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Volvo R brakes on 240 pedal feel issues

Texas240

Prius Owner
300+ Club
Joined
Jul 27, 2008
Location
Dallas, TX
Ive been battling pedal feel issues for a few years now since I've put the brakes on. The first motion of the pedal I have nothing, maybe a little braking then I start to get braking. I get full brakes at the very end of the pedal movement. Ive tried a few different known good boosters, tested with a mittyvac pump to check of leaky seals and Ive switch over to the mustang master cylinder.

Generally I dont complain in dry condition, I have great breaking other then the pedal feel. When its braking in the wet, tires just lock up, same ****ty pedal feel or lack of pedal like in the dry condition then brakes just lock up unless you gingerly apply brakes. What are other peoples pedals feel like with the R brakes on the front and the mustang master?
 
Leading Piston Size: 42mm (2 of each)
Trailing Piston Size: 38mm (2 of each)
REAR BRAKE CALIPER PISTON DETAILS:
Leading Piston Size: 28mm (2 of each)
Trailing Piston Size: 30mm (2 of each)

I found this on VIVA's site.
 
i would start with what the volvo r used for a master cylinder, what bore for what your using power/no power assist, then check pushrod, then pedal ratio, when i put the big brakes on my Chevy all of these things bit me in the ass, and a used hydro- boost that was slowly applying the brakes when it was running
 
So you had the same issues with the stock old Volvo MC and then a new Mustang MC?

I had this same problem with my mazda rx7 brakes with stock Volvo MC when I went from manual to auto then same issues with the Volvo R front calipers. This was also with a new volvo stock master.

Have you already played with the pushrod adjustment?

Yes, but this has been in the back of my head.

i would start with what the volvo r used for a master cylinder, what bore for what your using power/no power assist, then check pushrod, then pedal ratio, when i put the big brakes on my Chevy all of these things bit me in the ass, and a used hydro- boost that was slowly applying the brakes when it was running

I'm using the exact master Volvo R is using
 
If you're adjusted fully outwards and it's still not enough, here's what Marv did (Similar to Homer when he ran the Porsche Calipers IIRC). Do note that Marv is running the Cadillac ATS style Brembo calipers on the front of this car(wagon), though. I figured it's worth mentioning before getting further into the system and having to deal with bleeding the brakes a few times.
Turns out all I needed was a small rod coupling on the brake booster rod. The stock rod is too short to actuate the mustang master cylinder. Id probably bled a gallons worth of brake fluid through the brake system thinking i had the process wrong or that there was somehow still air in the brake system.

The stock rod on the booster is sae thread so I was able to find a sae to npt stud at my local ace hardware. So purchased a new stud and then a 3/4" length rod coupling gave me the needed length to actuate the master cylinder when I pressed on the pedal. Finally, a stiff brake pedal.

<a data-flickr-embed="true" href="https://www.flickr.com/photos/36011564@N02/27251701895/in/dateposted-public/" title="WP_20160523_001"><img src="https://c8.staticflickr.com/8/7795/27251701895_63cd20f9fa_c.jpg" width="800" height="451" alt="WP_20160523_001"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

I spent yesterday evening playing with the rod length. It was too long at first so the brakes were dragging. That's one way to bed in the new pads i guess. But I was able to get it really dialed in.
 
If you're adjusted fully outwards and it's still not enough, here's what Marv did (Similar to Homer when he ran the Porsche Calipers IIRC). Do note that Marv is running the Cadillac ATS style Brembo calipers on the front of this car(wagon), though. I figured it's worth mentioning before getting further into the system and having to deal with bleeding the brakes a few times.

Did exactly as Homer did with his extension
 
Ah, word. I'm pretty much just echoing what freevolvos is saying though so, cheers. Unfortunate that the problem may lie deeper.
 
I realize many of us are asking 'problem obvious' questions....but, here we are. Did you bench bleed MC's when you replaced them?
 
The rod length is important to get right. If you haven't you need to replace the adjustment screw on the end of your brake booster rod. The stock rod isn't long enough to work with the mustang master.
 
The rod length is important to get right. If you haven't you need to replace the adjustment screw on the end of your brake booster rod. The stock rod isn't long enough to work with the mustang master.

read bellow.

I realize many of us are asking 'problem obvious' questions....but, here we are. Did you bench bleed MC's when you replaced them?

Yes
 
Leading:omg:!!!! Piston Size: 42mm (2 of each)
Trailing !!!! Piston Size: 38mm (2 of each):omg:
REAR BRAKE CALIPER PISTON DETAILS:
Leading Piston Size: 28mm (2 of each)
Trailing Piston Size: 30mm (2 of each)

I found this on VIVA's site.

Veeeeeeeeeeeeery interesting , Schmart...:oogle:

But EVERY progressive piston caliper---and those sizes are common as hell, and perfect--but I've already been banned like 3 times by that guy Mr Super Nice Guy up there in your neck of the woods just on piston sizes so I won't say more about that----
EVERY progressive has smaller piston FIRST...because as a n AP Racing injur-near once siad "First piston gets a nicer "bite" on the disc with longer pads so 1.5" first, then the trailing at 1.625"

Always:nod:
 
let us know if you get this figured out I'm interested in what causing the issue

We did the math and we think I that I bought the wrong bore size mustang master cylinder comparing the stock 240 one vs. the s60r/v70r the one I have is too small so I've ordered a 1-1/16th inch bore.
 
the smaller the bore the higher the pressure in the line, i hope this solves your problem, a lack of fluid Volume sure would cause a lazy pedal to and i would think a high pressure situation would cause grabby brakes, low pedal
 
I've had no pedal issues with my r brakes all around and mustang master :e-shrug:

I will say my pedal is a little touchy. Not lock the brakes up touchy, but someone that hasn't driven the car will find the pedal sensitive.
 
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