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| Q.
How effective is this kit
without using Corvette calipers? |
A. Actually, as you can see from the
test results (click here to go to that page) they are quite
effective. Sure, Corvette calipers look really cool, and there are companies that do
offer that conversion but frankly, you pay for it too! Our goal when we began
R&D into this project was to offer a cost-effective, affordable alternative to the
high dollar systems already available and still provide a drastic improvement in
performance. We don't dispute the fact that PBR (Australian company that makes the
Corvette calipers) are excellent calipers, but we have seen no hard evidence to show that
replacing the stock calipers offer a significant benefit in this application,
especially for a one time stop. If you're autocrossing on a closed road course in
actual competition there may be some aspects we're overlooking, but frankly, we don't know
of anyone regularly campaigning one of these cars yet!
By keeping the stock calipers this makes for a quick, easy troublefree conversion
without the need to break the lines and bleed the brakes. You further save money by
opting to reuse your existing pads if you choose, and replacements are readily available
anywhere. |
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| Q.
What about dual pistons vs single? |
A. Don't make the
mistake of assuming dual pistons are always superior over single pistons!
In fact, the previous generation of these cars (96 and earlier) did have dual piston
calipers. Remember it's surface area that counts, and surface is exponential due to
the square of the radius, so it takes 2 very large pistons to equal the surface area of a
single larger piston. In fact, one of the theories of poor wet weather braking is
that on dual piston vehicles, the pad will flex and trap water in a cupping action between
the dual pistons, allowing the pad to hydroplane; so in some conditions, a large single
piston may be superior. Look at our test results compared to some of the most elite performance
machines out there and you'll realize just how well this 12" rotor upgrade compares!
60-0 in 127 ft is extremely good, much better than the Viper (in fact our stock
setup is better than the Viper!) and right there with the current 'Vettes! |
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| Q.
Why only front brakes?
Don't the rears need to be larger too? |
A. No, the rears are plenty large
enough. On a FWD vehicle especially, the rears provide very little in deceleration
as so much weight transfers to the front. Putting a larger system on the rears looks
great on a show car, but does nothing in the way of performance. We know of no
company that offers rear brake kits for these cars, although you may be able to special
order them for a price! Unfortunately, our 12" rotors cannot be put on the rear,
and we know of no company that offers a 12" rotor for the rears at all.
Besides, putting 12" rotors on the rear will only add to the unsprung weight,
and that's detrimental to performance. |
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| Q.
What about surface area?
Wouldn't larger pads help? |
A. Yes and no. Contrary to
popular belief, larger surface area, to a certain extent, does nothing in reducing
stopping distances on cold brakes. (Cold meaning a first time application
after they have had time to cool.) Larger surface area (i.e. larger brake pads) only
offer more heat dissipation for reduced brake fade under racing conditions. Remember
that the force of friction is merely equal to the normal force (that,
remember from physics, is the force parallel to the pad exerted by the piston) times the
coefficient of friction. Nowhere in that equation is surface area a factor - the
force exerted by the master cylinder is a constant (or rather it depends on how hard the
operator is applying the brakes) and not dependent on surface area, a larger surface area
merely means the finite amount of force applied is spread out over a larger area, but the
force of friction remains the same. Thus for a one time stop, pad size is
practically irrelevant. In theory, a dime size pad will stop a car just as well as a
large one if it doesn't heat up, but we all know in reality, it'll
probally get so hot it'll melt first! What can be said is that pad
size, for a one time stop, need only be large enough that heat doesn't alter it's physical
properties. Only with repeated hard stops under competition use does pad size become
a factor, and then only in reducing brake fade. |
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Actually our stock pads are already rather large. Here is our stock pad (the one
on top - yes, the larger one) compared to a C4 Corvette pad from '84-'88. As you can
see, it's much larger. '89 and newer C4 Vettes did have a slightly larger pad, and
it's comparable to our stock pad. Unfortunately, we did not have available one of
the newer C4 Corvette pads for photos. Based on our studies, we've come to the
conclusion that increasing our pad size would buy us little if any gains. |
| Here our pad is in the middle, with the C4 Vette pad to the right, and a vintage '69
big block 427 Vette thrashed for SCCA & Corvette club racing on the left, which
has the largest pad we've ever seen on a car! As you can see our stock pad is not
much smaller. (As an aside, brake fade is consistantly a problem on the road
raced C4 Vette, probably due to it's smaller pad size. The 427 '69 rarely fades the
brakes, but every season it's pads become extremely tapered at the ends from the force of
its 4 piston calipers and must either be replaced or sanded flat.) So why is the
C4 Corvette pad so small? Perhaps the answer is wet weather braking, as a larger pad
would trap water more easily and cause the pads to hydroplane under certain conditions. |
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| Q. By using the same
pad and just raising it higher to clear the 12" rotor, aren't you not using all the
possible rotor surface? |
A. That is correct and an excellent
observation. However, the area not covered by the pad is toward the center of the
hub, where the moment arm (torque arm) to the center of rotation is minimal. The
majority of your braking force comes from that which is furthest away from the center of
rotation, where the moment arm is greatest (hence the benefit of the larger rotor).
Making a pad larger to cover that innermost area actually does very little good, and
you'll find in almost every vehicle with large performance rotor diameters that the pad
never extends to that area. |
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| Q. What about other
pad compounds? |
A. The latest development in pad
compounds is NAO - non-asbestos-organics. Carbon fiber materials and Kevlar fall
under this catagory. Generally the more noisy the brake (i.e. the more brake squeal)
the more aggressive is the pad; therefore, pad selection is a tradeoff between
effectiveness and noise. Additionally, the more a pad wears the rotor, and the more
brake dust generated, generally the more aggressive it is. NAO pads tend to
insulate more, and not transmit as much heat to the brake fluid, therefore decreasing
brake fade for once the brake fluid boils the brakes fade badly. Also, NAO pads tend
to be softer and will reduce "morning sickness" - a low groan that occurs when
cold. However, NAO pads may also tend to suffer from hot roughness - hot spots that
can cause steering wheel shimmy when hot (making it seem as if the rotors were warped) but
goes away when cold. Our stock pads on '97 and newer GTP/GS are not
NAO, they're semi-metallic. We are experimenting with some NAO pads
and will announce our findings later. |
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| Q. What causes brake
fade? |
A. Brake fade can be caused by
"outgassing" of the pad material as it heats up. Pad materials change
characteristic depending on their temperature, and depending on how they have been heat
cycled. Therefore, some pad materials are good cold, some hot, and some drastically
change characteristics depending on their history and how they have been heat cycled.
Once a pad has been subjected to the point of fade, it's characteristics may
permanently change. This is why it is difficult to find the perfect pad material for
all conditions. Brake fade can also be caused by overheating and boiling of the
brake fluid. |
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| Q. What about
drilling or slotting the rotors? |
A. This was typically done for the
purpose of allowing the gases from a pad outgassing to escape. However, modern pad
materials do not outgas as much as they did in previous years, so drilling or slotting
serves more of a cosmetic than functional purpose now, although there may be some
advantage for wet weather braking. Remember that once drilled or slotted, it's
almost impossible to "turn" the rotors (i.e. put them in a lathe to grind off
high spots to make them flat again) should they warp. |
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| Q. What causes poor
wet weather brake performance? |
A. That's an
often debated question by brake engineers, and there doesn't seem to be a known answer, at
least among those we queried. It is thought that (obviously) water gets trapped
between the pad and rotor, allowing the rotor to hydroplane. It isn't commonly
believed that the pad material has any bearing on this problem. Common approaches to
solving this problem include making the pad smaller (remember how pad size doesn't affect
stopping distance!), and manufacturing pads with slots or grooves in them to allow water
to escape. Sometimes it is believed that certain wheel / brake setup interactions
occur which allow a wall of water to be trapped inside the spinning wheel, resulting in
hydroplaning of the brake pads. |
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