[ROVERNET - UK] P6 Design & Rear Suspension Function
rovercar at comcast.net
Mon Apr 7 21:10:03 BST 2008
Vern Klukas wrote:
> Body roll has very little to do with road holding (and, btw, has
> nothing to do with a car overturning, that is dependant on lateral
> roadholding, the track width and the car's centre of gravity), and I
> would suggest that it was the driver lifting in the P6 that allowed
> you to pull ahead. When the boys and I would take customers cars out
> for "road tests," I never had trouble keeping up to a SD1 in a V8 P6.
> In a 4cyl P6, the SD1 would walk away on the straights but I could
> stay with him on the twisty bits.
I'm not arguing the mechanics of the thing with you, Vern, because I
think you know a lot more about that than I do, but when a car is
leaning heavily and the tires are losing grip, you've reached the limits
of the the car's roadholding ability. I've owned a couple of French
cars, so I know what you mean about body roll vs roadholding.
Also, the twisty bits are not the same as the freeway on/off ramp I
specified. The ramp is more like a skid pad than a road course.
>> So, I'm not knocking the P6 suspension, but I'm not sure that all of
>> the complexity bought you all that much for all of the expense and
>> service hassles. The SD1 had a well-located live axle that wasn't all
>> that different from what was installed under Volvo sedans up into the
> Beg to differ there, the SD1 was much more sophisticated than Volvo's
Well, then, you're making my argument for me. I don't know how
sophisticated it was, but it was a whole lot simpler than the P6 rear
suspension. The SD1 rear suspension only has about ten moving parts to
it, if you include all of the bushings. It couldn't have been expensive
to manufacture (or it wouldn't have been on the SD1 in the first place),
and it is simple to service.
>> The complexity made it more difficult and expensive to service due
>> to the time it took to do things like setting the valve clearances
>> (on the 4-cyl)
> But how often do you set the valve clearances on a 2000?
Isn't once enough? Would your design choice be an engine that
necessitates the removal of the cylinder head (often more than once
according to posters on this list) in order to adjust the valve
clearances? And, of course, Rover manufactured a special jig for that,
too. Who wants an engine where a wrench, a screwdriver, and a set of
feeler gauges is all you need to do the job? No fun in that. Then
there's the cost of the cylinder head gasket.
The 4-cyl valve clearance snafu speaks volumes to what sort of
priorities Rover had.
>> or servicing the rear brakes, to say nothing of having to source
>> front shocks that are valved in reverse to every other car on the road.
> Total red herring there Glen. The same can be said for any part of any
> car, that is unique to that particular model.
Red herring fallacy <http://en.wikipedia.org/wiki/Red_herring_fallacy>,
a logical fallacy in which one purports to prove one's point by means of
Not at all. Shocks are a routine service item that can be sourced from a
variety of vendors located around the corner. Since most shocks, at the
time, fit several different vehicle, they were more likely to be stocked
and would be priced lower. Maybe these things were readily available in
the UK, but not in the USA.
The argument was that the design made the cars inherently difficult and
expensive to service compared to other cars. This was true in the home
market, but it was doubly true in the American market where they hoped
to sell a lot of cars. If you went to someone other than a Rover
specialist (ka-ching!), the shocks wouldn't be readily available, and
the local master mechanic wouldn't have the tool to adjust the pistons
out of the rear brake calipers. To adjust the valve clearance, the
mechanic would have to order a head gasket set from Rover and then be
willing to take on the liability for removing and reinstalling a
cylinder head. Of course, that wouldn't be so bad because he'd be
charging you $300 to adjust your valve clearances, anyway, due to the
inherent issues designed into the engine by Rover engineers and approved
by Rover management.
Volvo service would have laughed out loud at such silliness. And Volvo
sales may well have pointed out that the P6 you were considering would
be off the road for two days and cost you hundreds of dollars for what
were simple and inexpensive operations on other cars such as the Volvo.
Vern, I love the P6, too. But it's pretty hard to argue that Rover
thought through the service issues or the associated costs or the
inconvenience to the owner. If they thought these things would fly in
the mass American market, then they must have been truly naive or just
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