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I've read paragraph 13.5B regarding shock mounting but I'm not quite sure where stock parts end and freedom begins in the case of a bayonet-stye mount (typical honda top hat configuration with washers and rubber donuts on either side and a compression sleeve in the middle). I'd like to use a washer, a non-stock sleeve with an integral washer and non-stock rubber donuts to capture the shock shaft into the stock top hat. Alternate bushings are specifically allowed so I should be able to replace the donuts (if they are indeed considered a bushing) but I'm concerned that the statement "The mounting hardware shall be of the original type" prohibits me from replacing the stock washer-sleeve-washer configuration with my alternate parts. Help?

The top hat has to remain stock.  I'm not sure about the tubular spacer between the bushing washers -- if it is the same length and wall thickness as the stock spacer, I wouldn't see a problem having it integrated with one of the washers.  If it isn't the same length, I'm not so sure.  I would be inclined to say that it's not part of the bushing, so you can't change it.

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John S.
S2000 #42as

Actually, I just reviewed the shock bushing rule, and you're allowed to replace the stock bushing with anything you want.  Any material or type, including metal spherical bearings.  So I would say that everything but the top hat is fair game, and you can do anything you like as long as the effective mounting point on the shock complies with the requirements for shock length and spring seat location.

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John S.
S2000 #42as

Orthonormal:

Actually, I just reviewed the shock bushing rule, and you're allowed to replace the stock bushing with anything you want.  Any material or type, including metal spherical bearings.  So I would say that everything but the top hat is fair game, and you can do anything you like as long as the effective mounting point on the shock complies with the requirements for shock length and spring seat location and shape.

 Added what has also been discussed regarding this rule.

This is my interpretation.   In Stock Class, Shock bushings may be changed, but not suspension bushings.

A shock bushing is integral to the shock, part of the housing.  These are the eyelet ends that bolt directly to the chassis or control arm. In most OEM shocks these eyelets are rubber lined for compliance,  in high end shocks they are spherical bearings.  And this is completely legal in stock class.

 If the bushing bolts onto the shock/strut, like the top mount of a Miata or MINI (the two cars i know anything about) they are not integral to the shock and are therefore suspension bushings and cannot be changed.

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Keith
'90 Miata with a really big roll bar
www.chaserace.com
www.tightntidyracing.com
www.vorschlag.com

Orthonormal:

Actually, I just reviewed the shock bushing rule, and you're allowed to replace the stock bushing with anything you want.  Any material or type, including metal spherical bearings.  So I would say that everything but the top hat is fair game, and you can do anything you like as long as the effective mounting point on the shock complies with the requirements for shock length and spring seat location.

Yeah, that's the way I see it. The rubber bushings are definitely a mounting point for the shock in this application and are not serving as suspension bushings. Thanks for the responses!

Keith, does the "Shock Bushings" clarification on page 246 change your view?

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John S.
S2000 #42as

Nope, doesn't change my opinion.  It doesn't really clear up anything by referring to it as a shock bushing, but not allowing the replacement.  Why else would they have to allow enlarging the hole if you could just replace them...

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Keith
'90 Miata with a really big roll bar
www.chaserace.com
www.tightntidyracing.com
www.vorschlag.com

The rule doesn't restrict the definition of shock bushing to only those which are integral to the shock.  It explicitly allows removal of pressed or bonded bushings from standard parts (in other words, stock parts from the car) to replace them, and a bushing which is bonded to a part of the car can't be integral to the shock.

The shock bushings are those which attach the ends of a shock (not a strut!) to the car.  If only those bushings which were integral to the shock were allowed to be replaced, there wouldn't need to be a rule to allow it.  Shocks are free, and that allowance would include any bushing that's integral to the shock.

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John S.
S2000 #42as

13.5 B and C conflict with each other with regards to bonded bushing material. 

If that upper bushing in a miata can be replaced via 13.5 B why did they need the clarification?

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Keith
'90 Miata with a really big roll bar
www.chaserace.com
www.tightntidyracing.com
www.vorschlag.com

The SAC is currently reviewing the contradiction -- it appears that the allowance was added to 13.5.B without removing the contradictory part of 13.5.C.  The clarification explained the effect of the new language in 13.5.B.

Contradiction or no, it still would not be necessary to draw a distinction between bushings that are bonded to stock parts and bushings that are not, if only bushings that were integral to the shock could be changed.

As for the Miata upper bushings: on the 1st generation cars it might not be legal to change the bushing, if it is not possible to do so without modifying the mounting plate.  I seem to recall that the 1st gen upper shock mount had a single molded-in piece of rubber held in place by sheet metal above and below it.  I suppose if one were to remove that rubber and pour in some urethane, that would be permissible.

The 2nd generation Miata has a more conventional 2-donuts-sandwiched-around-the-plate upper mount, and the donuts can be replaced without modifying the plate. 

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John S.
S2000 #42as