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The Tire Rack's Tire & Wheel Forum
Use this forum to discuss anything in relation to wheels to tires to offsets.
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Old 04-03-2017, 10:38 PM   #1
hawk99
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Join Date: Apr 2006
Location: Victoria
Posts: 252
My Ride: 323ci
Wheel Spacers with Style 68 Staggered....

Hi All,

I have a 2000 323ci convertible, with standard sport suspension, and 17'' staggered style 68's with 225/45 on the front and 245/40 tires on the back.

I have done the measurements, but I would like to see if anyone else has my setup and has already added spacers to be sure. The local dealer that sells spacers doesn't have the test fitment kit.

From some research I have seen 15mm in front, and 20mm in rear. Can anybody confirm?

What is the Max spacers (front and rear) I can fit with this set up?

Thanks guys!
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Old 04-04-2017, 06:52 AM   #2
abyzzim
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Join Date: Mar 2015
Location: Thailand
Posts: 77
My Ride: '03 318i Sedan
According to my guesstimates, judging from my style 193 (rears) 18x8.5j ET+37 in the front and back of my 2002 sedan, I can imagine installing a 10 mm spacer in there and it would still fit fine on my car (on stock ride height). Therefore, with a 10 mm spacer, the effective offset would be ET+27.

Now I calculated using the wheel offset calculator (search google for it), and used a 25 mm spacer for the fronts of the 68's (17x7.5j ET+41), which would mean that the effective ET will be ET+16, and compared with my Style 193's (18x8.5j ET+27 <<< with 10 mm spacers), and the results are: 24 mm more inner clearance than my Style 193 (rears) in the fronts, and the wheel will retract by 2 mm (so it would probably not rub on the fenders).

The rears should be alright too. I used the wheel offset calculator, and used a 25 mm spacer for the rears of the 68's (17x8.5j ET+50), which moves the effective ET to ET+25, and compared with my Style 193's (18x8.5j ET+27 <<< with 10mm spacers), and the results are: 2 mm more inner clearance than my Style 193 (rears) in the rears, and the wheel will extend by 2 mm (so it would probably not rub on the fenders).

Even though I did my calculations based on my stock ride height, I can imagine that dropping the car by 1" or so would still be fine without the need to roll fenders, even with 25 mm spacers.

ps. However, with 25 mm spacers, you will end up with a lot more (too much) positive scrub radius in the front, because, according to my calculations, the ideal offset for a 7.5j wheel is ET+41. Subtract 41 mm and 16 mm and you get 25 mm, which means you will gain a +25 mm of scrub radius (which I think is a lot).

I wrote down a comment explaining this to someone in Engineering Explained's video about "Benefit of Wheel Spacers On A Subaru BRZ":

"To measure change in scrub radius, you should start with the base model for each car (so that it has the narrowest wheels) and calculate up. For example, if a base model has 7j wheels and an offset of ET+47, what would be the offset that would retain the same scrub radius if the wheel width were increased to 7.5j? The answer is for 7.5j wheels, the offset to use is ET+41. How did the +6 offset come about? So if you increase wheel width by 0.5j with the same offset (ET+47), the tire centerline moves inwards by 6.35mm (which I will round dowm to 6mm for simplicity). I calculated by changing 7 inches into 177.8 mm and 7.5 inches into 190.5 mm, and dividing those two widths by half equals 88.9 mm being the centerline for 7j wheels, and 95.25 mm being the centerline for 7.5j wheels; next, subtract 95.25 by 88.9, and you get 6.35 mm. Therefore, a +6 mm of offset is necessary to rebalance the tire centerline.

Now if you drastically increase wheel width to something like 9j, you will need an offset of ET+23 to keep the same scrub radius."

So, with a more positive scrub radius, one disadvantage is you will probably end up with more bump steer, which could be dangerous depending on the situation. Also, you might get a bit more tire wear and wheel hub-bearing wear as well. Braking and accelerating will also result in more degrees of toe-out as opposed to the stock setup's mildly positive scrub radius.
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Last edited by abyzzim; 04-05-2017 at 12:37 PM. Reason: adding more info
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Old 04-21-2017, 02:20 AM   #3
Dirtymyk
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Join Date: Dec 2016
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My Ride: 330i
15mm up front 12 in the rear
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Old 04-21-2017, 05:14 PM   #4
abyzzim
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Quote:
Originally Posted by Dirtymyk View Post
15mm up front 12 in the rear
Looks good man! How does she drive? How's the steering weight compared to before the spacer-installation? How's the bump steer?

(You have an effective offset of 41-15=26mm in the front on 7.5j wheels and 50-12=38mm in the rear on 8.5j wheels.)
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Old 04-22-2017, 05:05 AM   #5
Dirtymyk
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***128519;***128519;***128519;

Drives awesome! Forgot about the added benefits of wider track width...definitely feels better in the canyons...less understeer. More neutral in steering. I barely feel it when parallel parking...then again I rock climb 2x a week so my grip strength is abmormal...and had an e30 on 15x8 and no power steering prior to e46.
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Old 04-22-2017, 08:10 AM   #6
abyzzim
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Quote:
Originally Posted by Dirtymyk View Post
Drives awesome! Forgot about the added benefits of wider track width...definitely feels better in the canyons...less understeer. More neutral in steering. I barely feel it when parallel parking...then again I rock climb 2x a week so my grip strength is abmormal...and had an e30 on 15x8 and no power steering prior to e46.
I see; that's great to hear!
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Old 04-22-2017, 07:56 PM   #7
dsm2002
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My Ride: BMW 330i, 2002 & E30
Quote:
Originally Posted by Dirtymyk View Post
15mm up front 12 in the rear
what tyre size?
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