jgrts20

Ok peeps, Im gonna be upgrading my suspension while the car is in storage for the winter. Im going with this setup:

http://www.racingbeat.com/FRmazda2.htm
http://www.xshocks.com/tokicohp.htm
http://store.summitracing.com/defaul...18101R&FROM=MG

Now a buddy of mine races WRX's and told me when I upgrade my suspension that I should go with 17" rims. Does anyone think this should be done?

I'm currently running 16x7's with 225/55r16's now

Icemark

Actually I would stick with the 16x7 and a 225/50-16 myself for most applications, unless you can find some really light (17# or lighter) 17 inch wheels you will only take a performance hit using 17" wheels over a decent sized 16".

When I race on the track/autoX I actually use 15" wheels myself, I only use 17" for street driving, and even then I use 18# (with Lug nuts) wheels.

And for those that will post (trying to justify their own purchases or ideals) the sidewall difference between using 16 and 17 inch wheel with a 225 width tire is only 11mm... not enough to change any performance in sidewall flex if useing a decent tire.

Syonyk

Why is that? I know that going with too large of a wheel causes bad performance, but... what exactly is it about the lower profile sidewall that affects it?

Also, how do the 15" wheels compare with 14" wheels for autocross & such? Last time I threw the FC around, I was well up onto the sidewalls (with 14s), even with a good deal of tire pressure. I don't think my suspension was helping much, though - I was told I roll like a van out there.

-=Russ=-

jgrts20

So Ice, I should just stick with the 16"s with 225/50. I really dont like the bigger wheel due to the extra weight, but if 17's isnt gonna make a diff then I will stick to the 16's and drop the profile to 50. Oh BTW im running kumo's right now for tires but need to be replaced.

thanx
chris

Icemark

The biggest problem is with the extra weight. Honda published a couple years back that they found for every 5lbs increase found on all 4 wheels (in other words 20 lbs total weight increase on the car) that it robbed 5 HP from the engine in drive line losses.

Toss in the slower response of the suspension with a heavier wheel, and you have a receipe for lower performance.

Now if you went with a lightweight wheel, those losses are minimal, but lets face it... most 17" wheels are 20+ lbs with many of them 25# sometimes even 30#(with some of the cheaper ebay wheels).

14" wheels would be too much of a compromise on a FC. You have to have too much side wall to get the road height.

Again when racing I am using a 50 series tire, this would compare to a 70 series as found on a 14 inch wheel, and a 50 series is more than an inch less side wall than a 225 on a 15 inch wheel. An inch is pretty substantial difference and have considerably more sidewall flex.

jgrts20

well when I got my rims, they weighted 18 pounds w/o tires. My tires are nitrogen filled so they dont weight that much, like air filled ones!! so should I drop to 50's or stick with 55's. I have to replace the tires anyway.

Syonyk

Um... air is something like 78% nitrogen. How is replacing 22% of non-nitrogen with nitrogen going to change the mass of the tires by more than a few grams?

-=Russ=-

jgrts20

Nitrogen is an odorless, colorless, inert gas, meaning it doesn't mix easily with most other elements. Air is about 78 percent nitrogen by volume, and represents most of what we breathe in and out. Chemical No. 7 on the periodic table, nitrogen falls between carbon and oxygen, which accounts for another 20 percent of the atmosphere.

Several benefits flow from maintaining constant tire pressure, including extended tread wear, better fuel economy and improved performance, he said.

There also is evidence that nitrogen offers some other advantages, Unlike oxygen, which mixes chemically with other materials quickly, as in combustion, or more slowly, as in rust, nitrogen won't combine with either the rubber tire or its metal rim.

"The one main purpose of using nitrogen is to stabilize the tire's inflation pressure," nitrogen molecules leak out of the tire at a much slower rate than oxygen."



yea your right sorry!!

Skiles2070

^^ you still have the rotational mass to deal with, that doesn't make any sence^^
am I better off sticking with my stock 14" I love them now and I would really hate to have to change them. but I would for one rim WELD RACING: RACELITE R/S 17X7 only 12lbs. but ofcourse they are discontinued. if you know or see any for sale PM me coast won't matter for those bad boys

RETed

Uh, I don't think they are made for road racing?

The only reason to move up to 17" rims is to run bigger brakes.

Your 225 / 55 / 16 tire size is actually wrong for the FC.


-Ted