Saturday, September 12, 2015

HPDE at Putnam Park Road Course (followup)

I had time today to tear into the Corvette and look at some of the issues I had last weekend.

First on the agenda was to clean up the car, it had rubber marks all over it along with rubber behind the wheel wells. I put the car up on jack stands and removed the wheels because I needed to look at the front end and brakes anyway and its easier to wash the wheel barrels when they are removed.

When I removed the tires, I noticed the buildup of rubber on them. This could have been the cause of the push, its also a lot of buildup still on them after driving the car all week putting almost 200 miles on it since the track.

There was also still a ton of brake dust inside the wheel barrels, I wash these weekly on or off the car.

Looking a bit further I found the passenger side forward sway bar bushing had migrated out of the mount making the forward sway bar ineffective causing the push. The mount bolts were torqued properly and I cannot find any history on the net of this ever happening so the only conclusion I can make is I installed it incorrectly possibly not getting it set in the groves of the subframe and bracket.

You can see the bushing still on the bar in the lower center of the picture.

As for the spongy brakes I was able to figure a lot of that out before I left the track. Apparently bleeding my brakes a month before the track day was a bad thing to do, I should have bled them the day before. I wont go into a ton of details but basically brake fluid is very hygroscopic, the water it absorbs when heated turns to steam, steam compresses and you get spongy brakes.

The problem compounds itself because the brakes are weaker you use them longer and they get hotter.

Beyond even this is the brand of brake fluid, the better fluids cost more and the advantage of them is they raise the boiling point of the fluid some by more than 100 degrees.  Nearly everyone I spoke with was running Castrol SRF making it seemingly simple to just switch to using that. The problem is Casterol SRF is $60.00 for a 1 liter bottle, meaning it would cost $120.00 to flush and fill before a track event. Some of these guys are flushing their systems once a month and at a minimum before every track day they attend. I read some positive information on another fluid, Motul RBF 600 which has a slightly lower boiling point but costs only $15.00 a bottle, I will try it first.

Lessons Learned:
Track Days are fun!

Track Days are expensive!
  • $325.00 Registration Fee
  • $220.00 Insurance
  • $050.00 Fuel (approximate)
  • $350.00 wear on brake pads and rotors (approximate)
  • $500.00 wear on tires (approximate)
Right at $1500.00 considering incidentals 

Flush the brakes and use good fluid

Take off center caps

Driving position
The entire day I felt like I was fighting the car, I generally drive with the seat fairly close but I had the seat back reclined too much. With it in a more upright position it put my arms at a more favorable angle and would have made it much less tiring.

As much as Id lke to do it again I don't know if I will due to the cost, there is probably some things I could do to cut out some of it but registration fees, fuel, wear and tear are pretty fixed. I may try some autocross, its cheaper, easier on the vehicle and less chance of wrecks and damage. 

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