15 replies to this topic

[Brendan O]

Hi,
I had a shop help me with an NB alignment and corner weights. The values are as follows:

Cross: 50.1%
Rear: 46.6%
Left: 51.9%

Fronts are at 2.5 deg camber, 4 deg caster, 0 toe.
Rears are at 2.5 deg camber, 0 toe.

The ride height is a bit high - the lowest corner (LR i think) is around 4 7/8" and the highest is one of the fronts (can't remember which one) at 5 1/8". That is why they could not get 3 deg camber on the fronts. It was a miscommunication between us i think and they have gone to runoffs so i can't get them to adjust.

Now it is back home and I don't have access to scales and i have a track day in one week. I was wondering if i could simply turn the spring perches an equal number of turns (3 or 4 full turns) at all 4 corners to get the car lower. My thought was that the cross might stay the same (50.1%) if the angle of the shocks wrt veritcal is the same front and rear. This would also increase front camber which is good but it would also increase rear camber which may not be so good (according to JD setup guide ver 2).

Or should i just leave as is since its good enough for now? I am a newbie and am still learning how to drive.

thanks

[Flyntgr]

I'm no expert, but am learning, too. Jim's setup guide is excellent to learn how to adjust ride height and then crossweighting the car while keeping ride height the same. Basically remember this when changing crossweight: whatever you do to the RF and LR, do the exact opposite to the other diagonal, LF and RR, in order to keep the car level. If you want a higher crossweight, raise the RF and LR and the opposite on the other 2 corners. If you want to decrease CW, go DOWN on the RF and LR, UP on the other corners. Going UP on a corner increases the weight that corner carries.

My personal experience is that 1 turn equals about 1/8" change in ride height WHEN turning all 4 corners as above. If I want to change ride height on all four corners by 1/4", I make 2 turns up or down.

I learned from Davew that there is another consideration, though. You want to use the four corner weights in this manner: add RF and LR, then add LF and RR, subtracting the smaller total from the larger total to see how much weight difference there is between the diagonal corners. That difference, in pounds, is "the cross" [NOT the Cross Weight, but "cross" meaning "difference"]. You want the "cross" to be within 10 lbs, and within 0 pounds would be totally "square". You want square! According to Davew, you should try for a 50% cross weight till you learn when/how to change Cross Weight to your advantage. Get to within .1% and call that 50% (49.9 or 50.1% range is good enough, but I have hit exactly 50.00% on more than one occassion).

For my '99, Davew recommended a little "rake", which means the front is lower than the rear by about 1/8". For my car he recommended 4 3/4" front and 4 7/8" rear.
This might be different for your car and track.


If you level the car and THEN lower all four corners by the same amount,exactly the same amount, then the car should remain level. Re-check corner weights and ride heights at each corner to make sure. If you make a big change in ride height, I would recommend a re-alignment, and if you lower it, you should be able to get more camber if you want it.

Take this post as my own personal experience, not "gospel". Some authorities on this site will probably post soon, and you should take the experts' advice over mine. In the meantime this should give you something to think about if I haven't confused you or gotten this wrong. You will probably find a difference of opinion on some of the above. Happy Adjusting!

See my recent post in Spec Miata above refering to SAI being off.

[Johnny D]

Some say you never stop working on your car, you just have to stop and go race it.

You know what's wrong. Are you okay with that?
Some would say yes.
Some would start at step#1 in JD's setup and do it all over again to make it right.
J~

[HoneyBadger - BrianW]

If you are still working on coming up to speed in the car, I would just drive it like it is. The changes that you would make, would be, in general, small changes to increase the performance of the car. You will only notice these if you are already pushing the car close to the limits. If you have a car that you know is square, I would just drive it like it is for the time being. YMMV

[Brendan O]

I just noticed there is a setup forum so maybe moderators will move this thread there.

Flyntgr - thanks so much for the detailed response. I was not sure how much one turn was so knowing it is around 1/8" helps alot. You also cleared up my understaning of cross weight.

I think I will go with Johnny and Brian. Since i am no where near 10/10ths (more like 6/10ths), i guess I will leave as is for the weekend - it should be good enough for a biginner to keep learning. Basically, I have run out of time - why does that keep happening to me

One more question - does anyone think having rear at 46.6% will cause excessive oversteer? I guess if I brake AND turn then this will increase liklihood of oversteer. Is rear=46.6% within "normal" range - at least for learning?

thanks again

[Keith Novak]

You shouldn't have trouble with it beeing too loose. Mine comes out to 47%. What I found with my '95 was that with the front at that height, I couldn't get the car to turn in on the tight corners. It was a handfull.

If I had your car, I'd drop the front probably 2 turns and call it good. For the way I drive at least, it would be a more enjoyable ride. I've driven it almost exactly like you have yours set up but I like it much better with the front lower. You could measure everything first, drive it for a session, then take 2 turns off the front and see what it does.

You do want it a bit loose. Not crazy tail happy but you need it to rotate if you plan on going fast. The best adivice I ever got on how to go faster went something like this: You need to slide the car more. The really fast guys slide it everywhere and it's like a game of chicken. Pick a nice sweeper with room to make mistakes (for me T4 at Portland) take a deep breath and drive into it too fast. Not stupid fast but faster than you think is right. When the car slides, give a quick lift on the gas then shove it back into the floor. The car should rotate, catch and turn back in. It's a Miata, not a real race car so a quick little lift won't instantly throw you into a horrible spin. What I found was that while I could dial in a speed that in a neutral drift at WOT, the car would track all the way to the track edge but once I started to learn how to rotate it, I could go in even faster, use more throttle with an occasional throttle correction, get the car to track a tighter arc, and STILL have more room left over on the exit to practice going even faster. (Thanks Bruce!)

[Flyntgr]

I believe Kim is right: lower the front equally a turn or two and you'll see your car turn-in better. You should brake IN A STRAIGHT LINE before the turn, NOT during the turn. When the front of the car dips down it will turn better. To a lesser degree, on some turns the car will turn-in if you simply lift the accelarator pedal. Best of luck improving your times.

You shouldn't have trouble with it beeing too loose. Mine comes out to 47%. What I found with my '95 was that with the front at that height, I couldn't get the car to turn in on the tight corners. It was a handfull.

If I had your car, I'd drop the front probably 2 turns and call it good. For the way I drive at least, it would be a more enjoyable ride. I've driven it almost exactly like you have yours set up but I like it much better with the front lower. You could measure everything first, drive it for a session, then take 2 turns off the front and see what it does.

You do want it a bit loose. Not crazy tail happy but you need it to rotate if you plan on going fast. The best adivice I ever got on how to go faster went something like this: You need to slide the car more. The really fast guys slide it everywhere and it's like a game of chicken. Pick a nice sweeper with room to make mistakes (for me T4 at Portland) take a deep breath and drive into it too fast. Not stupid fast but faster than you think is right. When the car slides, give a quick lift on the gas then shove it back into the floor. The car should rotate, catch and turn back in. It's a Miata, not a real race car so a quick little lift won't instantly throw you into a horrible spin. What I found was that while I could dial in a speed that in a neutral drift at WOT, the car would track all the way to the track edge but once I started to learn how to rotate it, I could go in even faster, use more throttle with an occasional throttle correction, get the car to track a tighter arc, and STILL have more room left over on the exit to practice going even faster. (Thanks Bruce!)

[Brendan O]

Keith - that is a good idea. I will leave as is for Saturday and then lower the front a couple turns and see how it is on Sunday. That way I will have a good comparison and I will become more knowledgeable about how one change affects the car.

Regarding a little loose and going faster, I am always amazed at some of the YouTube videos with really fast lap times. I watch their hands and they are contantly putting in counter steer as the back end gets a bit loose in the middle of a corner (both tight corners and high speeed sweepers). When I drive, I rarely need countersteer since I am not at 10/10ths. So it seems the really fast guys are a little loose. I guess I just need more seat time to slowly learn how to do it safely. The high speed sweepers are a bit scary though.

One more question - do the little 4mm hex set screws in the spring perches really need to be tightened before going back out on track. My thought was that unless you can lift the rear inside wheel in a corner, the weight of the car at all four corners should keep the spring perches from rotating.

thanks again
Brendan

[James York]

Brendan,
FYI, when you lower the front end, it will change the toe (out), so you will be getting more than one change unless you reset it after you lower.

I personally don't use the set screws in the spring perches and don't know anybody that does. They end up getting impossible to remove later just when you are trying to do a setup change in a rush. Some folks do put some gorilla tape over the bottom of the perch to keep them from getting accidently turned when the car is up in the air though as a precaution.

[Tom Hampton]

One more question - do the little 4mm hex set screws in the spring perches really need to be tightened before going back out on track. My thought was that unless you can lift the rear inside wheel in a corner, the weight of the car at all four corners should keep the spring perches from rotating.

thanks again
Brendan

What set screws?

[Brendan O]

I didn't know about getting toe out - maybe i should just leave it alone then for the entire weekend.
Gorilla tape sounds like a good idea - thanks.

[Tom Hampton]

Brendan,
FYI, when you lower the front end, it will change the toe (out), so you will be getting more than one change unless you reset it after you lower.

Does anyone have "typical" bump-steer charts for NA and NB cars? Like fatcat's camber vs RH graphs?

[Keith Novak]

You currently have zero toe out. Many people prefer a 1/16th or so. It's not going to make your car veer violently off the road or anything. Either that or you can change your toe pretty easily.

[HoneyBadger - BrianW]

I personally don't use the set screws in the spring perches and don't know anybody that does. They end up getting impossible to remove later just when you are trying to do a setup change in a rush. Some folks do put some gorilla tape over the bottom of the perch to keep them from getting accidently turned when the car is up in the air though as a precaution.

I have noticed that my rear shocks tend to lower themselves. I even started checking ride height and setup at the last TWS race to make sure I wasn't going crazy (no comments). I havent resorted to putting the set screws in yet, but I have been using gorilla tape. I figure between the tape itself and the sticky residue it leaves making the perches harder to adjust it should fix the issue.

[Keith Novak]

Maybe not this weekend, but it is good practice to go out and just try different stuff and see how it drives. It has to make a big enough difference that you can notice it. For example if experimenting with the sway bars, try full stiff in the rear then full soft rather than middle so the change is really obvious but experiment, make mistakes, see what it does, forget about trying to set your best time for a bit, and most of all have fun with it.

It struck me when learning to CW my car how little a change would significantly alter the numbers. That's on scales meticulously leveled in my garage and the track will never be that level. If you only practice driving the "ideal" line, how are you going to cope when it's oiled up or you're 2 wide there and can't drive on it. You may hit something in a race and wind up driving many laps with a rear wheel 3/16 toed out. One of the most fun parts about SM is the racing is very close and in the heat of battle you spend a lot of time trying to drive fast on parts of the track you wouldn't pick given a choice.

When experimenting with more sliding you can start out pretty safely. If you pick the right corner, you can get the car a bit uncomforably bent out of shape early so if you have to back all the way out to gather it up or even put both feet in you have plenty of room. I'm still learning how to do that too but I'm much more comfortable doing it now that I've spent time experimenting and practicing using the wheel and throttle to correct oversteer and understeer...but sometimes I do wind up going agricultural.

Whatever you decide, have fun this weekend.

[Brendan O]

Thanks Keith - very good advice. I agree it is better to experiment to see how changes affect the car and forget about lap times for a little while. So even if i will get a bit of toe out when lowering front i will probably still do it just out of curiosity. The more experience i get with differnt handling characterisitcs, the more i will be able to tell if something is wrong and more importantly, i'll have a good idea of where to look first to fix it. I can always raise the front back to zero toe if i really don't like it.

I think there are several medium speed corners at Barber Motorsports Park where i can practice sliding safely. Like you said, I just need to start out slow and then increase speed as i get more confidence (in me and the car).

Any how, thanks for the advice - i hope i will have lots of fun this weekend without any "incidents" that involve bent metal

Brendan