Bumper Scratch Repair

If you’ve read any prior posts on this blog, you know I’m a huge fan of Dr. Colorchip. For small paint chips and scratches, the good doctor cannot be beat. But when the chips and scratches get bigger, the repair isn’t usually as simple. So I thought I’d try out some other products on the market to see if they work as advertised. Today I’m trying the ScratchWizard system.

First some background. I bought a 2013 BMW X5 in the fall of 2017. Although it came equipped with Park Distance Control sensors and cameras (back and side), the previous owner (aka Mr. Magoo) managed to scrape some paint off of all four corners. I bought a bumper repair kit from the ScratchWizard last November, and it took until May before the weather was nice enough for me to use it.

I followed the video instructions more or less, starting with two problem areas. First was this huge chip and scratch on the top edge of the bumper cover.

And secondly, a large scrape along the fold. One good thing about the color of this vehicle is that it hides scrapes really well, and I didn’t initially see this scrape until I started to work on the other one.

I didn’t want to use filler on plastic so I tried my best to repair the areas just by sanding before using the primer.  The key I’ve discovered is to go big.

Take advantage of the natural panel seams and plan ahead where you want to blend  into the original paint.  If you mask off a small area, you’ll get hard lines and the repair will be more obvious.

Follow the instructions allowing 10 minutes between coats, and 30 minutes between primer and color, as well as color and clear. Each step involves a light initial coat, followed by two medium-heavy coats.  You want good coverage, but you don’t want the paint to sag. Metallic paint is usually tough to match, but this came out pretty well.

I’m really happy with the result.  Once the paint has hardened for another month, I’ll level the clearcoat with Meguiars 105. Result.

Corner Weight & Cross Weight

One of the additional benefits of an adjustable suspension, besides being able to dial-in ride-height and rebound, is the ability to corner weight the car. “Corner weight” refers to the static weight at each of the four wheels.  50-50 front to rear weight distribution is ideal to maximize handling on most road cars, but a distant pipe-dream for MINI owners. “Cross-weight” compares the lateral total (Rear Left + Front Right) to the total weight. If that percentage is over 50%, that’s called “wedge” in NASCAR terms. (Reverse wedge if under 50%). Corner-weight can be changed by adding ballast if necessary to make a weight minimum, or making, adjustments to spring perches and sway-bar pre-tension in an attempt to equalize the weight at each wheel. But more importantly, what matters for handling is near 50% cross-weight in a FWD car.

Take my car as an example: I have an R53 with a rollbar, AC delete, race seats, and a gutted interior. With driver and a full tank of gas, my car weighs 2,685 pounds. 61.8% of that weight is in the front; 38.2% is in the rear. That is slightly better than stock which had a weight of 2,853 (with driver) and 62.7/37.3 weight distribution.

The first time we attempted to corner-weight my car, I only had an adjustable suspension to work with. I didn’t have adjustable drop-links on the swaybars. That resulted in a cross-weight of 52.4%. That isn’t terrible, but still helped to contribute to under-steer in left turns due to wedge. We installed Alta adjustable drop-links on both swaybars, and without adding any ballast, tried again. The results are below:

Each corner is within 5 lbs. of the target weight. Cross-weight is 50%. The car now seems very neutral in left or right corners, which for MINI means equal understeer in both directions, as opposed to excessive understeer when turning left. Result.

Read more about cross-weight at GRM. If you want someone to do the math for you, see this  corner balance calculator.

BMW Sets World Record for 8 Hour Drifting

BMW recently reclaimed the Guinness World Record for the longest drift, drifting 232.5 miles over 8 hours in the new BMW M5.

I was recently attending a seminar at BMW NA HQ and they have the vehicles on display in the lobby.

I found a few of the details interesting.  At about 1:50 in into the video, you’ll see the two cars come together.  Even though they were traveling at about the same velocity and just a few inches apart, it still made a decent dent.

I also appreciated the four cup holder on the passenger seat, which makes sense if you’re going to be in the car for 8 hours, you want to stay hydrated. But it makes you wonder if the driver Johan Schwartz also had the stadium pal. I also like the way the pump controls were integrated into the center console.

The driver called for refueling using the bluetooth connection to his phone.  He had to reestablish the pairing of his phone and the car a few times over the 8 hour period.  If you’ve ever used the BMW iDrive controller, you know that in itself deserves a Guinness record. (I can’t get that to work while I’m in my driveway, let alone mid-drift.)

The fuel line and return pass through the side rear window into the fuel cell in the trunk. As stated in the video, their biggest concern was fire so there was a fire suppression system in the trunk and special vents were added so the trunk would vent to the outside.

Rolex 24 Hours of Daytona

It has been a little over a month since this year’s Rolex 24 hour race at Daytona. Rather than recap the racing action, I thought I’d reflect on the event. It was my first time at a 24 hour race and my first time at the Daytona International Speedway. Neither was what I expected.

The speedway is both larger and smaller than you expect.  Imagine a super-sized baseball stadium, with all of the modern amenities you’ve come to expect over the last 20 years. Cut that stadium in the middle of center field and unwind it so it’s just one long straight, and bend it slightly around the start-finish line.  I guess you would describe it as a flat C or “(“. Add seating for 100,000+ people, but only fill it with 5,000. Take another 40-50,000 people and scatter them throughout the infield. That’s the Rolex 24 crowd.

You can move freely from Grandstands to Infield, but allow 20-30 minutes for the trip as you have to exit the Grandstands and take a trolly (or walk) through the tunnel to get there. Consider driving and parking in your favorite care corral (BMW, Porsche, or Corvette) or signing up for a luxury package from Audi to enhance your experience.  Grassroots Motorsports offers some excellent packages (we had the Stadium Ticket Package), and their Sunday morning breakfast may be the best bargain going.

The hardest thing is figuring out where you want to be.  From high in the Grandstands you can see the entire track above turn 1. With an optional garage pass you can walk among the cars and mechanics in the garages. Your best close up views are in the infield (turns 3, 4, 5). RVs and campfires fill the infield.  Most of the car clubs have tents with refreshments in the infield that provide a respite from the weather.  You can’t really escape the noise, but you don’t want to either.

You do want to think about your strategy for the 24 hour period. The race starts in the afternoon and runs about 4 hours before it starts to get dark. The transition into sunset provides some of the best action. We stayed into the early evening and then came back early morning. We were staying over an hour away from the track and would stay closer next time.  This year was interesting for the lack of extended caution periods or weather delays, but because IMSA got the balance of performance wrong, also didn’t have very exciting racing. It did set a record for most laps and longest distance run.

It is interesting to note that the previous track record from 1970 of 724 laps (2,758 miles) on the old road course (without the bus-stop) by a Porsche 917 in the top class was beaten by the Ford GTs in the GTLM class (2,787 miles). The 6th place Porsche RSRs,  missed that record by only 3 miles. This is truly the golden age of sports car racing.

(See this link on Flickr for my photo gallery.)

Scratch and Dent Removal

This is turning out to be a much colder winter in the Mid-Atlantic region than originally planned.  As a result, I’m falling behind in sorting the X5. This past weekend was the first since early November where I could get out and work on it.  The previous owner (Mr. Magoo) managed to scrape paint off of all four corners and dent the lower valance. It’s been too cold to try to repaint the big scrapes, but this past weekend I tackled some of the deeper scratches and the valance dent.

First off, it takes a certain talent to perfectly dent plastic without breaking it.  Because the PDC sensor is also damaged, perhaps Mr. Mr Magoo hit something larger, but this dent was about the size of a baseball. (It was actually much larger than it looks in the photo.) I wanted to see if I could get it out with just heat and some simple pry tools while I had the weather on my side.


Once I gained access behind the dent, I slowly heated the plastic until it was warm to the touch.  Then using the flexible pry tool, I slowly pushed it back into shape from behind. It isn’t perfect, but it looks better than before.

While waiting for the valance to cool down so I could put everything back together, I grabbed the random orbital polisher and a microfiber cutting pad.  The clear-coat on BMW bumpers is pretty robust, so I thought I’d see how well Maguiar’s M105 polishing compound levels the paint and helps to reduce the scratches.

These scratches are pretty deep, but not down to the color coat. I took two passes with the M105 before switching to Griot’s Machine Polish #3, and sealed it with a layer of AmmoNYC Skin. The result being that the scratches are not really visible after you get about a foot away from the surface.  I probably could have gone a little further, but didn’t want to risk burning through the clear-coat.