Acceleration Difference between 13" & 14" rotors...
04-10-2006, 12:30 PM
#1
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Acceleration Difference between 13" & 14" rotors...
I'm making my decision tonight wether to go with the Stoptech 14 or 13 inch front BBK with 4 piston cals.. I have a set of 19's with stock 18's in the garage incase I need to inter change for maintenance. I've search many threads and only found one thread that mentioned anything about the extra weight and turning force needed to turn a hugh 14inch rotor vs. the 13inch rotor. Does anyone have any input on this? BTW, the Z is for show only and minimal daily driving. FI will be coming soon, but I'd still like the best set-up to maintain optimal acceleration as well as braking distance.
Thanks,
Val
Thanks,
Val
04-10-2006, 12:55 PM
#3
To get a general idea of how much more inertia the bigger rotor has, you can use a VERY simplified equation,
Inertia = (Mass) * (radius)²
If mass were the exact same, 14² / 13² = 1.16, or about 16% extra rotational inertia.
If the 14" rotor weighs 10% more, 14²*1.1 / 13² = 1.28 (28% extra)
If the 14" rotor weighs 20% more, = 1.39 (39% extra)
This is an oversimplification though, because the disc is not uniform in terms of how its mass is distributed. This is just to give you a rough estimate.
Inertia = (Mass) * (radius)²
If mass were the exact same, 14² / 13² = 1.16, or about 16% extra rotational inertia.
If the 14" rotor weighs 10% more, 14²*1.1 / 13² = 1.28 (28% extra)
If the 14" rotor weighs 20% more, = 1.39 (39% extra)
This is an oversimplification though, because the disc is not uniform in terms of how its mass is distributed. This is just to give you a rough estimate.
Last edited by Wired 24/7; 04-10-2006 at 12:57 PM.
04-10-2006, 01:24 PM
#4
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interesting....
04-10-2006, 01:26 PM
#5
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We always so to go with the smallest rotor you can get away with in a performance application. If you have more heat capacity than you need then you are doing nothing but dragging extra weight around. That being said, on a show application a larger rotor will have a bigger impact and our new 6 piston front setup is only available with a 14" rotor so choose based on your needs.
04-10-2006, 01:38 PM
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Originally Posted by StopTech
We always so to go with the smallest rotor you can get away with in a performance application. If you have more heat capacity than you need then you are doing nothing but dragging extra weight around. That being said, on a show application a larger rotor will have a bigger impact and our new 6 piston front setup is only available with a 14" rotor so choose based on your needs.
I believe I will be comfortable with the 4 piston application. At first, I was mainly concerned with the amount of gap the 13inch rotor would leave with my 19's. I have 547R HRE's. They have a whole lot of open space between the spoke design, and I was hoping to have something behind it that could be admired. Then later on I started to take into consideration how the extra inertia effect the overall acceleration of the vehicle. Even though it's a show car, I still do not want to hinder its ability to show some umph! Tonight I wil be using the Stop tech templates to measure the clearance for both the 18's and 19's. I was already assured by Jeff @ Stop tech that the factory 18's will have no clearence problem. I'm assuming the 19's will not have a problem, but I will double check to play it safe.
04-10-2006, 01:47 PM
#7
I don't know man, you will have plenty impact with 13" rotors IMO.
The average "Joe car enthusiast" on the street will see a BBK, but is not going to pull out a ruler and ask whether its 14". Same thing with 6 pot vs 4 pot. IMO, for show, BBK is BBK whether you spent $4k or $10k
The average "Joe car enthusiast" on the street will see a BBK, but is not going to pull out a ruler and ask whether its 14". Same thing with 6 pot vs 4 pot. IMO, for show, BBK is BBK whether you spent $4k or $10k
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04-10-2006, 01:49 PM
#8
Originally Posted by Wired 24/7
I don't know man, you will have plenty impact with 13" rotors IMO.
The average "Joe car enthusiast" on the street will see a BBK, but is not going to pull out a ruler and ask whether its 14". Same thing with 6 pot vs 4 pot. IMO, for show, BBK is BBK whether you spent $4k or $10k
The average "Joe car enthusiast" on the street will see a BBK, but is not going to pull out a ruler and ask whether its 14". Same thing with 6 pot vs 4 pot. IMO, for show, BBK is BBK whether you spent $4k or $10k
That's on a show car perspective.
04-10-2006, 02:10 PM
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Originally Posted by Kolia
I agree. But I think that "visually", if you're running 19in wheels, you'd better go with 14in rotors. Too much void otherwise.
That's on a show car perspective.
That's on a show car perspective.
04-10-2006, 06:21 PM
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Val, I might be able to answer some of your questions.
I recently switched from stock front brakes to AP Racing's 14.25" 6 piston kit. The AP kit is noticeably heavier than the stocks when picked up but when it is installed, it doesn't feel like the car is slower acceleration-wise.. steering is a tad heavier and I noticed it right after the install.
Since I purchased this kit for auto-x and tracking, it was the perfect setup for me and I couldn’t be happier. Since you are going to go ‘show’ you are better off with the 14” so you can fill in more of the gap.. have you also considered the Rotora, Greddy and Endless kits as well?
Here is the pic with what a 14.25” looks behind spoke’d 19” wheels.
I recently switched from stock front brakes to AP Racing's 14.25" 6 piston kit. The AP kit is noticeably heavier than the stocks when picked up but when it is installed, it doesn't feel like the car is slower acceleration-wise.. steering is a tad heavier and I noticed it right after the install.
Since I purchased this kit for auto-x and tracking, it was the perfect setup for me and I couldn’t be happier. Since you are going to go ‘show’ you are better off with the 14” so you can fill in more of the gap.. have you also considered the Rotora, Greddy and Endless kits as well?
Here is the pic with what a 14.25” looks behind spoke’d 19” wheels.
04-11-2006, 06:17 AM
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Originally Posted by fahrenheit350
Val, I might be able to answer some of your questions.
I recently switched from stock front brakes to AP Racing's 14.25" 6 piston kit. The AP kit is noticeably heavier than the stocks when picked up but when it is installed, it doesn't feel like the car is slower acceleration-wise.. steering is a tad heavier and I noticed it right after the install.
Since I purchased this kit for auto-x and tracking, it was the perfect setup for me and I couldn’t be happier. Since you are going to go ‘show’ you are better off with the 14” so you can fill in more of the gap.. have you also considered the Rotora, Greddy and Endless kits as well?
Here is the pic with what a 14.25” looks behind spoke’d 19” wheels.
I recently switched from stock front brakes to AP Racing's 14.25" 6 piston kit. The AP kit is noticeably heavier than the stocks when picked up but when it is installed, it doesn't feel like the car is slower acceleration-wise.. steering is a tad heavier and I noticed it right after the install.
Since I purchased this kit for auto-x and tracking, it was the perfect setup for me and I couldn’t be happier. Since you are going to go ‘show’ you are better off with the 14” so you can fill in more of the gap.. have you also considered the Rotora, Greddy and Endless kits as well?
Here is the pic with what a 14.25” looks behind spoke’d 19” wheels.
I have looked at some of the other brands, and favor the stoptechs primarily because of the caliper look, sale price I was quoted, & the wide variety of pads available. I was also impressed with their tech support(Jeff) when I called asking questions.
Last night I cut out the cardboard templates for the 13 & 14inch rotor w/caliper, and placed them inside the rim. The 14 was more noticable. You have to use imagination and figure that the "hat" portion of the rotor is significantly more noticeable when it portrudes out futher from the center lug pattern. BTW, I found a screw stuck in my tire.
04-11-2006, 06:20 AM
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Originally Posted by TruBluZ
brakes...
04-11-2006, 06:38 AM
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Originally Posted by vo7848
Albert, nice set up. That's the kind of space I want to take up. Are the calipers 32mm or 35mm in width? When you say the steering changed, I imagining it feels more firm because of the extra drag?
I have looked at some of the other brands, and favor the stoptechs primarily because of the caliper look, sale price I was quoted, & the wide variety of pads available. I was also impressed with their tech support(Jeff) when I called asking questions.
Last night I cut out the cardboard templates for the 13 & 14inch rotor w/caliper, and placed them inside the rim. The 14 was more noticable. You have to use imagination and figure that the "hat" portion of the rotor is significantly more noticeable when it portrudes out futher from the center lug pattern. BTW, I found a screw stuck in my tire.
I have looked at some of the other brands, and favor the stoptechs primarily because of the caliper look, sale price I was quoted, & the wide variety of pads available. I was also impressed with their tech support(Jeff) when I called asking questions.
Last night I cut out the cardboard templates for the 13 & 14inch rotor w/caliper, and placed them inside the rim. The 14 was more noticable. You have to use imagination and figure that the "hat" portion of the rotor is significantly more noticeable when it portrudes out futher from the center lug pattern. BTW, I found a screw stuck in my tire.
Not too sure if you meant rotor thickness since they are 32mm. I don't know the caliper thickness off the top f my head. Steering feels heavier now (maybe even firmer like you said) because of the added weight. I am starting to like it more and more.
Sorry to hear about the screw.
04-11-2006, 07:18 AM
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Originally Posted by fahrenheit350
Not too sure if you meant rotor thickness since they are 32mm.
04-11-2006, 05:22 PM
#16
Originally Posted by vo7848
Hey George, yeah, I'm gonna bite the bullet and burn a hole in my credit card. Haha! I've saved up have of the money for the purchase already, so charging the other half won't be too bad.
Last edited by TruBluZ; 04-11-2006 at 05:25 PM.
04-12-2006, 09:25 PM
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I'm also in the market right now for a BBK. I'm going to go with the Stoptech 14" 355 4 wheel kit in red and drilled. It just looks to good too pass up.
04-13-2006, 09:04 AM
#18
the stock brembos give plenty of braking power if you use some good pads and better rotors like the stoptech aerorotors, some SS lines and high temp brake fluid
it won't quite match the 14" stoptech BBK though in terms of going to the track and driving for a solid hour, or if you're a pro and are running race tires, but it'll weigh less which improves accelleration and handling and of course is good on the street
I noticed a nice difference when I went with the aerorotors - 1-2 lbs lighter up front each and 2 lbs lighter in the rear each
I just can't STAND when people get 20 inch wheels with the base level brakes - tiny rotors, huge wheels. It just advertises the car is a flake
it won't quite match the 14" stoptech BBK though in terms of going to the track and driving for a solid hour, or if you're a pro and are running race tires, but it'll weigh less which improves accelleration and handling and of course is good on the street
I noticed a nice difference when I went with the aerorotors - 1-2 lbs lighter up front each and 2 lbs lighter in the rear each
I just can't STAND when people get 20 inch wheels with the base level brakes - tiny rotors, huge wheels. It just advertises the car is a flake
Last edited by sentry65; 04-13-2006 at 10:25 AM.
04-13-2006, 09:44 AM
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Originally Posted by lex350
I'm also in the market right now for a BBK. I'm going to go with the Stoptech 14" 355 4 wheel kit in red and drilled. It just looks to good too pass up.
04-14-2006, 02:03 PM
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if you can notice the difference in how your car accelerates with 13 vs 14 inch rotors, then more power to you....you will not notice a drop of difference
Steering on the other hand does differ - and for the better IMHO
Steering on the other hand does differ - and for the better IMHO
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