I don’t know about all these low pressures. My BMW factory recommendation is 35 Front, 37 Rear
My Mercedes asks, no - demands since it’s German, 32/36 F/R unless I plan on driving at sustained speeds of over 100 MPH in which case I should use 36/40.
Different chassis, different assumptions about usage.
Thanks for all the comments. It was the apparent sensitivity to tyre pressures, and lack of other knobs to twist to adjust the handling - especially at the rear - that set us down the path to do it our way. The easy part was finding a good theoretical layout, relying heavily on RACE software and the ever-helpful Raoul. This is what it looked like, with no account taken of trivial detail like clearances and attachment points.
At this point we passed it to the professionals to do the hard work and define real parts, but of course I couldn’t resist taking a step outside the narrow zone of my knowledge. It didn’t start well
Conclusions:
- Big respect for CAD jockeys.
- Fusion 360 has great capabilities in part and system design
- I do not
Could only go upward from here.
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Yes I have a Mk7 and always wonder about those low pressures on such a heavy car. Modern radials on my Merc are much higher.
“Would Sir care to indicate the purpose and manner of his proposed voyage in order that the staff might apply the appropriate quantity of atmosphere to the carriage wheels?”
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This is the kind of effusive pedantry up with which I will not put!
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Given this was 45 years ago, all I will swear to is:
-they were black.
-they were round.
Quiet in the colonies please
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I had them on my car.
The curse of a near photographic memory: Semperits came in at least two flavors; M301s were fabric belted radials, M401s were steel belted.
I do recall they were 'spensive: $400, in 1976 dollars.
Tires are MUCH cheaper now!
For that kind of money they would have to do a lot more than go round and round
You guys are funny
The colonies will not be quiet
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Clive, I apologize if I missed it: Are you taking a similar approach to the front? Sure looks like fun. Tom
Yes Tom, the rear will be double A-arm similar to the front. The software we use to lay out the kinematics doesn’t distinguish between front and rear so the picture shows a steering rack which obviously won’t be there, just a pair of toe links.
The whole exercise really started at the rear because we wanted to make it independent in all situations and benefit from decades of progress in analysis and understanding of suspension behaviour - for example, using toe and camber change as positive factors. It’s a pretty conventional double A-arm system although we invested a lot of time in the detail of mount locations and stiffness. (In addition to geometry, the software allows very detailed study of bushing and joint stiffness in all directions).
The front layout started out quite conventional although we changed to coil springs, combined with a stiffer front structure. We later moved the spring / damper units above the picture frame, driven by the upper control arms as rockers, to gain the necessary space to improve lower control arm stiffness.
Thanks for the interest. More detail as it becomes available.
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Maybe some interest - RACE software has a good library of suspension parameters and definitions. I use it when I need to sound learned.
https://race.software/education/suspension-designer-library/
I almost had an interesting experience yesterday when I went to do some more damper testing at BDR in Bangkok. I’m the harmless weirdo who shuffles in from time to time, they leave me to take care of stuff myself. They’d moved stuff around since my last visit, when it was time to gas the damper I couldn’t find the nitrogen bottle in its usual place. I found a set of bottles but the end fitting was different. As I was looking for a screwdriver I thought maybe I should check the label: อะเซทิลีน.
Very laboriously, drawing fragile memories from the depths…
อะ = a
เซ = seh
ทิ = tee
ลีน = leen
OK, I probably don’t want to put 200psi of that in a tube and stroke it at 20 in/second then.
Long pause while I look up the Thai word for nitrogen
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Painfully aware of that Jim. My daughter is a Colonial citizen and BC resident
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On July 3rd you posted a partial image of the head, when do we get to see the results…can’t wait…
