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PostPosted: Thu Jan 11, 2018 6:52 am 
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OK, doodling in CAD and had a thought. And yes I know I could just call a few people and get hubs, but I have a machine shop handy and like making stuff.

Reasoning first - for the 1st gen RX-7 in EProd, on the spec line, you're allowed to replace the front hubs, provided they weigh more than a given weight - I'm pretty sure you have to use the stock bearings due to restrictions on modifying the bearing carrier, but it doesn't specify any other rules describing the allowed alternate hubs. In the main body of the rules, 9.1.5.E.2.o.5, it says that hubs are unrestricted, though I'm reading this to only apply to rear hubs because it's in the final drive section. And 9.1.5.E.8.a has wheels unrestricted.

What I'd like to do is convert to 4x100, essentially because then there's a whole bunch of 15x7 off the shelf good wheels for a lot less than custom pieces from Jongbloed or whoever. It seems like it's definitely legal on the back of the car, but the aftermarket front hubs allowed in the spec line aren't nearly as well defined.


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PostPosted: Thu Jan 11, 2018 7:52 am 
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Can that be covered on the allowance to convert between GS and GSL-SE parts? but I'm not sure you can mix/match the 4x100 bolt pattern and GSL-SE hubs...

then again, I don't have a problem with it- seems prudent change to me. various trims of the car came with them, and even my rear axles are drilled with both bolt patterns. (surely because they were originally 4x100 and re-drilled to 4x114)

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Matt Blehm
Houston Region
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PostPosted: Thu Jan 11, 2018 8:10 am 
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A bit of clarification - I'm speaking of wanting to move to 4x100 (Honda/Miata bolt pattern never used on an RX-7) not 4x110 (GS/GSL) or 4x114.3 (GSL-SE) Scott Peterson's STU build got me thinking about it, and you and Jesse chatting on the "wanted" thread got me thinking about it a bit harder.


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PostPosted: Thu Jan 11, 2018 8:25 am 
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whoops- I thought the other RX7 pattern was 4x100, not 4x110

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Matt Blehm
Houston Region
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PostPosted: Thu Jan 11, 2018 8:50 am 
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OK, there of course isn't a specific rule allowing bolt pattern changes. So, you have to look elsewhere.

Wheels are unrestricted (9.1.5.8.a), so wheels with a different bolt pattern would certainly be legal.

Drive wheel hubs and bearing carriers are also unrestricted (9.1.5.?.0.5), so, it's legal on the rear of the RX7 to change to whatever fits.

Which leads me to the front (non-driven) hubs...

9.1.5.3.a.5 says "Suspension bushings, bearings and ball joints are unrestricted." If a spindle bearing is a suspension bearing, and it is really unrestricted, then a bearing with a different set of studs or holes is certainly legal.

Sure does seem legal to me, although somewhat convoluted to get there.

YMMV - and be prepared to get tossed and have to appeal this one.

Or, write a letter, or call our new tech manager, the famed/fast Rick Harris.


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PostPosted: Thu Jan 11, 2018 9:04 am 
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Yeah, I guess I was trying for a sanity check before I took it further. I have some time to do this build the way I want, and I figure anything unusual I do I damn well want to know it's legal.


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PostPosted: Thu Jan 11, 2018 9:41 am 
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Another definitely legal alternative, is to buy "normal" street-offset wheels (like say 40mm) and then buy 1" spacers that alter the bolt pattern.

That would certainly be legal. Many folks run spacers (myself included) but mine are all bolt-through, so I'm sure the stress loads would be somewhat different.


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PostPosted: Thu Jan 11, 2018 10:43 am 
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That's definitely Plan B. I just look at it as, I'm allowed to have non-production front hubs on the spec line, I'm allowed to have wheel spacers that do the same thing I want to do, but why shouldn't I be allowed to just design the hub to do that?

Anyway, thanks all for confirming I'm not crazy.


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PostPosted: Thu Jan 11, 2018 2:04 pm 
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Joined: Sun Jan 23, 2011 4:54 am
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Dan DeRosia wrote:
but why shouldn't I be allowed to just design the hub to do that?


Unfortunately, I have yet to see SCCA work that way.. it seems that most things like this, SCCA requires the hardest, most expensive workaround for something that should be stupid simple like a bolt pattern...

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Matt Blehm
Houston Region
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PostPosted: Thu Jan 11, 2018 7:25 pm 
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Joined: Thu Mar 27, 2003 7:43 am
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Location: Pueblo West, CO
Does changing the bolt circle provide a competitive advantage?
I can't see where it could.
What it does is make racing more affordable.
My Fiat had 4 on 98 but I could find that if not I would have redrilled to 4 on 100 and not worried about it.

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