Advanced Engineering and Fabrication Discussions, tips, and questions relating to: Performance engineering, design, and theory.

Is a 1" larger rotor worth 2.5 lbs more weight?

Old 12-18-2014, 12:24 PM
  #1  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default Is a 1" larger rotor worth 2.5 lbs more weight?

So I'm on the fence between 11.9" 17 lb and 12.8 19.5 lb rotors for the front and 11.5" 15.5 lb and 12.4 19.5 lb rotors for the back.

All else being equal what's better more rotor or less weight?

Last edited by charchri4; 12-18-2014 at 12:34 PM.
charchri4 is offline  
Old 12-18-2014, 12:39 PM
  #2  
V8 Miata Fanatic
 
Gator Bait's Avatar
 
Join Date: Jul 2014
Location: DFW, TX
Posts: 642
Received 24 Likes on 23 Posts
Default

Are you trying to solve a problem, or fulfilling a want?
Gator Bait is offline  
Old 12-18-2014, 12:42 PM
  #3  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default

Well 2 problems really - 1 practical and one vanity. The car has the worst brakes of any car I have ever driven.


And it looks really stupid with tiny rotors...

Last edited by charchri4; 12-18-2014 at 12:45 PM.
charchri4 is offline  
Old 12-18-2014, 01:52 PM
  #4  
V8 Miata Fanatic
 
Gator Bait's Avatar
 
Join Date: Jul 2014
Location: DFW, TX
Posts: 642
Received 24 Likes on 23 Posts
Default

I don't have either of those issues since I'm on 15" wheels and have 11" brakes front and rear. I've never dealt with the smaller rotors. I can say that as I dialed in more rear brake the stopping got much better. Do you have a manual proportioning valve already?

I doubt you would notice the difference in weight but have nothing to base that on other than an article I read some time back where they did a wheel weight test using lap times as the measure. There was no change.
Gator Bait is offline  
Old 12-18-2014, 02:41 PM
  #5  
V8 Miata Follower
 
Join Date: Jun 2013
Location: OH, the Arctic rain forest
Posts: 115
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by charchri4 View Post
So I'm on the fence between 11.9" 17 lb and 12.8 19.5 lb rotors for the front and 11.5" 15.5 lb and 12.4 19.5 lb rotors for the back.

All else being equal what's better more rotor or less weight?

On a V8 Miata, I would always choose bigger rotors over less (un-sprung weight). Un-sprung weight is only one of the details related to the suspension tuning & there are ways to reduce the effect of the added un-sprung weight. Large brakes & large tires are a very important part of making full use of the available power & torque.

For example: If (2) equally powered V8 Miata's were tested by the same driver on the same road course, (1) w/ small breaks (less un-sprung weight) & (1) large brakes (more un-sprung weight), the car w/ large brakes will set the fastest time every time. The early braking required in order to properly slow the car into turns would significantly slow the car w/ small brakes.

On an Autocross course, the effect of the brakes would be less, but would yield similar results a$$uming that the course were set up to allow the use of the cars' power.

On the street, without question, large brakes are more important.
523-LSX-NB is offline  
Old 12-18-2014, 04:56 PM
  #6  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default

LOL just had a guy smack me up side the head and ask why don't I just fix the brakes I have. If everything was working right they would not be so bad now... Back to the thinking mode...
charchri4 is offline  
Old 12-18-2014, 06:20 PM
  #7  
V8 Miata Enthusiast
 
.boB's Avatar
 
Join Date: Oct 2013
Location: Colorado Springs, CO
Posts: 409
Likes: 0
Received 32 Likes on 26 Posts
Default

For competition, you're better off with the absolute best brakes you can install. Spend the big bux on a Wilwood system. The increased performance and durability are well worth the cost.
.boB is offline  
Old 12-26-2014, 06:34 PM
  #8  
V8 Miata Participant
 
Join Date: Dec 2011
Location: Oakville, Ct
Posts: 344
Received 2 Likes on 2 Posts
Default

Anything that I can do to help stop this car is well worth any weight it costs. Unsprung-rolling-mass-inertial-gyroscopic-Saturn effect BS aside....if it helps to scrub speed and is safe to have on the car I want it. Now if someone could perfect that "Self-repacking" Parachute that the boys over at MI6 were working on for me.....
Meierznutz is offline  
Old 12-27-2014, 12:04 AM
  #9  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default

LOL love to see that! I hung the rear calipers today just to see what they look like and the Camaro calipers would bolt right up if I wanted to use 10" rotors.
charchri4 is offline  
Old 12-27-2014, 05:33 AM
  #10  
V8 Miata Participant
 
Join Date: Dec 2011
Location: Oakville, Ct
Posts: 344
Received 2 Likes on 2 Posts
Default

Jim, seeing that there is a kit out there already (Goodwin has Wilwod 10" rotors that use stock calipers with adapter brackets) why go through the expense and trouble of creating your own kit? Don't get me wrong, if you set up fits I want part numbers, but this is a proven set up.
Meierznutz is offline  
Old 12-27-2014, 09:42 AM
  #11  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default

LOL yeah that would be the easy way! The problem with all the after market set ups is they are very expensive, they all take custom pads, and most of the better set ups have no parking brake.

On the cost I know compared to other cars the $1300 FM or V8R big brake kit is crazy cheap. In F body world that would barely get you one end. But with the parts I have collecting dust I can put V8 Camaro brakes in the car for about 300 bucks and have a real parking brake to boot.

Last edited by charchri4; 12-27-2014 at 09:44 AM.
charchri4 is offline  
Old 12-27-2014, 02:05 PM
  #12  
V8 Miata Participant
 
Join Date: Dec 2011
Location: Oakville, Ct
Posts: 344
Received 2 Likes on 2 Posts
Default

My Goodwin kit uses Wilwood 4 piston front calipers and the stock Miata rear calipers. The two piece rotors are Wilwood and they are 11" front and 10 3/4" rears. I got the entire front/rear set for $850 shipped from a guy that mounted them and never put fluid in the lines. The set I had for Nadine came off a Spec Miata as they are required to use stock calipers and rotors. The deals are out there!
Attached Thumbnails Is a 1" larger rotor worth 2.5 lbs more weight?-rear-brake.jpg   Is a 1" larger rotor worth 2.5 lbs more weight?-rear-brake-2.jpg   Is a 1" larger rotor worth 2.5 lbs more weight?-rear-brake-3.jpg   Is a 1" larger rotor worth 2.5 lbs more weight?-rear-rotor.jpg  
Meierznutz is offline  
Old 12-29-2014, 10:33 AM
  #13  
V8 Miata Fan
 
Join Date: Dec 2009
Posts: 45
Likes: 0
Received 1 Like on 1 Post
Default

Have a factory Mazda sport 11" front brake kit for $250 shipped to your door? It's the factory setup on 00-2003? Or so. I bought for my last miata, new one has em already. I think stainless lines included, along with used rotors and pads. Cheaper shipping if you don't want used rotors and pads. .? Offers?
v8miatanet is offline  
Old 12-29-2014, 10:40 AM
  #14  
V8 Miata Fan
 
Join Date: Dec 2009
Posts: 45
Likes: 0
Received 1 Like on 1 Post
Default

Will trade for someone willing to collect cheap parts I need. I am in Canada, and used miata parts are crazy priced, even from most spec miata racers. Jim, I would be very happy, grateful if you could assemble/collect some of the parts I need, and we work something out.

Heater globes on dash, white ignition sw itchy thing on back of key ign switch, lower front spoiler, maybe sporty suspension bits....
v8miatanet is offline  
Old 12-30-2014, 09:40 PM
  #15  
V8 Miata Habitué
 
Join Date: Sep 2014
Location: Jacksonville
Posts: 210
Likes: 0
Received 13 Likes on 12 Posts
Default

Jim, it is my opinion that the 2 - 4 extra pounds on the bigger brakes will not degrade your track feel or handling enough to overcome the benefit of any significant improvement in stopping power...which is just as valuable in lap times as more engine power.

Where I think you will pay a penalty for the extra weight is in everyday street driving. The car is going to ride rougher and just generally feel less "light on its feet" when the pavement isn't fairly smooth. I lived in Minnesota for 10 years, so I know there is no shortage of "pavement that isn't fairly smooth."

From a pure performance viewpoint, I think the logical question becomes whether the smaller/lighter brakes, properly set up with the right pads (important), will generate enough braking force to nearly lock 'em up with hard pedal pressure, and continue to do so repeatedly within the endurance envelope that defines your hardest driving. The better factory brakes with good pads tend to perform pretty darn well on stock cars, and your car with you in it isn't all that much heavier than a stocker carrying a couple large adults.

I guess my point is the huge rotors would certainly look awesome behind those large wheels, but from a purely performance standpoint if the smaller ones will haze smoke from the tires without undue fade, the bigger ones really can't do much more for you than looking better.

I do totally understand the cosmetic thing; I think the same thing every time I look at my stock '90 discs behind my 16" wheels. Factory Sport brakes and good pads are in the cards.
Sunshine Guy is offline  
Old 12-30-2014, 10:20 PM
  #16  
V8 Miata Participant
 
Join Date: Dec 2011
Location: Oakville, Ct
Posts: 344
Received 2 Likes on 2 Posts
Default

Keith Tanner did a chart on what brake booster/master cylinder/caliper size swaps did to your pedal feel and performance. IIRC the early NA master with it's small volume mixed with the larger NB booster gave the most mechanical benefit as the ratio of foot pressure was amplified. His thought was that you had a "Thinner" window between normal apply pressure and outright lock up so you had to better modulate the input yourself. Surprisingly there was little difference in the caliper size used. I think I will have to find that again as I need a booster and master for my new car soon.
Meierznutz is offline  
Old 12-30-2014, 10:59 PM
  #17  
Jim Stainer
Thread Starter
 
charchri4's Avatar
 
Join Date: Jul 2011
Location: Sunny SW Minnesota
Posts: 2,462
Received 56 Likes on 50 Posts
Default

Thanks guys! Sunshine you are spot on as usual and the car did feel less agile and light on it's feet when I did all the body work and put the big wheels on it. The bigger paws seemed to smooth out the bumps rather than make them worse though. Could be softer side walls or just the bigger radius doing that.

I keep going back and forth between a bunch of options on it. I feel like there is something wrong in the system for it to be so bad. I know the caliper slides and pads are good but really have not done much with the rest of it.

At the moment I'm inclined to go with the Camaro brakes with the smaller of the 2 rotors I mentioned in the first post. But that is primarily because this is mod season I think. Much of the reason for the build is I just like messing around in the garage and trying new things. If it was just fixing the brakes for the same 300 bucks I could replace all the parts in the system. But it's so much more interesting to fabricate brackets and try to make my idea work.

The other thing is I need to buy a wide band 02 and will need tires before mid summer so probably the best thing to do is nothing.

V8miata shoot me a PM and let's talk. I'd be happy to help you find parts and that 11" is an interesting idea.
charchri4 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Braineack
DIY How-to Instructions
19
04-07-2017 10:22 AM
barrattboy72
Exterior Mods
6
04-18-2015 08:42 PM
v8miatanet
V8 Miata Safety, Legal, & Emissions
9
02-06-2014 01:10 PM
chpmnsws6
Site Tips & Suggestions
3
12-05-2012 01:20 PM
rmcelwee
Introductions
10
11-25-2010 09:49 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Rate This Thread
Rate This Thread:
You have already rated this thread Rating: Thread Rating: 0 votes,  average.

Quick Reply: Is a 1" larger rotor worth 2.5 lbs more weight?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.