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R/C Tech Forums Thread Wiki: Kyosho Ultima RB6 & RB6.6 Car Thread
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Last edit by: tobamiester
RB6.6 Kyosho America Product Page: http://www.kyoshoamerica.com/ULTIMA-...T_p_24505.html

RB6.6 Manual http://www.kyosho.com/jpn/support/in...A_RB6_6_IM.pdf

RB6.6 Kyosho Youtube https://www.youtube.com/watch?v=vW_sR667utY

MSRP $639 MAP $399.99

-------------------------------
New RB6.6 parts (compared exploded views, prices and links are Kyosho America):

Chassis:
  1. Main chassis - UM731 - $125.99
  2. Side guards - UM732 - $9.99

Battery Holder:
  1. Battery plate - UM733 - $8.99
  2. Battery foam - UM741 - $7.99

Rear Bulkheads:
  1. MM3 and Laydown - UM740 - $9.99
    • MM3 bulkhead
    • Laydown bulkhead
    • Swaybar Holders

3 Gear Transmission (MM and RM):
  1. Transmission - UM734 - $10.99
    • transmission cases
    • spacers
    • caps
    • plastic FR & RR suspension hangers

  2. Gear Cover - UM735 - $6.99

Laydown Transmission (3 and 4 gear possible):
  1. Transmission - UM736 - $10.99
    • transmission cases
    • spacers
    • caps
    • required extra hardware
    • pastic FR suspension hanger

  2. 40T idler - UM737 - $6.99
  3. Motor plate - UM738 - $18.99
  4. Gear cover - UM739 - $6.99

Body:
  1. Blade body - UMB05 - $27.99

Optional Parts:
  1. Lightweigt Blade body - UMB05LW - $31.99
  2. Aluminum FR suspension hanger - UMW705B - $28.99 (may be able to file UMW705 to fit)
  3. Brass FR suspension hanger - UMW725B - $30.99 (looks more different than UMW725..someone confirm?)

Typical Upgrades for new RB6.6 Buyers

UMW701 Aluminum Steering Plate (RB6)
UMW702 Aluminum Crank Arm (RB6)
UMW704-0 V2 Aluminum Rear Hub Set(0/RB6)
UMW705B Aluminum Rear Sus. Holder (RF/RB6.6) or brass UMW725B
UMW707 Aluminum Rear Sus. Holder (RR-Mid)

Nice to have:

UMW723 Aluminum Front Sus Block (Type B/10g/RB6/RT6/SC6).


Aftermarket Parts:

Front Wing: https://www.prolineracing.com/perfor...mount-alum-rb6

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Old 07-31-2013, 10:03 AM   #7756
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Quote:
Originally Posted by Shimmy View Post
No point in buying the Exotek ones now, not unless you're after a more set and forget thing.

The Kyosho hangers are cheaper (only need 3 to have the whole range of adjustment instead of 6) and offer more adjustment options.
Just ordered the RF and RR for rear motor myself.


I have a similar issue with lack of traction on a damp clay track that brings sand through to the top, everyone has the same issue but I just push in the corners heaps and the rear steps out quite easily, on 17.5 blinky.
Using holeshots M3 front and rear, narrow rear hangers, short wheelbase, 30deg kickup +4 caster, stock springs (have losi low freq springs on the way) and 22.5 rear and 25 front with ghia 4 hole, +.5 toe.
Shorty pack towards the front (move it rearwards and very little steering), a full size pack makes the rear swing around much easier.


Track starts to get better when we get into the warmer months though.
Just a guess, but it sounds like you are pushing loose. Your front end snow plows and won't steer and then all of a sudden it bites and whips the rear end out. You need to find the right balance.

I would take out that .5 rear toe and go down some in the overall caster. Also if you are running the 1.3x4 pistons, I think you are really too light on oil. I think I'm running the same pistons at 32.5 fr 27.5 rr with Pink / Gold.
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Last edited by Bob Barry; 07-31-2013 at 12:38 PM.
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Old 07-31-2013, 10:27 AM   #7757
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Originally Posted by motorhead68 View Post
are the stock rb6 arms preferred for low traction over the
flat rb5 arms ???

thanks
I would also like some clarification on what running RB5 arms does to the handling of the car and what conditions they are generally used in.
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Old 07-31-2013, 12:10 PM   #7758
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I would also like some clarification on what running RB5 arms does to the handling of the car and what conditions they are generally used in.
There is no definitive answer, or consensus, on how the RB5 arms change how the RB6 drives.
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Old 07-31-2013, 12:13 PM   #7759
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So many options so many adjustments...
Mind boggling
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Old 07-31-2013, 12:53 PM   #7760
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Thumbs up rb5 arms

I switched to the rb5 521 arms. The cars was instantly a lap faster.

I found that in my experience the arms raise the rear of the car by droop or ride height due to the different mounting of the shock position on the arm.

For me the car was just better with the rb5 arm...
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Old 07-31-2013, 01:34 PM   #7761
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Originally Posted by Johnn27 View Post
I switched to the rb5 521 arms. The cars was instantly a lap faster.

I found that in my experience the arms raise the rear of the car by droop or ride height due to the different mounting of the shock position on the arm.

For me the car was just better with the rb5 arm...
when you switch to the other arms, you are supposed to change the shock bottoms.

I'll put this out there and the other guys can correct me if I'm wrong:

The difference between the two should be one makes your suspension feel more linear and one more progressive due to the gull wing vs flat. I believe it's '6' arms are linear, 5 arms are progressive. Neither is better, they are different. Some guys like one over the other.

My car came with 521-1's on it and I just never changed them. I have the other options, I just didn't get around to switching them.
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Old 07-31-2013, 01:39 PM   #7762
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I have been told that you need to switch the shock bottoms, but which shock bottoms do you switch to?
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Old 07-31-2013, 01:47 PM   #7763
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I have to look at home, I have the 2 ends and the arms ziptied together I'm sure if you do a search in here, it's been covered.
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Old 07-31-2013, 02:37 PM   #7764
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Quote:
Originally Posted by Bob Barry View Post
when you switch to the other arms, you are supposed to change the shock bottoms.

I'll put this out there and the other guys can correct me if I'm wrong:

The difference between the two should be one makes your suspension feel more linear and one more progressive due to the gull wing vs flat. I believe it's '6' arms are linear, 5 arms are progressive. Neither is better, they are different. Some guys like one over the other.

My car came with 521-1's on it and I just never changed them. I have the other options, I just didn't get around to switching them.
Nothing is more progressive or more linear with the shape of the arm. What the "gullwing" shape gives you, is the ability to change the shock mounting position on the arm, without affecting ride height and droop. The holes in the arm line up with the radius circle of the shock, as it pivots from the top mounting location.

On a flat arm, with no gullwing shape, the closer in you mount the hole, the farther down the arm will sit, with everything else being equal. So if you only change the mounting location on the arm, you are actually making more than 1 change at a time. Not only are you changing how soft the shock is, but also ride height, droop, and roll center. You have to then go back and set these settings BACK, in order to only change the arm's leverage on the shock (which is ultimately what you want by changing the lower mounting location).

The kinds of things that are/were/need to be measured, are things like overall length hingpin to hingpin to determine if there is an overall length difference, relative mounting position for the bottom of the shock (which determines leverage against the shocks), if one arm provides a change in wheelbase, and how flexy the material is. One arm might shift the hub slightly more forward or backwards, and one arm might have more or less torsional rigidity over the other, which can subtract or add overall grip).

No difference between the two arms are going to magically give you an entire lap. All the measuring we did last season pretty much showed us that the differences in the arms were actually pretty small. The advantage to the gullwing arm, is simply that changing the lower mounting position only makes 1 change, where as on the flat arm, it changes 3 things. If I remember correctly (somebody correct me if i'm wrong), the flat arms from the RB5 were a tad softer in how easy they are to "twist". (But I could have that backwards)
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Old 07-31-2013, 02:42 PM   #7765
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Quote:
Originally Posted by Bob Barry View Post
when you switch to the other arms, you are supposed to change the shock bottoms.

I'll put this out there and the other guys can correct me if I'm wrong:

The difference between the two should be one makes your suspension feel more linear and one more progressive due to the gull wing vs flat. I believe it's '6' arms are linear, 5 arms are progressive. Neither is better, they are different. Some guys like one over the other.

My car came with 521-1's on it and I just never changed them. I have the other options, I just didn't get around to switching them.
I changed to the medium shock bottoms I think, but I know I changed them and went shorter
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Old 07-31-2013, 03:08 PM   #7766
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I started with the Gull, after some time went to the 521-1. After running these for awhile now, the car just hasn't felt as fast as it did with the Gull arms. I asked Tebo about the difference and how it impacts the car. He said "the gull can carry corner speed better, where the 521-1 square up jumps better". I was running mod when I switched and to me the Gull seem better in a 17.5 class and maybe the 521-1 arms work better in mod.
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Old 07-31-2013, 04:12 PM   #7767
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Quote:
Originally Posted by steam View Post
I started with the Gull, after some time went to the 521-1. After running these for awhile now, the car just hasn't felt as fast as it did with the Gull arms. I asked Tebo about the difference and how it impacts the car. He said "the gull can carry corner speed better, where the 521-1 square up jumps better". I was running mod when I switched and to me the Gull seem better in a 17.5 class and maybe the 521-1 arms work better in mod.
well if he said the gull wing carry corner speed better then thats what u would want for stock unless you have a hard time sqauring up jumps.
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Old 07-31-2013, 05:55 PM   #7768
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Originally Posted by Cpt.America View Post
Nothing is more progressive or more linear with the shape of the arm. What the "gullwing" shape gives you, is the ability to change the shock mounting position on the arm, without affecting ride height and droop. The holes in the arm line up with the radius circle of the shock, as it pivots from the top mounting location.

On a flat arm, with no gullwing shape, the closer in you mount the hole, the farther down the arm will sit, with everything else being equal. So if you only change the mounting location on the arm, you are actually making more than 1 change at a time. Not only are you changing how soft the shock is, but also ride height, droop, and roll center. You have to then go back and set these settings BACK, in order to only change the arm's leverage on the shock (which is ultimately what you want by changing the lower mounting location).

The kinds of things that are/were/need to be measured, are things like overall length hingpin to hingpin to determine if there is an overall length difference, relative mounting position for the bottom of the shock (which determines leverage against the shocks), if one arm provides a change in wheelbase, and how flexy the material is. One arm might shift the hub slightly more forward or backwards, and one arm might have more or less torsional rigidity over the other, which can subtract or add overall grip).

No difference between the two arms are going to magically give you an entire lap. All the measuring we did last season pretty much showed us that the differences in the arms were actually pretty small. The advantage to the gullwing arm, is simply that changing the lower mounting position only makes 1 change, where as on the flat arm, it changes 3 things. If I remember correctly (somebody correct me if i'm wrong), the flat arms from the RB5 were a tad softer in how easy they are to "twist". (But I could have that backwards)
And this is why he is the man and I am but a lowly peon

Seriously though, great info. Helped me. Hope it helps others.
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Old 07-31-2013, 08:08 PM   #7769
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Just a guess, but it sounds like you are pushing loose. Your front end snow plows and won't steer and then all of a sudden it bites and whips the rear end out. You need to find the right balance.

I would take out that .5 rear toe and go down some in the overall caster. Also if you are running the 1.3x4 pistons, I think you are really too light on oil. I think I'm running the same pistons at 32.5 fr 27.5 rr with Pink / Gold.
Thanks.

It doesn't really suddenly bite but just gradually starts turning more.
The rear whips out just as I'm trying to get back onto the power or lining up the exit.

I did have 25deg caster but found the steering was worse, especially off power (was virtually none).
I havnt measured the pistons (I bought the buggy 2nd hand), I realise I'm a bit on the light side for oil, I was curious to see how much difference there was, there was a bit, but nothing amazing, doesn't bottom out that much but does more noticeably than what was in there.
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Old 07-31-2013, 08:23 PM   #7770
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From my experience and it goes with what Tebo said, the flat arms will keep the car more flat while the gullwings had the car still leaning over when I was ready to power out of the corner. So for a loose track the gullwing is probably better since it'll give more traction. While on a higher bite track the flat arms will have the car square up faster out of corners.
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