Ride height - factory measurement method

[cowtown]

Hi,
I'm playing with the ride height on my '75.

Can anyone tell me:

For the BA height recommendation (25" Rear, 25.5" Front, fender lip to ground), what would be the equivalent "factory" measurement - the one that uses the difference between the torsion bar cap center and wheel center heights? This is assuming stock tire and wheel sizes.

I think factory as-shipped-to-USA spec was 12mm in the rear, so I'm guessing the rear BA "spec" would be around 0mm?

My tires are undersized (205/45-16), making fender measurements kind of invalid. I'm subtracting an appropriate amount (0.9") to compensate, but want a reality check against the factory spec.

Thanks for any advice!

[Bill Verburg]

Factory method ride height for the front of '76 my C3(ROW) was 108 &#177 5mm
for a US 911 it was 93 &#177 5mm.

The measurementis defined as the distance between the wheel center and the torsion bar center.

The 108m spec gives a height of ~25" at the lip.


The factory rear spec fo ROW 911 was 12 &#177 5mm
for US it was 37 &#177 5mm

[gduke]

I measured mine a while ago and used the torsion bar cap, wheel center method. The proceedure is in the 101 book.

[cowtown]

Ah, thank you Bill. I was thinking that the 12mm rear spec was USA spec. If it's Euro spec, I'll just shoot for that, or maybe a tiny bit lower.

Colin

[HKZ Bob]

Originally Posted by Bill Verburg

Factory method ride height for the front of '76 my C3(ROW) was 108 ± 5mm
for a US 911 it was 93 ± 5mm.

The measurementis defined as the distance between the wheel center and the torsion bar center.

The 108m spec gives a height of ~25" at the lip.


The factory rear spec fo ROW 911 was 12 ± 5mm
for US it was 37 ± 5mm

Hello the 108 mm is defined with an empty or full gas tank. Do you have to add. extra load to the tank?

BR
Bob

[Bill Verburg]

Originally Posted by HKZ Bob

Hello the 108 mm is defined with an empty or full gas tank. Do you have to add. extra load to the tank?

BR
Bob

I don't know where you got that from but it's wrong
DIN 70020 defines the measurement conditions which include a full tank of gas, tools and spare.

[HKZ Bob]

Originally Posted by Bill Verburg

I don't know where you got that from but it's wrong
DIN 70020 defines the measurement conditions which include a full tank of gas, tools and spare.

Bill,

thank you. I was not sure since the height leveling is perfromend with

a load & does not mention anything of the gas tank fuel level.

Load the front axle with a ballast of 100 kp
(220 lbs) in such way that both wheels are
evenly weighted (distribute the load evenly in
the luggage compartment).
2.

So for the height measurement add 100kg with a full or empty gas tank.

And for the alignment include a full tank of gas, tools and spare no extra weight.

Thank you. How about 75kg driver weight.

The DIN says 90% filled gas tank and 75kg driver weight.

Alignment now with driver weight or without?

DIN 70020

Zur Ermittlung des Leergewichts eines Fahrzeugs existieren verschiedene Normen. Das Leergewicht eines Straßenfahrzeuges (z. B. eines PKWs) setzt sich nach der DIN-Norm DIN 70020 Teil 2 aus der Masse des Fahrzeuges bei zu mindestens 90 % gefülltem Tank und je nach Fahrzeugart noch dem mit 75 kg angesetzten Fahrzeugführergewicht zusammen; die Normausgabe vom Juni 1972 galt für Kraftfahrzeuge und deren Anhängefahrzeuge mit Ausnahme von Krafträdern und gewissen Sonderfahrzeugen. (

[Arne2]

Originally Posted by Bill Verburg

The 108m spec gives a height of ~25" at the lip.

Bill, I hate to ask, but are you sure about this? I've heard this over and over, but my experience with my car is quite different.

My '84 has stock size tires (205/55-16, 225/50-16, both 25" diameter), and right now with about half a tank of fuel I measure between 25 5/8" and 25 3/4" at the fender lip. Yet when I do the math to measure the factory way (difference between wheel center and center of torsion bar), I'm much lower than 113mm (108 + 5mm). I measure mine currently at ~140mm.

Bentley notes that older, higher mileage cars could sit even lower, as much as another 15mm. So in theory, adding all that up means that an older car (which they all are by now) could be as low as 128mm. Which still puts me 1/2" lower than specs would allow. Yet I still measure close to 25 1/2" at the fender. How is this possible?

FWIW, my rear measurements are similar. Fender height right at 25", but the actual numbers are well below what are called for.

[Bill Verburg]

Get away from your keyboards and pick up a copy of the shop manuals or tech specs, do you own reading.

[Arne2]

Originally Posted by Bill Verburg

Get away from your keyboards and pick up a copy of the shop manuals or tech specs, do you own reading.

Thanks, I've done that. Went out to the garage and measured fresh while posting the previous. The only thing I'm questioning is the discrepancy between the oft-quoted 25.5/25" fender measurement, the 108/12mm measurements, and the physical measurements of my particular car. Because the three don't jive on my car.

[Bill Verburg]

Originally Posted by Arne2

Thanks, I've done that. Went out to the garage and measured fresh while posting the previous. The only thing I'm questioning is the discrepancy between the oft-quoted 25.5/25" fender measurement, the 108/12mm measurements, and the physical measurements of my particular car. Because the three don't jive on my car.

different tire sidewalls/heights, maybe the 25.5 is wrong, I dunno because I never use fender heights except in the most casual way
108+/- 5mm is the spec for unregulated front height, that means 113mm at the lowest end and 103mm at the most raised end

for track cars like SCRS and RSR, 143+/-5mm, so 148mm slammed and 138 jacked

[Arne2]

I guess that's kinda my point, Bill. I understand and agree with the reason behind the factory method, and not using the fender lips. But most people just spout the 25.5/25" numbers for "Euro height" as if they were gospel, and I don't think they are correct in most cases. My car is an example. With stock 25" diameter tires, 25.5/25" is well below RoW height as measured the factory way - by about 25-30mm if I'm really doing this correctly.

I'd really like to see some other numbers (factory method) from other cars that have stock height tires to confirm what I'm thinking - that 25.5/25" fenders (assuming stock tire sizes) is REALLY LOWER than euro height.

[Lyle O]

I hate to resurrect this thread, but I just found it after researching here, as this issue has been bugging me for months also. Like Arne2, I am getting measurements of 137mm on the fronts, same tire size: 205/55-16, but fender heights are 25 5/8". Everything is stock on the car (that I know of), and there is a nice gap between the top of the tire and the fender lip, so I would like to lower the car a bit. But at 137mm, this indicates a lowered car! What am I missing here, folks? My car is an '87 Carerra Cab. Did any of the basic suspension components change in '86 or '87? I only have the Bentley manual and Wayne's book, but not the Porsche service manuals, so maybe something else is referenced there? Arne2, did you ever resolve this in your case? Thanks a lot for any further inputs on this.

[Arne2]

Lyle, my first conclusion is that with a very few exceptions, there are two types of 911 owners. Those who judge ride height by fender measurements and appearance (paying no attention to the real measurements), and those who measure and adjust based on factory specs and methods (and who don't pay attention to fender measurements). You and I are in the very small group who look at both.

There are several other conclusions.

• Most people have no clue just how freaking tall a 911 set to factory height really is.
• There were only two sets of specs for road-going 911 models. The first was for all cars except '74-83 US-spec, and then of course, the spec for the '74-83 US cars which was higher due to the bumper height requirements in place for those years. When the bumper laws changed for '84 and on, Porsche reverted all cars to the spec used RoW for '74-83.
• The corollary to the prior is that "euro height" is an artificial construct. There was only the "US impact bumper height" and normal 911 height.
• There is a general perception that the oft-quoted ("euro") fender measurements of 25.5" F and 25" R is the "normal" non-bumper 911 height. I've found this to be totally false. Cars with those fender measurements (and with stock diameter tires) are already well below the factory correct RoW or non-bumper specs, as you have found as well.
• As a guess (since I've not raised my car to verify), if I were to raise my car to the factory spec of 108/12 (F/R), my fender measurements would be close to 26.75" F and 26+" R.
• I also suspect (based on the local cars I see at PCA events) that very few cars these days are set at factory height.

FWIW, my car is still running at about 140mm front, and -5mm or so in back.

[Lyle O]

Thanks a lot, Arne; glad to know we're not alone in our minority opinion (and I am not crazy or totally stupid). You have nailed the issue; this "Euro height" thing seems to be one of the biggest myths in our little universe. It would interesting to see how everyone's measurements at the fenders vs. factory method really do correlate. Also FWIW, I may still tweak my car just a tad lower, but i do feel a little less inclined to do so. Again, thanks for the insight.

[Arne2]

Originally Posted by Lyle O

It would interesting to see how everyone's measurements at the fenders vs. factory method really do correlate.

I've asked that question in other threads, the response has always been (insert sounds of crickets chirping here). You are the first person other than myself who has provided both types of measurements, and they are consistent with mine. I'm going to consider that fairly conclusive.

[stlrj]

Originally Posted by Arne2

[*]As a guess (since I've not raised my car to verify), if I were to raise my car to the factory spec of 108/12 (F/R), my fender measurements would be close to 26.75" F and 26+" R. .

Good guess. I recently raised my 87 to the 108mm factory spec and it did come up to exactly 26 3/4" at the fender lip. Steering effort has significantly been reduced and handling is just as crisp as ever.

Oh, the rear height per factory 16mm spec came out to 25 1/2" fender lip height on my car.


Cheers,

Joe

87 Carrera

[Algernon]

Originally Posted by stlrj

Good guess. I recently raised my 87 to the 108mm factory spec and it did come up to exactly 26 3/4" at the fender lip. Steering effort has significantly been reduced and handling is just as crisp as ever.
Cheers,
Joe
87 Carrera

Agreed! I recently did the same, 26-3/4 and 26. But it does look kind of high. Ride is good, so I'm leaving it there for now!

[stlrj]

Originally Posted by Algernon

Agreed! I recently did the same, 26-3/4 and 26. But it does look kind of high. Ride is good, so I'm leaving it there for now!

Same here. Also, I no longer worry about my front bottoming out on driveways.

But I know it's just a matter of time that someone will suggest I lower it to euro height...

[GMR911]

I had a reputable shop in Albany NY set my ride heights, align and corner balance my car a few years ago. I wasn't really looking for the fender height measurements as way of measuring the ride height as much as the factory specs. I was looking for 113mm fronts, and 12mm rears- I believe these were listed in my spec book as European Carrera ride heights. When all said and done I believe and this is from memory I think fronts came in at 112 and 114 and the rears were like 10 and 13. The corner balances were within 25 lbs side to side, I don't remember the diagonal weights. Point made is that the fender heights were probably 26.5 to 27 in the fronts and 26+ in the rears but the car handles like it never did before. Probably one the most noticeable improvements I made. Based on my car, I think if one sets the ride heights to those mm specs one can expect those fender height measurements, Jerry