I just had Bilstein Damptronics installed, the car lowered about 20mm and a camber change in the alignment. The alignment was made a little less than a GT3. AWE did an excellent job and I want to compliment the honesty of Mike at AWE. I was concerned about too hard of a ride for a DD and actually scheduled to have sway bars put on at the same time but he recommended that I go with the suspension first and then decide on the bars. It is unusual to find people willing to forego a profit for what they feel is the best thing for their customer.
Getting back to my question, what is the official way to measure ride height in a TT and what are the factory numbers?

 

Well a good way to measure ride height to baseline and then compare a mod is to measure from the center of the hub to the highest point of the fender arch. I don't know if that is the "official" way or not, but that is they way I've done it in the past.

 

from member Al Norton:

The correct way to measure ride height is to go under the car with a pair of inside calipers or whatever you have that will correctly measure a distance from floor to the measuring point on the car while in your extended hand.

For the front, look for a green-headed bolt a few inches ahead of the front anti-roll bar attachment block. Measure from the flat surface to the ground. In the rear, look a little forward and inboard from the rear anti-roll bar attachment block. There is a flat spot on the crossmember with a little hole drilled in it. Measure from the flat surace around the hole to the ground.

if you lowered the car they probably did a corner balance before the alignment so I would stay with their ride height settings

 

Only problem with that approach is the consistency of the floor and tire pressure/condition impact accuracy.

 

https://www.6speedonline.com/forums/...ml#post2758690

 

That is exactly what the Suncoast mechanic did after he installed my Bilsteins.

 

^ That's the way I've always done it, may not be fancy enough for some, but has proved to be accurate on several cars in the past.

 

No it is most definitely NOT the official way and is at best an approximate. The first problem with this is you have no idea how high your car is compared to the Porsche OEM specification.
Even if you measure *before* lowering, you still don't know. Why? There is a +/- 10mm range for ride height as car comes from the factory (AFAIK any expert please correct me as needed). Your car may come from the factory 10 down (see this thread here).

And why is it important to know? Say you install Bilstein and want to lower 20, it's imperative to know where your are with respect to OEM spec. If you are already down 10, you would only lower an additional 10, etc.

A second minor point is the method you mention, to be completely accurate, requires that the ruler be perfectly perpendicular to ground and/or the end point on the fender to be perfectly defined. I wonder if everyone who does this method have a thread and weight attached to the ruler? Just kidding. Ok, half kidding.

Consistency of the floor? Tire pressure condition? Why would you not want to measure your car in its normal operating condition? Why would you NOT want to measure your car where it's reasonably flat? (Besides the issue that fender method would be affected as much by an uneven floor.) The official method as mentioned by GT3 Chuck and others here takes less than 5 minutes once you know where to measure. It's also quite consistent -- try it, you'll see what I mean.

 

Center of the hub to 12 O'Clock on the fender arch is the way we do it, and "industry standard" according to H&R and Eibach.

 

Hi Damon, thanks for sharing your professional knowledge.

1. Maybe because not all car manufacturers clearly define where to measure, down to the exact spot, like Porsche? The wheel arch method may be more useful because it is universally applicable, *NOT* because it is more accurate. Obviously it works (no argument from me), but is it the most accurate for a 911? IMHO, no.

2. Using the wheel arch method, you are talking about 35 cm range with a ruler hanging in mid air. Using the Porsche method, you are measuring 10 cm with ruler resting on the ground. I think the accuracy implication is obvious. Trying to locate the exact center of the wheel cap and making sure ruler is perpendicular are other issues. Center of wheel cap and fender are NOT on the same plane -- another problem.

3. Again, I would agree with you that the wheel arch method works, but remember us nutty guys here are questioning every 5 mm change. It's quite clear to me the Porsche defined method is much more accurate. Why would you not want to use it if it's specified by the engineers who design the car and actually easier to do? And a reference standard is provided?

 

So, the car is +/- 10mm. It will still be +/- 10 mm whether it's measured at the top of the fender or on the 'green' bolt head, unless of course the 'green' bolt head isn't attached to the rest of the chassis.

 

Can, you can't actually suggest that trying to squeeze under a low car to take a (probably) one handed measurement is EASIER than standing beside the car taking the measurement!

Plus, everyone has a reasonable tape measure but damn few have the tool required to measure under the car.

Still lovin' you all the same.

 

Yes, especially if you are already under the car looking at the drop link. Ha-ha-ha.

Alright, alright, so I exaggerated a *little* bit. :-) But... seriously, no special tool required, a ruler like everything else -- see post # 187 in my Bilstein thread. GT3 Chuck uses the caliper tool but a retractable ruler does the same.

I've tested every which way EVER mentioned -- no question which one is much more accurate. And yes it's true if you just go by fender height you could be down 30 and think that you are down 20.

 

First just a clarification for anyone new to this: the bolt is NOT green in 997 Turbo. GT3 Chuck may be talking about older car (see my Bilstein thread for more current info and pictures).
Ok... I don't know if you are just kidding here, but the problem is this: The only way to be accurate is to use the bolt measurement. Why? Because Porsche only provides reference standard for this bolt measurement. Not fender height.

You would like to be more accurate if you want to stay within spec of the Bilstein:
For example if you want to lower the car 15mm, +10 inaccuracy would still be ok. You are at 25.
However if you want to lower the car 30mm, +10 inaccuracy would take you to 40. This is now out of spec as max lowering is 30. At high speed, a small bump may take you to the bump stop, which could indeed have serious consequence.

Is this quest for accuracy "too much"? Maybe. But we've seen recent examples by well intentioned installers who might not have paid attention to details, and the results have shown, suspension mod is no laughing matter. It is imperative to follow specs and instruction to the T IMHO.