[X25]

Track update

Trailer:

• Wow, I know Camaro is heavier than my MX5, but I'd hope my 2014 7000K trailer would not visibly 'flex' for a load still under its rating. Anyhow, I put it on sale over the weekend, and it sold in only 2 days! Check out how the frame bends down. It has 4"x2" channels.
  
• I finalized the details of my custom new trailer. It will be a tilt-bed 7x18.6 ft with 5"x2" channels and 10"x30" approach plates, 4" drop axles, hinged fenders, and radial tires. I'm hoping I won't need my race ramps; we'll see!

Differential:

• The night before the track day, I went out and drove the car a bit. As I was entering the gas station sideways, I put one of the rear tires up in the air, and guess what? I HAD NO TRACTION! This would happen if I had an open diff or a helical unit, but not with a clutch type. Alas, I think my differential fluid or the differential itself is toast! This might also explain why I can't improve my times anymore.
• I have three options for diff upgrade:
  • Eaton TrueTrac 912A686: I can get this differential for about $510, so it's pretty cheap. The problem with it is that Eaton asks you to use non-synthetic diff fluid. Those kinds of fluids don't last at high temps, so it's a no go for me. I asked Eaton again, and asked if I can use Redline 75W90 NS which does not have any friction modifier whatsoever. The reply was that it would work with synthetics, but would not perform optimal. I am weary about this.
  • Z/28 diff: Part # 23172755 costs $1960, and is the whole pumpkin that comes with the Torsen-type Z/28 differential. In order for it to work, though, you'd need to get the diff cooler lines, etc. You can also get the internals of the differential itself for about $1000, but considering a few hours labor the shop asks to put it into the pumpkin plus 5.5 hours of R&R, not to mention worries for labor quality, I'd rather just get the pumpkin.
  • OSGiken diff: I think this might be the best unit available for our cars. It comprises of 20+ clutches, yet is claimed to never need rebuilds, and it can provide lockup in small steps up to 100%. It also keeps working even if you raise one of the tires, unlike the Torsen unit. In such a situation, Torsen unit would have complete power loss.
• Cooler: Z/28 diff cooler kit, at around $500, is very attractive choice. If I got the Z/28 pumpkin, though, the diff lid would already be included.

Trofeo R:

• I had three track days with the Trofeo Rs, and they are now done. It was the front left tire that quit before the others. More importantly, it was the sidewalls that quit, and I actually still have thread left.
• I think there are a few reasons for this: The tire needs lower pressure to work. The recommended 28 PSI is just too high for it to have optimal traction. 26 PSI that I've tried is better, but it actually makes the soft sidewall issue worse. It is also still too high for this tire, but I did not go below that.
• Judging from uneven wear, for those who track their cars with Trofeo Rs, I highly recommend that you hit -3 camber (especially at the front). I am not sure if using at 28 PSI vs. 26 PSI would make any difference.

It actually corded as well.