ben.farnath

So I've bled them over and over and over. Resleeved master and some new lines. Master was bench bled. With the car off the pedal is firm and feels like a pedal should. As soon as you turn on the car the pedal goes soft as hell. But the brakes work strong as you just have to be super touchy when pressing them. (as in, through the whole soft sloppy pedal feel the brakes do work and work strongly) and I've adjusted the pedal as per haynes specs.

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clokker

iTrader: (2)

The behaviour you describe (pedal goes soft when car is started) is completely normal for a boosted system (brake boost, not turbocharged boost).
We'll assume that the system is mechanically sound and you've bled it properly.

That leaves the "feel" which is entirely subjective.
When I still had a stock brake system, several people complained of "soft" brakes and I've concluded that "feel" was completely intentional, just the way the engineers and test drivers wanted it.
IMO, the FC has woefully undersized master cylinders and boosters- especially if you've converted your base NA from single to four piston calipers.

A smaller MC requires less effort but more travel.
I cannot claim (simply because I never objectively tested it) that a larger MC/booster decreases actual braking distance but it certainly has an immediate and dramatic effect on the way the pedal "feels"...much shorter throw and harder response.

IF the system is bled, IF all the adjustments are correct (particularly the pedal>pushrod adjustment) and IF the mechanicals are sound, then changing the MC/booster is the next step to altering the pedal "feel".

Honda, Nissan, Subaru and even Mazda all have brake setups that are mostly plug-n-play into a FC.

mbonner

Clokker, does that mean the the 88 vert which comes with 4 pot calipers has a larger MC/booster?

clokker

iTrader: (2)

Yup.
The stock NA setup is a single diaphragm booster with a 7/8" MC.
Turbos (and verts, I think) came with double diaphragm boosters with a 15/16" MC.

IMO, optimal size for the MC is either 1" or 1 1/16".

mbonner

How difficult is it to switch to a larger MC on the vert, Clokker?

clokker

iTrader: (2)

Not difficult at all.

I prefer to match my MCs with their original boosters because it eliminates the booster pushrod>MC adjustment.
Something like the Subaru 1 1/16" setup is a direct bolt in, no mods required.
"No mods required" does NOT include the brake lines, they will probably need some reconfig, if not outright replacement, to fit the prop valve.

The FC uses a 10mm input shaft on the booster and our pedal clevis is fairly unique (our cast alloy pedals are wider than standard steel pedal shafts). The Subaru uses the same shaft and our clevis will screw right on.
Other candidates may have an 8mm shaft and the clevis must be modified to fit.
An 8mm Helicoil will screw right into the 10mm clevis thread and makes a perfectly fine adaptor (which is reversible if need be).

ben.farnath

Is the booster from an abs equipped fc(mine was) and a non abs(mine is now) any different. Ie the fact I used my abs booster with non abs master and no abs block, will it make a difference? (deleted abs in other words)

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Th0m4s

I have a S4 TII and I had a S5 TII brake booster lying around some time ago. The two brake boosters were a bit different from each other. The biggest difference were the holes for the brakelines in the master cylinder. Is there any bigger master cylinder which would be a direct replacement for the S4 TII one without having to bend new lines?

clokker

iTrader: (2)

Not that I know of.

The RX

I know this thread is about a month gone, but I was hoping I could get some feedback on the issue of soft pedal work...

Right, so the back story is as follows. Got car, been doing upgrades. Like... a year ago or so I got Hawk HPS', stainless lines, and I'm using a decent brand DOT4 fluid throughout. The discs on the car were OEM Mazda's (woo), and did me a lot of good, with a lot of stops on them. But about two months ago I finally noticed the beginning of some run out occuring. ****. So, saved up, got PowerSlot Cryo treated rotors, and just installed them yesterday. (Incidentally, I've got the four pot brake option, worth mentioning I suppose, haha).

Took the car out tonight, wondering how it'd all come together, and was met with both good and... unexpected results. I did in fact do a brake flush again. And I kept the same HPS pads, as they had a world of life left. Anywho, on the drive I found that while the pedal travel is extremely linear, it's also quite a bit longer a throw, and "softer" than before. They've definitely got the power to stop, but... the bite I was expecting just isn't there.

Points of note, I did bed them in prior to doing my full review on them. I double checked all my lines, and my flush work. Everything kosher there... I'm maybe thinking that the cryo treatment has created such a smooth finish at the molecular level, that it's going to take a bit to mate properly? But that still doesn't explain the long pedal travel... What's weirder, if I stand on them at a stop, they're solid as a rock. While moving, and approaching a braking zone, if I do a couple quick pedal blips, then the feel/throw is better, but by no means like before. And I'll reiterate the point of no air in the system, this is for sure.

So, longest post over, heh. Ideas?

texFCturboII

iTrader: (17)

That sounds normal for a boosted system. Isn't it a testing procedure to pump the pedal and see if the pedal gets firmer?

jjwalker

Verts have the same single diaphram booster and master cylinder as the NA coupes.