# Swap out the ZHP wheels?



## Andy (Jul 16, 2003)

I'm thinking about swapping out my wheels & tires on my 2003 330i ZHP and want to see what you guys would do if you were in my shoes (no pun intended  ). I really like the look of the ZHP wheels, however I wish they were lighter. I'm also wanting to put a wider tire up front based on my 255s Up Front Test.

I'm thinking about getting the following wheels and tires from Tire Rack...

- (4) 18x8.5 SSR Competition Anthracite w/Mach Lip ($429 each)
- (4) Bridgestone Potenza S-03 245/40YR18 ($205 each)

These wheels are only 16.5 lbs. each, the ZHP wheels are probably around 22 to 25 lbs. each. The lighter wheels will dramatically improve straight line acceleration. The 245 wide S-03 tires on all four corners will dramatically improve handling. Also, the Potenza S-03 are a lot better performance tire then my stock Potenza RE040s. Plus, with a non-staggered setup I'll be able to rotate my tires (front to back at least).

I really like the look of a stock car and LOVE the look of the ZHP wheels, that is why I am torn about this.

So... good idea or bad idea? What would you do?

Thanks,
Andy


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## AF (Dec 21, 2001)

Aren't those wheels available in 18 x 8 also ?

I wouldn't put 245's in the front, I think the 225/40/18 will provide you with a lot of grip if your going with the Bridgestone SO3's and put 255/35/18 in the rear if you want a staggered look.

They don't make a 245/35/18 Bridgestone SO3 . . . this is a pretty limited size, I have a set of Mille's with this size on the rear and my tires are Goodyear F1 GS D3

So now you need to rethink your plan and come up with something a little different . . . sorry bro !!


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## Nick325xiT 5spd (Dec 24, 2001)

245/40 will cost you more acceleration than a wheel diet gains you.

Plus, S-03s are freaking heavy.


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## Patrick (Dec 23, 2001)

Andy's wheel dilema(s) may soon be approaching "Alan F" status!

:angel: 

FWIW, I say keep the ZHP wheels.


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## Andy (Jul 16, 2003)

AF330i said:


> Aren't those wheels available in 18 x 8 also ?


They only offer the 8.5" wide wheel in the 18" wheels.



AF330i said:


> They don't make a 245/35/18 Bridgestone SO3 . . .


I'm looking at the 245/40/18s, which they do make, not the 245/35/18s.


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## hugh1850 (Jun 20, 2003)

Heavy or not, the M135's look great, they are one of the reasons I preferred the package; besides I like OEM wheels. Supercharge it to increase straight-line performance; I don't see lighter wheels making a statistically significant difference. You will get at least a half second by increasing the output by 100 hp.


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## AF (Dec 21, 2001)

Andy said:


> They only offer the 8.5" wide wheel in the 18" wheels.
> 
> I'm looking at the 245/40/18s, which they do make, not the 245/35/18s.


Why are you thinking of going with a 245/40/18 ? That size is too tall for your car and I really doubt you would be able to fit that size in the front let alone the back either without rubbing

There is no reason to go with a 245 upfront . . .

I would think you would get a crisper turn-in with a 225/40 upfront and all the grip you need or if you stick with a 18 x 8.5 wheel then go with a 235/40/18 up front and as an option go with that size on the rear too OR if you want staggered then go 18 x 8.5 front 235/40/18 and the 18 x 9 rear with a 255/35/18.


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## mbr129 (Aug 23, 2002)

I've thought of this even since before I got my car. But frankly, I think the M135's are part of the package's identity and, while I admit they are some heavy bastards, I must say that after driving on M68's for a couple of months, I don't see a big difference in performance. 

Perhaps some ultra-light wheels would make a difference, but am I not in the mood to spend that much money ona car that given my habits and skills, is above me. By the time I feel differently, I will (hopefully) have a sportier roadster. 

I'm leaving it stock.


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## Fifty_Cent (Sep 17, 2003)

Dont like those wheels, sorry. I prefer the stock ones, those ssr s dont look that good...well not on a 3 series at least. 
I dont think that performance is really such an issue on a car with 235hp...install some mod to make it a bit faster, and it will more than make up for it...

I like the stock ones, they look great and complement the car’s individuality.

Dont mess that up.


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## Andy (Jul 16, 2003)

Wow, I must say that I am surprised by the out come of the poll so far (one of those "yes" votes is mine). I would have thought the consensus would be to get rid of the heavy ZHP wheels and go with lighter wheels and wider tires. :dunno:

Well let me first start by asking a couple questions so I have a better understanding...

I know that lighter is typically better when it comes to wheels, so it sounds like this is more of preference of style. I like the ZHP wheels a lot too. However, I figured the drop in weight (close to 8 lbs per wheel) would be worth it. Plus, I think those SSR wheels look pretty good too.

However, my question lies with the tire choice. My thought is that wider is always better. More rubber on the ground means better grip in the corners. I wanted to reduce the amount of understeer that is built into our cars, so that is why I wanted to go with a non-staggered setup. 245s on all four corners seems like it would be better handling then 225s up front and 255s in the rear.

The tire ratings (on tirerack.com) on the S-03s blow the RE040s out of the water when it comes to handling and performance. I figured that this would be a WAY better tire and it would be a no-brainer going with the S-03s. However, as Nick pointed out the S-03 are pretty heavy (which I did not know), but still would offer much better grip then my RE040s.

So it sounds like the 8 lbs per wheel drop that I would get with the SSR wheels would be offset a bit by the heavier S-03 tires. I'm guessing that the each tire is maybe 2 to 3 lbs heavier, right? That still gives me a 5 lb weight advantage.

Now, in regards to going with a 40 mm side wall compared to the 35 mm side wall... As AF330i pointed out, Tire Rack does not sell a S-03 in 245/35/18s. My stock tires up front are 225/40/18, my rears are 255/35/18. I figured that since I'm running 40 mm tall tires in the front that I would be able to do the same in the rear. Is that not right? :dunno: 

I'm still undecided at this point, but tempted to just keep the ZHP wheels and mount stock size S-03 on them. I'm more interested in handling then I am in straight line acceleration (but having both sure wouldn't be bad  ).

Looks a side, is wider and lighter always better? :dunno: 

Thanks,
Andy


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## Nick325xiT 5spd (Dec 24, 2001)

Sidewall profile is a PERCENTAGE, not an absolute measurement. Why do you think people change profiles when they change tire widths?


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## Mr. The Edge (Dec 19, 2001)

if you are this concerned about weight, S-03's are about your worst choice for tires


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## Andy (Jul 16, 2003)

Nick325xiT 5spd said:


> Sidewall profile is a PERCENTAGE, not an absolute measurement. Why do you think people change profiles when they change tire widths?


I learn something new everyday... I did not know that. Wow, that makes a huge difference. I thought the sidewall was a measurement in millimeters, not a percentage. Come to think of it, I always did think it was a bit strange that the sidewall measurement changed when the width changed... now I know... thank you Nick.

So, with that in mind, the closest setup for what I am wanting to achieve is 255/35/18s all the way around, which I think is too wide up front with the S-03 (the S-03s 255s are 1/2" wider the RE040 255s).

Hmmmm...


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## Andy (Jul 16, 2003)

atyclb said:


> if you are this concerned about weight, S-03's are about your worst choice for tires


How much more do they weigh over the RE040s? Is it 2 to 3 lbs or even more then that? Anyone know?


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## Mr. The Edge (Dec 19, 2001)

Andy said:


> How much more do they weigh over the RE040s? Is it 2 to 3 lbs or even more then that? Anyone know?


I'm not sure how they compare with RE040s, but I do know that if weight (plus performance, obviously) is your goal, the Toyo T1-S seems to be the most popular choice.

235/40/18 Toyo=22.9 lbs

235/40/18 S-03=26 lbs


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## wrwicky (Jan 17, 2003)

Andy,

Essentially, lighter is always better.

More rubber is not always better. First, more rubber is heavier (see above). Second, for RACING APPLICATIONS you want just enough rubber to support the loads you will generate without overheating your tires. Autocross does not have long corners, sustained high speeds, or high aero loads, so for the street and autcross the stock sizes are already probably big enough. Maybe run 235s up front (or all around) to get balance.

Track RACING is different, the loads are sustained for a lot longer time and the tires really have a chance to overheat. For the most part, you can't get too much tire on a 3000 pound racing car.

Since you seem to love autocross and performance would really factor n, I'd get the comps in 17" (only if you can stay legal in the class you want to run) and a set of no kidding R (Oh my god! Here we go again) compounds in 235ish (pay more attention to mounted idth, not the marked size)in as low a profile as possible to keep the weight down, and to shorten your gearing to the min possible. Then, only run those at the autcrosses and tracks. and continue to enjoy your car with nice compromise tires on the stock wheels.

*But before you buy one more part, define your goal*. You can spend SOOO much money in racing that willl not help you if you don't have a firm idea of what you're trying to accomplish. It will matter a lot if you want to stay in BS, go fast as possible, evolve into a sprint or endurance racer, etc. There's a lot of us who dig your enthusiasm and want to give you advice that will help you succeed, but I don't think anybody (you included?) knows what your goal is. I think that's why so many guys tell you to leave your car alone, because we've all wasted a lot of money in our racing on parts and vehicles that we had to scrap once we figured out which class right for us.


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## PhilH (Jun 7, 2002)

Here's a tire size calculator that may help you.

http://www.powerdog.com/tiresize.cgi

Even though I like those SSRs, I'd stay with the M135 wheels. They help define the car, and right now, I'd say it's pretty cool to have a ZHP.

I'm going with 18" M72s over the M135s because the M72 is the correct BMW NA wheel for my car.


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## ff (Dec 19, 2001)

$2500 for a new set of shoes? No thanks. You must not have kids, in order to be even considering spending that kind of money for something that may, or may not, improve performance. Is a .02 second improvement in 0-60 time really worth that kind of money?

Also, are you sure that the S-03's are "a lot better performance tire" than the 040's? I have a feeling that they probably aren't much different (if at all). The 040's have handled everything that I could throw at them without so much as a hint of breaking loose. (disclaimer: DSC is always on). These are pretty damn good tires, and they're *significantly* better than the SP's Conti's.

Just my opinions, though. I think another set of wheels and tires is a monumental waste of money.

(edit)


Andy said:


> The tire ratings (on tirerack.com) on the S-03s blow the RE040s out of the water when it comes to handling and performance. I figured that this would be a WAY better tire and it would be a no-brainer going with the S-03s. However, as Nick pointed out the S-03 are pretty heavy (which I did not know), but still would offer much better grip then my RE040s.


You can't automatically go by that. 99.9% of the people that supply those ratings probably never have driven on both tires in order to compare. It's all about perception.


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## Andy (Jul 16, 2003)

atyclb said:


> I'm not sure how they compare with RE040s, but I do know that if weight (plus performance, obviously) is your goal, the Toyo T1-S seems to be the most popular choice.
> 
> 235/40/18 Toyo=22.9 lbs
> 
> 235/40/18 S-03=26 lbs


Looks like Toyo even offers a 245/35ZR18. Why doesn't Tire Rack carry these tires? :dunno: I would like to compare the ratings on the Toyos vs. the S-03.

http://www.toyo.com/tires/tire_specsheet.cfm?id=2


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## Mr. The Edge (Dec 19, 2001)

ff said:


> $2500 for a new set of shoes? No thanks. You must not have kids, in order to be even considering spending that kind of money for something that may, or may not, improve performance.


what on earth would having kids have to do with this?


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## ff (Dec 19, 2001)

atyclb said:


> what on earth would having kids have to do with this?


You must not have kids either. Kids cost a lot of $$$$$$$$, leaving very litle for papa to spend on personal pleasures.


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## Mr. The Edge (Dec 19, 2001)

ff said:


> Kids cost a lot of $$$$$$$$, leaving very litle for papa to spend on personal pleasures.


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## ff (Dec 19, 2001)

atyclb said:


>


 :dunno:


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## Mr. The Edge (Dec 19, 2001)

ff said:


> :dunno:


there's a LOT of folks here who have kids that don't mind spending $$$ on car upgrades, even purely :bling: upgrades


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## ff (Dec 19, 2001)

atyclb said:


> there's a LOT of folks here who have kids that don't mind spending $$$ on car upgrades, even purely :bling: upgrades


They must make a lot more money than I do.


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## Andy (Jul 16, 2003)

wrwicky, I appreciate the advise. Thank you. I have plans to purchase a set of wheels and R comp tires for autocross. However, I also wanted to purchase a set of wheels and tires for the street, that I could also use for autocross during the rain. The S-03s seem to be a pretty good performance tire in both dry and wet conditions.

ff, you're right no kids...yet.  You're also right about the Re040s. Those tires are the absolute best handling tires I have ever driven on, but when I compared the ratings on tirerack.com with the S-03, I thought to myself, "self... if the RE040s handle that well with those kind of ratings, imagine what the S-03 handle like with those ratings!!". But then again, I probably am giving those ratings/reviews a little too much credit.

I appreciate the feedback all of you have given me. You've given me a lot to think about. Thank you.


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## Cliff (Apr 19, 2002)

ff said:


> Also, are you sure that the S-03's are "a lot better performance tire" than the 040's? I have a feeling that they probably aren't much different (if at all). The 040's have handled everything that I could throw at them without so much as a hint of breaking loose. (disclaimer: DSC is always on). These are pretty damn good tires, and they're *significantly* better than the SP's Conti's.


They're a significant improvement over the RE040 both in terms of traction and wear.


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## mbr129 (Aug 23, 2002)

Echoing my post above, I am with ff in that that is way to much money to spend on wheels/tires when the car already has a pretty nice set to begin with. I plan on driving my M135's with RE040's until they wear out, at which point I will go with whatever seems like the best tire. Weight be damned.

Maybe it is just me, but I consider my car to be a great-performing daily driver that I can have fun with at AutoX. For that reason, I plan to keep it bone-stock. When I add a BoxsterS/S2000/Elise-like roadster a few years from now, maybe I will be more inclined to seek performance-enhacing mods for that car since I still will have the 330i as a daily driver. Although that type of car should be pretty damn good in stock form.


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## wrwicky (Jan 17, 2003)

Andy, 
You're welcome. With your reply in mind. You like the look of the stockers (so do I, or they would have been gone due to weight and 18" diameter) and you'll have dedicated drys to race with. Keep the M135s and go with the S-03s. They're heavy but they provide grip that is as good or better than any other street tire, with turn-in to match, and last as long or longer than anything else in their class

I think S-03s are pretty much the best rain tire out there. The Toyo T1-S, and Goodyear F1GS-D3 would make good alternate choices. Or you could consider my next set up, Bridgestone RE-750s 225 or 235/40s up front and 235 or 245/40s in the back, which are very close to S-03s in performance but last longer and cost less. Still a lot of grip for a street tire especially in the wet.

I'm a Bridgestone fan and particularly for anyone who values wet traction. Bridgestone is the choice for wet grip, especially over the life of the tire (UNI-T AQII). 

Why doesn't the rack carry Toyo? Apparently not commercially viable - too bad. They're pretty responsive, be sure to send them an email if it matters to you. Frankly, I'm astounded with all of the great stuff they do have and the excellent support they provide to us enthusiasts. (I have NO affiliation with TR)


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## Andy (Jul 16, 2003)

wrwicky said:


> *But before you buy one more part, define your goal*. You can spend SOOO much money in racing that willl not help you if you don't have a firm idea of what you're trying to accomplish. It will matter a lot if you want to stay in BS, go fast as possible, evolve into a sprint or endurance racer, etc. There's a lot of us who dig your enthusiasm and want to give you advice that will help you succeed, but I don't think anybody (you included?) knows what your goal is. I think that's why so many guys tell you to leave your car alone, because we've all wasted a lot of money in our racing on parts and vehicles that we had to scrap once we figured out which class right for us.


wrwicky,

I set three goals for myself back in October after completing the last race of the season. The first one, I think is definitely reachable. The second will be quite a bit harder and the third, well.... let's just say It would be a miracle if it happens. They are...

1. Win my first autocross event next year.
2. Qualify for nationals.
3. Place in the top 10 at nationals.

I must admit, I will be pretty disappointed if I am unable to achieve goals 1 and 2 next year. Those two are really my main goals for next year. Goal 3, well... to understand me you have to understand that I have to set goals for everything I do. You'll notice that each goal builds upon it's self. If I do qualify for nationals next year, I need a goal to shoot for when I'm there. Would I be disappointed if I don't finish in the top 10? Absolutely not!! In fact, I would be in shock if it does happen. It's just that I have to have that goal in place if I do make it to nationals... that's just how my mind works.


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## mbr129 (Aug 23, 2002)

Best of luck.


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## Andy (Jul 16, 2003)

mbr129 said:


> Echoing my post above, I am with ff in that that is way to much money to spend on wheels/tires when the car already has a pretty nice set to begin with. I plan on driving my M135's with RE040's until they wear out, at which point I will go with whatever seems like the best tire. Weight be damned.
> 
> Maybe it is just me, but I consider my car to be a great-performing daily driver that I can have fun with at AutoX. For that reason, I plan to keep it bone-stock. When I add a BoxsterS/S2000/Elise-like roadster a few years from now, maybe I will be more inclined to seek performance-enhacing mods for that car since I still will have the 330i as a daily driver. Although that type of car should be pretty damn good in stock form.


mbr129,

Thanks.

I pretty much have the same mind set as you. My ZHP is first off my daily driver and secondly my weekend autocrosser. I know that if I really ever want to be competitive at a national level that I'll need a different car (i.e the S2000 in B-Stock). However, I am just way too much in love with my bimmer to drive anything else and too poor to have a track-only car... well, ok actually too married to have a track-only car. I'm sure you married guys know what I'm talking about.


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## mbr129 (Aug 23, 2002)

Andy said:


> ... well, ok actually too married to have a track-only car. I'm sure you married guys know what I'm talking about.


I'll be in that boat as of August 14th 2004.


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## e46shift (Oct 12, 2002)

ballers


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## Andy (Jul 16, 2003)

e46shift said:


> ballers


Ballers? :dunno: What does that mean?

Based on your sig, I can tell you're not to happy with SSR Wheels. How in the world did that happen?


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## Dr. Phil (Dec 19, 2001)

Patrick 520iAT said:


> Andy's wheel dilema(s) may soon be approaching "Alan F" status!
> 
> :angel:
> 
> FWIW, I say keep the ZHP wheels.


 :rofl:

And agree :thumbup:


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## Andy (Jul 16, 2003)

Patrick 520iAT said:


> Andy's wheel dilema(s) may soon be approaching "Alan F" status!
> 
> :angel:





Dr. Phil said:


> :rofl:


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## JetBlack330i (Feb 8, 2002)

atyclb said:


> there's a LOT of folks here who have kids that don't mind spending $$$ on car upgrades, even purely :bling: upgrades


They have different priorities in life.
ff is correct. Kids (and cars) can be an endless pit for money. 
Here's a quick list of *optional* activities (two kids) for me. It doesn't include required basic items to raise kids, such as food, clothing, schoolling (supplies, tuition) and health care (braces) :
a) piano lessons ~ $200/month
b) Gimnastic lessons ~ $200/month
c) Soccer lessons ~ $190/month
d) Misc. expenses (toys, vacation and other gifts) ~ $100/month

("How much food can a child eat?" you ask. Son has been eating more than I do since he was 9, and it only gets worse from here. While most kids' choose McDonalds, mine chooses Texas Land and Cattle Steak House. :bawling: )
In other words, if I didn't have kids, I could pretty much afford to change the 4 tires *and the wheels with them* every 3 months, while still maintaining the same life standard. Have mercy!!! :bawling:
I've pretty much resigned to draw satisfaction from mod-ing my kids instead of from mod-ing my cars. :angel:


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## SpaceMonkey (Mar 13, 2002)

If these are going to be street only wheels, why on earth are you not considering 17"?

And if you're planning on using the SSR's at any autocross, you wouldn't be in BS anymore.


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## Andy (Jul 16, 2003)

SpaceMonkey said:


> If these are going to be street only wheels, why on earth are you not considering 17"?


I thought about that, but I really like the look of the 18" wheels, plus... (see below)



SpaceMonkey said:


> And if you're planning on using the SSR's at any autocross, you wouldn't be in BS anymore.


I do want to be able to use these for autocross. TireRack does not carry these wheels in 8" width, however Passen Motorsports a local performance shop told me they can get the SSR Comps in 18 x 8.


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## Andy (Jul 16, 2003)

wingspan said:


> bimmerfest rules!


Amen to that!! :thumbup: I learn something new everyday on this site and simply can't get enough.  Thanks wingspan.


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## ·clyde· (Dec 26, 2001)

Andy said:


> It looks like Goodyear Eagles will allow it, but unfortunately it's the Hoosiers that I am wanting and 8" is outside of their recommend rim range.
> 
> http://www.tirerack.com/tires/Spec.jsp?make=Hoosier&model=A3S03


 RX-8 guys are getting 275/35 Hoosiers on their 18x8 wheels and they are claiming that the 285/30s should fit too. Maybe Mazda 8 inchers are wider than BMW 8 inchers? :dunno:


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## ClubSpec330i (Oct 22, 2003)

Guys,

What do you think of 235/40-18 Kumho MX all around? Would it be a great tire for street and AutoX once a month? Would it be better than 235/245 combo? 

See you on the track!!!

Mack


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## wrwicky (Jan 17, 2003)

*225s Are Probably Fine*

Andy, 
RE: Are 225s enough? Don't get too hung up on any particular number. Remeber all of those sidewall numbers are suprisingly approximate and racing tires generally run wide.

I checked on TR and no specs were listed for the 225/40 18. The 225/45 17 (closest match) has a section width of 9.5". That's a fairly wide 2_*35*_ (9.5"x25.4mm/in=241mm). A lot of guys think those things are sized exactly, but they just round off numbers to whatever is closest and whatever shows more applications. The 245 Bridgestones I want to get are 9.6". So relax, you're getting very close to 245s as it is. Plus those tires will have alot more grip for the same amount of rubber. I'm guessing another tenth of a g easy.

Which size is better? For autocross (warning: free advice from a guy with only one autocross) probably the 225s for max agility. What's your style? Hard in, late apex, slow mid-corner, hard out (probably the big rears) or smooth and flowing with high mid-corner speed (probably matched sizes). Either way, don't worry, the beauty of soft compound tires is they'll be gone soon enough. If you don't like them just light em up and get the other size when you replace them.

Since you seem to enjoy discussing setup, I'm going to jump over to the racing forum and start a thread about setting up your car. Maybe we can combine all the bits of advice you've received into one coherent strating point for next season.


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## wrwicky (Jan 17, 2003)

ClubSpec330i said:


> Guys,
> 
> What do you think of 235/40-18 Kumho MX all around? Would it be a great tire for street and AutoX once a month? Would it be better than 235/245 combo?
> 
> ...


People seem to find them almost as good as the best tires in the dry, and a bit lacking in the wet. They wear quickly, and cost a lot less than S-03s and the like. I'd rather go for the S-03s, F1s, T1-Ss, which will work a little better all around and should last longer to varying degrees. Total cost with mount and balance per mile - probably about the same. Definitely YMMV.

I've been thinking a lot (and checking out a lot of threads) about sizes lately, and 235s all around seems to be about the most popular choice for non-track cars. Personally, my theory is maintain a slight stagger, but this is not the popular sentiment.


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## GregD (Feb 5, 2003)

wrwicky said:


> Andy,
> RE: Are 225s enough? Don't get too hung up on any particular number. Remeber all of those sidewall numbers are suprisingly approximate and racing tires generally run wide.
> 
> I checked on TR and no specs were listed for the 225/40 18. The 225/45 17 (closest match) has a section width of 9.5". That's a fairly wide 2_*35*_ (9.5"x25.4mm/in=241mm). A lot of guys think those things are sized exactly, but they just round off numbers to whatever is closest and whatever shows more applications. The 245 Bridgestones I want to get are 9.6". So relax, you're getting very close to 245s as it is. Plus those tires will have alot more grip for the same amount of rubber. I'm guessing another tenth of a g easy.
> ...


 :thumbup:

A couple of additional thoughts. The 225s on the stock rims will probably have more linear breakaway characteristics and be easier to drive at the limit. I think there's a high likelihood that you (and most people for that matter) would be faster on the 225s than the 245s with the stock rims. They'll also be a bit lighter which never hurts. 

Also, don't get too hung up on the oversteer/understeer thing. Driving style and inflation pressures can make a lot of difference. I had my car at the Streets of Willow a few weeks ago and after a few adjustments ended up with pressures of 37 front and 38 rear (the next morning after the tires cooled down). With these inflation pressures I had a small amount of understeer on most corners with a bit of oversteer on one uphill corner, and the car's understeer/oversteer attitude was very easy to adjust as necessary.


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## andy_thomas (Oct 7, 2002)

hugh1850 said:


> Heavy or not, the M135's look great, they are one of the reasons I preferred the package; besides I like OEM wheels. Supercharge it to increase straight-line performance; I don't see lighter wheels making a statistically significant difference. You will get at least a half second by increasing the output by 100 hp.


?

Heavier wheels add more than just static weight. The weight of the Style 135 wheel assembly is 50/55 lb F/R. 10 lb off this weight at each corner is a loss of 40 lb static weight. The centripetal acceleration experienced by the whole mass of the wheel as it rotates translates to a force (F=ma) which acts directly against the power generated by the engine as it turns the wheel. A formula can be used to express this force as a static weight increase at a given rotational speed, and for a typical wheel assembly it's something like twice the static weight increase, or around 80 lb in my example above, for a total of 120 lb.

Perhaps someone can post the equation used to epxress dynamic weight as static weight, over a range of speeds. It might be quite useful for finding out the objective impact of heavier wheel assemblies (not to mention the subjective impact on ride and handling).


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## ClubSpec330i (Oct 22, 2003)

GregD said:


> I had my car at the Streets of Willow a few weeks ago and after a few adjustments ended up with pressures of 37 front and 38 rear (the next morning after the tires cooled down). With these inflation pressures I had a small amount of understeer on most corners with a bit of oversteer on one uphill corner, and the car's understeer/oversteer attitude was very easy to adjust as necessary.


Hey GregD,

How did you do at Street of Willow? I am going this coming Sunday. What pressure did you start off with in the morning? I am deciding whether to bring my M68 set along so I can do a comparison in term of timing and hopefully a little drifting action at the end of the day. Let me know.. Oh! my OEM is RE040.

thanks,

Mack


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## GregD (Feb 5, 2003)

ClubSpec330i said:


> Hey GregD,
> 
> How did you do at Street of Willow? I am going this coming Sunday. What pressure did you start off with in the morning? I am deciding whether to bring my M68 set along so I can do a comparison in term of timing and hopefully a little drifting action at the end of the day. Let me know.. Oh! my OEM is RE040.
> 
> ...


I had a great time at the Streets of Willow. My goals were just to have some fun and get more familiar with the handling characteristics of my car in a relatively safe environment. I started out with pressures of 40 front and rear. It felt pretty good once I eliminated my excessive corner entry speed, and adjusted the pressures down a little ending up with 37 front and 38 rear as I mentioned above. I have the stock Michelins on my car.

Timing a stock car on a race track is an exercise in futility other than to see how your driving is, hopefully, improving. The day I was at the Streets, there was a nearly stock older Miata with 'R' type tires on it that was about the same as my car around the track. I'd gain on him on the straights, but he'd pull away under braking and through the corners. Some people were faster, some people were slower, way too many variables to make any reasonable comparison.

Sorry, drifting is not something I'm interested in. Just seems like a great way to go slow, and wipe out a set of tires in the process. Although I guess it can be an entertaining show. :dunno:


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