Re: BRAKE Question - 10.1 or 11 on a mk1?

[nocones77-vw@yahoo.com]

I was just about to reply with pretty much the exact same info, but then I saw
Ron's post. Thanks Ron. :)

I use un-vented 9.4" front brakes and stock drums on the rear. No issues on the
street or autocross. I would at least put vented rotors in if I were doing a
track day. 10.1 might be in order if I were serious about road racing, but I'm
pretty sure 11" brakes are unnecessary. That's my opinion on the situation. So
if you're making 4x the power of a stock Mk1 Scirocco and you're doing track
days, you'll want vented/bigger brakes. If you're not increasing power by 400%
or not doing track days, well...at least it will still look cool.

The only reason you might see Wilwoods and/or 10" brakes on my car is because
you can actually build a system that is significantly lighter than the OEM 9.4
solid setup with heavy cast rotor hats and calipers. I'd be going for reduction
in unsprung weight more than anything else. I'm actually trying to see if I can
find aluminum hats and 9.4" rotors, but it seems like most out there start at
10".

Remember that weight is typically a much more important factor than power when
it comes to brakes. Yes, more power means you go faster which means you need to
dissapate more heat under braking, but you need a LOT more power in your
sub-2000lb Mk1 Scirocco to make it go fast enough to match the requirements of
a stock Audi 5k that weighs a lot more (3000lbs? Something like that).

For further evidence, I believe Ben Rogowski's (some of you know him) GT4
Rabbit uses 9.4" vented rotors. They *may* be 10.1 but I'm 95% they're not. It
uses 4-piston Wilwood Dynalite calipers and still fits inside a 13" wheel. Now,
obviously the Wilwoods help a little with heat dissipation in the caliper. But
rotor heat is still the driving factor, and those are damn small rotors on a
dedicated road-race car with a Drake Formula Super Vee engine that probably is
somewhere north of 180whp. That car was purpose-built for hard-core road
racing. No issues...

Last points regarding the fact that the 10.1 and 11 use the same calipers/pads:
If you actually do need more braking power, diameter really *DOES* matter. A
lot. Even if you keep the caliper and pads the same, you're not only increasing
heat sink mass in a larger rotor, you're also making a significant change to
the moment arm that the caliper is working on, which means it takes far less
pad pressure to exert the same force on the spindle, so there is more heat
dissipation AND it generates less heat to start with. Double-plus-good, even
with no change to caliper or pad.

(For the hard-core: Carrol Smith writes good books)

Neal
'77 Scirocco
235whp, 205wtq, and unvented 9.4's :)

--- Ron Pieper <rapieper@yahoo.com> wrote:
> FWIW, in autocross, anybody who's serious (with half a brain) is using 9.4's.
>  Some are even using
> *unvented* rotors. They stop the car fine, but granted, they don't get too
> hot in autox.  Still,
> there ain't much weight to pull down.  10.1's are more than fine.
>
> Ron


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