TWO REAR TIRES
The car has two rear tires so why not use them both?
Couple of weeks ago at Irwindale, second time trail after I
relocated the 4 link bars, I added some right rear tire preload and
the tires slipped a bit - so I took out the preload and the tires
hooked. I concluded that it did not like that and did not try it
again.
Several Tim Dolan videos since then show the car moving right on
launch and then back left after 30 ft or so. This indicates too much
left tire weight but the evidence was against change.
The wear pattern on my new tires showed the edges were not doing any
work. I experimented with tire pressures and found they worked best
at 10 lbs. Well - one of them did anyhow.
Irwindale's track prep is sketchy. They have a golf cart with VHT
they use before the first race. After that it’s a hand cart with a
garden sprayer and a mop. And sometimes its not even VHT. Some fast
talker sold them some "comparable" sauce and it was crap. Add to
that the fact that the lines men leave you in the water a lot, and
all the dweebs that drag half the water in the box up to the line
and what the hell was I thinking when I made a suspension tuning
decision based on one run at Irwindale anyhow. Sheesh.
Thursday's race, Tim looked at my right rear tire and asked "how
come your tires aren't sticky". His drag radials come back sticky
after a race. That got me thinking - and looking and comparing the
tires a lot closer every run.
Fontana's track prep is excellent. They have all the stuff you see
on TV - the big tractor with rotating brush, the dragger with the
half dozen big tanks of VHT. Every two hours or so they break it out
and do the track.
Saturday I hooked on my first run and ran 11.93. Not the 11.80 I was
hoping for but happy to get my 11 second ticket.
The tires were talking now. I could clearly see the left tire was
rough and sticky edge to edge and the right was slightly rough in
the middle and not sticky at all.
I dialed in a 1/4 turn top right bar preload and went a tenth
quicker the very next lap with diminishing air.
A tenth! A whole stinking tenth! Apparently two tires work better.
The tires were looking almost the same after that run. I dialed in
another 1/4 turn and went a little slower - but it was getting hot.
The right tire was looking more like the left now so I stopped
there. It was time for eliminations.
I lost in round three at the line. My 081 was bested by a 048 light
and a good consistent car. My previous RT was a scary 007 and I over
compensated.
Good day for me all around though.
The data graph PDF for the 11.93 run is -->
HERE. The
raggedy 2nd gear crap is still very apparent. I playback each run on
my tach, to note the actual shift points, and noticed the raggedy
RPMs every run.
I'm hoping it's the soft tires wobbling. On the way home, with 20
lbs in the tires, I downshifted to second on the freeway and ran it
up to 5800 RPM twice. Bad citizen. Both times the needle was rock
steady.
Final tire evaluation at the track I saw that the edges were taking
a beating indicating too soft. Thursday I'll go back to 14 lbs and
see what happens.
These changes mess up my Air Gap evaluation. I'm thinking I should
go quicker if I move my shift points down a couple of huns.
Sunday is Summit Series. I'll run the vacuum carb on Thursday to get
a new baseline to compare to the BG bubble dumper two weeks after.
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