why is the sky blue? we truly may never know.

As others mentioned, it won't affect the ride in most cases. Track applications, however, require consistency to a much greater degree than our daily low-speed commute. The air we breathe and use to inflate our tires mostly consists of nitrogen already (78%). It's likely cheaper to get a tank of compressed *moistureless* nitrogen than to properly dry the ambient air, as far as tire applications are concerned.

I agree.

Nitrogen is used in track applications to get consistency in tire pressures. But, if you are Michael Shumacher, 1 psi can make a noticeable difference to you.

Most street drivers, on the other hand, would NEVER notice even a huge variance in tire pressure. In fact, most people don't even notice when one of their tires has ZERO pressure! I see posts all the time (I think I've seen some here) from "enthusiast" drivers who have had a flat and drove for miles before even noticing it.

Certainly, there is no one here that could notice the small changes that a tire with normal air in it undergoes as it heats up (the pressure increases) on their street car.

Anyone who thinks they can is flattering himself.

But we've known for some time why the sky is blue... it has to do with the atmosphere scattering the light. Go here for more info:

http://www.why-is-the-sky-blue.org/w...-sky-blue.html



Oh, wait, that was one of them there rhetorical questions, wasn't it?

Nevermind

It wouldn't. The tire doesn't know or care what the composition of the air inside it is. All it cares about is PSI. A tire that has 35 PSI of air in it will ride the exact same as a tire with 35 PSI of nitrogen in it.

If the air in a tire were absolutely dry, there would be very little pressure increase in the tire as it heats up during driving. The more moisture in the air in the tire, the more the PSI will increase as the tire heats up.

But, the tire pressure specs are for cold tires, and take into account the PSI increase that occurs in the tire with normal air in it.

If you were to put pure nitrogen in a tire (which is theoretical only, because to get pure nitrogen you'd have to first evacuate all the air in the tire), then theoretically the tire's PSI would not increase as much as the tire warms up. You could accomplish the same thing (lower PSI) by simply letting a little air out of the tire.

Again, all of the differences and increases we are talking about are completely unnoticeable - unless perhaps your name is Michael Schumacher.

yes Spyke, that was a rhetorical question , but thanx for the cool site

I warned my local Sears auto center to be careful with the (C7) rims, but they didn't listen... so they say they will pay to have them refinished.

BUT!!

My Pilot Sports were shot at 15k miles, so I went with the Sumis. I love the tires - "All Season Ultra High Performance" should work well in our Illinois winters.
They are also non-directional so you can rotate them.
Another neat feature is a little lip that (hopefully) keeps you from curbing the rim.
*ahem* That assumes that the tire shop doesn't destroy the rims first.

Noise is comparable to the PS's. Traction is pretty good, too - but not quite as good as the Michelins.

hey I also want that tire. Can you tell me how it performs on dry road? Is it comparable to michy?

Yes, on a dry road it is almost as good as the Michelin - I say almost because the Michelin was very very sticky.... and that's why they're $250 each and only last 15k miles.
The Sumo is 90 percent as good for half the price (or less). AND, it's all-season.

I know a lot of you guys have done tire/wheel mods: Sedans and non-C7 Coupes.
Can anyone honestly tell me if by going to Performance tires from the factory std All Season tires that there was an increase in tire noise and a decrease in comfort.
As an 'old fart' I want my cake and eat it too.
So please; no playing in this sandbox if you have a C32 AMG, Sports package sedan or a C7 packge Coupe?

Thanx

P.S.
Luke at the tirerack tells me I can't use their test results as that would be comparing 'apples' and 'oranges'.

If I understand your question correctly, you want an OEM size tire that has better performance and less noise than what came from the factory. Am I correct?

If so, then you might want to try the Yokohama AVS dB. Tire Rack calls this a Ultra High Performance All-Season tire. I had these on my E320 and thought they performed very well for an all-season tire and they were very quiet. Give them a try.

Actually I need to clarify my position. Thanx for pointing that out to me.
I decided to keep my std wheel/tire combo since my wheel deals fell through. They are all seasons (Michelins) and should be OK for my climate in the winter month. But I want to go to 17" performance for the nicer month (mostly sunny but quite often wet). That is where I have my question. I rather not increase my noise and decrease my comfort. Or would I if I were to go this route?

I owned a non-C7 car for 77 days before getting my current car. I didn't notice any change in noise and very little change in ride. Of course, any changes in noise and comfort will depend a lot upon which two tires are being swapped. It is possible that there could be a large increase in noise and decrease in comfort.

Thanx

I was just looking for a generalization. Plus 1 sizing appearently doesn't hurt the comfort whereas the tire brand can affect the noise.
Example:
Right now I got Michelins. I know a lot of people on here don't like the Contis, performance(?) or all-season(?), but MB picked them as OEM. Am I comparing apples and oranges again?

have a C320 that I changed from OEM 16" to 17" C32 wheels with Mich Pilot Sports - there is a big change - half from upping to 17" and hald from the Pilot Sports - I heard they have very very stiff sidewalls..and it seems true...the ride quality greatly diminished - I compare to the C240 loaners I get and it immediatley makes me want to switch to more of a all-season tire with more ride comfort (I don't need a performance tire).

I've heard Kumho 712's are better comfort but not all season and can be "Jekyll and Hyde" tires...some are great some suck.

I'm thinking of the tires on the new E class - Continental Contact all season.

amdeutsch,

I have a 01 C240 - changed the wheels/tire at about 15000 miles from 16's to 17's. I got the staggered set up that is from the C32 - split spoke wheels; 225/45x17FA and 245/40x17RA. I had the Conti OEM Allseason tires as 16 and went with 17" Conti Sport Contact as the initial upgrade. I was really happy with those tires. I dont drive too aggessively, but like my car to handle as well as possible without extensive modifications. I know alot of people do not like the Conti's, but I was not disappointed in them - good dry and wet handling. As I live in AZ, bad weather is not a real problem - other than the summer monsoons. But they handled the wet very well for me. I now have Kumho Ecsta 712. Upgrading to 17's you will notice a slight harsher ride with performance tires. But not too drastic, you will notice some of the bumps a little more. You can also look into performance all-season tires - Michelin and Sumitomo has them. Those are the only two I really looked at - the Michelins are a bit too expensive for me. With regard to road noice - it really depends on road conditions. The Kumhos are notoriously noisy tires, but on certain roads they ride as quiet as any I have had. So, it is hard to judge whether one is generally noisier than another. The route you take is up to you - you can get a performance oriented all-season tire and wont have to worry about chaning wheels/tires when winter come along. But you have that option if you keep your original wheels/tires. I guess it depends how harsh your winters are - if you need snow tires.
Good luck.

I can relate - I too am an "old fart" when compared to the majority of posters here on this forum. But still, I think I am just as performance oriented, but dont want to have my teeth rattled to death!

I guess this boils down to how much performance do you really need vs. how quiet do you want. Even at 17", I still think the Yokohama AVS dB is a good compromise.

Especially for you "old farts"

I had no awareness of all of these tire and wheel related issues before such time that I started researching my most recent car purchase. So, my experience is limited to the last 15 months where I've been paying attention to how different wheels and tires affect the ride and handling of a car. After careful consideration during my selection process I chose to buy a coupe with the 17" wheel package. This was based on the fact that I felt the improvement in handling was greater than the diminishment in ride comfort. Keep in mind that the comparison was made between 16" all season tires and 17" performance tires. I have driven 14,000 miles on the 17" Conti Sport Contacts and have just switched over to 16" Nokian WR for the winter. Based on the range of experience I've outlined I have a generalized assessment. If you use the same type of tire but in the 16" size vs. the 17" size there will be some slight differences. The 16" will provide more compliance resulting in a slightly softer ride. The 17", being both wider and lower, will provide better grip and less lean when cornering and quicker turn in response to steering wheel input. These differences are noticeable but not enormous. The amount of difference in these characteristics will vary if you start comparing tires of different make and model.

This is really great info. Maybe I'll try my tire/wheel combo on ebay (just noticed a set for $510 with reserve not met - should be able to beat that) and then upgrade to all season 17".


From one "OLD FART" to all of you farts , both young and old;

Many, many thanx for the education and help.

For those that have them; what type and size of tire are you using, and if you don't like the tire, what do you want to switch to?

I have 19x9.5 in the rear, and I'm trying to decide if I can size down to a 255 tire.

Toyo T1-S 235/35/19 and 265/30/19. They are WAY better than Pirelli PZeros - price-wise and durability-wise. The Pirellis are excellent on dry, but very poor on wet. Toyos are much better on wet.

I want to try S-03, but they dont make the sizes that I am using. If you go with 255 at the rear, you probably have to go 225 in the front.

I use Yokohama AVS 265/30, it's quite good, i think as i haven't tried the other brand. They are not that noisy and grip is not bad. I'm thinking to switch to Falken when i'm finish with my yokohama. Falken has the thinest sidewall so if u have rubbing problem use Falken instead.

W0n6_3d4n, I see you are using Eibachs; and 19's. What is the offset and width on your rear wheel? Mine is a +35. Because most of us will rub on the rear bumper side instead of the top of the fender lip, I'm trying to figure out the workaound for it. When I look inside the fender there is a bracket that seems like it can't be cut.

My rear wheels are 9 inch width and has an offset of 24 originally but then it was too much so i machined it for 3mm so it's 27 now. Mine used to rub the fender lip then i pull the guard and fully folded the fender lips, now it only scrub the rear bumper, can't even take 2 people at the back