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Old 02-09-2007, 02:17 AM   #1
chimchimm5
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Default 225/45/17 on a WRX is bad final drive?

My 06 WRX came with 215/45/17 and I noticed the STi size of 225/45/17 provides a whole lot more tire choices than my stock size. For example, the Falken RT615 don't come in 215/45/17 and neither do the new Bridgestone RE-01R's.

I know they "will fit". But since the diameter of my wheel/tire would be increasing with the 225's, how bad is the effectively increased final drive? (or is that decreased?)

IE, does it bog down the WRX?
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Old 02-09-2007, 07:22 AM   #2
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...no

...and if being here and reading ALL THESE POSTS didn't answer THAT question LONG AGO.....
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Old 02-09-2007, 09:05 AM   #3
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I just put 225's on, after bugging Uncle to make sure before I spent the $$, and they drive and look much better. re960 pole positions.
It should be a damn sticky.
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Old 02-09-2007, 11:10 AM   #4
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There is only a 1.4% difference. Not noticeable. The 215s are too small anyway. 225/45 is closer to 205/55-16 which is what older WRXs ran.
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Old 02-09-2007, 12:26 PM   #5
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Originally Posted by waktasz View Post
There is only a 1.4% difference. Not noticeable. The 215s are too small anyway. 225/45 is closer to 205/55-16 which is what older WRXs ran.
.......the older WRX is NOT the same car and should NOT be compared.

the older wrx, with less torque and the gear ratio's, could actually benifit from a shorter tire.


the new wrx is different.

going to a bit taller tire with the '06+ isn't an issue, especially if the car is a bit modded and has more power.
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Old 02-09-2007, 12:35 PM   #6
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^^^Again, not a big deal.
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Old 02-10-2007, 10:45 AM   #7
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not to contradict above posters, but i spoke with Subydude last week about getting new 17x8 rims w/ 235/45/17's and they informed me that they dont recommend 45's w/ 17's, they think it greatly affects the gearing/overall drive of the wrx.........they say go w/ 40's

just another opinion i guess
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Old 02-10-2007, 10:52 AM   #8
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Quote:
Originally Posted by chimchimm5 View Post
I know they "will fit". But since the diameter of my wheel/tire would be increasing with the 225's, how bad is the effectively increased final drive? (or is that decreased?)
I thought you were an engineer? This is just simple math, should be right up your alley, man! It's just a matter of ratio-ing the tire diameters (or the "revs per mile" which are usually listed on Tire Rack.)

http://www.miata.net/garage/tirecalc.html

I don't the difference will be significant enough to notice.

Quote:
Originally Posted by NcKidd View Post
not to contradict above posters, but i spoke with Subydude last week about getting new 17x8 rims w/ 235/45/17's and they informed me that they dont recommend 45's w/ 17's, they think it greatly affects the gearing/overall drive of the wrx.........they say go w/ 40's
You realize that talking about "45's" and "40's" is pointless unless you also talk about the section width, right? A 235/45 and a 225/45 and a 215/45 all have different sidewall height and different diameters and would have different effects on gearing.

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Old 02-10-2007, 11:32 AM   #9
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Yea, that. Besides, try finding a 225/40 tire, anywhere.
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Old 02-10-2007, 12:17 PM   #10
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...and there are TOO MANY here that THINK---erroniously....that all the WRX's are the samecar

THEY ARE NOT THE SAME CAR

The 2.0's are weak....and can be 'helped' by using a 'shorter' tire.

the 2.5's are NOT weak...and do not NEED a shorter tire.

I wouldn't even THINK about buying anything but a 17x8(or 17x8.5) wheel for an '06+ and putting a 245/40 or even a 255/40 on it....the car can VERY easily overpower street 225/45's and there is no reason, for summer use, to use anything small on an '06+ WRX if you have the $$$ to buy the larger wheels and tires.
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Old 02-10-2007, 02:02 PM   #11
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Quote:
Originally Posted by Patrick Olsen View Post
I thought you were an engineer? This is just simple math, should be right up your alley, man! It's just a matter of ratio-ing the tire diameters (or the "revs per mile" which are usually listed on Tire Rack.)

http://www.miata.net/garage/tirecalc.html

I don't the difference will be significant enough to notice.
Yes, I did use that calculator. But as an engineer I know that there are lot of variables which are unknowns yet are significant; tire/wheel inertia, etc. Hard numbers are generally useless here at NASIOC. But the value is collecting many people's experiences evaluated according to their apparent experience level and applications.

On my previous car, I went from 14" steelies to 15" alloys and one up tires with marginally more weight and close overall diameter. The car bogged down enough to annoy me in the low end... something the tire size weight, wheel size weight, gear ratios, final drive, dyno chart, did not reveal. Nothing is black and white, ie bog or not, so the real value is getting the "feel" from other peoples experiences. Rating like "8.6 out of 10" are nearly useless, but reading the review reveals a lot when reviewer #1 says, "I never autox or track, but the s-tech makes the car feel so planted. Love em!" then reviewer #2 says, "after taking the s-techs to buttonwillow the suspension would bottom out due to the reduced travel and the soft rate made the car understeer horribly as it lost camber".

I'm looking for responses like this:

Quote:
Originally Posted by Uncle Scotty View Post
...no

...and if being here and reading ALL THESE POSTS didn't answer THAT question LONG AGO.....

I've long since written off Uncle Scotty as a grumpy old man who has had lots of great experience. So I take this one as +1 for 225 and I just laugh off the terseness.
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Old 02-10-2007, 02:05 PM   #12
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Quote:
Originally Posted by Uncle Scotty View Post
...and there are TOO MANY here that THINK---erroniously....that all the WRX's are the samecar

THEY ARE NOT THE SAME CAR

The 2.0's are weak....and can be 'helped' by using a 'shorter' tire.

the 2.5's are NOT weak...and do not NEED a shorter tire.

I wouldn't even THINK about buying anything but a 17x8(or 17x8.5) wheel for an '06+ and putting a 245/40 or even a 255/40 on it....the car can VERY easily overpower street 225/45's and there is no reason, for summer use, to use anything small on an '06+ WRX if you have the $$$ to buy the larger wheels and tires.
So what advice would you give a stage II 2.0l then?
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Old 02-11-2007, 12:34 AM   #13
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Originally Posted by REX8 View Post
So what advice would you give a stage II 2.0l then?
...still weak...a 'stage 2' 2.0 is a good laugh
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Old 02-11-2007, 12:53 AM   #14
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Quote:
Originally Posted by Uncle Scotty View Post
...still weak...a 'stage 2' 2.0 is a good laugh
They make the same low/mid range power/torque as a stock 06 and more high end power....so you'd have to recommend the same. Of course the modedd 2.0l is faster as well...

So your opinon would change on the tire recommendation on a stock 2.0l vs. a stage II 2.0l correct?

IMO, there's no reason not to push the same gearing advantage, even in the more powerful car. Sure it doesn't "need" it, but thats relative.

I swapped a set of 225 45 16's on an 06 for a day at Summit I co-drove. The shorter gearing on the 06 is VERY VERY nice as well.

Last edited by REX8; 02-11-2007 at 01:01 AM.
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Old 02-11-2007, 07:49 PM   #15
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Quote:
Originally Posted by chimchimm5 View Post
But as an engineer I know that there are lot of variables which are unknowns yet are significant; tire/wheel inertia, etc. Hard numbers are generally useless here at NASIOC. But the value is collecting many people's experiences evaluated according to their apparent experience level and applications.
I've been toggling between the stock wheel/tire setup for winter and '04 STi BBS/RE070 for summer. Nothing really registered on my butt dyno... and if it did, it would be of the same order as placebo effect.
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Old 02-12-2007, 03:20 AM   #16
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this thread make my head spin...

Uncle Scotty, you are saying that a (StgII) 250ish WHP 05 should NOT have 215+ width tires on 17inch rims?
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Old 02-12-2007, 07:41 AM   #17
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Originally Posted by Bbasso View Post
this thread make my head spin...

Uncle Scotty, you are saying that a (StgII) 250ish WHP 05 should NOT have 215+ width tires on 17inch rims?
He was talking about tire height. A bit shorter tire can help with the gearing to give a little extra grunt at low engine speeds. I don't think anyone has mentioned limiting yourself in width here.
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Old 02-12-2007, 07:57 AM   #18
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Quote:
Originally Posted by chimchimm5 View Post

IE, does it bog down the WRX?
Quote:
Originally Posted by waktasz View Post
There is only a 1.4% difference.
yes about 1.4%...

not a big diff at all.. especially for a 2.5, as others have mentioned.. will actually help things like fuel economy.. not much, maybe 1.4% or so

Quote:
Originally Posted by chimchimm5 View Post
Yes, I did use that calculator. But as an engineer I know that there are lot of variables which are unknowns yet are significant; tire/wheel inertia, etc. Hard numbers are generally useless here at NASIOC. But the value is collecting many people's experiences evaluated according to their apparent experience level and applications.

how many unknown variables are there when comparing a two slightly varying sizes of 17" tires? the OP has already mentioned that he is keeping the OE wheels.. so that sort of cuts out ALOT of variable eh?? its not like he's asking about a set of dub-duces??

although..

IF it were me.. I'd go
17x8 +48 wheels with a set of 245/40-17's

hell I've even reccommended that set-up to a couple 2.5i owners/friends of mine.
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Old 02-12-2007, 12:10 PM   #19
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Quote:
Originally Posted by waktasz View Post
He was talking about tire height. A bit shorter tire can help with the gearing to give a little extra grunt at low engine speeds. I don't think anyone has mentioned limiting yourself in width here.
Even with an OTS stage I map, a 2.0 matches a stock 2.5l in the lowend. So Scotty's advice wouldn't be applicable to a modded 2.0l.
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Old 02-12-2007, 12:11 PM   #20
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Quote:
Originally Posted by REX8 View Post
Even with an OTS stage I map, a 2.0 matches a stock 2.5l. So Scotty's advice wouldn't be applicable to a modded 2.0l.

Not that I agree anyway.

A gearing advantage is a gearing advantage, no matter what power level you are at.
...but STAYING in the gear longer.......with a taller tire does WHAT?????

especially if ya have more area under the curve.

and a 'stage2' 2.0 is NOTHING.......except in the head of the driver.
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Old 02-12-2007, 12:13 PM   #21
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Originally Posted by REX8 View Post
Even with an OTS stage I map, a 2.0 matches a stock 2.5l in the lowend. So Scotty's advice wouldn't be applicable to a modded 2.0l.
True but with more power you might want to stay in gear longer if the tradeoff in low end power is worth it to you. Since the 06 has better low end, it doesn't need the reduced gearing as much.


nano'd
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Old 02-12-2007, 01:06 PM   #22
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Originally Posted by Uncle Scotty View Post
...but STAYING in the gear longer.......with a taller tire does WHAT?????

especially if ya have more area under the curve.
Haha... see? NOW we are starting to get into discussing things I had ulterior motives for with my original post.
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Old 02-12-2007, 01:12 PM   #23
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Quote:
Originally Posted by Uncle Scotty View Post
...but STAYING in the gear longer.......with a taller tire does WHAT?????

especially if ya have more area under the curve.

and a 'stage2' 2.0 is NOTHING.......except in the head of the driver.
A stage II 2.0l HAS MORE AREA UNDER THE CURVE THAN A stock 06!!!

Yes, I understand that in a car with a broader torque curve, taller gears CAN BE advantageous. That is entirely dependent on what type of driving you are doing. Track days, 1/4 mile, etc.

You just can't make a blanket statement that longer gears will be good for all conditions. On a road course, where the shift time compared to total time on the throttle is VERY VERY little, shorter gears may/DO certainy help...in the 1/4, if it costs you an extra shift, they may not.

But again, this is not what we're talking about, as the 06 DOES NOT have a broader curve than a TBE/EM 2.0l
BTW: Post 19 was supposed to say II, not "I"

Last edited by REX8; 02-12-2007 at 01:23 PM.
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Old 02-12-2007, 01:13 PM   #24
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Quote:
Originally Posted by waktasz View Post
True but with more power you might want to stay in gear longer if the tradeoff in low end power is worth it to you. Since the 06 has better low end, it doesn't need the reduced gearing as much.


nano'd
No, the 06 doesn't have a better low end than a stage II 2.0l. Stock to stock, you're of course absolutely correct. And again, staying in gear longer as an advantage is entirely dependent on what conditions you are driving in.

Last edited by REX8; 02-12-2007 at 01:23 PM.
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Old 02-12-2007, 01:14 PM   #25
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Right off Cobb's website.

You would recommend shorter gears on the 2.0l ???? Please explain!

Last edited by REX8; 02-12-2007 at 01:23 PM.
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