09-28-2020, 10:07 AM | #1071 |
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Based on my experience with measuring off of the wheels, I am not convinced that wheels provide a more reliable place to measure than the stands. Many wheels (such as the turbo twists) do not have a reliable spot that you can put the caliper against to measure on the rim. Furthermore, you need a level on your caliper because even a minimal angle there can have a significant impact on the reading.
The stands are MUCH easier to measure with than toe plates because they are hard mounted. All you need to do is pull the tape measures tight to get a precise measurement. No averaging needed. They don't move around, they aren't leaning against a soft tire, and they won't fall off the car. There are two different places that you measure on the hub stands: 1) Tape measures. This is how you get your actual toe. 2) Thrust angle strings / ruler. The key is to get these the same on each side. In the case of the Porsche, that means that "straight" is about 1/4" in on each side. You are getting these the same on each side, you are not getting them square. Track width doesn't really matter, as long as the hubs themselves are squarable. However, when you know where you are on #1, you can reference #2 for a live readout of changes as you make them. Something that you simply do not get while working on strings. The other thing that is nice is that you have a live readout of "trapezoid." The goal is not "square," but rather isosceles trapezoid. Personally, for me, while I can see a rational argument that strings *could* be more accurate, my experience with these is that the stands are real world much more accurate for me. I've tried laser strings (horrible - the laser plane loses focus). I've used smart strings. E30s, I just ballpark the tie rods until it drives straight and check my work with toe plates (since the rear is non-adjustable, thrust angle is kind of irrelevant unless you are concerned that a trailing arm is bent). That said, I know that you are more methodical than I am. I wouldn't be surprised if you're better at this. Strings are a struggle for me.
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09-28-2020, 10:32 AM | #1072 |
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When you say "trapezoid," are you referring to the fact that the front and rear track widths are different? How do you know how much they differ? I can see how this would all work if you were starting from a known reference (i.e. a calibrated alignment rack) but otherwise, you're kind of guessing.
With strings, assuming the strings are relatively close to the tire / wheel (the tire being the limiter, obviously) the angle of the scale when you take a measurement doesn't really affect it much. I don't even use a level - it's similar to the technique one uses when measuring a cylinder with a dial bore gauge - you look for the smallest readout on the dial. Same thing with the scale - you move it up and down until you see the smallest reading. That, by definition, is level. This of course assumes that the strings are level, but again, it's really very easy to verify that during initial setup. This discussion is interesting to me because I make so many small alignment changes to the competition car(s) and commercial alignment setups are frequently so far off (or they shit the bed when a vehicle has excessive camber, as mine does). I literally check my alignment before and after every event, so being able to do that quickly and very accurately is essential. You should stop by some time and I'll walk you through my method to show how easy it is. The bar is well-stocked |
09-28-2020, 11:05 AM | #1073 | |||
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And yeah, one of the reasons why I DIY this is that even a shitty alignment is usually better than I'll get from paying someone. And dealers do the worst alignments in my experience. And I definitely should do that. And maybe bring the stands too so you can see what I'm talking about!
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09-28-2020, 11:18 AM | #1074 |
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To clarify a little...
The first picture shows "square" on the stands. You will never see that real world. Instead, you'll see something more like the second picture. The key is that should read the SAME on both sides. As long as the reading is the same left to right, your thrust angle is correct. Note that the reading will not be identical on different axles unless you have identical toe readings. The built in rulers are used ONLY for thrust angle and watching toe movement. Precise toe measurement is off the tape measures. (Edited to upload correct second picture.)
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09-28-2020, 12:03 PM | #1075 |
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I think that just reinforces my concern that there's just no way to verify that the stands are true, and given how they're constructed, it's almost certain that they're not.
FWIW I almost never bother to use a caliper anymore during alignments. I use a 6" metal scale marked every 1/32". |
09-28-2020, 12:08 PM | #1076 | |
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All that's needed to check them is a known flat surface - I'm sure Wallgren has one.
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09-28-2020, 12:15 PM | #1077 |
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I'm supposed to "test drive" a set of hub stands that a fellow competitor has, so I can do a back to back alignment check with the string setup attached.
If Eric has a surface plate and an indicator you could check them. |
09-28-2020, 12:52 PM | #1078 | |
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I just looked up the tolerance specs for aluminum wheels, and the ranges given are surprisingly large. No wonder BMW wants people to align off the hubs using their special heads.
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09-28-2020, 12:59 PM | #1079 | |
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10-02-2020, 12:56 PM | #1080 |
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Businessman Zef Eisenberg dies while trying to break British land speed record:
"The founder of health supplement firm Maximuscle, Eisenberg was driving a Porsche 911 Turbo S car at Elvington Airfield in Yorkshire, northern England, when he lost control of the vehicle." https://www.cnn.com/2020/10/02/motor...spt/index.html |
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