.
This is why they dont like being very very low.
Ref the 'pivot' at the top of the strut - yes, thats why you have a bearing aswell as a rubber bush. There is very little movment - but it needs to be there.
Again, another limitation of Macstrut - your damper piston and seals etc are taking lots of sideways, twisting loads etc. Creates stiction, binding etc. Thats why they are fairly large diameter.
On a double wishbone the damper assembly does nothing except move in and out.
It sounds like I'm slating the cars - I'm not, mine was good fun on track. But they are not a layout you would start with if you were building a ground up racer.
(Course the flip side is all the space in the front and rear boots through having slimline suspension and at the front especially, that low profile, simple front subframe.
LennyM1984 said:
What is the history with Porsche using MacPherson struts on the front? I know the rears are usually multilink on the 911 but I think the fronts have always been struts. Is it just a packaging thing?
Possibly a hang over from the beetle? That used trailing arm front suspension which would have increased the luggage capacity at the front which would have been a priority in that application. Struts in later beetles too I think, which once again minimised intrusion into the frunk.It does seem very strange to me that Porsche keep with the struts at the front even nowadays but they clearly can make them work! But then again they do insist on having the engine hanging out over the rear axle so clearly they're not that keen on change....
It would be pretty hard to get the relatively deep and wide frunk on a 911/Box/Cayman otherwise. That would be full of subframe or chassis leg and upper wishbone.
Not impossible mind - Honda have done it on front engines hatchbacks, leaving room for an engine and transmisson. Very short upper wishbones though.
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