Poor braking performance :S

sailaholic · Postby **sailaholic** » Thu Jun 06, 2013 11:46 am

Further down someone talks about gtx familias using protege boosters on 929 masters. Not sure of the boost the 323 units.

Seeing how much is borrowed from 323s, maybe this is an option.

manga_blue · Postby **manga_blue** » Thu Jun 06, 2013 12:13 pm

Just checked the 323 in the shed. It's a 7/8" with different plumbing. I'll just keep doing background research. The miata.net thread was really good in that it mentioned everything I had always disliked about my brakes but was afraid to talk about. You saw the bit about the "knee" where it initially bites too quickly? :roll:

Maybe I could just follow guran's lead and just get a boosterless master out of a Leyland Mini.

Anyway, glad you're on the way to sorting yours.

stb · Postby **stb** » Thu Jun 06, 2013 2:27 pm

Are you sure about the valve being the right way around? When I did my engine swap I accidentally put the booster hose on backwards and the brakes were effectively unboosted.

dmad_dood · Postby **dmad_dood** » Thu Jun 06, 2013 10:11 pm

Im still having the problem but not as bad now.. i can lock the brakes up but they still don't feel as good as they should be (i think). I think there just taking a long time to bed in probably glazed rotors / pads me thinks. I've got good pressure at the pedal but i'm still gonna do a full bleed. I have real crap feel as well, i have no pedal feel at all.

When cold the brakes are crap but after a few stops they get better - not great but better which is very confusing as the hps are street pads which should work cold?

Im probably going to take the rotors and pads out and give them a good hit with 120grit then re-bed my pads.

Whats the best method for bedding in?

Im also assuming its jsut a matter of the surfaces going dull and im ready to reinstall?

sailaholic · Postby **sailaholic** » Thu Jun 06, 2013 10:24 pm

Yah I did some more reading, it seems hps pads don't get that good a wrap and that they are "designed" to be progressive so don't come in like a light switch. Reading between the lines I take this as they need warming up.

Have you done your booster check?

Hawk have the bedding in procedure on their website.

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dmad_dood · Postby **dmad_dood** » Fri Jun 07, 2013 5:13 pm

Haven't checked my booster yet, perhaps i should before i rip my brakes apart. How are your brakes now? Did u also find a lack of feel?

dmad_dood · Postby **dmad_dood** » Fri Jun 07, 2013 5:27 pm

Just did the test and its all good. Car off, soft pedal until i pumped it up then hard. Started car then waited a min, tired again and soft. Proceed to bleed?

sailaholic · Postby **sailaholic** » Mon Aug 05, 2013 9:42 pm

Manga blue, did you get anywhere with your research, looks like I need to pull the booster so works make a good time to swap.....

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manga_blue · Postby **manga_blue** » Tue Aug 06, 2013 9:04 am

Nothing to report really. I did a whole lot of searching for some sort of vacuum regulator so I could adjust and limit maximum vacuum in the booster unit but found nothing particularly suitable or affordable.

Great minds think alike though. It turned out that Porsche has done that for years.

sailaholic · Postby **sailaholic** » Tue Aug 06, 2013 10:12 am

I wonder if the a booster with a smaller diaphragm could be built / used in the old shell. Might talk to the brake specialists, the might be able to do something tricky.

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MattR · Postby **MattR** » Wed Aug 07, 2013 2:06 pm

Just run without the booster. The m/c size isn't that big that the pedal will be too hard to push. I have quite happily dríven cars with 1" m/c and no booster on the road and track.

plohl · Postby **plohl** » Wed Aug 07, 2013 2:33 pm

I have mentioned a booster delete to him at least a billion times. I think the issue comes when gf's drive said cars.

sailaholic · Postby **sailaholic** » Wed Aug 07, 2013 3:04 pm

MattR wrote:Just run without the booster. The m/c size isn't that big that the pedal will be too hard to push. I have quite happily dríven cars with 1" m/c and no booster on the road and track.

No thanks. As I've said, i HAVE dríven it with no booster and I'm not happy with the performance for (daily) city / road use.

I also think it would be quite difficult to pass through insurance / engineers.

I'd love to do a delete, but I would want to change the master size to compensate. All of which gets more complicated and expensive then I'm interested with at this point.

sailaholic · Postby **sailaholic** » Sat Aug 17, 2013 4:37 pm

I found this that may be of interest to others,

After 97-mxv post about brake upgrades and adjustable proportioning valves not being legal I happened across this today. It would seem that fitting a 1994-1997 USDM ABS proportioning valves or a 2002 non abs prop valve would give more rear bias while keeping things "factory"

http://www.flyinmiata.com/tech/stock_bpv.php

Magpie · Postby **Magpie** » Sat Aug 17, 2013 5:04 pm

I'm going for the adjustable bias but in the engine bay and not in the cab. Due to the ITB's the proportional valve needs to be moved anyway. Thinking about the booster delete if there are other space issues. From research and information exchanges a smaller size master as well as changing the pivot point of the brake pedal may be the right combination.