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can't understand this
https://forums.tipec.net/viewtopic.php?f=25&t=20359		 Page 1 of 1
Author:  Adrian [ Sat Sep 05, 2015 10:46 am ]
Post subject:  can't understand this
on a 944, why did they go to all the bother of venting the door space, i.e. via the grille in the b post.
Both cill cavities are also vented into the inner rear wheel arch and out thro the slots at the side of the tailgate.


Also, on the rear suspension i assume this rubbery part

Attachment:
sept15 016 (Small).jpg
sept15 016 (Small).jpg [ 35.89 KiB | Viewed 4086 times ]


is to limit sideways torsion bar movement?

But, is there no rubber bump stop on the A arm? And, what is that welded-on metal bit that juts down just to the rear of that rubber part. I'm a little confused.
Author:  Endoman [ Sat Sep 05, 2015 1:26 pm ]
Post subject:  Re: can't understand this
The vents in the doors are probably to help dry out the door interior as well as venting the air when shutting the door. The rear banana bar is to resist rotation of the torsion bar tube as the swing plates work in rubber bushes which are designed to flex, not rotate.. If polly bronze, delrin or roller bearings are used and the torsion bar deleted with coil over shocks, the banana bar is often chopped off. The rubber mounting is for nvh isolation and often replaced with a solid mount for racing.
The 944 and 968 were often criticized for a harsh ride (especially the Sport and CS models) a function of the somewhat dated torsion bar / trailing arm rear suspension with high unsprung weight. Hence the amount of rubber in the rear end.
Progressive bump stops are fitted to the shocks front and rear, the 944 does not respond well to slamming despite the trend over the pond.
I'm in the middle to a full suspension refurb on my S2 as most of the rubber bushes are well past it.
The 924/944/968 are beautifully handling cars due to front to rear weight balance c/w early 911s which can be quite a handful especially in the wet.
With the 964 and 993 the torsion bar was ditched and the difference is very noticeable.
Author:  Waylander [ Sat Sep 05, 2015 4:23 pm ]
Post subject:  Re: can't understand this
That mount in the centre of the picture has delaminated, fallen to bits, that will cause the ass to sag a bit.

The bad news is they are £172.00 each
Author:  Adrian [ Sat Sep 05, 2015 7:33 pm ]
Post subject:  Re: can't understand this
i'm probably being thick, but i can't see why that rubber part would cause the rear to sag....does that rubber part not bear against the banana bar to limit transverse movement, something that the mounting onto the rear of the cill also does
Author:  Waylander [ Sat Sep 05, 2015 9:23 pm ]
Post subject:  Re: can't understand this
Hard to put into words but that is the end plate of the tube and it only has two mounting points.

The bottom as you point out and that top mounting, the banana arm bump stop at the top gets crushed when the top mount breaks up and allows the whole tube to twist only by a few MM but when you add the length of the trailing arm to the equation it adds up to about 10-15 mm

I can see in your pic that it has not rotated very far yet but it will eventually, when they get really bad the end of the alloy end plate at top will start hitting the chassis rail
Author:  Adrian [ Tue Sep 08, 2015 5:14 pm ]
Post subject:  Re: can't understand this
sorry i didn't see the bolts holding the rubber/metal bush to the body......so the top bush (mounted next to the upper damper mount takes the torque reaction from the inner end of the torsion bar (via the torsion tube) and the one further forward (in my pic) takes the torque reaction from the outer end of the torsion bar, in conjunction with the mounting on the cill end, but only because the rubber bushes on the spring plate are tending to shear, not rotate in their housings...is that it?
Author:  Waylander [ Tue Sep 08, 2015 6:11 pm ]
Post subject:  Re: can't understand this
the bushes on the spring plate will not shear but they will be massively out of round with the load on them from the car

shown here
http://www.elephantracing.com/project/9 ... atediy.htm
Author:  Adrian [ Thu Sep 10, 2015 6:21 pm ]
Post subject:  Re: can't understand this
what i meant was, if the rubber bushes on the spring plate were roller bearings, there'd be no torque reaction....
i have a bit of a knocking noise from rear left when going over bumps etc....i'm expecting to have to replace the 4 bushes, 2 each side (1 in my pic plus the the other one at 12 o clock posn ), no point in doing any less.....i don't want to go polybush, so , as they're vulcanised to the spring plate, don't really want to replace the spring plate to torsion bar bushes....sound right?
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