The Bridgestone Era: 1991

January, 1991 SportsCar - “Fastrack News”
Racing Bulletin 91-02
The Board of Directors met in Denver, CO., on Dec. 1, 1990, and approved the following items requested by SCCA Enterprises, EFFECTIVE Jan. 1, 1991, unless otherwise noted.
1. Add item 12.i.5.C.22.j., Page 25, "A throttle return spring may be added at the foot pedal.
2. Add item 12.l.5.C.22.k., Page 25, as follows:
k. Any oil filter maybe used provided:
1. It mounts in the same location as the OEM filter.
2. The oil filter chosen shall be an OEM equivalent justified by a filter manufacturer’s application chart. The competitor is responsible for providing this documentation.
3. The capacity of the filter cannot be changed even if allowed under the above.
4. Add item 12.1.5.C.23.j., Page 26, “Tallman Kit, # 1350905, is required on all SCCA Spec Racers. EFFECTIVE April 1, 1991.”
6. Allow the addition of a steel floor pan in the area of the foot pedals/driver’s feet, dimensions to be listed in FasTrack when available.
                    

January, 1991 Spec Racer News
“Meet The Mumm Brothers” by Anon
Some of us know the Mumm brothers as the first ones to be slapped with a $500 fine for a Fram oil filter.  They decided if an oil filter was worth $500, they should go into the lube and tune business. Constrained by Spec Racer rules, they looked around the paddock in Atlanta for their first customer.  John Freeman of SRS, kindly offered them his golf cart to practice on.  After the tune up and carb service, there was still a problem. As Spec Racer ace mechanics they knew immediately the engine was down on power.  Not limited by Super Seals, this baby came apart in no time.  The cylinder was slightly worn (50 thou over).  The decision was made for a quick hone job and new rings.  They could only come up with a 10 thou over piston, which might be good enough anyway since loose bottom ends produce good power.

In record time the engine was assembled and our brothers set off for their test target... the Big Hill next to the infield.

Closely watched by about 70 spectators at turn 12, they build up their speed in the dip, estimated at 5000 RPM judged by the smoke.

With speed slowly decreasing they decided to stop three quarters of the way up the hill.  That is when they found out the parking brake did not work.  They jumped out and tried to hold the cart.  Some spectators thought they were trying to push the cart up the hill.  Did they make it?  We don’t know, because the pace car appeared and we focused on that.  Judged by the smile on John Freeman’s face the next day, driving his cart with the “Engine tuned by Mumm Brothers” sticker, they must have.
                         

April, 1991 SportsCar - “Fastrack News”
Racing Bulletin 91-04
1. Foot well pan: Material = 16 gauge mild steel, Size = 27.87 x 21.65 x 1.25 (contact SCCA Enterprises for drawing).
                         


April, 1991 Spec Racer News - “Pit Stop”
Shock absorbers have played an important role in auto racing as one of the key suspension pieces.  I still can remember my dad telling me stories of when he was racing without shocks and the technological leap when shocks were invented and found their way onto his race car.

Of course shock absorbers are really misnamed.  They don’t absorb shocks, springs do.  The role of the “shock absorber” is to dampen the energy stored in the spring as it is compressed.  When the spring is compressed, kinetic energy is stored in the spring.   When that compressive force goes away, this stored energy is released and the spring extends with great force.  The shock absorber was developed to dampen this release.  This is done by a hydraulic damper, consisting of a piston that moves in an oil filled cylinder.  By metering the fluid through suitable orifices, the kinetic energy stored in the spring can be damped, converting it from kinetic energy to thermal energy, or heat.

Shock absorbers are inherently velocity sensitive.  The faster the piston moves the more damping will result.   Fluid dynamics laws tell us that a fluid’s resistance to flow through any given orifice will increase directly as the square function of flow velocity.  To maintain suspension sensitivity at low displacements, valving is arranged so that little damping takes place at low piston velocities.  Put another way; If the suspension tries to move rapidly, the shock resists this with a high force, caused internally by the shock piston trying to ram oil through a tiny valve.  Adjustable shocks (like ours) change the size of this valve and with it the damping characteristics.

The heat generated inside a shock warms up the oil that it contains.  As the oil gets hot it thins out just like the oil in your engine.  Thin oil offers less resistance to being pushed through a small hole, so the shock loses some of its damping force.  This explains why your race car needs some track time to properly “warm-up.”

The Koni shocks that come on the Spec Racer are street shocks, not racing versions.  The special Koni aluminum bodied double adjustable externally shocks are a precision unit worth the cost and can finely alter both rebound and compression characteristics.  Our shocks on the other hand must be disassembled to adjust, time consuming and tedious, and can only affect rebound.   Really this is intended by Koni to be a wear compensating feature but racers have found it to be an important aid in fine tuning transient handling.

Since roughly 70% of the Spec cars weight hangs on the rear suspension it makes sense that the rear shocks would require stiffer settings to control the larger mass.  Incidentally both front and rear shocks are identical.  I phoned Koni about this as it seems that the front shocks should be different from the rear. Koni said that we had the correct shocks.  They agreed however that the rear shocks would need to be set firmer than the front.

Basically stiff shocks give rapid response and good transient characteristics or in other words they help the race car take it's "set" quickly.  There seems a surprising number of driver/owners who are not even aware their shocks are adjustable.

Trial and error is the only method for shock testing.  By running full soft and then trying full hard you will quickly discover neither extreme is very good. SRN came up with our shock settings by laying out a transition course with rubber pylons and then adjusting for predictable transition response.  Again those settings are: front shocks 1 1/2 turns from full hard. Rear shocks 1 turn from full hard.

To adjust this, first remove the shock from the car.  Remove the top 3/8 mounting bolt attaching the shock to the rocker arm.  In the front this is best accomplished with a box end 9/16 and a 3/8 drive with a 9/16 short socket.  In the right rear the exhaust system will interfere with a socket drive so use two 9/16 wrenches.  You may have to lift up lightly on the suspension to withdraw the 3/8 bolt.  You will notice an inner and outer tapered spacer designed to allow the spherical heim in the top of the shock to rotate freely.

To remove the bottom portion of the shock you will need a 3/4 box wrench and a 1/2 drive with a 3/4 short socket.  The bolt will stay in place, so with the nyloc nut removed slip the shock off the bolt and remove.  Also you will notice an inner and outer tapered spacer. Inspect these, particularly the inner spacer for signs of mushrooming.  This mushrooming is caused by over-tightening of the nut that causes the inner spacer to flare and essentially lock out the lower ball in the shock heim. Obviously replace this part if this condition exists.

Now that you have removed the shock from the car, place the lower mounting heim in a vise to hold the shock body steady.   Next use a spanner wrench to lower the adjustable spring collar on the threads to its lowest position.  Usually there will be a second jam collar that must be threaded down first.  On the early style shocks you can thread the collars completely off.   That is because the threaded section is slipped over the body of the shock and then welded in place.  Whereas the newer style has threads cut right into the body of the shock.

On old style shocks with the collar removed the spring will come off the bottom, though the shock must be removed from the vise for that to happen.  On the newer style shocks thread the adjustable spring collar as low as possible.  This will release tension on the spring enough so that you can remove the aluminum spring hat.  Next slide the bump rubber down and then pull down the rubber washer around the large shaft nut that secures the top heim hat.   Next remove the heim top hat; apply a large crescent wrench across the flat sides of the heim body and a 1" open end wrench on the large shaft jam nut.  With the jam nut free you should be able to spin the heim hat off the top of the shock shaft.   Sometimes the heim hat is stuck and you must use a vise-grip wrench to the shock shaft and use the large crescent on the heim hat to break it free.  Be careful to apply the vise-grip as high as possible on the shaft (right below the top threads) to avoid damaging an area of the shaft that will descend into the shock.  With the top heim hat removed, next remove the large jam nut, rubber washer, and bump rubber.

Now thread the jam nut back on and then the heim hat and temporarily snug the two.  Next push the shaft into the shock body as far as it will go. When it stops, rotate the heim hat slowly until you feel it drop slightly into a detent.  Now you are ready to adjust your shock.  Turning the heim hat clockwise tightens the shock setting.  There will be about 2 3/4 turns from soft to hard.  SRN settings are based on turning the shock full hard and then backing off a prescribed amount

Reverse the disassembly process and reinstall, taking care not to over tighten the fasteners.  Figure on about a half hour per shock.  Take your time, clean the shock while you have it out, inspect everything for signs of damage or wear and lubricate the heims.  Usually shocks fail because the seals go bad or the shaft is bent.  Rotate the shaft to check for straightness and look for signs of leaking shock oil past the seals where the shaft extends from the shock body.  Also inspect the heims for cracks or excessive looseness.  The heim is replaceable in each end of the shock.
                            

August, 1991 SportsCar - “Court of the Appeals”
Judgement of the Court of Appeals
Clay Sylvester vs. SOM
MAY 29, 1991
PRIOR PROCEEDINGS AND FACTS IN BRIEF
On May 12, 1991, at the Daytona International Speedway National race, Clay Sylvester’s Spec Racer was found at post-race impound to be in violation of Spec Racer Rule C.6.a.2.C.  The violation consisted of an aluminum shield fastened to the top of the exhaust manifold between the manifold and the carburetor.  The Chief Scrutineer, Bernie McHenry reported this to the Chief Steward, Harro Zitza.  Mr. Zitza excluded Mr Sylvester from the event.  Mr. Sylvester filed a protest against the Chief Steward's action.

The Stewards of the Meet, George Hall, Jim Stark, Ron Rawls, Steve Tye, and Bob Clark, chairman, held a hearing and upheld the Chief Steward’s exclusion.  Mr. Sylvester filed an appeal.

FINDINGS OF THE COURT
The reason for a heat shield is to prevent vapor lock, which is a problem caused by temperature and humidity in certain areas.  Spec Racer Rule C.6.a.2.C., states: build and install a metal heat shield between the head and the fuel pump.  Mr. Sylvester’s heat shield was built and installed by the Southwest Division CSR, Glen Graham on May 11,1991, to solve a vapor lock problem.  The Stewards of the Meet ruled that once a heat shield extends beyond the fuel pump toward the rear or the side of the car it is illegal and that the presence of a heat shield between the exhaust manifold and the carburetor may provide a measurable performance advantage.

The Stewards of the Meet did state that it would be helpful to competitors and to CSRs if SCCA Enterprises and the Competition Board would provide definite size limits and guidelines for this heat shield.  As there are now no size limitations for the heat shield in the current Spec Racer Rules, the Court cannot hold Mr. Sylvester’s Spec Racer heat shield to some non-existent dimensions.

The Court does request that SCCA Enterprises and the Competition Board review the rule on heat shields and be specific about what is allowed so that race officials will have appropriate dimensions, etc., on which to rule.

RULINGS OF THE COURT
The Court overturns Mr. Sylvester’s exclusion and restores his finishing position in the May 12,1991, race.  Mr. Sylvester’s appeal is well-founded and his appeal fee, less $25 retained by SCCA, will be returned to him.

Editor’s Note:  Clay won this race!
                             

Miscellany from 1991
Dave Downey wins the Runoffs
Jeff Beck wins CenDiv with 69 points
Warren Stillwell finishes 1st in NEDiv with 66 points
Robert Mumm finishes 6th in CenDiv with 45 points.  We qualify 12th at the Runoffs and finish 9th.
Clay Sylvester finishes 4th at the Runoffs
SCCA Enterprises sells 13 car kits
Total Cars Sold to Date: 597

Barry