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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 08-05-2014, 10:59 AM   #41056
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Wow, ran, and won, on a surface hot enough to cook a steak on and didn't even puff the battery. That is impressive.
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Old 08-05-2014, 02:04 PM   #41057
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Quote:
Originally Posted by EDWARD2003 View Post
RedBullFixx - Thanks . I really do appreciate a professional opinion on this topic, but that's all that he's provided. There wasn't any reasoning behind it nor did he comment on the differences in handling.

But really...Why do 1/12th designers disregard achieving perfect rear pod balance? Doesn't make much sense now does it.

Maybe, I'm just speculating here... The distance of 3 mm he used in his test was probably too much of an offset. With this offset and the weight of the motor could of caused the screws to generate elastic characteristics (spring effect). This is all just speculation.
Speculation by an expert is sometimes all you need. Theory is fine, but it doesn't always work in practice!

Quote:
Originally Posted by I)arkness View Post
how does balancing of the main chassis work out with non balanced rear pod, as i thought id gotten mine pretty well even left to right with balancing pins, but when i used a corner weight rc scale station i was much heavier on left side, even when it was perfectly tweaked still was out.
is it possible to get it perfectly balanced to some degree??
Quote:
Originally Posted by RedBullFiXX View Post
ihmo
I would not recommend balancing chassis electronics with the rear pod connected, unless the rear pod is also balanced, which could be seen as pushing the ball up-hill to no benefit

Weight on the pod is spread across a solid axle, weight on the chassis is not

Any imbalance of the rear pod will further skew chassis balance, if one were to corner weight the car as a whole, or on balance pins

I've given up on pod balance, now preferring to just have the least weight on the pod as possible

Choose the tires your club mates run to start
Yokomo-3Racing offer a nice portable truer at a fair price
The issue with a 12th car is that it is a racing chassis with a hinge in the middle. Much of one's perceived wisdom about weight distribution therefore goes out of the window.

RedBull - thanks firstly for finding Mike's original post. After ten frustrating minutes I couldn't! Thanks secondly for pointing out the key difference between balancing the front and rear of the car, and how it should (not!) be done.

Each end of the car is sitting on three points. At the rear, those three points are solidly connected through the axle and the bottom pod plate. Generally speaking, all the weight inside those three points (the two tyres and the centre pivot) will even out over the there points giving an even weight distribution across all three. the comments about dynamic imbalance still apply, but balancing the car is a static event, not a dynamic one.

The situation with the main chassis is different. The three points are disconnected because the front tyres are sitting on two springs independently pivoted from the main chassis. The weight in the chassis will unevenly distribute itself across the front tyres because each can accommodate a different weight as it pivots independently from the main chassis.

If you take the pod off the car and balance the main chassis with all its elements fitted you will evenly distribute its load across the front axle. Ignore the rear pod - within the limits of the different motors' weight distribution the weight will be pretty much even across the rear tyres.

Now reconnect the chassis to the pod and set it up on the tweak screws using whatever method takes your fancy - tweak station or coin-drop test. If you do that and then put it on the corner-weight balances, you will find it is within a couple of percent from side to side on the front wheels. That's what I do and I get within 1% most of the time.

For this to be accurate you need tyre sizes exactly the same on each side of each axle. As they never are, there is always some imbalance. You don't stop halfway through a race to swop your tyres over, so don't sweat the chassis balance too much on the bench. HTH
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Old 08-05-2014, 03:27 PM   #41058
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Hi
Couple of questions.
How do you calculate the roll centre of the rear pod?
How does the centre of gravity of the rear pod affect the roll if it is off centre?
Is the system really connected by a pivot, this sounds silly but if the the side springs are sufficiently compressed i would say its no longer a freely moving pivot.
Interested in your views.
Marc
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Old 08-06-2014, 08:40 AM   #41059
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Can 1/12 pan car perform on concrete ?
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Old 08-06-2014, 09:42 AM   #41060
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For all the guys running the rc12r5.2 chassis , there is a transverse conversion made by reflex racing that uses a oring to hold the lipo in like a crc and includes a new shock mount that allows you to run multiple shock lengths i have been running it for about 2 weeks and it is great

http://www.reflexracing.net/RSD-AE-1...it_p_2367.html
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Old 08-06-2014, 11:14 AM   #41061
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Quote:
Originally Posted by cmunro View Post
For all the guys running the rc12r5.2 chassis , there is a transverse conversion made by reflex racing that uses a oring to hold the lipo in like a crc and includes a new shock mount that allows you to run multiple shock lengths i have been running it for about 2 weeks and it is great

http://www.reflexracing.net/RSD-AE-1...it_p_2367.html
Do you have any photos of your car with the conversion?
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Old 08-06-2014, 01:32 PM   #41062
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Quote:
Originally Posted by marcvanderzon View Post
Hi
Couple of questions.
How do you calculate the roll centre of the rear pod?
How does the centre of gravity of the rear pod affect the roll if it is off centre?
Is the system really connected by a pivot, this sounds silly but if the the side springs are sufficiently compressed i would say its no longer a freely moving pivot.
Interested in your views.
Marc
Hi Marc, thanks for your interest.

To all intents and purposes, the rear roll centre is the height of the rear pivot ball. Arguably the diameter of the rear tyres plays a role in this, but for all practical purposes the height of the ball is it.

You can buy a set of pivot balls that are reduced in height by about 0.5mm (but you must lower the plastic 'bridge' by the same amount, and I've never seen them sold!) to give more rear grip. That works well on low-grip surfaces.

The roll is not affected by the rear pod weight being off centre. The rear pod doesn't roll, only the chassis does. Remember the pivot in the middle of the chassis? It's there to allow the rear pod to stay flat while the main chassis rolls as the weight transfers.

That's not to say there isn't weight transfer across the rear axle; there is. That's why we said in earlier posts that dynamically it's a different ball game. That also applies to the diff, which has most of its weight offset to one side - the drive side. If we were really worried about weight distribution in the rear pod, why has no one come up with a heavier left side drive to offset the heavier diff side drive. Answer, because it doesn't matter statically! And dynamically, what we have works. It ain't broke, so don't fix it!

Don't confuse the free movement of the pivot with a mechanical stop that prevents it moving beyond a certain point - when the springs are fully compressed. During racing the chassis does't roll more than 2mm (otherwise it would touch down all the time) and that is limited more by the front springs than the rear. At that point the springs are not compressed and there is no mechanical stop in play. The chassis rolls freely from side to side as the car moves from one corner to the other.

When I am asked to help people get their car to handle, nine times out of ten the problem is a rear pivot wrongly set and preventing free roll of the main chassis. The pivot must not have any resistance or 'steps' in its movement. I usually leave about .005" of vertical play in the setting to allow for the fact that the side links are pulling the rear pod forwards and backwards when they move through their arc. HTH
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Old 08-06-2014, 01:54 PM   #41063
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Good stuff as always Mr. SlowerOne

Tamiya went to the extent of designing a left rear Counterweight for their F1, it floats freely on bearings

Jury is out on results of that experiment...


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Old 08-06-2014, 01:59 PM   #41064
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Hi slowerone

Thanks for the great answer. As an engineer I am fascinated with these great little cars. I guess the flex of the rim and the compression of the tire create some room for roll but it would be marginal. The point about the pivot being the roll centre in hind sight is obvious but I never though of it in that way. I now understand why the freedom of movement is so important, guess its time for a rebuild

Marc
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Old 08-06-2014, 02:05 PM   #41065
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Quote:
Originally Posted by RacinJ View Post
Do you have any photos of your car with the conversion?
I'll post some pictures by tonight. We did the development on Cmunro's car. I really like how it drives. It is very forgiving and incredibly smooth.
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Old 08-06-2014, 02:54 PM   #41066
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Quote:
Originally Posted by SlowerOne View Post

That's not to say there isn't weight transfer across the rear axle; there is. That's why we said in earlier posts that dynamically it's a different ball game. That also applies to the diff, which has most of its weight offset to one side - the drive side. If we were really worried about weight distribution in the rear pod, why has no one come up with a heavier left side drive to offset the heavier diff side drive. Answer, because it doesn't matter statically! And dynamically, what we have works. It ain't broke, so don't fix it!
To follow on with this and a post of yours quoted further up the page from a different thread.

In a static mode the pod weight distribution will affect the weight on each tyre, broken down to it's simplest form the pod by itself is a simply supported beam (the tyres being the supports), now assuming for a moment the motor is the only thing that has any weight.
If you put the motor directly over one tyre then that tyre has 100% of the load.
Put in the centre each tyre gets 50% of the load.
1/4 of the way across, one gets 75% the other gets 25%.
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Old 08-06-2014, 04:19 PM   #41067
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Could you please clarify the last sentence?

Are you saying you leave the plastic pivot housing that bolts to the chassis slightly loose so it can move about slightly?



Quote:
Originally Posted by SlowerOne View Post
Hi Marc, thanks for your interest.

To all intents and purposes, the rear roll centre is the height of the rear pivot ball. Arguably the diameter of the rear tyres plays a role in this, but for all practical purposes the height of the ball is it.

You can buy a set of pivot balls that are reduced in height by about 0.5mm (but you must lower the plastic 'bridge' by the same amount, and I've never seen them sold!) to give more rear grip. That works well on low-grip surfaces.

The roll is not affected by the rear pod weight being off centre. The rear pod doesn't roll, only the chassis does. Remember the pivot in the middle of the chassis? It's there to allow the rear pod to stay flat while the main chassis rolls as the weight transfers.

That's not to say there isn't weight transfer across the rear axle; there is. That's why we said in earlier posts that dynamically it's a different ball game. That also applies to the diff, which has most of its weight offset to one side - the drive side. If we were really worried about weight distribution in the rear pod, why has no one come up with a heavier left side drive to offset the heavier diff side drive. Answer, because it doesn't matter statically! And dynamically, what we have works. It ain't broke, so don't fix it!

Don't confuse the free movement of the pivot with a mechanical stop that prevents it moving beyond a certain point - when the springs are fully compressed. During racing the chassis does't roll more than 2mm (otherwise it would touch down all the time) and that is limited more by the front springs than the rear. At that point the springs are not compressed and there is no mechanical stop in play. The chassis rolls freely from side to side as the car moves from one corner to the other.

When I am asked to help people get their car to handle, nine times out of ten the problem is a rear pivot wrongly set and preventing free roll of the main chassis. The pivot must not have any resistance or 'steps' in its movement. I usually leave about .005" of vertical play in the setting to allow for the fact that the side links are pulling the rear pod forwards and backwards when they move through their arc. HTH
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Old 08-06-2014, 05:09 PM   #41068
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Quote:
Originally Posted by RacinJ View Post
Do you have any photos of your car with the conversion?
here are the pictures of Charlie's Car:




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Old 08-06-2014, 06:22 PM   #41069
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Since the rear pod runs on a solid axle and has no suspension.

One could say that:

A - The rear pod influences on the main chassis' handling is marginal? It only contributes to forward and aft weight transfer to the main chassis via the central damper?

B - The main chassis is the main component where the majority of the suspension is at work. Front springs, central damper, and side springs.

So really, when it comes to tuning a 1/12th, we are finding a balance between the front and rear end of the main chassis?

Sorry, it all sounds silly, but I'm just trying to express my ideas to further understand this class.
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Old 08-06-2014, 11:24 PM   #41070
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I'm shopping for a 17.5 to run with 1s on asphalt. What do you guys recommend?
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