Im thinking about getting some 17" rims for my 5th gen. Will it rob a lot of power since the axles are turning bigger rims/wheels? Also wouldnt it mess up the milage and the speedometer since they are set to calculate speed and milage using 16" wheels?

 

bigger rims = smaller tires
then it will be fine

 

Short answer: search. GREAT explanations have been given on this before, countless times.

Nice answer: yes, it will slow you down a bit. It's not too much, though, IMO, and you will corner much better.

If you use the correct size tire, your speedo will not be affected.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus &raquo;</TD></TR><TR><TD CLASS="quote">Nice answer: yes, it will slow you down a bit. It's not too much, though, IMO, and you will corner much better.
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cornering will only be improved if you're on mushy tires that will benefit from the smaller sidewall of a low profile tire. if you were on azenis, for instance, the 45 series vs the 50 series is pretty close in rigidity and wouldn't make much difference either way.

17's will be ok.

 

what about it messing up my milage and speedometer

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lancer &raquo;</TD></TR><TR><TD CLASS="quote">what about it messing up my milage and speedometer</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus &raquo;</TD></TR><TR><TD CLASS="quote">If you use the correct size tire, your speedo will not be affected.</TD></TR></TABLE>

more weight = less power

 

i've got 18s on my lude! don't worry about your not losing that much.

 

wtf, I just realized I was saying milage instead of odometer. That probably didnt make any sense. Doesnt the car calculate how fast and how far you are going by the rpms? So wouldnt it be different for a 17" rim than a 16" since they have different circumfrences? One rev on a 17" would go farther than one rev on a 16"

 

the rims have a different circumference - yes you are right.

but they do not have the same size tires.

 

higher moment of inertia means less WHP. 17" rims will dyno less WHP is the moment of inertia is higher.

moment of inertia is the weight located a certain distance from a rotating object.

best bet...15" rims with strong sidewall tires.

AKA my set up.

Racing hart CP035 rims with yoko A032R tires.

 

basically, a smaller diameter rim allows for better gearing (i.e. - better acceleration).

 

Wheel size changes your gearing.

Moment of inertia depends on WHERE the wheel's weight is...i.e. more in the center or more towards the rim. Moving weight towards the rim slows you down the most (think in terms of levers).

Short answer, yes, usually larger wheels will slow you down since the gearing ratios are changed and they are heavier. Will it be noticeable? Probably not (unless you drag or autocross).

 

well i guess if your really concerned with losing hp with wheels and tires id say, just get 17's but get real light wheels but that means you'll need a heavier wallet to purchase these. anyone heard of those 8lb magnesium wheels?? those are craaazzzy!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kal &raquo;</TD></TR><TR><TD CLASS="quote">basically, a smaller diameter rim allows for better gearing (i.e. - better acceleration).</TD></TR></TABLE>

hmm, not to nitpick, but smaller diameter tires give you better gearing. the Overall diameter of a 205/50/16 tire is 24.1". The speedometer and odometer use the assumption that the tires are this diameter when they calculate speed and distance. If you were to use a 205/45/16 tire, whose diameter is 23.3" your speedo and odo would be off. The gearing would be shorter as well.

If you're looking for a 17" tire size that is as close to stock as possible, 225/40/17 is exactly the same diameter. 215/45/17 is .5" too big. 205/45/17 is .2" bigger.

bookmark this link:
http://www.miata.net/garage/tirecalc.html

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tribal nerd &raquo;</TD></TR><TR><TD CLASS="quote">well i guess if your really concerned with losing hp with wheels and tires id say, just get 17's but get real light wheels but that means you'll need a heavier wallet to purchase these. anyone heard of those 8lb magnesium wheels?? those are craaazzzy!</TD></TR></TABLE>

lighter is always better, but for braking/accel purposes, a 15lb 17" wheel is not the same as a 15lb 15" wheel. the extra radius length of a 17" wheel makes it harder to start or stop its rotation.

 

one inch more will not make any noticeable difference... Isn't it mostly about weight? Rotating a 30lb wheel compared to the same sized 15lb wheel will make a difference... but 1"? you don't have 19" high profile tires....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matgallis &raquo;</TD></TR><TR><TD CLASS="quote">one inch more will not make any noticeable difference... Isn't it mostly about weight? Rotating a 30lb wheel compared to the same sized 15lb wheel will make a difference... but 1"? you don't have 19" high profile tires....</TD></TR></TABLE>

i actually could feel the difference between a 16" and a 17" wheel, it wasn't mindblowing, but it was there. but in short, no it wouldn't be a big difference. but for some of us on an auto-x course or a drag strip where every hundredth counts...

 

I read an article in a magazine. test was done with the same exact tires....two differing rims.


here it is.


The articile is Wheel to Wheel Shootout Pg 66. The wheels , the Volk Racing TE37-15.5 lbs. and OZ Wildcard-21.6 lbs, wheels look a lot alike. Both are size 17x7.5 and both used hoosier R3SO3 USTCC spec. racing tires. The car used is the Killer Bee Racing Honda Del Sol. On a dyno at 7800 Rpms the OZ's got 152.5 HP and the Volks got 158.0 Hp. On the test track, Laguna Seca with a 5 lap average the OZ's 1:48.48 the Volks 1:47.22. So wheel weight does effect wheel horsepower and track performance.


the difference between a really light 15" wheel and a really light 17" wheel is also night and day difference.

probably more so around 10 WHP more.

 

should I get slower going from 19lb base rims to 16.5lbs 17" rims?

 

its tough to tell.....cause some rims have the weight located closer to the center of the rim vrs. others.

 

I dynoed 181whp and cranked out 2.2 60's with my RacingHart 18"s on 215/35/ZR18 tires. Your not gonna lose jack.