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AngryCorvair
AngryCorvair MegaDork
10/8/18 12:23 p.m.

In reply to maschinenbau :

you posted 

and i see two things that are contributing to your poor pedal feel.

(1), with no vacuum booster, you lost a force multiplier of about 7:1, so what used to take 25 lbs pedal force now takes 175 lbs.    and with that much pedal force, the firewall will flex significantly more than you think.  you could be losing up to a full inch of pedal travel due to firewall flex.

(2), those loops of brake pipe that go "up and over" from MC OUT to ABS IN are going to be nearly impossible to bleed.   the volume of each of those pipes is probably equal, maybe larger than, the volume of a full stroke of the MC.  but there may be a solution.  it'll be a little messy, but i think it'll work. 

you'll need a couple feet of tygon (clear) tubing that is a tight fit onto the tubes from MC OUT to ABS IN.   hold both ends of the tygon up in a U shape, and fill about halfway with clean brake fluid.

crack the tube nuts loose at MC OUT, and disconnect the other end of those tubes from ABS IN.

slip one end of the tygon tubing over the ABS IN end of the tube.   tight on the tube, not tight on the tube nut LOL.  zip tie tygon to ABS IN end of tube.

rotate those brake tubes forward in car, up and over the reservoir, until the ABS IN ends are lower than the MC OUT ends.

snug the tube nuts on the MC OUT end.

elevate the free ends of the tygon tubing so they're vertical and higher than the MC.

fill reservoir, and let those tubes gravity bleed.  you'll see air bubbles rising through the fluid in the tygon tubing.

when you don't see any more air bubbles rising, those tubes are bled.

then prop the brake pedal as described below, loosen MC OUT tube nuts and rotate the tubes back to installed position.

remove tygon tubing, install tubes to ABS IN, and tighten all tube nuts.

that should help a huge amount.

maschinenbau
maschinenbau Dork
10/8/18 12:39 p.m.

In reply to AngryCorvair :

Thanks a lot for the explanation. It makes sense to me, but I've been using a Motiv pressure bleeder that holds 15psi on the reservoir. Shouldn't that be enough to push any air out of those tubes? Or maybe the pedal needs to be pumped with the pressure on the reservoir, to force that air pocket out?

Also if I delete ABS tonight with some tee fittings, I could try going under the MC instead of over to reduce the chance of air pockets.

AngryCorvair
AngryCorvair MegaDork
10/8/18 12:58 p.m.

In reply to maschinenbau :

I can't give you a definite answer whether 15 psi should push that air through.

also, if your shock tower won't let the pipes rotate far enough to get the ABS IN ends lower than the MC, you might have to bend them a bit to do the bleed and then bend them back to reinstall.  If bad turns to worse, install a tee at the highest point and put a bleed screw in the third leg of the tee.

NINJA EDIT:  the best fix would be to minimize the length of tube that is higher than MC OUT.

maschinenbau
maschinenbau Dork
10/8/18 9:27 p.m.

Got the ABS deleted and shoved all the lines below the height of the MC using parts store tee fittings two tries of nicopp tubing. My hands smell and feel so bad. But the pedal feels firm with no squish noise, I think? It stopped the wheels from spinning on jack stands a little bettet. I think it's just a real stiff ass pedal. I hope. Idk, gonna sleep on it and rebleed tomorrow, see how it feels then.

I hate brake fluid.

 

Patrick
Patrick MegaDork
10/8/18 9:51 p.m.

Manual brake cars also have the pushrod mounted in a different location on the pedal arm for more leverage so if it’s too stiff you can move the rod up on the pedal.  Ratio is x/y where x is fulcrum to pedal pad and y is fulcrum to master cylinder pushrod, and you’re looking for about 6:1 with a manual master.  

AngryCorvair
AngryCorvair MegaDork
10/9/18 6:59 a.m.

In reply to Patrick :

Pushrod angle into MC needs to be less than 3 degrees off the MC bore axis, or it will wear the piston seals and start leaking in a matter of months.

also, increasing pedal ratio means increasing pedal travel.  Pedal could hit hard stop on floor before max MC pressure can be achieved.  And that's bad, mmmkay?

my recommendation:

EVERY DAY IS LEG DAY!

TED_fiestaHP
TED_fiestaHP Reader
10/9/18 7:11 a.m.

    If to much pedal effort, can change to a slightly smaller diameter master or get more leverage out of the pedal.   True you don't want to much angle on the push rod, at some point would have to move the master cylinder up a little.    When I converted my old fiesta to twin masters, they were slightly to large, had to adjust the pedal leverage.  Not much fun, since you have to remove the brake pedal and modify it then reinstall, brake pedal never fun to remove and replace.

maschinenbau
maschinenbau Dork
10/9/18 7:29 a.m.

I went out to the car this morning after the brake rage of last night subsided. No squishy noise. Pedal stops firmly a lot higher up than before. I think we got something. Still going to re-bleed before test driving tonight.

Gunchsta
Gunchsta HalfDork
10/9/18 8:07 a.m.

Man this thing is incredible. I'm late to the party but I just skimmed through all of it. Naturally I love the box flares. Oh and I think I mentioned it in the rice-rod thread but the Elcamino is gorgeous. 

 

What ever happened with those BBS wheels? Hopefully still lurking around?

maschinenbau
maschinenbau Dork
10/9/18 8:17 p.m.

Thanks! The wheels got left behind with a friend during the move. I can get them back anytime I feel like giving his chop saw back :) 

The brakes work! The pedal really isn't too firm. It needs a bias valve because the rears lock up way too early, but it stops pretty well! I have the valve, but at this point I don't want to mess with it anymore and risk breaking something 2 days before leaving for the Challenge. I'll fix it later, but the car can race as it sits now and I don't want to change that.

Also this machine straight up rips.

Indy-Guy
Indy-Guy UltraDork
10/9/18 8:54 p.m.
maschinenbau said:.

..... Also this machine straight up rips.

Out-Berkeleying-Standing!

Pete Gossett
Pete Gossett MegaDork
10/10/18 6:10 a.m.

In reply to maschinenbau :

Awesome!!! Hopefully the FL panhandle doesn’t get washed/blown away & I can see this in person in a couple days!

mazdeuce - Seth
mazdeuce - Seth Mod Squad
10/10/18 7:15 a.m.

So I was thinking.......this is going to be a multi time Challenge car, yes? If it were me I'd skip the paint and save it for later. Having to try and do nice-ish paint over hastily applied paint is going to suck. Like Pete I can't wait to see this in person. 

maschinenbau
maschinenbau Dork
10/10/18 7:25 a.m.

Yes, definitely coming back next year for a proper Challenge with drags. I still have almost $500 left in the budget for paint, bodywork, and nitrous. I am planning to hit the local strip later this month for test and tune.

I was thinking of rolling on some rustoleum Thursday night, since it'll be raining here all day today and I still need to do my build book. Shouldn't be too hard to strip later. Primer just does not score well in Concours.

mazdeuce - Seth
mazdeuce - Seth Mod Squad
10/10/18 7:38 a.m.

Good point. I hadn't thought that removing the paint would be easy, but I tend to shy away from paint. If you're still making it pretty after dark tomorrow I'll come help you roll some on. The Challenge photographers can make cars look much better than they are as long as they're shiny. 

AWSX1686
AWSX1686 SuperDork
10/10/18 8:09 a.m.

Really sad I decided not to go this year, but I do hope to come back next year, so hopefully I'll see it then!

AngryCorvair
AngryCorvair MegaDork
10/10/18 11:03 a.m.

In reply to maschinenbau :

Judging of primered Challenge cars is kinda like I before E.  sometimes, but not always, follows a pattern.

maschinenbau
maschinenbau Dork
10/10/18 7:02 p.m.

I just bought supplies for a Thursday night parking lot roll-on paint job. Let's do this!

Re: Awkward brake bias. Some ideas have been floated past me for reducing the rear brake bias to prevent the car from rotating too much during autocross. I'll warn you, not all of them are good...or are they?

  • Lubricate rear rotors with lithium grease between runs
  • Install the rear brake pads backwards (metal side on rotor)
  • Run with no rear rotors, shove block of wood between rear pads
  • Vise grips pinching rear brake line
  • Actually install the bias valve and just get on with it already
Stampie
Stampie UberDork
10/10/18 8:20 p.m.

Don't hit the brakes because they only slow you down?

RealMiniNoMore
RealMiniNoMore PowerDork
10/10/18 9:16 p.m.
Stampie said:

Don't hit the brakes because they only slow you down?

Yeah, man. Brakes are for Bob Costas.

I mean, c'mon. Look at my avatar. laugh

Pete Gossett
Pete Gossett MegaDork
10/10/18 10:24 p.m.

In reply to maschinenbau :

You forgot “drift the entire course”. 

sleepyhead
sleepyhead Dork
10/11/18 2:29 a.m.

just make sure to include the vice grips in your budget wink

edizzle89
edizzle89 SuperDork
10/11/18 8:03 a.m.

weld diff, remove one caliper and leave one on. easy peasy

AngryCorvair
AngryCorvair MegaDork
10/11/18 8:43 a.m.

put the ABS back on, just mount it lower than the MC.   this is the true win.

maschinenbau
maschinenbau Dork
10/11/18 4:16 p.m.

On our way!

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