Explain to Me the Purpose of Alignment Turn Plates, Please.

So, after taking Chuppy to the most recommended alignment guy in Tulsa, I came away swearing I would never let anyone else do my alignment again. Apart from this fella's bitching and moaning about "hot rod" parts, he used nothing but home made tools. Which is perfectly fine because despite his complaining and home made tools, he did a terrific job.

I understand the tools needed for camber, caster, and toe. What I am unsure of is the purpose of the turn plates. Obviously, they allow the wheels to rotate and therefore you can catch any binding of the steering. However, I noticed they can move laterally--they're a plate on top of a bunch of ball bearings so they can move freely in any direction.

Could the GRM gurus enlighten me as to the purpose and proper use of alignment turn plates?

Thanks JP

The turn plates allow the wheels to settle into the position they want to be in, avoiding any pre-load of the tires, suspension bushings, etc. Otherwise, unless you roll the car forward or backwards after every change, turning the steering, etc. you'll have binding that can throw your readings off depending on how much things can flex.

Next time you jack up the front end of your car, set it down and look at the tires. Roll it a foot, and look again. In most cases, you will lose a degree or two of camber in that foot of movement. The plates allow everything to settle into place properly.

And hot rod parts are generally stupid and sucky, and designed to compensate for something stupid that's been done to the car.

Exactly. When the suspension moves, the contact patch will move fore-aft and side-side. This is either the byproduct of suspension geometry or the purpose of it, depending on your point of view.

I have never worked on an alignment rack where that stuff actually worked, it was always siezed. Putting the tire on a newspaper works amazingly well as a makeshift turnplate.

And hot rod parts are almost universally garbage. Good modifications use OE parts. I've seen some scarily bad designs sold as high end components, like polyurethane bushings with no inner sleeve to tighten against. (Solution? Use Nylocs. And all that suspension slop as the bushing rattles around is performance slop, I guess)

I actually have a set of plates. They do make an alignment much easier because the contact patch can move wherever it needs without trying to twist or slide the tire.

Mine were headed to the scrap yard when I saved them. I think I gave the guy $5 for them.

I'm glad you posted this. I needed to remember to take them to work in the morning.

I have a pair of plates I don't use anymore.

They weigh a ton.

Free to anyone who wants to come get them.

Before long they will be going for scrap.

Okay guys--he was cranky. I don't have hot rod parts. I have adjustable control arms, tension rods, tie rods, and adjustable four links out back. It's all very well made. The guy was just initially pissed that there was so much to adjust. After a little bit he calmed down and began complimenting the design. Trust me, it all works very well.

So, to make my own turn plates I would need a sort of shallow boxed lower portion filled with bearings and a flat steel plate on top with some pins to hold it in place?

https://www.youtube.com/embed/7aEDZXThDek

Probably not as slick as the ball bearing and steel plate, but very cool none the less.

A couple of garbage bags with wheel bearing grease in them work pretty well for home brewed alignment plates.

This is why we have ball transfers on the bottom of our hub stands. Having that true freedom of movement of the bottom of the wheel makes a big difference.

Not sure what the shop had for measuring alignment angles but most systems require steering to be moved a required number of degrees in both directions to measure caster and steering axis/McPherson strut inclination. The radius plates are very important for the above mentioned settling and not binding the suspension in order to get correct readings and adjustments. The plates should be kept clean and maintained so they will move freely with vehicle weight on them. Other wise you are wasting time and money. As mention above, there are other ways to accomplish this w/out the plates

Would this, by chance, have been Greg at ACME? If so, it's worth hearing is griping, he really is that good. And as for his "interesting" tools, the man can set the toe you specify to + or - 1/32 inch, every - single - time. And camber to + or - 0.1 degree.

Cheap easy to use turn plates are as close to you at any kitchen store! They all sell cheap Teflon cutting sheets the ultra thin ones. Get the CHEAP ones with out the anti-slip on one side. Normally come in a 4 pack of different colors stack two in front of the wheel roll car on to them. $4 well spent. No oil or grease is needed. Wheel offset can change the "Scrub Radius" which is what make the slide to side movement. Ever seen a pick up with really stupid high offset rims? Ever seen them turn the wheel in a parking lot the whole front end hops over inches, this is do to scrub. Turn plate really help with setting Ackerman where due to geometry the inside wheel turns more then the outside wheel. as the tie rod angles on the inside wheel flatten with the turn and the out side wheel tie rod gain angle as it scribes an arc. you can check Ackerman with a level / straight edge on the tire side wall go out distance "x" mark floor then another 10 inches and mark "y" turn wheel to full lock re-due straight edge and mark then due the math to find the angle.

"Hot rod parts" is a very broad term.

An old Grassroots Motorsports magazine under each tire works pretty well, too.

I do really nice string alignments at home in my shop space. I finally upgraded to a set of longacre turnplates and digital camber/caster gauge, but I still use the strings for toe. The right tools really help make the job faster and much more repeatable. Another nice benefit of good turn plates is you can turn the wheels a specific number of degrees. This is extremely useful when using a caster gauge but is NOT necessary if you're calculating caster by hand with the caster formula (I used to do this and it sucked). I'm in the Tulsa area BTW, so I could probably check it out for you. I also have a set of corner weight scales and roll off levelers, and know how to use them.

As knurled sort of mentions, bushing slop is the bane of my existence when I'm trying to do alignments. The goal is to eliminate as much friction as possible between the tire and whatever it is sitting on. I sometimes use pieces of linoleum tile with grease between them or I'll use two sheets of heavy black trash bags to get things moving right. It's super frustrating when you turn an adjuster and nothing happens because the bushings deflect instead of the wheel.

I use 2 pieces of flat steel with oil between. Works real well.

Man, I would love to own a set of real turn plates.

But what I use instead is the cheapest institutional linoleum floor tiles I can find. Sandwich two with some lube in the middle. If you didn't park on a level surface (hard to do a good alignment otherwise,) you will find out in a few minutes!

I've always used the guy at Dino's up on Admiral (aligned my track Miata more than once) and the Cecils on west side of the river in Jenks (Cecils Tire, NOT Cecil and Sons).

Dang, how many of you guys are in Tulsa?

I'd love to have the Longacre plates but at $700--I can't justify the cost. I've been looking at these though:

https://www.amazon.com/gp/product/B00J7E7B3E/ref=ox_sc_sfl_title_10?ie=UTF8&psc=1&smid=A3RW7WXKNSRMU9

I understand there are wonderful homemade solutions but I like permanent tools.

I've also been looking at camber/caster gauges. These in particular:

https://www.amazon.com/gp/product/B000PG6OW2/ref=ox_sc_sfl_title_8?ie=UTF8&psc=1&smid=A2UUWCCR4G5EFA

You'll have to copy and paste fellas--it won't allow hotlinking for some reason.

redvalkyrie wrote: Dang, how many of you guys are in Tulsa?

Haha, not exactly sure!

Off-topic here--but it seems maybe we should acquaint ourselves sometime.

Tulsa meet! Shoot me a PM. I'm usually available when I'm at work or helping a buddy of mine wrench on his car.

redvalkyrie wrote: Off-topic here--but it seems maybe we should acquaint ourselves sometime.

I'm in! I just PMd Z31maniac.