I purchased a new Speedway HD axle for my recently acquired Drag Week Gas/B project. Just general question with a swapped in straight axle when using a firewall mounting dual master. Should I treat the front axle just like the factory does the rear axle on most cars? Though obviously with flex lines going to the disc calipers Meaning I run a hard line to the frame, jump a flex line to a Tee on the axle, with hard line running to the flex lines for each caliper. Is there better way to do it or is this obvious way the best way?
If you want to use 3 flex hoses, you can do that. A simpler way is to plumb it like anything else, run the metal lines to a bracket on each side mounted to the frame near the brake, and one flex line to the caliper on each side.
I dont necessarily want to do it in any given way other than an easy and effective one. This seemed more straightforward to me than trying to get a hardline all the way to the other side of the engine bay. Which I have done before, but I feel like that takes significantly more effort. Not so much to do it, but to make it look semi-decent. When I did it before it was effective. but pretty it was not. The biggest issue is I didn't have a line straightener. If that extra 16" or so of soft line isn't going to cause issues the way I outlined seemed easier to make it look clean. I guess that's more what Im asking, is will an extra piece of short flexible line noticeably compromise braking? FWIW, this is the way the Right Stuff rear disc kit on my later model (67) Firebird is set up (per their directions) You weld a couple tabs on the rear axle to anchor flex line that goes to the calipers. And then you have the factory flexible line that runs from the rear hardline to the axle.
You can purchase lengths of straight line from your local auto parts stores. Running it on the axle will probably be less visually appealing than running it along the backside of the front crossmember - especially on a g***er where the axle is hanging out more in the open. I'd personally just follow the tried and true flex line from frame to wheel cylinder method. If you do decide to route it as you've drawn, the third flex line won't add any noticeable effect. As you note, retrofit kits and modern vehicles with disc brakes and a solid rear axle will use three flex lines.
Always saw it as line to each front corner (2 hoses), so that's my knee jerk reaction. Your 'rear axle' way is proven on the back as you say. So I'll offer a couple thoughts on why, not necessarily trying to talk you out of it, just additional points. Unsprung weight (tiny, I know). More fluid is subject to more vibration. 3 brackets on axle for hoses needs quality weld, is subject to more vibration. One more fitting and hose to leak. Line on axle should be behind, not on top (subject to damage). Servicing is 50/50, removing full axle is one hose, doing brakes is the same. One more hose to inspect. I'd look at stuff that uses a solid axle in front still (equipment, 18 wheelers) and see if this is used in those. It's going to cost a bit more in production, but there may be a safety reason too. Seems like it's a KISS situation. The hose is going to have more twist/movement to follow the arc of the wheel turning unless you locate it just right. I say all of this with a dormant project in the garage that has 3 hoses in the rear, because calipers.
Excellent point about running it behind the cross member. In this case I dont know that there is going to be a cross-member in the traditional area. The original k member was removed so its currently open in the center. This is going to be a front/mid engine plate setup. But otherwise yes that is how I would do it with the line on the cross member. Should have mentioned that. My last g***er project was the same, the center of the engine bay was open and it had a bar ran from rail to rail at the front of the frame to add rigidity back in. That was wasn't an engine plate setup though. I am undecided if Im going to add back in a cross member for rigidity, where that will be, or if a roll cage will be significant enough. An entirely different set of questions and conversation. My biggest hesitation with doing it like my drawing is you lose the axle as a point where you can throw a strap around the axle as a tow point if (when) I break the car. Because you would kink the brake lines.
I actually think that's the method I tried, but to be fair I didn't try very hard. I think I was just annoyed at myself for not having the foresight to buy the tool ahead of time and half ***ed it. It was also the first time I had done a custom brake line job from front to back. You are always better after you did it once and screwed some stuff up. I work in process improvement, so I tend to be a tools person when its financially reasonable to do so. I do think that I later saw a thing where a dude drilled a small hole in a piece of 2x4 and pulled the line through the wood which straightened it pretty good.
You can ģet brake line straight by putting it between 2 pieces of say 3/8" ply and sliding the upper piece over the lower with a sawing action, rolling the line straight. Line needs to be roughly straight first, not colied! Chris
3 flex lines in brake systems are quite common. Look under the front of most disc braked solid axle 4x4's and most have 3 flex lines, rear axles are also the same so clearly it works.
If you are doing a proper race duty G***er then you'll probably have to relocate the Master Cylinder down to the floor/frame mount, esp when you incorporate the midplate/motorplate into a 12pt rollcage structure.
If you are planning to run drag week or a track where they check stuff you need to get a NHRA rule book . It used to be no brake line on the firewall or bell housing area and no brake lines on the cross member near the dampner. We would run the front lines on the bottom of the radiator support. Just a thought , but I am out of the loop.
It boils down to not wanting to spend the money to get a tubing straightener. They do a great job really easily. You will have other lines on the G***er that need to be straightened as well to look right. Other future projects ??? or sell it if you will never ever need to straighten a tube again. Since you like tools, bite the bullet and do the job right. Amazon has them for about $85
I always hard line from master to the driver's side frame rail nearest the wheel. Then install a Tee there that the flex line comes out of, and hard line to the p***enger side ending at the same spot as the driver's side, and a flex to that caliper. Simple, clean, and like most factories did.
Since I can't think of any OEM front axle that had a line going across the axle, why would you go there?
Given that I don't have a traditional cross member as I mentioned, that is likely what I would have to do. I also mispoke earlier, I completely forgot that I purchased one of the under dash clutch/brake setups from Wilwood, so I lied about a normal dual master on the firewall. Its the reverse mount deal with three separate master cylinders that reverse mount. I just bought that like 4 days ago and I already forgot about it. That might open up a different possibilities.
if you are wanting to straighten out rolled brake line tubing, try taking a couple short pieces of 2x4's, then screw 2 or 3 together, once connected together, drill a hole all the way through the stack just a little larger than the brake line. Straighten out a section of brake line to get it started through the hole in the 2x4's. Now unroll what you want to use from the roll and cut it. Put the 2x4 stack in your vise. and pull the tubing through the hole. 2 or 3 time through and it will be nice and straight. that how I do it.
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