Hi, our 2010 Mazda 6 has 18" wheels, but some have 17".
Does the 18" version have bigger brakes than the 17" version?
Thanks.

 

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A few more facts.
Our Mazda is a 4 cylinder version.
I checked part numbers and the rotors, calipers, and pads are the same part numbers whether the car is a V6, 4, GS, GT, 17" rims or 18" rims.

 

No a car outfitted with 18's from the factory will not typically be outfitted with larger brakes. This is due to the fact that while 18's will weigh more than 17's it will not be catastrophically so. We're not talking about differences of 20lbs even in most cases. My aftermarket 18's that I use for daily driving only weigh in 2lbs more a corner than the stock 17's did (now my race wheels weigh considerably less, but those were bought specifically for their weight...or lack thereof). Thus, it is not necessary for Mazda to spend the extra money to outfit the car with larger rotors, reinforced calipers, and all the extra hardware that goes along with upgrading a brake system. Sorry I didn't see this thread before now.

 

The thing is, those 18" wheels on your car will in fact hurt both your turn-in as well as your braking (and to a lesser degree your handling). Why? Because for every inch you push the weight of the rim portion of the wheel out away from the axis of rotation you incur a geometric increase in the energy required to change its axis of rotation (i.e. to turn it), spin it, and stop it from spinning. That those 18" wheels weigh more than the 17" wheels hurts your performance even worse.

Your race wheels (if they're 18" or larger) will will do the same (even though they're lighter), just to a lesser degree.

 

Nope, race wheels are 17x 7.5 for the reasons stated in your post (and actually I have thought about stepping down to a set of 16's to reduce weight even further and pick up some gearing while I'm at it). I am well aware of the effects the larger wheels have on turn in and braking distance, and I adjust my driving accordingly. Generally speaking though, plus sizing by 1 inch will not mean you will go sliding off the road every time you have to slam on the brakes. Yes braking distance increases, but not by so much that it's impossible, or even difficult to compensate for the change.

My point is simply that the dealership is simply not going to be revamping a car's braking system simply because they put a +1 size wheel on the car. Would it help the car and make for a better overall deal for the consumer? You bet, but it would not be cost effective for the dealership.

 

Ahhh, smart man. I actually know some folks who've dropped to 15" wheels and claim an improvement in lap times. Go figure.

 

If I could run 15's that would be awesome, but I believe 16" is the smallest that can be run on the 6 ( could be wrong on that, but I would think brake clearance would become an issue with 15's). As for actually dropping down to a set of 16's, well I've been eyeing some used NA & NB miata's to possibly get as a track toy/weekend car after graduation and getting a better job.

 

I consulted a few resources I typically use to figure out what wheels will fit any given car and if there are any 15" wheels out there that fit a 2005 Mazda6, I've been singularly unable to discover them. Said another way, I'm thinking 16" is about as small as you can get.

 

Pretty much the conclusion I have come to as well. But as I said, I'll likely pick up a used miata before I do anything else to the 6.