Kyosho ST-RR conversion

[rootar]

the thicker the oil the longer it takes the center diff unload to the front tires on takeoff, nitros can get away with running a thicker center fuild because they have a clutch and not near as much "snap" as brushless i would saygo light for track use 7-10 to make it handle good and go heavy as you want bashing because wheelies are part of it.

[Gee]

I'm running a mixed set of shocks on mine. I have Jamming BB in the rear and Kyoshos in the front. As for the hole sizes I don't remember which ones. I had been e-bay shopping for BB for a long time. Had a hard time spending what they wanted at the LHS for a new set. WOW. I was pretty excited when the BB's showed up in the mail. I just put them together without thinking which size I should install in them. What a difference the big bores made in how it handles. It was worth the wait.

I need to tear into my diffs and check them out. Let us know what you think of the 30k in the center.


Rootar so what are you running/recommending for a electric? Starting in the front 7/10/3? I am running a nitro at this time so I should go with a heavier center?

[George16]

Well, the rain finally stopped earliear but the track is so wet and muddy. So I was forced to do the initial run on pavement while the track is drying up. My initial impression is WOW!!! The truck rides like it's on rails. I thought it will behave different compared to the nitro version (friend's truck) due to the added weight of the batteries but I was wrong. Turns on a dime and I can actually drive it at high speeds in a straight line without my hands on the steering wheel :applause: :applause: :applause: . I like it so far. I'll give more feedback once I run it on the track and do some jumps. Main concern I have is the chassis flex especially in the rear end.

Here's a couple of videos:




Temps are as follows:
Air temp - 48*F
ESC - 99*F
Batteries - 90*F
Motor -102*F

It seems too good to be true for the temps until I realized that there is a big hole on the front windshield of the body so there's a lot of airflow. The MMM's fan didn't even come on(it did during calibration and initial setup).

My setup:
Batteries - 5S 5000mah Neu lipos (I might go 4S and gear up according for 40 mph)
Pinion - 15T
Spur - 50T

Diff oils:
Front - 7K
Center - 30K
Rear - 3K

Shocks (16mm bigbores):
Front - 50wt Losi shock oil
Rear -50 wt losi

[George16]

Here's another video. The track still has a lot of standing water so no dice in jumping the truck.

[lstmuggy]

that kyosho looks sweet

[rschoi_75]

Dang that's a nice track!

Your truggy looks awesome!

[Shark413]

Nice, looking conversion. Yeah I have been running my ST-RR conversion for some time now and love it. One of the best handling truggies I have every driven and I attribute some of this handling to the chassis flex. Most buggies/truggies are designed to flex, that is why the braces stop short and attach to the middle of the chassis (and not to each other). Without this flex it would feel like a brick. I use the King headz braces only because I was worried the stock Kyosho brace might pop off (held on with a large ballend) and so far they are working great. So don't worry about the flex, it is a good thing.

[George16]

Originally Posted by Shark413

Nice, looking conversion. Yeah I have been running my ST-RR conversion for some time now and love it. One of the best handling truggies I have every driven and I attribute some of this handling to the chassis flex. Most buggies/truggies are designed to flex, that is why the braces stop short and attach to the middle of the chassis (and not to each other). Without this flex it would feel like a brick. I use the King headz braces only because I was worried the stock Kyosho brace might pop off (held on with a large ballend) and so far they are working great. So don't worry about the flex, it is a good thing.

Great that you chimed in Shark. I just ordered the rear Kingheadz brace and rear mount from Amain since Kingheadz is so slow in replying to my question asking them if they ship to a military address. I was certainly worried about the flex (this is my first "real" truggy) but felt reassured now.

What's your current diff oil and suspension setup? Thanks again.


rschoi_75, we built that track inside the navy base here in Yokosuka Japan last year. The background is the mouth of Tokyo Bay and it gets windy and cold especially now.

[Shark413]

George16, I am running 7K, 10K, 3K in my diffs and that setup works well for the short technical track I run at. One thing you have to keep an eye on are your diffs, the ST-RR uses spiral gears and they are very sensitive to shimming. The torque, heavy truck, bigger tire contact patch, plus the fact the neu motor puts out so much torque it can shred diffs bigtime. I destroyed my center diff one week and then the front blew the next week. The center blew out because I switched to an aluminum diff cup that was a little out of spec, the front blew out because the inner pinion bearing let loose throwing the mesh off. I have switched back to the stock Kyosho diff cup for the center with harden HB gears and rebuilt and reshimmed the front diff (and replaced all the bearings). Don't get me wrong, the ST-RR is a durable truck, I have been running it hard for 5+ months and these are the first diffs I have blown. Nothing else major has broken, but I did wear out the front bearing in my Neu a few months ago (replaced by Neu).

[George16]

Shark413, I have about 5 sets of Ofna diffs/gears that I can throw in there if the stock ones get sheared. With that said, I will also have to change my spur/pinion since the ofna diff I have are from the buggies which use a 43/13 ring gear/pinion.

Well see how the stock goes. I'll just have to change back to 10K for the center since I put 30K in there. I like how it's setup now but there is always room for improvement.

Thanks again.

Edit-I also installed the HB hardened gears in the CD.

[Shark413]

George16, regarding the suspension, were pretty close. I am using Kyosho BB with the blue springs (stiff) and 55wt in front and 50wt (associated) in the rear. Using about 5mm preload in the rear and 3mm in the front. Arms parallel to the ground after bouncing the suspension. At my track the biggest jump is a 3 foot triple, the rest of the track is pretty smooth and the suspension works well for me.

[George16]

The water finally dried out from the track yesterday so I did some laps to test the truck. It was sunny but very, very windy. My son had a hard time filming due to the strong winds. I didn't put any background music so everyone can hear the howling wind.

Temps after a 15 minute run:
ESC- 104*F
Motor - 132*F
Batteries - 100*F

air temp - 60*F but felt like low 50's.



I'll be changing the center diff oil to 10K instead of the 30K I have in there.

[George16]

Just installed some upgrade parts.







Dace Mfg. 17mm hex:


I had a chance to ran it last Friday and Sunday when the air temp was about 57*F and 68*F respectively and wasn't pleased with the results.

Here's my gearing and temps:

ST-RR
50/15, 5S

Air temp was 57*F
ESC – 104
Motor – 131
Batteries – 100

ST-RR
50/16, 5S

Air temp was 68*F
ESC – 112
Motor – 170
Batteries – 104

I'm going to try 48/16 this weekend and see if the motor temp drops. Both were continuous 10-12 minute runs.

I went up to 16T pinion based on this:
Hot motor, cool controller, cool batteries = undergeared

[Jason]

whats gearing do you recommend guys for 2370kv motor on 4s @ 14.8v ?

[George16]

What's your target top speed? If I'm going to run 4S, I'll start with a 46/13 gearing.