FD Mythbusters: Brake master cylinder stoppers
 

Hey everyone -

One mod I've always been interested in is a brake master cylinder stopper. These are quite common in Japan - the principle is when you hit the brake pedal, the firewall deflects a certain amount. The stopper braces the master cylinder against the shock tower, restricting movement. This should give better brake feel.

Big problem with this mod is it's only for right hand drive cars. Since the brake master is on the opposite side of the engine bay, the bracket wouldn't work. I've even talked with a buddy who has an import shop (Fighters Garage, here in town) about making these brackets. We did some experiments on his 240sx and my car with a dial caliper to measure deflection. Pumping the pedal, you do have noticeable movement - the FD had about 2/3s to 1/2 as much movement as the 240 did.

Anyhow, fast forward to this week. "Delubozparts" (some dumb name like that) on Ebay is selling master cylinder stoppers, and it actually said "US Spec" in the text. I decide to take one for the team and buy one to try it out - $35, so it's not that big of a chunk outta my side :).

I get the kit, and unfortunately it is for a RHD car. But, the good thing is the primary bracket actually fits just right if flipped upside down, and I just had to fab a small bracket to keep it located. Done deal.

Went over to my buddy's shop and we re-did the test and measured the movement again - this time, the movement was negligible. So, it's doing what it should be doing.

The result? Pretty much no difference in brake feel. In day to day driving, you just don't press the pedal down with enough pressure to deflect the assembly. You have to apply quite a bit of pressure to get the effect, and even doing some hard kick-in-the-ABS stops, I didn't see enough of a difference for it to be worthwhile.

If you built an FD for track use, MAYBE. But, really, all you end up with is about 1/8" less pedal travel - I think the sole of your shoe would probably deflect more than that!

I do think this doodad might work on other cars with more sloppy and flexy frames, but the FD is stiff enough where it just doesn't make that big of a difference. Save your money for something more important.

Attached is a pic of it on my car. It'll be coming off in the near future if anyone wants it :).

Dale

Exactly. The car already has power brakes so it doesn't take as much pedal pressure to lock the tires (or activate ABS) and unless the firewall structure were already woefully inadequite you won't notice it. Reinforcing the firewall in the master cylinder and pedal mount area is common for racing cars with manual brakes though. If the firewall is moving much then strengthening it will do the same thing for the brakes that adding a front strut tower brace does for the steering.

Interesting stuff, Dale. I've never heard of a brake cylinder stopper, is it a Nissan thing? I'm glad our cars don't benefit from it, as any engineer worth their salt will design a very large factor of safety into the braking system. When is the last time you've heard of a brakes-related failure in any vehicle?

-s-

I like the title of this thread, "FD Mythbusters." There are several of them floating around about this car. Recently Sport Compact Car had a cover article entitled, "The Truth. Tuning myths busted wide open." It should be a must read before you start spending big $$$ on modifications.

I've never heard of this thing either, but thanks for the field test Dale, good stuff.

Thanks for " taking one for the team". I think you have too much time on your hands :D.

It's not caught on in the US, but is quite popular in Japan - they do have FC and FD versions. I think this just falls into the neato gimmick category.

If you wanna see the hardcore, check out AutoExe's full brace for the RX-8 -

http://www.autoexe.co.jp/car/RX-8(SE...age/MSE495.jpg

That will protect your brake master in event of nuclear attack :).

Dale

I think it's really one of those Japanese robot dogs.

heh, thanks for doing this dale. . . i was gonna fab one up myself and see if it worked. guess i can dedicate that attention elsewhere now. . .

i think it would be a better benefit to take your shoes off if you are looking for the most brake feel. :)

But this is a good topic and good find too. Good luck Dale.

yeah I have heard of this crap. makes sense on a Indy or f1 car to tie down the pedel set more than a flimsy CF body can. But really, our fire walls are build for i little more than a 50# foot force,; the intend is to takeout vague and nonlinear springyness. Start with the pads, then rubber lines .. change to steel braided teflon lines and stop there before you determine that the pedal arm itself is deflecting and well as the seat mount, seat back and soles of your shoes. GMAB .. the FD still has one of the best OEM braking setups in the industry and it is now 13 years old.

haha, that's just overkill

Interesting read.

I just put one on my car, but as you said can't feel any difference.

that thing is impregnable! never heard of this mod. Interesting.

For track driving, I could see a BMC stopper making sense. The idea is similar to braided stainless steel lines: pass as much fluid to the caliper as possible in a consistent manner for any given pedal effort. Also similarly, I haven't noticed SS brake lines making a difference in daily driving. It's really only when I push hard enough to almost lock the brakes that I notice the difference. I figure it's the same with a BMC stopper (I don't have one, so I don't have first-hand experience with the stoppers).

Also, have you measured if there's any side-to-side deflection of the master cylinder when stepping on the pedal? In some cars, there's also some side-to-side movement when depressing the pedal. Consequently, some manufacturers make the stoppers as brackets that somewhat wrap around the cylinder to prevent that movement.

The RX-8 brace looks interesting, I've never seen anything like that before!

saw this right before i read this thread, actually, thought id throw em up

Cusco
http://homepage2.nifty.com/7mania/tuning/MBSkit.jpg
http://homepage2.nifty.com/7mania/tuning/MBSkansei.jpg

That Cusco brace is IDENTICAL to the Ebay one I bought, save for the one I got being chrome plated instead of blue powder coat. Even the bolts and the little red cap to press against the master is the same.

Dale

Oh, on side to side movement - there was none I could see. The forward movement is VERY visible. You can even see it yourself - pop the hood, stick one foot in the car and pump on the brake pedal while you watch the master. You can see it move.

Dale