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This is a place to share knowledge related to 1/12th scale racing. It is not to be used for conversations.

KITS:
Click links to go to manufacturer product page. If any are missing please add them!

TIRES:
Pre-mounted tires readily available in the US:
Pre-mounted tires readily available in the Europe:
  • Hot Race ??

Gluing your own donuts:
https://www.youtube.com/watch?v=hm7z1rz-74s - Special thanks to Edward Pickering!
Truing tires:
https://www.youtube.com/watch?v=8wqHOLWq6Uc - Special thanks to Edward Pickering!

The following information came from HERE, with some editing and information added. Thanks Christian!

THIS MAY NEED UPDATING FOR THE NEW BLACK CRC CARPET

Brands:
BSR, CRC, Jaco:
Pro One is no longer selling to the public, but it and the brands above are all mounted by BSR and use the same foam. The nomenclature of the BSR vs Jaco/CRC is a little different in a few instances but is otherwise the same. The BSR foam consists of three families, and can be identifed as synthetics, naturals, and blends.

Synthetics - The old school, light weight, easy to true "dry feeling" tires. These include tires like CRC/Jaco Yellow (BSR White), Black, Gray, etc. These tires offer the highest wear rate and lowest grip. Many racers continue to use these nder high bite conditions.

Naturals - These tires are usually the best alternative for low bite and asphalt. They include Pink, Magenta, Double Pink, Lilac (BSR Team Purple), Purple, and other tires. These tires provide a ton of grip, but tend to get sticky in high bite conditions. This rubber does not wear as easily, and the cars will pick up gunk and fibers from the carpet under most high bite conditions. This is especially bad if the humidity is high.

Blends - These are the tires most people run today. They were initially called "JFT foam" by some, as it was believed that the tires were the same as the JFT tires. We can divide the blends further into two groups: high rubber and low rubber content. The high rubber would be the new rear Orange and Red from the BSR family, and the low rubber would be the Green and Blue varieties. When, asked about the difference, John Foister from BSR Tires said they came from the same "family" of foam, but they offered different grip. According to John, the Green/Blue has more bite than Orange/Red, but from track testing Oranges offer more bite than Green (being equivalent to in hardness) when the grip is high and absolutely no grip when it is lower. The Orange foam has a denser pore structure and the tire is not as prone to chunking. It is also important to note is that BSR Blue rears are not the same as the BSR Blue fronts!

JFT:
JFT stands for Japan Foam Tire. They started the new wave of foam tires we are all using now (Blue/Blu, Green/Greene, Dbl Blue, etc). These tires are a little different than the BSR tire family, but work in very similar conditions. They offers four varieties A (asphalt), C (carpet), S (???), and R (???). This does not mean that those types only work on that surface, but this is what they recommend.

JFT uses the same foam for fronts and rears if the color is the same.

A: Used on asphalt, considered close to the natural rubber variety and are named consistently with other natural tires.
C: Used on carpet, considered a blend.
S: Used on carpet?, tires are ???
R: Used on carpet?, tires are ???

For setup, the JFT foam seem to generate more bite than the BSR, therefore the car tends to be a little more aggressive.

Ulti:
Ulti is another Japanese brand that offers an array of compounds. They have their own way of rating tires, and are difficult to equate to other brands. They have 4 different varieties, each in varying degrees of hardness.

J: High rubber content tire, similar to Pink/ Magenta. Soft would be close to a pink. These offer the most bite and are great for asphalt/carpet front tire. (J hard being very popular)
X: "Balanced" blend, similar to JFT Blue/ Green. Soft is equivalent to Green, medium to Blue in hardness. Great for carpet!
Y: High synthetic blend with lower grip, and is not a very popular variety.
Z: A very expensive "special" foam that is supposed to be magic on asphalt. Only make it in soft shore.
European tires:
There are many great European foam tire brands that use their own types of foam, as well as traditional foams. SOmeone with more knowledge about them will need to fill this in!

Tire Diameter:
If you are racing on carpet, you have to evaluate how much grip your track has. If your track is low to medium grip, you can run bigger tires. If you are on higher bite you have to cut them smaller, there is simply no way around it. Bigger tires are needed for asphalt, especially in the rear. The larger tires provide much needed lateral bite.

Carpet (mm):
Low - Medium Bite
Front: 42.0 - 42.5
Rear: 42.5 - 43.00
Medium - High Bite
Front: 40.5 - 41.0
Rear: 41.5 - 42.0
Big Race
Front: 39.5 - 40.0
Rear: 40.5 - 41.0
Asphalt (mm):
Parking Lot
Front: 43.0 - 44.0
Rear: 44.0 - 45.0
Prepped High Bite
Front: 42.0 - 43.0
Rear: 43.0 - 44.0

Tire Saucing:
Most facilities have moved towards odorless traction additives such as SXT. Some of additives evaporate very quickly and some do not. This seems to be something that is also dependent on tire compound and ambient temperature. For example, saucing a Green compound seems like it never dries, especially when tjhe temperature is lower. We have found that wiping the tires off 15 minutes before we go run allows the sauce to cure, which makes the car come in much quicker with Green rears. Blue compounds on the other hand, do fine when wiped off right before hitting the track.

Saucing half front and full rear is a good initial starting point. If the front of the car is too agressive you can sauce les than half, or for a shorter amount of time.
Tire Fuzzing:
In conditions of increasing grip, foam tires will somewtimes get sticky and pick up fuzz and debris from the track. This is highly dependent on the rubber sedan tire that is being run at your local track and the compound/ type of foam you are running on you car. The softer the sedan tire and the harder/higher rubber content in your foam tire, trouble with fuzzing seems more likely to occur.

There are ways to get around fuzzing under most conditions, and usually involves the selection of the correct foam compound. The more fuzz you get, the softer/lower rubber content you want to run.

Examples:
Problem: Car fuzzes with Lilac/Team Purple fronts and car starts pushing.
Solution: Use a softer front tire and or different family of foam. Replace it with Blue or Double Blue front.

Problem: Car loses rear bite 6 minutes into the run. Blue rear tires look almost clean but have small carpet hairs.
Solution: Use Green rear tires. The softer compound wears instead of getting sticky, minimizing fuzz.

Tire Selection:
Starting out, pick 2 tire compounds for the front and rear. The following should have you covered 99% of the time.

Front - Green and Blue (BSR) or Green and Light Blue (JFT)
Rear - Blue and Double Blue (BSR) or Blue and Dark Blue (JFT)

You may wonder about other compounds out there and if they might be better, trust me, they probably won't be. Even if there are other tires that can be as fast, the synthetic family wears out really fast and the high natural rubber will probably fuzz on you over an 8 minute run. The blends family seems to be the most versatile foam type available today. They last awhile, and sticking to them will make your process of tire selection simpler.
Tire Charts:
BSR/CRC/Jaco



Contact



Corally



JFT (Japan Foam Tire)



Ulti



Enneti (Xceed)



ELECTRONICS:
ESC:
As of now, ROAR is staying 1S (3.7V nominal; 4.2V fully charged) for 1/12. There are many 1S ESC's with a built in BEC so nothing else is required to power the receiver and servo.

If you don't want to lock yourself into a 1S specific ESC, you do have other options! It is possible to use your 2S ESC without a booster or receiver pack, and the ESC simply supplies the lower voltage. If that does not appeal to you, you will need to use an Rx pack or booster. The Rx pack and booster will both supply the receiver with a higher voltage than the 1S pack.

If you decide to use an Rx pack, MAKE SURE TO REMOVE THE RED WIRE FROM THE ESC PLUG THAT GOES INTO THE RECEIVER!!!

If you choose to use a voltage booster, it works exactly how it sounds. Instead of plugging the ESC into the receiver, it plugs into the booster, and the booster plug goes to the ESC, supplying the higher voltage.

1S ESC:
If there are any missing please add them!!

If anyone would like a need for a chart comparing the ESC's specs PM fenton06 and I'll get one made and put in here!
Voltage Boosters:
If there are any missing please add them!
Servos:
BODIES:
Black Art (CRC - US Dist):
  • Audi R8C - BA002 - .020 Thick



  • Black Market (Mohawk 12) - BA005 - .020



  • Lola B10 - BA006 - .020 thick
  • Toyota TS030 - BA008 - .020 thick

    Lola - black/red, TS030 - green/pink


PROTOForm:

Reflex Racing/RSD:

SUSPENSION ADJUSTMENTS:

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Old 11-30-2007, 02:16 PM   #27631
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Quick question.

Just rebuilt my L4 (for the hell of it) and have noticed that the captive balls in the T-bar "float" up and down a little bit. There doesn't seem to be any side to side play so shouldn't cause any crabbing problems, but will the up and down float cause any issues? We're only talking 0.25mm here, but would it be enough to cause any problems while in use? Or am I being too paranoid?

Stu
You can also take the cups apart and very lightly sand the two flat surfaces that meet together to capture the pivot ball. Be careful not to take off too much as the ball will be too tight and that is not good either. It's a trial and error thing. Do a couple of swipes on a piece of #1000 sand paper on a flat surface and screw it all back together and see how much of the play you removed. It there is still too much play, then repeat the process only doing a couple of passes on the sand paper at a time until all of the play is removed but the ball moves freely.
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Old 11-30-2007, 02:40 PM   #27632
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Originally Posted by StuartC View Post
Quick question.

Just rebuilt my L4 (for the hell of it) and have noticed that the captive balls in the T-bar "float" up and down a little bit. There doesn't seem to be any side to side play so shouldn't cause any crabbing problems, but will the up and down float cause any issues? We're only talking 0.25mm here, but would it be enough to cause any problems while in use? Or am I being too paranoid?

Stu
Stu,
Take the mouldings apart and take a couple of thou off the flat one by running it across some 1200 grit wet & dry. Rebuild and check the float, if there is still some repeat.

Jason
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Old 11-30-2007, 11:23 PM   #27633
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i remember having to do that when they are new.
but its all in building a car.
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Old 12-01-2007, 01:22 PM   #27634
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What size pinion do i want to use for a Stock class brushed motor. I have a 100 tooth 64 pitch spur.

Where do i want to be for a brushless 13.5 motor

Thanks
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Old 12-01-2007, 02:28 PM   #27635
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What size pinion do i want to use for a Stock class brushed motor. I have a 100 tooth 64 pitch spur.

Where do i want to be for a brushless 13.5 motor

Thanks
For a CO27 I usually run 48-52mm rollout on a 100x48 track or as little as 38-40mm on a 58x36 track. I don't run brushless but most people usually gear a 13.5 into the mid 60's which you'll never reach with a 100 tooth spur.

Rollout = (tire diameter*3.14)/(spur/pinion)
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Old 12-01-2007, 02:40 PM   #27636
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What size pinion do i want to use for a Stock class brushed motor. I have a 100 tooth 64 pitch spur.

Where do i want to be for a brushless 13.5 motor

Thanks
You should get an 88 tooth spur, you'll strugle to get to the proper rollouts with that tall a spur.
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Old 12-01-2007, 04:15 PM   #27637
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What size pinion do i want to use for a Stock class brushed motor. I have a 100 tooth 64 pitch spur.

Where do i want to be for a brushless 13.5 motor

Thanks
1.750-1.800 for rollout on a stocker. Toss the 100 if your going 13.5. Its just not gonna happen unless you go to a much smaller spur. 78 tooth spur from RW is nice to use if your going with a 13.5 and roll it out in the 60-65mm range like what was posted earlier.
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Old 12-01-2007, 05:28 PM   #27638
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Here's a roll-out tutorial I just sent to the new 1/12 racers in our club. I really do believe that doing the math a couple times helps it all make more sense...plus you get a better idea how changes in this or that affect your roll-out. A tooth on the pinion or a mm of tire diameter make a couple percent difference, a couple teeth on the spur don't make much difference, etc.

This comes under the heading of "give a man a gear combo he'll know roll-out for the day...teach him to calculate roll-out (and what it means) and he'll know roll-out forever. AND be able to teach someone else!

Please feel free to correct if you find any errors. My typing ain't all it could be.

================================================== ========
I sent some information to Neal without really thinking that he (and maybe you guys) probably have never been exposed to roll-out. This is the kind of stuff that will drive you bat-shit because nobody ever really just spells this stuff out. OUR big goal, though, is to keep you guys from getting frustrated (like we invariably did).

Here's a bit of a primer on roll-out.

Gearing a foam-tire on-road car is ENTIRELY dependent on the current diameter of your tires. What you're trying to find is how far the car moves forward for every revolution of the motor. To express it any other way is hopeless because of the fact that foam tires change diameter where rubber tires, effectively, do not. Also we'll see why the question "what gear to run" is impossible to answer without some of the other variables answered.

Just as a reference point I've found for brushed motors in 1/12 that a 96T spur gets pretty much all the combos you need for our tracks. Then it's a matter of measuring your rear tire dia. and consulting the roll-out chart to find desired roll-out and what size pinion gets that for you. I will show you these charts Sunday next. BUT...like a lot of things in life you will gain a FAR better appreciation and understanding for this phenomenon if you do it the hard way a few times. Remember that prior to PC's and easy to download Excell share-sheets we had to manually calculate roll-out and this is a good skill to have because even now I'll end up with an oddball spur gear or a value that doesn't show up on the chart. Or I'll leave my charts someplace. Or... Plus the mathematician/math teacher in me LOVES this stuff!

This is where your high school geometry comes in handy (you remember...the stuff you and every other kid on earth said "but I'll never use it"). Roll out is calculated using good ol' pi (3.14159...). You multiply the tire diameter by pi and that gives you the tire circumference (distance around the tire). Then divide your spur gear by the pinion gear to get your final drive ratio. Finally, divide the tire circumference by the fdr and you have roll-out. The roll-out charts all do this but it is performed on an Excell spread sheet.

What you're usually trying to do is find what pinion to use. If you know your tire dia/circumference, spur gear teeth and desired roll-out value you can identify the pinion size that yields your desired roll-out with a little algebraic manipulation.

The base formula is (remembering that / means "divided by"):

(pi X tire diameter) / (spur teeth / pinion teeth) = roll-out

Let's call (pi X tire diameter) "tire circumference" and (spur teeth / pinion teeth) "final drive ratio" (though we probably won't use this for now).

As I said, the mystery number is usually the pinion teeth so we want to segregate that variable.

Our base formula is now:

(tire circumference) / (spur teeth / pinion teeth) = roll-out

Noting that we have a "double division" in this base formula (basically a fraction in the bottom of a fraction) our first step is to take the bottom fraction, (spur teeth / pinion teeth), invert it and multiply by the tire circumference, giving:

(tire circumference) X (pinion teeth / spur teeth) = roll-out

Now we multiply both sides by spur teeth giving us:

(tire circumference) X (pinion teeth) = (roll-out) X (spur teeth)

Finally, divide both sides by (tire circumference) and we get our desired result:

pinion teeth = (roll-out X spur teeth) / tire circumference

Seems like the long way to get there but THIS is the point where you'll start. This last is the only formula you'll need if you know everything BUT the pinion gear size. I just showed the math to get there as proof. Please note that there are a couple ways to get from there to here but the result will be the same.

So, say you're like me and have a 96T spur gear and new 48mm dia rear tires. You want to be a little conservative so you're going to start with a 40mm roll-out (I think I'm running about 42-43mm in Stock). The pinion you need is found by:

pinion teeth = (40mm X 96 teeth) / (48mm X pi)

Remember that pi is approximately equal to 3.14159 (you can really stop at 3.14, but what's the fun in that?)

pinion teeth = (40mm X 96 teeth) / (150.8mm)

pinion teeth = (3840 mm teeth) / 150.8mm)

When we divide out the right side the mm cancel leaving only teeth AND the desired result.

pinion teeth = 25.46 teeth

NOW...a 25.46 tooth pinion is a bear to find, and it usually doesn't mesh worth CRAP even if you do locate one. You'll need to round up or down, especially since you're nearly exactly in the middle. This little difference probably won't be catastrophic (provided your initial assumption was "conservative" as I did) either way, so I'd probably do a 26T pinion and settle for the 40.84mm roll-out.

NOTICE...the roll-out we "accepted" in this example is almost a full mm more than what our target was. THAT'S how quickly things that seem really small can change things once multiplied back out. This difference is about a 2% variance but such is what we're left with since we can only go to full tooth intervals on pinions. The only alternative would be to true the tires down a nick. I can find that amount (if I was really concerned...in this case I really wouldn't be but will make the entire case for our discussion) by going back a step in our earlier calculation to where we had:

(tire circumference) X (pinion teeth) = (roll-out) X (spur teeth)

And divide both sides by pinion teeth to yield:

tire circumference = (roll-out X spur teeth) / pinion teeth

tire circumference = (40mm X 96 teeth) / 26 teeth

Multiplying and dividing (this time "teeth" cancel) we find that the tire circumference to hit EXACTLY 40mm roll-out would be 147.7mm. Divide this by pi and we see we need to true the rear tires to 47mm...taking a full mm off of them. Again, a bigger result than anticipated, but that result is multiplied by over 3 X to enter the equations.

Once you're comfortable with roll-out we'll tackle ride height adjustment.

hth guys,

Scottrik
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Old 12-01-2007, 05:49 PM   #27639
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Scott-
All I can say is...Whew!

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Old 12-01-2007, 06:02 PM   #27640
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Scott-
All I can say is...Whew!

That's whatcha get when you tell D.Powell I'm a "math geek"
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Old 12-01-2007, 06:09 PM   #27641
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Scotrick you got a pm from fl.
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Old 12-01-2007, 06:39 PM   #27642
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That's whatcha get when you tell D.Powell I'm a "math geek"
ROTFLMAO
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Old 12-01-2007, 07:00 PM   #27643
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ROTFLMAO
Then again, my bud Bambi (yes, her real name...and she's not a stripper) just says I'm pedantic. She's probably correct.
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Old 12-01-2007, 07:03 PM   #27644
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I for one can hardly wait for Scott's tutorial on body clips.
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Old 12-01-2007, 08:10 PM   #27645
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I for one can hardly wait for Scott's tutorial on body clips.
You know I've already seen this, I quit reading when he said take out a Trinity Spring Thingy and check the spring tension!
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