New minimum weight for 2012

In the Prepared classes, each car and class have mimimum weight requirements.  Most of the classes use similar formulas, but they can vary.  In DP, the minimum wieghts are based primarily on displacement.  The purpose behind the minimum weights is to try to create parity amongst the different cars in the class.

When we built our car, the formula was as follows:

Engines with displacement less than or equal to 1667cc:

1.10 x displacement (cc)

Engines with displacement greater than 1667cc:

0.95 x displacement (cc) plus 250 lbs
In addition, due to the age of the rules, there was also a weight penalty for cars running wheels wider than 7".  In general, many of the cars running in Prepared have been older cars, and thus 7" wheels used to be considered wide.  That weight penalty was 75 pounds for wheels up to 10" and 150 pounds for wheels over 10".

Therefore, the formula for our car was:

0.95 x 1999 (displacement) plus 250 lbs, plus an additional 75 lbs for our 10" wide wheels.

Total minimum - 2,225 lbs

As a comparison, our primary competitors in DP are 1.6 L Miatas and 1.8 L Miatas.  Their minimum weights were 1,758 lbs and 1998 lbs, respectively.  So, there was a 240 pound difference between the two earlier Miatas, and then another jump of 227 pounds to us.

Prepared rules allow for pulling a lot of weight out of the car since these are effectively full on race cars.  Unfortunately, a bone stock MX-5 comes from the factory weighing a published 2,441 pounds.  And, in fact, our previous CSP MX-5 weighed only about 2,320 pounds. 

We obviously took advantage of the weight reduction rules when building the car, and ultimately had to add back about 225 pounds to the car to reach the minimum weight requirement.  The nice thing was that for local events, we were able to run with a passenger in the car and be at our minimum.  For big events, we had plates of steel that we put in place of the passenger seat.  We got these steel plates from our sponsor, Where2Race.  They were coated in rubber for moisture protection/rust prevention.  Due to their size, we were able to place the front of them on the support rail that the front of the seat bolts go into, and then drill holes through the plates to use the factory rear seat mounts.  We then used some 1 1/2" steel strapping between the front and rear seat mounting points to hold the weight securely in place. 

By using the factory mounting holes for the seat, we were able to make it a fairly easy change between local events and big events.

Fast forward to the winter of 2011/2012, and a change in the minimum weight calculations.  Since pretty much everyone in the class had to add weight to the car to reach the minimums, the SEB (Solo Events Board) made a change to the minimum weight calculations for DP.

The new formula is as follows:

Engines with displacement less than or equal to 1667cc:

1.06 x displacement (cc)

Engines with displacement greater than 1667cc:0.91 x displacement (cc) plus 250 lbs

 

Of additional importance, is that the 75 weight penalty for up to 10" wide wheels went away.  For us, that changed our minimum weight to the following:

 

0.91 x 1999 (displacement) + 250 lbs, for a total of 2,070 lbs. 

 

This change allowed us to shed 155 lbs for the 2012 season.  Since we were using either steel plates or a passenger for approximately 225 pounds of add-on weight already, this was an easy change to make, as we only needed to reduce how many steel plates we had in the car for National level events.

 

The finished product with the steel plates firmly in place for the 2012 season.