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[gemini330zhp]

Can over all tire diameter affect the car overall????

Stock 18s FF 25.7 and RR 26.3 245/40/18 and 265/40/18

I just ordered new tires 255/40/18 and 275/40/18 and had them mounted on.

The overall tire diameter turned out to be FF 26 and RR 26.7

I am just worried this can affect vehicle warranty and computers on the car.

I just want to make sure???? If not I would have to order new tires with the correct over all tire diameter... thanks for any info If I do order new tires I would go 265/35/18 ff and 285/35/18 rr.

[King Tut]

Your car should work fine with those new diameters. The key is to maintain the staggered diameter. Originally you had .6" stagger and now you have .7" stagger so you should be fine and that won't upset the traction control. I tried running 265/30/19 and 285/35/19 which upset my traction control so much I couldn't use cruise control over 60 mph as the computer would think the tires would start to spin. That was a 25.3" and 26.9" which made the stagger 1.6" which is too much to keep the car happy.

[JCtx]

I don't like changing stock tire sizes myself for several reasons. Having said that, staying within 2% of stock tire circumference (more accurate than diameter) is not going to affect anything, like in your case. You'll never find the exact same circumference in a different tire size, but if you go slightly larger in front, I'd do the same on the rear as well (or viceversa) to keep EDC happy, which is exactly what you did, so no worries.

The difference in rear circumference will be reflected as a slightly higher speed than the speedo indicates, but factory error is usually larger than that, so again, no worries. Take care.

[King Tut]

Why would circumference be more accurate? Your just multiplying by Pi. Diameter is a number that more people are comfortable with.

[gemini330zhp]

Thanks for the info guys car drives fine!!!! Would this tire set up make my car slower since its a tad taller than stock??? Should I have went with a 265/35/18 and 285/35/18 with a 25.3 and 25.9 with a .6 stagger.

[King Tut]

It will change your final drive ratio and make it a little taller giving you a slight bit less acceleration and more top end, but I do mean slight. Since you already got the tires and had them mounted it would cost alot of money to sell them and get new tires mounted. Trust me, as I already had to do that and took a huge loss on selling my old tires. I don't think I would do that large a width tire on the OEM wheels.

[gemini330zhp]

Originally Posted by King Tut

It will change your final drive ratio and make it a little taller giving you a slight bit less acceleration and more top end, but I do mean slight. Since you already got the tires and had them mounted it would cost alot of money to sell them and get new tires mounted. Trust me, as I already had to do that and took a huge loss on selling my old tires. I don't think I would do that large a width tire on the OEM wheels.

Yeah its a slight difference not much but actually not sure if the MPG is right seems like the slightly taller tire made the gas mileage alot better??? LOL at 55 mph the car showed 54mpg!! I just made a M3 hybrid lol!!!! I will keep the tires they are fine I was just paranoid after the installer said I should have went with a 265/35/18 fr 285/35/18 rr instead.

[JCtx]

Originally Posted by King Tut

Why would circumference be more accurate?

Because the difference in circumference (as a percentage) means the difference in speed as well . You want to stay within 2% of that as not to upset DSC (according to a BMW tech, but don't know in reality). Difference in radius tells you how much more or less fenger gap you'd have as a result of the change, and how much more or less ground clearance. Turns out diameter doesn't tell you much . Take care man.

[FStop7]

So what happens if you go the opposite way? Instead of a .7" stagger to the rear, I now have a .3" stagger toward the front (245/35-19 FF, 275/30-19 FR). This was done to make the car sit more level, as it had a slight rake with H&R springs on stock tires.

My cruise control seems to work fine and my DSC works, at least it did during one small test. I haven't really pushed it yet, I'd hate to try only to discover it's not working right.

[Lemans_Blue_M]

Originally Posted by FStop7

So what happens if you go the opposite way? Instead of a .7" stagger to the rear, I now have a .3" stagger toward the front (245/35-19 FF, 275/30-19 FR). This was done to make the car sit more level, as it had a slight rake with H&R springs on stock tires.

My cruise control seems to work fine and my DSC works, at least it did during one small test. I haven't really pushed it yet, I'd hate to try only to discover it's not working right.

275/30/19 tire has a rolling diameter that is nearly 3/4" smaller than stock, so your ride comfort will suffer slightly. That's the only real difference you'll be able to detect.

Your speedo will be off a bit more than usual, but you are still within the factory allowed 3% margin of error.

[rzm3]

The BMW DSC seems to work well with a range of tire sizes and staggerred set up. I was once told by Tirerack that some japanese cars like the G35/7 are really annal about tire sizes.

I've tried on the M3: (all 19" rims)

255/35 275/35
255/35 295/30
255/35 285/35

[Dartanium]

265/35 295/30 seems fine also

[MrHarris]

I'm at 255/35/19 front (rubs slightly) and 285/30/19 rear (looks tiny). I put my sizes in the tire calculator and turns out my front sidewall is fatter than my rear lol. I'll be going 245/35/19 front and 295/30/19 rear next, hopefully that works out well.

[gemini330zhp]

Is it better to have a 0 or .1 to .3 stagger rather than a .6 to .7 stagger?

[rzm3]

Originally Posted by gemini330zhp

Is it better to have a 0 or .1 to .3 stagger rather than a .6 to .7 stagger?

you want to stick to the OE stagger ratio as much as possible. i guess that could be called "better"

[Lemans_Blue_M]

Originally Posted by gemini330zhp

Is it better to have a 0 or .1 to .3 stagger rather than a .6 to .7 stagger?

It's primarily going to effect your perception of the ride quality more than anything else.

Again, you have a built-in 3% margin of error from the factory...

Keep in mind that the OEM 18's have a front-to-rear tire diameter differential of .6 from the factory. (25.7 front, 26.3 rear)

An 18" tire with a slightly smaller diameter will transmit MORE NHV to the cabin, while a tire with slightly larger tire diameter will transmit LESS NHV to the cabin. (due to the taller sidewall)

[gemini330zhp]

Originally Posted by Lemans_Blue_M

It's primarily going to effect your perception of the ride quality more than anything else.

Again, you have a built-in 3% margin of error from the factory...

Keep in mind that the OEM 18's have a front-to-rear tire diameter differential of .6 from the factory. (25.7 front, 26.3 rear)

An 18" tire with a slightly smaller diameter will transmit MORE NHV to the cabin, while a tire with slightly larger tire diameter will transmit LESS NHV to the cabin. (due to the taller sidewall)

So I could have gone with a 255/35/18 and 275/35/18

with a 25 front and 25.6 rear with a .6 stagger???

Or could I have gone with a 245/40/18 and a 285/35/18

with a 25.7 front and 25.9 rear with a .2 stagger???



Why I am asking all this is what would give you the best acceleration with a wider tire combo near to stock?

[Lemans_Blue_M]

Originally Posted by gemini330zhp

So I could have gone with a 255/35/18 and 275/35/18

with a 25 front and 25.6 rear with a .6 stagger also?

Why I am asking all this is what would give you the best acceleration with a wider tire combo near to stock?

Well...the two tires sizes you mentioned are both too small to use on this car IMO.

255/35/18 = 24.9" diameter (way to small)

275/35/18 = 25.5" diameter (boarderline too small)

They have very short sidewalls, which will not give you the performance you seem to be looking for...

I don't think these sizes are a very good option for the M3, and I'll explain why.

Generally speaking, the tire with a little taller sidewall will give you slightly better traction. (within the same brand and tire model)

Since the shorter sidewall tires have less 'give' in them when the power is applied, this will slow you down when you really lay the hammer down. The only thing you will accomplish, is burning the tires down at a much faster rate than normal. (spinning the wheels) A rigid short sidewall tire is less likely to provide you with good traction, since the energy that is being transfered through the drive line has to be absorbed by the rubber tires on your car. Radial tires with a taller sidewall will flex more than a tire with a shorter sidewall. At the moment when the power is being transfered, you want the tire to absorb some of this energy, so your tires don't break traction due to the rapid increase in torque as you accelerate.

If your tire sidewall doesn't retain the proper level of flexibility, a high powered car will break traction easier, and you'll actually lose time in a 0-60mph sprint or even a 1/4 mile run at the drag strip. (where the 60 ft. time is crucial to running a good elapsed time)

[gemini330zhp]

Originally Posted by Lemans_Blue_M

Well...the two tires sizes you mentioned are both too small to use on this car IMO.

255/35/18 = 24.9" diameter (way to small)

275/35/18 = 25.5" diameter (boarderline too small)

They have very short sidewalls, which will not give you the performance you seem to be looking for...

I don't think these sizes are a very good option for the M3, and I'll explain why.

Generally speaking, the tire with a little taller sidewall will give you slightly better traction. (within the same brand and tire model)

Since the shorter sidewall tires have less 'give' in them when the power is applied, this will slow you down when you really lay the hammer down. The only thing you will accomplish, is burning the tires down at a much faster rate than normal. (spinning the wheels) A rigid short sidewall tire is less likely to provide you with good traction, since the energy that is being transfered through the drive line has to be absorbed by the rubber tires on your car. Radial tires with a taller sidewall will flex more than a tire with a shorter sidewall. At the moment when the power is being transfered, you want the tire to absorb some of this energy, so your tires don't break traction due to the rapid increase in torque as you accelerate.

If your tire sidewall doesn't retain the proper level of flexibility, a high powered car will break traction easier, and you'll actually lose time in a 0-60mph sprint or even a 1/4 mile run at the drag strip. (where the 60 ft. time is crucial to running a good elapsed time)

Thanks for the classroom discussion!!!!!! I am learning alot more about tire sizes and how it affects the car. With my choice of 255/40/18 and 275/40/18 that I have installed on my wheels with a 26 and a 26.7 with a stagger of .7 I should be ok near stock then. With just a slight taller ratio.

[MrHarris]

Has anyone tried 285/35/19 in the rear lowered on springs like H&R/Eibach/RDsport?

[Lemans_Blue_M]

Originally Posted by MrHarris

Has anyone tried 285/35/19 in the rear lowered on springs like H&R/Eibach/RDsport?

Man you REALLY want those 285/35/19's huh?

This is like your 10th post about this particular size.

BTW: I thought you were going to get 295/35/19's ?

[gemini330zhp]

Originally Posted by MrHarris

Has anyone tried 285/35/19 in the rear lowered on springs like H&R/Eibach/RDsport?

I think you want 285/30/19 I want 285/35/18!!!!