I'm running 46 ford coupe frontend and rearend (Stock drum brakes), and have nearly all my lines run and they are 3/16", from the rear to the brake pedal (Wilwood 7/8 bore ms). I had to move my front lines when I installed my radiator/grille. I'm wondering if I can mix 1/4" lines in the front because of my rubber lines will fit on the 1/4" lines not problem, if I use the 3/16" lines I have to use an adapter for them to fit on the rubber lines. Would there be any problems mixes those size lines?
Anyone, I'm about to go buy some hard lines and finish up the job tonight. But only with your help! thanks
I mixed line sizes on the front of the Raunchero when i straight axled it and i am still alive.People warned me not to ,but i tried it any way and the brakes stop as well as my wifes late model ...
I didn't figure there would be a problem, but I wasn't sure. I may just go ahead and run the little lines with the adapters that way they are consistant.
I believe line pressure is determined at the master cylinder. Whatever, the pressure in a hydraulic system is equal everywhere in the system.
I stepped up the line size on mine to the new rubber lines on the spindals.I dont know for sure if stepping down would cause a problem cuz i havent done it personally.I was told the smaller lines from the master cylinder couldnt supply the pressure to the bigger lines but i can lock up all four wheels if i try and mine has 49 Chevy brakes (rebuilt by me of course) and original 49 drums on the front.With a mustang 2 rearend and little drums on the back.It stops as well now as it did 2000 miles ago when i did it.If it didnt i wouldnt drive it.Good brakes is one thing i dont compromise on...
this is a good thread. i'm getting ready to redo all my lines and new ms also. the downside is i don't really know what i'm doing. can't seem to find any books that go into depth more that rebuilding a drum brake.can anyone point me in the right direction for reading material? sorry chaddilac, not trying to hijack.
Petersen Publishing printed a soft cover book some ears back about brake systems etc. You may be able to get a copy through Amazon. Petersen also printed a soft cover type motors manual that I believe was called "The Big Book of Automotove Repair" or something like that. There are also sites on the web that go into detail.
My 69 El camino has both 3/16 and 1/4 inch lines factory.[4 wheel drum] The fronts are 3/16 from the master to the rubber hoses the rear is 1/4 from the master to the rubber line then 3/16 from the rubber to the wheel cyls.
Use the adapter. I was always of the idea the factory ran 1/4 to the rear of some older cars to soften the "hit" and reduce the possibility of rear wheels skidding prematurely. Anyway, if you can get an adapter, then i'd say do that
Hmnnn, never heard that one before. How do you suppose it does that? I never took hydraulics - but it seems to me that the volume displaced at the m/c and the resulting volume displaced at the wheel cylinder is pretty much unaffected by the line size. After thinking on it for a few minutes the only thing my pea brain can come up with is that Disc Brakes operate at roughly twice the pressure as drums brakes do. With that in mind I wonder if the factory switched from 1/4" (old standard) to 3/16" (newer standard - sorta) in an effort to lower the force that the line "see's" - yes it's all PSI But there's LESS "SI" (square inches) in a smaller diameter line - allowing it to withstand a higher pressure - all other things beign the same. Just thinking out loud
It's just an educated(?) suspicion of mine. I can't think why else the factory used 3/16 up front and 1/4 in the rear up to the tee on the rearend housing. What's your guess?
My guess is that Detroit realized it didn't matter and since 3/16" was cheaper - someone got a HUGE bonus when they switched!!! That or someone was worried that the rear being farther away would suffer some parasitic loss and alleviated this with the larger size line - yes I am digging way deep into my "BS bag" for this one.
Thanks guys... I figured if there would be any problems, it'd be with adding in 1/4" line in the mix. So I went to the parts house and got some more 3/16" lines just to be safe. Very different brake line setup from what I've seen. I ran a short soft line to the wishbone then a hard line down the wishbone and another short soft line to the inside of the frame rail. My frontend is suicide so the regular soft lines were to short. Looks pretty cool anyway.
Like Pasadena said, hydraulic pressure in a closed system has to be the same at all points. If you ran 1" lines and adapted down to what the wheel cylinder required things would still operate the same. That said, I think a couple of the reasons factories went to 3/16" line - or vice versa - is that they were worried about mechanical strength of the tubing and figured 1/4" would resist better than 3/16". And the 3/16" was used up front so they could coil it in a spring-like shape to help damp vibration and the attendant problems from same. As well as be able to make sharper turns with the 3/16" tubing. Far as the economy thing goes, line size mix may be simply due to trying to use up 1/4 line after they figured 3/16" would do the trick at all four corners. Factories more than lkely bought the tubing many months in advance and bought millions of feet at the time.
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