ALFAGTV6.COM

[ar4me]

I'm about to move the rear brake hard-line from running next to the drive shaft under the car into the cabin on my race car, and I will add a Tilton adjustable brake bias valve (7 position lever type) at the same time. So, in the process of selecting the hard-line I have been searching a bit. I plan to use 3/16" line. Regarding material there are some options:
1. steel
2. stainless steel
3. bundy tube (aluminum coated carbon steel) - perhaps just a variation of 1.
4. Cunifer (90-10 copper nickel)
The latter is apparently a fairly recent development (which is used by many major car manufacturers today: Volvo, Audi, Porsche, ...) and is DOT approved. However, an article on brake lines for race cars revealed that although decent, Cunifer tube has lower yield strength than Bundy tube, and it has higher expansion rate under pressure. That same article recommended using good-old bundy tubing for brake lines on a race car (due to yield strength and expansion rate), while Cunifer has no place on a race car (although fine for the street). The advantage of Cunifer is corrsion resistance and easy to work with (in terms of bending and flaring).

In terms of connectors there is a choice of AN (37*) or SAE/ISO 45*, single or double flare, ISO bubble flare, SAE double flare. The use of AN fittings with single 37* flare appears advantageous since it does not fatigue the brake line material from multiple diss-assembly/assembly operations, and it provides a better (re-usable) seal.

So, in summary it appears 3/16 bundy tubing with AN3 steel fittings on 37* single flares is a good choice for a race car.

What have you guys used on your race cars? Any thoughts or suggestions?

Jes

[Mats]

Good 'ol Stock lines.
Braided teflon on the flexi bits though.

[ar4me]

Good 'ol Stock lines.
Braided teflon on the flexi bits though.

So, what material are stock lines?

They appear to be 3/16. The flares appear to be ISO/DIN bubble flares, and nuts are probably 10mm x 1.0.

Jes

[MR2 Zig]

I think that most US standards require double flare. Go with the coated steel for corrosion resistance tho I think plain steel will be fine. Stainless would be ok but for cost. Copper would be last....it would be ok for an oil line or something else low pressure, just not 4-500 lb brake lines.

Older US cars use steel lines...uncoated.

hth

Scott

[ar4me]

I think that most US standards require double flare. Go with the coated steel for corrosion resistance tho I think plain steel will be fine. Stainless would be ok but for cost. Copper would be last....it would be ok for an oil line or something else low pressure, just not 4-500 lb brake lines.

Older US cars use steel lines...uncoated.

hth

Scott

Single or double depends on flaring type. Standard brake lines are typically 45*, and SAE requires double flare, but if AN, i.e. 37*, then the flares should be single, and double flare is inferior (according to what I have read). Note that _serious_ race cars use AN (37*) while mass production cars use 45* (SAE or ISO). The AN gives a better seal (which is also why it is used on aircrafts, I suppose).

The 90-10 copper-nickel _is_ for brake lines, and _is_ used on many mass production cars for brake lines.

Jes

[MR2 Zig]

Ok, but which flare will hold in the compression nut better? I understand that the tube pulling out of the nut was why the double sae flare was used (granted 20+ years ago)

AN is an aircraft standard like SAE for cars. The significant difference is weight of fasteners. If the 37deg. AN flare will take, as a service pressure not peak, 3000psi then I think your safety factor is adequate. If not I'd use the steel.

BTW the stainless is is bleepin hard to bend compared to the steel, but in the small sizes your talking about for brake lines shouldn't be that big an issue. 3/8 in. stanless is where it gets rough.

Scott

[ar4me]

The advantage of the AN fittings is that the compression area is at least twice as large, and there is a sleeve between the flare and the nut (unlike SAE and ISO). Hence, the flare is isolated from the torque of the nut as you tighten it. I read a quote that the only thing Carroll Smith would put on his race cars were AN single flare. Double flare should be used with SAE (perhaps with some dependency on tube material), but single flare is recommended with AN.

Some of this may be a bit academic, but since I'm replacing stuff I want to do it to the best practical standards. So far I'm leaning towards Bundy tube with AN where possible. At MC I'm obviously forced to use what the MC takes.

Jes

[MR2 Zig]

Jes,
A separate issue you may consider is what hardware is easy to get vs. having to order....may not be an issue for you.

hey, isn't most aircraft tubing aluminum anyway? maybe, if it will work, that would be a way to go....aluminum would be both lite and easy to bend.

scott

[Mats]

NO WAY Aluminum!

It will fracture sooner or later and up until that point it will flex like crazy. Shun it like the plague.

Std on the GTV is steel, painted.

[MR2 Zig]

brain fart on my part

[Moynesey]

Hi

I always run Euroquip braid lines when running through the cabin, it can be a nightmare to get the joints to seal at first (make sure you cut it straight then strip) but once done gives a faultless service in my experience. Things like bulkhead fitting are nice touches instead of grometts on the inner wings/bulkheads/floors.

Just make sure you can get all the fitting you need for the original equipment you will be connecting to.

Also looks great next to the fuel line if you spend the time getting them in a straight line and nice order!!

Copper is easier though!!

[tomp]

Hi Jes,

Just saw your post. Did you get your balance bar setup installed? I was wondering what master cylinder sizes you ended up with. I did some calculations but really dont know the real CG height or braking G-force. Ive machine up a system that fits (barely) within the ABS housing and hope to do testing around the end of next month.

-Tom P.