For those running the eXcelerate carpet tires on black carpet, what front and rear widths are you running? Building up the kit stock I have 188mm rear and 180 front (max spacer width)

189 rear, 186 front with the wide front end.

I just saw there's a +4 option and just ordered it. Was wondering how you guys were getting the wider front track width.

What about pre-load on the rear springs? what's a good starting point?

adjusters flush with the top of the carbon piece

190mm front and rear with stock setup and sweep tires...

Is there really a downside to running a diff outside of maybe weight and potential for failure?

Don't worry about getting the cars to max width. With our CG and the way the cars work, you don't have to run it in either the front or rear at 190mm. My personal F1 from Champs last year, Alpha, Nats and Canadian Nats was 188mm rear and 184ish front (depending on different brands of tires).

How did we end up running spools in the first place? On black carpet with pan cars using a ball diff, the inside rear wheel would lift enough that it would lose traction and spin - or diff out. That would slow momentum off the corner. Spools stop this from happening. They also make the car rotate aggressively mid-corner. Spools are also lighter weight and the lower rotating mass helps acceleration a little. Those benefits in mind, the down side of a spool is that it can snap loose or over-rotate the car on corner exit in mid to low grip situations. Some stay with the spool in these situations and go easier on the throttle out of the corners, choosing to drive through the negative effects. Driving with a spool on mid to low grip surfaces is challenging and costs you time when you are too hard on the throttle out of a corner.

Ball diffs are generally best at matching the wheel speed differences needed during cornering (inside wheel follows a smaller circle than the outside wheel) theoretically scrubbing the least amount of speed of all the rear axle choices. But, ball diffs are heavier, can diff out on high grip tracks, and need to be rebuilt every couple of weekends. Ball diffs are also less expensive than gear diffs. While you are learning, a ball diff will be the easiest to drive at the lowest cost. When I run one on the WGTR, I use 30k Kyosho diff grease to slow down the action so that it acts more like a gear diff. I clean it an apply new grease every two race weekends.

The Gear diff is kind of the middle option. It scrubs a little more speed through rear wheel friction than the ball diff, but less speed than the spool. It rotates well mid-corner, but not as well as the spool. It is capable of stopping the inside wheel spin on throttle off the corner, but without the snap loose effect of the spool. You can tune it to be closer to working like a ball diff by running lighter damping fluid or closer to a spool with heavier fluid. And, they last a long time. I ran the A12 diff for a full season without rebuilding it. The one in my son's car has been in there two full seasons. The negatives are the heavier weight and the overall cost.

My experiences:

17.5 foam on black carpet, spools are fine even in lower grip situations. If my son was still running 17.5, I would have him run the gear diff as he is learning. I would only run it in my 17.5 car if it were a very slippery track.

GT12 rubber tire on black carpet, on a high grip track, the spool is about 0.1 seconds faster for me. On a mid to low grip track, the spool is slower. I will probably run the gear diff in my GT12 car most of the time, except for bigger races with high grip.

WGTR on black carpet, on med to high grip tracks, I prefer the spool. It is a tenth or two faster. On a fresh layout or tracks with low to med grip, I much prefer the gear diff. Or if I show up and am just having an off day and I'm not keeping up with the car. I will put the gear diff into the car. Some days it just isn't worth working that hard and I want an easier car to drive.

You're just beginning. I would say that a gear diff on the F1 car would be a benefit. As for gear diffs failing, they are pretty tough.

As always, wonderful information, Hamilton! Gear diff for the F1 headed my way shortly!

I noticed my front wing was drooping more on the rh side so did the boil and got it back flat again. What is your method for boiling wings etc? Start with wing in cold water and let it come to boil? Dunk wing in already boiling water? Take it out and air cool? Let it slowly cool in the water? Is there really a difference in any of that?

I put the car on a flat surface, no front wheels, wing installed with screwdriver handles under both sides and heat the wing up with a hair dryer. This method has worked pretty good for me.

Boiling might not be necessary if you store your car on a flat surface with something under the wing to keep it flat on both sides. I doubt that the wing would be crooked after that...

Can anyone explain the difference between the -1.5, -3, and -4 steering blocks?

so you have inline axles then -1.5 axles which means axle is back from inline -1.5 mm. Then -3 is 3mm back and so on. Shortens wheelbase