RomanoM

agsid you know my feelings, but FYI:

StopTech will be introducing a 4 wheel brake kit designed for track duty at the next SEMA show. I have that straight from the "horses mouth".

They did one for the 350Z and actually improved braking performance quite a bit. But the 350Z carries 250lbs. extra mass with about the same braking power as the RX-8.

350Z test:
http://www.zeckhausen.com/testing_brakes.htm

Gord96BRG

You're absolutely right - but then the stock rotors and calipers on an RX-8 GT are not at all the same thing as those on a Miata, either.

My point was simply that you can't presume that because VW brakes aren't up to track use that Mazda brakes aren't either. There's no need to plan an expensive brake upgrade until some experience shows that the RX-8 brakes aren't up to the task. It doesn't hurt to do some research, but it's not a guaranteed requirement.

Regards,
Gordon

Sputnik

They don't. There are still mechanicals and trim that decreases headroom.

---jps

agisd

OK I sat in one without a sunroof and it had lots of headroom space. (I am 1.83m tall - 6 ft). I am thinking of ordering one with sunroof. I don't expect any problems with the helmet.

rsowell28

http://www.mazdatrix.com/8brakes2.htm

Factory RX-8 brakes are only single piston.
Check out these bad boys, they look tough!

wakeech

...those're simply larger calipers... i'd wanna see mass specs, and try out more aggressive pads on the stock calipers before going bigger.

PUR NRG

Bigger is not necessarily better. As with all things, proportion and balance are key. 36-24-36...

Read this StopTech article for a better understanding of why slapping larger calipers on can result in worse braking performance.
________
Lovely Wendie99

Mazdatrix

We located this obscure little company called BREMBO, supplied them with meaningless? things like piston diameters, rotor swept area, width, diameter, wheel specs, corner weights, percentages, (all of that was FRONT and REAR), car weight, etc. etc. and asked them if they had a 4 or 6 piston aluminum caliper that would NOT affect the brake balance of the car - as well as meet the other criteria we needed.

We arrived at the 4-piston caliper we are going to use.


btw - No go on a 6-piston -- would NOT work without major changes front and rear.

wakeech

...that's all well and good, i'm just saying we don't have any metrics which prove they're better, yet.

a hit in unsprung weight (supposing they're heavier) might not justify the supposed increase in heat disappation ability.

RomanoM

A caliper transfers fluid pressure through the pistons and pads into force applied on the rotor.

A sliding cast iron caliper does this just as well as a fixed aluminum caliper.

Just getting an expensive caliper does not mean superior braking performance. It will more than likely mean superior pedal feel.

All to often people confuse performance and feel, making the leap that if the brakes feel better they must also be performing better.

Nope.

Brake performance is dictated purely by the unbending laws of physics and thermodynamics:

Vehicle mass, center of gravity, wheelbase, weight distribution, tire friction, brake pad friction, caliper piston area, rotor effective radius (the distance from the center of the rotor to the center of the pad), heat dissipation, heat conduction and heat convection.


In this list the critical parameter is tire friction ( and everything in the suspension that ensures best contact).

Your brakes will produce brake torque. This torque is translated into stopping power by your tires. Once your tires lock-up or ABS is activated any brake torque increase after that is useless.

Therefore, if you have no problems going into ABS or lock-up any money spent on improving brake performance can be better spent else where.

It's no different than having 400lb-ft of torque and trying to put it down on the road in a hard launch through 195 width Pep Boys specials tire. The last 300lb-ft is used to make smoke not acceleration.

And it's not just the tires, but also the road surface. Any tire will have far worse friction on a concrete highway or dirty city street than on a flat, sticky race track.

So, even if you upgrade to some very aggressive summer tires chances are the street your driving on will not allow a very high friction force compared to a race track.

Which is why for 85% of cars driven on the street those $2000 plus brake upgrades are completely wasted money.

If you drive the RX-8 solely on the street or at best around orange cones in a parking lot. Then save your cash. You will not see a performance gain. Especially by changing just the caliper design. Same piston area means same force, no performance benefit at all!


Fade (brake torque loss) is a bit different. But the caliper design is a very small part of the fade equation. If your worried about fade the big things are:

Rotor size and mass, air convection, pad compound material, brake fluid wet boiling point.


Now to feel:

Yes a very stiff caliper like the Brembo will improve pedal feel, probably a lot.

Question is how much is that worth to you?


BTW- Chance are the Brembo caliper (which is aluminum) is 30% lighter or ~ 5-7 lbs. lighter than the RX-8 cast iron caliper. That's the norm, but GET REAL DATA FIRST!

Here's more on brakes:

http://mysite.verizon.net/romano.michael/

I like to thing my stuff on there is good, but please follow the links (especially to the StopTech and DBA site) too.

Mazdatrix

Thank you RomanoM -- I agree 100% with everything you have said.

For everyone reading this thread:
At this time I am not going to claim there will be any braking performance "increase" (we have not even DRIVEN my car with them on -- still need to make the brake lines -- and "increase", on a street car, can be a little hard to pin down).

I have an RX-8. MANY customers and friends have seen it these last few weeks. More than a few have commented on the "ugly / wimpy looking / ONLY single piston? / OLIVE DRAB!" etc. front calipers.

I have been driving real race cars since 1972 (SCCA, IMSA, Trans-Am, etc. - currently driving amatuer SCCA again, and I just won the E/Production race at the June Sprints/Road America - led ALL the laps and set a new lap record). I do not expect any noticeable brake performance "increase" (maybe a firmer pedal?) with these Brembo calipers as the RX-8 (and a LOT of other cars today) should not be anywhere near the "limit" of their brakes while driving on the street. The RX-8 seems to have excellent OEM brakes.

There are car owners out there who purchase rather expensive parts/kits for their cars mostly for an improvement in "looks".
We have already had more than a few inquiries on bigger front brakes. I will be putting the first kit on MY car (along with the drilled and slotted rotors).
They are going to LOOK SOOOO much better than the OEM calipers and rotors.

Dave Lemon --

RomanoM

BTW- FEEL IS IMPORTANT.

A car with 0.95g of lateral grip is good, but only a car with great steering is a GREAT handler!

Think of brake feel the same as steering feel. It makes the whole experience more satisfying.

If all that mattered where pure numbers we would all buy a Mustang Cobra.