Thursday, March 29, 2012

Yes We Camber!

Now that I have a fresh new U-joint in the steering and the winter gas is all burned off, it's time to get ready for racing. This year I intend to work hard to ensure that the camber and toe are properly set, the car is corner balanced, and I hope to work out the best settings for my shocks, sway bar and tire pressures in light of the new setup.

That's about a six variable optimization (if you don't count weather & temperature), which is kind of daunting. Where does one start?

While I was doing the work on the steering, I noticed that my right side had a lot fewer camber plates than the left, so I had a strong suspicion that my side to side camber was not correct. Therefore, since this appears likely to be out of whack and since the settings are available on Lotus-Talk, I'll start there.

Over the winter, I bought a SmartCamber tool, but before I can use it I need to get the car on a level surface and equipped as if it were racing. We want to optimize for racing so the setup will be slightly off for road use, but road driving isn't a competition (despite what the folks in the urban assault vehicles seem to think).

I put on the race tires, removed the tow bar and put 150lbs of books and break rotors in the driver's seat to simulate the driver (which is around 7% of the weight of the car!). To level the car, I shimmed the wheels with linoleum tiles (available for 69 cents each in Home Depot). I measured how many each wheel needed with a 78" long level resting on a couple of sockets and the SmartCamber tool, which is really just a fancy level. After marking the point I measured the tiles, rolled the car to that point and jacked it up. After jacking the car up, and placing the tiles under the wheels I also inserted a plastic bag folded over with some motor oil between the folds. This allows the tires to slip sideways when the car comes back down and avoids the need to roll the car back and forth.

The camber measured -1.1 on the right side and -0.1 on the left side. That's a whole degree of difference, which may go a long way to explaining why my car tended to ABS earlier than it should in threshold breaking. Also, thinking back I can't remember any spins that were clockwise. I hadn't thought about it before, but I suspect that the setup I had settled on in terms of shocks/tire pressures and sway bar settings last year was flawed. Possibly, the right side of the car was slightly tail happy, but neutral on the left, which would be consistent with a better camber setting on the right that gave the front right more traction in a left turn than the front left had in a right turn.

The rear was better, -2.0 on the right, and -1.7 on the left. The latter is stock and the former is just a little bit less than the recommended setting for autocross which is -2.25.

I took out all three shims on the front left, one on the right rear and two out of the left rear. The result was -1.0/-1.1 in the front and -2.1 -2.3 in the rear. This is now within the .2 side to side tolerance recommended by Lotus (just barely for the rear). Many serious racers seek even more negative camber in the front, but to achieve more one needs to replace or mill the steering arms.

Anway, Next up... Measuring the Toe. Here are some pictures of my setup...

Friday, March 23, 2012

Back on the Road

All put back together, and burning off the winter Gas...

Next mission, check and set the camber & toe on all 4 wheels...

Friday, March 9, 2012

U-Joint Install

In a previous post I promised to describe the lower U-Joint install. This was before I understood the depth of this undertaking. I am now in the middle of it (and an additional repair I found along the way). It turns out to be necessary to unbolt the entire steering column and shift it by an inch or two. I don't want to give folks advice on working in the vicinity of the airbag system, so I will only list some general guidelines as to what is entailed, and not a step by step process. The idea here is to help you understand whether or not this project exceeds your mechanical ability or available time frame, not to provide a guide. Things you must do include:

  • Removal of the bolts for the u-joint shaft where it attaches to the steering rack, and the upper U Joint. This will be very difficult if you are overweight, or taller than 6 ft. If getting into the car is difficult for you, this may be physically impossible.
  • Removal of steering column shrouding, and the binnacle over the instrument cluster.
  • Removal of the instrument cluster, and switch pack
  • Unbolting of the steering column.
Please consult the lotus manuals, or other resources for details and safety precautions. I STRONGLY suggest you read section WD of the service manual on airbag safety. I have purchased a copy myself. Working on any part of the vehicle containing pyrotechnic safety devices (i.e. airbags, and seatbelt pretensioners) without the service manual is very dangerous. Note that in the Elise BOTH airbags will deploy and the seatbelt pre-tensioners will also fire if the system is fooled into thinking a crash has occurred. Static electricity can also set off airbags, so proper disablement is important.

Things you don't have to do that I did:
  • Loosen the steering rack - I thought I might be able to avoid moving the steering column this way, but it is insufficient to allow removal of the U-Joint.
  • Take apart the whole dash board. I did this following a thread on Lotus Talk (see links page), but when I got a copy of the manual, it became clear that the dash could be left in place. However, dash removal is not that hard, and it makes getting to the back bolt of the steering column a piece of cake. 
  • Remove the Steering wheel from the steering column, although it's not hard and makes access into the dash to remove the rear steering column bolt much easier. This requires airbag removal however, so I repeat... 
Please READ section WD of the manual before working on the dash or steering column! Airbag Detonation can cause serious injury or death. Also note, that for dash removal you have to break 4 clips on the passenger airbag cover, and that you must buy new ones to replace them. They were only about $10 for all 4 (plus shipping), but you cannot re-assemble the dash without them.