Saturday, January 28, 2012

Flipping Tires - Things you should know

In the weeks after the race at Infineon, I spoke with other racers about my experience with my tires lack of grip.  Lots of speculation.  Most people thought it was b/c I had so many heat cycles on them.  It was an obvious conclusion - but it was not correct.  Testing the tread with a durometer showed that the tires were actually still nice and soft and not hardened from heat cycles.

I kept on exploring and finally figured it out.

At the last race, I had decided to "flip" the tires to even out wear patterns.  Flipping the tires refers to dismounting them and remounting them so that the inside tread is now on the outside.  This enables you to get a little more life out of the tire and saves money.

Turns out when you "flip" a tire, you need to put at least one session on them.  Otherwise the tires do not grip.  Major lesson learned....

In retrospect, I'm not sure if this actually saved me any money.  It cost me a few $ to flip the tires and the car didn't have any grip, ruining a race weekend.

When "Flipping Tires", plan on doing a session or two on them so that the tread grips again.

Racing at a new track - SCCA @ Infineon

So the next race was Infineon Raceway in Sonoma, CA.  I have only been to this track once before in my street car (RX7).  Infineon is known as a technical track.  It is more challenging and difficult to learn than Laguna Seca or Thunderhill.  There are many and frequent elevation changes.  Most corners are blind (meaning you can't see the apex or exit).  It doesn't even really have a straight.  This track keeps you busy working the car the whole time.

The scariest thing about this track is that it doesn't have any run-off.  If you go off, you are probably going to hit something.  I had just finished fixing my car and was not looking forward to breaking anything else...

How to prep for a new track
I wish I could give you pointers on how to do this but I don't know if I have much to go on.

In preparation for this race at a track that I wasn't familiar with, I watched many Spec Miata videos on YouTube and Vimeo to try and understand braking points, turn in points and see if I could learn this line.  Viewing the videos, made me feel comfortable.  However, once I got out on track, what I had seen in the videos just didn't translate well to what I did on track.

With the large elevation changes at this track and blind apexes, the videos just didn't seem to help me all that much.  I felt totally lost out there.  Next time, I'm going to try and do a test day before attempting to race a track that I've never been to before.

Let's talk tires for a bit.  

This race was at the mid-point of the season and I was still running the original 6/32 shaved Toyo RA1 tires that I had bought at the beginning of the season.  They were wearing surprisingly well.  The outside edges were showing a bit more wear than the inside of the tires.  Some people "flip" tires to get more life out of them.  This involves dismounting the tire and remounting with the inside "flipped" so that it now on the outside.  Being the frugal person that I am, I decided to do this.  I had AIM Tire flip the tires Sat morning of the race weekend.

Racing at a new track
So, new track, learning the lines, trying to re-build confidence after my last race where I damaged my car.  Lots of challenges.  I just could not get comfortable.  I tried following people during practice but my tires didn't seem to have any grip.  What could be wrong?  The tires felt awesome last race.  Could I have used them up suddenly due to all the heat cycles?  The tires still had about 2/32nds of tread.  Was it just the driver's self confidence?  Very un-nerving at a track as challenging as Infineon....  My qualifying times had me last.

The race finally came and I approached feeling very uncomfortable.  The car didn't have any grip and I couldn't keep up.  Pretty soon, I was getting lapped.  Approaching the Esses, I noticed a string of front runners coming up fast.  There isn't enough room for a 5 car train to pass in the Esses.  What should I do?  If I held my line, I was afraid I'd get taken out so I slowed up and pulled off line so the train could get through. Then I drove into the hot pits and called it a day.  I'd rather have the car in one piece so I can figure out what was wrong and save it for the next race.

How to Diagnose a Bent Ball Joint

If you ever need to diagnose if you have a bent ball joint, here is a video tutorial. Hope it helps.

Assessing and Fixing the Damaged Front End

If you read my last post, you'll learn that I wrecked the front end of the car in a bad spin at the last SCCA race at Thunderhill in July 2011.

Damage Assessment

I got the car home and got the front up on jackstands and started to assess damage.  Here is what I found.

1. Upper control arm bent:

2. Lower Control Arm very slightly bent (forgot to get picture).  I probably could have re-used it but it would have affected how much camber could be adjusted.

3. Front Subframe bent badly.  Here are a few pics illustrating the damage:
- Subframe Lower Control Arm rear mounting tab bent:

- Subframe Lower Control Arm front mounting tab bent:
4. Front wheel bent:

I had already changed the front subframe once before while building the car b/c the driver side mounting tabs for the steering rack had been bent at one point in the car's life.  It isn't that difficult to do but is a bit time consuming and not fun.  I decided to tackle the repair myself so I started sourcing parts.  "Where to source these parts?" you might be thinking.  The answer is craigslist. :-)

Most of the used parts sourced for this car came from craigslist.  So I turned there again.  It seems like there is always somebody local parting out a Miata on Craigslist.  Since the parts are local, shipping costs are eliminated.  

I decided to upgrade the front subframe to the one from the 94-97 Miatas.  These cars came equipped with more bracing from the factory on the front and rear subframes.  You technically could add these braces to the original subframe of the 90-93 cars but that would require more work on my part.  When I started looking for parts, I discovered that a fellow racer had the parts I needed.  He cut me an awesome deal at $100 for the front subframe, spindle and lower control arm.  I didn't need the upper since I had a spare.  I sourced  a new wheel from our local race tire supplier and series sponsor - AIM Tire.

So I picked up the parts and started wrenching to get the car ready for the next race.  I replaced the subframe and control arms.  I didn't replace the spindle at this time because a I couldn't get the ball joint separated so I left it alone since I had replaced the ball joint when I built the car.

Here is a comparison of a bent subframe the straight, un-bent replacement.  The bent subframe is on top.  The replacement is on the bottom.  The control arm mounting tabs were bent a good 1/4".

If you never replaced a front subframe on a Miata, it isn't particularly difficult.  It took me the better part of a day to do it 4-6 hours.  If you want specifics, please contact me and I can prepare a write-up with pics.

Do you think I got it right?  Sadly, no....

Once the car was back together, I brought it over to TFB Performance to get the car corner balanced and aligned.  Here is where we discovered that I had not replaced ALL of the bent parts.  We couldn't get more than -1.5* of camber on the passenger front.  Turns out the spindle and the ball joint were also bent.  I never even knew those parts could bend....  Thankfully, TFB does a lot of Miatas and had the parts in stock.  He installed a new ball joint and a used spindle.  I spent about $700 in total on this repair.  Expensive mistake but it could have been worse.

If you are curious about how to diagnose a bent ball joint.  Here is a video I took repeating the diagnostic procedure that TFB had done in the shop.  Basically, put a socket on the ball joint, put pressure so that the ball joint is pushed downward or outward so that it is against the outer edge that it sits in, then turn the wrench as if you were tightening the nut.  Hopefully the video makes sense of this:

Frustrating repair but it got done.  When's the next race?

SCCA Spec Miata Race - July @ Thunderhill = Spin and wreck...

This was a frustrating race. Blogging about it made it more frustrating. Hence the radio silence on the blog.

I was having a great weekend. The car felt great. The tires were performing well and I was getting a lot out of them. Pressures were 38 PSI checked after hot practice and qualifying which is perfect. My lap times improved a lot. I was finally doing 2:16s at Thunderhill which ain't bad for a rookie. Then the race started....

Check out the race on YouTube here:

I was chasing fellow rookie Cliff in the white car with the burgundy stripe. I was pushing hard and making him work for his position. Problem was that the tires were starting to lose grip. My mind was telling me that I had to slow it up a bit and let the tires cool off a bit and come back to me. The "Red Mist" was telling me to push harder. Just one more turn. So I kept pushing. And then.... I had no grip at T5... Oops.

I crested the hill and the car was already sliding and eventually looped around. The passenger side front wheel hit the adjoining road surface sideways and damaged the front end of the car. I could have rolled it if the rear wheel had also made contact there but thankfully that didn't happen. I wound up sitting in that spot and waiting for the race to finish so I could get the car back into the pits.

Thankfully I was able to load the car onto the trailer so I could get it home and figure out what I was going to do and how I was going to get this fixed.

This sucked.

 Lessons learned = Beware the Red Mist. Believe what your tires are telling you. Loss of control can be expensive.