I know, I know. Dumb question re: Ride height
Nordschleife Master
Joined: Dec 2004
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From: Guelph, Ontario, Canada
Because fender placement is not relative to the mounting points of the suspension. While they will be close, the most accurate suspension geometry is kept by measuring how far the suspension is off the road, not the body panels. There can easily be 5-10mm difference.
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From: Boulder Creek, CA
It could for YOUR car once you know what the REAL measurements are, but outside of the nearby solid known suspension components, you introduce more and more slop the father out you get in measuring this...so it cant compare between two cars.
Chronic Tool Dropper
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It can, but many fenders aren't what/where they used to be. When I first got the car, I adjusted the height to WSM spec height, and shared the fender lip heights with the group on what was the predecessor to RL. I should have known better, since folks would find that post with search and believe it was a standard way of measuring.
The suspension pick points are more reliable, but the WSM also assumes that the factory tire sizes will always be used, and that the tires are new. There's that 10mm allowance for tire wear, for instance, but folks are loathe to consider it as such. WSM heights and tolerances are there to guide a dealer tech, but give enough latitude so they aren't obligated to "do something" (read: warranty service) about a car that's a little higher or lower than another.
Ultimately, the "perfect" static height has the lower control arm level, with the tie rod at the same angle. This gives the least amount of camber and toe change with normal displacement/movement of the suspension. With new standard-height tires, the WSM settings give you this. Sag/wear allowance should probably not be used unless the tires are worn, keeping in mind that most Z-rated tires don't have 10mm of tread depth to give away.
I made a set of height gauges out of coat hanger wire (actually welding rod) that serves nicely. Stores easily in a 1qt Ziploc bag too, with a piece of corrugated tool holder and some masking tape to complete the kit.
The suspension pick points are more reliable, but the WSM also assumes that the factory tire sizes will always be used, and that the tires are new. There's that 10mm allowance for tire wear, for instance, but folks are loathe to consider it as such. WSM heights and tolerances are there to guide a dealer tech, but give enough latitude so they aren't obligated to "do something" (read: warranty service) about a car that's a little higher or lower than another.
Ultimately, the "perfect" static height has the lower control arm level, with the tie rod at the same angle. This gives the least amount of camber and toe change with normal displacement/movement of the suspension. With new standard-height tires, the WSM settings give you this. Sag/wear allowance should probably not be used unless the tires are worn, keeping in mind that most Z-rated tires don't have 10mm of tread depth to give away.
I made a set of height gauges out of coat hanger wire (actually welding rod) that serves nicely. Stores easily in a 1qt Ziploc bag too, with a piece of corrugated tool holder and some masking tape to complete the kit.
Nordschleife Master
Joined: Jul 2003
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From: Minneapolis
An interesting observation is that the factory heights don't give horizontal lower arms. I've always thought that was a good design goal for the reason you gave: least alignment variation in cornering and bumps.
The later WSM gives a procedure that removes tire size from setting the ride height and looks, correctly, at the difference between body height and knuckle height. In other words, don't set the fender height at all; set the angles of the suspension.
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It can, but many fenders aren't what/where they used to be. When I first got the car, I adjusted the height to WSM spec height, and shared the fender lip heights with the group on what was the predecessor to RL. I should have known better, since folks would find that post with search and believe it was a standard way of measuring.
The suspension pick points are more reliable, but the WSM also assumes that the factory tire sizes will always be used, and that the tires are new. There's that 10mm allowance for tire wear, for instance, but folks are loathe to consider it as such. WSM heights and tolerances are there to guide a dealer tech, but give enough latitude so they aren't obligated to "do something" (read: warranty service) about a car that's a little higher or lower than another.
Ultimately, the "perfect" static height has the lower control arm level, with the tie rod at the same angle. This gives the least amount of camber and toe change with normal displacement/movement of the suspension. With new standard-height tires, the WSM settings give you this. Sag/wear allowance should probably not be used unless the tires are worn, keeping in mind that most Z-rated tires don't have 10mm of tread depth to give away.
I made a set of height gauges out of coat hanger wire (actually welding rod) that serves nicely. Stores easily in a 1qt Ziploc bag too, with a piece of corrugated tool holder and some masking tape to complete the kit.
The suspension pick points are more reliable, but the WSM also assumes that the factory tire sizes will always be used, and that the tires are new. There's that 10mm allowance for tire wear, for instance, but folks are loathe to consider it as such. WSM heights and tolerances are there to guide a dealer tech, but give enough latitude so they aren't obligated to "do something" (read: warranty service) about a car that's a little higher or lower than another.
Ultimately, the "perfect" static height has the lower control arm level, with the tie rod at the same angle. This gives the least amount of camber and toe change with normal displacement/movement of the suspension. With new standard-height tires, the WSM settings give you this. Sag/wear allowance should probably not be used unless the tires are worn, keeping in mind that most Z-rated tires don't have 10mm of tread depth to give away.
I made a set of height gauges out of coat hanger wire (actually welding rod) that serves nicely. Stores easily in a 1qt Ziploc bag too, with a piece of corrugated tool holder and some masking tape to complete the kit.
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Racer
Joined: May 2011
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From: West Chester Ohio
Sooo, with a known fender lip height=knuckle height on a particular car it should be close? I did have one piece of coat hanger wire that I cut to 175mm. But when I tried to fit it was a little too long. I will cut a few more. BTW, I was also thinking of plastic straws, seems like that might work, and if I'm under there measuring, I can start long and clip with diagonal snips to exact length then measure...
jc
jc
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Chronic Tool Dropper
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From: Bend, Oregon
What are these heights?
An interesting observation is that the factory heights don't give horizontal lower arms. I've always thought that was a good design goal for the reason you gave: least alignment variation in cornering and bumps.
The later WSM gives a procedure that removes tire size from setting the ride height and looks, correctly, at the difference between body height and knuckle height. In other words, don't set the fender height at all; set the angles of the suspension.
An interesting observation is that the factory heights don't give horizontal lower arms. I've always thought that was a good design goal for the reason you gave: least alignment variation in cornering and bumps.
The later WSM gives a procedure that removes tire size from setting the ride height and looks, correctly, at the difference between body height and knuckle height. In other words, don't set the fender height at all; set the angles of the suspension.
Sooo, with a known fender lip height=knuckle height on a particular car it should be close? I did have one piece of coat hanger wire that I cut to 175mm. But when I tried to fit it was a little too long. I will cut a few more. BTW, I was also thinking of plastic straws, seems like that might work, and if I'm under there measuring, I can start long and clip with diagonal snips to exact length then measure...
jc
jc
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After seeing Dr. Bob's collection of welding rods a few years ago, I made a similar set from coat hanger, they work just fine:
Recently Arnoud posted an ingenious adjustable ride height gauge, which is nice if you've got the caliper to measure it with:
Recently Arnoud posted an ingenious adjustable ride height gauge, which is nice if you've got the caliper to measure it with:
