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I am welding a new lower A-arm and was wondering if anyone with miata spindles could get me in the ball park wth regard length and offset. MY A-rms were designed for strut style uprights. I have 3 deg neg caster and 10 deg neg camber. I can get it to 3 deg neg camber but that puts the upper ball joint (3" of threaded body at 17mm thread) out way too far. I think I need to bring the lower in about 1" to get to 0, then use the ball joint to get to the desired neg 3. deg.

Upper A-Arm. Center (bolt on chassis) to Center of upper ball joint or rod end on spindle. Mine is 11.825"

Upper A-Arm offset. How far behind center line is the upper ball joint. Mine is .5".

Lower A-Arm. Center (bolt on chassis) to Center of through bolt on lower ball joint. Mine is currently 16".

Lower A-Arm offset. How far forward from center is the center hole 12mm on the ball joint. Mine is currently centered.

Thanks for your time.

I'm currently designing some A arms for the miata spindles and a book chassis. I have built a "string computer" (as described in the "Stanforth" book) to help properly locate my roll center. I can probably have those measurements for you this weekend but I need to know what size chassis you have. Also, if you aren't using a Miata rear end I need to know the rear track measurement.

Where are your suspension pickups on your chassis? I assume the lowers are in the "book" location, how high up are the upper arm mounts? Their location is what determines your swing arm length and roll center. Your lower arms are simpler to design since they just need to be parallel to the ground.

If you want to figure this out yourself (which is probably best) just put the car on jackstands and put a jack under your front tire. Unbolt your coilover and swing it out of the way and then unbolt your lower a arm from the car. (but not the upright) Put a jackstand or something under the arm (to hold it up in place) and slowly jack up the tire until the car is at "ride height" relative to the tire you are jacking, whatever that is for your car. You should then be able to first verify that the tire on the jack is in a vertical position and then have someone hold it there while you lift the lower A arm back into place. Remember it should be parallel to the ground, when you verify that everything is propery aligned you can measure and see how much length you lack from being able to bolt it up. Add that length to your new lower arm and you should be in business.

Also while you have it positioned there you may want to measure from the centerline of your chassis to the outside edge of the tire, double that measurement and make sure it is close to the rear end track measurement. (outside of tire to outside of other tire) If they are off by much you may want to re-fab the upper arm.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

OK, according to my "plans" there is 15 7/8 inches from the center of that vertical hole (closest to the chassis) on that iron piece that locates the ball joint to the pivot on the chassis. Hope that helps.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

I think my original thread a bit confusing. I should have asked; does anyone have the dimensions of the sierra spindles with the strut tube adapters? I need to know that the difference is between the center holes so I can shorten my lower A-arms. This will be OBE by tomorrow as I am mocking it up using clamps to hold the lower mount in place and then measure both camber and caster.

I was concerned about caster because of the CMC miata kit's A-arm design. I thought the straight tube mounted that way, but it looks to angle forward quite a bit. I still have about 1/8" of shims that can be removed if I need more caster.

I have the Mk Indy front suspension trimmed equally at the pick-up points to fit inside the stock "Book" CMC chassis. I think there are some photos on the locost usa yahoo group in the two bonjo folders. My issue is that I want to retain the basic MK Indy geometry, just bring the lower ball joint in to accomodate the difference in length of the strut style spindle the suspension was designed for, in effect reducing both A-Arms length proportionatly.

The rear live axle is another story all together. The shocks will be moved, but I am not yet sure if I will abandon the short 4 link in favor of a 3 link. My initial impression of the 4-link is that it will be an oversteering monster with possible binding.

I'll see if I can find the original cad drawing of my front suspension. with the 500ld springs and level ride my roll center is at the ground. When it was sagging with stock springs the roll center was much higher and all jacked up.[/img]

I was surprised when I did the fitting how much will need to come off the Lower A-Arm, and how the taller angled ball joint affects other stuff. So what I thought would take 30 minutes took two hours.

Now.. Stock tie rod ends will fit, but will need to shim the rack. Front ride height drops .5" Will have between 2 deg positive and 6 degrees neg camber range. The lower a-arm remains level, but the upper now shows an upward tendancy much like the photos in "the book."

If anyone wants some maxi lower ball joints with poli dust covers drop me a line.

I'm glad you got it sorted out. Post a pic if you get a chance.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

http://www.freewebs.com/bonjo2/locostphotos.htm

Sorry it took so long. Welds are substantial and not ground pretty yet. I recently removed the powder coat with gasket remover and will be painting them with statin black enamel with a clear or black vinyl strip accross leading edge.