GRM Exclusive Reveal: Exocet Spec-A

The numbers we're running will have a fairly substantial effect on the effective wheel rate, but I don't think it'll affect the roll centers. Those are all based on the pivot points, and those haven't changed. The scrub radius will change, but that's not going to be a big problem as we have power steering and a relatively light front end.

The important thing is that this is what you have to do in order to put rubber on these cars. So any theoretical molestation of the purity of the Miata's scrub radius is rather moot.

The wider track is a benefit. Less weight transfer.

The instant centers won't change, but the roll centers should take the contact patch into account. All other things being equal, going wider will nudge the roll center up slightly. This isn't a bad thing, as it means more uncoupled roll stiffness. It's just good to know if you're chasing the last hundredth of a g in steady-state cornering.

Kevin is at SEMA, and Warren is in ATL shipping bodywork.?.?.?

In reply to SteadFast:

I'll be at Fab-Tech in Atlanta every day of the show with XP-4 and XP-5.

What about hub and bearing load / life? +36 (15X8 6UL) to -20 is a pretty huge swing in the moment about the outer bearing. I don't have parts in front of me, nor have I ever had to take mine apart, but it looks like the hub face is overhung about 20mm from the outer bearing. So the center of the contact patch goes from being within the bearing duplex by ~16mm to being overhung by ~40+mm. Quick back of napkin says this is 4-5X load seen by the outer bearing, and >2X for the inner. I can refine if someone can measure bearing and hub spacing.

If the alternative is to not have tires, it's a good solution. The frame design puts some real constraints on what we can do.

Meierznutz wrote:

mrvwcastner wrote: Changing resistor in relay fixed hiperflashp my gremlin still exists does anyone have good diagram of lighting for blinkers & tails?

What harness are you using? From my experiences, most intermittent electrical issues are from a bad ground, a loose connector, or a chaffed wire.

My car is a 1990. I really think its in the relay, or something else. Maybe even inside lights. Still a mystery as everything rings out. Adding an additional ground and trying another relay this weekend.

Keith Tanner wrote: If the alternative is to not have tires, it's a good solution. The frame design puts some real constraints on what we can do.

Agreed, not sure what else you would do. Seems like a significant design compromise if you:

1 - Can't use the Miata wheels you already have, or one of many inexpensive options in the aftermarket

2 - Have to run huge spacers (not a fan)

3 - Use custom wheels and/or spacers, and suffer bearing longevity

The rollbar fixation was a big step up relative to the British design, no doubt. I guess the alternative would have been to move the rollbar forward and give up a couple inches of legroom? Or a compound bend in the main spars? Didn't the British design use spacers due to the fender stay packaging?

MattGent wrote: Agreed, not sure what else you would do. Seems like a significant design compromise if you: 1 - Can't use the Miata wheels you already have, or one of many inexpensive options in the aftermarket 2 - Have to run huge spacers (not a fan) 3 - Use custom wheels and/or spacers, and suffer bearing longevity The rollbar fixation was a big step up relative to the British design, no doubt. I guess the alternative would have been to move the rollbar forward and give up a couple inches of legroom? Or a compound bend in the main spars? Didn't the British design use spacers due to the fender stay packaging?

I don't think that the wheel packaging is that big of a deal. Keep in mind Flyin Miata is running 15x9" wheels with larger than normal tires on that LSX car. A 15x9 -26et is the same positioning of the inner lip (the interference point) as a 15x8 +0. For 99% of us, a 15x8 will be plenty of wheel/tire for this car and there's dozens of options in the 15x8 +0 that are reasonably priced.

Unless you NEED a 15x9, I don't see the problem. Sure, you put a bit more load on the bearings, but I doubt it's enough to be a serious problem. The only other negatives are the slightly affected scrub radius, but that's negligible and offset by steering feel IMO.

MattGent wrote:

Keith Tanner wrote: If the alternative is to not have tires, it's a good solution. The frame design puts some real constraints on what we can do.

Agreed, not sure what else you would do. Seems like a significant design compromise Or a compound bend in the main spars?

I guess forming a tire clearance kink in the tubes is too difficult.

Kinky chicks in bars = good

Kinky bars in rollcage = not good

I think there's a little bit of misunderstanding here. When you go up in wheel width by 4" or so, you're changing a lot of variables. It's impossible for a car like this to allow straight bolt-ons of every combination of aftermarket components; sometimes you'll have to be a little creative to get what you want.

Stock wheels and tires work, you just might need a small spacer in some instances. The UK guys indeed use huge spacers, even for 7" wheels. As far as I can tell, the original Exocet was designed for 1.6 OEM wheels. The rear clearance requirements on the US frame are due to an emphasis on cockpit width and rollbar integration. I fit much better in the US Exocet, even as it sits right now.

Keep in mind, guys, a 15x9 wheel won't work in a stock Miata without changing to narrower coilovers and rolling fenders in an NA. 9" is a lot more than the 5.5-6.5" wheels that came on the Miata. Keeping under a minimum backspacing is a lot less work to getting the same rubber under a Miata.

icaneat50eggs wrote: Kinky chicks in bars = good Kinky bars in rollcage = not good

I am so stealing this quote!

BTD wrote: For 99% of us, a 15x8 will be plenty of wheel/tire for this car and there's dozens of options in the 15x8 +0 that are reasonably priced.

Would you mind listing a few you know about - other than the traklite holeshot? Thanks in advance.

Cost is an object

or if cost is no object

BTW, we found that a +30 15x7 with a 225/45-15 (which fits on every Miata without modification, IIRC) will rub on the Exocet frame badly. That's not taking the fender mounts into consideration. We may have rubbed a 205 on the same wheel, I forget. There's only about 10mm difference in clearance.

We had to go further out on the offset on those particular 15x9s because of brake clearance. I suspect we could have pulled them a bit further in. A 15x9 -26 is the same as a 15x8 -13 or so, it has more clearance than a 15x8 +0. Remember, the offset is measured from the center of the wheel so adding 25mm (1") overall to the wheel width will only change the offset by 12.5mm, assuming no other changes.

linuxd00d wrote:

BTD wrote: For 99% of us, a 15x8 will be plenty of wheel/tire for this car and there's dozens of options in the 15x8 +0 that are reasonably priced.

Would you mind listing a few you know about - other than the traklite holeshot? Thanks in advance.

Traklite, as mentioned makes the Holeshot in 15x8 +0 or the Octane in a 15x8 +15 so only a small spacer is needed

XXR Makes a number of models in 15x8 +0, including the 002, 002.5, 536, 537, 538, 531, and 532. They also make the 530, 527, and 550 in 15x8.25 +0 as well as the 501 in 15x8 +15.

Avid.1 makes a number of wheels in 15x8 +15

Rota used to make the Grid V and Zero Plus in 15x8 +0, not sure if they still do.

Konig makes the Wideopen in 15x8 +20, which is what I will be running with a small spacer to clear unless I decide to sell them for some +0 wheels.

I've had good luck with XXR, Rota, and my Konigs. Everything here is under $600/set, most under $500. If you up the budget significantly, SSR, Work, and Volk all make wheels in 15x8 +0 that would work, but are ~$500/wheel. I'd say that's a pretty wide range of options all requiring ~0.5" spacer or less.

Warren v wrote: In reply to SteadFast: I'll be at Fab-Tech in Atlanta every day of the show with XP-4 and XP-5.

I am going to be manning my company's booth at Fabtech on Wednesday/Thursday. I'll definitely have to stop by and visit.

Lets talk coolant re-routing for a minute. There's this kit:

http://trackspeedengineering.com/product_info.php/cPath/53/products_id/112/osCsid/ruo3ajk0lhh6cie17iakemd654

While I'm sure it works well, I was wondering if there was some sort of variation that completely eliminated all the coolant hoses from the outside of the engine save the radiator hoses.

Like a block off plate for the whole thermostat housing plus a new bolt on plate for the water pump & rear head that eliminated all extra coolant nipples.

For the oil cooler, I can't just go to an air unit and I don't see why the throttle body lines can't be eliminated.

Some of those hoses ensure water flow through the engine while the thermostat is closed. You can pull the thermostat neck and insert a freeze plug in the hole if you want a cleaner option.

I forget exactly what the lines to the throttle body do right now, I think it's part of the cold running mechanism. Once the coolant gets up to a certain temp, there's a physical change in the throttle body.

What's your actual goal? Do you want to be like a VW with no visible wires or hoses or air filters?

They open/shut a passageway around the throttle plate for a higher cold idle. Something the idle control motor can do alone.

So you're suggesting leaving the hard line that routes under the exhaust manifold? Guess you could say I'm going for the clean/simple VW look.

I would need to somehow cap the extra nipple on the water pump housing and the elbow on the back of the head.

I just realized I need two nipples for coolant lines for the turbo.

Edit: okay I think I know how I can do this.

The M-Tuned rear head water housing has ports for both the heater core and an extra line for the turbo. The heater core hard line that runs under the exhaust manifold can be routed to this new housing for coolant flow when the thermostat is closed.

The extra nipple (hopefully it points towards the divers side) can route to the turbo and the nipple on the water pump can be the feed line for the turbo.

I can block off the front housing per Keith's directions.

One last question for you Keith. Your FM oil cooler kit, does that replace the coolant housing that the oil filter threads onto or is it just a sandwich plate? I'm talking about the piece that you thread the braided feed/return lines and the oil filter itself.

Yes, keep the hard line. I would be careful not to compromise the car's cooling for the sake of aesthetics.

Have a look at how the MSM turbo water is plumbed, you might be able to take some tips.

Our oil cooler kit uses a sandwich thermostat that goes between the factory oil cooler and the filter. The factory part is needed as a spacer, otherwise the oil lines foul the block. You can disconnect the water lines to the part, or we can supply a billet spacer. Btw, that's more of a hear exchanger to speed up oil heating than a cooler.

Thank you Keith.

Friday bodywork update?