Tim Duhamel (Jaguar XJ12C) and Pete Mantell (MG MGB)
BritishV8 2013 Track Day at Mid-America Motorplexas published in BritishV8 Magazine, Volume XXI Issue 1, July 2013
by: Curtis Jacobson
About Mid America Motorplex
Mid America Motorplex is a relatively new road racing facility; its road course
was completed in April 2002. Track owner Mark Tincher commissioned the track's
design to Alan Wilson, and asked him to build it with safety in mind. The result
is a 2.23 mile long racing circuit "with 15 turns of increasing radiuses, decreasing
radiuses, long straights, ample passing zones, challenging switchbacks, and a
flat-out kink". According to Mid America Motorplex's website, the 40 foot wide
polymer track surface is an uncommonly tire-friendly compound; it minimizes tire
wear while promoting traction for all types of vehicles. The track certainly has
very generous run-off areas in nearly all directions. For BritishV8's track day,
Mid America Motorplex was well staffed with corner workers. Before we took to
the track, the staff very helpfully marked suggested braking zones, corner apexs,
and they even marked corner exit "targets" with traffic cones.
Al Wulf's Buick 215 powered 1967 MGB tips the scales at just 2228#.
|OWNER||MODEL||ENGINE||LBS||(FL, FR, RL, RR, F:R, fuel load)||LBS||(FL, FR, RL, RR, F:R)|
|- WITHOUT DRIVER -||- WITH DRIVER -|
|Ryan Reis||59 Husky||Olds 2.3L||2460||(595, 594, 650, 621, 48.3:51.7, unk.)||2685||(686, 603, 742, 655, 48.0:52.0)|
|Tim Duhamel||76 XJ12C||Chevy 350||3835||(1005, 1049, 882, 898, 53.6:46.4, 3/4)|
|Al Wulf||67 MGB||Buick 215||2228||(557, 563, 554, 554, 50.3:49.7, full)|
|Carl Floyd||79 MGB||Buick 215||2239||(601, 577, 505, 556, 52.6:47.4, full)||2429||(666, 581, 583, 599, 51.3:48.7)|
|Mike Moor||78 MGB||Buick 300||2362||(596, 613, 572, 581, 51.2:48.8, 1/2)||2555||(670, 616, 646, 623, 50.3:49.7)|
|Dave Kirkman||80 MGB||Ford 302||2375||(573, 646, 606, 550, 51.3:48.7, full)|
|Kelly Stevenson||78 MGB||Ford 302||2458||(659, 678, 546, 575, 54.4:45.6, full)|
|Curtis Jacobson||71 BGT||Buick 215||2150||(521, 546, 542, 541, 49.6:50.4, full)||2341||(595, 543, 611, 592, 48.6:51.4)|
|Rick Ingram||74.5 BGT||Rover ~5L||2392||(602, 614, 590, 586, 50.8:49.2, full)|
|Terry Schulte||74 BGT||Ford 302||2596||(659, 654, 664, 619, 50.6:49.4, full)|
|B.A.D.A.S.S.||68 BGT||Buick 455||2780||(full)||2835*||(720, 720, 675, 720, 50.8:49.2)|
|Phil McConnell||74 Spitfire||Chevy 350||2624||(703, 669, 584, 668, 52.2:47.8, full)||2800||(744, 678, 670, 708, 50.8:49.2)|
|Jay Smith||63 TR4||Ford 302||2316||(587, 646, 565, 518, 53.2:46.8, full)||2509||(647, 647, 649, 566, 51.6:48.4)|
|Dale Knapke||72 TR6||Ford 2.3||2345||(full *)||2521||(592, 586, 701, 642, 46.7:53.3)|
|Calvin Grannis||74 TR6||GM 5.7L||2657||(661, 643, 660, 693, 49.1:50.9, full)|
|Ken Hiebert||72 TR6||GM 5.7L||2763||(709, 696, 655, 703, 50.9:49.1, 2/3)|
Note: B.A.D.A.S.S.'s "Roadmaster" was weighed with and without toolbox, not with and without driver.
We didn't have time to weight Phil Leonard's MG RV8 racecar at Mid-America Motorplex, but it gets weighed after every Sports Car Club of America GT2-class race it competes in. (It has competed in eight races to date!) It weighes approximately as follows: 1,583lbs empty, plus ~170 pounds of gasoline, plus ~250 pounds of driver, plus at least 150 pounds of lead ballast (strategically placed) to bring it to the SCCA-mandated minimum race weight for a GT2 RV8: 2101 pounds.
Participant Cars (photos by Graham Creswick)
Fastest overall: Calvin Grannis and his 1974 TR6 V8 (2656#)
Quickest through the corners: Carl Floyd and his 1980 MGB V8 (2240#)
Tim Duhamel and his 1976 XJ12C (3835#)
Curtis Jacobson and his 1971 MGB GT V8 (2150#)
Phil McConnell and his 1974 Spitfire (2622#)
Mike Moor and his 1978 MGB V8 (2302#)
Dale Knapke and his 1972 Triumph TR6 (2345#)
Dave Kirkman and his 1980 MGB V8 (2375#)
Steve DeGroat and his 1970 MGB GT V6
Fresh Off the Racetrack: Terry Schulte's Spectacular 1974 MGB GT V8 (2596#)
Tire Compound and Inflation Advice
What are all those numbers underneath the photos? Max Fulton volunteered to measure tires with
a durometer, an air pressure gauge, and a temperature probe. Rick Ingram helped gather data
when cars pulled off the racetrack and onto pit lane for quick measurements. Then, Max made
specific recommendations about how much air pressure track day participants should add or remove
air from their tires to improve overall traction before resuming their track day.
So, what does "LF: 75a/64a, 30.5psi/36.5psi, 134F/135F/136F. OK." mean?
When cold, the tread of the Left Front tire measured 75 with a Shore A hardness tester. After use on the racetrack, the tread softened to a measurement of 64 Shore A hardness. (Softer is stickier. All tires soften while in use, but the amount they soften is a function of their design, their suitability for a particular car, and their age. A tire that's designed for use on heavier cars, that's oversize or undersize for a given car, that's rated for for high-mileage use, or that's getting old will typically exhibit less drop in durometer reading.)
The tire started with 30.5psi of cold air, and the air pressure measured 36.5psi after use.
Three temperature measurements were made across the tread of the tire; 134°F at the outside tread block, 135°F in the middle, and 136°F at the inside tread block. That's a very even temperature distribution, so the tire's air pressure has been judged "Okay".
Participant Cars (photos by Richard Woodley)
Larry Shimp and his 1968 MGB GT V8 (2568# when weighed at BV8-2008)
chasing Dale Knapke in his TR6 and Carl Floyd in his MGB
Richard Moor and his 1969 Fiberfab Avenger (2330# when weighed at BV8-2008)
Participant Cars (photo by Artie Clark)
Doug Brown and his Mini
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Participant Cars (photos by Curtis Jacobson)
Ken Hiebert and his 1972 TR6 (2762#) - Photo taken later in the week.
Pete Mantell and his 1969 MGB V8 (2305# when weighed at BV8-2008) - Photo taken later in the week.
Phil Leonard and his 1992 MG RV8 Racecar (1851#) - Photo taken in 2012 at Heartland Park, Kansas.