IS250 with IS F and IS350 brakes
11-14-10, 04:38 AM
#31
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BBK will not shorten stopping distance on the street. It will however usually feel shorter and the pedal will firmer. On the track it will help dissipate heat, brake fade.
I do get BBKs for my cars, its not rice. Its for looks but theres nothing rice about them.
I do get BBKs for my cars, its not rice. Its for looks but theres nothing rice about them.
11-14-10, 08:05 AM
#32
I'm an engineer.
Guess which of us Brembo, Stoptech, and folks who design brakes for OEM car makers agree with?
(hint: it's not you)
Your IS-F brakes (well, half IS-F brakes) stop you car in exactly the same distance your stock ones did.
While also eating through pads faster, and cracking the rotors sooner, than the stock ones did.
Since you're not tracking the car what you've done is a downgrade from a functional perspective.
It just looks nice... Which is the one thing I agreed with from my first post in the thread.
Once your wheels are locked (or ABS engaged)... which the stock brakes can do just fine, everything is determined by kinetic friction. Which is your tires against the road. Your brakes have no impact whatsoever on braking at this point.
Here's the formula to calculate braking distance-
d = V2/(2g(f + G))
Where:
d = Braking Distance (ft)
g = Acceleration due to gravity (32.2 ft/sec2)
G = Roadway grade as a percentage; for 2% use 0.02
V = Initial vehicle speed (ft/sec)
f = Coefficient of friction between the tires and the roadway
Notice how it doesn't ask about your brakes?
Because as long as they can engage ABS, which again the stock ones can, they don't make a difference
Again, every expert on the topic of brakes (or even basic math) agrees on this. It's been an established fact of the universe since before there were even cars.
I'm afraid "Uh, I'm a mechanic!" doesn't really trump that.
If you'd bother to read the original article I linked you to (written by a guy who designs brakes for car makers) you'd find good explanations of why this is so, and why your car might feel different with brake upgrades, while not actually stopping any shorter.
But then you might learn something, and you're apparently dead set against that.
11-14-10, 07:03 PM
#34
Lexus Test Driver
damn i realli want some big break kits.... =) but i m thinkin about goin with some Project U or Fsport or if someone sellin some IsF ones but my big question for u guys is will it work on a AWD
11-14-10, 07:04 PM
#35
It's physically impossible for such a result. That's why, as I said, even Brembo doesn't bother testing braking distance. Ditto Stoptech, who also will tell you that tires determine braking distance, not rotor size or pad material... Unlike you they understand big brakes don't change stopping distances.
Likewise, you haven't dyno tested a 20 hp gain from the NOS stickers on your car, no matter how confident you are in that either
I know you're pretty new here, but this thread comes up at least a couple times a year... always with some guy who either wants a BBK or just threw one on his car... and every time it does someone has to explain how brakes actually work to him. Do a seach, you'll find 20 more threads that start with this, and all end with the guy with the BBK realizing he's wrong when I or one of the other knowledgeable folks on here explain it to him.
The difference this time is you're not interested in listening or learning anything.
We provide you with detailed explainations, and solid sources, and you're incapable of a more well thought out reply than "Nu uh!"
Which is hardly compelling.
By the way- next time you're going to make up fake "testing" numbers, try more plausable ones.
An IS-F only stops in 112 feet, a 350 in 114 feet, and a 250 in 113 feet. (all numbers from 60 mph, from edmunds.com testing)
Notice how a 15 foot decrease is wholly unbelievable from mis-matched bigger brakes on your 250?
Know why they're all nearly identical?
Because the brake size doesn't change braking distance.
Last edited by Kurtz; 11-14-10 at 07:26 PM.
11-15-10, 08:45 AM
#37
I already know what I think of your brakes... and it's a lot more accurate than what you seem to think... which is kinda sad.
Anyway, hopefully my advice at least helps you next time you decide to make up numbers about fake results you don't have... they'll probably be a little more close to plausible next time.
Some perspective on how silly your made up number is-
15 feet shorter than stock on a 250 would be about 98 feet. Here's a quote from Edmunds.com review of the M3 they did in 08:
In our tests, the M3 stopped from 60 mph in 100 feet, which is the shortest stopping distance we've ever recorded.
Really though, if BBKs actually caused huge improvements in normal braking distance (and a 15 foot decrease in distance on an IS250 would put it into 6-figure supercar territory for braking distance...which you also obviously didn't know when you made up your claims) then you'd see Brembo, Stoptech, and other major brake makers screaming from the mountaintops about the stopping distance improvements their hardware offers for street cars.
Instead they outright tell you that their stuff won't shorten your braking distance in street use. Because unlike you, they understand how brakes work and don't just make stuff up.
The only time they discuss braking distance is in fade tests, which is great info to have for a track car, but utterly useless on a street car since even OEM brakes won't experience fade in normal use... and even then they're generally clear that for the first stop the "big" brakes cause no improvement, and for the 10th stop the distance gets "less longer" than the smaller brakes, not shorter.
Last edited by Kurtz; 11-15-10 at 09:07 AM.
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