Don Juan

So here is the scoop about Rear tires diameters

The E60 530s come either with :

225-50-17 (x4) Overall tire Diameter = 25.86" (656.80mm)
245-40-18 (x4) Overall tire Diameter = 25.72" (653.20mm)

These tire diameters are calibrated with the speedometer.

The E60 545s come either with :

225-50-17 (x4) Overall tire Diameter = 25.86" (656.80mm)
245-40-18 (x2) Overall tire Diameter = 25.72" (653.20mm)
275-35-18 (x2) Overall tire Diameter = 25.58" (649.70mm)

So In 19 inches will be:
245-35-19 (x2) Overall tire Diameter = 25.75" (654.10mm) <-- so here is within the factory specsm of a 530
275-30-19 (x2) Overall tire Diameter = 25.50" (647.60mm) <-- here the tire diameter seems to be too small, therefore speedometer issues (shows higher speeds while in reality is less)
or
285-30-19 (x2) Overall tire Diameter = 25.73" (653.60mm) <-- here the tire is closest to factory diameter specs

So my point and request for advise is, based on the number above, wouldn't make sense (for E60 530s only) to have the 285-30-19s in the rear ???

BullMkt

I always thought the first series of numbers referrred to the width of a tire while the second series refered to the overall diameter (meaning 285 is just wider than 275)?!? If I'm wrong, than I'm definitely interested in an answer to your question...

Also, you're talking about a difference of about 5.6 mm so how much (in mph) is the discrepency.

6spdMan

By doing the math, the initial conclusion I came to was that 285/30-19 was the ideal size for the rears. I was going to buy the PS2's in this size until I realised the following:

1. BMW always has a 30mm stagger on their cars, for example:
E60 M5 style 166M - 255/40 Frt and 285/35 Rear
E60 520/523/525/530/545 style 124/128/172 - 245 and 275 (18" and 19")
E46 and E90 various models - 225 and 255 (18" and 19")
E60 Alpina B5 - 245/40 Frt and 275/35 Rear on 19"
The point here is that BMW has, in their infinite wisdom, chosen a 30mm stagger to take into account the F/R weight distribution and handling characteristics of their cars. By going to wider rears, you increase the understeer. Which is fine if you have enought torque to break the rears free, but with a 3.0l M54 and standard gearing, this may be a bit too much contact patch. More importantly, I did not want to second guess BMW's engineers.

2. Not all tires conform exactly to the mathematical formula. For instance, the PS2 275/30-19 is 25.6" in OD according to Tirerack's spec sheet, not 25.5" as the formula would give you. This is close enough for me. Also slightly lower gearing from the slightly smaller OD.

3. 275/30-19 is a much more readily available size than 285/30-19. Hence they will be cheaper (US$78 per tire on tirerack.com) and not on permanent backorder. What happens when you have to replace your rears? More $$$, and a long wait.

4. 275/30-19 will be lighter than the 285/30-19. In the case of the PS2's, this weight difference is 3lbs per tire. Not a lot, but remember each lb of rotating mass is worth 10lbs of static mass.

5. BMW speedometers are always 'optimistic' by 3 to 5% depending on the speed you're at. An indicated 120km/h will be a real 115km/h, all the better to keep you out of trouble with Law Enforcement. A slight difference in tire size doesn't wreck a perfect reading, it merely makes an inaccurate reading more inaccurate!

Net result is slightly better response due to lighter mass (point 4) and slightly lower gearing (point 2). And a lower credit card bill at the end of the month (point 3).

Don Juan

6spdMan,

Very interesting details. I thought about some of those too after further researching. In addition 3 pounds extra per tire is equivalent (by a formula 3x2=6, 6x7=42) to having an obkect of 42lbs in your car, thus increasing the rolling mass weight, not much for a V8 but felt in a M54 engine as mine. I have also noticed the difference diameters per brand and they fluctue. So pretty m,uch just trying to get nice, good and cheap. So far i'm inclining into the Nittos 555 but havent heard anyones commnets. My cousin has them in hi s330Ci and he likes them, he says they stick as the S03s and are a lot less harsher.. so unsure now.. this is hwat i have been putting together to make my descision this weekend...

6spdMan

How about the new Toyo's? I've read they're pretty good value for money on the e46fanatics board.
I figure if Michelin is good enough for all the F1 teams except for Ferrari, it's good enough for me.

Don Juan

Umm toyos? no i have not check on those..like what model tire are you referring? My friends have had the Yokos ES100s, good tire but start making noise in less that half its life and wear pretty fast...ummm Toyos.

6spdMan

I think they are called Toyo Proxes R1S or something like that. The original R was very good, but the new RS (or something like that) is supposed to be the cat's pyjama's.

Don Juan

Got it Toyo Prozes T1r..ummm 280 AA for about $1100... not bad

UUronL

How about the new Toyo's? I've read they're pretty good value for money on the e46fanatics board.
I figure if Michelin is good enough for all the F1 teams except for Ferrari, it's good enough for me.
[/quote]



The new Toyo Proxes T1-R seems to improve upon the T1-S in all areas, and the T1-S was a phenomenal tire. I'd go that route personally. They're harder to come by though - not generally available through the normal online channels.


I was really impressed with Sumitomo HTR Z II tires on my last car, having run both Pilot Sports and Toyo Proxes T1-S prior to running the Sumitomos. They wore very well, had more than 90% of the Toyo's grip, and were nice and quiet.


Tire rack has them for ridiculously low $$$.

http://www.tirerack.com/tires/Sizes.jsp?ma...&model=HTR+Z+II


Good reviews too:

http://www.tirerack.com/tires/tires.jsp?ti...eModel=HTR+Z+II

Don Juan

UURunl, yes i saw those but sumitomo does not make the sizes I'm looking for... <_<

So far Im debating now between the following tires:

Toyo Proxes T1R.. found the fornt ones but they can not locate the rears
Nitto 555
or
Bridgestone RE750



they are about the same in price (@$1000) ,<span style='font-size:14pt;line-height:100%'> can not believe no one has changed their tires or have any input on the tires they have...anyone?</span>

here are some pictures