I set up my four wheel align ment for next week. I had a quea

[patrickt]

The MT statement that they're just as good as my Yokos? Well, you may be right -- I don't know, they might even be better. The last thread I can remember on MTs I don't think there were a lot of responses. But I haven't heard a negative word on the Avons in any regard (and you know how I enjoy needlessly pissing away dough on my car). But, since you do tend to be more right than wrong, usually; before I buy them I'll look at the MTs as I think I recall that a new MT came out in 15" just last year. I'm not sure on that, but I think I remember that.

[Cobra #3170]

The debate on corner weights, ride height and suspension alignment and what to do first is somewhat confusing because they all interact with each other.
I usually start with ride height and corner weights as suggested by Rick and then have to go through the whole process about 3-4 times before everything is correct. small changes in camber can effect corner weights and changes in ride height will effect camber, camber changes effect toe settings ect ect. Getting the bump steer right also effects rear caster, and rear toe. I think the best advice is from ERAChas, if the car is just being driven on the street and maybe an occasional track day basic settings will work fine, no need to go nuts on the details because you won't notice the difference. The main thing is to make sure nothing is way off left to right, camber and caster should be close to equal, ride heights left to right equal with a forward rake angle and corner weight should be fairly close side to side, since it isn't a formula car it will always be heavy on the drivers side but that's OK as long as there are not huge differences IE more than 75-100 pounds. If you scale the car the scales have to be perfectly level side to side or you will get bogus readings for weights and camber if you measure alignment on the scales. Tire pressure and tire diameter differences can also adversely effect your setup and throw off the settings. I just spent the last two days chasing an alignment problem that was related to my garage floor being off side to side and front to rear. I shimmed the platforms and checked them with a really long bubble level and also a digital level but neither was good enough to catch the problem, I finally used a surveyors laser transit and got the right heights for each scale pad then all the corner weights and camber settings came in as expected. Settings are usually dictated by the chassis design and tires, radials like negative camber, toe in gives stability both front and rear, the basic settings mentioned elsewhere in this thread would probably work very well for you.

Originally Posted by ng8264723

Any recomendations on settings? I know the owner of the shop and can tyell him what to dial in. By the way the car is running very well. Boy does it ever attrack attention. A few young girls stopped today to take pics
chris

[67JET]

Hey Jerry
I'm interested in getting my car set up. I'm sure it's all screwed up because i just totaly rebuilt it over the last year. If i bring it down to Chicago what would you charge to tune it in? I'm just going to drive it around on the street and maybe Road America if i get the chance. I'm not as hardheaded as Patrick, but let's face it he has 2 rollbars -- that can't be normal. PM me with some information and pricing. It might cost alittle bit more for you to let me help but i would like to learn how it's done.

[scottj]

Originally Posted by patrickt

I'm thinking something more like Circle Track magazine

Here's the Circle Track article you requested.

http://www.circletrack.com/chassiste...ght/index.html

[RodKnock]

Originally Posted by ERA Chas

You've taken this 'poser' stuff to new depths. Even Ferrari / Porsche owners conclude we're ass-clowns based on what can be read here.

Them's fighting words. Where are these foreign car owners that think we're ass clowns?

Chas, BTW, my oil is $8/quart and my 110 Sunoco race gas is about $6.35/gallon. I also plan to buy Avons when my Yoko's age out. I want a V-rated radial tire under my behind. OK, OK, I'll get back to my "Ass-Clown Anonymous" meetings ASAP.

Third roll bar...that was funny.

I had my car corner balanced and weighed, and somewhere in there they set the ride height, but I have no clue what order they did it in.

[Tom Kirkham]

Here is a primer for setting up a Spec Miata for someone just starting out in racing. Before you laugh too much this is a highly competitive class...
The ideas are what is important not the numbers...

http://www.specmiata.com/download/sm_setup_guide_v2.pdf

For those who have never raced and laugh at Spec Miatas
http://www.youtube.com/watch?v=b7iUKaPlBl8

[ERA Chas]

3170,
Thanks for weighing-in here with your great project. I'd much rather see far more content like yours and how you improved your car and solved problems than floor mat threads and 'scientific debates'.

Your only flaw is that your car is NOT a replica...

[patrickt]

Originally Posted by ERA Chas

You go to restaurants...

Chas, tonight when they brought me this I thought of you. Now the Blackberry snapshot really does not do it justice. Two lobster tails over a curry of crab leg, rice and sweet corn. Somehow I thought it would bug you if I posted a pic of it.

[RodKnock]

Originally Posted by patrickt

Chas, tonight when they brought me this I thought of you. Now the Blackberry snapshot really does not do it justice. Two lobster tails over a curry of crab leg, rice and sweet corn. Somehow I thought it would bug you if I posted a pic of it.

It bugs me a great deal. It looks like vomit. BTW, life must good. Lobster tails, crab leg, etc.

I'm hungry now. Vomit or not.

[Excaliber]

Just make sure the ride height is squared away and go get an alignment, it will be "close enough" in most cases when you start with a quality built car to begin with. Like an ERA, or even,,, a Kirkham.

Having done a few corner weight jobs I can say this, if you get to picky about perfection you will be doing the job over and over for at least a month and STILL not get it perfect! Change tire pressure 1 pound in any given tire, BAM, game penalty, re-adjustment required.

[Z-linkCobra]

There are 2 schools of thought here. Scott is obviously coming from a major circle track background on his techniques. If he can make a late model turn left and do it competetively....then I would take his advice and take it to heart.

There are so many contributing factors in suspension and how they work. Scott is right on when he says that if you make an adjustment to the RF coil over you have to make an adjustment to the LF coil over as well. Down 2 turns on the RF...up 2 turns on the LF. Thats a huge adjustment mind you but you get the point.

All that being said you also have to remember to compensate for dynamic actions as well. Setting static weights in the shop is great but what you do and have an understanding for what happens at the track is even better.

Someone said they run their toe at 0 so the ruts in the road dont play with the car so bad. A 1/4 in on toe would probably make it even better. Toe in makes the car alot more stable down the straights. Toe out on the other hand makes going down the straights a real pain...but corner entry is great...give a little, gain a little.

I know in kart racing we are doing now with my son...I can make a 1/4" change on tire offset and the whole turn entry of the kart

Long story short...Nobody is really wrong or right. Set your car up for fun and go from there. If you want to start circle track racing....Give Scott a call. Just dont expect him to teach you everything....lol.

Gene

[vector1]

somebody needs to make some stickies.

[Tom Kirkham]

Originally Posted by Z-linkCobra

...Someone said they run their toe at 0 so the ruts in the road dont play with the car so bad. A 1/4 in on toe would probably make it even better. Toe in makes the car alot more stable down the straights. Toe out on the other hand makes going down the straights a real pain...but corner entry is great...

1/4 inch toe is too much for one of our cars. This much toe will cause a lot of tire wear. The car will also feel bound up. You will be much happier at 1/8 inch toe in for the street.

[Z-linkCobra]

Originally Posted by Tom Kirkham

1/4 inch toe is too much for one of our cars. This much toe will cause a lot of tire wear. The car will also feel bound up. You will be much happier at 1/8 inch toe in for the street.

I could see that happening.

[Tom Kirkham]

Some things to keep in mind for those who are setting or just checking their toe settings at home.

A typical alignment settings for total toe is 1/8 inch. But the question you should be asking is: "over what distance is this taken?" This distance is known as toe span. It is very important that the included angle of the tires is correct. Obviously the further apart the toe measurement is taken for a given toe angle the larger the toe measurement becomes. So, is the toe measured at the rim? tire sidewall? tread face, or some other spot? I have seen all of the above methods used and surprisingly this number is a hard to find. Actually I have never found it. On Hunter alignment machines, and on the specs tables they give for toe, total toe is based on:
2 degrees = 1 inch.
But since most of us do not have alignment machines at home, what is the toe span used to give toe settings?

So, based on 2 degrees is equal to 1 inch.

If we draw an isosceles triangle with two equal sides, and the angle formed by the two equal sides is 2 degrees, and the base of the triangle is 1 inch, we can calculate the height of the triangle or the toe span. If we bisect the 2 degree angle we get a right triangle with one side being ½ inch forming an angle of 1 degree with the other side.

So then,
tan 1 degree = ½ in / toe span
Toe span = ½ in/ (tan 1 degree)
= 28.64 inches

Now the typical front tire is a 245/60-15
so to get the tire diameter the following formula is used:
tire diameter =(tire width mm)(1 in/25.4 mm)(aspect ratio)(2)+(rim diameter)
=(245 mm)(1 in/25.4 mm)(60/100)(2)+15in
=27.05 inches

So if your toe setting is 1/8 inch, and you are only measuring to the tread face of the tire, you are putting in too much toe. To convert to what your toe should be based on tire diameter:

tan angle = toe/toe span = new toe/ new toe span
note that 1/8 = .125
so we get
new toe setting = (spec toe)/(spec span)*(new span)
=.125 in/28.6 in*27.05 in
=.118 inches

Now if we measure to the rim
new toe setting=(.125 in/28.6 in)*15 in
=.066 inches

As you can see it is very important where you are taking the measurements. Something else to keep in mind is: the smaller the toe span the more difficult it becomes to set the toe accurately.

To further complicate measuring toe, it is normally very difficult to measure straight across the tires because things like engines and frames are in the way...So some guys just measure up to where the tape measure just touches the frame. The problem is that they have made the toe span smaller yet...

That's why toe plates were invented.
: http://www.longacreracing.com/instru....asp?instid=23

Hope this helps,

[Z-linkCobra]

Tom......really?....lol.

For the race cars we use a toe stick. 1/2 conduit with sliders on either end. those sliders have rods coming off with flat washers welded vertical to the ends of them about 12"s long (to clear any frames or headers or anything) and locking bolts. Jack the car up...spin the front tires and mark a line with white chalk at the center of the tire. Now give the front tires another good spin and mark a line in the chalk with the end of a another flat washer.

Now if you took the time to build your toe stick with measurements on the stick...cool. If not then line up the washers on the rod with the lines in the chalk you scribed earlier. Measure it and check the back...or front depending on where you started. Make sure when you put the car back on the ground after being on the jack that you settle the suspension by bouncing the car up and down a little before you try setting your toe.

The redneck way...thats also the way you do it at the track when someone runs over your s@%* and you have to replace a tie rod or they bent the frame horn and now the RF is all F*%$&@# up and your in the points lead...sorry..getting off on a rant.

Toms equations gave me a headache...lol

[Excaliber]

It was right about here that my eyes started to glaze over.

...isosceles triangle...

Actually I DO appreciate a good technical write up and this was an interesting one, thanks for taking the time Tom.

[big-boss]

Tom you are the greatest! I, an engineer as well se the truth to what you just wrote I always knew it- you actually made since of the issue, thanks. That is why all the new cool machines and BMW and all the other cool guys are simply using degrees now and actually degrees based on each side to further the complex issue.

At the end of the day it really is about the tire patch on the road right? So if your tire pressue is up or down a couple of PSI all the laser ball scratching is for not anyway right? Our poor old Cobras were never meant for this type of percision- Those guys at lemans "back in the day" were just glad the tires were not being eaten off as they used their tape measures and those kool little pipe things with welding rod inside with a little clampy thing.

I took mine to a little shop with a 100K machine gave him all the specs and it was great. I have about 6K miles on it now- but things are different I feel it - I keep the tires the same as then but it drives different. So I plan on in the next week or so to take it back and get it redon to the same specs as before. I am sure it settled in I will report back. I did screw around with corner weights at first- I got them close and gave up. I just drive on the street anyway.

[Tom Kirkham]

Originally Posted by Z-linkCobra

Tom......really?....lol.

I was trying to say: unless a toe setting includes a toe span or an implied toe span (i.e. setting the car up on an alignment machine), it is unfortunately an almost meaningless number.

Is there a problem with using toe plates?

Originally Posted by Z-linkCobra

...spin the front tires and mark a line with white chalk at the center of the tire

In other words, you are measuring to the face of the tire.

Lets do a thought experiment. Lets take the car to an alignment shop that has the latest and greatest alignment machine. It is so good, that it is perfect. Lets tell them to set the total toe at 1/8 of an inch or .125 inches. Now when they finish aligning the car you decide that you want to check and see how good this new alignment machine did. So you jack up the car and scribe the lines on the tires just as you describe. Assume for this example that the tire has a diameter of 27.04 inches. How well will the alignment machine check out to your method of measuring toe? Will you get the toe to measure .125 inches? No. I submit that you will read .118 inches of toe.

Now a completely separate argument could be made that this was close enough...

Sorry, I know doing the math can suck.

[Tom Kirkham]

Originally Posted by big-boss

...That is why all the new cool machines and BMW and all the other cool guys are simply using degrees now and actually degrees based on each side to further the complex issue.

Yes.

Originally Posted by big-boss

At the end of the day it really is about the tire patch on the road right? So if your tire pressue is up or down a couple of PSI all the laser ball scratching is for not anyway right? Our poor old Cobras were never meant for this type of percision-

Yes. Garbage in = garbage out. Yes, like most things there is a point of diminishing returns. But a poor alignment can make a sow's ear from a silk purse.

Originally Posted by big-boss

Those guys at lemans "back in the day" were just glad the tires were not being eaten off as they used their tape measures and those kool little pipe things with welding rod inside with a little clampy thing.

Actually the more I learn about the old guys the more impressed I am with them. I know they must have been taking very good measurements on their cars. At Miller Motorsports Museum they have the set up notes from the race teams when they raced the GT40s, and how each driver wanted their car set up. Over a long race a small disadvantage becomes a big disadvantage. Look at what Ford spent just on testing for the GT40 program...Accurate measurements would have been critical to maximize the results of their testing.

Originally Posted by big-boss

I took mine to a little shop with a 100K machine gave him all the specs and it was great. I have about 6K miles on it now- but things are different I feel it - I keep the tires the same as then but it drives different. So I plan on in the next week or so to take it back and get it redon to the same specs as before. I am sure it settled in I will report back. I did screw around with corner weights at first- I got them close and gave up. I just drive on the street anyway.

Yes a good machine can make aligning a car much, much faster and easier. But a lot a very fast race cars are still done with a string and a ruler. IMO the most important thing about an alignment is the person doing it. Yes, a good alignment can do wonders, especially if the old alignment wasn't very good.