Installed Front Parabolics and Brakes Went Soft

[artpeck]

I just completed the front end installation of parabolics and new shocks yesterday.

All went totally fine, no issues or surprises and was done in 3 hours. Dramatic improvement over OE springs that were rusted into a solid mass.

When I went to drive the truck the brake pedal was very soft but with one pump it braked normally. And in driving about town it any time elasped between braking I would have to pump the pedal again. I checked the hoses, fluid etc and all was good. I literally changed nothing wrt the brakes other than the truck sits somewhat higher so the flexible brake line is extended at a different angle. Not over extended however. On my list to replace but trying to figure out what the heck is going on. Any thoughts as always appreciated.

[SafeAirOne]

Did bleeding the front brakes change anything?

[artpeck]

I didn't have the time to do so yesterday so I will when i get around to it. However how would air have been introduced since I didn't touch them? If bleeding fixes it doesn't that mean that there is a flaw in the line? The master and all four wheel cylinders are new as of a few months ago when I got the truck and started work. Having sat for 16 years unrun all the hydraulics, brake and clutch, were shot.

[SafeAirOne]

However how would air have been introduced since I didn't touch them? If bleeding fixes it doesn't that mean that there is a flaw in the line?


Flaw in the line. Damaged flex line. Call it what you will.

Or it could just be a coincidence. If bleeding fixes it and it doesn't leak, you're all set. It might not even be in the front brake system, but that's where I'd start for obvious reasons.

[I Leak Oil]

Yup, you probably stretched\damaged a line while swapping springs or it's just pure coincidence that something wen't at the same time. Bleed em' and try it again...

[artpeck]

This aspect of working on the truck perfectly defines my mostly love/sometimes hate relationship with it. Every project successfully completed triggers something else to deal with. Mostly love as in in I really enjoy working on it and it would be a let down to be "done" which of course will never happen. Thanks for the advice as always.

[Eric W S]

You should have replaced you flex lines with longer ones when you swapped your springs. The truck rides higher and your old ones are now just dangerous.

Just get the longer braided BF Goodridge ones our hosts sell and re-bleed the system.

[I Leak Oil]

X2 on the longer lines and using Goodridge. RM used to pimp their longer, rubber lines when they sold a set of springs for good reason. Not sure if vendors recommend this much any more or not as I haven't needed to buy springs in a few years.
With any luck, you'll find a bum flex hose and need to change them anyway.....if you can call that luck!

[jac04]

You should have replaced you flex lines with longer ones when you swapped your springs. The truck rides higher and your old ones are now just dangerous.

Just get the longer braided BF Goodridge ones our hosts sell and re-bleed the system.
The use of longer brake flex lines is not always necessary. The front shocks can limit travel and keep the rubber flex lines operating well within their design range. I used standard rubber flex lines with parabolics and OME shocks on my SIII lightweight. No issues at all. On a IIA, the flex line arrangement is a little different, but you can adjust (by bending) the mounting brackets on the chassis to keep the flex lines happy. Just make sure to check the lines under full articulation with the steering maxed out in both directions.

BTW, BF Goodrich = tires, Goodridge = brake lines.

Now, you may think that the fancy stainless braided lines are the way to go, but this isn't really the case. The Teflon inner hose can be quite fragile (hence the outer stainless protection), and hose failure is much more common than with standard rubber hoses. If dirt works its way in between the teflon hose and the braid the hose will fail. They are easily damaged/kinked by debris hitting them or bending. They are also difficult to inspect for damage to the inner teflon hose.

IMO, the standard rubber flex lines are the best ones to use.

[SafeAirOne]

The use of longer brake flex lines is not always necessary. The front shocks can limit travel and keep the rubber flex lines operating well within their design range.

Possibly so, but that's not good for shock absorbers and can cause damage/failure to them if I'm not mistaken. They generally aren't designed to take impact loads caused by the piston bottoming out on either cylinder end.

I believe (and again, I could be wrong) that's why they recommend changing the shocks to ones with (presumably) longer travel when you change to parabolics.

The axle check straps should be limiting your axle travel, as opposed to the shocks.

[I Leak Oil]

Using normal shocks to limit suspension travel is not a good practice, especially if that's what you're using to keep your brake lines from over extending! Shocks and brake lines need to be sized accordingly unless your truck never hits the dirt.

[jac04]

I believe (and again, I could be wrong) that's why they recommend changing the shocks to ones with (presumably) longer travel when you change to parabolics.

The axle check straps should be limiting your axle travel, as opposed to the shocks.
True, but there are no check straps on the front. The only thing limiting travel is the shock absorber (and/or the ability of the spring to flex to full droop). I installed the (presumably) longer travel OME shocks on the front along with parabolics and still found that the shocks would keep the brake flex lines from over-extending. However, I checked by removing the shackles and allowing the shock to fully extend. No idea whether or not the shock could easily bottom-out fully extended in real life.

[Eric W S]

The use of longer brake flex lines is not always necessary. The front shocks can limit travel and keep the rubber flex lines operating well within their design range. I used standard rubber flex lines with parabolics and OME shocks on my SIII lightweight. No issues at all. On a IIA, the flex line arrangement is a little different, but you can adjust (by bending) the mounting brackets on the chassis to keep the flex lines happy. Just make sure to check the lines under full articulation with the steering maxed out in both directions.

BTW, BF Goodrich = tires, Goodridge = brake lines.

Now, you may think that the fancy stainless braided lines are the way to go, but this isn't really the case. The Teflon inner hose can be quite fragile (hence the outer stainless protection), and hose failure is much more common than with standard rubber hoses. If dirt works its way in between the teflon hose and the braid the hose will fail. They are easily damaged/kinked by debris hitting them or bending. They are also difficult to inspect for damage to the inner teflon hose.

IMO, the standard rubber flex lines are the best ones to use.

First I have ever heard about someone advocating the use of the OEM brake lines! Problem is most people change shocks so most change lines. Paras can damage stock shocks easily off road and I for one wouldn't want a brake failure offroad. Second, why bother with Paras if you can't utilize them with stock shocks? It's just stupid not to change. Period.

rich v ridge = whatever.

Been running braided lines and never seen one fail. Ever. Maybe your buying crap. Who knows. Most have moved onto durable sleeves over the braides to prevent the exact thing your speaking of. Had a set of EE's on my D-90 for years. No worries. In fact, everyone in CLRC who upgraded suspension upgraded to EE lines or like and never a problem.

Stock lines suck compared to any decent covered braided lines. I would always rather have too much line than too little. Especially if you actually use your truck off road.

[artpeck]

For what it is worth I installed RM paras and their pro comp shocks. Appreciate the passion on the issues. I took a look at the brake lines again and with the truck sitting on level ground they are in no way stressed or hyper extended. I am assuming however that when detached the axle to remove the old spring and refit the new I probably stretched and compromised one or both. Although I also don't have any fluid leakage. Good hygiene says replace them anyway as they are almost 40 years old and were already on the list to do before I begin using the truck in ernest.

[Eric W S]

I took a look at the brake lines again and with the truck sitting on level ground they are in no way stressed or hyper extended. Good hygiene says replace them anyway as they are almost 40 years old and were already on the list to do before I begin using the truck in ernest.

The safety issue arises when you articulate the axle. The longer stroke of the ProComps and the increased range of motion from the paras will not produce happy results for your stock lines.

On level ground the stock lines will not appear to be a problem.

Sounds like replacing the lines is the happy ending. Good time to see if any other brake parts might need some love while you have the wrenches out.

[artpeck]

I have replaced with new the master and all the wheel cylinders. Inspected the hard line. All brakes have been apart obviously so shoes inspected as well. Everything cleaned,degreaser, appropropriatly lubed and reinstalled. Springs all good. So, this is the last link (until something else surprises me). Thankfully the truck is 100% rust free as it has 31,000 miles in northern california and then was simply stored. So far there haven't been any truly ugly surprises. Cross my fingers.