That's a question that I get asked a lot and I have a definitive answer...........sometimes........ 
OK.......so here's what I mean.
- Some chassis designs such as the "no brainer" that I talk about, work well on most any surface with any tire.
- Some however, need something a little more specific.
- The test outlined below illustrates this difference pretty well.
Here are two new chassis that continue to explore my recent theme of brass/wire rail combos.
Both chassis are 4" wb X .925 guide lead.
Both use R-Geo .050 angled face brackets.
Both used a std. JK chassis kit as a starter.
Both used the same RH motor for the test geared 9-28
Both used the same Parma Lola T-163 body
Left is 3 rails/side. 2/ .062 brass, 1/.062 wire. Pans are shaker style. All up = 105 gr.
Right is 2 rails/side. 1/.062 brass, 1/.062 wire. This is a torsion car. All up = 100 gr.
The cars were tested on this track. (I post the picture b/c this is a a rather unusual track design) My usual tire for this track with most cars is the JK 8713 PP. On a day with good conditions, a good time for a Can Am on this track is ~~ 4.80-4.90. Today, conditions were pretty good.
Cars were tested 10-12 laps at 98% of max. I would glance at the timer each lap and note highs and lows. I would disregard any hair laps and the results are the average of the 3 best (non-hair) laps. Because I was not trying to set lap records with each test, I seldom came off and really didn't have many hair laps.
3 rail shaker car (left)
JK 8703 PP = 4.82
JK 8713 PP = 4.84
JK 8763 PP = 4.87
JK 8703 PT = 4.86
JK 8713 PT = 4.83
JK 8763 PT = 4.92 a touch loose
Kelly Retro = 4.94 a touch looser
JK 8713 PT = 4.81 Retested to verify and also to test a different body (O/S 410-L)
Conclusion: This is a very good race car for this track and can use just about any tire (approaching no brainer status)
Torsion Car (preface....I have built similar torsion cars over the last couple years without much success)
JK 8703 PP = 5.09 (Would snap out on exit in fallaway LH 180 in foreground and RH sweeper in background)
JK 8713 PP = 5.06 (Felt similar although clock said it was better)
JK 8763 PP = 5.02 (Starts to feel more predictable)
JK 8703 PT = 4.94 (Beginning to feel racy)
JK 8713 PT = 4.88 (Feeling like I could push the car pretty hard now)
JK 8763 PT = 4.98 (OK but starting to feel loose)
Kelly Retro = 5.12 (Loose and unpredictable)
Conclusion: At first, this car felt poor but with some tire tuning it got into the ball park for this track. Some selective narrowing might have been beneficial for this car. This chassis is possibly not ideal for the subtle direction changes on this track. I think it will prove to be better on tracks with more conventional turn configurations. This is consistent with most of the other torsion cars I've built.
So.......yes. Sometimes, different chassis designs on the same track will have very different reactions with different tires while other chassis designs may work with almost anything.
