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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. On black carpet the car may be numb to sauce changes, either a long or short sauce can produce very similar handling.
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. Alternatively you can sauce the front tires harder and tune the car for less front end bite.

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. Possibly a longer sauce will prevent fuzzing.

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

Rear - Green and Blue (BSR) or Green and Light Blue (JFT)
Front - 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!
DISCONTINUED 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:
Pan Car Front Suspension Tuning:
DISCLAIMER : The following tuning advice was written based on the tuning experience of the author and may not hold true for all cars, drivers, or surfaces. In the end the best tuning advice is to experiment and make changes one at a time so you can track your changes and find the car balance that works best for your driving style. One real world test is worth a million ‘expert’ opinions.

Front End Type:

All popular modern pan car front suspensions are very similar, with a few exceptions such as Speedmerchant New School but most of the info in this wiki applies to them as well. For the most part, they consist of a rigid bottom arm, an upper A-arm, and a kingpin with a spring. There are different flavors of this general design, such as the CRC Dynamic Strut that uses a threaded kingpin and upper pivot ball instead of the Associated style that uses a kingpin that goes through the entire steering knuckle assembly, but their operation is the same with the rigid lower arm and the upper arm controlling the arc of movement as the suspension is compressed.

Assembly:

More so than in almost any other part of the car, the front suspension of your 1/12 car must move absolutely free. Reamers and hobby knives are important here, as any binding will cause the car to corner unpredictably. A little play in the suspension is a good thing, and racers will often find that ‘worn in’ suspension pieces function a little better than new.

Springs:

Besides tires, spring rate is the most important part of deciding how your car will handle through corners, but are somewhat complicated. As a general rule of thumb, a very hard front spring will have somewhat less steering grip than a softer spring with the same suspension setup and tires, but not as much as in other classes such as touring or offroad. On carpet, springs of different tension can be used to tune how your car will maintain or lose energy through corners with the following general rule of thumb:

Hard Spring (0.55mm or harder): Less overall steering, quick reaction to driver input, less on power steering, harder turn-in with potentially lazy mid-corner and exit.

Soft Spring (.45mm): More overall steering especially at low speed, slightly slower reaction to driver input, more on-power steering, less aggressive turn-in but can ‘hook’ and give better mid-corner and exit.

It is worth noting that front springs from different suppliers are often very different, in both height, wire thickness, and coils for a given spring height meaning that a “medium” spring from one manufacturer may be the “hard” spring for another. To make accurate changes you may want to use one spring maker and stick with their line.

Another aspect to pan car springs is that they can get “blown out” and collapse, no longer as stiff or as tall as they were. These should be replaced with fresh springs to ensure consistent handling.

Dampening:

This is generally a minor adjustment, but adding dampening tube fluid to the front kingpins of a 1/12 car can give it a little more initial steering. Often unusual compounds see use here, such as Losi Smart Diff Grease or Associated Green Slime being a popular front kingpin lube.

Caster and Reactive Caster:

Caster is the angle of the kingpin, almost always angling back to the rear of the car, with a typical range from 0-10 degrees. Increasing your caster will typically result in less turn-in but a little more control, more steering exiting the corner, and somewhat increased straight-line stability with less tendency to wander because a wheel running caster will tend to straighten itself. Less caster will usually give you more off-power steering, but often with correspondingly less on-power when accelerating out of the corner.

Running reactive caster attempts to use both of these aspects to increase overall steering: when the car loads up on the outside front tire, the caster angle decreases, increasing the front end ‘hook’ as you enter the corner and then giving you the high caster on-power steering as you exit and weight is transferred off the front end. More reactive caster means more overall steering, but can mean you may have to adjust your driving style to drive more ‘ahead of the car’, needing to predict where the front end will grip.

As grip increases, less reactive caster is the normal tuning change made to keep the front end of the car from gripping too hard and oversteering and prevent traction roll. Static caster adjustments are still used to change the cars on power / off power steering balance.

Reactive Camber and Front Roll Center:

Reactive camber or camber gain is how much camber is added the front wheels as the suspension compresses. This can be increased or decreased by changing the angle and length of the top arm. Short, angled arm = more. Long, flat arm = less. More reactive camber will typically cause the car to “roll up” on the outer front wheel, transferring more weight in a turn and give more steering up to the point at which the tire is overloaded. This is generally more front grip and weight transfer than wanted on carpet, and as a result most cars run a flatter longer front arm.

Roll Center is the point on which the car will twist laterally or ‘roll’ during cornering. This can be raised or lowered by changing the angle and length of the top arm, with a short angled arm raising is slightly and a long flat arm lowering it. From what I have calculated most modern 1/12 cars meant for carpet have a roll center somewhere around the height of the chassis plate or just below it, but due to the lower arms being rigid and flat the roll center cannot be under the bottom of the tires like it often is on a touring car.
These two are inexorably linked in pan cars. Top arm length can be changed by the top arm mount in or out using shims or a CRC Long Arm kit, but is generally a minor tuning choice. Tuning of roll center with shims is usually a minor tuning choice in a pan car with a rigid bottom arm due to how the car cannot gain extra mechanical advantage on the lower arm as you can in a touring car, while reactive camber can be a significant driver of the car’s performance. In a modern car running on carpet the kit setup is usually perfectly fine.

Front End Alignment:

Static camber is the angle of your front wheels at rest, typically somewhere from 0 to 1.5 degrees on a pan car depending on surface, tire choice, and other factors, but a good starting point is usually somewhere around 0.5 degrees. More camber will typically give more steering, but many racers use static camber to ensure that their tires wear flat even if that means not having exactly equal camber on both sides of the car. This is adjusted by threading in and out the upper turnbuckle or pivot ball.

It is also worth noting that when running on high grip the flex and deformation of your chassis, suspension parts, and front wheels can become significant and cause uneven front tire wear. Some troubleshooting of the right combination of static camber, camber gain, caster, and tire/rim choice may be necessary to ensure even front tire wear.

Toe-In:

The front toe is one of the more easily adjusted aspects of the car and can have a significant effect on the attitude of the car due to it being a quick way to moderately adjust Ackerman without making significant other changes. With nothing else being adjusted, going from zero toe to toe-in will give a car a harder turn-in and will tend to scrub speed with the front end as opposed to using drag brake. This can be necessary when racing in Super Stock or higher power classes and will allow you to drive more aggressively, and can help the car track straighter under power. Toe-out will tend to make the car coast more through corners due to reducing the steering angle of the outer front tire. If a car has too much off-power steering but is otherwise stable, adding toe-out can calm the car but may the car to wander on the straights especially if the front end setup is very soft.

Ackerman:

Ackerman is the difference in steering angle between the two front tires during a turn. It is the result of how during a turn the inside of the car experiences a tighter circle and needs correspondingly more steering angle, but is also an important tuning tool. More Ackerman means having more inside wheel steering angle relative to the outer wheel, less means that the difference in steering angle is smaller.

To add or remove Ackerman, using a servo horn that spaces the links further apart (such as a Kimbrough Small Servo Saver, the outer holes on a Tamiya or Xray servo saver) will have more Ackerman than a servo that puts the links close together (Kimbrough Medium inner holes, Tamiya or Xray inner holes.) The rule of thumb is that a servo that puts the ball studs close together but spaced away from the servo horn will have less Ackerman than one that spaces them far apart and close to the servo horn. Ackerman changes will have the same effect as changing toe with more Ackerman being effectively toeing the wheels out and less toeing them in, but will not affect the straight-line attitude of the car.

Turning Circle / Steering Angle:

In offroad or even touring car you can set up the car to use the full angle of the steering 100% of the time. You will almost certainly not be able to do this in 1/12 scale. It goes without saying that as you turn up your steering angle you will gain steering often to the point of the car being undriveable. The quickest way to set the steering correctly is to set the sub-trim in your radio such that the car tracks straight and the servo horn is straight up and down, then set the endpoints equally such that they don't quite hit the steering bump-stops, then turn down the dual-rate or total throw from there. A typical starting point is somewhere between 45 and 60% of the total steering throw, or a 4-5' turning circle.
Pan Car Rear Pod Tuning:
Modern pan cars are all link cars with a center pivot ball and solid rear axle. This suspension system is required by ROAR rules and has the advantage of being simple, lightweight, and inexpensive compared to other more exotic methods of rear suspension, but it has some complicated movements that can be unintuitive.

Motion of the Rear Pod:

Due to how the rear pod is a solid axle, the only motion the pod itself sees is the main pivot up and down, but due to the main chassis being independently sprung it will feel the lean, dive, and squat of the main chassis as the car is driven. The lateral forces of the main chassis during cornering is transmitted through the main pivot ball and side links, the roll through the side springs and side dampeners, and the squat and dive through the main shock and spring. In addition, the torque of the motor against the pinion gear both during acceleration and braking is significant enough to cause a change in attitude even in low-powered classes. The motor pinion will try to “climb” the spur gear, lifting the center pivot of the car and countering the “squat” of the main chassis weight being transferred backward by the acceleration or the opposite under brakes.

Main Shock:

The adjustment of the main shock of a pan car is one of its more important tuning parameters. Spring, dampening oil, and pod droop are all controlled by the main shock.

Main Spring:

A soft main spring generally means more rear grip and more forgiving off-power, while a stiffer spring can mean more steering especially off-power, but the main spring must also be stiff enough to prevent the chassis from dragging when running on high grip. For most cars the kit spring is a medium weight spring that is a good starting point.

Main Shock Dampening:

The weight of the main shock oil will determine how fast the car will react off-power. 30wt or roughly 300cps shock oil is a good starting point, going up in weight will increase initial off-power turn-in, while going down will generally make initial turn-in softer. Often a heavier shock oil can make the car transition from entry to mid to corner exit smoother, where a car with light fluid may have a more pronounced ‘hook’ in the mid corner.

Side Springs:

The side springs transfer the roll motion of the main chassis to the rear plate via spring tension. Softer side springs give the car more rear grip and can make the car have a smoother steering feel. Stiffer springs promote the cars rotation and give more steering. You can either pre-load side springs or let them float, due to all side springs being progressive beehive shaped springs pre-load makes them effectively harder and will give more steering, but a small amount of pre-load can also make the care more predictable and forgiving. In conditions of extremely high grip, it may be possible to run no side springs at all due to the steering afforded by the tacky running surface and helps prevent traction-roll, likewise in extremely low grip when rear stability is absolutely necessary. Generally 1/12 cars run soft side springs but stiffer ones can be very common in Pro 10, WGT, or WGT-R.

Side Dampener Tubes:

Heavier tube lube will keep a car flatter at corner entry, initiating quicker. It may also make the car square off the corner entry when the grip gets beyond med-high. Going lighter will reduce steering initiation and maybe preferred on higher grip. This parameter is really unique to the driver preference, as some drivers are very fast and consistent with heavily dampened cars while others prefer softer setups.

Droop:

Controlled by the length of the shock, adjusting the rear pod droop is extremely important on high-grip surfaces. Reducing droop prevents the car from transferring weight during cornering and will give more rear stability and prevent traction-roll or problematic lifting of the inside rear tires during cornering, low droop can also give the car slightly more on-power steering. Increasing will allow the car to transfer more weight and dive harder into corners, but by allowing the center of the car to rise you will be more prone to traction roll issues. A typical starting point is 1-2mm of droop from ride height, but 0mm is often used on high grip.

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Old 10-26-2005, 11:33 AM   #15181
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Quote:
Originally Posted by Crashby
I think the YRX-12WE (silver chassis) is the best asphalt 12th car available!! This is the car that OD, JRRC and I run at all the asphalt races. The reason it works so well on asphalt is that the batteries are placed out from the centerline of the car further than any other 1/12th car. By moving the weight out away from the centerline of the car, you get better traction on surfaces with less grip due to better weight transfer to the wheels on the outside when cornering. On carpet, which has much higher grip that asphalt, you want to move the weight closer to the centerline of the car. Yokomo does make a black chassis for the YRX-12, which has the batteries in closer to the centerline of the car. I will check my inventory when I get home and see if I have one still in the package with a part number
Awesome....and like you said, I might need that chassis.....cause there will be NO outdoor 12 scale here, especially with SNOW coming...LOL
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Old 10-26-2005, 01:09 PM   #15182
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Quote:
Originally Posted by rayhuang
CHassis and battery trays.
awesome thanks
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Old 10-26-2005, 02:00 PM   #15183
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Quote:
Originally Posted by Rookie Solara
Awesome....and like you said, I might need that chassis.....cause there will be NO outdoor 12 scale here, especially with SNOW coming...LOL
What I would do with that YRX-12 WE that you just bought from Mr. Shookie, would be to put a 12LR chassis, lower motor pod plate and rear chassis cross brace under it. Yokomo does not make a thick chassis. While the black Yokomo chassis does move the batteries in, it is still a thin chassis, which does not lend itself well for carpet racing. In the winter for racing on carpet, just throw the 12L4 chassis pieces under the Yokomo. In the summer, when you go outdoors, put the YRX-12WE chassis pieces under the rest of the Yokomo kit and you will have the best of both worlds!
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Old 10-26-2005, 02:41 PM   #15184
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Quote:
Originally Posted by Crashby
What I would do with that YRX-12 WE that you just bought from Mr. Shookie, would be to put a 12LR chassis, lower motor pod plate and rear chassis cross brace under it. Yokomo does not make a thick chassis. While the black Yokomo chassis does move the batteries in, it is still a thin chassis, which does not lend itself well for carpet racing. In the winter for racing on carpet, just throw the 12L4 chassis pieces under the Yokomo. In the summer, when you go outdoors, put the YRX-12WE chassis pieces under the rest of the Yokomo kit and you will have the best of both worlds!
Very much like everyone just told me........but it is hard to find 12L4 chassis (not even Tower has it).....
About Lower motor POD plate....exactly, what is that..? The whole lowering pod like those from IRS...?
And the Rear chassis cross brace......what exactly is that...?
There are several carbon fiber on a little car like that, and I am kinda lost track whcih one is called which....

If I am using this one for carpet........can I just use the 12L4 chassis..? Or I have to get the rest items to match the chassis...?

It almost sounds like it is cheaper to buy a used 12L4 afterall...thanks for your info....
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Old 10-26-2005, 03:06 PM   #15185
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Originally Posted by Rookie Solara
Kevin....once I am ready to be back at IRP, I will constantly bothering you about almost everything of 12th scale...just like last year with the pro 4.
(p.s....I might need idea about foam TC....right now, I have no cars and don't know what to get...)
No problem "Bunchbob"... Any of the new cars out there are good....
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Old 10-26-2005, 03:13 PM   #15186
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Quote:
Originally Posted by Rookie Solara
Very much like everyone just told me........but it is hard to find 12L4 chassis (not even Tower has it).....
Towerhobbies has it. Do a search "RC12L4". They have HEAPS of L4 parts as well.

But their search engine is really crappy. You really need to see your luck if you want to find something. The best is to enter the item# directly than 90% of the time you can find it.
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Old 10-26-2005, 03:18 PM   #15187
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I'm looking at getting a 2nd 1:12 for indoor carpet race only.

I'm driving a L4 at the moment and i want to try something different and i have my eyes on the CRC cars. Which CRC car do you guys recommend? I'll be racing mod and this car will be for indoor carpet only.

Our indoor track has quite low traction (probably lower than the our medium traction outdoor asphalt track) and no traction compound of any sort is allowed at all.
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Old 10-26-2005, 03:34 PM   #15188
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Quote:
Originally Posted by yellow15
I'm looking at getting a 2nd 1:12 for indoor carpet race only.

I'm driving a L4 at the moment and i want to try something different and i have my eyes on the CRC cars. Which CRC car do you guys recommend? I'll be racing mod and this car will be for indoor carpet only.

Our indoor track has quite low traction (probably lower than the our medium traction outdoor asphalt track) and no traction compound of any sort is allowed at all.
yellow

i have been using crc cars for about 5years they are one of the best out there .i have a 3.2R bloody knife and love it i use it for stock and 19 turn
. if you have any more questions about any of there cars just give them a call ,they will tell you which one is best for you.
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Old 10-26-2005, 03:42 PM   #15189
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Hey guys,

Looking for roll out on 19t and stock motors. Track is 70 x 36. I'm sure its on this thread somewhere, but its a huge freakin thread, LOL. Also, could someone post up the formula for roll out one more time.
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Old 10-26-2005, 04:14 PM   #15190
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Quote:
Originally Posted by zinger77
yellow

i have been using crc cars for about 5years they are one of the best out there .i have a 3.2R bloody knife and love it i use it for stock and 19 turn
. if you have any more questions about any of there cars just give them a call ,they will tell you which one is best for you.
Thanks Unfortunately i'm from New Zealand so calling them isn't the best option for me

And i hope some CRC owner can tell me their real life experience/feedback like the advantage and disadvantage/weakness of each CRC car.
Btw, i notice the 3.2R has a graphite T-bar? would it still break during a crash?
And the carpet knife is using somethign like a rubber band to secure the batteries!?? how good is it?
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Old 10-26-2005, 04:18 PM   #15191
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rollout= (tire diameter x 3.14) / (spur/pinion)

not sure what 3.14 equals in MM though, sorry
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Old 10-26-2005, 04:22 PM   #15192
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I ran my first 1/12 heats in 16 years this past weekend and the car made me look MUCH better than I am. I qualified in the B-main after two heats (no practice) but bumped up with a time/total that would have qualified me second in the A-main!! On my third pack.

I'd forgotten how much I loved DRIVING 1/12. I only got out of it then because it was such a battery war with the 1200SC batteries we had back then. It was cheaper and less hassle to race 1/8th gas on-road, so that's what I did. Then took a dozen years off...

You won't be disappointed with the CRC. Wonder how I'll do with it when I actually get it set up.

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Old 10-26-2005, 04:27 PM   #15193
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Quote:
Originally Posted by Northeast Racer
rollout= (tire diameter x 3.14) / (spur/pinion)

not sure what 3.14 equals in MM though, sorry
25.4mm/inch, so:

3.14 X 25.4 = 79.76mm

BUT (and this is a BIG but) I don't believe you have to convert pi to metric , just the tire diameter. Pi is pi. Or pi are round, or whatever it is mathematicians say. Pi is a fixed ratio (thank goodness or highschool Geometry would have been even MORE fun). If you convert both pi and the tire diameter you'll end up with a number that likely won't show up on any roll-out charts. Or if you convert pi and not the tire diameter you'll be similarly in error. Unless your tires are 3.14" in diameter...but I digress.

The tire diameter is all I need as I've got roll-out charts that accept both inch and mm diameter inputs. BUT...if you're really jonesing for some math you can do it all yourself.

Examples?

1.7" (tire diameter) X 3.14 (pi) = 5.34" (tire circumference) X 25.4 (convert to mm) = 135.59mm (tire circumference).

Now, let's suppose your buddy told you the guys at your track are using about a 44mm roll-out (1.73") for their layout. Circumference (135.59) divided by desired rollout (44) gives you your target gear ratio (3.93:1). Further, let's pretend you've got a 100-tooth spur gear on your car... take 100 (spur gear teeth) divide by 3.93 (target gear ratio) and you get 25.45 (desired pinion size). Now, I've HAD pinions that have a half tooth, but they're really noisy and not terribly efficient, so in this instance you'll have to round up or down. OR if you're REALLY anal retentive you can try a different spur gear and see if it lines up better with your target gear ratio. A 96 tooth spur would give a target pinion size of 24.42. Hmmm...not much better. A 92 tooth would give 23.4. Well, if you're THAT much of a perfectionist I guess you'll have to true your tires down a bit. We could do the math to tell you how much to take off of them, but it's making my head hurt.

Take the lazy way out...measure tire od and plug it into the chart and compare with what your buddy tells you is a good roll-out number. Assuming HE knows what he's doing...

Scottrik

Last edited by Scottrik; 10-26-2005 at 05:40 PM.
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Old 10-26-2005, 05:28 PM   #15194
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Quote:
Originally Posted by Northeast Racer
rollout= (tire diameter x 3.14) / (spur/pinion)

not sure what 3.14 equals in MM though, sorry
Isn't rollout Tire Diameter X 3.14 X Pinion / Spur?
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Old 10-26-2005, 05:33 PM   #15195
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Both equations give the same answer...so I guess both are correct!
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