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Old 02-09-2013, 09:10 PM   #1
Scooby Newbie
Member#: 171376
Join Date: Feb 2008
Chapter/Region: South East
Location: Florida
2002 Impreza WRX

Default DIY: WRX Brake ducts.

I realize there are brake duct options out there and the cheapest option for WRXs is the "Quantum Motorsports (now Lambert Automotive Performance).

These are relatively cheap and not a bad option BUTTT, when installed, the outter tie-rod end and lower ball joint do not have heat protection. In my opinion, if you are generating enough heat in the braking system to need brake ducts, I would think that the ball joints will need protection from the heat.

RCE engineering does have a design out for newer STIs but I'm pretty certain the hub layouts are different. Also this being said I found ducting mounts for the spindle on Ebay as well that are the same style as the Quantum Motorsports ones but they are for 5x114.3 hubs only.

I used both of these ideas to make my own. Also i referenced Porsche air guide duct designs at the same time.

Here is my Production!

Parts needed:
1. x2 18" x 20" 18 gauge sheets of steel (sold at home depot and probably lowes. 20-22 gauge will work as well)

2. 8-12" of 3" steel exhaust pipe. (or any steel 3" pipe. Note: thinner the wall the better)
3. x6 8 x 20mm 1.25 thread bolts (hardware store, lowes, home depot)
4. x24 washers that fit the bolts. (hardware store, lowes, home depot)
5. door trim protection strip (usually sold at autozone/advance auto.
6. 12' of brake ducting (local speed shop or online, use google)
7. OEM foglight surrounds
8. 4" to 3" ventilation duct adapters for microwave/range hood vents (home depot, lowes)
9. x6 3 1/2" hose calmps for ducting (lowes, homedepot)
10. 3m or other reputable named epoxy (lowes, home depot, hardware store)
11. x12 steel 12-15mm rivets (larger the better)(lowes, home depot, hardware store)
12. x24 washers that fit rivet diameter perfectly (lowes, home depot, hardware store)
13. cotter pin variety pack (lowes, home depot, hardware store)
14. thin cardboard
15. x2 10 x 12 x 1.50 bolts and nuts

Tools Needed:
2. black sharpee
3. jack (2-ton minimum recommended)
4. x2 jack stands (2-ton minimum recommended)
5. razor blades (drywall knife works well)
6. jigsaw with metal blades
7. heat gun
8. flat head screw driver
9. 6mm alan/hex bit (3/8" socket recommended)
10. sockets :12mm, 13mm, 14mm, 17mm, 19mm,
11. tin snips
12. protractor
13. dikes tool
14. multiple pone books
15. white crayon
16. drill bit variety pack
17. drill
18. tape measure (recommend 6ft minimum)
19. wrenches: 13mm, 14mm, 16mm, 17mm, 19mm
20. braker bar
21. torque wrench

Lets begin!

If your cars ride height is high enough to fit a jack under the engine all the way back to the subframe, good. If your vehicles ride height is too low, I suggest getting 2x4 pieces of wood to drive the front wheels up onto.

Once the vehicle is at a suitable right height, stick jack under oil pan all the way back to the square piece of steel that is held to the subframe with 4 bolts. It is safe to jack the vehicle up from this point. Aim the jack pad to where when jacking up the pad will securing be seated on this panel.

Prior to lifting the vehicle, use braker bar and 19mm socket or tool needed for different lug nuts and brake loose lug nuts.


Lift the vehicle up high enough to place the jack stands under the factory lift points by the rocker moldings on each side of the vehicle behind the front wheels. Finish loosing front wheel lug nuts and remove wheels.

Now that the wheels are off and vehicle is secured on the jack stands having the front of the vehicle in the air only; insert ignition key into ignition and turn on then off. Leave the key in the ignition because the spindles will need to be turned many times.

To remove calipers, take braker bar and 17mm socket and brake caliper bracket bolts loose and remove. I would suggest using long zip ties to suspend calipers in the air so the brake line is not strained from hanging. Ziptie the calipers to the springs on the struts, no need to tighten ziptie all the way just enough to relieve tension on the brake line.

Now that the calipers are off the rotors should come right off without issue. Mark the rotor backing plates of which side is which. Remove brake rotor backing plates using a 12mm socket and ratchet.

Now that you have the backing plates of take thing cardboard sheet and black sharpee and draw outline of backing plates and holes. Use scissors to cut out drawn template and drawn holes. Test fit template to spindle using factory bolts to ensure bolt pattern alignment and be sure to assign each backing plate template the proper side. If holes line up without issues great, If not, remake templates with more cardboard.

Due to the level changes in the factory backing plates the cardboard cutouts will not fit flush against the spindle, do not worry.

With the cardboard template bolted to spindle, look from back side of template (side closest to ball joints) and draw outline of spindle onto cardboard using black sharpee. Leave section marked because this will be referenced later.

Take a rather long piece of cardboard and bend and fold to fit against towing mounts on subframe and against lower control arm.

This is to make templates for Porsche style Guide ducts. I did not list material for this due to the many options that can be used to make these. I used a material called kydex which is more durable then lexan and easily moldable.

For those of you interested in doing both the next steps are coming. For those who are interested only in the rotor backing plate ducts please skip forward a few steps and continue on. Thank you

When a piece of cardboard has been measured and bent to a ideal angle (keeping wheel width and travel during turns in mind). Drawn carboard outline onto chosen material to be guide duct. Use jigsaw to cutout material.


If using kydex, use heat gun to imitate bend made in cardboard to get proper bend to match from towing mount to lower control arm. Trim off excess closest to spindle.

Hold guide duct at desired level to not drag on ground, use white crayon to mark a line at top of nut for lower ball joint on bottom side of lower control arm. Also mark both sides of tow mount. You may leave this project alone for a few and let material cool down from being heated.

BACK TO BACKING PLATES. Now that the cardboard template has been made, take the steel sheets and draw outline of cardboard template to steel sheet. (Note: If sheet is covered with oil, standard rubbing alcohol and a rag will clean of the oil residue to allow marker to transfer ink to metal)
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Old 02-09-2013, 10:07 PM   #2
Scooby Newbie
Member#: 171376
Join Date: Feb 2008
Chapter/Region: South East
Location: Florida
2002 Impreza WRX


Using the tin snips, you should be able to cut the outline of the steel sheet. Be mindful of sharp edges from cutting. During the template outlining and drawing, the spindle bolt holes should have been drawn on as well. You will need to match up a drill bit to hole size and drill out wholes. Do not fret if holes are larger then bolt thread thickness.

Once Steel plates are cut out, test fit to spindle referencing proper sides and ensure easy fitment. Most likely factory bolts are long enough to hold the new backing plates on so now use the 6 bolts referenced in parts list to loosely hold backing plates on.

Take 8-12" 3" pipe and cut directly in half using jigsaw again with metal bit. Be careful.

Take one half of the pipe and hold at 40 degree angle above the speed sensor. holding that, draw line on pipe vertically and parallel to back plate, do the same horizontally for spindle, now you have lines of which to cut sections out of pipe. Do so again with jigsaw very carefully.

Once pipe is cut check fitment to backing plate and spindle. Once fitment is optimum, outline pipe on backside of backing plate. Using tin snips to cut inside of outline just drawn. Removal of backing plate necessary. Once the pipes and backing plates are setup, take to local machine shop or good speed shop and get pipes welded to pertaining sides on proper sides of backing plates. I would recommend marking them in a way best for you to remember to match the pairs.

Once they are welded, reinstall and check fitment again, grinding may be necessary and which you will now need a die grinder.

Once fitment is desirable, take door jam protection trim and install to speed sensor side of the pipe to protect harness wire from chaffing and damage from pipe.

Remove backing plate with pipe and fit jigsaw closest to backing plate and cut excess pipe off, you will need the excess later. If painting backing plate desired now is a good time unless producing lower guide plate as well.

If building lower guide duct, leave backing plate installed and build bracket from excess steel sheet to be riveted to back side of guide duct above white line drawn earlier for lower control nut.

Once bracket is built. Remove cotter pin from lower ball joint nut and use 19mm socket and braker bar to loosen and remove. Find appropriately sized drill bit to match diameter of threads for lower ball joint. Hold guide duct up and place bracket at bottom of thread section of lower ball joint and draw outline of threads to for a point of drilling a hole. drill hole. Reference marks made at front side of guide duct at tow mounting, drill hole at tow mounting for larger 2 bolts and nuts referenced in parts list.

Install guide duct. With guide duct and backing plate installed, turn spindle as if turning steering wheel to make a turn and check clearances, if contact exists, remove material from guide duct.

(Note: Trimming may be required to clear tie rod and to clear wheel during clearing and with vehicle at ground level. to check wheel clearances, put rotor on hub, rebolt wheel on finger tight and turn as making turn and check and alter as per needed)

Once guide ducts have been altered for final fitment, install. Once backing plate has been altered for final fitment, Check spindle location and guide duct location and outline open space between lower ball join and tie rod ball joint and cut section off of backing plate. paint backing plate. Once backing plate is painted, take the 24 washers referenced earlier that fit bolts and fit 4 washers behind backing plate at each bolt whole and bolt onto spindle. check rotor clearance of bolt heads and backing plate. less washers may be needed. Install backing plate, rotor, caliper.

Now to foglight surrounds.

Using vent ducting adapters and jigsaw, cut to fit around foglight hole on foglight surround. Once fitment is easy and easy to install on and off, scratch surfaces on back side of foglight surround and inside and outside of vent ducting adapter closest to mount point of foglight surround. using epoxy, apply epoxy to contacting points of foglight surround and vent adapter and place painted side of foglight adapter down on smooth clean surface and place phone books on top to hold pressure down on adapter to allow proper placement during epoxy cure time.

^^ Not good unless track car only^^^

During the drying time of of the epoxy, take brake ducting hose and start on passenger side first feeding from bumper back. I did not round straight back or along inner fender well because my first attempt did not allow for a lot of steering angle and the hoses were damaged. Here is the routing I chose the second time and so far so good. be sure to secure ducting hose to pipe on backing plate with one of the hose clamps.
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Old 02-09-2013, 10:07 PM   #3
Scooby Newbie
Member#: 171376
Join Date: Feb 2008
Chapter/Region: South East
Location: Florida
2002 Impreza WRX


Once ducting is routed and secured in preferred fashion, reference excess 3" piping cut off from backing plates. Paint excess pieces desired color. Go back to foglight surrounds with glued adapters and cut 4 slits around inner 3" diameter to allow flex. Take excess metal pipe and put in to plastic adapter and secure with one of the hose clamps.

With brake duct piping installed and routed, leave about 4-6 inch excess sticking out of front bumper. place hose clamp on duct and then take foglight surround and install duct piping to excess metal pipe and secure with hose clamp. Install surround to bumper and push in extra ducting into bumper.

My apologies for any vague steps but each person has their own idea and mine may not always be the best. Most of the materials I already had so I don't know pricing except for the duct hose was about $90.

Thank you and hope some of this may be helpful.
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Old 02-10-2013, 12:25 AM   #4
Scooby Specialist
Member#: 198372
Join Date: Dec 2008
Chapter/Region: South East
Location: The Former Space Coast
2006 WRX TR VF43
WRB Camo


Awesome write up sir! Nice work
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Old 02-10-2013, 07:55 AM   #5
Scooby Newbie
Member#: 178770
Join Date: Apr 2008
Chapter/Region: NESIC
Location: Western,MA
06 STi
04 FXT


Good job! Is that satin or matte paint/wrap? Looks nice.
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Old 02-10-2013, 10:09 AM   #6
Scooby Newbie
Member#: 171376
Join Date: Feb 2008
Chapter/Region: South East
Location: Florida
2002 Impreza WRX


Satin Paint job. Door jams and all.
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Old 02-10-2013, 01:51 PM   #7
Scooby Specialist
Member#: 119397
Join Date: Jul 2006
Chapter/Region: NWIC
Location: Snohomish
1998 L
Red & Black


Great write up, this makes me want to try it myself.

Do you have a link to the material you ordered...kydex.
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Old 02-10-2013, 06:49 PM   #8
Scooby Newbie
Member#: 171376
Join Date: Feb 2008
Chapter/Region: South East
Location: Florida
2002 Impreza WRX


this is a pretty good link for Kydex sheeting. Searching wouldn't hurt but this is a good source. http://www.professionalplastics.com/KYDEXTSHEET
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Old 09-03-2013, 12:22 PM   #9
Scooby Guru
Member#: 149262
Join Date: May 2007
Chapter/Region: MWSOC
Location: Grand Rapids MI
03WR Rally/XTDD/98SJ


Nice job!!!!
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