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Legal bushings? Delrin Vs. Urethane? Zerk?

Last post 10-11-2008, 9:21 PM by GChambers. 10 replies.
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  •  07-05-2008, 12:48 PM 308639

    • G. Jay is online. Last active: 11-22-2008, 10:40 AM G. Jay
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    • Forest Lake Minnesota
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    Legal bushings? Delrin Vs. Urethane? Zerk?

    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.


    1991 Miata STS2
    Recovering former member of the pushrod posse
  •  07-05-2008, 1:46 PM 308643 in reply to 308639

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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.


    Aut tace aut loquere meliora silentio.
  •  08-01-2008, 7:19 PM 313432 in reply to 308643

    • G. Jay is online. Last active: 11-22-2008, 10:40 AM G. Jay
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    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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.
    1991 Miata STS2
    Recovering former member of the pushrod posse
  •  08-01-2008, 7:38 PM 313433 in reply to 313432

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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.


    Aut tace aut loquere meliora silentio.
  •  08-01-2008, 7:51 PM 313436 in reply to 313432

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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
     


    --CRX Addict
    --Recovered Mini Addict
  •  08-01-2008, 9:46 PM 313442 in reply to 313433

    • G. Jay is online. Last active: 11-22-2008, 10:40 AM G. Jay
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    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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.


    1991 Miata STS2
    Recovering former member of the pushrod posse
  •  08-01-2008, 10:59 PM 313446 in reply to 313442

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    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.


    Aut tace aut loquere meliora silentio.
  •  10-10-2008, 2:38 AM 326287 in reply to 308639

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    G. Jay:

    Can I put on a zerk legally?

     

     I'm interested to hear peoples opinion on this one.  Here are the rules which may allow it, or may not depending on how you look at it:

    14.8.B. Suspension bushings may be replaced with bushings of any materials (except metal) as long as they fit in the original location.  Offset bushings may be used. In a replacement bushing the amount of metal relative to the amount of non-metallic material may not be increased. This does not authorize a change in type of bushing (for example ball and socket replacing a cylindrical bushing), or use of a bushing with an angled hole whose direction differs from that of the original bushing. If the Stock bushing accommodated multi-axis motion via compliance of the component material(s), the replacement bushing may not be changed to accommodate such motion via a change in bushing type, for example to a spherical bearing or similar component involving internal moving parts. Pins or keys may be used to prevent the rotation of alternate bushings, but may serve no other purpose than that of retaining the bushing in the desired position.

    14.8.I. Camber kits, also known as camber compensators, may be installed. These kits consist of either adjustable length arms or arm mounts that provide a lateral adjustment to the effective length of a control arm. Alignment outside the factory specifications is allowed. The following restrictions apply:
    1. On double/unequal arm (e.g. wishbone, multi-link) suspensions, only the upper arms OR lower arms may be modified or replaced, but not both. Non-integral longitudinal arms that primarily control fore/aft wheel movement (e.g. trailing arm(s) or link(s) of a multi-link suspension) may not be replaced, changed, or modified.

     


    Schooner
    95 Miata STS2
  •  10-10-2008, 9:09 AM 326300 in reply to 326287

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    Zerks? 

    Seems like it would be a pretty weenie thing to protest, given that the zerk would be expected to provide a bushing location function.  But since you aren't going to have to lube these things all that frequently the whole issue gets side-stepped if you pull the zerks after doing the lube and replace them with screw-in plugs of the same thread.  I think this has even been done at the OE level at various times (though in that case for improved resistance to contamination).

    On edit, I don't think that I've ever seen bonded polyurethane bushings.  Nor am I seeing what possible benefit there might be, given that the usual poly pieces fit tightly enough in the outer sleeves to not rotate at that surface and that rotation is specifically intended to occur at the inner sleeve surface (duh).

    Norm


    seat time is where you find it (semi-retired) weenie CP '79 Malibu, (no longer ST/SP legal) '95 626
  •  10-10-2008, 9:31 AM 326308 in reply to 326300

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    Norm Peterson:

    On edit, I don't think that I've ever seen bonded polyurethane bushings.  Nor am I seeing what possible benefit there might be, given that the usual poly pieces fit tightly enough in the outer sleeves to not rotate at that surface and that rotation is specifically intended to occur at the inner sleeve surface (duh).

    Norm

    I can't remember the manufacturer, maybe Powerflex? Make bonded urethane bushings. Bonded bushings have the urethane bonded to the center metal sleeve - not the suspension arm - just like OEM bushings. They're maintenance free, but are nearly as soft as the Mazdaspeed bushings for Miatas.   


    Aut tace aut loquere meliora silentio.
  •  10-11-2008, 9:21 PM 326558 in reply to 326308

    Re: Legal bushings? Delrin Vs. Urethane? Zerk?

    I have grease fittings on all of my bushings. They have no other function than to allow me to easily grease my bushings. They don't even hold the bushings in place to keep from spinning. If that isn't a convenience item, nothing is.
    90 Miata/89 CRX - STS2 #90/190
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