our stock tires, according to www.tirerack.com do 819 revs per mile. between tire manufacturers the same tire size (215/50/17) vary up to about 10 revs per mile in either direction. is this normal?? why arent the numbers the same for the same size tire?? also, everyone seems to say that putting wider tires on a 17 inch rim (like a 225 or 235 width) will cause your car to be slower...now for example, the sumitomo HTR+ in the size of 235/45/17 do 823 revs per mile. that is VERY close to stock and even a tiny bit smaller in circumfrence which should be a BENEFIT, correct? so you get a benefit of a lower revs per mile and a loss from the new added width of the tire, and presumably the weight of the tire as well. now is it safe to assume that the added traction at LAUNCH will outweight any slow down over the course of a 1/4 mile??? i mean, if youve got stock tires, you can smoke the shit out of them, with better, wider, grippier tires, you should be able to get a better launch, would that launch be enough to outweight any loss the tires would cause? im trying to deside what size tires to go with and i dont want to take a hit in gas mileage or speed and acceleration but it really seems that the 235/45/17 are the BEST match for stock tire size with an increase in width. the 225 width in either a 45 or 50 give a MUCH LARGER margin of error on your speedo and odometer...id rather not have my warranty expire faster than it already will, you guys know what im saying. if your tires are off by an additional 1.5% or more (as they would be with 225/45) then your factory 50k warranty will expire AT LEAST 750-1000 miles too soon!! thats something id rather not deal with....

 

Okay 235/45/17 and 235/40/18 are best fit sizewise... just make sure that you have light weight rims less 1lb/inch... say less thab 17lb for 17" a 15 lb 17-18" Whell would be great!

Now for loss of MPG and Trap speed would be there... In fact, my CLS brakes on its own when lifting off at high speed

I learned that the new Yoko ES 100 has new silica compound to reduce rolling resistance...

 

When I did a miles test, Interstate signs to my odometer, my odometer was reading app. 2.2% more than the interstate signs. I don't think a dealer is going to say 51,100 is over the 50,000 limit.

 

what are you trying to say?? i mean its obvious, 51,100 is a number that is greater than 50,000 and 50,000 is the limit on our factory warranty?? is it not? are you saying we have some kind a grace period after 50k for more warranty work? and if so, what is it?? 1,000 miles? 2,000 miles? 5,000 miles?? there must be a cut off somewhere, and no matter how you slice it, if you decrease the over diameter of your tire, you will approach that # much faster.

 

My dealer also gives the impression that the warranty will be extended as a goodwill gesture for MAJOR mechanical problems if you followed maintenance schedule with the dealer. He mentioned another 10,000 miles

 

It's not that the tire that slows down the car. It's because it takes more horsepower to drive the wider tires.

 

according to my tire calculator website if your riding on 215/50/17 stock and you want to go a little wider i'd personally go with a
235/45/17. it's about 3/4 of a inch wider but Circumference you lose 1/2 inch. overall ride height you lose 1/6 of a inch(which you'd never know). now the best part you DON'T HAVE TO ADJUST YOUR SPEEDOMETER cause lets say with your old tire setup your rolling along at 60 mph with these your rolling at 60.33 mph(it's so small of a difference it's not even worth unbolting the dash for)

 

What I'm saying is that if you are within the tolerance of Tire variance (or show that you have tires that cause the odo to be off, your dealer will take care of it.

 

NO! It seems to be the obvious conclusion that more rubber on the road means more drag.

If you go to a 235/45-17 of identical construction (same materials, rubber, etc) to a 215/50-17, you will actually have less DRAG due to rolling/deformation losses.

AND

At higher speeds (100+ MPH), there is more drag from a wider tire (someone would need a wind tunnel to figure this out and is probably a non-issue for non-open wheel motoring at non-autobahn death-run speeds).

The 235/45-17 and 215/50-17 will have a loaded radius that can be very close to each other (within 1%). The 235/45 has a smaller front-to-rear contact patch and larger side-to-side contact area. Both tires (215/50 vs. 235/45) need to support the same weight of a given car, and less front-rear patch means less deformation in the sidewall (the additional weight is supported by the increased side-to-side area in the 235/45).

This is rather non-intuitive and flies in the face "common sense"...

 

You now know something that a lot of people don't. You can't just go to a calculator and do a figure for a 235/45-17 or 225/40-18, and expect every make and model of tire to have identical section width, tread width, diameter, loaded radius, and or revs/mile.

The construction is different in each tire and different tires have different tread widths.


Your covering so much area that this is what makes "horse racing"...


225/45-17 vs. 235/45-17: The 225/45-17 will make for a lower weight tire compared to the same 235/45-17. The 225/45-17 will generally fit "better" when lowered with wide wheels and with large drops. The effective torque is increased with the 225/45 relative to the 235/45.

You are trading weight, traction and drag.

You are also making a choice regarding speedo accuracy. (And, it might turn out that your speedo is high or low and a given tire will "offset" the error -- it depends).

More stick == more drag.

Narrow tire vs. wide tire + (both with same compounds) == narrow tire with more losses from "deformation"...

You can also get a very sticky tire that is much heavier than a stock tire and that could allow for super stick on take-off, but it could result in higher induced HP losses at higher speeds (due to rotational inertia, deformation losses, and losses due to the stickier compound).

Suggestion:

Make a spreadsheet with all of the parameters you are interested in and "get into it"

At some point, depending on road surface, type of objective (drag racing vs. autocross vs. road course vs. long wear vs. economy vs. under-reporting-mileage) you could end up with very different candidates. (And, I'm not even getting into the area of winter, all-season, and/or 3-season issues).


Finally, when you start getting into the warranty area, that becomes so subjective based on how much you drive per year and other factors (like fun and what is your safety worth), that I just don’t give that issue any thought…


BTW – if you could find a MXM4 in a 235/45-17, it would give you better gas mileage!

Welcome to trade-off world… (the stock tires are very energy efficient and you are going to be hard pressed to beat the economy of those tires).

 

the STOCK tires are expensive as hell!!! at tirerack.com they are 178 a peice!!! holy sheeit!

 

You know, I was just thinking...when your tire wears, doesn't that technically effect the speedo as well? The tire actually gets smaller due to loss of rubber thru wear.

 

sure does, might shrink by as much as 1/3", then again as your tire gets hotter air pressure builds and the tire gets bigger. Go figure.. YMMV