i think it’s time I invest in a good pair of reading glasses. Ha! My car came with a 14” spare,

The skinny race tire offerings are super light. The spare wheel would have to be awful heavy to make a skinny tire and spare combo heavier than a factory 14” wheel and tire.

Who can can weigh a 15” spare and report back?

Let me see if the spare is still in the tire well of my nb2. I might be able to weigh it if so.

Both of my spares, both from nb1s, are stamped 14 on the tire.

at this point, im not sure if they are na or nb spares....

That's interesting. My comments were based on my perception that NB1 compact spares were 15's, same as Andrew.

However, I just looked at mine and the indication is that it is 14 x 4.

this NB2 is 15x4

My NB2 spare is a 15. Could be dependent on whether the car had sport brakes or not, so all 03+ spares should be 15x4s, but some 01-02s might not be

That's what I'm thinking. Sport brakes.

Front Skinnies: If I end up ponying up the $$ for biased ply skinnies:

How much would it matter between the M&H 3.6/24-15 vs 3.5/22-15?

Pros and cons, assuming no special suspension tuning.

Go with the 22’s, lighter and fit better

This!

It’s plenty safe, looks right, and faster.

That’s what I thought. ebay has a set of used Bogarts with the 24’s.

Im thinking these 24.5" tall on a 15x8 6ul for my rears.

I think it will be a close fit. Don't wrinkle walls "grow" by the end of the quarter mile? It says tire diameter range: 24-24.99 inches

Attachment 218872

That's a little tall, to my understanding.

Well crap. If I went with a 23" tall then I think I'd want 13's to get some more sidewall

You can try them, but unless you are making serious power, you will go faster with less tire. A 24.5” will fit though.

Mickey Thompson’s don’t grow much. Some tires are built to grow as you get down the track. These days, most drag racers try to keep tire growth to a minimum.

You say you are expecting 325/325tq on a boosted v6. You might pull off the larger tire with the right diff ratio, depending upon launch technique and torque at launch versus when the boost comes on. Sounds like unchartered territory and trial runs to figure it out.

Estimated power level is around 400whp. Not much torque tho as full boost doesnt hit til 4500rpm.

Im thinking 5 speed + 4.3 with at 24.5" tire puts me at 122mph on the limiter in 4th which should be good for an 11 sec pass.
Compared to a 23" tire 4th gear is only good for 115mph and I'd have to shift to 5th

Edit: assuming the drivetrain stays together after launch*

You have a short gear and good power so you will need the tall tire

So, I may have jumped ahead of myself. Orders some wheels and tires. Racing slicks. Now I look at Atlanta Dragway (nearest to me) and I'm not sure there is a class that I can race in. They have also reduced their Test and Tune days.

The best class would have been TrueStreet, but for that, must be DOT tires. I haven't found any cheater slicks small enough.

Need a track that is friendly to "imports", I guess.

Most tracks do test and tune one or two days a week.

If you are just starting to try drag racing, you will be better off with biased ply slicks. DOT tires are a bit less forgiving and require more time to get the setup all working properly. I really think you will be happy with the tires you originally picked out. Don’t over think it.

I also note, as I continue to overthink, that M&H has Street and Strip Tires in 13” that are DOT wrinkle wall. Not quite as soft a compound, but likely fine at my power level.

Would allow me to test and tune, and also run TrueStreet in same set-up.

Some say yes, Some say no.

Specific wheels that will? I am looking at AR95 Estrella, 13 x 5.5 for use with P205/60-13 for DOT rated wrinkle wall.

I looked at clearance between my 15" rim, and there is not 1" of space.

Exactly. I originally wanted to buy 13" mickey thompsons but couldn't find any 4x100 13x8 wheels that have an offset that will fit. Which would be around +25 or +35. Couldn't even find cheap steelies

gotta jack up the rear, if you can find a spinwerks dealer, they can make you anything you want at a reasonable price. Bisimoto used to sell them, also these weld knock off's would work.

Also look up VMS Modulo wheel 13x8 +20

Regarding jacking up the rear, when under load during weight transfer you want the CV axles to be perfectly straight with no bends or you will break them.

I exchanged a few emails with Bill Diamond of Diamond Race Wheels. The drop well on 13" wheels is 11.25". I measured my 1.8 brakes to be exactly that. I am not willing to grind my calipers, or run a wheel that is outside the fender. So... no go on 13's.

I really think you would be happy with the 15” low pro tire, but if you really think you need to try a 13” get a set of rear 1.6 rotors and caliper brackets. It’s cheap, and not a ridiculous amount of work to convert for a weekend of drag racing, then convert back.

My friends 13" spinwerks cleared my 1.8l brakes, I may have ran a 10mm spacer but I can't remember. I did pull my mtuned brackets and sport rotors. It was a quick swap.

I hear you. I also did a search of "site:miataturbo.net rota rb" and found that this subject has been discussed many times.

Again, my only issue is that I'm trying to both see what my best ET could be (15's perfect for that) and run True Street class, which eliminates the 15's as they are not DOT.

As I'm totally ignorant on 1.6, etc... Can I re-mount my 1.8 calipers onto the 1.6 brackets and run them with 1.6 rotors? I bet @curly knows. If so, yes that would be a quick and easy fix.

People remove and ditch 1.6 setups to upgrade for 1.8 all the time. It shouldn't be hard to come up with the calipers and brackets and rotors for the front. The rotating Mass and static Mass will be much better for you.

I converted to 1.6 for the reduced rotating mass. During the conversion, I noted the calipers were the same. I did note oddly enough that the 1.6 calipers were swapped left and right for some reason. Could have been brought to me backwards.

We are discussing the rear at this time.

https://cimg0.ibsrv.net/gimg/www.mia...163a8206f4.jpg
I know when upgrading the fronts you have to put the right bracket on the left and vise versa. I forget if the rear is the same, but calipers are all the same from 90-05, minus sport brakes. Just keep brackets paired with rotors and pads. So if you want 1.6 stuff, just grab 1.6 brackets, rotors, and pads.

you could always go crazy like the above pic.

Oops.

Speaking of heavy things, here's one of my mechanics with a steel shear we rent.

@curly, I just got in the 1.6 rear pads. I cannot see any reason that I would not be able to use my 1.8 pads on the 1.6 rotors. Do you know something I don't? I'm thinking I should just return these.

EDIT: I'd say that makes sense, now that I think about it.
Or is it just not a good idea to swap rotors on used pads?
I'll keep all my pads and rotors paired up.

In other news, I ordered rotors and 13" rims, getting some brackets.

Rims easily available are:

Konig Incident (13 x 5.5 ET 38), which I purchased
Americcan Racing (13 x 5.5 ET 35)
Pacer 83B (IIRC) in steel (13 x 5.5 ET 35), which I likely should have purchased due to cost and better match to the Compact Spare front wheels I have.

Why only 5.5” wide?

5.5 is a super narrow wheel, what do you plan to fit onto it?

DOT certified M&H Street and Strip Biased Ply. Recommended rim is 6.00, John at M&H says +/-1" OK with preference to - over +.

https://cimg8.ibsrv.net/gimg/www.mia...e4c762b479.jpg

https://cimg7.ibsrv.net/gimg/www.mia...829149d8b1.jpg

wow that's pretty interesting. really curious to see what they'll do to your ET

I think that is a good call on your wheel and tire choice. Really looking forward to the results.

It's not their stickiest compound, like a cheater slick, but should be fine with my low power. I can almost put full power on the 225 G-Force on street asphalt, so I'm thinking these should work well.

have you guys done anything else suspension wise to help your 60ft ?

I have stiffer rear springs, poly bushings, zero camber, zero toe, welded subframe mounts so they don't tear off, ford 8.8 diff bolted in with poly bushings (no PPF to flex), solid motor mounts, rigid trans crossmember, trans brake, air down mickey thompson drag radials. Setup has cut 1.67 60' times with a conservative launch and 2 yr old tires. I expect with launch control setup it would dip into the 1.5X range without any other changes.

Wheel & tire sizes pat?

stock 15x6 wheels, 225 size mickey thompson drag radials.

What kind of harness is required, and what will work with stock seats? 5-point / 6-point? Pictures?

I'm reading rules that if Convertible, then Roll bar is needed, and if Roll bar, then harness.

Seems to me a 6 point might be easier to install than a 5 point.

Thoughts?

Do you prefer radials over bias plies?

I run radials, they work well so I never tried anything else.

At this point, Pat has an automatic. Drag radials are normal with an auto.

For reference, here is what a 23x8x13 M+H slick looks like on a 7.5" 25offset Lenso wheel.
The wheel clears the brakes, and I can probably go 1.5" higher on the xidas if the tires rub.


https://cimg0.ibsrv.net/gimg/www.mia...c89ca5a89c.jpg
https://cimg7.ibsrv.net/gimg/www.mia...4d32c42ac7.jpg

That sidewall is drool.

Does it look like a 24.5 tall tire would fit?

Not comfortably with my setup. Clearance from top of tire to fender is currently 1-1/8"(stock fenders 2.5camber) and double checking,
I have closer to 1" more of height adjustment. So call it a comfortable 2" of clearance.

A 24.5" tire will be .75" closer to the fender and you will probably see about .50" of tire stretch at speed.

YMMV depending on your fender modifications, wheel offset, camber, spring rates etc.

BTW, the stock wheel/tire weighs ~33lb while this weighs ~23lb.

This is 13x8 +20 with 13x8x24.5 hoosier bias ply slicks.

No diff in the car and these are 1.5" taller than my standard setup so I have quite the monster truck look going on. Ill post final picture once ride height is lowered and car is in 4 wheels.

This confirms 13" wheels fit standard NB brakes. Cant wait to start replacing axles now

Attachment 222775
Attachment 222774

Question 1: Fuel lines.
Got the new NHRA rule book. Says no rubber lines and no clamps.

I am running the stock nylon line from steel supply to the rail. I think this is OK as stock. However, I have a rubber hose from the FPR to the steel return line. Both ends use fuel line clamps. Will this be a problem?

Question 2: Harness. Seems like without hardtop, I am required to use roll bar - OK - and Harness. Is that correct? I will need to install harness? Not all that expensive. Just checking.

I understand that Commerce is pretty much By the Book.

I plan to run True Street class and hope to break into 12's, and should realistically beat 13.5, which is a transition point, IIRC.

1) Check rules - I believe you're allowed 12" of cumulative rubber hose in the fuel system.

2) Any bar or cage that's not OEM installed requires an in date 3" SFI harness.

Thx. Yes, there was / is something about a length.

Fortunately, I do plan to install seats that will be compatible with a 5 point harness.

Also, though I don't know how they would know... is stock flywheel OK? There was something about not using a cast iron "stock type" flywheel. EDIT: Ordered a steel Flywheel: ACT 13-pound unit. Will go in with my SM Organic Clutch.

11.49 and quicker would need SFI flywheel/clutch and bellhousing or shield.

Non DOT slicks might require this stuff too. I believe 13.49 is a big deal without a hard top, and 11.49 is a big deal with a hard top, loops, shields, cages, ect... It's also interesting to note that it's 11.49 or 135.

So, on stick axle cars a rear sway bar helps them launch straighter. Is this true on the miata as well? I have mine removed for autocross, but can reinstall if it will help 60ft times.

My understanding is you want the biggest rear sway money can buy.