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      01-03-2019, 10:27 AM   #1
MGRMLN
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Run Rears in the front?

Has anyone run another set of rear wheels/tires on the front?
I'm currently running a square 245/40-20 setup but was curious.
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      01-03-2019, 10:59 AM   #2
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Quote:
Originally Posted by MGRMLN View Post
Has anyone run another set of rear wheels/tires on the front?
I'm currently running a square 245/40-20 setup but was curious.
Aren't the 245/40-20's the stock rear tire? If you are running them square, then aren't you already doing that?

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      01-04-2019, 06:57 AM   #3
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I think the OP meant "can you run 245s at all four corners?"
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      01-04-2019, 12:07 PM   #4
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Originally Posted by KAMF View Post
I think the OP meant "can you run 245s at all four corners?"
Do we all understand what a "Square Setup" is?

If he accurately said: "I'm currently running a square 245/40-20 setup..." Then he is already running 245's all around...

Running a "square setup" specifically means you have four IDENTICAL tires on your car. A "staggered setup" is when the fronts are different sizes (typically narrower) than the rear (typically wider)...

I specifically run a "square setup" on my M4 track car so I can rotate the fronts to the rears (and vice versa) to balance tire wear (mostly front outside shoulder wear). This is why racers very often run a "square setup". A staggered setup typically provides marginally better performance but a square setup provides significantly better economy...

Last edited by evanevery; 01-04-2019 at 12:13 PM..
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      01-04-2019, 03:47 PM   #5
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Quote:
Originally Posted by MGRMLN View Post
Has anyone run another set of rear wheels/tires on the front?
I'm currently running a square 245/40-20 setup but was curious.
That is not what the OP is asking. He wants to know if anyone is running “rear wheels/ tires on the front”

He is asking if 8 1/2 inch rear wheels and 245/40- 20 tires has ever been put on the front. He is not asking if 245/40-20 tires have been put on the 7 1/2 inch front wheels.

Seems like a valid question. 8 1/2 inch wheels on all four corners? Unfortunately it won’t work with the stock rear wheels placed on the front of the car because of the offset. You would really have a huge clearance problem as the wheel/tire assembly would move out towards the fender by about 1/2 inch plus the wider tire would probably make everything outside of the fender.

Tire manufacturers don’t recommend 245/40’s on a 7 1/2 inch wide wheel.
Nor do they recommend 275/35’s on an 8 1/2 inch wide wheel as has been suggested in another thread.

235’s on the front and 255’s on the rear are as wide as we should go on the stock wheels. Problem is.... there are no good tire choices in those sizes that I’ve been able to find.

Last edited by Coastal i8; 01-04-2019 at 04:14 PM..
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      01-04-2019, 03:58 PM   #6
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A "Square Setup" implies running the same Tires AND Wheels on all four corners. If you are running different wheels front/rear then it isn't truly a square setup as the tires/wheels wouldn't be fully interchangeable (even if they fit)...

So back to "Square One"... :-)

"Anyone tried running the factory rears (wheels/tires) on the front?"

You got a wrench?

Last edited by evanevery; 01-04-2019 at 04:12 PM..
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      01-04-2019, 04:31 PM   #7
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Yep.
A wrench and 10 minutes would answer everything.
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      01-06-2019, 08:03 PM   #8
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Thanks for the lively discussion.
I am in fact running 245/40-20’s on front and back.
I added 5 mm spacers all around to get the insides of the front tires just a bit further from the upper arm and for better appearance. Stock, I think the i8 tires look too “tucked in” but that’s common to almost all cars these days to me.

It seems to me that running another set of rears, in the front would essentially look like running a 10mm spacer right?
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      01-06-2019, 08:31 PM   #9
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After much confusion, the OP basically wants to know if you can run the factory rear wheels/tires on the front...

The issue is the wheels, not the tires (or the tire sizes). Everyone seems to agree that the rear tires will work if installed on the front wheels. The question is whether the rear wheels will work (with those tires).

The rear wheels are wider than the fronts but they also have different offsets (so their effective/proportional centerlines might also be meaningfully different)

There are several different tire/wheel combos for the i8. My friends at iND gave me this link:

https://www.etkbmw.com/bmw/EN/search...i8/USA/36_2467

Note that not only do the wheel sizes vary but also the offsets. Take the first listed example: If a wheel width increased by a half an inch (12.5 mm), and the offset increased by 10mm, then most of that increase in width was pushed into the wheel well. Just because a wheel design is increased in width doesn't mean it happens symmetrically in both directions (inward/outward). Offsets matter.
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      01-07-2019, 03:14 PM   #10
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Quote:
Originally Posted by evanevery View Post
After much confusion, the OP basically wants to know if you can run the factory rear wheels/tires on the front...

The issue is the wheels, not the tires (or the tire sizes). Everyone seems to agree that the rear tires will work if installed on the front wheels. The question is whether the rear wheels will work (with those tires).

The rear wheels are wider than the fronts but they also have different offsets (so their effective/proportional centerlines might also be meaningfully different)

There are several different tire/wheel combos for the i8. My friends at iND gave me this link:

https://www.etkbmw.com/bmw/EN/search...i8/USA/36_2467

Note that not only do the wheel sizes vary but also the offsets. Take the first listed example: If a wheel width increased by a half an inch (12.5 mm), and the offset increased by 10mm, then most of that increase in width was pushed into the wheel well. Just because a wheel design is increased in width doesn't mean it happens symmetrically in both directions (inward/outward). Offsets matter.
Thank you!
I will stay my current setup.
I appreciate the help!
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      01-07-2019, 03:45 PM   #11
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Quote:
Originally Posted by MGRMLN View Post
Thank you!
I will stay my current setup.
I appreciate the help!
I sure don't feel like I answered your question though... Maybe just made things more confusing...

Doesn't mean the extra considerations aren't real though!

I still think your best bet is to just grab a wrench and see for sure. Tip the car up on one side, take the front wheel off and move the rear to the front. You don't even need to remount the front (on the back) to preliminarily check the front suspension clearance.

If the one rear wheel physically appears to fit when on the jack stands, then finish the job (swapping fronts/rears). Take her out and drive her in circles (lock to lock each way). If that checks out, you pretty much have your answer (suspension travel complications not withstanding). You will probably want to swap everything back though as I doubt you want to leave your fronts on the back...
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      02-03-2019, 11:13 PM   #12
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Resolution to the story.
So I’m now running 245/40-20 tires up front, just like the rears.
Understeer, totally gone. Running 3mm spacers, just to ensure adequate clearance to the front uprights.

I also made a switch to titanium lug bolts at the same time and I love how strong and light they are!

Counteracts the heavier tires so overall less unsprung weight!
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      02-04-2019, 04:30 AM   #13
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Quote:
Originally Posted by MGRMLN View Post
Resolution to the story.
So I'm now running 245/40-20 tires up front, just like the rears.
Understeer, totally gone. Running 3mm spacers, just to ensure adequate clearance to the front uprights.

I also made a switch to titanium lug bolts at the same time and I love how strong and light they are!

Counteracts the heavier tires so overall less unsprung weight!
So is that 245mm tyres fitted to the smaller front wheel? Have you noticed any improvement in traction with the fronts in edrive mode? Mine slip like crazy if I have a remotely heavy right foot.
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      02-05-2019, 09:51 AM   #14
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So are you running these square, or just the larger tires on the narrower stock front wheels?
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      02-07-2019, 01:02 PM   #15
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Quote:
Originally Posted by MajorJump View Post
So is that 245mm tyres fitted to the smaller front wheel? Have you noticed any improvement in traction with the fronts in edrive mode? Mine slip like crazy if I have a remotely heavy right foot.
I have so much more traction and the handling is transformed. I was very unhappy with the amount of understeer with the factory sizes. Mounting 245/40-20 on the stock front wheels has resulted in much better turn in, front end grip and neutral handling. I love it.
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      02-08-2019, 10:40 AM   #16
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Quote:
Originally Posted by MGRMLN View Post
Quote:
Originally Posted by MajorJump View Post
So is that 245mm tyres fitted to the smaller front wheel? Have you noticed any improvement in traction with the fronts in edrive mode? Mine slip like crazy if I have a remotely heavy right foot.
I have so much more traction and the handling is transformed. I was very unhappy with the amount of understeer with the factory sizes. Mounting 245/40-20 on the stock front wheels has resulted in much better turn in, front end grip and neutral handling. I love it.
I've got 245s on the std front wheels and 275s on the std rears.

Grip is better at the front but the over-aggressive traction control still spoils fast pullaways in electric mode. You can still easily spin the fronts but it is better.

No fouling anywhere and they look nice on the rims. Had them on for about 8000 miles.

But of extra protection from the kerbs too.
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      02-09-2019, 02:35 PM   #17
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So no spacers needed then? That's great news, I think I've got about 6 months left on my summer tyres so I can go up a size next time around.
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