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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.

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

Pre-mounted tires readily available in the US:
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!


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 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 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.

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 Chart:

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Old 08-04-2002, 10:57 AM   #1201
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onaMISSION....that is a sweet looking paint job!!!!!!!
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Old 08-04-2002, 04:45 PM   #1202
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That is a nice paint job
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Old 08-04-2002, 07:26 PM   #1203
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anybody here do anything to there tires to keep them from chunking? I have heard of people putting show goo or CA on the sidewall but thought it would mess up the balance.
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Old 08-04-2002, 08:23 PM   #1204
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I know a lot of the sedan guys put a small bead of ca along the edge where the foam meets the rim. A small amount shouldn't hurt the balance any but if you are worried you can always rebalance the tire.
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Old 08-05-2002, 12:09 PM   #1205
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Alvin- Check out the pic from the World's at Orions website of the Corrally car. You will see that they made a graphite motor pod top plate and mounted an Associated style VSC center shock to it. They also use what look like CRC Side Dampers on it. If you call Windtunnel racing at 877-596-2403 I bet he could make you that top plate. I also think you will want him to make you a couple of .075" fiberglass T-bars for it since the stock Corrally T-bars may be too thick (I'm not sure).

Newracer- It seems that the number one thing you can do to prevent chunking foam tires is to make sure that the wheel wells on the body are properly cut out and that the body is properly mounted. If you compress the suspension fully by pressing on the body posts (with the body on the car) the tires shouldn't hit the body. Turn the front wheels first one way and compress the front suspension and then while still pressing down turn the wheels the other way. Make sure that the body doesn't rub on the tires or this will cause you to "chunk" them during cornering or a crash. For the rear tires push the side of the body inward and see if it hits the tires. The bigger the rear tires are the better up to let's say 1.95". By having wheel wells cut out for this big of a rear tire you shouldn't cut or chunk a rear tire. If you run on ashpalt mostly then you want to cut the rear tire wells to fit 2" rear tires because you normally need the extra clearance. For carpet racing we normally run from 1.94"-1.82" rear tires and the fronts are usually 1.74"-1.68". For asphalt racing I imagine that you would want rears between 1.99"-1.89" and fronts between 1.78"-1.72" (these are estimates since I don't run asphalt).
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Old 08-05-2002, 12:40 PM   #1206
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thanks for the replies

I haven't "chunked" any fronts yet but did a pretty good job on one of my rears. I think it may have actually hit something on the track or even a board.

what is the proper way to adjust ride height in the front? I use the spacers under the suspension mounts, should I also be using kingpin spacers?
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Old 08-05-2002, 01:03 PM   #1207
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What servo would you guys recommend to be used? Thanks!
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Old 08-05-2002, 02:09 PM   #1208
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Originally posted by Kraig
What servo would you guys recommend to be used? Thanks!
Good question. Back in the early-mid '90's I always ran the Airtronics 94143 or 94144, and nowadays my instinct would be to go with the Airtronics 94145Z, however I've been looking at the Futaba 9602 with some interest.

Has anyone used the 9602? Any opinions? My new Switchblade kit arrives tomorrow, and I'll have to choose between the 94145Z and the 9602 pretty soon... I wouldn't mind saving some money by going with the 9602, but not at the expense of performance.


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Old 08-05-2002, 02:20 PM   #1209
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look at the hitec mighty mini, if u get it mg + BB its got like 60 oz torque at something like .1 and it didint have slop like my 925 did. the mini are also only like $45
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Old 08-05-2002, 08:20 PM   #1210
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Hey could some help me out with a carpet setup for 4 cell 19t on carpet?

I purchased my first 1/12th scale. And I have no idea about tire size or anything for that matter any help would be much appreciated.......

you could email me one or just post it right here dukeone@mindspring.com

Jax, FL
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Old 08-05-2002, 08:33 PM   #1211
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What's up speedy! I thought we were running 6-cell Stock?

Duke forgot to mention this is brand new carpet, (if it makes a difference).

Last edited by Stika525; 08-05-2002 at 09:03 PM.
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Old 08-05-2002, 10:48 PM   #1212
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Duke1- I'm assuming that you will be racing road course. If you check through some of the prior post (such as pages 18-24) you will get some very good ideas about build and setups. Normal caster/camber/spring settings which are only a 1/3 of a setup in my opinion would be: 3deg caster, -2deg camber, Assoc. .020" springs. Hope this helps.

Kraig- I personally like/use the JR 3550Z and so do several top 12th scale racers due to its centering capabilities (resolution) and good torque capabilities (that seems better than its rating).

Add in JR's awesome support, good size/weight, a fair price ($60), good speed (.12sec/60deg) and tuff gear train (even though its nylon) and you have a great servo.

I had consistent problems with the Hitech 235AG servo's (3 of them) for 12th scale. It usually dealt with resolution loss since the motor isn't a coreles or 5 pole (like the JR and others). Also gear trains were hard to come by for me with the Hitech's and easy for the JR's (I've changed 1 gear in a 2yr old servo!).

However in all fairness Hitech has a new digital 12th scale servo out that may be very good (I can't remember the model number).

NewRacer- You are spacing the ride height correctly by putting washers under the lower supsension arms.
Spacing the the top or bottom of the Steering block will raise or lower the Roll Center. Spacing or "shimming" the kingpin will mostly adjust "Droop". I prefer some "Droop" at the bottom of the kingpin where the spring is so that the car has a little more on throttle steering and works a little better on bumpy tracks.
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Old 08-06-2002, 08:13 AM   #1213
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Alvin - Regarding the SP12G3. I used to run that car about 6 years ago (it seems). I put the small Delta shock on it and made my own fiber glass t-bar from .063 stock. Corally had glass t-bar, but it is thicker. I used the spring and shock to make tuning adjustments, rather than stay with the one t-bar. This combination made the car stable on the bumpy tracks in my area. I treated this part of the car just like the 12LC that was the hot Associated car at that time. Green spring with 30 weight oil in the shock. I now suggest that you use the Associated VCS shock and test oils between 20 and 40. There are also many springs to try, starting with the green and you may make it all the way up to blue. Tiger talks about the upper pod plate and the "rod in tube" style damper, but I don't think that is necessary. Your biggest challenge is to get the Corally damper system to ride properly so that all motion from the motor pod translates to piston movement in the shock. As far as the option part you saw in, I assume, the Corally parts list/catolog, they are Yokomo shocks that are too large for the 1/12 scale car. That shock does not have enough tuning options to be of benefit. I used to use that shock on the F1 Corally. But I built a new F1 two years ago and used the VCS shock instead. That combination ran great. I wouldn't get too excited about the Corally effort at the worlds. I consider that car to be the result of band aids to adapt to the pavement.
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Old 08-06-2002, 02:38 PM   #1214
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what are the effects of having the servo mounted flat on the chassis instead of angled on mounts?

Car: RC12L3

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Old 08-06-2002, 03:01 PM   #1215
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it affects the ackerman a bit. With the servo mounted on a slant, the rotation of the center point moves somewhat forward and backward as well as left and right and this (I believe) helps correct the ackerman angles a tad.

If the servo is mounted flat, there is none of the forward and backward motion.

Is this observation correct, or am I imagining things. . .once again. . .
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