rijowysock

on the front calipers...

the 997.1 is not perpendicular to the ground (more about 75* from the ground)

the 997.2 is perpendicular to the ground

i would assume the 997.1 they were trying to lower the mass of the front large calipers? but with 997.2 it didnt matter? i say this because i notice they care very much about where weight is on the car (the tool kit is flat on frunk versus upright.)


-Riley

Nizer

Not sure anyone has answered this question yet. The change resulted from a change in uprights between 997 MkI and MkkII GT3's. This is why most brake kit upgrades for MkI won't fit MkII without a change in uprights.

sin911

Interesting question, I would like to hear some more theories/explanations. Subscribed!

Larry Cable

As I recall much of the suspension changes on the .2 were motivated by the work done on the GT2.

The best theory I can come up with is that raising the CoG on the front of the car might benefit the turn in? but this is just a SWAG and not based on any science ...

911SLOW

Very good!

How about also adding the following scientific proven possibilities

1. looked better to the attending engineer
2. New bracket uses 12grams less metal and saves Porsche 2341USD per year
3. Random act related to Chaos Theory

TRAKCAR

996FLT6

They screwed up on the 997.1 uprights : ). Mike

adrial

The location of the brake caliper affects the loading into the wheel bearings.

Moving the caliper around can change whether the loads induced by the pad dragging against the brake rotor adds/substracts from all the other loads induced in the bearings.

This could have had something to do with it ... but only the Porsche engineers really know.

Getting all the weight as low as they can always matters, they likely found some other small improvement that you, the end-user, won't notice.

Antonov

Chris Harris stated in one of his reviews that they lowered the polar moment of inertia in the front resulting in better response. That doesn't really make sense to me, and I usually take journalist's engineering explanations with a grain of salt, even from CH.

What does make sense is that they lowered the CG without lowering the RC (effectively what RSR uprights accomplish).

Chances are that due to these changes, they had to slightly move the caliper mounting points.

.02

rijowysock

i know the .2 cars all have changed suspension (mostly in front end) which i DID notice in my non GT3 (997.1 was very flighty in the steering department ESPECIALLY under deceleration) my 997.2 has much better steering response.. but i never really thought about location of caliper in regards to bearings and such but it makes sense.

i have not checked non GT3 to see if the caliper position is different, just noticed a .1 and .2 next to eachother at dealer both with non-PCCB but different caliper locations.

nwGTS

Rise dead thread! Rise!

The location of unsprung mass aft of the front hub will affect dive angle under hard braking. You can either move fore mass down or aft mass up to lower front end dive (all else being equal).

Elephant racing offers spacers on their adjustable thrust arm to lower the thrust arm position and angle relative to the front suspension subframe in order to lower the amount of dive. Moving the caliper up on the aft side of the hub would similarly help this. I don't have the data to tell how much it helps but basic suspension geometry says this is something that would change with moving the caliper around. Hope that helps.

matt33

Position aside... are the .1 and .2 calipers identical? (with 28/30/32mm pistons)

Fisher

PCCB calipers on my 997.1 measure 3 degrees lower than vertical.
This thread seems to be relevant to only 997.1 cast iron rotors, rather than all 997.1 GT3 brakes.

997_rich

A few thoughts on the above

• bearing force.. this is one i never thought about (because the bearing is 360 deg that same) but i guess there is a lateral braking force on the axle (the momentum of the car) and there is also the load of the car.
• As for polar moment of inertia.. that seems plausible. But if the porsche engineers are going this crazy to optimize that factor I'd be surprised. It's a VERY small gain in lower polar moment of inertia

I'll throw out a few possibilities:

• Cooling- the calipers are in a better location for ducted cooling. I'm sure there is a focus on brake cooling
• Water ingress- better position so they don't get flooded in the rain.
• Caliper mounting ears are in a better place that allows them to be beefier/more-resonant or use less material, Brake feel and lightweight are often key factors to optimise.
• Allows for shared use of parts across several models or takes advantage of new parts available. This is often another goal in all of product development. They may be trying to use the same brake line or something across all of the models. Or maybe they're cutting to a new brake line on the next Gt3 that was already done. Or maybe the uprights are also used on some other model that had some constraint that drove the change.

rbahr

As food for thought:

The 996 GT3 has the front calipers basically perpendicular to the ground. The 996 GT3 RS (homologation for the 996 RSR) has the front calipers roughly 45 degrees off the perpendicular. This was (allegedly) to lower weight.

Ray