Project Fiesta ST-Improving the Brakes with mountune USA

by Mike Kojima

So far we have improved the handling and shifting on our Project Ford Fiesta ST with some stuff from ST Suspension and mountune USA.  We are very impressed with the base car.  If you are into tuning FWD Sport Compacts you can really appreciate just how good this car is from the factory. If you have built Turbo Hondas or perhaps a Sentra SE-R we equate the Stock ST to one of those cars with a T28.

The car is a lot of turbo fun but with solid OEM reliability, great handling and OEM refinement. On the track the car has proven to be exceptionally reliable putting down lap after lap with not a single problem.  No overheating, no fade, no unbalanced handling and most of all, the brakes are up to snuff for track abuse even stock!

We did want to improve them a bit though. Our OEM fluid was getting heat cycled and thrashed and the brake pedal was getting spongy.  Now was a good time to get some better brake feel with some mountune braided steel brake lines and improve fluid fade resistance with some Motul RBF 660 brake fluid.

Read more on the Fiesta Project

We first began work on Project Fiesta ST's brakes by putting the car on the rack and replacing the stock brake pads with new stock brake pads as well as removing the stock rubber brake lines. When running on the track with street compound UHP tires, surprisingly the stock pads will hold up to lap after lap of pounding with little fade.  This will probably change with R-Compound tires but for now stock is great!
Here is the mountune brake line laid out next to the stock Ford part.  The mountune line is made of teflon lined braided steel.  Its principal advantage is that it will not expand under normal brake operating pressures like the stock rubber part.  The expansion of the stock part is significant and has a big impact on the brake pedal feel contributing to pedal free play and mush. 
The mountune brake lines fit perfectly using all of the stock hardware.  This is actually a pretty impressive fit.  This is important for the front wheels since they must pivot for tuning and excessive line can snag or whip. 
The fit into the stock chassis hangers is quite good as well.
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Monday, September 29, 2014 9:22 AM
What is the silver box on the front strut (faces forward)?
Mike Kojima
Mike Kojimalink
Monday, September 29, 2014 9:43 AM
They are mass dampers. We explain them in our first story.
Monday, September 29, 2014 12:12 PM
Can you quantify the swelling of stock rubber lines compared to braided stainless?
Mike Kojima
Mike Kojimalink
Monday, September 29, 2014 4:51 PM
Well we could do an elaborate test to do that or you can just take my word for it because I am not going to do an elaborate swelling test! :)
Monday, September 29, 2014 6:12 PM
I'll take your word for it! It's just I've heard opinions from other engineers that new rubber type lines have a negligible expansion relative to the braided lines. Also that any swelling of rubber lines is insignificant compared to other sources of compliance like caliper or firewall flex. I was hoping maybe you were aware of white paper on the subject, I spent some time searching online and I was unable to find anything. I would think if there was a significant difference in swelling, that the manufacturers of the braided lines would be keen to tout it for marketing purposes! Or you would see them as OEM equipment on high end sports cars, neither of which I've seen.
Mike Kojima
Mike Kojimalink
Monday, September 29, 2014 9:54 PM
The amount of fluid movement in a brake system is pretty small so these things make a pretty big difference. Adding braided steel lines on any car usually makes a pretty decent difference that is easily felt.

Several things that keep the braided lines from oem use are one cost and two some difficulty in passing the DOT whip test. The hard plastic sleeves on the lines are for strain relief and also to prevent a stress concentration during the whip test.

Conversely, you never see a race car with rubber lines.
Tuesday, September 30, 2014 8:12 AM
The OE pads on the FiST are good...but they just can't stand up to the stress of my home track, Hallett, that is only 1.8 miles and several heavy braking zones with short straights that follow.

I'm about halfway through my second set of OE pads in ~6700 mi

This last track day, I only went out for two sessions and the rotors were glazed over somewhere around 4-5 laps. Pedal has been pretty solid, but started softening early in the second session. I'm thinking brake ducts will be my next project.
Tuesday, September 30, 2014 11:02 PM
I know that the pedal feel changes remarkably with stainless lines, and is well worth the cost IMHO. It makes other upgrades like a MC Brace feel even better. I'm now at the point of wanting to remove the BB just to improve the pedal feel.
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