Have a seat my
friends as you hear the story of the 20 cent washer. Well, two of these
washers actually, but at this low price what difference does it really make?
Well, quite a bit as let me tell you what these two washers have to do with
rear wheel wobble and cutting my track time in half on Saturday. Those of you who read my SCCA Lime Rock event
in mid June, you recall how during qualification there was a driver
error and this caused the right rear upper suspension bit needing to be
replaced. The race last month went well and all seemed fine.
Arriving
at NHIS on Friday, the day before the two races, i began doing the usual bolt
check while also changing the car's rear wing setup for high downforce.
Everything checked out and was ready for qualification using NHIS' roval
course. The car felt good, if a bit understeering, during the first few warm
up laps. Around lap 7 was taking the lefthander (T3) and the rear of the car
stepped out and wobbled. It felt much like the rear left tire going flat and
so nursed the car into the pits. Naturally the first thing i did was check
the rear left and the tire had pressure. Hmmm, interesting as there
is a problem. A few moments later i noticed the two bolts that hold the top
suspension bit, which was replaced at Lime Rock Park, seemed as though they had backed out
considerable. Then
realizing the shims that control camber, which these bolts secure down, were
completely missing! This meant the missing shims, about 3/8th an inch worth, allowed the
upper wheel connection to move that amount. This is some serious movement
when one factors in the movement possibility at the top of the rear wheel!
Qualified fourth with a best lap time of 1:08.155.
What the ???
Scratching my head as was sure the bolt check
was thorough, i chalked it up to perhaps missing those bolts. Fortunately
had plenty of spare shims, about 6 needed for correct alignment, and so
commenced to realigning the car and tightened the corresponding bolts. Of
course these bolts did have a washer or two at their head so all looked fine. With
everything set and the bolts tight, and using some Loctite Blue for good
measure, it was time for the race.
During
the race the car started off with a touch of understeer, yet by lap 6 was
really neutral and was feeling great. Rifled off a few more laps and the car
was coming on strong. And as some of you readers guessed, that is
when things went a bit haywire on lap 10. Coming down the hill (T9) and taking the
right the car had the same weird wobble as during qualification and so immediately
pulled her into the pits. Game over, damn! Checking the rear left was astonished all my shims
were once again gone! What the...!
Color me perplexed as this was just fixed! Of
course i verified the rear left wheel assembly was tight. So that night i
took that section of the car completely apart to analyze what was going on,
as the bolts were indeed tight. Basically, the
part of the rear wheel where the upper suspension bolts attach, and shims
insert between, has the usual screw front and an opened rear. One would
assume a long bolt would simply screw in and, if too long, would continue
through the part and exit out the rear hole/opening.
Upon additional studying of the part in
question (seen right), it appears the bolt screws in yet hits an end point and will not
go though the rear opening. My study concluded that the bolts were indeed
tight, though perhaps a very small bit too long. Perhaps when reassembly during the Lime Rock Park event one additional
washer per bolt were necessary. You see, there was probably a looseness of
only a few thousandths of a inch, as the bolts were tight against the end
stop and not the actual suspension/shims/wheel upright assembly. This
extremely small looseness while being undetected with the usual checks and
balances, caused a shim to fall out while driving and then
caused the other shims to subsequently fall out.
So even though i verified the tightness of
the assembly and bolts while fixing it after qualification, this ever so
slight and obviously undetected spacing was easily solved by using a single
additional washer on each of the two bolt heads. The space taken up by the washers now meant
the bolts were truly tight within the wheel assembly and not hitting the end
stop. As for why there is a stop versus the bolt going all the way through
the rear opening, my guess is that this part is so close to the brake rotor
the design was to ensure the bolts did not go through to a point where it
would make contact with the rotor.
And so that is my Saturday story of how a
pair of 20 cent washers cost me two complete set of rear shims plus track
time during qualification and cutting short the possibility of completely
finishing the race. Fortunately the car did hold together past the half-way
mark so did get credit for the race. Also, fast hands and quick thinking
meant the car did not get balled up into the wall and, instead, was able to
bring her back in to the pits to make the proper correction. We dare not
think of what could have happened if the tremendous rear left wheel movement
happened at certain moment and the car spun in a fashion that would have been
catastrophic.
My thanks goes out to Rob Laverty for lending
me a set of rear shims at the track, as i ran out of spares.
Best lap was 1:09.575 and was the first to
retire from the race.
Sunday, July 15th Event
With
the car now fixed, or had darn well better be, it was time for
qualification. Today the race was not in the roval, but in the chicane-chicane
configuration. This is the way i have driven this track quite a bit so was
familiar with what was needed as many others have rarely, if ever, driven NHIS
in this setting. Used the first few laps to get the car and tires warm while
being sure the rear left was fine. It was a hot and very humid morning
plus felt confident in the car so on lap 9 did a 1:14.244. Then i took a slight
break for a few laps to make my last run at the end. This allowed more gas
to burn off in the meantime and on the very last lap of qualification earned
a third place qualification finish of 1:13.749. Perhaps all those years of
watching Formula 1 combined with a small handful of SCCA events has taught me to make my best efforts with good spacing in front of me and when
the car is at her lightest. Goodness knows i have made enough freshman
errors already.
To Rain Or Not Rain....
That
is the question. The on-again off-again rain showers continued through the
afternoon. An hour before the race the rain was coming down in buckets, only
to let off and eventually turned into a light sprinkle. With only 15
minutes until grid the sky was spotty yet still overcast a bit. Many
of us were on dry tires hoping for slow to no rain as it did let up from
time to time. Then the rain began coming down harder and so the mad dash to
change to wet setup commenced! The gentleman in the pits next to me had his
car on 1/2 wet and 1/2 dry so he only needed to change two of the four
tires. Smart man! With a brand new set of Hoosier wets on the car it was time to roll
out to the grid. Rob commented that, as Glenn at GTP suggested, a set
of hand grooved Hoosier 25 as intermediate tires would have been perfect for
these condition and be careful not the fry these full wet tires so seek out
damp bits of tarmac if the track dries up.
The rain slowed up and we got two laps
behind the pace car so as to get familiar with the now wet surface. i noted
the transition from 2b to the NASCAR straight was very slippery. My new
Hoosiers were not scrubbed in, and so they felt a bit 'pointy' and not quite
flatfooted. Perhaps i had too much pressure in them, though did set them according
to what was recommended. Under the second pace lap i saw the other Formula
Continental driver pull off, later finding out he had an issue that caused an
electrical short or some such with the smell of burning plastic filling his cabin. The
other Formula Continental driver was out due to yesterday's event. So being
the sole survivor in my classification and having never ran the car in the
wet, felt it was best to take this track time more for a test session than
as a pure race. No need to pitch the car to the very edge, and perhaps off
the track and causing damage. Was also warned that this light rain condition could cause the full wets to overheat and ruin them. At these
prices there was no need to cook a brand new set of tires, but being inexperienced
i had no idea the feeling of using versus cooking.
And so came probably the slowest laps in the
car as at the beginning the tires felt pointy, yet after 5 laps things
started to come along and feel better. Sure i could have driven faster, yet
in the back of my mind was frying a new set of wets or tossing the car off
the track. The car was great on the straight parts yet during turns was a
bit more challenging. My budget is limited and already needed a few new bits due to
other circumstances at previous races. And so while finishing first by
default, it was not necessarily the best drive of my life. After the race i
looked at the tires and realized they could have easily handled the
conditions and harder driving without fear of frying them. Darn! Well, at
least there was now some wet weather experience under my belt and data
recorded for future use.
Appreciation And Thanks
Rob Laverty deserves a huge thanks for
lending me his rear shims and providing some excellent tips and hints. Rob's
friends get a huge thumbs up for buckling me in and whatnot during the event. And of course my
wife for putting up with my weekends away at the track. As always, in the
end what really matters is that we all...
Enjoy the Track,
Steven R. Rochlin
