Suspension Geometry maximums and problems

[gslender]

Hang on, you're now saying the aligners were trusted and probably good at their trade, but somehow unable to explain why the alignment is poor? I'd expect a good place to either outline the problem or at least tell you why they did what they did, especially if it was against a request.

Either the car had suspension issues (bent) or they did a avg job. There isn't really a reason I can think of why they'd leave it like that, unless they thought you would prefer a very pedestrian alignment!

G

[StuwieP]

I'm trying to reconcile the knowledge that the owner of the shop is someone who has plenty of experience, whom my dad swears by and who races himself, with the fact that the figures in front of me, while in part are probably due to poor communication, are completely off both what I asked for and, in the case of the caster, what the factory specified as minimum/maximum allowances.

I also think they see a lot of cars through that are just after a pedestrian alignment. Maybe that contributed to the toe figures, in particular (reading them as "each" rather than "total" -again, I wasn't specific and just assumed it would be read as total)

I didn't push hard enough for an explanation at the time, I was hot (been 37 here), tired of waiting and had to get to work. I also wanted to fully grasp the mx5's suspension before I called in and demanded an explanation. Might have contributed to the rant-like character of my posts. Will call tomorrow, prepared with knowledge.

I haven't been told that the suspension is bent. I'd hope that I would have noticed, if not then my mechanic or these guys might have mentioned it.

Cheers guys
Stu

[project.r.racing]

I think you'll need to get another alignment done sorry. This is what I have taken from the thread so far:-

You asked for an alignment, not really know what you were asking for,
Aligner did the job that you asked for,
End result was not what you wanted in you mind, but what you asked for verbally.

Now you have the knowledge, when you return again, you'll be able to explain what you actually want without error.

[Charlie Brown]

OK let me have a go at this.

The standard Mazda Specifications for the NB (but the NA is similar) are:

Front
Caster: 4.83 deg min. to 6.83 deg max
Camber: -1.10 deg to +1.10 deg
Toe: -0.05 deg to +0.35 deg

Rear
Camber: -1.78 deg to +0.22 deg
Toe: -0.05 deg to +0.35 deg

You can see from these figures that the Caster has a range from 4.83 deg min. to 6.83 deg max, the 6.83 is more caster to answer your question Stuwie.

Over the years some people on this site have reported that on stock NA’s & NB’s the maximum front negative camber they could achieve was under 0.5 negative. This is obviously your case too, although you maybe right in suspecting that the aligner wasn’t up to doing a good job.

To get a quality alignment, and as it has been said above, this should be around the $90 – 100 range for all four wheels, I’d contact the MX-5 Club of Victoria and ask the Motorsport Captain who’s the best to go to.

A precision aligner will make allowances for your weight without you in the car (easily worked out by hooking up the equipment and checking the figures with you in and out of the car before the alignment starts) or by allowing you in the car thought out the alignment or by weighting the car with sand or gravel bags to simulate your weight. You do this so the figures achieved match side to side.

Being a stock NA MX-5 and you wanting it to feel alive and assuming you can only get 0.5 degrees negative camber up front, I’d set it up with these figures.

Front Camber: -0.5 degrees
Front toe in: 1.5mm total (0.75mm each side)
Castor: Maximum you can get with the -0.5 camber. You should be able to get around 5 degrees.
Rear Camber: -1.0 degrees (if you can get more negative camber up front, increase the rear negative to 0.5 degress more than the front)
Rear Toe in: 2.0mm total (1.00mm each side)

Once you head to the track these figures will change as you start to modify the handling characteristics of your car.

[StuwieP]

project.r - while it is certainly obvious that I don't fully understand the intricacies and workings of suspension and geometries, my knowledge when I asked for the alignment, before this thread, was as follows:
camber - during cornering negative camber allows more contact between the loaded (outside) tyre and the road as the car experiences body roll = good. Better cornering. Too much camber for the roll experienced results in less contact than ideal, and on straights impairs acceleration and, more importantly IMO, braking, as well as increasing wear on the inside of the tyre.
toe - toe in improves straight line stability by reducing or removing the occurence of bump steer, as the wheels are exerting opposing forces at neutral. Toe out aids corner entry and results in bump steer as well as seeing the car more likely to tramline. Makes the car a little less 'pedestrian' - twitchy and alive. Toe out on the rear of an mx5 is bad because it induces excessive oversteer - the outside wheel during a corner wants to take the 'line' it describes, rather than following the front. If the alignment isn't done with ballast, the drivers weight will add a little toe out.
caster - adds camber as the wheel is turned, reducing the need for drastic negative camber on the front. that's all I knew caster did (didn't know HOW, or the other functions it serves)

So, I would like to say that in a basic sense I knew what behaviour I was asking to have, and in some ways (cambers are all off, including rears which obviously wouldn't be affected by caser settings -I knew that!-, caster is way out) I didn't get what I was asking for at all. In others (toe) I got what was written because I wasn't clear enough.

Charlie, thanks. I think it may have been your geometry I used in the first place. Any reason why some NAs seem to have such a comparatively "limited" range of adjustability?

Cheers
Stu

edit - some typos

[gslender]

Any reason why some NAs seem to have such a comparatively "limited" range of adjustability?

Ride height - would explains why some can, and some cannot. Less ride height means better camber, but starts to muck up overall geometry.


Whilst that would mean they aren't stock, but some cars can also sag and some might not know they have slightly lower King springs and non std shocks.

G

[project.r.racing]

project.r - while it is certainly obvious that I don't fully understand the intricacies and workings of suspension and geometries, my knowledge when I asked for the alignment, before this thread, was as follows:
...
So, I would like to say that in a basic sense I knew what behaviour I was asking to have, and in some ways (cambers are all off, including rears which obviously wouldn't be affected by caser settings -I knew that!-, caster is way out) I didn't get what I was asking for at all. In others (toe) I got what was written because I wasn't clear enough.

thats not what i meant, nor was i trying to have a dig at you.
knowledge of what those thing are is great, but in the end it isn't gonna help you with your specific car. cars are all different, and how various changes in 1 aspect may change another one. which you have found out through this thread.

the specs you are asking for, are they even possible on a stock setup? can the end result you are looking for be archievable or do the require offset bushes in the upper arms also? need to really find that thread hey?

[Charlie Brown]

Any reason why some NAs seem to have such a comparatively "limited" range of adjustability?

It's not only NA's that sometime have this adjustability problem. Some NB's and NC's also suffer from this. The comments I saw a number of years ago said it's due to production line assembly tolerances. In other words, the robots didn't get the metalwork that holds the suspension pieces in exactly the same spot everytime on every vehicle.

Years ago, one of the Forum members cars maxed out the front camber at a postive +0.01, so I wouldn't get overly concerned if you can't get more than 0.5 negative on a stock NA. If you want more then you need to start modifing either by lowering the car or putting in offset bushes. In NSW that puts you straight into the modified class when you do Club Days.

[NitroDann]

That's hardly fair. Get a smash repairer to pull the sub frame just enough to hit maximum factory recommended settings.

Dann

[StuwieP]

project - no sweat, wasn't an irate response by me, I didn't take it as criticism - it's partly true anyway. Just thought I should clarify given the amount of info that has just been passed on to me, that while much of it was new I did try to grasp the basics before I got the alignment, honestly hoping to avoid the very issue before me. But yes, the way they all affect each other in terms of actually achieving the alignment was WAY beyond me.

I was under the impression that the specs were quite mild, again I think the biggest problem is the toed-in stance, rather than camber and caster angles, and that came down to poor communication on my part and an apparent unwillingness to confirm with me by the shop (if I was given something that could go 2 ways, one of which would be significantly different to the other, I would definitely confirm with the customer exactly which of those two ways it was. Not like I was more than 30m away the whole time. 30 seconds effort could have avoided all this...)

The thread was the alignment post in the tech guides here:
http://mx5cartalk.com/forum/viewtopic.php?f=76&t=15398
I was looking in this sub-forum (wrong place). There are links to it in almost every alignment related topic on this entire forum Now it's in my "I'm confused - please help" thread.

Cheers
Stu