STR Prep - Suspension and Alignment
#231
Quick question....if I don't have camber joints up front (yet) and I'm going to have the car realigned should I go for max camber and sacrifice caster to get there or max caster first and then see how much camber I can get. Currently the car is at -2.8 up front but caster is a hair below factory spec. I know from my previous s2k when we ended up going for more caster I could only get -2.5 up front. Which is better?
Steering angle is angle of the wheels.
So if we assume a typical steering angle of 10 degrees (I haven't looked to see what a typical steering angle would be - anyone else done this to see what steering angle is when the steering wheel is turned maybe 90 degrees or so?), then just as Matt said, you can expect a hair under 0.2 degrees difference in camber from 1 degree of caster.
So the ballpark you should be shooting for in my mind is trading 0.2 degrees of camber for 1 degree of caster. If you get more camber for that much caster then go with the camber, if you get less camber then go with the caster. Keep in mind the inside wheel will lose camber at the same rate from caster. In other words, for example, lets say you find you can add 1 degree of caster at a loss of 0.2 degrees of camber, so you're right on that line. In a turn at 10 degrees steering the outside wheel will have the same amount of camber either way. However the inside wheel would have 0.4 degrees more camber if you had done the camber option (because you added the 0.2 deg camber, plus you're not losing an additional 0.2 from camber loss from additional caster). Of course the inside wheel is far less important than the outside wheel. Also keep in mind obviously at 5 degrees steering you only get half(ish) the camber from caster, or at 15 degrees you get more camber. Plus of course you have to remember the unpredicability - with camber it's easier to balance front and rear traction, whereas if it's all in caster then at high turn angles you'll oversteer and at low turn angles you'll understeer. It's all a balancing act. But hope this helps you have a general idea.
My guess is that you're going to end up mostly maxing out camber, but then maybe giving up the last 0.1 or 0.2 degrees of camber for caster, but I haven't tried to max everything out on this car so I don't have experience.
#232
The deal I was hoping to get on some other parts fell through so I'm most likely going to be keeping my J's camber joints and therefore will be able to get max caster and the exact amount of camber I want. Looks like I won't have to give anything up. At least I learned a little something
#234
Thread Starter
#235
So I haven't played with rake much. Anyone that has, I'm wondering what your opinion is on how much it affects things?
My rear shocks are not as short as I'd like them to be, it looks like I was reaaally close to bottoming them out at the last event last year. And now I lowered the front bar setting two notches since then, so the car will actually roll even more (some quick calculations tell me around another .05" in the rear of spring travel).
Ride height is about 13" in front, and just a little more in rear, maybe 13.1". Spring rates are currently 800 F/700 R, Gendron hollow front bar now on 4/6, no rear bar. Last event last year I had this exact setup with the Gendron at 6/6 and it was understeer city, and like I said I was a hair's breadth away from bottoming out the rear shocks.
I don't want to bottom out the shocks. So to fix this, I'm trying to decide between:
1) Raising the rear spring perch another 0.2" or so and making no other changes. I want to raise it more than I probably need since raising it will make it roll more again plus I'd like to have a little more wiggle room.
2) Buying a miata bar for the rear and putting the front gendron at maybe 5/6 and tuning from there. That should get rear roll about to what it was before with the front bar at full stiff and no rear bar. Then only raising the rear height slightly, maybe another .1", just for wiggle room. This would just be a temporary solution since I'd really like to design an adjustable sway bar for the rear if I really want a rear sway bar, but I'm guessing the rates would be miata-bar-ish and I don't have time to do that right now.
So my question is, how do you think those two options will compare? I've got a pretty good idea of what the effect of the sway bar changes will be but is a difference of 0.1" of rear ride height really going to change anything balance-wise?
Pretty sure I'm going with option 2, but even then I'm adding some rake compared to now so I'm curious about the rake effects specifically.
Of course our test and tune is this weekend on sunday, and I've got tons to do (mostly non-car related) in the mext couple weeks so I really want to add as little as possible work.
Edited for clarity
My rear shocks are not as short as I'd like them to be, it looks like I was reaaally close to bottoming them out at the last event last year. And now I lowered the front bar setting two notches since then, so the car will actually roll even more (some quick calculations tell me around another .05" in the rear of spring travel).
Ride height is about 13" in front, and just a little more in rear, maybe 13.1". Spring rates are currently 800 F/700 R, Gendron hollow front bar now on 4/6, no rear bar. Last event last year I had this exact setup with the Gendron at 6/6 and it was understeer city, and like I said I was a hair's breadth away from bottoming out the rear shocks.
I don't want to bottom out the shocks. So to fix this, I'm trying to decide between:
1) Raising the rear spring perch another 0.2" or so and making no other changes. I want to raise it more than I probably need since raising it will make it roll more again plus I'd like to have a little more wiggle room.
2) Buying a miata bar for the rear and putting the front gendron at maybe 5/6 and tuning from there. That should get rear roll about to what it was before with the front bar at full stiff and no rear bar. Then only raising the rear height slightly, maybe another .1", just for wiggle room. This would just be a temporary solution since I'd really like to design an adjustable sway bar for the rear if I really want a rear sway bar, but I'm guessing the rates would be miata-bar-ish and I don't have time to do that right now.
So my question is, how do you think those two options will compare? I've got a pretty good idea of what the effect of the sway bar changes will be but is a difference of 0.1" of rear ride height really going to change anything balance-wise?
Pretty sure I'm going with option 2, but even then I'm adding some rake compared to now so I'm curious about the rake effects specifically.
Of course our test and tune is this weekend on sunday, and I've got tons to do (mostly non-car related) in the mext couple weeks so I really want to add as little as possible work.
Edited for clarity
#236
Jon,
I'm not sure what will be best for you, but I like my mx5 rear bar. I do suggest getting two 21mm or slightly bigger split collars to put on the other side of the pressed sway bar retainers that come on the mx5 bar. Mine moved laterally about 1/4" and it was causing the bushing lubr to slide out and the bushing to become dry. I ordered two aluminum ones from mcCarr to limit lateral travel on mx5 bar. I can get u the part number at a later time, but I think I went with13/64 to approximate 21mm.
See you Sunday.
I'm not sure what will be best for you, but I like my mx5 rear bar. I do suggest getting two 21mm or slightly bigger split collars to put on the other side of the pressed sway bar retainers that come on the mx5 bar. Mine moved laterally about 1/4" and it was causing the bushing lubr to slide out and the bushing to become dry. I ordered two aluminum ones from mcCarr to limit lateral travel on mx5 bar. I can get u the part number at a later time, but I think I went with13/64 to approximate 21mm.
See you Sunday.
#237
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So I haven't played with rake much. Anyone that has, I'm wondering what your opinion is on how much it affects things?
My rear shocks are not as short as I'd like them to be, it looks like I was reaaally close to bottoming them out at the last event last year. And now I lowered the front bar setting two notches since then, so the car will actually roll even more (some quick calculations tell me around another .05" in the rear of spring travel).
Ride height is about 13" in front, and just a little more in rear, maybe 13.1". Spring rates are currently 800 F/700 R, Gendron hollow front bar now on 4/6, no rear bar. Last event last year I had this exact setup with the Gendron at 6/6 and it was understeer city, and like I said I was a hair's breadth away from bottoming out the rear shocks.
I don't want to bottom out the shocks. So to fix this, I'm trying to decide between:
1) Raising the rear spring perch another 0.2" or so and making no other changes. I want to raise it more than I probably need since raising it will make it roll more again plus I'd like to have a little more wiggle room.
2) Buying a miata bar for the rear and putting the front gendron at maybe 5/6 and tuning from there. That should get rear roll about to what it was before with the front bar at full stiff and no rear bar. Then only raising the rear height slightly, maybe another .1", just for wiggle room. This would just be a temporary solution since I'd really like to design an adjustable sway bar for the rear if I really want a rear sway bar, but I'm guessing the rates would be miata-bar-ish and I don't have time to do that right now.
So my question is, how do you think those two options will compare? I've got a pretty good idea of what the effect of the sway bar changes will be but is a difference of 0.1" of rear ride height really going to change anything balance-wise?
Pretty sure I'm going with option 2, but even then I'm adding some rake compared to now so I'm curious about the rake effects specifically.
Of course our test and tune is this weekend on sunday, and I've got tons to do (mostly non-car related) in the mext couple weeks so I really want to add as little as possible work.
Edited for clarity
My rear shocks are not as short as I'd like them to be, it looks like I was reaaally close to bottoming them out at the last event last year. And now I lowered the front bar setting two notches since then, so the car will actually roll even more (some quick calculations tell me around another .05" in the rear of spring travel).
Ride height is about 13" in front, and just a little more in rear, maybe 13.1". Spring rates are currently 800 F/700 R, Gendron hollow front bar now on 4/6, no rear bar. Last event last year I had this exact setup with the Gendron at 6/6 and it was understeer city, and like I said I was a hair's breadth away from bottoming out the rear shocks.
I don't want to bottom out the shocks. So to fix this, I'm trying to decide between:
1) Raising the rear spring perch another 0.2" or so and making no other changes. I want to raise it more than I probably need since raising it will make it roll more again plus I'd like to have a little more wiggle room.
2) Buying a miata bar for the rear and putting the front gendron at maybe 5/6 and tuning from there. That should get rear roll about to what it was before with the front bar at full stiff and no rear bar. Then only raising the rear height slightly, maybe another .1", just for wiggle room. This would just be a temporary solution since I'd really like to design an adjustable sway bar for the rear if I really want a rear sway bar, but I'm guessing the rates would be miata-bar-ish and I don't have time to do that right now.
So my question is, how do you think those two options will compare? I've got a pretty good idea of what the effect of the sway bar changes will be but is a difference of 0.1" of rear ride height really going to change anything balance-wise?
Pretty sure I'm going with option 2, but even then I'm adding some rake compared to now so I'm curious about the rake effects specifically.
Of course our test and tune is this weekend on sunday, and I've got tons to do (mostly non-car related) in the mext couple weeks so I really want to add as little as possible work.
Edited for clarity
I as well be doing a test and tune soon. Hopefully I’ll have my new rear bar on before then.
#238
thanks guys, that's helpful. Noel, I thought you could just hammer those retainers over and then that would hold it, did you try that? If you did, then if you can send me that part number that'd be awesome.
#240
Just an FYI and observations. Many of us with koni's or similar modified the OEM mounts for use with 2.5" springs. Everything seats pretty well, but I noticed this winter that the top rubber insert inside the top hat was very deformed from the spring. Doesn't seem to hold up to high rates and daily driving.
I only check my rear's so far and they were both messed up. I'm assuming the fronts are the same or worse.
I only check my rear's so far and they were both messed up. I'm assuming the fronts are the same or worse.