Brake fade with new 4x4 4 piston front calipers

[Guest larkja]

I just installed my new 4 piston calipers from Motorsport. It took a while to pull everything off, cut the backing plate and reinstall, but it looks nice (included also were ss brake lines). I have a '73 240z and while at it, also installed a new brake master cylinder. I bled the brakes carefully, front and back, to ensure all air was out of the lines and used Castrol DOT 4 fluid. I went on a couple high speed passes and after about ten 90+ mph hard stops, the pedal was going to the floor - basically, no brakes.

 

Any ideas what might be wrong? Do I need to upgrade the master?

 

Thanks

[blueovalz]

Ten hard 90-to-0 stops will make anything but a good racing set-up feel mushy

[Miles]

I have been considering doing the Toyota brake swap using the MSA kit. Does MSA supply the small hard pipe that connects the caliper to the flex line?

 

Also, has anyone else experienced the problem with the brake pedel going to the floor? Other people who have done the Toyota swap indicate they get about 0.5 in. of slack in pedel travel. Can that extra pedel travel be adjusted out some where in the master cylinder linkage?

 

Thanks

 

Miles

[260DET]

Going to a 15/16" master cylinder helps keep the pedal up when converting to 4 spot fronts. Off a 280Z or ZX, not sure what years.

 

You may need to duct some air in to help cool the rotors if you use your brakes hard.

[Mikelly]

Hold on there tex...

Did you bed in the pads? You can't just go out after installing new components and trounce on them. Average break-in is to drive the car for approximately 300 miles in traffic to allow the pads to bed in properly, unless you have racing pads... I'd guess you glazed the pads. Also, you may need to upgrade your fluid to something that will shed more heat... Also, look in ANY magazine...They all do their testing from between 6-70mphour down to zero... Not 90mph...

 

Mike Kelly

[Modern Motorsports Ltd]

Larkja, you gained some braking force with your setup but minimal gain in fade resistance if pads are similar to previous compound. Those are toyota 4x4 calipers and sounds like you put them on OEM solid rotors. The OEM front solid rotors are relatively light and being unvented they'll absorb and retain heat generated from braking friction quite readily. This heat heads from the brake pad/rotor interface into your caliper and brake fluid, particularly once rotor gets quite hot as the heat will then reach out to any cooler objects (ie. caliper/fluid etc). Your pads will heat up beyond their functional level and your brake fluid will start to boil and thus both reactions (of which you may have only had boiling fluid) result in loss of braking. For further gains put some ducts on your backing plates or duct direct to your caliper if you want to stay with solid rotors.

 

As Terry says it typically takes a higher level brake system to take the punishment you threw at it. Routine pad bedding varies among manufacturers. Typical routine for KVR's is 40mph to a stop (gradual braking) 5 or 6 times, then park it for at least an hour and then all's well after that:)

[randy 77zt]

the stock rotors wont take this abuse with out warping-i have done it on sears point.the 4 piston calipers help but will fade unless you run carbotech or porterfield race pads and then the rotors wont last.get bigger brakes with vented rotors.

[blueovalz]

In the issue that 260DET brought up, the larger master cylinder is from the first year ZX, onward. The earliest ones adapt most easily using the same bolt pattern, spacer, etc, and will provide about 11% increase in firmness (yeah, it's hard to measure firness) based on the piston area ratio between the two.

[Zeventy8]

Before too much time/money is invested, bleeding the master cylinder first, then the wheels once more might be prudent.

[BLKMGK]

Soounds like the fluid boild in the calipers. Did you change the fluid before doing this or simply add for what was lost? If this is the solid rotor conversion the rotor is probably an issue too...

[Guest digitalz]

you need bigger vented rotors if you're gonna abuse the brakes like that.

 

imho the stockers are not up to it. i am upgrading my brakes soon because when we get used to our little toys, we tend to push them harder than they were designed. repeated demands on the little stock rotors will cause them to do bad things.

 

i had toyota 4x4 brakes on cause they were cheap from local napa store. just to shake the bugs out of the conversion about 3k miles now. now it's time for me anyways to get serious for i need to stop as well as i can accelerate.hehe!!

 

do a search, i think alot of discussion about this issue has already taken place

 

kent

[Guest larkja]

Okay, okay, don't shoot me. I picked up some cross-driller rotors and am starting to read that this may not be the best setup. I will also need to pick up some racing pads. When I swapped out the rotors, I found a couple small chunks falling off on the corners. Quite a bit of sanding later, they were okay, but I won't be doing that again.

 

So you guys recommend vented, not the cross-drilled with the 4x4 setup?

 

Thanks

Jim

[Guest digitalz]

cross drilled=cheese graters imo. if they are stock width drilled replacements then very little improvement if any over stock setup.

 

just compare the z-stockers to late model oem performance oriented brake setups, you'll find that 30yr old designed z brakes are not really hi performance imho.

 

check out scca's (mike's) site. lotsa pictures of different setups.

http://www.fonebooth.com/brakes_zcar.html

 

email me if you want install pictures or feedback. i will be putting the stuff on in a couple of days if i have time. i hope....it's mike's stage 2 package with outlaw 4000 calipers. pads area is huge compared to stock stuff. went with the bigger caliper cause only $100 more. when i looked at the specs, there was no comparison.

 

hope this helps you,

kent

[Guest larkja]

Thanks for the info. Please e-mail me your address - mine's jlark@actional.com. Also, I tried scca's link to "Contact Us" and it doesn't work. Do you have his e-mail? I would like to ask him some specific questions re. the brake upgrades.

 

Jim

[Guest Anonymous]

These guys are right. I converted to 300ZX vented using the spacer sold by "scca" (Mike) and the 4-pistons. I also am running 79' 280zx calips and solid rotors in the rear.

 

A few weeks ago (on Valintine's day) I ran all over town hard and fast. I was late for a very improtant date. After 1 hour of riguous hot-rodding I stopped to check my brakes; the fronts w/ the vented rotors were nice and cool , but the rears were roast'n .

 

I would highly suggest upgrading the fronts asap. Use the 15/16" master from a 79' 280ZX (fits like a glove) and it will take almost all the slop out. I can slam 90-0 too, but I'll still keep stopping down the road. Face it, the solid rotors suck. upgrade to vented in the front and slap on some disc's in the rear, it's the only way to ride. But, if you need some solid rotors to mess with you can have mine . Don't worry, it sounds like you are on the right track. I only suggest the best thing on your ride are the brakes. I may not be the fastest out there yet, but I'll be damn'd if I rear-end someone again

 

Nic