New Studs Installed

New Wheel Studs

I finally got a couple of days this past week where the temperature in the garage was above 45 degrees so I started to prep the MINI for the upcoming track season. No major changes are planned this year, just routine maintenance items. First up is to inspect the brake calipers and change the wheel studs. For the brakes, I’m checking the condition of the brake lines, cleaning the calipers and carriers, inspecting the piston dust boots, and torquing all of the bolts to spec. Track pads will come later. [And since someone will ask, the rotors at the top of the post are not cracked. That’s just discoloration from the brake pads contacting the rotor when the parking brake is engaged.]

Because my car is outside most of the time, I like to replace the wheel studs every other year. This has been an especially harsh winter so they are really very corroded. The process is not difficult, but getting good leverage in a tiny garage without a lift can be a challenge. Here’s the method that works for me.

Nut to nut

Remove the caliper, carrier, and rotor. Remember support the caliper by something other than just the brake-line (like a hanger or box.) If you’re removing old wheel studs, you’re going to need some leverage to overcome the sheer force needed to get them moving. Wheel studs don’t need to be tightened to high torque levels, but by using Loctite, they can be a pain to remove. I find that I can usually remove them using the double-nut method if I heat the hub first with a torch. You don’t need to get it red hot, but if you heat the area around the stud first, then block the hub from spinning, you can usually get the stud to start moving with a quick hammer blow on the wrench against the top nut. (If I had a lift and was working at shoulder height I might even get it to move just by pulling on it, but I’m working on jack-stands and sitting on the floor.) There are a couple of ways to approach the double-nut job. The right way is to thread the first nut upside down, then put a spacer washer on the stud, and thread the top nut the right way. If you plan to use these nuts on your wheels, this method will protect the cones. If you’re using nuts you plan to get rid of (like me), just thread them together. Put a little red Loctite on each stud and torque 16-20 ft lbs (using double nut method again.)

I’m using Apex Studs and they put together a little video explaining the process.

Pull a Vacuum

Use a Vacuum to Change the Oil Drain Plug without Changing the Oil

Have you ever needed to change a drain plug or a drain plug seal ring, but didn’t want to change your oil? This post shows you how by using your shop-vac to pull a vacuum on the oil fill tube which will hold the oil in your oil pan even when you remove the drain plug.

Shop Towel and VaccumYou will need a clean shop towel, folded in quarters; a shop vac hose adapter that’s slightly larger than the oil fill tube opening; and assistant  to hold it in place and operate the shop vac.  In this case, I’m working on a Porsche 996.  The 2.5 inch hose adapter fits over the fill tube and is taped to the end of the shop vac hose. It is very important that the hose adapter not move or you will lose the vacuum holding the oil in the pan.

Listen to the tone of the shop vac once the video starts.  You will hear the tone change when the drain plug is removed, but the oil will not start flowing as long as the vacuum stays on.  To change the drain plug seal ring, you just need to keep the vacuum running and you have time to remove the plug, change the ring, and put the plug back in.  Wait until it’s is hand tight before you release the vacuum.  In this video I’m actually going to dump the oil for an oil change (using Driven DT-40), but I wanted to show you how it works and that there really is oil in this engine.  Enjoy.



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Andy Hollis on Data and Suspension Tuning

Long-time readers of this blog will know that we’re huge fans of using data (especially video) to improve driving performance. A recent talk given by Andy Hollis at the SCCA Motorsports Expo reminded us that data comes in many shapes and sizes; and that it often involves zip-ties.

Andy started his presentation with the rhetorical question, “What is Data?” He asserted that data is the digital representation of a car’s performance across a set of constraints, either recorded or perceived. Your “butt-dyno” just isn’t calibrated fast enough for the rate of inputs per second of a car at speed. The advantage of data over “feel” is objectivity.

For example, do you sense that your suspension is bottoming out in a given corner? Put a zip-tie around the strut shaft where it meets the tube and see how far it moves. If it moves as far as the photo below, then it is bottoming out.

ziptie

Want to know how much body-roll you have?  Someone is always taking pictures at autocross or track events, so find a good high-resolution image of your car head-on and measure the angle? A good amount is probably in the two to four degree range.  More and you get too much weight transfer to be efficient, too little and you’re losing grip.  If the angle looks good, what is the loaded tire doing? Do you have enough negative camber?  How about air pressure?  This photos shows body-roll of about three degrees, but the loaded front tire is deforming suggesting more negative camber is needed.

Roll Angle

Data will show some surprising results, such as all other things being equal, a narrower car will be faster through a slalom (think old vs. new Miata). In Andy’s experience, tire compound is more important than width.  And testing requires a different mindset than competition.  You need to be consistent and remember your objectives when testing so you can isolate and focus on the aspect that you are testing.

For suspension tuning, he starts on the skid pad.  Time is the most important factor, not feel.  Use zip ties to see if bottoming out.  Look at tire temperatures front/rear and side to side. To get good data run in 3rd gear.  He uses a 100 foot radius skidpad.  For alignment changes, work on the end of the car that lets go first. For a front heavy car, a thicker front bar can help it push less (again counter intuitive.) Rake is important, but consider dynamic toe effect when changing rake after changing ride height. Once you have steady state on round skid pad, then go to oval skid pad and introduce the pitch variable.  If too extreme, go back to round skidpad and adjust. Next add braking/acceleration on the oval skid pad.  If the rear steps out, it could be a brake bias issue.  If you can’t adjust bias, then go back to suspension. Next he moves on to the slalom and takes acceleration of out if to just work on the transitions.  This requires a constant speed through the slalom. For autocross, a little toe out in the front can help (not recommended for the track.) For an underpowered car with over-steer a little toe out in the rear can actually help, but can also make for an interesting ride in a straight line over bumps. The B Spec cars in PWC are running as much as a half an inch toe out [which is nuts.] In the end you may have to compromise, but consider where you spend most of your time on course.  If you’re running autocross in a small parking lot with many tight turns, you may make changes that are different if most of your time is spent in long sweepers.  The same goes for the track.

Elliott Forbes Robinson on Racing

Elliott Forbes RobinsonElliott Forbes Robinson gave an interesting keynote at the SCCA Motorsport Expo last Saturday talking about what he’s learned during his 37 year career in racing. Following along with Randy Pobst’s theme of fear, he noted that if you’re feeling the adrenaline rush while driving, then you’re probably doing it wrong. It should feel awesome, yes; but not exciting. Exciting is often bad and can lead to surprises. And surprises are often bad as well: wheels falling off, fluid on the apex, no brakes, throttle stuck. It’s not that good driver’s don’t make mistakes, it’s more about how they recover. Like good actors who miss a line in a play, the observer may not notice. For a good driver that mistake could be too fast corner entry, or going off course — just without drama. But it is more a matter of style. He always tries to turn in early (something I hear attributed to Mike Skeen once too.) By turning in early, he’s able to make constant adjustments, but more importantly, he can get on the throttle at the right place, every time. He hardly ever trail-brakes and thinks of braking as the least important aspect of the corner. He tries to get all of his braking done in a straight line. As a result he consistently gets better gas mileage while maintaining competitive lap times.

2 Quart Extension Kit

Hardening Your M96 Engine

I had a nice long chat with Charles Navarro of LN Engineering at the SCCA Motorsports Expo in Charlotte, North Carolina last weekend.  He’s half of the team behind the IMS Solution for M96 engines — the other half being Jake Raby of Flat Six Innovations. I wanted to talk to Charles about preventive measures for the driver who occasionally tracks their 996.  As the Mark I 996s start to depreciate below $15K, they start to become attractive track toys, but given that a decent rebuilt motor is also $15K, nobody really wants to think of their Porsche as an engine with a disposable wrapper.

Assume for the moment that you have a 2000 996 with manual transmission and 84,000 miles on the odometer.  Your clutch and rear main seal were replaced at 67,000 miles, and engine oil analysis shows no signs of abnormal wear.  Your car doesn’t make any funny noises at start up or idle.  There’s no smoke.  You get decent gas mileage, and the car pulls very well (i.e., my car.) If you’re an engineer type, you might describe its operational condition as “nominal.” Most 996 owners seem to suffer under a state of perpetual performance anxiety, just waiting for the lump to implode.  I’ve tried to remain outside that camp, but just like wearing suspenders with a belt, it can never hurt to take extra precautions. 

So besides the IMS Bearing Retrofit which is well documented, what other preventive measures would Charles recommend?

  • Air Oil Separator (AOS): Unless you plan to track your car often, no need to replace proactively. Just check the vacuum at the crankcase. If you are going to see lots of track time, then upgrade to the Motorsports AOS.
  • Thermostat & Water Pump: If tracking often, then consider getting a lower temperature thermostat and proactively replace your water pump.  Use only genuine Porsche parts and do not use pumps with metal blades as they destroy the housing when they fail.
  • Chain Guides: Use your Durametric cable and software to look at cam timing deviation for signs of chain guide wear. Don’t replace unless the timing is off or you see excessive wear (bits of plastic) when you drop the sump cover.
  • Ticking Noises: If hot, then probably lifter.  If cold, then probably cylinder. If cylinder, then the wear may be at the bottom of the stroke and you won’t see it with a borescope coming in from the cylinder head.
  • Oil: Don’t use Mobil 1.  Use Driven DT-40.  If using other synthetic, make sure it has a high level of zinc for metal longevity.  Even if zinc looks good, watch calcium which is a measure of detergent.  High levels of calcium may clean away the beneficial zinc.
  • Oil Starvation.  Since I already have the improved oil baffle, he recommends getting the Two Quart Sump Extension. Since you’re going to replace the IMS bearing, no need to continue to use the IMS Guardian with the low hanging MCD Sensor.  Switch back to a regular magnetic drain plug.

How big of a problem is the IMS failure in 996/997 model 911s? We didn’t discuss it at the show, but most estimates range from 1% to 8% of the cars delivered, with the average for all years of this engine being 4.5% (it doesn’t effect GT2/GT3 models). Sure the failure can be catastrophic, but if you think of the IMS Bearing as just another wear item, it really isn’t that daunting.  Replacement will cost less than a clutch and should be changed again in 75,000 miles.  If you plan to keep your car forever, then go for the permanent solution (aka, the IMS Solution) which is more expensive, but only done once, otherwise, get the bearing retrofit and move on with your life.

Source: http://imsretrofit.com/wp-content/uploads/2013/11/Porsche_Class_Action_Lawsuit_Failure_Percentages_Exhibit1383012197.gif accessed 2/24/15.

Source: http://imsretrofit.com/wp-content/uploads/2013/11/Porsche_Class_Action_Lawsuit_Failure_Percentages_Exhibit1383012197.gif accessed 2/24/15.

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