[ROVERNET - UK] P6 Design & Rear Suspension Function

Vern Klukas vern at inkspotco.com
Mon Apr 7 21:55:51 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.

When the tires lose grip, you are at the limit. The body roll is 
beside the point except that many drivers tend to back off as the 
roll increases, thereby never exploring the actual limits of the car.

>  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 90's.
>>Beg to differ there, the SD1 was much more sophisticated than 
>>Volvo's approach
>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.

I should of said: I have never had to adjust the valves on a 2000, 
except when the head was going to have to come off anyway. If the 
clearances had gone away, something was amiss. It is not a routine 
service operation.

>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 
>>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 
>irrelevant arguments
>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.

When I was fixing these as a job in the late 70's early 80's, shocks 
were readily available. Aside from OEM, American brands included 
Monroe, Gabriel and Autocraft. And then there were Koni, Bilstein, 
Spax. The Monroes and Gabriels were always in stock and we usually 
used the Monroes which were about 2/3 the cost of OEM.

And most shocks "back then" did not fit several different cars, they 
might be common across a particular model of car but in most cases a 
specific part number would apply to only one car.

>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 bloody headed.

But most of your points talk more to problems created by the rarity 
of the car in America, not on it's construction. The master mechanic 
wouldn't have the caliper tool if he saw one P6 a year, but he'd buy 
one pretty quick if he had twenty customers to service.


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Vern Klukas                             I'm a little . . .
Inkspot Type & Design
vern at inkspotco.com

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