Blk-G35

I was wondering if one plus size tire can be fitted onto the G37 stock 19" wheels. I was thinking of 235/45-19 front and 255/40-19 on rear.

timothyn1967

Unless this car is really tighter on space than it looks, you should be able to go up one size with no problem. You are only talking about a centimeter of extra width, which works out to just 5mm extra bulge per side. But if you ask me, that tiny bit of difference wouldn't be worth the extra cash since it would hardly be noticable anyway.

dmkozak

iTrader: (1)

On the same size wheels, the M6 uses 245/40 fronts and 275/35 rears. They would be sizes to get as they retain the same rolling radius as stock.

lowrider

iTrader: (1)

Not quite - Specifications for M6 are:

Tires and Wheels
Tire dimensions (performance tires) - front 255/40ZR-19

Tire dimensions (performance tires) - rear 285/35ZR-19

Wheel dimensions, front/rear 19 x 8.5 / 19 x 9.5

Material Light cast-alloy

That's .5" wider in back than the G37, and the tire sizes are 10mm wider front and rear than you quote.

However, I agree with your recommendation that 245/40/19 and 275/35/19 would fit and work great on the G37s 8.5" wide front wheel and 9.0" wide rear. If you could get the same brand and model of tire that is currently mounted on the car, you could move the rear tires to the front wheels and only replace the rears.

Just rechecked the BMW site, and found that the optional wheels on the 650i are:

Optional tire dimensions 245/40R-19 front/275/35R-19 rear run-flat performance

Optional wheel dimensions 19 x 8.5 front, 19 x 9.0 rear inches

Material forged alloy

So, I guess you are half right, and yes the optional wheels on the 650i are indeed the the same widths as the same as the G37.

Lou

Blk-G35

Why does profile of the tire need to be changed from 45 to 40 on front and 40 to 35 in the rear when wider tires are used. Also does overall diameter of the tire changes due to the profile thickness difference.


Will it be little too rough on daily driving?

UNV-IT46

iTrader: (3)

the side wall profile is relative to the width of the tire, so for instance a 225-45 would not have the same side wall height as say a 275-45 you would need to go down to a 275-40 to have the same side wall as the 225 because of the width of the tire.

lowrider

iTrader: (1)

You started to explain it, but well, let me try. The second number in the tire size is the ratio of the tire height relative to it's width. So a 245/45 tire would have a sidewall height equal to 45% of it's width, or 110mm. A 275/40 would have a sidewall height of 40% of it's width, or 110mm. So you see, the 245/45 tire and the 275/40 tire have the same overall diameter. Do the math, you'll get the idea.

Lou

Blk-G35

Thanks for great feedback and I was initially thinking about going with 255 but 265 might be better size for stock G37. When the time come for new rear tires I'll definetely explorer more options.

Gwhiz37

I just ordered Michelin Pilot AS w/ 400 tread for $247 a piece, size 275/35R 19. The 9" rim cannot take a wider tire and the 275/35R will keep the speedometer and diameter difference to a minimum. Many benefits in doing so, far too technical to go into here (plus, a fair amount of opinions).

The below is from 1010tires.com (where you can do you own playing). What is important is to make sure the new tire can fit on the stock wheel.

Stock Tire - 245/40R19 >Search Tires Tire 1 - 275/35R19 >Search Tires
Section Width: 9.64 in 245 mm

Section Width: 10.82 in 275 mm
Rim Diameter: 19 in 482.6 mm

Rim Diameter: 19 in 482.6 mm
Rim Width Range: 8 - 9.5 in

Rim Width Range: 9 - 11 in
Overall Diameter: 26.71 in 678.43 mm

Overall Diameter: 26.57 in 674.87 mm
Sidewall Height: 3.85 in 97.79 mm

Sidewall Height: 3.78 in 96.012 mm
Radius: 13.35 in 339.09 mm

Radius: 13.28 in 337.31 mm
Circumference: 83.91 in 2131.3 mm

Circumference: 83.47 in 2120.1 mm
Revs per Mile: 778.7

Revs per Mile: 782.8
Actual Speed: 60 mph 100 km/h

Speedometer1: 60.3 mph 100. km/h
Speedometer Difference: - Speedometer Difference: 0.526% too fast
Diameter Difference: - Diameter Difference: 0.53%

G2Envy

iTrader: (1)

This was created for the Miata but it will work with any tire. Just enter in the numbers and you can see how much the speedometer is off by.

http://www.miata.net/garage/tirecalc.html

NasaMan

I vote for this set up. Post pics if you have them. I prefer them on stock rims. Thanks, Gents.
Edit: Oh, btw. The original Bridgestone RE050 has the narrowest section widthso be careful if go with diff brand.

lowrider

iTrader: (1)

Actually those tire computers are only a good starting point. Each Manufacturer's tire dimensions vary slightly within a given size.

However, a good rule of thumb in this case is to assume that the 245/40/19 and 275/35/19 within any manufacturer's lineup will have the same outer diameter, and is therefore interchangeable, if there is sufficient room under fender, and the width of the wheel will handle the wider tire.

Cases in Point - The outer diameter of the Dunlop Sport Max are:
245/40 - 26.7" - 275/35 - 26.6"

Michelin Pilot Sport PS2:
245/40 - 26.7" - 275/35 - 26.6"

Bridgestone Potenza RE050A:
245/40 - 26.9" - 275/35 - 26.5"

Bridgestone Potenza RE050A RFT:
245/40 - 26.9" - 275/35 - 26.7"

Goodyear Eagle F1 GS-D3:
245/40 - 26.7" - 275/35 - 26.6"

Michelin® Pilot Sport A/S
245/40 - 26.7" - 275/35 - 26.6"


None of the tires listed match the calculations Gwhiz's mathematical computations, so we must look at each tire individually.

Also, I assume Gwhiz plans to put his current rear tire on the front and use the new tires on the back. IMO, this may not be a good idea. Mixing different brands and types of tires on a performance vehicle may not be the best for optimum handling or safety. Typically High performance tires have a tread wear rating of somewhere between 140 to 240. The Michelin PS AS tire has a rating of 400. This means the rubber compound is softer in the Hi-Po Tire. Also the Tread design in the Hi-Po tire is not meant for all season use, and is designed for ultimate handling on warm dry or wet roads. The design of the AS tire is more compromised and will not handle the same. The tires will grip and slip at different times in the same road conditions.

Lou

Gwhiz37

In my case the Michelin® Pilot Sport A/S 275/35 @ 26.6" are only going on the rears. According to Bridgestone, the stock diameter is 26.7" thus 26.6" on the Michelin will fit fine. Further, on the Michelin website there is specific information as to the sizing requirements that the Michelin will require. The stock rim meets thus requirements. Thus, in theory, if not in practice, the Michelin should fit and behave on the rear without incident. FYI - I did the exact same change to my 2003 G35 Coupe without incident.

I am not going to place the current rears on the front. Living in lower NC, I have cold weather with some rain and ice a few times, but almost no snow. I look to having a good all weather tire that will handle the cold weather with some rain (remember the Birdgestone are not cold weather tires). Yes, the front may not have that good of handling in the cold weather since they will not be AS. I fully realize that, but IMO there is no need to purchase new fronts. The rear causes me more grief in cold and wet weather.

I agree that mixing and matching tires has a risk to it, but I am willing to take that risk. I will use the stock fronts until they wear out and then decide to use the stock backs on the front until they wear out or get a new set of Michelin AS. I completely understand the tread wear concerns and appreciate the advice; however, given the driving that I do I am willing to take that risk. This will be the third vehicle that I have done this with the first being a 240Z, the second, the 2003 G35 Coupe (now has 60,000 miles on it). Maybe I am lucky, but in doing my own research reading through way too many web articles, working with different local tire companies and through my driving, I have yet to see the impact/difference. I believe that the tire companies, much like the "change your oil every 3,500 miles" companies, put too much fear into place thus people are afraid to try or do anything other that what they programming to hear. I'll let you no more when I put he tires on and take it up to tsome of the winding roads for a spin. Pix will follow too.

lowrider

iTrader: (1)

Just alerting you to the risks associated with mix and match of tires developed and made for different purposes. As I stated previously however, the sizing is ideal for your new ride. Good Luck to you and your new Coupe

Lou