12th scale cars go off of roll out as the tire diameter is changing. The equation is (tire diameter x 3.14) x (pinion / spur). Starting point for roll out for 17.5 would be 90-95 and for 13.5 70-75 depending track size.

Here is a calculator as well. https://www.tqrcracing.com/rc_tools/rollout.asp

I just raced my first race in a State Race with a 12 scale and at present my knowledge is very limited.

In the first qualified I qualified 4th with a total of 11 guys so I was happy. I hit my marks well.

We are racing a 21.5 motor with a GT body. My questions are as follows:

Per the above post can I assume the roll out would be at approximately 105 for a large asphalt track? I was at 95.64 I seemed to have the same straight speed as others. My batteries did seem to fade, but I was using older packs..... Motor temp was acceptable at 154 degrees. I put a fan on it for Q3 and the mains and the temp dropped to 120 degrees.

As tires wear should I go up a tooth or two in my pinion size?

Optimally, what is the best diameter for my fronts and rear tires? (We get about 7 runs out of the fronts and probably twice as many out of the rears... It should be noted, that I changed out my tires for a new set (Not cut) for Q3 and the same set for the mains. I was slower in the mains than my Q1 time. I had good grip... Any thoughts?

All you had to do is come over to my tent and ask. (Boylan soda sign). I would be glad to help you. I ran my CRC CK25 ,By the way I was the 3rd place car in the Q1 with the 59 Brumos Porsche body. I had a tire truer with me if anyone needed to use it. I used the CRC Pro cuts and cut them to 42mm. Trinity 21.5 XFactor with either a 54x70 and then 54X72. My problem in round 3 is I got feeling bad and that was it for me. The 2- 3 guys on top are usually on top. If your going to Beachline I true my tires to 41mm but others run lower (skins on a rim). Gear ratio about the same as it is a big carpet track.
Almost forgot for Carpet some at using the straight axle set-up bring both and try what works for you.

What is the deal with charging 1 cell packs? I thought I'd use my standard X6, set it for one cell, skip the balance plug and let her go. I started researching new cables and see this 1 cell cable uses a XH connector. Why would that be? Is it required?

https://cimg2.ibsrv.net/gimg/www.rct...b685f005a2.jpg

Generally not for cells over 1500mah..../ aka not for RC cars....some small Airplane packs or cells for drones use the other XH plug since they are too small for tubes, hence not an option to charge with.

Alot of the iChargers use the balance port for cell voltage monitoring, even on 1s. You can disable in the menu and just measure from the charge lead, but it's just as easy to plug the xh connector in and not have to remember how to enable or disable balance charging each time you switch cell counts.

My 2s charge leads have a 2mm bullet plug installed so I can switch between 2s and 1s charging without changing the entire harness or digging through the menus.

I'd use the 1s balance plug. Charging is way more precise using all 4 wires. IIRC, I had to cut one of the tab ears off.

Single side damper tube.
 

I've seen a few guys pics using only one tube.
What is the science behind using only one damper tube.

Easier to run wires
+ Overall less dampener (which is good for spools)

Ok what if you run it with no dampers and stiffer side springs.

I've done it (accidentally). In general it feels not nearly as bad as you think. It just not the fast way around the track. Going too light on side damping generally causes double steering which greatly reduces corner speed.

At one point way way back, it was a thing to run no side springs with very thick lube.

We were running such light fluids in the dampers that it just dripped out, evaporated, or went wherever it goes (the rainbow bridge?) too soon. It was inconsistent.

Single damper allows us to return to a lube twice as thick, and is more consistent every run.

Also some retard engineers didn't leave enough clearance for the battery posts, with the battery in the rear position. And the post side damper gets knocked off in a crash. Notice that it's almost always the post side damper that's removed. Some classic onroad dummy design work there.

Indeed but you have to look closely the dimensions of the LiPO before buying because LCG shorty does not assure that it is compatible.

My CRC had this problem, battery post would hit the dampener tube, so I took my Dremel tool and buzzed a chamfer into the post and it fit great.

I think running just one tube makes you look like you made a mistake.

I never had that problem with my CRC? I've done the one tube test before. I've also run without tubes at the birds before.