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Discussion Starter · #1 ·
It was very interesting as I was watching this show on Speed Vision (don't remember its name - the one with the fat guy) that they modify cars, add aftermarket components and dyno/track it before and after.
Very interestingly, they modified this Honda, added a Mugen cat-back that is supposed to add more than 10HP and they also put a BIG braking system there with all the bells and whistles.
They actually LOST POWER, dyno was less after the cat-back and brakes! The guys were totally confused themselves and I am actually amazed they even aired the show... they called Mugen and they said they lost power because of the brakes they installed...

On the braking performance side, their stopping distance DID NOT change and their track time was also the same or worse (multiple runs)...

So, this goes with almost what most knowledgeable people were saying on this forum about brakes and why bigger is not always better!
 

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Discussion Starter · #3 ·
Re: Another proof why BIGGER brakes are NOT always best! (gehr)

Quote, originally posted by gehr »
I saw that part of the show......it was interesting......rotational inertia's a bitch

Yes it is!
It just bugs me that people come here and try to go bigger and BIGGER and BIGGER and they don't believe that it's not really doing anything for them and if someone who knows tells them (like for a long time Racer_x) they just say, "so why XYZ did it!"
Oh well, if there are not people like that, many companies would be out of business
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

Racer_X has stated this very same thing over and over. From what I see I'm guessing that 75% maybe more install bigger brakes for the looks.
 

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Discussion Starter · #5 ·
Re: Another proof why BIGGER brakes are NOT always best! (kdiver58)

Quote, originally posted by kdiver58 »
Racer_X has stated this very same thing over and over. From what I see I'm guessing that 75% maybe more install bigger brakes for the looks.

I think so, but they still claim all kinds of non-sense... and companies also advertise and market bigger brakes for performance! I hope one day people learn
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

I've learned my lesson. After reading what people had to say and my observations that the stock brake system and stock pads did 90% of what I wanted it to I've decided to just replace my pads with a pad that will take the higher temps of a track day and not upgrade to the 312mm rotors. I'm going with an extra set of track rotors and pads.
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

If I recall correctly the brake comparisons were done with entirely different weather conditions. It was very cold and rainy after they installed the Stoptech brake kit, and they stated that their was a lack of grip to truly test them. I don't know if this was the same episode you saw. I didn't see any part with dyno runs so I'm not sure. The show is Sportscar Revolution I believe.
 

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Re: Another proof why BIGGER brakes are NOT always best! (Byron N.)

The Big-Brake belief is probably one of the greatest misconceptions about performance parts that I ever see. Kinda like M4d tyte JDM VTEC yo!
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

I'll bet they put some 18" wheels and some Z or W or Y speed rated 215/35R18 tires on it, too. Like that Honda is ever going to go over 168mph (or even 150mph). Right!
This also points out another important detail in building up a car. Make one change at a time, then measure your results. Sounds like the crew on that show was clueless as to which things helped and which things hurt.
In slight defense of the big brakes, I'll bet the wheels and tires they picked hurt performance a lot worse than the brakes themselves. And the tires were probably the big problem with stopping distance (and could have contributed to acceleration problems, both due to weight and grip). But a lot big brake kits require larger than stock wheels to clear, so you get that added penalty in addition to the weight of the brakes themselves.
Still, if you want maximum performance, you want the smallest brakes that you can use that won't fade in your driving situation(s) and the smallest (or almost smallest) wheels that clear those brakes.
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

Quote, originally posted by alexb75 »
It was very interesting as I was watching this show on Speed Vision (don't remember its name - the one with the fat guy) that they modify cars, add aftermarket components and dyno/track it before and after.
Very interestingly, they modified this Honda, added a Mugen cat-back that is supposed to add more than 10HP and they also put a BIG braking system there with all the bells and whistles.
They actually LOST POWER, dyno was less after the cat-back and brakes! The guys were totally confused themselves and I am actually amazed they even aired the show... they called Mugen and they said they lost power because of the brakes they installed...

On the braking performance side, their stopping distance DID NOT change and their track time was also the same or worse (multiple runs)...

So, this goes with almost what most knowledgeable people were saying on this forum about brakes and why bigger is not always better!

How can you "lose power" from the brakes they installed? That makes no sense to me.
Also, why did these dumbasses install a cat-back on a NA car? That does nothing other than add the fart sound.
 

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Re: Another proof why BIGGER brakes are NOT always best! (dcomiskey)

IIRC, that Catback they installed added something like 8 or 11whp.
And you lose power from big brakes (or large / heavy wheels) b/c your engine now has to try and spin all this extra added weight when it accelerates. The engine still puts out the same amount of power, but it is not able to efficiently put it to the ground.
Picture them throwing on a set of 45inch wheels that weigh 1000lbs each and 40inch brakes (that would also be insanely heavy).. Now imagine if they went on a dyno. The engine would barely be able to turn the wheels, thus, "robbing" it of power.
 

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Re: Another proof why BIGGER brakes are NOT always best! (dcomiskey)

Crank HP can increase with whatever engine mods...power to the ground (Wheel HP) will decrease (say if one remains stock or doesn't upgrade those engine mods when adding heavier rotors and/or wheels) with heavier rotors and/or wheels. Kinda like yeah, the ECS Stage 3 big brake front weighs LESS than stock...but the rotors actually weigh MORE than stock...most of the weight savings is from the caliper. The specs are right there...
As was said above...rotational inertia is the issue.
 

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Re: Another proof why BIGGER brakes are NOT always best! (dcomiskey)

Quote, originally posted by dcomiskey »
How can you "lose power" from the brakes they installed? That makes no sense to me.
It all depends on how you measure horsepower. The two easiest and most common methods would be the G-TECH/Pro and an inertial chassis dyno.
The G-Tech pro will show horsepower based on observed vehicle acceleration, vehicle weight and tire rotating radius. So, any losses to inertia in all 4 wheels will show as lost whp.
An inertial chassis dyno also reads hp based on the acceleration of the roller on the dyno. So it will show inertial losses from the weight of the wheels and brakes on the drive wheels as lost whp.
Quote, originally posted by dcomiskey »
Also, why did these dumbasses install a cat-back on a NA car? That does nothing other than add the fart sound.
Actually, a cat back system helps norally asthmatic cars too, just not as much as it helps on a turbo. It also depends on how good the manifold, donwpipe and cat flow. VW's can have fairly good flow through those parts, so a 2" (or 2.25") cat back system will give a bit of extra power over the stock 1.75" (or 2") system.
 

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Discussion Starter · #14 ·
Re: Another proof why BIGGER brakes are NOT always best! (Racer_X)

Ok, just to clarify what they did... got a stock car, dynoed it, did a stopping distance test, and tracked it...
Then added a cat back exhaust, and bigger brakes... did it again. HP shown on the dyno was less than stock and their stopping distance did not change, and their track time also remained the same! So, all that trouble for nothing

They then called Mugen Honda to see why they lost power and they said it is because of the rotational mass of the bigger brakes (not made by mugen) even though the bigger brakes weighed the same as the stock brakes!!!!
BTW, they were NOT trying to prove that bigger brakes cause power loss and they actually tried to justify it somehow...
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I bet in most of the mods people do here, if they do the exact same test, the results will be exactly the same. I see people slam their cars to the ground, get 20" wheels, and huge brakes and biggest exhaust, etc.... I wish they tracked their car before and after to find out that they just got slower



Modified by alexb75 at 10:31 AM 2-3-2005
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

That's pretty lame. Most BBKs don't reduce your stopping distance, contrary to popular belief. The main advantag is for fade resistance. I guess initial logic would tell you bigger brakes = shorter stopping distance but no. Did these tuning idiots try better tires?
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

Quote, originally posted by alexb75 »
Ok, just to clarify what they did... got a stock car, dynoed it, did a stopping distance test, and tracked it...
Then added a cat back exhaust, and bigger brakes...
What about wheels? Same wheels? Or did they "upgrade" to clear the larger brakes?
Quote, originally posted by alexb75 »
did it again. HP shown on the dyno was less than stock and their stopping distance did not change, and their track time also remained the same! So, all that trouble for nothing

They then called Mugen Honda to see why they lost power and they said it is because of the rotational mass of the bigger brakes (not made by mugen) even though the bigger brakes weighed the same as the stock brakes!!!!
Total weight might be the same. But I'll bet it went from heavy cast iron calipers, small rotors to big heavy rotors, light weight aluminum calipers.
Even if the rotors weighted the same, the added diameter will move the weight outward, increasing inertia.
 

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Discussion Starter · #17 ·
Re: Another proof why BIGGER brakes are NOT always best! (Racer_X)

Quote, originally posted by Racer_X »
What about wheels? Same wheels? Or did they "upgrade" to clear the larger brakes?
Total weight might be the same. But I'll bet it went from heavy cast iron calipers, small rotors to big heavy rotors, light weight aluminum calipers.
Even if the rotors weighted the same, the added diameter will move the weight outward, increasing inertia.


Not sure on the wheels... but they didn't mention anything, so I assume it was the same wheels and tires.
You are bang on with second comment, the guy said Mugen told them although the brakes are lighter, but the rotational mass is the problem as it moves the weight outward (just as u said).
 

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Discussion Starter · #18 ·
Re: Another proof why BIGGER brakes are NOT always best! (dcomiskey)

Quote, originally posted by dcomiskey »
That's pretty lame. Most BBKs don't reduce your stopping distance, contrary to popular belief. The main advantag is for fade resistance. I guess initial logic would tell you bigger brakes = shorter stopping distance but no. Did these tuning idiots try better tires?

They didn't try better tires, this just showed that bigger brakes don't help stopping distance.
Also, your point of fade resistance is not 100% true as the most important factor is pads+fluid and if u upgrade those on ur stock-size rotors, you will have no fade!
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

Quote, originally posted by alexb75 »
but the rotational mass is the problem as it moves the weight outward (just as u said).

Yeah...and not in a linear fashion. The moment of inertia goes up
with the square of the radius....
 

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Re: Another proof why BIGGER brakes are NOT always best! (alexb75)

Quote, originally posted by alexb75 »
They didn't try better tires, this just showed that bigger brakes don't help stopping distance.
Also, your point of fade resistance is not 100% true as the most important factor is pads+fluid and if u upgrade those on ur stock-size rotors, you will have no fade!

I think a better term to describe the benefit of larger rotors is added heat capacity rather than fade resistance. I definitely noticed an improvement in temperatures with the 11.3" -> 12.3" upgrade. I doubt it made any difference to my lap times, but its mainly for my peace of mind and not melting off the clear-coat on my wheels!!!
edit: spelling



Modified by phatvw at 1:08 PM 2-4-2005
 
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