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Discussion Starter · #1 ·
OK, so I'm considering upgrading the size of my tires/rims on my 2002 330xi sedan.
I have the sport package so the tires are:
• 17 x 7.0 Double Spoke (Styling 79) alloy wheels, 205/50R-17 all-season tires


If i choose to get larger tires does my speedometer need to be recallibrated? Because hypothetically, if i had tires that were 2" in height, they'd rotate MUCH more than would my current tires, and so the MPH calculations would be off, wouldn't they? So, is recallibration a necessary step?

also,
I certainly want to get larger rims/tires, and I'm considering some Hammans (PGIIs--18"). What's the weight difference on the type 79 rims and these? what about the style M68's?

thanks.
 

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King of Rear Clunks
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Stick to tires of the same diameter, +/- 0.25in dia and you won't have that problem.

And I believe Clem said in another thread today that Hamanns are on the heavy side, although OEM wheels also tend to be pretty heavy.

I posted a BUNCH of tire/wheel info in another thread today that you might wanna take a look at.
 

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The Original Dr. Phil
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330Guy said:
OK, so I'm considering upgrading the size of my tires/rims on my 2002 330xi sedan.
I have the sport package so the tires are:
• 17 x 7.0 Double Spoke (Styling 79) alloy wheels, 205/50R-17 all-season tires


If i choose to get larger tires does my speedometer need to be recallibrated? Because hypothetically, if i had tires that were 2" in height, they'd rotate MUCH more than would my current tires, and so the MPH calculations would be off, wouldn't they? So, is recallibration a necessary step?

also,
I certainly want to get larger rims/tires, and I'm considering some Hammans (PGIIs--18"). What's the weight difference on the type 79 rims and these? what about the style M68's?

thanks.
Not sure about weight difference, but Mike 325xi has put style 68s on his car and has raved about them. He has kept his style 73s for winter use.

If you upgrade do you plan on selling the 79s? If so please contact me, I'm in PA and would be interested.
 

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Discussion Starter · #6 ·
right...

that's what i'm saying JPinTO, if I wanted to get 18" rims but keep a larger tire on, I'd have to recallibrate the speedometer, would I not? Does BMW do this? Because I want 18" rims but I'd rather not get too thin tires so they don't pop/wear down too quickly.

Basically, I want the widest possible without going under 45. (it's basically the look you get with a Viper from the back--the wheels are ENORMOUSLY wide. I like it.)

SO, can you increase the width without increasing the percentage (for height of side wall)? Meaning, can you have 225/45 on a car and also have 265/45? Or does increasing the width mean a smaller side wall?

thanks.
 

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With a variance of +/- 3% in the OVERALL wheel and tire height you will not have to recalibrate your speedo.

Not that our speedos are that accurate anyways. :tsk:

330Guy said:

SO, can you increase the width without increasing the percentage (for height of side wall)? Meaning, can you have 225/45 on a car and also have 265/45? Or does increasing the width mean a smaller side wall?
Increasing width should also have a smaller aspect ratio (i.e. 40 series, 50 series etc) The aspect ratio is a percentage of a tire's width which when calculated will give you the sidewall height.

For example: 225/40/18 will be approximately the same height as a 235/35/19 and a 225/50/16 with a +/- 3% variance
 

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OK, excuse me for shouting here... DO NOT DO IT!!! In addition to needing your speedometer recalibrated, you will need your differentials changed. Your car will be considerably slower if you do this. It will also raise the car FURTHER into the air, thus dramatically worsening cornering, too. Doing this would BADLY screw up your car. I STRONGLY recommend that you don't do it.

Oh yes, increasing the circumference of your tires also worsens braking performance.

That said, if all you care about is looks, whatever. Go for it if it makes you happy. But make sure that you won't miss the performance.
 

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Discussion Starter · #9 ·
whoa

ahhhhh, whoa, no none of that. Honestly, this is partly my inquisitive side, i'm just curious about these things and "hypothetically speaking,..."

BUT, I do want 18"s on my car. So, I want 18"s that are very wide but don't make the tires too thin (sidewall height). Can some1 give me a good size? (i'm guessing like 250/45/18?)

thanks

and yes, I DO want all the optimum performance I can get, FOR SURE!
 

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King of Rear Clunks
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The widest 18s you can put on the car with proper wheels without modifications or otherwise screwing something up is 235/40/18F and 265/35/18R. I know for sure that with 18x8ET47 front and 18x8.5ET50 in back (what I have), this will fit with no adverse effects, aside from possibly more understeer.

Also, the aspect ratio (the 2nd #) is a relative measurement to the first, not an absolute one, so 'not wanting to go under 45' isn't a valid statement. In fact, those two sizes are the same diameter (25.3in) as a 205/45/18 if such a thing existed.
 

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Re: whoa

330Guy said:
...........I DO want all the optimum performance I can get, FOR SURE!
If you want 18s and optimum performance then a wider tire isn't what your looking for in terms of acceleration. Especially when you add your criteria together.

330s (nevermind the 323/325/328) don't have enough torque to justify have such wide rear wheels. IMHO

The main purpose for wider rear wheels is to gain maximum traction potential. i.e. Porches, Ferraris, Vipers with rear wheels 275+
 

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For optimum performance on 18" wheels (which are a bit larger than ideal, but certainly aren't bad option), go with 225 or 235/40s all around. Really wide tires in back lead to lots of understeer with these engines. IMHO, that takes a lot of the fun out of driving.

If you manage to end up with a slightly smaller overall diameter, it's probably a good thing. Bimmers are geared way too tall, anyhow. I'd love to put a 10 to 15% shorter diff in my car.

At any rate, I'd not recommend going wider than 235. I'd pick 225/40, personally. The other thing to keep in mind is that really wide tires will lead to more and more road wander.

There are tradeoffs with any tire size. Your opinion may very well differ from mine. The same size all around will give you more fun and more control. Staggered tires will give you a little more grip, arguably at the cost of a little fun and control. Just so long As you keep it to abotu the same diameter (erring smaller, not larger), you'll notice a huge improvement in handling whatever you do. :)
 
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