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Old 07-27-2001, 09:40 PM   #1
SK00Impreza
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Default 48 offset compared to 53 offset

I'm trying to decide whether or not to get superleggeras with a 48 offset that are available now, or wait for the superleggeras specially made for the Impreza WRX available sometime in the future. I'm definitely not a wheel expert and don't know what the differences would be in the two, if any. Like would I notice any differences in handling for example between the two, 48 compared to 53? Insight would be greatly appreciated.
Thanks,
Scott

Sorry guys, I'm ALWAYS asking some type of question
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Old 07-27-2001, 10:53 PM   #2
wrxdriver
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Default need more info.

What types of tires are you going to be running? This can have an effect tread width difference of +/- 30mm even with 215/45 s between different brands and models (e.g. Bridgestone S-03 pps and Yoko A520s).

Are you going to be lowering the car as well? If so, how much? Who is going to be installing the setup?

What kind of driving will you be doing?

I'd recommend you collect as much of this info. and go to your favorite Subaru dealer or shop and get their recommendation on the whole package.

Ultimately they are going to be receiving your money, and requiring your total satisfaction.

As to whether ET48 fits on the WRX, that answer is yes, and Subaru Canada sell a BBS wheel with this offset in 17" x 7".
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Old 07-28-2001, 02:23 AM   #3
rbehny
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i think the guy is asking on a identical setup between the two wheels with probably daily driving and a little spirited what are the noticeable differences between et 48 and et 53.
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Old 07-28-2001, 02:25 AM   #4
Andrew
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you can slam the car down farther with a 53 than you can with a 48.
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Old 07-28-2001, 05:02 PM   #5
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Default Here's the facts

The difference between the 2 will be nominal because the wheel that OZ has rumoured to be attempting to build in the future is 8" wide and the current SuperL is 7" wide.

the math works out like this

8" wide wheel / 53mm offset
8" / 2 = 4
4 x 25.4 = 101.6
101.6+53 = 154.6
154.6 / 25.4 = 6.08"
8" wheel with 6.08" back spacing = 1.92" extension from the mounting surface towards outside of car

7" wide wheel / 48mm offset
7 / 2 = 3.5
3.5 x 25.4 = 88.9
88.9 + 48 = 136.9
136.9 / 25.4 = 5.38
7" wheel with a 5.38 back space = 1.62" extension from the mounting surface towards the outside of the car

As you can plainly see the differnece is only .3"

So, lowering the car could be completed more effectively with the 48mm offset wheel

Luke
877-522-8473 ext. 362

Last edited by Luke@tirerack; 07-28-2001 at 05:05 PM.
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Old 07-28-2001, 05:28 PM   #6
ThinkTank
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Default well.. ignore the math :)

I just installed 50mm offset on a 2002 Impreza and I dont have much clearance for lowering. I would go for the highest offset no matter what.

Compare a 7" and a 7" at 53 and 48
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Old 07-29-2001, 02:04 AM   #7
rbehny
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so things are even lets do it this way.

7" wide wheel / 48mm offset
7 / 2 = 3.5
3.5 x 25.4 = 88.9
88.9 + 48 = 136.9
136.9 / 25.4 = 5.38
7" wheel with a 5.38 back space = 1.62" extension from the mounting surface towards the outside of the car

7" wide wheel / 53mm offset
7 / 2 = 3.5
3.5 x 25.4 = 88.9
88.9 + 53 = 141.9
141.9/ 25.4 = 5.85
7" wheel with a 5.85 back space = 1.15" extension from the mounting surface towards the outside of the car

I don't know what all the figures mean but to me it looks as if the 7x53 is closer to the body than the 48 is. I'am presuming that closer is better.

Done my good deed for the day. heh
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Old 07-29-2001, 03:54 AM   #8
wrxdriver
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Default "better" ?

Better for what? May be better for clearance when "slamming down" or lowering, but not for overall handling where a wider track is better.

Run those same calculations with an 8" wide wheel and 53mm or 55mm offset, and I'd be very surprised if you weren't then rubbing on the inside strut or spring.
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Old 07-29-2001, 04:03 AM   #9
ThinkTank
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Default I add this link for clarity.

http://www.tirerack.com/wheels/tech/offset.htm Offset is the distance of the center mount of the wheel from the midline. Shaving the back of a 42mm offset wheel to 48mm gives you a larger offset and moves the wheel inboard. (for example)

Last edited by ThinkTank; 07-29-2001 at 04:15 AM.
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Old 07-29-2001, 04:13 AM   #10
rbehny
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8" wide wheel / 53mm offset
8" / 2 = 4
4 x 25.4 = 101.6
101.6+53 = 154.6
154.6 / 25.4 = 6.08"
8" wheel with 6.08" back spacing = 1.92" extension from the mounting surface towards outside of car

8" wide wheel / 48mm offset
8" / 2 = 4
4 x 25.4 = 101.6
101.6+48 = 149.6
149.6 / 25.4 = 5.88"
8" wheel with 5.88" back spacing = 2.12" extension from the mounting surface towards outside of car
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Old 07-29-2001, 04:52 AM   #11
wrxdriver
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Default 8" wide, 50s offsets??? I don't think so

So again, I do not believe you have the back spacing room to maintain 50s+ offsets with > 7" rims, look at the stock rim:

*****
stock 6.5" rim with 55 ET:

6.5" wide wheel / 55mm offset
6.5" / 2 = 3.25
3.25 x 25.4 = 82.55
82.55+55 = 137.55
137.55 / 25.4 = 5.41"

6.5" wheel with **5.41"** back spacing = 1.09" extension from the mounting surface towards outside of car

*****
7.5" wide wheel / 48mm offset
7.5 / 2 = 3.75
3.75 x 25.4 = 95.25
95.25 + 48 = 143.25
143.25 / 25.4 = 5.64"

7.5" wheel with a **5.64"** back space = 1.86" extension from the mounting surface towards the outside of the car

1/5" more back space than stock, probably OK, see STi wheel below.
*****

8" wide wheel / 53mm offset
8" / 2 = 4
4 x 25.4 = 101.6
101.6+53 = 154.6
154.6 / 25.4 = 6.08" !!!

8" wheel with **6.08"** back spacing! = 1.92" extension from the mounting surface towards outside of car

0.67" more back space than stock!!! Will this not rub on the inside? Does any vendor dare make a wheel like this?
*****

7" wide wheel / 48mm offset
7 / 2 = 3.5
3.5 x 25.4 = 88.9
88.9 + 48 = 136.9
136.9 / 25.4 = 5.38

7" wheel with a 5.38 back space = 1.62" extension from the mounting surface towards the outside of the car

7" 48 ET gives almost the same back spacing as stock, and reduces clearance towards outside of car only 0.53" more than stock.
*****

The 17"x7" with ET 48 actually comes closest to the stock rim with regards to back spacing room. I cannot imagine an 8" wide rim working at all without reducing ET into the 40s.


An actual wheel that is 17x7.5 ET 48:

http://www.rayswheels.co.jp/lineup/sti/rszero.htm

I do not know if this wheel works perfectly with a NA 02 WRX, one would hope so, and it probably would with the right combo of tires and suspension setup.
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Old 07-29-2001, 10:42 AM   #12
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Quote:
So again, I do not believe you have the back spacing room to maintain 50s+ offsets with > 7" rims, look at the stock rim:
wrxdriver - please read my theory/calculations/real life observations of my 18x7.5 ET53 wheels on a WRX sedan in this thread just 2 days ago:

http://i-club.com/forums/showthread....threadid=75599

My position is that you will not have any problem with 225 wide tires on a 7.5" or 8" wheel with 50-53 offset.
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Old 07-29-2001, 01:35 PM   #13
wrxdriver
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Default read the thread

Rick,
I read up on your thread, and it is good info. I'm glad your P1 18x7.5 ET 51 setup with 225/40/18 S03s are working.

I do believe you have a tight fit though, 13mm is not a lot of space, measured static.

Also, your choice of tires may be a critical factor. Note that the specs for say Michelin Pilot Sports (OEM on Porsches) for 225/40/18 have an 8.9" tread width on an 8" rim while the S03s on an 8" rim have an 8.3" tread width.

So I believe that with certain tire makes to maintain even that 13mm, you might need to go to 225/35 or 215/40 or something lesser than 225/40 though you're lucky, you picked a good tire, and it fits.

A non S03 225/40/18 could reduce that 13mm to less than half or getting into the sub 1/4" static free space between tire and strut. Now you're also saying this offset would be OK with 8" wide wheels, well how would that could put the tire right at the strut.

At some point, you have to fish and cut bait, and extend the width out the fender side, take a look at some modified racing cars with flared fenders, you don't want to keep narrowing your track, or you'll end up with a backwards 3 wheel car that they drive in Europe.

So are there any 8" wide Subaru wheels with > 50 ET? I personally think it would be foolish given the tightness of 7.5" at 51 with your provided measurements.

I think you're running very tight in your inside wheel wells.

Read Jeffg's messages on that thread, he's basically saying the same thing, that at 8" wide, ET45 of so is safer.
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Old 07-29-2001, 02:42 PM   #14
ThinkTank
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Default 1/2 inch is huge if you are

reducing the space between the fender and outside edge of wheel. There wasn't much space with the stock wheels if you lowered the car.

Last edited by ThinkTank; 07-29-2001 at 04:50 PM.
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Old 07-29-2001, 11:00 PM   #15
Joe Hogan
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You also might want to watch the tire strut clearence. 8" rims will be happier with 48mm offset because you gain some space between the strut and tire. Atleast this is the case on a RS.

Joe
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Old 07-30-2001, 07:24 PM   #16
SK00Impreza
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Default Hmmmm...

So how much would I be able to lower my car with the Superleggs? I already ordered H&R's so I hope this will be an ok combination. The H&R's lower the car about 1.5 inches. Thank you all for the VERY in-depth information.

Scott
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Old 07-30-2001, 09:47 PM   #17
ThinkTank
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Default I was told

H&R lowered 1.7"
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Old 07-31-2001, 08:55 AM   #18
Luke@tirerack
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At this time we do not even offer an 8" wheel for Subaru's and now you know why.
To explain the numbers:
25.4 is a metric conversion calculation

Luke
877-522-8473 ext. 362
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Old 07-31-2001, 10:02 PM   #19
Patrick Olsen
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Default

Quote:
I do believe you have a tight fit though, 13mm is not a lot of space, measured static.
Bah! 13mm is tons of space. On my race wheels/tires, I have probably 2mm clearance, maybe 3mm at the very most, between the tire and the strut and the tire and the spring seat (DMS coil-overs). Clearance on my street tires is slightly greater, but definitely less than 1/2" (13mm). I have yet to experience any rubbing of any sort on the street, auto-crossing, or at the track. If your tires are flexing by 1/2", you need to get real tires that actually have a sidewall.

As for the offset/backspacing calculations, the numbers calculated above are nice for comparison's sake, but they were all done improperly. The advertised rim width is not the same as the actual rim width (because of the lip on each side of the wheel). A wheel that is advertised as 17x7" is going to be somewhere around 8" wide overall, give or take 1/4". My 15x7" Racelines are actually 7 3/4" (I think) wide edge-to-edge. My 16x6.5" 2.5GT wheels are 7 3/8" wide or something like that (it was sometime last fall that I checked this out, so my numbers very well may be off). Edit: The more I think about it, I seem to recall the 2.5GT rims were 7 5/8" wide and the Racelines were 7 7/8" wide - one was just over 1" wider than advertised, and one was just under 1" wider. Anyway, keeping that added wheel width in mind, the correct way to convert from offset to backspacing is to add 1" to the advertised wheel width. Hence the backspacing on a 17x7.5" +48mm wheel would be (7.5" + 1")/2 + (48mm/25.4mm/in) = 6.14" rather than 5.64".

Again, even that number won't be perfect, since the lip size is different depending on the wheel. I'd be willing to bet, though, that if anyone takes off a WRX wheel, for instance, and measures backspacing (just put a 16" straight edge across the back edge of the wheel and measure to the mounting face) they'll get something closer to 5.92" rather than 5.41". Anyway, it's all moot, since the same 0.5" error was introduced into all the calculations done by various people above, so the comparisons are still valid. I'm just an anal bastard.

Pat Olsen
'97 Legacy 2.5GT sedan

Last edited by Patrick Olsen; 07-31-2001 at 10:05 PM.
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