How To: Corksport Type II Rear Bumper Caps

vrracing · 03-23-2012, 08:54 PM

Last week we installed a set of the Corksport Type II Rear Bumper Caps including painting them in the garage. I thought folks might want to see some picts of how it went.

This is the pict from the Corksport site:

The fiberglass was beefy but there was obviously no attempt to test fit them at the factory and the mating surfaces were very different. I know that fiberglass body kits always require professional fitment but I guess CS has always set a high bar for me and I expected more. Near the wheelwell there was a black line and a corresponding indentation in the gelcoat that didnt seem to belong. Not a big deal but I'd prefer not to have to do bodywork on the pretty parts of the piece.

We are subscribed to www.LearnAutoBodyAndPaint.com and if you're interested in doing anything like this it is a terrific resource. Tony video tapes and narrates complete projects and one of them is installing and customizing a fiberglass body kit on a Miata including bumper caps like these. The rear bumper also had a gouge and a corresponding bulge in the urethane on the top of the bumper. Tony has a two different videos on fixing bulges and tears in urethane bumpers. Perfect!

Per Tony's video we used a heat gun, a hammer's wooden handle and wet rag and leveled out the bulge. Then we beveled out the tear and filled it with DynaWeld, a two part epoxy specifically for this type of work.

We trimmed the bumper caps using a dremel with a 1/2" diameter sanding drum. We got the sides pretty good but the backs we could not get flush. We got them consistent side to side.

We then put a 1" piece of masking tape on the inside along the edges where we would be epoxying them to the car. The rest of the inside we put a double coat of bed liner to protect the fiberglass. The CS instructions make a big deal about preventing water sitting on the glass so they are very well protected now.

Once that was dry we test fitted them and then drilled some holes to fix them to the car. You can see in the pict below we got too close to the edge and broke the corner off. Don't do that.

We roughed up the mating areas on the car and the caps with 80 grit. We then masked the outside of the cap and the adjacent parts of the car so that any extraneous epoxy could be easily cleaned up.

Then we coated the previously masked parts of the inside of a cap with DynaWeld making sure that all the exposed fiber glass was coated and therefore protected from water. We also applied it to the corresponding areas on the car. Then we put the cap on the car and put the screws back in. Then we removed the masking tape.

Then we did the same thing on the other side and left the DynaWeld to cure overnight. It cures quickly but that ensures it was really strong.

Note that in his video Tony put the caps on the car with the screws and then molded them in with the Dynaweld. We wanted to make sure it really stuck and unlike the Miata we didnt have a flat area above the cap to mold to.

The next day we removed the screws and then filled the holes with more DynaWeld and we filled the gaps between the caps and the back of the bumper.

We used Rage body filler and 120 grit to get the rough shaping. Most of the work was blending the backs of the caps with the back of the bumper. That took a lot of hand and finger sanding but the results were ultimately very good.

In this pict just before priming you can see near the wheel well where we had to fill the area CS demarcated with the black line.

Here is a view of the primer ready bumper from the back left. Everything has been wet sanded with 320. The bulge and tear were below the right edge of the license plate.

Here are a couple shots of our fancy paint booth. We use 3M VOC respirators but someday may get a fresh air system. The kid also went and bought a bunny suit at HD because the clear makes your body hair all stiff and weird.

At Tony's recommendation we use PPG Shopline products. That is their value line and works well for us. Previously we painted the Tii side skirts and CS Odura lip so had some experience with it. We have an eBay 1.8 HVLP primer gun and a Harbor Freight HVLP 1.4 base and clear gun - the purple one. Both work very well doing body parts with a 20 gallon compressor with a HF air/water separator.

We primered and then used Rage Metal Glaze to get everything perfect. I have had bad luck with the evaporative glazing putties; chunking, not drying, shrinking, etc and as a catalyzed glaze this stuff rocks. Its expensive but I dont want to have to redo everything later. Then we wet 320'd again and reprimered. It all looked great so we 400 wet the primer and put two coats of the the Brilliant Black code PZ followed by three coats of clear. We followed Tony's multi video tutorial on blending at the back of the wheel wells and they came out perfect.

As part of this project we also fully installed the wing. Kevin of Rotary Resurrection told me that he used a Mitsu 3000GT wing on his vert and we'd gotten a black on on ebay a few years ago. It installed easily and fit pretty well but there were gaps where the posts met the trunk lid. So we taped wax paper to the trunk lid and reinstalled the wing after running tape along the bottoms of the posts. Then in the gaps wider than a 1/8th of an inch we used epoxy putty and filled them. Then we filled the rest with DynaWeld.As the epoxy started to harden we pull the tape from the posts. Once that set up and after a bit of sanding we had a wing perfectly matched to the trunk! We primered and painted the wing and three posts along with the bumper.

Once the clear hardened we color sanded with wet 1000, then 1500 and finally 2000. Then used a HF polisher with an orange pad and Meguire's Ultimate Compound. Later, we'll hit it all with a black pad and Ultimate Polish and wax.

Here are some finished shots.

Precolor sanding and polishing

Precolor sanding and polishing

After a wash

It was a fair amount of work but it was fun and we are very pleased with the results. The Corksport Bumper Caps really finish off the back of the car and do a nice job of tying the front lip to the skirts to the back.

Let me know if you have any questions.

reese.leblanc · 03-23-2012, 09:58 PM

Great write up! Thanks for sharing!

JustJeff · 03-23-2012, 10:59 PM

Nice writeup...I've always wanted to see some pics of those. One question, what pedestal wing is that. It seems kinda similar to the Racing Beat one that I covet.

vrracing · 03-24-2012, 02:26 AM

I'm not sure what you mean by "pedastal wing". If you mean the wing on the back of the vert it is a Mitsu 3000GT wing. There are several on ebay pretty much all the time. We painted the wing at the same time as the bumper and in the write up i doc'd what little we did to make it a perfect fit.

Here is a current example on ebay.

03-23-2012, 08:54 PM	#1
vrracing Rotating Assembly Join Date: Oct 2008 Location: TX iTrader: (0) Posts: 102 Rep Power: 17	How To: Corksport Type II Rear Bumper Caps Last week we installed a set of the Corksport Type II Rear Bumper Caps including painting them in the garage. I thought folks might want to see some picts of how it went. This is the pict from the Corksport site: The fiberglass was beefy but there was obviously no attempt to test fit them at the factory and the mating surfaces were very different. I know that fiberglass body kits always require professional fitment but I guess CS has always set a high bar for me and I expected more. Near the wheelwell there was a black line and a corresponding indentation in the gelcoat that didnt seem to belong. Not a big deal but I'd prefer not to have to do bodywork on the pretty parts of the piece. We are subscribed to www.LearnAutoBodyAndPaint.com and if you're interested in doing anything like this it is a terrific resource. Tony video tapes and narrates complete projects and one of them is installing and customizing a fiberglass body kit on a Miata including bumper caps like these. The rear bumper also had a gouge and a corresponding bulge in the urethane on the top of the bumper. Tony has a two different videos on fixing bulges and tears in urethane bumpers. Perfect! Per Tony's video we used a heat gun, a hammer's wooden handle and wet rag and leveled out the bulge. Then we beveled out the tear and filled it with DynaWeld, a two part epoxy specifically for this type of work. We trimmed the bumper caps using a dremel with a 1/2" diameter sanding drum. We got the sides pretty good but the backs we could not get flush. We got them consistent side to side. We then put a 1" piece of masking tape on the inside along the edges where we would be epoxying them to the car. The rest of the inside we put a double coat of bed liner to protect the fiberglass. The CS instructions make a big deal about preventing water sitting on the glass so they are very well protected now. Once that was dry we test fitted them and then drilled some holes to fix them to the car. You can see in the pict below we got too close to the edge and broke the corner off. Don't do that. We roughed up the mating areas on the car and the caps with 80 grit. We then masked the outside of the cap and the adjacent parts of the car so that any extraneous epoxy could be easily cleaned up. Then we coated the previously masked parts of the inside of a cap with DynaWeld making sure that all the exposed fiber glass was coated and therefore protected from water. We also applied it to the corresponding areas on the car. Then we put the cap on the car and put the screws back in. Then we removed the masking tape. Then we did the same thing on the other side and left the DynaWeld to cure overnight. It cures quickly but that ensures it was really strong. Note that in his video Tony put the caps on the car with the screws and then molded them in with the Dynaweld. We wanted to make sure it really stuck and unlike the Miata we didnt have a flat area above the cap to mold to. The next day we removed the screws and then filled the holes with more DynaWeld and we filled the gaps between the caps and the back of the bumper. We used Rage body filler and 120 grit to get the rough shaping. Most of the work was blending the backs of the caps with the back of the bumper. That took a lot of hand and finger sanding but the results were ultimately very good. In this pict just before priming you can see near the wheel well where we had to fill the area CS demarcated with the black line. Here is a view of the primer ready bumper from the back left. Everything has been wet sanded with 320. The bulge and tear were below the right edge of the license plate. Here are a couple shots of our fancy paint booth. We use 3M VOC respirators but someday may get a fresh air system. The kid also went and bought a bunny suit at HD because the clear makes your body hair all stiff and weird. At Tony's recommendation we use PPG Shopline products. That is their value line and works well for us. Previously we painted the Tii side skirts and CS Odura lip so had some experience with it. We have an eBay 1.8 HVLP primer gun and a Harbor Freight HVLP 1.4 base and clear gun - the purple one. Both work very well doing body parts with a 20 gallon compressor with a HF air/water separator. We primered and then used Rage Metal Glaze to get everything perfect. I have had bad luck with the evaporative glazing putties; chunking, not drying, shrinking, etc and as a catalyzed glaze this stuff rocks. Its expensive but I dont want to have to redo everything later. Then we wet 320'd again and reprimered. It all looked great so we 400 wet the primer and put two coats of the the Brilliant Black code PZ followed by three coats of clear. We followed Tony's multi video tutorial on blending at the back of the wheel wells and they came out perfect. As part of this project we also fully installed the wing. Kevin of Rotary Resurrection told me that he used a Mitsu 3000GT wing on his vert and we'd gotten a black on on ebay a few years ago. It installed easily and fit pretty well but there were gaps where the posts met the trunk lid. So we taped wax paper to the trunk lid and reinstalled the wing after running tape along the bottoms of the posts. Then in the gaps wider than a 1/8th of an inch we used epoxy putty and filled them. Then we filled the rest with DynaWeld.As the epoxy started to harden we pull the tape from the posts. Once that set up and after a bit of sanding we had a wing perfectly matched to the trunk! We primered and painted the wing and three posts along with the bumper. Once the clear hardened we color sanded with wet 1000, then 1500 and finally 2000. Then used a HF polisher with an orange pad and Meguire's Ultimate Compound. Later, we'll hit it all with a black pad and Ultimate Polish and wax. Here are some finished shots. Precolor sanding and polishing Precolor sanding and polishing After a wash It was a fair amount of work but it was fun and we are very pleased with the results. The Corksport Bumper Caps really finish off the back of the car and do a nice job of tying the front lip to the skirts to the back. Let me know if you have any questions. __________________ 90 S5 Vert. JDM Tii with BNR Stage1 turbo. Pineapple Racing street port. Bonez cat-forward. Corksport cat-back with Vibrant UltraQuiet resonator. RTek 2 wZeitronix w/b. HKS EBC. Vis CF Tii hood. 3000GT wing. Ground Control coilover kit with KYB AGX shocks. Red and Black leather RX8 seats. Corksport Odura lip & bumper caps, OEM Tii skirts

03-24-2012, 02:26 AM	#4
vrracing Rotating Assembly Join Date: Oct 2008 Location: TX iTrader: (0) Posts: 102 Rep Power: 17	I'm not sure what you mean by "pedastal wing". If you mean the wing on the back of the vert it is a Mitsu 3000GT wing. There are several on ebay pretty much all the time. We painted the wing at the same time as the bumper and in the write up i doc'd what little we did to make it a perfect fit. Here is a current example on ebay. __________________ 90 S5 Vert. JDM Tii with BNR Stage1 turbo. Pineapple Racing street port. Bonez cat-forward. Corksport cat-back with Vibrant UltraQuiet resonator. RTek 2 wZeitronix w/b. HKS EBC. Vis CF Tii hood. 3000GT wing. Ground Control coilover kit with KYB AGX shocks. Red and Black leather RX8 seats. Corksport Odura lip & bumper caps, OEM Tii skirts Last edited by vrracing; 03-24-2012 at 02:34 AM..

03-23-2012, 09:58 PM	#2
reese.leblanc Doing my own thing Join Date: Feb 2008 iTrader: (2) Posts: 209 Rep Power: 17	Great write up! Thanks for sharing!