I was considering swapping out my rubber brake lines for stainless steel. Should i buy Spiegler or Galfer and also is Motul DOT 5.1 Brake Fluid good enough for street riding. Thank you in advance

 

When it comes to stainless steel lines, they are all generally about the same so I'd pick one. Here is what I found on the 5.1 stuff.. I hope this helps you make a decision

"DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based).
Polyethylene glycol fluids are hygroscopic and will absorb water from the atmosphere. This degrades the fluid's performance, and if allowed to accumulate over a period of time, can drastically reduce its dry boiling point. In a passenger car this is not much of an issue, but can be of serious concerns in race cars or motorcycles.
DOT 5 is one of several designations of automotive brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point. DOT 5 is a silicone-based brake fluid. It is NOT compatible with any polyethylene glycol based fluids. Mixing DOT 5 with other types of brake fluids will start a chemical reaction that will cause solids to precipitate out of the mixture and inhibit proper brake system function.

Unlike polyethylene glycol based fluids, it is not hygroscopic, however this means that instead of being dissolved, any water in the system will eventually find its way to the lowest point in the brake line, corroding it, and potentially boiling and causing brake failure. Since it does not attract moisture, there is no way this will occur unless you are careless in cleaning out of the old fluid. Its major advantage over other forms of brake fluid is silicone will exhibit a more stable viscosity index in extreme temperatures, which is why the US Army likes silicone fluids. It is widely used in the antique automobile arena as well as it will not damage paint. From a lubrication standpoint, there is no appreciable difference.

Check with the manufacturer of your vehicle to see if this voids your warranty

If you do decide to make this switch, be careful. You will have to completely flush you entire brake system of the DOT 3/4 before filling with DOT 5. Flushing with mineral spirits is enough to cause a complete system failure in a short time. In fact the introduction of any petroleum based products such as motor oil, power steering fluid, mineral oil (baby oil) even in small quantities will cause failure. The only way to properly flush this is with a brake cleaner that does not leave a residue.

In order to flush the system properly, every component must be removed and cleaned individually, then lubricated with the new DOT 5 and reassembled. This is the perfect time to see if any parts are worn and replace them accordingly. If done properly and no moisture is introduced into the system, you will not have to replace the internal components of your system again."

 

you should be fine with 5.1, the brake lines and everything should say which types of fluid are safe to use as well so just check before running any fluid through them (usually 3,4,5.1) . The higher the number usually just means the more resistant the fluid is to breaking down and the more water/dirt/whatever it can withstand in the brake lines and still be effective, and a higher boiling point, but those two things kind of go hand in hand.