Brake Problems

[Nickel Dime]

A friend of mine has an 82 Lancia Zagato he uses for the street (when it's running). He has never had good brakes on the car, it takes a very high pedal pressure to just slow the thing down. He has had the booster rebuilt and it tests OK, replaced the master cylinder and converted to Fiat front calipers (one line vs two lines per cylinder). He gets good fluid flow at the bleeder and 17 inchs of vacuum at the booster.

We're running out of ideas. Any suggestions would be greatly appreciated.

[JohnRW]

Proportioning valve is plumbed in backwards ? Too big (yes...too big) a master cylinder, inside diameter-wise ?

You guys do know it's the MIDDLE pedal, right ?

If you changed from 2-line front calipers (a 'diagonal etc. system, like old Volvo's), how did you re-route the plumbing ?

[Nickel Dime]

From what he tells me, the original Lancia calipers had a main line going to the piston and a back up line going to a smaller area on the end of the piston - as a back up? I'm ASSUMEing he pluged the back up line at the master cylinder. That brings up a point - He swears he has the "main" line running to the calipers but should he plumb the lines so that both of them go to the single port on the calipers? Neither one of us has ever seen a car with two lines running to the calipers. If Volvo's had them I'll tell him to look into how those systems worked. Trying to find infomation on a Lancia is killing him. He's about ready to pull the whole system out from the firewall down and go with an aftermarket system.

[JohnRW]

Not real familiar with Lancias (...there's a statement for ya...), but I'd guess that they used 'Ate' calipers, just like my Alfa did...and my Volvo 142 did. If it truly was a dual-line system, then probably they are two-piston calipers in the front...and each piston is fed independantly by one of the lines, which also fed diagonally to the rear calipers. That way, if you had a caliper failure, you'd still have both front calipers braking 'a bit'. If he just 'plugged the backup line at the master', he's only getting half the braking action of the caliper, as he effectively just disconnected half his caliper.

Just an opinion here...but I wouldn't ride in the Lancia with him...at least until he gets the brake system plumbed right.

[Nickel Dime]

The original calipers (like the fiat replacements) were single piston. The rear breaks are fed through a seperate line off the master cylinder to a variable propotioning valve in the back. That thing is weird. The proportion valve is mounted to the underbody with an arm that connects to the sway bar. As the weight comes off the rear end it reduces the braking to the rear wheels. It seems to me that some engineer had way too much time on his hands when they developed this whole system.

And as far as riding with him --- luckily his inspection sticker has run out so he's affraid to drive it any farther than the end of the street. I just sit in the yard with a beer and watch. :birra:

[Conover]

The proportion valve is mounted to the underbody with an arm that connects to the sway bar. As the weight comes off the rear end it reduces the braking to the rear wheels.
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Just like a VW. Get him a chute, or an anchor, anything but an Italian car.

[ITC Racer]

I also have no clue on Lancias but I would check to see how/if the extra line is plugged. Depending on how the system is plumbed and if a plug is actually installed somewhere, you may be locking the master cylinder from
moving much (or any) fluid.

He may also have to check the master cylinder and caliper fluid volumes to see if the mc is not sized properly for the calipers.

Also, the adj proportioning valve system described above is fairly common in pickup trucks not too long ago and perhaps still.

[Nickel Dime]

We played with it the other night. I made him get the book out (with a system diagram) and explain what he had changed. The master has two main ports for the front brakes - one for each side - and one port for the rear. There was a fitting at the rear port that three lines tied into for a "mixed" system. Two lines went to the front calipers and one line went to the rear. He blocked off the two "mixed" lines going to the front and kept the single line going to the rear. The way he explained it, the original calipers have one piston contacting the brake pad with a second smaller piston behind it. The theory is, if the front system lost pressure the rear system would push the small piston into the big piston and apply some power to the front brakes.

We pulled the right wheel off and replaced the pads (from a different vendor) with ones for a fiat, which are actually thinner. He drove it (to the corner) and got the right wheel to lock up but still with heavy pedal pressure. So he's getting the hydrolic pressure to the calipers. We could not find anything with the Master Cylinder size so we'll do a little research to see if there is a difference between the Lancia and Fiat MCs. He's also looking into having someone like carbotech make him a set of street/autocross pads for a better bite. As soon as he gets the whoa pedal to work right he wants to start autocrossing and do a few HPDE events.

[Mark LaBarre]

..... He blocked off the two "mixed" lines going to the front ...
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I think you hit on at least part of it. If any fluid from the rear is putting force on the front pads, and you block that off, you're having the same effect as reducing the master cylinder diameter to the front.

[Eric Parham]

About 20 years ago I did the opposite. That is, I put Lancia Beta front brakes on a Fiat 124 Spyder. It's possible that I'm mistaken, but I'd swear that the Beta brakes we used had bigger non-vented rotors and dual-piston calipers. Now that I think about it, we had to use the 14" wheels from the Beta too since our 13" would not clear the calipers. I was told that Pininfarina did the same (or similar) upgrade on the final year (1985?) Pininfarina 2000 (rebadged Fiat 124 Spyder). I never did get the Fiat to brake evenly either before or after the upgrade, but always suspected that it was more of a suspension problem. Haven't owned a Fiat in quite a few years now, but thanks for bringing back that memory :)

[mowog]

There's a guy named David Strittmatter who races a Lancia Scorpion in FP. He's from Akron, Ohio, and I suspect he can provide some guidance on Lancia brakes. I don't have any other contact info, but maybe someone here can provide some help locating him, or you can try posting on the Production forum. Good luck!