[lkstaack]

Originally Posted by terryd5150

I agree with you on that; however, I had a 2009 335i that came with the sport package 18" wheels, 225/40 front, 255/35 rear.

I went to 19" 437M reps with 235/35 front and 275/30 rear; I noticed a distinct increase in the rate at which the odometer started adding up the miles.

10-minute drives around town (not on highways or interstates) would show I'd traveled 20 miles.

While not concrete evidence in itself, it does suggest this theory of "averages" may play into this equation somewhere.



Again, just pure speculation based on ancedotal evidence.

You can calculate changes in speedometer readings based upon tire sizes with this calulator: Speedometer Calculator

[floydarogers]

Originally Posted by lkstaack

I have researched multiple BMW related websites now. Those that address speedometer sensors point to one location. Even though ABS sensors calculate wheel speed for each wheel, only the speed from the left rear wheel is used for the speedometer. Can you provide information that disputes this?

No, but I don't really care. The speedo is so far off I generally ignore it in any case. The ABS/DSC system has to create an average that would be different from the LR wheel-speed, not sure why they wouldn't use it. Whatever.

[terryd5150]

Originally Posted by jnecr

You're just driving a lot. You're talking about doing 2.5k miles/year vs 16k miles/year. This is in no way explained by tire size differences...

I know it seems implausible, but that's the only part of the equation that changed.

The distance to work (and the beer store ) didn't change.

I changed the wheels back to the originals when I traded it back in; a five-hour drive to the dealership to trade it in registered slightly over 200 miles.

With the 19" wheel & tire combo, it registered 50 miles on in-town commutes.

Regardless, the F32 I picked up registered the same 200-ish miles on the trip home.

I'm happy now.

[lkstaack]

So, I ended up ordering Michelin PS4S 245/35x19 tires for the front and 264/35x19 in the rear. I chose not to get the 255s for the front as my analysis suggested because: 1) I learned that matching diameter sizes isn't as important in the front (the speedometer gets its information from the left rear), and 2) I don't want to risk rubbing during turns. I'll report back in a few weeks after I've driven on them awhile.

[terryd5150]

Originally Posted by lkstaack

So, I ended up ordering Michelin PS4S 245/35x19 tires for the front and 264/35x19 in the rear. I chose not to get the 255s for the front as my analysis suggested because: 1) I learned that matching diameter sizes isn't as important in the front (the speedometer gets its information from the left rear), and 2) I don't want to risk rubbing during turns. I'll report back in a few weeks after I've driven on them awhile.

Please keep us posted.

[terryd5150]

Originally Posted by lkstaack

So, I ended up ordering Michelin PS4S 245/35x19 tires for the front and 264/35x19 in the rear. I chose not to get the 255s for the front as my analysis suggested because: 1) I learned that matching diameter sizes isn't as important in the front (the speedometer gets its information from the left rear), and 2) I don't want to risk rubbing during turns. I'll report back in a few weeks after I've driven on them awhile.

Updates?

Pics?

[terryd5150]

Originally Posted by lkstaack

I have researched multiple BMW related websites now. Those that address speedometer sensors point to one location. Even though ABS sensors calculate wheel speed for each wheel, only the speed from the left rear wheel is used for the speedometer. Can you provide information that disputes this?

That seems highly unlikely.

Could you link to the sources you've researched?

[floydarogers]

Originally Posted by terryd5150

That seems highly unlikely.

Could you link to the sources you've researched?

There are BMW techs posting on BMWCCA's forums that have posted that, fyi.
But even though I believe it's an average, I don't really care too much. I have much more problems with the built-in inaccuracy due to crazy regulations.

[CTDrifter]

Originally Posted by floydarogers

There are BMW techs posting on BMWCCA's forums that have posted that, fyi.
But even though I believe it's an average, I don't really care too much. I have much more problems with the built-in inaccuracy due to crazy regulations.

Any pics? Think I bought same rims as you. I was planning on going Michelin PS4 235/40 and 265/35, I?d prefer a little more sidewall if possible and don?t want any rubbing.

Why is everyone so concerned with speedometer? With all the sizes mentioned you?ll only be off a couple MPH at highway speeds...

[floydarogers]

Originally Posted by CTDrifter

...
Why is everyone so concerned with speedometer? With all the sizes mentioned you?ll only be off a couple MPH at highway speeds...

I have two sets of winter wheels and tires I've used on my 2010 335d E90, which has tires one size smaller than F3x, if you didn't know. Both are square.
1) 225/45R18 (that's an F3x size - E3x is 225/40R18) of Blizzak WS80. The speedometer is almost dead-on the real speed with those tires on - perhaps 1/2 mph fast.
2) 225/45R17 Michelin Primacy RFT's. That is an OEM size, comes on basic 325i/328i E9x (wheels are OEM BMW). With those tires on, the speedo is 4-5 mph fast at 70-80 mph.

So, from the "standard 2-3 mph fast with OEM-size tires, the actual range of measured offsets from true is substantially bigger than your "couple MPH":
4-5 versus 2-3 (Primacy vs. Michelin Pilot PS2 ZP). Both factory sizes for E9x.

Different manufacturers give different results.

[terryd5150]

Originally Posted by CTDrifter

Why is everyone so concerned with speedometer? With all the sizes mentioned you?ll only be off a couple MPH at highway speeds...

It isn't the speedometer, in and of itself, it's the impact on the odometer.

If your speedometer is reading too fast, your odometer is accumulating miles at a rate faster than it should (and devaluing your car at an artificially higher rate in the process).

[CTDrifter]

Originally Posted by terryd5150

It isn't the speedometer, in and of itself, it's the impact on the odometer.

If your speedometer is reading too fast, your odometer is accumulating miles at a rate faster than it should (and devaluing your car at an artificially higher rate in the process).

Lol, an extra 2,000-5,000 miles every 100,000... seems trivial.

[lkstaack]

I've added pictures and comments at the end of my first post. Great wheels and great wheel/tire sizes.

[terryd5150]

Originally Posted by CTDrifter

Lol, an extra 2,000-5,000 miles every 100,000... seems trivial.

Check my earlier post; I'd hardly call that trivial


FYI the F32 I replaced that car with is showing 350 miles for the last 30 days driving the same route.

[terryd5150]

Originally Posted by lkstaack

I've added pictures and comments at the end of my first post. Great wheels and great wheel/tire sizes.

Looks great.

Maybe I missed it, but how wide are those wheels?

[dr.roro]

Can you confirm if the OEM center caps fit in the FT101?

[lkstaack]

Originally Posted by dr.roro

Can you confirm if the OEM center caps fit in the FT101?

It's possible to fit BMW center caps into these 305Forged wheels, but it is very tight. I opted to keep the caps it came with because, in part, I was concerned that I could break off a cap tab.

[Mkswoosh]

purchasing same spec wheels as the OP. 19's 8.5 et 32 and 9.5 et 40 on an xdrive f30 with coilovers

but for tires....

235/40 and 265/35 OR 245/40 and 275/35

is the difference that noticeable between the two? more concerned with speedo error.
trying to eliminate wheel/fender gap and protection to the wheels because the roads are usually bumpy with random potholes. BUT i like the wider look of the tires. help a first time wheel/tire buyer out.

[Pipe335i]

I have 403m staggered with 255/35r19 in all corners, no issues at all .