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      01-20-2017, 01:44 PM   #23
SlipperyGary
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I haven't changed tires yet, so I don't have any personal experience with different tire widths, but I'm pretty sure I've read that people are running 245's up front and 285's in the rear on the stock rims without problems.
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      01-20-2017, 04:44 PM   #24
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if the tires are changed to 245 front and 285 back - what the tyre profile to be used? is it 30 or 35? will it affect the actual speedometer?
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      01-23-2017, 10:54 AM   #25
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Quote:
Originally Posted by greddyuk View Post
if the tires are changed to 245 front and 285 back - what the tyre profile to be used? is it 30 or 35? will it affect the actual speedometer?
Here's a comparison.





You can do additional comparisons at, https://tiresize.com/comparison/
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      01-23-2017, 03:18 PM   #26
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Thanks for letting me know. Definitely something I will look into when I change the rubbers. Let me know how you get on with your change of tyre widths.
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      01-23-2017, 06:57 PM   #27
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Quote:
Originally Posted by greddyuk View Post
if the tires are changed to 245 front and 285 back - what the tyre profile to be used? is it 30 or 35? will it affect the actual speedometer?
285/35/20
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      01-23-2017, 07:01 PM   #28
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Quote:
Originally Posted by SlipperyGary View Post
Here's a comparison.





You can do additional comparisons at, https://tiresize.com/comparison/
Isn't OEM supposed to be "Size 1" in the comparator?
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      01-24-2017, 09:12 AM   #29
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I didn't realize there was a standard for which to put first when comparing tire sizes. I put the stock size as "Size 2" in both comparisons.
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      01-24-2017, 10:13 AM   #30
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Front 27.61
Rear 27.71

Width x 0.Side x 2 / 25.4 + rim size

245x0.40=98x2=196/25.4=7.71+20=27.71
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      01-24-2017, 10:33 AM   #31
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a better wheel/tire size calculator with a more graphic approach:

http://www.willtheyfit.com/
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      01-24-2017, 12:50 PM   #32
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Quote:
Originally Posted by SlipperyGary View Post
Here's a comparison.





You can do additional comparisons at, https://tiresize.com/comparison/
The 245/40R30 for the front is outside the recommended rim width of the OEM front rim. Rim width recommendation for that size is no less than 8". The front OEM rims are 7.5" wide.

My guess is that it would work, but I am uncertain

Shawn
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      01-24-2017, 02:08 PM   #33
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Not sure if anybody knows the answer to this but if you look at the diagrams above and you see the diameter for Size 1 and Size 2 and then % diameter difference.

If going to non-OEM tires like we all are discussing, do front and rear tire both have to be -% or -% (or +% and +%) or can front/rear can be -% and +%? The reason why I ask is because the % diameter difference plays a huge role in speedometer accuracy. If the front has a -% and the rear has a +% (or vice versa), does that cause an issue?

EDIT: For Example. If you go to a front 235/40/20, it is a -0.7% diameter difference than front OEM. So the speedometer will read slower than OEM. But if you put rear 255/40/20, it is a +1.1% diameter difference which means the speedometer will be faster than OEM.

Last edited by Ghetto2315; 01-24-2017 at 02:26 PM.
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      01-25-2017, 04:30 AM   #34
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Quote:
Originally Posted by Ghetto2315 View Post
Not sure if anybody knows the answer to this but if you look at the diagrams above and you see the diameter for Size 1 and Size 2 and then % diameter difference.

If going to non-OEM tires like we all are discussing, do front and rear tire both have to be -% or -% (or +% and +%) or can front/rear can be -% and +%? The reason why I ask is because the % diameter difference plays a huge role in speedometer accuracy. If the front has a -% and the rear has a +% (or vice versa), does that cause an issue?

EDIT: For Example. If you go to a front 235/40/20, it is a -0.7% diameter difference than front OEM. So the speedometer will read slower than OEM. But if you put rear 255/40/20, it is a +1.1% diameter difference which means the speedometer will be faster than OEM.
Depends on there the speedo is driven from but I would expect a sensor on one of the rear uprights or from the ICE gearbox.

So the rear tyre is the important one. And going slightly larger is no bad thing as it will fix the flight speedo over read.
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      01-25-2017, 08:10 AM   #35
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I wouldn't get too hung up on it - I read somewhere that a couple of % shouldn't be an issue (not sure if there was proper maths behind it though).
Your tyre/tire diameter fluctuates anyway presumably with pressure changes, thermal changes and tread wear over time.

What's the tread depth on new tyres/tires? Is it about 10mm and down to 3mm when worn, so you've got a 7mm variance over the life of the rubber anyway.
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      01-25-2017, 08:14 AM   #36
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Quote:
Originally Posted by NGR View Post
I wouldn't get too hung up on it - I read somewhere that a couple of % shouldn't be an issue (not sure if there was proper maths behind it though).
Your tyre/tire diameter fluctuates anyway presumably with pressure changes, thermal changes and tread wear over time.

What's the tread depth on new tyres/tires? Is it about 10mm and down to 3mm when worn, so you've got a 7mm variance over the life of the rubber anyway.
Agree!

And, tires by different manufacturers with the same specifications will have slightly different widths and diameters. Don't sweat the small differences.
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      02-05-2017, 05:19 PM   #37
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Does anyone by any chance know the offsets for the front and rear OEM wheels? (W style, not the turbines).

I was talking with a wheel shop and for their wheels they recommended the following:

Front:
245/40/20 with a 34mm ET offset (20x9)

Rear
275/35/20 with a 45mm ET offset (20x10)

Will these sit flush or poke out at all?
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      02-05-2017, 05:46 PM   #38
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2016 BMW i8  [5.00]
Quote:
Originally Posted by Emon Crew View Post
Does anyone by any chance know the offsets for the front and rear OEM wheels? (W style, not the turbines).

I was talking with a wheel shop and for their wheels they recommended the following:

Front:
245/40/20 with a 34mm ET offset (20x9)

Rear
275/35/20 with a 45mm ET offset (20x10)

Will these sit flush or poke out at all?
Searching sucks on mobile. I posted the stock offsets in a thread I started awhile ago. Those seem okay. You can use a comparison site to confirm the difference from stock.
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      02-06-2017, 10:36 AM   #39
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Quote:
Originally Posted by Emon Crew View Post
Does anyone by any chance know the offsets for the front and rear OEM wheels? (W style, not the turbines).

I was talking with a wheel shop and for their wheels they recommended the following:

Front:
245/40/20 with a 34mm ET offset (20x9)

Rear
275/35/20 with a 45mm ET offset (20x10)

Will these sit flush or poke out at all?
they will seat flush a little poke on the rear (very little)

The stocks are 20x7.5 Et +40 & 20x8.5 Et +50
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      02-13-2017, 02:21 AM   #40
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Quote:
Originally Posted by Amgeater2 View Post
they will seat flush a little poke on the rear (very little)

The stocks are 20x7.5 Et +40 & 20x8.5 Et +50
What offset do you think should have the rears sitting flush? Closer to ET50 with a 275/35/20 (20x10") setup? I'm about to pull the trigger on the wheels tomorrow and want to make sure that the wheels engineers have the right measurements for a flush seated wheel.
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      02-13-2017, 11:17 AM   #41
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Quote:
Originally Posted by Emon Crew View Post
What offset do you think should have the rears sitting flush? Closer to ET50 with a 275/35/20 (20x10") setup? I'm about to pull the trigger on the wheels tomorrow and want to make sure that the wheels engineers have the right measurements for a flush seated wheel.
Yeah anything from 45-50 you will be fine brother post some pics after the install
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      02-13-2017, 07:49 PM   #42
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Quote:
Originally Posted by Amgeater2 View Post
Yeah anything from 45-50 you will be fine brother post some pics after the install
Thanks Amgeater! I'm inclined to go more towards a 48mm offset based on willtheyfit.com showing the inner barrel being 19mm closer to the suspension strut and only poking outwards 19mm.

I'm planning on doing a wrap and putting the wheels on, will definitely post pictures. Build time is estimated at 7-10 weeks
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      02-14-2017, 04:03 PM   #43
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Still wondering if anyone has put different size tires on the stock wheels. If so, what has been your experience? Good, bad, indifferent?
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      02-14-2017, 04:52 PM   #44
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Quote:
Originally Posted by SlipperyGary View Post
Still wondering if anyone has put different size tires on the stock wheels. If so, what has been your experience? Good, bad, indifferent?
yes a fellow member did 275 and 245 on the stock wheels
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