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TRP Parabox Disc Brakes

Review: TRP Parabox Disc Brakes

shackett's picture

We Liked

That finally the rank and file CX racer can have hydraulic disc brake performance. Disc brakes for CX and Road I firmly believe this is one technology that should have been driven by the main consumer being the non UCI racers and recreational cyclists rather than the idiotic UCI regulations. There still will be naysayers that CX and Road bikes do not need them for all kinds of reasons even the idiotic purist argument. Whatever the argument against the same thing was said about mountain bikes. I am no stranger to disc brakes on my mountain bikes and really could not imagine not having hydraulic disc brakes especially on my DH bikes.

Purists go ahead stay in the dark ages ride steel frames with friction shifting, and wood rims. The fact is, in then next few years I do expect disc brakes to be the norm on CX and even road bikes no matter what the UCI rules will be. In the works are integrated fluid reservoirs in the electronic shifters by Shimano, Campy, I am unsure as to what SRAM has in the works. The writing is on the wall as the uniform braking performance in all weather conditions with disc brakes is undeniable. Other benefits not so evident are better rim design, as the rim will no longer act as the braking surface. The overall structure of rims will become stronger as no heat cycling and wear to the rim a benefit to both alloy and carbon construction. Currently most road & the new wider CX rims designs in many cases are just repurposed standard rim design that's is still engineered for rim braking.

Most new disc brake CX bikes are equipped with any one of several cable disc brakes, these cable discs do provide better braking than both CX style cantilever and road dual pivot brakes. Though non of the cable pull designs are much different the other in basic design and function. There are issues like mushy or hard lever feel, something you really do not notice till you have used a well designed full hydraulic system. Ever drive a car without power brakes or power steering, then drive one that does? Some of the feel issue can be addressed by the use of a compressionless cable housing, there still is the issue of only one pad moves to make contact with the rotor, the non moving pad needs to be continually adjusted manually if not there is rotor deflection that will cause uneven rotor and pad wear even warp for those heavy on the brakes.

Weight wise even the lightest cable system both the calipers alone weigh more than the calipers, junction box, hose and fluid, post mount bolts for the TRP Parabox system total of 528g. The weight of 160mm rotors 95g each, mounts and hardware 13g an end are about the same for either, add in the increased weight of cable housing the difference is quite amazing.

So should you upgrade your new disc bike with a full hydro system? Undoubtedly yes.

How is the TRP Parabox disc brake system to install and set up?

The Parabox brake system comes fully assembled, pre-bleed and ready to install though most will need to shorten the lines. First order of business when installing is to remove the bar and stem from the steer tube, the junction box bracket will take the place of a 5mm spacer so keep this in mind if you happen to have no spacers for your stack height you will need to find a less tall stem or get a new fork though for most CX bikes this is not an issue. Install the junction box, reattach the stem and then attach the calipers with the supplied stainless hardware no need to tighten it all down just yet as you are just test fitting to measure how much the hose need to be shortened, I ride a 53-54cm frame so I needed to.

Once the lines are at the correct length the system will need to be bleed, I suggest doing this on the bench and not on the bike as the junction box needs to be tipped on it side as the final step. The instructions suggest tipping the entire bike on it side while you are holding the bleed hose on, but if it slips off air is introduced into the system and you start all over so bench bleeding is a must with the Parabox. I tried several times as shown in the manual and was only frustrated trying to hold the hose on undo the work stand clamp, holding on to the bike all without fluid getting all over the place or dropping the bike. You will also need to purchase separately the TRP Tektro bleed kit.

Reinstall the junction box, stem and calipers but do not tighten it all down. Next is to measure and cut the short cable housing sections that will run from the levers as usual to the noodles that connect to the junction box this may take several times of cutting to get it just right be sure you have the noodles and cables going the correct brake line. Mine are set up Euro style so right is front and left is rear doing this the noodles crossed in front.

Run the cable though as you normally would threading through the noodles, through the lower section of the Parabox and linkage arms, there is linkage set up pin to set the arms in place while tightening the anchor bolts with a 2.5mm Allen wrench and 9mm open box wrench while holding the cable taut. I found it best to do this with the Parabox not attached to the steerer, tighten the cables down then attach to steerer reinstall stem & bar.

Install the rotors on the wheels if not already done, install the wheels, to center the calipers on the rotors with the caliper mount loose squeeze the lever, make sure both pistons move the same amount if not pry back so they are even, then squeez lever hard to hold caliper in place and tighten the bolts. Spin the wheel repeate if needed, once all is turning smoothly torque all the bolts to spec using a quality torque wrench like the Effetto Mariposa Giustaforza II PRO. Wrap the bars and you are ready to bed the pads to the rotors.

To bed in pads you need to cycle the brakes 10-15 times without coming to a complete stop allowing the rotors to cool between each cycle. I did this by riding up the hill in front of my home coasted down applied the brakes to slow then road back up. This procedure should be done each time the pads are changed. You are now ready to ride though take it easy for the first several braking sections, as the brakes will not achieve full power till 30-40 cycles. Once installed the Parabox is far less maintenance cantilevers a big plus.

How do the Parabox brakes work?

Overall a massive improvement over cantilevers I rode them in all kinds of conditions even made my own mud pit, purposely threw mud on them dowsed with water the braking was always consistent as I expected. In very cold weather under 20 degrees I did find a slight decrease in responsiveness this is due to TRP using a mineral oil based fluid there are benefits to using a mineral oil fluid namely it does not attract moisture as DOT fluid does.

With the Parabox disc brakes racing there is the added benefit of when a wheel change is needed, different width rims are not an issue or knocking the pad set up when installing a wheel are gone! The lever feel and modulation of the Parabox is good but not the best when compared to that I have used on my mountain bikes but is more than suitable for CX use and fare superior to cants and better than any of the cable disc brakes I have tried. Full power wise if you have not used disc brakes before you will need some time to adjust to the power.

I do think the feel could be improved with a smaller I.D. hose, and larger fluid reservoir. I was able to improve the lever feel close to what I liked by adjusting the bite point of the piston at the lever arm adjuster by moving it in or out. Note this is not described in the manual.

How do the Parabox brakes look on the bike?

At first glance anyone will notice you have disc brakes. Personally I think the TRP Parabox looks really cool especially in the white that was sent to us. I would prefer that the junction box and calipers be anodized rather than paint as I did have some of the paint rub off quite easily. Some people have commented they do not like the looks as it ruins the lines of the bike and only view the junction box approach as a stop gap till hydraulic reservoirs are inside the shifter/brake lever. Even then there will be a need for a Parabox type system as not everyone will want electronic shifting or can even afford it, there is then the problem of when a lever is broken or something wrong with the electronics it is an expensive fix the whole system needs to be disconected not the case with the TRP Parabox.

We Didn't Like

Bleeding Procedure is complicated even for a Hydraulic system.

Painted Surface – Anodizing would look better and is more durable aftre short use already had many scraches and worn off paint.

Modulation not as good as it could be but I’m very picky about this.

The Final Say

Either you are upgrading a Disc brake CX bike or building a spec bike as we did with Project Privateer Litespeed CX Ti, the TRP Parabox is an excellent choice for disc brakes on a CX bike. The Parabox system is lighter than a cable system when the complete system is added up. The calipers do not need to be manually adjusted as do cable systems they are less bulky, they look better and have overall performance a cable system or cantilevers cannot match. At $469 MSRP they are not as inexpensive as a cable set up but not for off the price of the TRP EuroX Magnesium cants some of the lightest cants out there a modest weight penalty ~ 300g. Personally I am willing to make the trade off for the increased performance, easier wheel changes, better reliability and less overall maintenance.

About Hydraulic Brake Fluids:

About Hydraulic Brake Fluids: Two types of fluids are typically used in braking systems; DOT Brake Fluid and Mineral Oil. The two groups have different base chemical compositions and properties and should not be mixed or substituted for in a brake system. Mixing or substituting these types of fluids will destroy rubber and plastic components within the system. It can also alter the performance characteristics of the brake system.

DOT Brake Fluids

DOT brake fluid is approved by the Department of Transportation for use in brake systems and is required to meet certain performance criteria, mostly consistent performance within a specified temperature range. DOT 3, 4 and 5.1 fluids are hygroscopic (water absorbing) glycol based fluids. These fluids absorb water at a rate of 2-3% per year. The result of this is a lower boiling point of the fluid because it is diluted with water. Brake fluid will not boil while under pressure. The automotive industry and all high end motorsports use DOT fluid for their braking systems. DOT 5 brake fluid is silicon based and should not be mixed with the glycol based fluids.

Mineral Oil

Mineral oils are also used in brake systems but are not controlled by any specific standards. Mineral oil does not absorb water and can break down with time and heat. Low ambient temperatures will cause a mineral oil to congeal and the system to have sluggish performance (<20ºF). Some mineral oils are more environmentally friendly than DOT Brake Fluid, however oil is still an oil and should be disposed of properly.

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