hi, quick question: i like my car (m37x) except the marshmallow feeling of 18 inch wheel. What causing that feeling? Size of the wheel of size of the tire? 19 or 20 inch? I prefer 20 inch but where I am living the road are pretty bad ... A lot of
pot holes....

Combination of the tall side wall of the 18's and the factory suspension. Shorter sidewalls (19 or 20" wheels) will help. Adjustable coilovers, even if set to factory ride height, will let you tailor the feel to your liking even more.

go with some factory 20" sport wheels. IMO you cant beat that look.

Its is hard on the road 245-40-20 with our car?

Yep, 20 is the way to go. Just don't go lower than 40 series tires.

Pierremontreal wrote:Its is hard on the road 245-40-20 with our car?

I just put the 20"s on mine with the 245/40 tire and the ride is no more harsher than the 18". however the turn in and overall handling is much sharper than before.

I second all of the above. The difference between 19 or 20 wheels is mostly the eye of the beholder. Personally, I think 20s are just a bit too big for our cars, but clearly I am in the minority as I see plenty of them. As stated above, you should not go lower than 40 series to make sure you have enough 'give' for pot holes and other things like railroad tracks, etc.
I have 255/40/19s on 19 x 8.5 (+40) wheels and the comfort has not changed at all, but the handling is better and the wet grip is much improved. Plus the wider tire (255 instead of 245) looks awesome, like those on a merc S series or a BM 7 series. The extra height from the 19 inch wheels is cancelled out by dropping from 45 series to 40 series tires and the 19 x 8.5 inch wheel (replacing 18 x 8) makes the tires come very close to flush with the fenders.
The only difference with adding 20's is that you probably need to do suspension work to lower the car. I didn't need to lower the car or add spacers.
Pics are in the following thread:
latest-mods-m35-2009-t598772.html

Larz wrote:The difference between 19 or 20 wheels is mostly the eye of the beholder.

I agree. Less sidewall does technically make for more road-feel and control but is probably negligible between 19 and 20. 18 to 20 is a significant jump though and should be very apparent.

Larz wrote:The only difference with adding 20's is that you probably need to do suspension work to lower the car. I didn't need to lower the car or add spacers.

Not sure what you mean by suspension work but other then springs or adjustable coilovers you don't need do anything else for 19's or 20's. You also don't need to lower the car for 19's or 20's so I assume you mean cosmetically. And the need for spacers is based on wheel offset, clearance needs, and (like lowering) cosmetic preferences, not wheel diameter.

Although the top fender gap with factory 18's and 20's does not stand out as much as it does with aftermarket 20's it still very noticeable (I look at the 18's gap everyday ). For me it becomes especially obvious when aftermarket wheels of any size are used. Even with the small increase to 19's I think this gap would be too much for me personally. Can't tell though since all the pictures in your tread are taken from very close and with this gap cropped out.

Back to the OP's question, like suggested above I think if lowering is not being considered the factory 20's would be perfect.

Thanks you very much for all suggestions!

Debonair wrote:
Although the top fender gap with factory 18's and 20's does not stand out as much as it does with aftermarket 20's it still very noticeable (I look at the 18's gap everyday ). For me it becomes especially obvious when aftermarket wheels of any size are used. Even with the small increase to 19's I think this gap would be too much for me personally. Can't tell though since all the pictures in your tread are taken from very close and with this gap cropped out.

The photos in my post were taken to show close-ups of wheels and tires - there was virtually NO changes in gap. Hence the notation I made in that thread about the gap, height, etc:
The tires sit just slightly inside the wheel well. The overall height increased by 0.3 inches. Wheel well filled out an extra 0.2 inches. Speedo change: 60mph now equals 60.9mph. Revs reduced from 758 to 746 per mile.
My concern regarding suspension was as follows. If you increase the wheel size by 2 inches in circumference, you are raising the car off the ground by 1 full inch. Besides being noticeable, it also raises the car's center of gravity. That is nearly 3X increased height off the ground compared to my wheels. I don't know enough about the physics of this change regarding the car's handling and stability, ... but .... When the Ford Explorer came under scrutiny for it's frequent roll-overs, design experts determined that lowering the vehicle's center of gravity by 1.5 inches would remove that risk. The newer models are 2 inches lower. I don't know if that has any relevance to this discussion, but that was what I was worrying about when changing the height of my car. I may have been grossly OVER reacting in which case I defer to your expertise.

Larz wrote:My concern regarding suspension was as follows. If you increase the wheel size by 2 inches in circumference, you are raising the car off the ground by 1 full inch. Besides being noticeable, it also raises the car's center of gravity.

This is incorrect. The overall wheel diameter does not change when going from 18's to 19's or to 20's (unless an incorrect sized tire is used). The tire size is adjusted to keep it within factory spec. The cars overall height will not change.

Here are the two M37/M56/Q70 factory tire sizes compared so you can see what I mean, specifically the diameter since this is what would potentially raise or lower the vehicle. As the wheel size goes up the side wall goes down to compensate and keep the diameter within spec. Virtually no change in ride height or speedometer calibration.

Another question, since i can't find factory oem 20 inch, witch aftermarket brand wheel are very good? Because where i am living, the road is pretty bad (pothole) after winter... So i am scare to damage cheap aftermarket wheel. Any suggestion?

I personally suggest you find a wheel design / style you like first. Any brand at any price point. Then once you know what style you are looking for you can start finding alternatives, and getting suggestions, at a higher quality and or lower price depending on your goals and budget. This tactic works for me.

I had 19" TSW wheels on my previous car with 245/35 & 275/30 (3.25" sidewalls) tires and they took a beating. Never bent or went out of round.

I'm sure others will have some suggestions too.

Just a question on the 20 inch wheels, should this OEM sit fine in the M37x ? It does say 37s only but I need a confirmation before I purchase.

http://parts.infinitiusa.com/infinitiPa ... alogid=212

ANy input is appreciated.

I found an Infiniti dealer that is selling them online for $375 X 4 wheels and I have a coupon code for 25%, the total is coming to $1160 shipped. I didn't buy because I wasn't sure if it fits 37x...

They will fit