Unless a factory shaped HT must be used, a fastback setup using glass (not Lexan) is the way to go.

Care to elaborate? Just curious is all. I'm using a Treasure Coast fiberglass top with lexan.

For Gridlife street class you're required to run glass, so that's in order to comply with the rules.
The OEM HT doesn't have all that great of a shape, fastback is better.

Oh I thought there was pretty good parity between GTA and Gridlife, guess that is not the case. At GTA lexan is allowed for aftermarket hard tops since glass for them can be either expensive or non-existent in some cases.

Go figure.

Interesting... Because I spoke with Adam Jabaay (GridLife Co-founder and on-track authority) shortly after typing that post (See *DOUBLE EDIT*) and according to him the wording of the 2018 ruleset will state specifically that lexan is prohibited except in the case of an aftermarket hardtop on which it is allowed and will be permitted.
​​​​So... Good news for a Street class miata! ;)

The rules are meant to be an exact copy in order to attract GTA cars to participate in GL. Per Adam this was simply an oversight in an attempt to simplify the rules and should have been more in line with GTA in this regard.

That's great news.

Nevermind

2018 Ruleset released:

Streetmod:
TIME ATTACK RULES ? #GRIDLIFE

I wonder how should this be interpreted? The wing may be as wide as the OEM body lines and the mirrors are included in this width measurement, or the wing may only be as wide as the OEM body lines, OEM body lines is a measurement taken from one OEM mirror mounting location to the other.

I know how I want it to be interpreted...

Seems a little off to use two difference references for wing with.

My guess is that it's like that to prevent someone from putting on aftermarket mirrors that are 2 feet wider than stock.

OEM body lines will likely be interpreted as OEM mirror width.

OEM body lines is also used in reference to other aero, and in that context it sure sounds like it would not include the mirrors in the width.

I read the same seeming contradiction... sounds like a quick email to Adam might be in order.

Clarification:

Maximum wing width for StreetMod is the same as the measurement from the tip of one mirror to the tip of the other OR 5" wider than OEM body lines (Not including mirrors) whichever is greater.

All other Aero is 5" from OEM body lines.

This means that a Miata without side mirrors that measures 64" at it's widest point may have a wing that measures 74"

This means that a Miata with side mirrors that measures 76" from one mirror tip to the other may have a wing that measures 76"

This rule was introduced to accommodate commonly available off-the-shelf wings for BMWs that exceeded the 5" rule but did not exceed the side mirror width.

thanks for the clarification... that would be significantly more wing for us too.

Wing has been acquired. GTC-250. I will need to get some bigger end plates.

Attachment 229648
Attachment 229649

That's a GTC-300. 3D wing
The GT-250 is the 2D wing but yeah, moar end plate.

Isn't the 2D GT250 going to be the more preferred wing here due to less drag? Or are we just throwing MOAR POWER at this equation?

L/D ratio of the GT-250 is better than any of the APR 3D wings. The strength of a 3D wing is when you have to mount it low to the deck. In such a case, the air stream hitting the foil is moving up at the edges of the car and moving downward in the center. The mistake we see so often is taking a nice 3D wing and mounting it so high that only one section of the foil is at the correct angle with the other angled section completely stalled. If the entire air stream is hitting the foil at the same angle a 3D foil is awful.

You'll notice most OEM 3D shaped foils have a long gradual transition to AOA that is usually determined with CFD and tunnel time. Most aftermarket 3D foils have a very abrupt transition from the two angles. Problem here is that you have a small chance of having that twist transition coincide perfectly with the air stream direction change that is actually happening on your car. In practice, and aftermarket 3D foil will almost always have some portion of the foil that is contributing nothing but drag. What's worse is this stalled section messes with the flow next to it that is technically at the correct AOA for the air stream flow direction

If you are getting the idea that I think an aftermarket 3D wing is to be avoided if you are allowed to/can afford a 2D, you be right.

Ryan@Singular thinks its a GTC-200. I'm going to have to try to find a part number tomorrow to figure out exactly which wing it is. Bigger end plates are on the to buy list. The wing was $400 and at that price I couldn't pass it up. It might be slightly less then optimal, but the $1200 saved oher the singular setup will go nicely to some 15x10 6uls.