square spring rates vs "traditional" stagger
Nov 9, 2015, 06:14 AM
#136
Evolved Member
It looks like the OEM tie-rod sits a little lower then the control arm (from parallel) so that with the rear steer geometry, the car toes in under compression.
You really want to just be able to adjust tie-rod height since caster, camber, and tow adjustments all impact the bumpsteer curve to some degree.
Looking at the racefab arms, it doesn't look like the balljoint is on the right angle for use with the factory hub carrier?
You really want to just be able to adjust tie-rod height since caster, camber, and tow adjustments all impact the bumpsteer curve to some degree.
Looking at the racefab arms, it doesn't look like the balljoint is on the right angle for use with the factory hub carrier?
Nov 9, 2015, 06:21 AM
#137
Evolved Member
I'd be impressed if you're evaluating suspension changes while maintaining constant camber under load. Most people don't reset alignment after making small ride height/rake changes. Some people do reset static camber and toe settings after making a ride height change and that is better but still doesn't give you the full answer. changing the ride height changes where in the camber curve you operate and the curves are not always linear. Specifically, when you lower the rear the camber curve gets more aggressive, so without changing anything else you will operate with more negative camber on the outside rear tire at max lateral load, even if you start off with the same static camber setting. the car will be more pushy as a result of that camber change at full load.
I have also done the opposite experiment, where I kept the lateral load transfer distribution constant after accounting for the change in roll center height before and after a rake change, with the results still showing substantial balance changes with changes in rake even though the load transfer was the same.
I have also done the opposite experiment, where I kept the lateral load transfer distribution constant after accounting for the change in roll center height before and after a rake change, with the results still showing substantial balance changes with changes in rake even though the load transfer was the same.
In regards to rear camber... you really need to stop with these examples of changing multiple variables and blaming the effects on a single variable. Based on your example, I don't think you have ever modeled suspension geometry before.
I also find that last bit rather hilarious. And again, unless you modeled your geometry to confirm your assumptions, I don't think you can reach those conclusions on load transfer.
Nov 9, 2015, 08:12 AM
#139
Is there anyone willing to walk me through taking measurements of my car? I would like to figure out where my CG is, roll center, etc.
without this information I'm pretty much make my changes based on feel and the knowledge of others which seems to be working but I would rather have hard data to back everything up.
I have no problem paying for the time and information.
without this information I'm pretty much make my changes based on feel and the knowledge of others which seems to be working but I would rather have hard data to back everything up.
I have no problem paying for the time and information.
This paper from 1991 had four different laboratories measure CG height and found that even the professional laboratories differed by several inches: http://deepblue.lib.umich.edu/bitstr...pdf?sequence=2 . If you can minimize vehicle compliance (coilover compression, etc.) it might help a bit.
Roll center is a virtual point calculated from suspension geometry, so you have to model up the suspension. I still haven't done this yet so take this more as a starting point than a guide, but here was my plan:
0) Remove all of the suspension components from the car and carefully measure/model all of them.
1) Get the still stripped car elevated and level on a very level and flat surface.
2) Put heavy paper down on the floor underneath the car and get it firmly stuck in place so that it can't move at all until you're finished.
3) Use a plumb-bob on a stiff, unstretchable string to plot the X-Y positions of everything you might want to measure on the car on to your paper below. Measure all suspension mounting points as precisely as possible.
4) Also measure the Z position of all of the same points above. Either very carefully measure the length of the plump-bob + string up to the point you want to measure, or I've heard of people using a long tube filled with water + surfactant as a remote height measurement level.
5) Use the marks on the paper and your height data combined with the models/measurements of the suspension parts to construct a model of the suspension geometry.
Again, I haven't actually done this so I could be completely wrong or off the mark on some of these steps. But I've found that the best way to get proper information on the internet is to post up the wrong solution and wait for everyone to correct you, rather than to just ask in the first place, so here we are.
Nov 9, 2015, 05:16 PM
#141
I still haven't done this yet so take this more as a starting point than a guide, but here was my plan:
0) Remove all of the suspension components from the car and carefully measure/model all of them.
1) Get the still stripped car elevated and level on a very level and flat surface.
2) Put heavy paper down on the floor underneath the car and get it firmly stuck in place so that it can't move at all until you're finished.
3) Use a plumb-bob on a stiff, unstretchable string to plot the X-Y positions of everything you might want to measure on the car on to your paper below. Measure all suspension mounting points as precisely as possible.
4) Also measure the Z position of all of the same points above. Either very carefully measure the length of the plump-bob + string up to the point you want to measure, or I've heard of people using a long tube filled with water + surfactant as a remote height measurement level.
5) Use the marks on the paper and your height data combined with the models/measurements of the suspension parts to construct a model of the suspension geometry.
Again, I haven't actually done this so I could be completely wrong or off the mark on some of these steps. But I've found that the best way to get proper information on the internet is to post up the wrong solution and wait for everyone to correct you, rather than to just ask in the first place, so here we are.
0) Remove all of the suspension components from the car and carefully measure/model all of them.
1) Get the still stripped car elevated and level on a very level and flat surface.
2) Put heavy paper down on the floor underneath the car and get it firmly stuck in place so that it can't move at all until you're finished.
3) Use a plumb-bob on a stiff, unstretchable string to plot the X-Y positions of everything you might want to measure on the car on to your paper below. Measure all suspension mounting points as precisely as possible.
4) Also measure the Z position of all of the same points above. Either very carefully measure the length of the plump-bob + string up to the point you want to measure, or I've heard of people using a long tube filled with water + surfactant as a remote height measurement level.
5) Use the marks on the paper and your height data combined with the models/measurements of the suspension parts to construct a model of the suspension geometry.
Again, I haven't actually done this so I could be completely wrong or off the mark on some of these steps. But I've found that the best way to get proper information on the internet is to post up the wrong solution and wait for everyone to correct you, rather than to just ask in the first place, so here we are.
Just some feedback.
1. Level and stripped, yes. Flat level floor...meh
Small angle approximation tells you that this isn't that big of a deal. If you have like 1"/foot grade or something, yeah it might be trouble, typical garage floor should be fine though. Also, you'll be taking relative measurement too so even if the car isn't perfectly level, you can account for it...
2. yup...get lots of paper...I found like 3' wide rolls of brown paper at the craft store for cheap.
3. Plumb bob + some way to secure the string to the body. You actually want the string very compliant though. Just make sure it's not touching anything when you mark up the a paper and it's come to a complete rest.
4. This one can be tricky. Too small of a hose and surface tension can cause problems. Stick a 3' machine rule to the wall and tape the hose up next to it for your measurement. Raise the other end to put the muniscius at the height you want to measure. I liked taping it up and then standing back and making sure everything stayed still then took the measurement.
5. Establish a datum plane/line to measure from.
7. Record all measurement. Remove paper, reset height guage. Repeat 1-4 two more times... Toss all the data in excel and see where you messed up...Measure again if you have a lot of scatter.
8. Bounce it off me if you want and we will compare numbers. I'm not in to giving away A LOT Of my time...but I'm 100% willing to do some peer review if you are interested.
Nov 11, 2015, 11:42 AM
#146
Evolved Member
Nov 12, 2015, 02:41 PM
#147
I've seen it for other cars. What I've seen was extremely detailed....PAGES and PAGES of diagrams and dimensions. It had all the critical chassis points dimensioned out along with acceptable tolerances.
I would imagine somebody working in a collision repair shop that does frame straightening could get it if it does exist for the Evo.
http://www.blackhawkcr.com/frame-mea...nsion-data.asp
I would imagine somebody working in a collision repair shop that does frame straightening could get it if it does exist for the Evo.
http://www.blackhawkcr.com/frame-mea...nsion-data.asp
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