Sway bar bind / Polyurethane bushings HELP!

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ChristoMX5
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Sway bar bind / Polyurethane bushings HELP!

Post by ChristoMX5 » Wed Sep 03, 2014 7:14 pm

Hey guys, so I was just reading an article for an STS miata build and skimmed across the following:

"While sizing the bars is important, mounting them for optimal performance is critical. Particular attention must be paid to removing any tendency for bind. This is especially important when urethane frame mount bushings are used. These typically are sized too tight. In almost every off-the-shelf aftermarket application I’ve ever seen, these required some modification to facilitate smooth movement. Lubing the inside of the bushing will provide some temporary relief, but under pressure, the lube will just be forced out over a very short period of time. Once that happens, the bar will act a lot stiffer than it is or it will be erratic. It will also start to fatigue the frame attaching hardware or the frame itself. It is common to see either the saddle bracket or frame extension on a Miata cracking from improper front bar installation.

To fix this problem, there are two easy solutions. One is to grind away some of the material from the flat outside part of the D_shaped bushing. Alternatively, you can put a washer or two under the saddle mount to shim it up. I prefer the former method. Ultimately, you are looking to be able to smoothly move the bar arms up and down when the end links are disconnected."

Does this have any merit? My car is currently having all bushings converted to polyurethane and the sway bars front and rear are stock. If my mechanic installs the urethane bushings on a stock bar will I experience any of this binding? Please let me know if anyone has experience with this or can offer hands on advice. Thanks as always!

-Chris

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Fred Sullivan
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Re: Sway bar bind / Polyurethane bushings HELP!

Post by Fred Sullivan » Wed Sep 03, 2014 8:13 pm

Early miata's were prone to breaking their front sway bar mounts. If you take a good look at the way it mounts you can see how a frozen bar would tend to bend the mounts and break them after awhile.

I had a '91 miata that I put poly bushings in the A arms and would not do it again. They were a constant battle to keep from binding. Mind you this was a daily driven street car. I tried a few things to get them to work better but nothing really helped. I have access to a center less grinder at work so I ground each of the metal sleeves to a perfect fit, then I cut a helix on them on a lathe and tapped the bushings for a grease fitting... they still bound up. I was always greasing them but they would just push the grease right out. Mazda had a 40% stiffer rubber bushing available from mazdamotorsports they were more expensive but were the ultimate solution. I've heard teflon tape can help with poly but I never tried it. I switched them out before I had heard about it.

Thats my experience with them.

Freddie.

ChristoMX5
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Re: Sway bar bind / Polyurethane bushings HELP!

Post by ChristoMX5 » Wed Sep 03, 2014 9:24 pm

Interesting Fred, do you recall what brand you had before you changed them? I've installed the Flyin Miata PU kit and would have a hard time imagine these bind up the A-arms if installed properly, but I've seen enough now to believe about anything. Hopefully it isn't a problem as they are already on the car : /

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Leonard Cachola
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Re: Sway bar bind / Polyurethane bushings HELP!

Post by Leonard Cachola » Wed Sep 03, 2014 9:42 pm

Fred Sullivan wrote:Early miata's were prone to breaking their front sway bar mounts. If you take a good look at the way it mounts you can see how a frozen bar would tend to bend the mounts and break them after awhile.
I had a control arm tab mount break in the middle of an autocross run once. :( So, not just older Miatas. Heck, not even R-comps.
~Leonard Cachola
#82 CS, CSCC Solo Novice Coordinator

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Steve Lepper
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Re: Sway bar bind / Polyurethane bushings HELP!

Post by Steve Lepper » Thu Sep 04, 2014 8:45 am

Yes, installation is key, as is the quality of the bushing kit you use. Make sure you use an installer that knows what he's doing with them or you will just destroy the bushings in short order.

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Fred Sullivan
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Re: Sway bar bind / Polyurethane bushings HELP!

Post by Fred Sullivan » Thu Sep 04, 2014 11:28 am

The poly bushings I got came from mazda motorsports. It was branded by them I beleive but it was just a kit they got from one of the big name poly bushing makers. I don't want to bad mouth a company on a web forum, if you want the company's name pm me. I tried really hard to make them work. They used a bushing that pressed in from each side. In addition to the things I mentioned in my earlier post, i even fabed up a reamer to make sure the holes were concentric.
Steve is a smarter guy then me about this, I sure he has some tricks to make them work.

Something to remember, the miata alignment adjusters rely on compliance from the bushings. Toe in the rear and caster up front puts twist in the bushing. I'm not sure how you addres that with poly. Some kind of spherical bearing seems like the solution there but is it practical?

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