This advise is fine for very hi grip track conditions, however, on low to med grip, you can run the tires bigger. For club racing, I usually start at 43.5mm in the rear. If the car is grip rolling, take out front camber until it stops, if this does not fix it, then go down on diameter, or try a harder front tire. Remember, as you make the tire smaller in diameter, you are effectively making the tire harder, and taking away grip.

For a track with low to med grip
I would true a few sets to 42Fr 44Rr, take a few runs on each, then true to race size

Normally it takes a bit to get used to the track, and fine tune some things on the car, so I'd rather not use 1 run tires for this

Smaller is almost always going to handle better though, and Andrews sizes are the go to for maximum performance at a high bite track

For mod practice I start tires at 42 to 42.5 mm (huge!!) and they will normally last for at least six to eight full 8-minute runs of mod before they are too small. I personally find that going any larger in diameter just makes the car drive like shit since the roll centers are jacked, so I don't even bother.

For big races (medium to high grip) I would start with 41.5 mm and then put a practice run or two on them so they are right around 41 mm for quals and mains.

EDIT - sorry, realized I didn't explicitly say I was referring to rears. For fronts just take off one mm or so from the above, depending on how much rake/stagger you like running.

The Serpent S120LTR already has this feature. The main lower pivot ball is suspended from a hinge pin. The hinge pin swivel for/aft, so the lower main pivot ball can't possibly bind. Also, the main lower pivot ball is captured by a threaded plug, so the amount of play can always be adjusted, as parts wear. The main lower pivot ball can also easily be replaced without tearing the whole rear end apart. No messy football or locknuts to deal with.

I've been reading that it's good to run 1mm or so shorter front tires than rears. What benefits does this give?

The stagger in general biases your front to rear grip. A larger delta in my experience takes away steering.

I will be be the first to admit I am no expert when it comes to mod. I used to race on a low bite track with stock and larger tires gave more grip. When I began running mod I figured I would need loads of grip, so I ran larger tires at first, like a 44/42 r/f. I was amazed, after taking advice to cut them smaller, that even on the low grip carpet I raced on the car worked better with smaller tires. Maybe a better answer is run them as large as possible without grip rolling. Some of this will also be determined by differing perceptions of low vs high grip as well as other factors like carpet type and bumpyness. FWIW I start with the sizes in my first post on green layouts when I go to a new track. Although remembering now at Worlds in FL I do think we ran like 42.7 rears and 41.5 fronts because grip was abysmal. So maybe a little bigger than I mentioned could work after all, or maybe I should just quit droning on...

Hi again guys, I found an old post that recommends rollout between 85-87 for 13.5 blinky.. I know it depends on timing, track layout, etc. but does that sound like a good starting point? I have a 13.5 coming to practice with and need to buy some different pinions/gears to play with it. Just want to confirm a starting point to shoot for.

I am no expert on 1/12, today was my son's first time running it or any onroad for that matter. We were running uncut crc purple stripe tires and because I didn't have much for 64 pitch gears, we played around with 48 pitch. We ended up at 30/65, he qualified 2nd because he got stuck on a tube, but was ables to take the win by a little more than half a lap. Hope that helps some. We also used a reedy 13.5 1s ss motor with the timing turned all the way up.

Thanks for the reply, sounds like your son had a good day Do you know what the diameter of your tires were?

47mm, he is well known for his offroad racing program. Just playing with some onroad stuff to break it up a bit.

85 is a good place to start

That 48p rollout worked out to 68mm
Small track ?

Not sure on size, maybe 60 or 70 x40. We just changed gearing til he felt comfortable and his lap times were good. Tqed practice so that's what we stayed with.

Had a blast running modified.

However, the ESC gets pretty darn hot like 65 degrees Celsius hot. I'll let your figure out the temperature in Fahrenheit.

Jumping from 1/12th 21.5 2s to 3.5 1s isn't soooo bad. It's probably the most fun I've had in awhile. Having all that power at your disposal, wow. Love it. Just pull the trigger and let it rocket down the straight. You will need to adjust your driving style to accommodate for the extra power, such as smoother on/off throttle and turn in timing points on the track. By far the most important thing for me is being comfortable with your cars setup. I can see it being nerve racking if you don't know how the car will react in the next corner.

First round of practice...

After settling in on a decent tire setup I focused on tire diameters sizes. First I tried a large diameter of 42 mm and 42.5 mm. I found the larger sized tires difficult to cut in and follow through the corner. Though, easy to drive, I wasn't able to drive the car hard or tight into the corners. The sidewall being too large caused the rear to be locked in.

Next round of practice...

I decided to try out the complete opposite with 39.8 and 40.5 mm tires. I found the car was really fast and really quick in the corners. However, the foam was too thin and the cars rear end started to break loose after 3 minutes. Though, the tires were old, the lack of a sidewall made it difficult to maintain stability in the corners.


I decided to run 41 mm and 41.5 mm and that was the hot ticket. The car carried corner speed and maintained a good amount of traction in the corners for a 8 minute race.

Glad to hear you sorted it out. What compounds were you on?

Team Bomber Silver Compound front and rear.
The best foam compound I've used so far.