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Old 07-20-2005, 09:10 PM   #1
UltimateLurker
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Default Lets visit this one more time guys...

So, I'm in Barnes & Noble last night checking out the new EVO (the magazine) that I can't afford to spend $10 on, and I see an ad for a dealership in the UK that looks pretty cool. Apparently they're giving away Prodrive packs from now until the end of the year when someone buys a new STi (every country should be so lucky), something about full factory warranty, 40 ponies, an 18% increase in torque to 405 Nm, and a .55 drop off the -mile time. I'm thinkin' great, sign me up!

Anyway, I'm poking around on the Prodrive site a little while ago and I notice that there is no such pack available for the US-Spec STi (figures), and something catches my eye. I believe it was the line "To fully benefit from the extra torque levels available, fitment of 18" wheels and tyres are recommended."

Now, here on the all-knowing, all-seeing Nabisco, we've been all around the subjects of increased rotational mass & unsprung weight, and concluded that they both have their origins with The Devil. However, I've never heard anything eluding to the fact that smaller diameter wheels wouldn't allow an STi to take advantage of more torque.

At first I thought this might be a sales pitch, but on closer inspection I noticed that they're not trying to sell the PFF7's pictured on the website (and not in the magazine ad) as part of the pack, nor can you even get them as part of the pack, it's not even an option.

So, why would Prodrive say such a thing? Could it be that there's something we've all missed with regards to larger wheel/tire combo's? The JDM S203 didn't need 18's, did it? I mean, Subaru had to contact BBS and have the Diamond Black RE's made to their specs because they certainly didn't exist in 18X8.5 before, so why didn't they want them made in 16"? 17"?

Discussion welcome.
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Old 07-20-2005, 09:15 PM   #2
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Who gives a ****.....we never get the good **** anyway.....bastards.
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Old 07-20-2005, 09:20 PM   #3
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where on the prodrive web site. is this.
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Old 07-20-2005, 09:20 PM   #4
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never mind
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Old 07-20-2005, 09:23 PM   #5
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this is simple. if you have more torqe you will be able to use it more by apllying it over more surface area.

ie. if you have 8" wide tires you will be able to get more grip.
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Old 07-20-2005, 09:25 PM   #6
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Quiter.



15 minutes, that is a record!!, sometimes I forget that this is a forum not a chat room, let people come in and read and respond before you give up like that, it takes time and you will probably get a lot more thoughts during the morning.

If I knew enough to comment about this I would - but I'll let the 'informed' help answer your question.
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Old 07-20-2005, 09:51 PM   #7
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Quote:
Originally Posted by BREWPUBEAVER
this is simple. if you have more torqe you will be able to use it more by apllying it over more surface area. ie. if you have 8" wide tires you will be able to get more grip.
1. Incorrect.
2. No one said anything about an 8" wide wheel.
3. More lateral grip, but not more forward grip, and I hardly think Prodrive is talking about the application of torque in a lateral manner.
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Old 07-20-2005, 10:25 PM   #8
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Quote:
Originally Posted by UltimateLurker
"To fully benefit from the extra torque levels available, fitment of 18" wheels and tyres are recommended."
I read something similar on here that Prodrive USA recommended 18s too. It's got to be marketing IMO. My guess is it's a brand image type of thing, where they want to achieve a certain look...let's face it, almost everything comes with 17s now and to a lot of people they're too small.
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Old 07-20-2005, 10:27 PM   #9
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Quote:
Originally Posted by esteve
I read something similar on here that Prodrive USA recommended 18s too. It's got to be marketing IMO. My guess is it's a brand image type of thing, where they want to achieve a certain look...let's face it, almost everything comes with 17s now and to a lot of stupid, brainwashed, people think they're too small.
.....
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Old 07-20-2005, 10:28 PM   #10
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Am I missing something or does more contact area with the ground not mean less wheel slip? And could it have anything to do with tire flex? Like how on drag cars the tire folds on launch. I doubt either of those are the real reasons, probably a marketing pitch, which is why those wheels arent included, you buy them later seperate.
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Old 07-20-2005, 11:39 PM   #11
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OK, I'll open the can of worms. A wider tires does not mean more contact patch, it only means the shape of the contact patch changes. There are only 2 ways to "add" surface area to the contact patch...

1. Increase the weight over the wheels
2. Decrease the amount of air in the tires

A 205/55/16 has the exact same contact patch surface area as a 225/40/18 if they're both on the same car. The difference is that one of those patches is longer front to back, and not as long side to side, whereas the other one is longer side to side, and not as long front to back.
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Old 07-20-2005, 11:42 PM   #12
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Quote:
Originally Posted by esteve
I read something similar on here that Prodrive USA recommended 18s too. It's got to be marketing IMO. My guess is it's a brand image type of thing, where they want to achieve a certain look...let's face it, almost everything comes with 17s now and to a lot of people they're too small.
I've heard this same argument as to why Ferrari and Porsche still have drilled rotors. At the bottom of the Ferrari and Porsche rotor issue was the fact that drilled rotors that have the holes made into them at the time of manufacturing don't have cracking problems, and are lighter. Outgassing is no longer an issue.

I feel this is similar to our larger-wheels argument, there must be a real reason other than marketing.
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Old 07-20-2005, 11:57 PM   #13
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Quote:
Originally Posted by shoeler25
Am I missing something or does more contact area with the ground not mean less wheel slip? And could it have anything to do with tire flex? Like how on drag cars the tire folds on launch. I doubt either of those are the real reasons, probably a marketing pitch, which is why those wheels arent included, you buy them later seperate.
the reason a dragster's tire flexes is for the rubber band effect, not so much for contact patch size
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Old 07-20-2005, 11:57 PM   #14
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well I think the ad on the prodrive web site states whats in the package clear, they are claiming their sports exhaust, high flow cat, fuel pump, and ecu reflash will give you these gains, and it is said to upgrades wheels for full benifit (upsale).
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Old 07-21-2005, 12:12 AM   #15
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Quote:
Originally Posted by DriftZero
well I think the ad on the prodrive web site states whats in the package clear, they are claiming their sports exhaust, high flow cat, fuel pump, and ecu reflash will give you these gains, and it is said to upgrades wheels for full benifit (upsale).
1. It's not a claim, the dyno plot is right there.
2. The package is sold without the wheels, and gives said gains.

What we're discussing is exactly what Prodrive means by "fully benefit". I have a feeling that they're saying that the tires need to have a smaller sidewall in order to make the car handle correctly with the added power. Although the RE070 has an extremely hard sidewall, an extra 40 hp could raise the cornering speed beyond them.

Still, what sense does it make to advise an 18" wheel/tire combo for handling reasons without any other handling suggestions in the package? One could assume that they mean the 18" wheel/tire combo could be doing something other than increase the handling limits to help apply the extra torque to the ground.
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Old 07-21-2005, 01:19 AM   #16
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Quote:
Originally Posted by UltimateLurker
I've heard this same argument as to why Ferrari and Porsche still have drilled rotors. At the bottom of the Ferrari and Porsche rotor issue was the fact that drilled rotors that have the holes made into them at the time of manufacturing don't have cracking problems, and are lighter. Outgassing is no longer an issue.

I feel this is similar to our larger-wheels argument, there must be a real reason other than marketing.
I could see those points about the drilled rotors, but we're talking about 18" wheels/tires which in many cases will add weight and further out. If Prodrive were so concerned about performance, I'm curious as to why their BBK uses an extremely heavy 1-pc. rotor which also may or may not suffer from coning in extreme use.
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Old 07-21-2005, 10:27 AM   #17
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A good point. I've emailed Dan at Prodrive for more specifics on what exactly that quote means.
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Old 07-21-2005, 10:31 AM   #18
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Even with no increased torque, Prodrive recommends 18" wheels for a 2002-2003 WRX with their prodrive springs.

FWIW, I have driven a 17" wheel'd prodrive sprung car, then again when the owner put 18" on it. It handled better on the 18"s Which isnt typical, because the smaller sidewall of the 18"s usually mean tire bounce in corners, which reduces traction.
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Old 07-21-2005, 10:45 AM   #19
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Quote:
Originally Posted by UltimateLurker
OK, I'll open the can of worms. A wider tires does not mean more contact patch, it only means the shape of the contact patch changes. There are only 2 ways to "add" surface area to the contact patch...

1. Increase the weight over the wheels
2. Decrease the amount of air in the tires

A 205/55/16 has the exact same contact patch surface area as a 225/40/18 if they're both on the same car. The difference is that one of those patches is longer front to back, and not as long side to side, whereas the other one is longer side to side, and not as long front to back.
Thats really as simple as that. That assumes you're running tires at equal PSI. With correct pressure in the tires, a wider tire will increase your contact patch...but in theory, if its equal pressue, sure, they will have equal area patches.
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Old 07-21-2005, 10:59 AM   #20
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I like this thread ! I need this information. Actually I was reading about this last night and seems curious to me the thing about the 18"s. I also read in the W- site that actually there is a package available for US -spec.
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Old 07-21-2005, 11:04 AM   #21
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In my experience (have had on my both 17 and 18 prodrive wheels, pridrive springs, PPP3), the 18s help the car be a little more responsive, especially in regards to steering, but this is largely based on the tire you run. The 18s will typically have a stiffer sidewall simply b/c there is less of it to flex. Hence, you generally get a stiffer ride and a little more bounce with 18s than 17s.

Keep in mind that most full-body road race cars use 18's - I have even seen high tourque cars on 19's. The WRC cars also run 18s on tarmac.

I can only see how 18's could help with handling, no idea why they would want you to run a bigger wheel to get the benefit of tourque....makes no sense to me.
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Old 07-21-2005, 11:09 AM   #22
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Prodrive has been recommending 18" wheels on Imprezas since ~1999 when the P1 came out.

Do a search for "wheels" from poster Simon Lines or Mike Wood. Lots of info in the archives from 2000-2001.

Personally, I'm stunned that anyone would run 18s (with 225/35 tires no less!) on a street car driven aggressively on poor quality roads. That's a 3.1" sidewall. I wouldn't even make it to work without getting a flat tire on those rubberbands.
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Old 07-21-2005, 11:18 AM   #23
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Good responses, all, but I'm still no closer to understanding how an 18" wheel/tire combo would allow me to get "full benefit" of increased torque, or how a 16" wheel/tire combo wouldn't allow me to.

Jon: 225/40, and I drive 2.6 miles to work .
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Old 07-21-2005, 11:42 AM   #24
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Why when they talk about the stage 1 , they propose the oval tip , what's the difference between the oval and the round tip?
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Old 07-21-2005, 11:46 AM   #25
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Quote:
what's the difference between the oval and the round tip?
To give you the full benefit of moving exhaust past the bumper.
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