BMW Compact Build

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john vanlandingham
While living there i chanced upon a bumper stick which encapulated, refined, personified perfectly the baseline , default attitude spanning every social and economic class, age, and race in the area inside 128. It read simply "Fuck you, you fucking fuck"

I think I've seen that one, and I can hear someone with a southie accent saying it now. The town I grew up in was split by 128...I was on the inside. LOL

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fiasco
I still can't understand how anybody not under heavy sedation could actually live in the metro Bahstun area.

I got out as soon as I could, moved to Colorado Springs for college and moved to Denver as soon as I graduated. Similar climates...but way better out here...and skiing is skiing, not ice skating with long skates.

Dave



Edited 1 time(s). Last edit at 01/31/2011 10:33PM by DaveK.

Yeah, I forget your rear is E30, not E36. All the failures are on E36's

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phlat65
Yeah, I forget your rear is E30, not E36. All the failures are on E36's

That's fawkin eaahhhh goOD!

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DaveK

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phlat65
Yeah, I forget your rear is E30, not E36. All the failures are on E36's

That's fawkin eaahhhh goOD!

Wicked pissah that you don't have to stiffen up that fawkin' thing!

I'm a Mainah... a few years ago after flying for 12 hours I start the drive from Boston north. Missed my turn on a long and congested roundabout and ended up having to force my way into a line of traffic exiting (something every Boston driver does at least ten times on the way to work.. totally not a big deal). This guy in a Saab was so mad that he just lost ten more seconds. A minute later we were stuck next to eachother in traffic for like five minutes and the whole time he was screaming and flipping fingers. I just smiled.

[

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I think I've seen that one, and I can hear someone with a southie accent saying it now. The town I grew up in was split by 128...I was on the inside. LOL

Yeah? Where?

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.but way better out here...and skiing is skiing, not ice skating with long skates.

Dave

PNW wet concrete slush is one thing, at least it firms up at night, but fawk me the 2 times i went "skiing" deep shiney transparent BLUE ICE! Acres of real gawddam ICE not some lame little crusty skaty "oh like wow i think its maybe icy" this was GOOD GAWD MAN THATS BLUE and 3 feet thick!

Take this advice from an engineer who works with this stuff all day everyday...

Ditch those residual valves asap. There's no issues with the fluid "draining" back to the masters, there's not really a drain back concept, all that you have to do is to keep the fluid res higher than the bleeders on the calipers, thats all.

As for fighting knockback, the correct way to get rid of it is to install anti-knockback springs behind the pistons.

Now the reason the residual valves are stupid to use and should've never been thrown on the market is because they hold about 10psi of line pressure. That on an M3 with stock calipers (60mm front and 40mm rear pistons) and average Mu pads is about 46 ft-lbs of brake drag. Also the fact that the fluid is not free return to the mc's the breather port hole on the mc's wont open and wont equalize the pressure behind the piston was well, and also when thing start to get hot (and with 46# of brake drag it will) the fluid will start to expand and wanting to push back but all it will do is drag the brakes even more. Also vapor lock. Uggggh just toss those things and install the springs. You'll always have a firm pedal and wont have to worry about any mickey mouse gizmo's like that.

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DaveK
Decided to install some residual pressure valves in the brake lines, and have been tracking down the right fittings to get them to work. These valves are used to keep a couple PSI in the brake system to keep fluid from draining back to the masters (when floor mounted), and may also help to fight pad knockback that seems to plague cars that race on rough surfaces. Got those installed yesterday.

I did pickup the 2psi ones, the 10psi ones are meant for cars with drum brakes or at least that's what the info on the website says.

The other things you've mentioned about fluid expansion make sense and don't sound good, but if I'm installing a 10 lb spring inside the caliper, how is that all that different from keeping 2psi in the lines in terms of brake drag?

I'll leave it as is for now, but will investigate anti-knockback springs for the wilwood calipers when I get around to getting those installed later this spring.

Thanks!

Dave

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DaveK
I did pickup the 2psi ones, the 10psi ones are meant for cars with drum brakes or at least that's what the info on the website says.

The other things you've mentioned about fluid expansion make sense and don't sound good, but if I'm installing a 10 lb spring inside the caliper, how is that all that different from keeping 2psi in the lines in terms of brake drag?

I'll leave it as is for now, but will investigate anti-knockback springs for the wilwood calipers when I get around to getting those installed later this spring.

Thanks!

Dave

Ok ok ok, 2psi is a little better but still hold the fluid and the seals will still be swolled up. Now as far as the knockback springs, they're normally around 4-6 pounds each. So on a billywood caliper with 1.75 pistons and 2psi line pressure still equates to 19lbs of clamp load per caliper.

Putting the 4 or 6lb springs will get you less than 10lbs of clamp on average once you figure in seal rollback and resistance.


Now as far as knockback, the 2psi valves will do nothing to it because once the bearing moves and shows a periperal force of more than 10lbs to each side it pushes the pistons back nothing will push them forward again, thats why the springs are so good piston can move back and forth will always be in contact with the pads.

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Cosworth
Now as far as knockback, the 2psi valves will do nothing to it because once the bearing moves and shows a periperal force of more than 10lbs to each side it pushes the pistons back nothing will push them forward again, thats why the springs are so good piston can move back and forth will always be in contact with the pads.

Thanks for the info! Another question just popped into my head:

If the valves keep some pressure in the lines, won't that help resist the knockback in the first place? Or is it not enough pressure to really win that battle and effectively drag the brakes more but still allow the piston to get pressed back in?

Would you see using one of these on a clutch pedal as having the same drawbacks, or likely to be ok for that application since the fluid won't be getting heated up? My brake reserviors are mounted on the top of the trans tunnel, so I think they're sufficiently higher than the nipples on the brake calipers, but the bleeder for the clutch is probably an inch or two higher since I didn't use a remote reservior.

Dave

The valves will only resist knockback if the force applied is less than the 19lbs of clamp load... know what I mean, and at that point the pistons wont move forward anymore and you'll have a long pedal. As for the clutch I dont really see a problem short always have constant pressure on the TO bearing, might reduce the life but dont really know.

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DaveK
Thanks for the info! Another question just popped into my head:

If the valves keep some pressure in the lines, won't that help resist the knockback in the first place? Or is it not enough pressure to really win that battle and effectively drag the brakes more but still allow the piston to get pressed back in?

Would you see using one of these on a clutch pedal as having the same drawbacks, or likely to be ok for that application since the fluid won't be getting heated up? My brake reserviors are mounted on the top of the trans tunnel, so I think they're sufficiently higher than the nipples on the brake calipers, but the bleeder for the clutch is probably an inch or two higher since I didn't use a remote reservior.

Dave

Where are you with the diff?

Lower mount is done. I think Steel Solutions is maybe sending a rear diff mount and we have some modifying to do to try to get it on.
Dave's been working 7 days a week and in Steamboat on weekends teaching at the winter driving school so there hasn't been much progress last week or so.

JVL sent out a non-powdercoated version of that rear mount that you have Grant. Hopefully we can adjust the diff forward/backwards slightly so that we can put the mount where that boxed beam goes across the underside of the floor so we can weld it in on two edges. May also try to get a measurement so the driveshaft guy can finally make one.

I picked up two more helper springs, so maybe we can "de-Safari ride height" the car a little bit more.

Also been looking at a couple kits out there that will let me retrofit E46 front control arms to the car. At ~15-16" fender-to-hub height, I'm at ~3 degrees of positive camber up front. The E46 arms are 65mm wider than the E36 ones, so it should help fix that positive camber issue, I'm just not sure if it'll move it too far in the other direction. General consensus is 1-2 degrees negative up front is plenty, right?

I'm headed to the shop after work, so I'm going to try and see how much of a camber change that extra width should cause. Hopefully someone on here is good with teh maths.

Dave

Ford Sierra specs were between 1 and 1.5 neg on gravel.. I have mine at 1.25 neg