Wednesday, April 25, 2012

More on wheel vibrations

Wheel balancing issues can lead to pesky, unwanted vibrations and can also rob you of your track time by having you running back and forth to the tire guys. A simple way to keep your wheel weights where they should be is Duct Tape. Use a good quality Duct Tape to double secure the weights to your wheels, as shown in the photo below

Wednesday, April 18, 2012

Buttonwillow Results + Prep, Tuning & Coaching

We had great results at the second Lotus Cup race weekend at Buttonwillow. We managed to secure two Open class victories and one overall win.  We also secured the fastest lap all weekend again - beating the entire field including the 211s that we're attempting to compete against.  Our driver Glen is doing a superb job along with the team in prepping the Art Car.  We also had help from our friend and driving coach Dave Thilenius.  

The weekend did not run 'issue-free'.  We suffered from an electrical cut that killed the car on the first day during practice.  Patrick managed to figure out that one of the wires in our ignition was loose and secured it.  We have kept the stock key and start button on our car.  Glen's knees are quite close to these wires and he believed his knees were brushing the wires causing the cut out.  Unfortunately for us, the problem cropped back up on the second race - while we were in the lead, on the last lap!   Luckily Glen had a clear enough mind to wiggle the wires under the steering column and get the car started.  He managed to get in behind Andy and secure the Open Class victory and second place overall.  Eliminating this wire is now high on our list of reliability improvements.

AiM Data Coaching
We're big advocates of using data to lower lap times.  We also use it as an R&D tool as we develop our products.  At Buttonwillow we were graced with Dave T's presence and benefitted from his extensive expertise with coaching via data.  Reviewing the data allowed Glen to adjust his shifts, braking points and more in order to achieve the fastest lap of the weekend.  Our friend Andy has used data to secure LCU championships with his 211 and is one of the fastest drivers in our series.  We have a new AiM product that makes getting into data much more affordable and practical for track day enthusiast and racers alike.  See the new Solo DL.

The guys were taking tire temps and pressures and adjusting pressures and camber.  Amazingly we are running less than -2deg of Camber with this kit and getting even tire temps.  Typically these Yokos require -3deg.  We also softened the High Speed Compression to improve our grip over the curbs.  In doing so, we stiffen the Low Speed Compression as well to quicken the turn-in.  Buttonwillow is a much bumpier track than Chuckwalla so a softer set-up is ideal.  Our new raceUPRIGHTs are running beautifully and allowing for an amazing low ride height.  We kept our ride height at 103mm/110mm to insure we did not bottom out.  These ride heights can not be achieved in an Elise or Exige with stock uprights.  We are now conducting our Set Down process to see how the raceUPRIGHTs are fairing.  I peeked at them and they remain in great shape after 5 track days.  Expect another Blog posting reviewing the condition in more detail.
Car Prep
A key tool that we use to prep and insure our car is running well are simple Checklists.  We use these lists to confirm that we checked critical areas on the car before it leaves for a practice session, qualifying or race.  Every time - not just at the beginning of the day.  It takes a bunch of time to run through these checklists but we've found it is a key way to ensure our car runs as well as it can.  Since we are running with the LCU leaders, we can't afford to make mistakes with the car prep.  If any of you would like copies of our Checklists, let us know.  They are an effective tool for the casual track day enthusiast to the hardcore racer.

What's Next?
We can't be happier with our results so far this season.  We have some work to do before the next race - including a Lexan Optic Armor windshield that should shave another 16lbs from our Art Car.    Infineon is the next race in mid May and we will be competing against a bunch of NorCal locals who know the track well.  We'll need to bring our 'A' game to keep our track record as it will be very competitive!

 Now watch Glen turn the record lap...

Tuesday, April 10, 2012

Determining Wheel & Tire Vibration

A common problem faced by owners of light cars with light wheels is high speed vibrations.  We faced a serious vibration problem at the last Lotus Cup race and wanted to determine the source.  Typically the following areas can be the cause:
  1. Wheels
  2. Tires
  3. Balancing
  4. Suspension
After returning from the races, we conducted a comprehensive set-down on our car.  We scrutinized the suspension components to see if any parts had come loose.  We were testing our new raceUPRIGHTS and new Delrin Bushes so we checked everything closely.  Nothing was loose or found to contribute to the vibration problem.  We then turned our attention to the ETHOS wheels that we had used.

We decided to send the wheels that we ran and were suspect to our supplier, Tom Merrifield, for measurement.  I called Tom to discuss the issue and he was open to conducting a Run-out test on the wheels.  Poor run-out in wheels could be from either poor manufacturing quality or track/road damage.  We decided to measure these wheels to see if they were out of spec.

Tom made a nice video showing the test method. See below:

He found that the wheels had less than .004" of run-out.  According to Tom, vibrations can not be felt under .015" of run-out.  We are well under this amount.

This leaves the Tires or Balancing.  Since the tires are from Yokohama, the quality is generally very high.  I spoke with the tire supplier and he was also confident that the tires were OK.  We've run them many times with good success.  Of course since we did not test them, we're not 100% confident.  In our mind, this left Balancing as the most likely source.

We arrived at the event with a set of scrubbed-in tires that we had locally mounted and balanced on a set of ETHOS.  They performed with no problems and Glen set the Fastest Lap of the Weekend.  We bought a new set of tires, at the track, and had them mounted and balanced to a new set of ETHOS. These vibrated badly around 70mph.

Balancing done at the track is usually difficult because of time constraints. There is usually a line of racers waiting for their turn, so the poor guy balancing never really gets enough time.  This was the case at this first race.  The tire supplier graciously offered free mounting and balancing so had their hands full!

Our local wheel balancer, Frank, advised that plenty of lubrication is needed for these tires and that proper time needs to be taken along with careful balancing to get these light wheels and tires sorted correctly.  He also agreed with the run-out spec that Tom follows.  We're attending this weekend's race with new tires and old ones that Frank balanced to the same two sets of ETHOS wheels that we ran last time.  Running the old tires (that vibrated), balanced by Frank, will determine if the track balancing was the problem.

What's the moral of the story? Get an extra set of wheels and use a local tire balancer who will take the time to install and balance your race tires before you leave for your track event.  Follow this rule and you won't likely have the same headache that we faced.