Tapered 18" rims for e70

[byaru1]

Originally Posted by andrewwynn

...

How about for taller sidewall, I do:

Front: 255/60R19
Rear: 275/55R19

I'm hoping it wouldn't touch the suspension parts especially at full turn, given it's not a huge change?

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[andrewwynn]

That size is tall enough to throw off your speed as shown. Where original size you're going 77 at 80 on speedometer, that size you'll be going 82.5.

That will also be enough to lose some acceleration and cornering will be noticably softer with more body roll (which will be a trade off anyhow to achieve your goal using tires vs. spring/shock)

[byaru1]

Originally Posted by andrewwynn

That size is tall enough to throw off your speed as shown. Where original size you're going 77 at 80 on speedometer, that size you'll be going 82.5.

That will also be enough to lose some acceleration and cornering will be noticably softer with more body roll (which will be a trade off anyhow to achieve your goal using tires vs. spring/shock)

Thank you.

How about rubbing on suspension parts, is the clearance enough to not rub?

I don't mind a little body roll, I'm willing to trade that for extra rubber and sidewall within reasonable safety provision.

Acceleration... Well the 3.0si is already a donkey, I'm used to it. What's the worst that could happen

[andrewwynn]

I found this from an old x-drive manual. Though the original setup has the rears 0.3% smaller, I would be ok with starting 0.7% bigger as the rears tend to wear faster anyhow if you use your throttle heavy (on our 50i, it's very noticable).

Also why I would prob switch to a square setup.

I'm prob going to a square 275/50/18.

E70 M has up to 285 fronts so I'm not concerned about 275s clearing body/suspension.


You can see the size I'm aiming for is nearly identical to the biggest tire BMW puts on the front.

In my case by going from 255 > 275 up front I will likely bias the car a little more towards oversteer, but likely not enough to actually make it oversteer. Something I've only seen a couple times on slippery surfaces.

[andrewwynn]

As I mentioned out next set will most likely be 275s square setup (as it's basically impossible to get a staggered set in 18s and I'm not buying new rims already have two sets of 18s).

That said above is before/after comparison of the front if you go to 275 square.

2.8% bigger means your speedo will be a good amount more accurate.


At 75 on the dash you'll be going 74 vs. 72. (also it won't read wrong "low" until 107

The ability to rotate tires and the fact you are willing to trade cornering for comfort, I think you'd be very happy with a square setup on 275s.

It should definitely feel different but prob no more different than my e53 with sport suspension and wife's e70 without. We both have 255/55/18 and she has the 50i which begs the question: if BMW put 315s on the 4.8 WTF putting 255s on the 50i! (The tires break free at pretty much every shift at full throttle). The rear tires are wearing much faster than the front. Even when we bump up to 275s I expect that to happen why I don't want to switch to stagger setup.

I just realized the caveat in your case. You may have staggered rims!

If you have 9/10 rims which is not uncommon, you can't really rotate and means might as well use a staggered set.

[andrewwynn]

To test for clearance put your rears on the front and see if the 285s fit.

255/60s might be a bit overzealous for making the tire a full 2" taller, I would start to be concerned with contact with the fender well.

Wife's 50i handles perfectly "ok" with square setup 255/55/18 so with your mindset of ok to trade comfort for handling I wouldn't worry at all about upsetting the delicate balance of handling.


One more square setup to consider.

265/55 will get you 14% more sidewall, 5.2% bigger.


With that size your speedo will be off 1mph low at 75 (actual speed 76) but will be spot on at 57.

(The green line is original tires actual speed, black line is speedometer speed)

That option is your max comfort option and the X5 has very large wheel wells I don't think you will have any concerns about making contact.

[andrewwynn]

As far as performance goes, BMW changed the diff from 3.91 to 4.1 for the 3.0 which is 4.1/3.91=1.049 to help out off the line. You'll definitely feel three difference but again comfort vs. performance.

At 2.8% bigger tires, that makes 200 ft·lb become 200/1.028=194.553

With 5.2% bigger tires:
200/1.052=190.114.

6 or 10 ft·lb loss. It's something a racer would be concerned about, I doubt you would.

[bcredliner]

Continental Extreme Contacts have the softer sidewalls you are looking for. They are also a quiet tire. The tread rating is still hard enough that the tires last longer than most. You will have more rollover so turn in will be compromised a little but they are an option to consider if they make the size you want. The pricing is lower as it relates to other premium brands. They are directional.

[andrewwynn]

I think that tire came up in one of my first searches.

Combining a slightly bigger tire and the softer sidewall I would recommend over going to the bigger size.

[bcredliner]

You have to be very careful about going to other size tires than specified. The tire size specified can be the widest tire that should be used on that particular rim and a taller tire will reduce rate of acceleration. Taller tires will also lower the RPMs where the transmissions shifts. The shift points are are chosen to provide the best mix of acceleration and economy.

I wouldn't experiment with different size tires. I think, based on what it sounds like you are seeking, a softer sidewall with a tread that minimizes road noise is all you need. I don't know what your budget is but a good tire shop should be able to advise what tire is best based on how much you are comfortable spending and what you want to achieve.