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Can anyone tell me how to be sure that aftermarket suspension bushings meet the rule about no more metal that stock?  Is there a list of options for an NA Miata that anyone knows about or does anyone know the dimensions I need to look for?

 I understand that these plastic bushings may squeek.  Can I put on a zerk legally?

 I'm also wondering about the advantages of Delrin.  Urethane seems to be a lot cheaper.  Here's ones I'm looking at.

http://www.949racing.com/index.asp?PageAction=VIEWPROD&ProdID=107

 All advice is appreciated.

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1991 Miata STS2
Recovering former member of the pushrod posse

If you take a Miata bushing apart, you'll find that the normally visible metal parts give the impression that there is minimal metal in the bushing. In fact, there is a huge knot of metal in the middle. It would be very unlikely that aftermarket bushings would have an equal or greater amount of metal.

As far as Urethane vs Delrin, I'd avoid non-bonded urethane. In order of performance I'd use stock OEM Mazda bushings, Mazdaspeed stiffer bonded rubber bushings, bonded urethane bushings, then delrin. Non bonded urethane bushings have all the disadvantages of delrin, but miss some of the advantages. The only advantage that non-bonded urethane has is cost, and the difference in cost will be quickly forgotten after they become a PITA to maintain.

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Aut tace aut loquere meliora silentio.

Any idea how much time delrin is worth compared to OE Miata bushings?  Can anyone estimate a time reduction on a 60 second run?  It is a lot of effort and cost but it seems to be universal on the well prepared cars.

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1991 Miata STS2
Recovering former member of the pushrod posse

G. Jay:

Any idea how much time delrin is worth compared to OE Miata bushings?  Can anyone estimate a time reduction on a 60 second run?  It is a lot of effort and cost but it seems to be universal on the well prepared cars.

Rubber bushings would have negated the accuracy of my gold-plated shocks, which gained me between 2-3 seconds per run over revalved Koni Sports. 

I went from rubber bushings and stock springs and shocks to poly bushings with Koni Sports and 500-350 springs to delrin bushings and Koni 2812s with 700-450 springs. Each step was a 2-3 second gain. But then I'm a sucky driver that depends on his car to do all the work.

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Aut tace aut loquere meliora silentio.

G. Jay:

Any idea how much time delrin is worth compared to OE Miata bushings?  Can anyone estimate a time reduction on a 60 second run?  It is a lot of effort and cost but it seems to be universal on the well prepared cars.

 

Bushings by themselves are not going to make you go faster. They help you drive better, and how much better you drive is entirely up to you. If you can drive a floppy, unstable car well then they won't help much. If your scared of your car because it won't drive in a straight line then you will probably go a good bit faster.

Ian
 

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--CRX Addict
--Recovered Mini Addict

modernbeat:

....poly bushings with [revalved] Koni Sports and 500-350 springs to delrin bushings and Koni 2812s with 700-450 springs. Each step was a 2-3 second gain.

 

Holy carp, is this possible?  I've got Koni Sports with OTC valving and I'm looking for 2-3 seconds.  I was thinking about getting the fronts re-valved and moving up from my 450 springs.  Does this really leave me so far off the pace still?

 Seems like there is a range of opinions here.

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1991 Miata STS2
Recovering former member of the pushrod posse

G. Jay:

modernbeat:

....poly bushings with [revalved] Koni Sports and 500-350 springs to delrin bushings and Koni 2812s with 700-450 springs. Each step was a 2-3 second gain.

 

Holy carp, is this possible?  I've got Koni Sports with OTC valving and I'm looking for 2-3 seconds.  I was thinking about getting the fronts re-valved and moving up from my 450 springs.  Does this really leave me so far off the pace still?

 Seems like there is a range of opinions here.

Well, I also added a sway bar and upgraded from 15x6 to 15x7 wheels. Tires were Azenis RT215s on both. Everything was incremental except changing to better tires and going with 2812s. The REO1r was better than the RT615, which was better than the RT215.

The advantages of the bushings were the ability to have a fairly static spring rate, and have a static alignment. The spring rate bit is what allowed the shocks to do their work right.

If your car is a daily driver, I'd skip delrin bushings. Too much maintainence. If your car is an occasional driver, or a competition car, I'd do it.

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Aut tace aut loquere meliora silentio.