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rear brake heat?

Posted: Tue Feb 05, 2008 3:35 am
by sh0rtlife
on a street car that gets abused how much of a problem is there with heat on the rear brakes?...being im in the proccess of more or less redesigning most of the car anyway im wondering if i should add some ducting for the rears while ive got everything apart....mind you the car went on a HUGE diet and should be under 2000lbs(hopeing for 1600-1800) should be real close to 1800 range

Posted: Tue Feb 05, 2008 12:54 pm
by Alfettish
i doubt there'd be much 0f a problem at all on daily basis. If you were driving fast in the hills or something where there are lots of tight corners and you're driving at higher than recommended speeds, sure, ducting is a good idea. But i think driving around town abusing your brakes isnt'a a very good idea.

Posted: Tue Feb 05, 2008 3:45 pm
by sh0rtlife
i didnt exactly say around town :wink:...and "if" i can id love to put the car on the track a few times ...just wondering if the huge weight reduction would help out with the brake heat at all much ducting is a good idea? like to do my best to retain the stock brake system(well the calipers and rotors anyway since the masters are being replaced with tilton)..

any ideas on what the "ideal" size of ducting would be?....just thinking rather build some ducting into the car while building it than later ...since right now ive got free roam to improvise...since most of the body is off anyway

Posted: Tue Feb 05, 2008 4:31 pm
by Alfettish
Do the ducting mate, it can't hurt and you could show us how you do it here for future reference.

The weight will help but they'll still get hot. My fluid boiled on a hot day after 2 runs of my local hillclimb track and one run lasts less than 60 seconds.

Posted: Tue Feb 05, 2008 5:31 pm
by Greg Gordon
It's a lot easier to add vented rear rotors than it is to put in ducting. Plus it's the factory's solution.

With all that said, I doubt you will ever overheat the stock brakes on the street, but at the track, it's pretty easy.


Posted: Tue Feb 05, 2008 6:44 pm
by sh0rtlife
Greg Gordon wrote:It's a lot easier to add vented rear rotors than it is to put in ducting. Plus it's the factory's solution.

With all that said, I doubt you will ever overheat the stock brakes on the street, but at the track, it's pretty easy.

vented isnt in the budget for a long ways out..and even still wouldnt some ducting help them as well?

Posted: Tue Feb 05, 2008 7:35 pm
by Greg Gordon
I understand the budget issues! I suppose ducting would help with vented rear rotors as well, but I don't have any real data on that.


Posted: Tue Feb 05, 2008 9:12 pm
by Barry
The stock rear brakes are pathetic by todays standards i.m.o.
After really developing the outboard brakes on my Giulietta I would go for big outboards 99/100 times.
The extra weight on the De Dion is easily compensated for by suspension tuning .
The extra braking from the rear far outweighs the std. inboard stuff. 8)

Posted: Tue Feb 05, 2008 10:54 pm
by sh0rtlife
id love to have that kind of budget ..but as it stands i have a shoestring that must be stretched and thin at that....ill be lucky to swing vented's by the end of the year....and actualy i like the inboard brake design for this project....and im FORCED into staying with 15inch wheels no fact 14's would fit soooo much better in the overly tight wheelwells ...the 195 50 15's are a VERY tight fit

Posted: Wed Feb 06, 2008 5:13 am
Two cheap (partial) fixes:

1) Put a heat shield on the exhaust where it passes the left caliper (or right on a Milano). No need for exhaust heat to make matters worse.

2) Use track brake pads and a high temperature brake fluid.

Posted: Wed Feb 06, 2008 3:02 pm
by sh0rtlife
well i use the ate blue brake fluid already in the gtv6 and planed to use the same fluid in the project....exhaust heat shield isnt a bad idea....tho im not sure the exhaust will be routed the "stock" way on this considering making a channel in the body to route the exhaust in a better location

Posted: Wed Feb 06, 2008 11:14 pm
by MD
The stock rear brakes are pathetic by todays standards i.m.o.
Gotta agree there "Mr no muff too tough Barry" :D

Although if you wanna stay in the spirit of the original design ie. inboard, check out my Nissan conversion to 296 x 19 mm vented rotors using alloy callipers and bigger race pads off the shelf.

These are fitted to the "Brick"

Caution, if you are going to go down this track, you will need to modify the De Dion tube and the boot floor for clearance. The caliper bleeder nipples also need to be moved from "inside" to "outside" so you can get your hands on them. And last but not least, you need to cut access holes in the boot floor to install/remove brake pads.

Regrettably, if you are using a GTV6 fuel tank in the boot/trunk, you will not be able to make these access holes.

2nd Caution. These are for a race car and have no handbrake mechanism

If your intentions are not for racing applications, I would go down (not like Barry) :D the path of the out board caliper using something like the Mazda RX 7 series rear calipers that have a handbrake mechanism.

Caliper mounts designed and made by Daniel from this Forum and the rotors were made by Leda Suspension, Brendale. Qld.

Posted: Wed Feb 06, 2008 11:36 pm
by Micke
Didn't realize the disks are so big you must move the calipers out of the way.
Remember they are not in the airflow at all anymore. You must duct air to the calipers not to boil the fluid. Not a big issue and hopefully done already.

3 more blabbering on this topic:

1) the stock rear brakes ARE pathetic
2) they are good enough on the street (even drums are)
3) what on earth is sh0rty driving which has tight in the rear wells with 195/50R15?

Posted: Thu Feb 07, 2008 12:14 am
by sh0rtlife
:lol: :lol: :lol:

technicaly im working on a 87 milano platinum (and i use the word "milano" ever so loosely)
as far as the state government would be concerned im working on a 1958 lloyd alexander TS (still thinking a twinspark would be cool due to the car being a "TS" but i love the v6)

those nissin brake look flat out wicked!!!! :shock: :shock: ..and very considerable but i do need an E-brake as i intend to pretty much daily driver the car and FULLY enjoy the hell out of it....if it turns out as fun as i hope it to be ill probably sell the gtv6 far as cutting the trunk out LOL not an issue as i intend to go fuel cell or make a fuel tank again a rear seat isnt an issue either as there isnt room for one

fear of being chewwed out for what ive done has prevented me from posting pic's or giveing many details to more than a few ppl ...i think this forum can probably handle what im doing as its a little more relaxed than alfabb...since here its all about the transaxle wich my project HAD TO HAVE
junglejustice nows EXACTLY what im working on

ill make a deep explanation post and prepare to be flamed :roll:

Posted: Thu Feb 07, 2008 1:29 am
by MD

This site has a no flame policy so post away..

A little ribbing of course is all part of the fun. Just take a look back and see how many times Jim Greek and Barry have taken the piss out of me and in turn they have received elocution lessons to help them on their way...

It's an Australian quirk to poke some fun but maintain a respect at the same time.


Your 100% right about the cooling. The removable access plates in the floor are targetted as entry points for the air supply but only if I need it. We will do some testing first and see. Our laps are short and the brakes have trouble getting hot enough, so we'll just have to wait and see.