V3 Track Talion Rebuild

[Forker45]

I‘ve been racing my V3 Talion at a local outdoor track since I picked it up in February 2018.

My skills improved and I realized I was at the limit of the “speed truggy” suspension setup. In February 2019 I installed Kraton shocks, shock towers, & axles/hubs. This dialed the suspension in to a point where I have been pretty competitive for an RTR.

The setup up to this point other than factory Arrma parts:
Kraton Towers & Shocks w Tekno rod ends
Shock Oils: FR 45wt RR 40wt
Shock pistons: FR 8x1.2 RR 8x1.3
Diff Oils: 7/10/4
JX servo: BLS-HV7146MG
SRX-482R (Sanwa clone receiver)
JConcepts Finnisher body
RPM wing mount
RPM Rear Skid
AR727410 droop screws
ARA330554 no-pop Turnbuckle balls
AON28CT01 Hot Racing FR Chassis Brace
AON21N02 Hot Racing Delrin Cap hub nut

Well the truck has taken some punishment and it’s time to replace the chassis plate so I figured this would be a good time to start a build log.

The diff clearance bulge in the chassis pan is gone from the front. ??

 

[Forker45]

As I’ve gotten faster (as well as all the guys in the club with race kit trucks ?) this year, I’ve again reached the limit of the truck’s setup. I know no matter what, the Arrma may be competitive but I’m not going to go much faster than I am at this point due to the weight and limited adjustment vs a race kit.

This has led me down two paths:
1. Get serious and build a Mugen MBX8T-ECO (to go with my MBX8 buggy)

2. Do a mild rebuild on the Arrma to optimize it further to be a good track car for my son as well as a backup on race days.

One thing that I’ve struggled with on the Talion is a combination of difficulty turning under power and snap oversteer. I’ve tried all the adjustments (droop, springs, oil weight, rear hub location, etc) but I think it comes down to the chassis layout. The rearward balance of the V3-V4 Talion layout is good for high speed go-straight stability and bashing but not so good for competition track duty.

Obviously the chassis needs to be addressed and I have decided to get a Kraton chassis to move the weight balance forward. So I guess from here on there’s not much left to call it a Talion. Haha

Below you can see the motor and even the widest part of the chassis is about 1” further forward compared to the Talion.

 

[Forker45]

The Kraton layout vs the MBX8T. The motor mount on the Mugen is about another 1” more forward.

 

[Forker45]

While I’m waiting on a few more parts I did a shock rebuild and replaced the Arrma molded pistons with the machined Delrin 6x1.3 Mugen pistons I had left over from the MBX8T build.

The Mugen piston ID is too small to work with the Arrma shaft so it needs to be drilled out. The Arrma shaft OD measures about 3.38mm at the piston end.

I used the 1/8” portion on a step drill to open up the pistons since it tends to make a more round hole. The Arrma washer OD was large enough to partially shroud some of the holes in the Mugen piston which was a no-go. I scrounged through my parts and found some good washers but they needed the ID opened up.

The fit of the Mugen pistons was much better since they are machined and have minimal, more consistent clearance to the shock body ID so I expect them to perform much better.

 

[SARRT8]

Great build and info. I wish we had a dirt track near me. I would love to run my Talion on a track. I also like your team paint scheme. Thanks again for sharing and good luck this season.

 

[Forker45]

The last of the parts I ordered came in late in the week and I started the teardown & rebuild last night.

It was pretty quick pulling the front and rear clip but slowed way down as I’ve been going through every component completely to inspect, clean, or replace.

If the hinge pins aren’t bent beyond a little straightening I chuck them up in a drill and hit them with a microfiber and some metal polish.

I finished up the rear clip this morning and I got most way through the front but I’m taking a break to enjoy the weather outside.

I went back to the Talion hubs from the Kraton which are significantly wider. The additional offset from the pivot centerline of the hub will actually cause jacking on the inside and dropping on the outside(dependent on caster), effectively causing front roll just by turning the wheels. This could have also been contributing to my funky handling issues on the track. Also reduces unsprung weight which is never a bad thing.

Most of the way through the front, should wrap it up tonight.

 

[Forker45]

I finished up the front clip earlier and I was going to pull everything off the old pan. Unfortunately I stripped out both screws going into the motor mount. So that’s all for today...I will deal with that tomorrow. ?

 

[Forker45]

As soon as I drilled the heads out I thought I made a mistake since there wasn’t enough to grip with pliers. Fortunately the ezout made quick work of it. ??

Finished it all up today in between assembling a backyard pool for the kids.

One thing to note is the big button head droop screws don’t work with the rpm arms. I had swapped them over and noticed even with them run all the way in (for max droop) there still wasn’t enough droop so I had to swap back to the old grub screw style.

Looking forward to trying out the new setup to see how it handles! ??

 

[NeverDun]

I am using big droop screws on my Kratalion, and I thought there was an issue at the rear, because I couldn't get full droop. Turns out I had the left and right arms switched, and the pocket for the droop screw is only on one side. Might be worth a check. Nice build!

 

[Forker45]

I am using big droop screws on my Kratalion, and I thought there was an issue at the rear, because I couldn't get full droop. Turns out I had the left and right arms switched, and the pocket for the droop screw is only on one side. Might be worth a check. Nice build!

Yeah I had them on the right sides. Unfortunately the RPM arms have a little bit different geometry where the screws come through and even with the big screws run all the way in it’s limiting droop more than I want for this application.

Here are some old arms for reference.
RPM on left Arrma on right.
Rears

Fronts

 

[pl9171]

I like the set up.
You talk about oversteer. Interesting. What's your diffs oil management for the dirt?
Thanks for sharing.

 

[Forker45]

I like the set up.
You talk about oversteer. Interesting. What's your diffs oil management for the dirt?
Thanks for sharing.

Thanks! ??
Diff fluids are 7-10-4.

For more background on the handling: when I started running the local track it was a little less technical and usually stayed pretty loamy with medium grip. For me, this led to a driving style of throwing the car into corners and just powering through & steering w throttle. So the rear bias of weight worked ok and the low speed handling ills would be masked by the grip level allowing easy rotation.

Now the track has stepped their game up in the past several months and the layout is more technical in places but still fast in others. The prep results in medium to high grip that blue grooves as the day goes by. This resulted in the Talion becoming a handful because it no longer wanted to controllably oversteer (due to high grip) and in the technical areas the rear weight transfer caused frustrating understeer. Overall these conditions caused me to slow down just to maintain car control in the track conditions.

I think the changes I made should make it easier to drive with confidence but it won’t be a dominator. But that’s why I got the MBX8T-ECO. ?

 

[pl9171]

This resulted in the Talion becoming a handful because it no longer wanted to controllably oversteer (due to high grip) and in the technical areas the rear weight transfer caused frustrating understeer.

Yep, yep...
Kind of same problem... Fix the oversteer problem but the understeer came... Well, the brake and throttle calibration could be an option (Sanwa receiver?) Cornering is so delicate... It's look like nothing, but it's a kind of art! I think that we (and my son) are learning every day.
In our case, on outdoor carpet course, the main problem is always grip, especially on the morning. In the after noon, it's another ball game with dry carpet.
"Throwing the car into corners" is a so true reality... My son is still doing that and the learning process is bit tough! Kids wants to drive like a video game...
For this season, I will try 7-10-7 for the Typhon diffs.
Hurry to test, but the track is now closed. Seems to be the same in Florida?

 

[Forker45]

Well, the brake and throttle calibration could be an option (Sanwa receiver?)

Hurry to test, but the track is now closed. Seems to be the same in Florida?

Yes I have a Sanwa M12S-RS Tx, so there’s a ton of adjustments...but it still seems to me to be a physical/mechanical thing I can’t adjust away. Hence, trying to just optimize it a little bit more with the forward-bias Kraton chassis.
My local track is officially county-owned so it already fell under their closures and now with the statewide stay home order it’s really off limits.

 

[Forker45]

My local track is officially county-owned so it already fell under their closures and now with the statewide stay home order it’s really off limits.

So actually the track is city owned and the city didn’t reopen parks whereas the county has...so the track is still locked down and I haven’t run the rebuilt Talion or the MBX8T yet. ?

 

[jkflow]

Yes, aren't you glad that we have a clear cohesive plan that is somewhat logical...ok to walk around the lake with 50 other people but don't step a foot on that open grass area! Oh well, seems like it's all open again on the 26th.

 

[jeaster12]

New joiner and I wanna do something similar with my talion - so thanks for the great information!

Any idea what of the MUGEN parts fit on the talion as well?

 

[Forker45]

New joiner and I wanna do something similar with my talion - so thanks for the great information!

Any idea what of the MUGEN parts fit on the talion as well?

Good deal, I still haven’t had the chance to run the truck yet. I don’t know for sure what Mugen parts work but I believe there’s quite a bit of discussion around it in the forums.

The Talion will be a good way to get your feet wet and have fun at the track or bash anywhere.

 

[LibertyMKiii]

Great build thread on racing. I wonder if the EXB limited slip diffs would be a good thing for racing. I know in 1:1 racing a good multi-plate LSD makes big differences in the car's exit speed in the turns.

 

[Forker45]

Great build thread on racing. I wonder if the EXB limited slip diffs would be a good thing for racing. I know in 1:1 racing a good multi-plate LSD makes big differences in the car's exit speed in the turns.

Thanks!

I haven’t gone real deep into the EXB diffs but they are definitely interesting. I don’t think they would translate to racing for a few reasons.

I am assuming the design intent is to match differential action of higher viscosity used for most bashers and also maintain consistent performance with heat. Most racers run much lower viscosity in general based on track grip and I don’t think it would be free enough for most racing surfaces.

Also I think that’s a significant amount of weighton a vehicle where every bit counts. Look at the differences between the milled and drilled diff out drives on the Mugen vs Arrma. It would have to be a huge performance advantage to be worth its weight.