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      06-25-2020, 05:34 AM   #1
nolumih
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rear tires 275/35/20 or 265/35/20

Good morning all. I would like to increase the size of the rear tires and go to 275/35/20 or 265/35/20. I would like to have feedback from those who did it and why they chose one or the other.

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      06-25-2020, 09:14 AM   #2
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245/40x20 on the front and 275/35x20 on the rear with the stock wheels fit fine. No clearance issues. This set up also keeps the diameter almost exactly the same as original.
There are also many more tire choices in these sizes.
Going with the 265 will give you a smaller diameter tire than originally installed and more speedometer error.

All of these tire sizes including the 265’s are slightly wider than the tire manufacturers recommend installing on the narrow stock i8 wheels.

https://tiresize.com/comparison/

Last edited by Coastali8; 06-25-2020 at 11:43 AM..
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      06-25-2020, 12:00 PM   #3
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I changed fronts and rears. A major concern for me is weight. 245/40 on the fronts adds 4 lbs per wheel! Likewise 275/35 on rear. That is like trying to sprint in work boots. So I went with 235/40 front and 265/35 on rear, tiny diameter difference, weight almost balanced out by using titanium lugs.

In my experience reducing unsprung weight is one of the best performance mods you can make.
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      06-25-2020, 04:33 PM   #4
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Interesting point. True that unsprung weight is very important. Adding 3-4 pounds of extra tire weight per wheel total 12 pounds at a supposedly 3.47 to 1 ratio amounts to adding around 41 pounds of sprung weight. But....another way to look at it is the additional tire contact with the road may increase your ability to travel faster through the curves. On the other hand... lighter wheels/ tires generally improve the ride. Although.... if your going to drag race your i8, the extra unsprung weight may add 1/10 second. But....I don’t see many high performance cars with skinny tires. Lots to consider. Ultimately.... fat tires look cooler.

Last edited by Coastali8; 06-26-2020 at 12:02 AM..
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      06-25-2020, 06:37 PM   #5
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I don't think you could see any noticeable difference between 275 and 265, or 245 and 235. Some 245/40 tires will not fit up front, so one needs to be careful there.

Wider tires do not necessarily have more contact, and certainly do not always enhance cornering or handling on stock vehicles - TireRack has some great tests. In general lower profile, wider tires have a small, positive effect on cornering. In the case of the i8, I think there is a significant effect on performance, because tire choice by BMW was slanted towards fuel economy.
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      06-26-2020, 05:51 AM   #6
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Thank you for your feedbacks. The skinny tires are just to be able to lower CO2 emissions below 50 gr / km. Very important thing on Europe.

The question I ask is whether the 275 with rim flange protection goes or not? In front, actually I think a 235 is wiser.

As for the brand, Continental Conti-PremiumContact seems to be according to German tests the best choice in summer tires.

Last edited by nolumih; 06-26-2020 at 05:58 AM..
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      06-26-2020, 12:41 PM   #7
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I have a set of 245 and 275 on order.
Will let you know next week what it is like.

I went for pilot 4S
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      07-04-2020, 08:42 AM   #8
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Works like a charm
Handling is better
Heavier steering
More road nose and header ride.


Happy over all.
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      07-05-2020, 02:37 AM   #9
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Has anyone tried using the wider original wheels on the front to give a 'natural' seating for the 245's? Given that this is a 4wd car too I do wonder how the car would behave on 245's all round, the Audi performance quattro models (RS3, RS4, RS5 TT RS) use the same profile front and rear after all, and those with similar performance (RS3 and TT RS) actually use 245's and grip like mad!
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      07-06-2020, 05:02 AM   #10
nolumih
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Quote:
Originally Posted by DocDoc View Post
Works like a charm
Handling is better
Heavier steering
More road nose and header ride.


Happy over all.
Thanks Doc for the feedback.
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      10-30-2020, 01:16 PM   #11
nolumih
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Runflat ?
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