cretinx

what's the word on the long tube header from BHR?

I had a local place fab up a custom aluminum exhaust and I'm considering the DSP move next year, with a fabbed up custom header/midpipe (not aluminum!)

TeamRX8

iTrader: (25)

Better get them to start fabricating a stainless exhaust now to replace the broken aluminum one ...

ps: the bird is the word ....

cretinx

A properly welded aluminum exhaust has plenty of longevity. The folks at STM who built it have been running them for years.

I've had 0 problems so far and I lost over 33 lbs.

cretinx

Also - anybody play with the 5.125 ring and pinion or is 4.777 the way to go on the S1?

TeamRX8

iTrader: (25)

This thread is for SCCA D Street Prepared Class. The 5.12 gear ratio is not an allowed modification.

Only 33 lbs? Then my stainless exhaust weighs less. I've yet to see an aluminum exhaust last on a rotary application, but then maybe their solution was to make it out of heavy wall material and nullify any weight savings advantage.

Yield Strength

If it fails you won't be the first person here to have it happen ...

TeamRX8

iTrader: (25)

I posted a few updates in post #1 relative to the fuel cell allowance and update allowance for the 2009+ models

Kennetht638

iTrader: (2)

As Team alluded to, I had my aluminum exhaust fail in an autocross application. The whole catback with two mufflers was only 11 lbs. I don't think it's a foregone conclusion that it wouldn't work though since mine was definitely not supported as well as it should have been and I could have been a little bit smarter about where I put my flex joint to give it a better chance. But having seen how my exhaust vibrates especially on a Pro Solo launch, I just don't feel like giving it another shot. It was also way too loud. Another aluminum exhaust that I built for an STX WRX has held up extremely well though, and it even shows evidence of cone strikes.

cretinx

weld **** from my exhaust - Custom RX-8 Aluminum Exhaust by STM | autophiliac

Kennetht638

iTrader: (2)

Looks great! I would seriously recommend a flex section somewhere after the midpipe hanger on the PPF though. You're otherwise putting a bunch of stress on the flanged connection to the midpipe. If it works just fine though, you can ignore me! Also, is that not super loud? I found that the Vibrant cans do almost nothing. Edit: I see that you have the stock cat in place, so maybe it's not as obscene as mine was.

TeamRX8

iTrader: (25)

and my early STX version in 20 Ga. Stainless below

large center resonator is now a Moroso sprial-flow, rear cans and tailpipes are similar to yours just stainless, and the cat goes away for DSP. The entire exhaust system including custom header manifold will be under 25# in DSP trim. Plus as I have eluded to before, making the RX8 lighter in the rear is easy. Not really looking for less weight there.





exhaust system above now has four seasons on it, will last forever

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cretinx

It is shockingly NOT loud - everyone is blown away at how good it sounds.
Here's my secret - 2.5" piping.

Why?
Because I've been running in CS and the 2.5" outlet from the header is already a bottleneck.

cretinx

that looks great.

I wonder how much mid-range torque our cars could pick up with a nicely designed custom header and cat removal?

But, to be honest - in CS trim at least, I've never come out of a corner and said "I NEED MORE POWER" - car manages to keep pretty high cornering speeds so it's always on boil coming out.

I'm always screaming for more grip.

And I used to race a CP Firebird.

TeamRX8

iTrader: (25)

I have no idea ....

BLUE TII

I'm always screaming for more grip.

In case anyone else wanted to try the 18x11 +45 295 fitment I mentioned but was worried.

Here is a shot from this weekend of my 18x10.5 +38 F/R w/ 265/35-18 Ventus TDs.

Outside wheel and tire is in *exactly* the same spot as my 18x11 +45 w/ 295/30-18 that I was racing on previously.

Stock front fenders, never a rub. Zero paint missing from fender edge, zero abrasion on plastic fender liner or rivets.


Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit

TeamRX8

iTrader: (25)

No it's not. Where the tire face and corner is will be completely different. The 265 on a 10.5 is as stretched as a non-confessing devil worshipper on a Spanish Inquisition torture rack. This is not a street tire thread either; Hoosier race rubber runs wider at the corner area.

I ran 265/35-18 yokohama AD07 street tires on 18x10.5 +45 with zero fender mods/rubbing front or rear over 7 or 8 years ago as documented on this forum.

I'm not really sure what you're trying to prove. 11's can be made to fit, but when the tire OD and width becomes that large there will be some rubbing issues to address in one form or another.

TeamRX8

iTrader: (25)

and just to make the point, here is the 295/30-18 on an 18 x 10.5 +43 with a big f'ing gouge in it. This was just driving around at moderate speed in a bumpy parking lot. The tire would be lucky to get through an autox run or two before going flat. Maybe you were lucky and got some magic front fenders on your car that mine doesn't have it's a moot point regardless since we are allowed to roll, cut, or add flares in DSP.

Getting back on topic, I forgot how fun port matching is ....

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BLUE TII

I wore out the 295/30-18 on 18x11 +45 racing and there was no rubbing.

"What I am trying to prove" is that as the picture shows there was plenty of opportunity for the 295 on +45 offset to rub and it didn't. No paint worn off the fender edge, no wear marks on the plastic fender liner or rivets and no marks on the tire.

You keep referring to the Ventus TD as street tires, which is amusing but wrong. I have already corrected you on this and shown you that their tread width is wider than the Hoosier in the 295.

Hankook Ventus TD

295 on 18x11 +45 worked with stock fenders for me.

295 on 18x10.5 +43 required a fender roll for you.

I am not arguing with you.

In posting the picture I was providing more information for the people who are looking for more grip such as the quoted user cretinx.

They can decide their future wheel/tire fitment based on information provided.

TeamRX8

iTrader: (25)

This is a racing thread and you are on street tires. A 1/2" wider wheel is not going to stretch a 295 Hoosier race tire in past that gouge position. Your outer bead seat position is approx. 0.2" further outboard than the wheel in my pic if your specs are correct. People need to understand that the math just doesn't add up for the information you are providing, plain and simple. My car was in the basic suspension prep of this class discussion and yours is not. IMO you are either misleading people and/or do not have accurate information for wheel width, offset, or comparative tire sizing/suspension setup.

The Bogart 17x10.5 wheels have a lot of clearance from both control arms and the tie rod at full lock. No, I did not order 7.25" backspace or by backspace at all. Closer to 8" taking a rough look at it with the tape measure. So far it is just the wheel fit to the car on jackstands. It may be that the tire will rub inboard once mounted on the ground in full race trim. I have five full sets of spacers ranging from 3mm - 15mm with 2.5" long ARP race studs to fine tune if necessary. My goal is to get the tire well supported and as far in board as possible.

I've f'd around with all these different sizes for many years. My assessment is that a 295/11" won't offer enough to overcome the diameter/weight difference and certainly not a 315+. Again, Brian smacked down on the DSP class at Nationals last year with the 275/35-17 on a heavier more powerful BMW with a codriver. There are certainly a lot of factors, conditions, and situations that affect the outcome of any race. I don't see how going larger is of any benefit at this point, but I'm always open to the idea down the road.


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Kennetht638

iTrader: (2)

#1: The Ventus TD is most definitely NOT a street tire, which I think has been re-hashed a few times in this thread. It's a 80 treadwear DOT-R. It's not a Hoosier A7, so maybe it's not as relevant to this thread as some might like, but it is a tire that can be run in SP and not in ST or Street classes. It's about as much a street tire as a Hoosier DOT-R.

#2: Blue TII, I'm a little surprised that you don't have any issues with rub, but from what I'm seeing in the tire specs that I could find, the Ventus TD in a 295 actually has narrower tread width than the 285 BFG's that I'm running. As I mentioned earlier in this thread, I had to roll the rear fenders but was able to leave the fronts alone. I get some rubbing on the control arms and the firewall near full lock. However, I'm much lower than stock ride height so maybe you're just able to stay out of a travel range where these things are an issue?

TeamRX8

iTrader: (25)

my bad then, not really a street or a track tire, kind of a tweener

Hankook Ventus TD

BLUE TII

#2: Blue TII, I'm a little surprised that you don't have any issues with rub, but from what I'm seeing in the tire specs that I could find, the Ventus TD in a 295 actually has narrower tread width than the 285 BFG's that I'm running. As I mentioned earlier in this thread, I had to roll the rear fenders but was able to leave the fronts alone. I get some rubbing on the control arms and the firewall near full lock. However, I'm much lower than stock ride height so maybe you're just able to stay out of a travel range where these things are an issue?

Nice, that is awesome that you were able to fit those wide 285 R1-S on stock front fenders!

That is correct, the 295 TD tread width is just over 1/4" (.3") narrower than the 285 R1-S and just under 1/4" (.2") wider than the 295 Hoosier A6.

I did state that the wheel inner lip rubs the front lower control arm around full lock, if it didn't interfere first the tire sidewall might rub at full lock as yours do.

I also stated I had to roll the rear fender lip under.

Only thing I can think of is TeamRX8 put the 18x10.5 +43 and 295 Hoosiers on his car with the car lowered and as much camber taken out as possible because he had been racing on street tires and was not familiar with DOT-Rs.

As we know, one has to fit the wheels/tires with as close a set-up as you are going to race as each degree of - camber on a 25" tire moves the outer tread block 11mm inward away from the fender edge.

Wide DOT-Rs are going to require all the camber you can muster stock and then likely some more.

Us FD RX-7 guys get around -2.5 stock and use eccentric bushings to get around -5 on the 285 Hoosier A6s. RX-8 may have more front camber gain though and require less static camber.

May I inquire about your set-up Kennetht638?

About what range of static camber do you run on the 285 R1-S?
What is the offset of the wheels you use with the 285 R1-S?

Thanks.

TeamRX8

iTrader: (25)

My car has way more camber than yours, max capable is over -3 deg thanks to custom offset upper control arm bushings. These put the top of my tire further inboard than yours too.

Kennetht638

iTrader: (2)

My bad, I had looked through the thread to see if you had rolled the rears and couldn't find it. That makes a lot more sense.

When people ask me how much camber I run, I usually just say "all of it." I have the adjusters maxed out in the front to get the tire temps that I want so I don't even bother measuring it. I actually have the rears just shy of maxed out too. I know I measured them last year but I don't remember the numbers.

The wheels are 18x10 +38. I posted this picture of the tire at full jounce with the spring removed on the first page of the thread, but it shows that I have a tiny bit of room before rubbing the front fender sheetmetal, but it definitely contacts the fender liner. I guess my rates are high enough that I haven't actually had it contact while driving though.



And just for fun, this is what it looked like in the rear before rolling the fender lips:

TeamRX8

iTrader: (25)

I had 900#/in front springs and a 1.25" OD x 0.25" wall front speedway swaybar when the 295 interfered, my shocks allow much more full travel up into the wheel well too

just to summarize the sizes we have been discussing

18 x 8.0 +50, OE size, base reference for aftermarket wheel lip positions

18 x 10.5 +43 .... 38.50mm further outboard, 24.75mm further inboard

18 x 11.0 +45 .... 42.85mm further outboard, 33.10mm further inboard

18 x 10.0 +38 .... 37.15mm further outboard, 13.40mm further inboard

17 x 10.5 +56 .... 25.75mm further outboard, 37.75mm further inboard



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TeamRX8

iTrader: (25)

so after all this discussion and considering the above, is there a possibility that BlueTII's 18x 11 wheels have a deeper offset than +45? Given the above it doesn't make sense that the 11 +45 wheel is closer to the control arm than the 10.5 +56 wheel.

It's pretty much a standard that the distance from the tire bead seat to the outer wheel lip edge is 0.5". A formed wheel shell just has the lip rolled out to this dimension to provide stiffening whereas the forged/cast wheel lip is typically solid out to the same dimension.