Ok, so now that we've discussed tires. The next issue is wheels for these tires.

They need to be wide enough to handle the max 275s for STU - but also able to handle the 285s for running V710s in BSP. They need to fit properly - of course. Should be lightweight but not too expensive.

Someone recommended the Enkei RPF1 18x9.5, 45mm offset. They weight 17.2 pounds and are available at good-win-racing.com for $309 a piece.

I was told this is the biggest size that will fit all 4 corners properly (as I prefer to NOT be staggered for better balance) and that I may have problems with 10" wheels.

So is this the best option that meets all my needs or does someone know of an even better option?

Thanks in advance for your inputs.

there is a thread on the forum where someone already ran 10" wheels with 285/30 tires at all four corners, I personally don't think it will be an issue and IMO you can likely get 10.5" wheels to fit though there may be some rubbing at full lock in the front. The difference is the price of entry is going to be much higher than the Enkei setup. You can't get close to their value/weight without spending at least twice as much.

I bought the Enkeis to start because the deal really can't be beat. If the car looks to be competitive nationally I may pony up for the increase, but not before.

...You can't get close to their value/weight without spending at least twice as much.

That's what I was thinking. Thanks for confirming. They're pretty much the best "bang for the buck" wheel and will probably do everything I will ever need - especially if I can fit 285s on them - which I think I can.

285 V710's will be a tight fit on a 9.5" wheel, it will probably just depend on how skilled you're tire mounter is, the regular tire shops can't get the 245 V710 to seat on an 8" wheel, a skilled race tire mounter has very few problems

Has anybody tried the 16x7.5 wheels in stock class? My experience with other cars is that smaller diameter wheels with less rotational inertia and better gearing from a smaller diameter tire were generally more competitive. With the 8 having such a factory wheel option it would be allowed in stock. This seems to me like it would be the hot ticket, even giving away 1/2" width. You could probably still get a 225 on a 7.5" wheel. For SP, STU and the like, I would still think the widest 16" wheel you could fit would be the fastest option.

This assumes a similar width/profile wheel so that the overall tire diameter and gearing is reduced.

16 on what car? The base '04 auto? Cause as I understand, 16 wont fit on a sport package.

:newbie:'s should not be seen or heard ...

Has anybody tried the 16x7.5 wheels in stock class? My experience with other cars is that smaller diameter wheels with less rotational inertia and better gearing from a smaller diameter tire were generally more competitive. With the 8 having such a factory wheel option it would be allowed in stock. This seems to me like it would be the hot ticket, even giving away 1/2" width. You could probably still get a 225 on a 7.5" wheel. For SP, STU and the like, I would still think the widest 16" wheel you could fit would be the fastest option.



This assumes a similar width/profile wheel so that the overall tire diameter and gearing is reduced.

Not only do they not fit a 6spd car, brakes are to big, but they are not legal in stock class on a 6spd car.

It is hard to beat that deal if you can wait for them. Any other 9-10" wide wheel seems to weigh more or cost way more. The good news is a 285 will fit a 9" wheel, the Boxster S uses them on a 9" as well as some guys I know with a DSP BMW, so a 9.5" should not be a problem at all. Get your name on the list. :biggthump

Ok, so now that we've discussed tires. The next issue is wheels for these tires.

They need to be wide enough to handle the max 275s for STU - but also able to handle the 285s for running V710s in BSP. They need to fit properly - of course. Should be lightweight but not too expensive.

Someone recommended the Enkei RPF1 18x9.5, 45mm offset. They weight 17.2 pounds and are available at good-win-racing.com for $309 a piece.

I was told this is the biggest size that will fit all 4 corners properly (as I prefer to NOT be staggered for better balance) and that I may have problems with 10" wheels.

So is this the best option that meets all my needs or does someone know of an even better option?

Thanks in advance for your inputs.

how long a waiting list for the enkeis?

also, are these wheels strong enough for daily use? or will they bend at the sight of a pothole? I want to drive the car to the track without bringing a set of wheels. I'm just paranoid cause I had gram lights which bend easily and when they do bend, they are garbage. Those wheels are cast aluminum so I'm kinda scared to buy anything but forged.

well not exactly ...

http://www.enkei.com/technology.html

Yeah I've read about M.A.T. before. I'm not totally convinced about this "most advanced technology". Seems like some corny advertising bs. Bottom line.....Cast is cast and forged is forged. I still really want these wheels but if I end up cracking one, waiting for a replacement would suck.

lol, I guess you won't use SSR Comps either ...

lol nope they're discontinued anyways.

I know you're being sarcastic team. Thing is, the roads here are pooh. At least forged wheels are repairable.

^^ What makes you think the forged wheels are more repairable?

If they break...they are broken :D:

The stock wheels are very fragile....the Enkei's are at least as strong as the stockers

^^ What makes you think the forged wheels are more repairable?

If they break...they are broken :D:

The stock wheels are very fragile....the Enkei's are at least as strong as the stockers

I know that but cast wheels are not fixable even when bent.....

Not only do they not fit a 6spd car, brakes are to big, but they are not legal in stock class on a 6spd car.

Makes sense. I thought the brakes seemed too large to squeeze into 16" wheels.

For non-stock classes, you could still get a 17x8 RP02 or RP03 in there and reduce your weight and diameter some. Probably not worth losing the width unless you could get at least a 17x9.

ULLLOSE and carbonRX8, I appreciate your relevant and polite answers.

Makes sense. I thought the brakes seemed too large to squeeze into 16" wheels.

For non-stock classes, you could still get a 17x8 RP02 or RP03 in there and reduce your weight and diameter some. Probably not worth losing the width unless you could get at least a 17x9.

ULLLOSE and carbonRX8, I appreciate your relevant and polite answers.

Right.. A 17X8 would be a step back. Now a 17X9-10 with a 275 would be nice.

Here you go. Offset seems a little low, but good-win lists them for the rx-8, so I would assume they fit. Reasonably light for a wheel that wide too.

http://www.good-win-racing.com/mazda/miata/60-1082.html

What I didn't look up is if you can get tires to match, but my guess is that you can.

This should be a faster auto-x setup than any 18".

I trust Brian Goodwin to list the proper wheel (#) for the proper car (#). You can call them if you want to make sure. He is very helpful. Highly recommended. (I bought my wheels (#) from him). As far as recommending the wheel for your application...:dunno: It is a fallacy that 17" are necessarily faster than 18". On a track the 18-9.5 inch RP-F1s will be faster (with the right tire and driver, of course) I would recommend HPDE first before any track-worth mod.

more n00bs who can't search ... :rolleyes:

more n00bs who can't search ... :rolleyes:

I'm just trying to help out with a little info. I thought that's what this group was for. If I'm looking for personal insult advise, I'll be sure to look you up.

Everybody was a "nOOB" at one time.

overly-sensitive one's too ...

...I would recommend HPDE first before any track-worth mod.

Agreed, but I have more than the average amount of racing experience already. I'm not planning to seriously auto-x my 8 right now, I have a different racing toy. If I did, I would just go stock and so wouldn't be able to run the 17s.

17s are not always faster than 18s, but the lower gearing and reduced rotational inetia offered is usually an advantage on a low speed event like an auto-x. For a particular auto-x that will depend on the course setup and particularly if you can still hold second without hitting the limiter. If the lower gearing forces more shifts then it will almost certainly hurt your times. But it is easier to start with smaller wheels and tires than installing a lower final drive like I have seen discussed elsewhere. Also, when you switch back to your streets, you are back to your normal gearing.

Just my $0.02.

I wouldn't go 17 for one simple reason. Tire sizes.

Agreed, but I have more than the average amount of racing (#) experience already. I'm not planning to seriously auto-x my 8 right now, I have a different racing toy. If I did, I would just go stock and so wouldn't be able to run the 17s.

17s are not always faster than 18s, but the lower gearing and reduced rotational inetia offered is usually an advantage on a low speed event like an auto-x. For a particular auto-x that will depend on the course setup and particularly if you can still hold second without hitting the limiter. If the lower gearing forces more shifts then it will almost certainly hurt your times. But it is easier to start with smaller wheels (http:///#) and tires (http:///#) than installing a lower final drive like I have seen discussed elsewhere. Also, when you switch back to your streets, you are back to your normal gearing.

Just my $0.02.Lower gearing? The tire (http:///#) circumferance should be about the same. Just that you will have a higher profile than with the 18s. So you are planning to run 45s on a 17? Just run with 225/40-18s and you will get the same "gear reduction." IMHO this is a really bad idea. Where do you race your car?

If you have an equal profile and equal width, the 17s will have a smaller diameter than the 18s. As you note, changing the profile from a 45 to a 40 will accomplish about the same thing, although the 17x..45 will still have less rotational inertia than the 18x..40. Going to a 40 reduces your slip angle a little, which will make the car a little "twitchier" but will also bleed a little less energy through the turns. For auto-x, I don't think the difference between a 40 and a 45 is too important. For high speed events, the reduced profile could make the car a bit trickier to handle.

But going from a 225mm width to a 275mm width will significantly change your tire circumference. If you go from a 225mm to a 275mm but assume you stay with a 18in and a 45 profile, your sidewall is going to increase 0.45*50mm, or 22.5 mm which is nearly an inch, so your overall radius will also increase that inch thus increasing your gearing. Going to a 17 will help offset this increase somewhat.

Simple examples of the radius from the axle to the tire patch:
Radius = 1/2 wheel diameter + (tire width * profile)
so
stock: 18in/2 + 225mm*.45 = 9 in + 101.25mm ~= 229mm + 101 = 330mm
18x275R45: 229mm + 275*.45 ~= 352mm
17x275R45: 8.5in + 275*.45 ~= 216mm + 124mm = 340mm
17x275R40: 216mm + 275*.40 = 216mm + 110 = 327mm

The circumference will be 2*pi*Radius, but that isn't important. If the radius goes up %2, then the circumference will go up the same %2.

All 3 of the 275mm examples have a taller sidewall than stock simply because the tire width goes up ~2in., so the sidewall goes along with that unless you reduce the profile.

If that is all obvious and boring, I apologize. I just find it easier to think of this with some actual numbers.

I'm not planning on racing my 8 this year, but I'll be racing a kart out on the left coast, near Portland, OR. Chassis setup on a kart is a bit different, but racing is racing. On the kart, everything just goes out of control a bit more rapidly. Not that the 8 wouldn't be a lot of fun to race, but if the guy next to me wants to bump the side of my kart, new side pods cost about $40.

overly-sensitive one's too ...

I've been called thick, but sometimes I might not be thick skinned enough.

frankly you sound like a guy who read a bunch of books, but otherwise lacks practical experience in the topic he's trying to discuss.

for starters, setting up a kart is a lot different than a production car, a lot ...

and in the real world, the general theory of tire inertia is not so important as compared to the actual magnitude of comparable differences relative to all the other factors that come into play with regard to tire performance on a 3000# car, many of which outweigh what you're going on about ...

further, maybe you'll find it easier to think about practical tire sizes like 275/35-18, 285/30-18, etc. and other annoying real world practicalities such as available wheel sizes and their weight/cost. The manufacturers actually provide the data for you; no calculator is required

perhaps the most practical of all, consider asking questions to start rather than espousing ... i.e. ask if 16" wheels fit before going on about it pointlessly when in fact they don't. You're more likely to get the kid-gloves treatment that way ...

Simple examples of the radius from the axle to the tire patch:
Radius = 1/2 wheel diameter + (tire width * profile)
so
stock: 18in/2 + 225mm*.45 = 9 in + 101.25mm ~= 229mm + 101 = 330mm
18x275R45: 229mm + 275*.45 ~= 352mm
17x275R45: 8.5in + 275*.45 ~= 216mm + 124mm = 340mm
17x275R40: 216mm + 275*.40 = 216mm + 110 = 327mm



To bad there are no 275-45-18 track tires, nice try, now if you use real race tire sizes that you can buy it looks like this:

Tire Size Sidewall Diameter Circumference Rev/Mile Difference
225/45-18 4.0 in. 25.97 in. 81.59 in. 777 0.0% stock size
245/35-18 3.4 in. 24.75 in. 77.76 in. 815 -4.7%
265/35-18 3.7 in. 25.30 in. 79.49 in. 797 -2.6%
285/30-18 3.4 in. 24.73 in. 77.70 in. 815 -4.8%
245/40-17 3.9 in. 24.72 in. 77.65 in. 816 -4.8%
245/45-17 4.3 in. 25.68 in. 80.68 in. 785 -1.1%
275/40-17 4.3 in. 25.66 in. 80.62 in. 786 -1.2%

<snip>
perhaps the most practical of all, consider asking questions to start rather than espousing ... i.e. ask if 16" wheels fit before going on about it pointlessly when in fact they don't. You're more likely to get the kid-gloves treatment that way ...


Give screamindean a break, he asked about the 16s and got an answer that they didnt' fit. Sounds to me like everything else he wrote thereafter is not untrue; if it's of no interest to you personally, leave it be. I personally find this topic interesting, and would hope that additional thoughtful discussion/input would not be discouraged.

^^^yeah, but everything he asked has been covered in depth many times on here. He could of searched to begin with.

Give screamindean a break, he asked about the 16s and got an answer that they didnt' fit. Sounds to me like everything else he wrote thereafter is not untrue; if it's of no interest to you personally, leave it be. I personally find this topic interesting, and would hope that additional thoughtful discussion/input would not be discouraged.It's only discouraging for those who choose to be overly sensitive to the style of delivery. Keep in mind, we've got a bunch of smart guys here with real-world knowledge trying to help steer. People should take advantage of that, along with the wealth of knowledge already loaded in these forums.

A problem with espousing and speculating and running calculations to come up with theoretical numbers is that other new people will read those & think its true. As mentioned before numbers aren't the gospel if the combination doesn't work with everything else.
-dk

..now if you use real race tire sizes that you can buy it looks like this.. (shortened for brevity)
Two of the choices you mentioned were:
245/40-17 3.9 in. 24.72 in. 77.65 in. 816 -4.8%
245/45-17 4.3 in. 25.68 in. 80.68 in. 785 -1.1%

Hypothetically, would it be safe to say that the 245/40 is a "better" choice out of the two above for autocross because it has slightly less intertial mass (for quicker acceleration) as well as better handeling (shorter sidewalls means less tire roll)?

I've enjoyed reading over the discussion and am not too worried about some of what has been entered that could be interpreted as, well, not overly kind. Those notes that point out the deficiencies in my posts are useful. Those that ignore what I have to say because I am a noob, or because the poster somehow divined my racing experience based on a few posts, well, those posts are useful too, at least in understanding the poster.

And to be clear, no I don't know diddly about the specifics of RX8 chassis setup. I'm new to the car and learning along with many of the rest. And absolutely, chassis setup for a fully independent suspension on a 3000lb car is very different from a solid rear axle, 360 lb (including driver) kart.

But I do have a fair bit of experience with tires, including car tires and the basic effects of width and profile are the same everywhere. Gear ratios are also very straightforward. The beauty of changing tire sizes is that they don't significantly change chassis geometry (except for a trivial bit of ride height). So you don't necessarily need a detailed knowledge of a specific car's suspension to discuss tires and wheels.

OK, enough of that.

I will give credence to what somebody says based on their demonstrated experience. When somebody can say "05' SCCA BS Natl Champ", I gotta pay attention to that. Interestingly , ULLLOSE did point out there are 275-40/17 and 285-30/18 (wow!) racing tires. Also ULLLOSE said, "Right.. A 17X8 would be a step back. Now a 17X9-10 with a 275 would be nice" With that Enkei 17x9.5 wheel and the 275-40/17 wheel you could do that and keep yourself slightly below stock gearing.

And before I get jumped on, no I don't know that it would necessarily be faster, but clearly it can be done on the RX8

"Are you pissing in someone's pool again?'

"Yeah. And we're fresh out of chlorine"

One small followup. My previous post is not intended to imply that the only smart guy on this board is ULLLOSE. It's just that I don't know much about anybody on this board yet. I don't know who knows their stuff and who just has a lot of opinions. I do know that a national champ knows his stuff.