Terra Scorcher suspension tuning

[Saito2 8309]

I've been running my mostly stock Terra Scorcher over several terrains including grass, loose surface dirt (ballfield), gravel and mulch. Other than bearings, a Torque Tuned motor, DF03 wheels and Dual Block K tires, its set up box-stock. 

The steering is twitchy and the car is more "on edge" than the understeery Hotshots I run or the more balanced Top Force. This hasn't changed from what I remember when I ran my Thundershot over a decade ago. Added to this is a hefty amount of oversteer. This might all be down to tires, but aside from that are there any suspension tricks I should be looking at? Should I ditch the sway bars? I know when it finally does hookup in a turn suddenly, it tends to grip-roll. Just looking for suggestions from the T-shot chassis experts. Thanks. 

[Ferruz 13542]

@Saito2 While I'm in no way a T-shot chassis expert, I'm happy to share my personal experience with the Terra Scorcher. Not that I did much to it, but since I find it extremely rewarding to drive and free from any faulty behavior (such as being twitchy, oversteer or grip-roll) I guess it's worth a shot -pun intended-

Suspension wise, once the car was built I found the oil shock supplied with the kit to be way too soft, especially in the fronts. I swapped to much stiffer oil, can't remember exactly but I reckon I used some 650/750 cst Associated shock oil in both front and rear shocks. Overall handling felt much better afterwards. 

I also used suspension hinge pins in place of the screw pins on both front and back suspension arms, but I only did it cause they came with the A5 aluminum part. I don't think they make much of a difference tbh. One last thing, I gave the steering some toe out, just a little bit compared to the instructions' settings, I think about 1 mm maybe even less. I think that's about it, the servo saver is still the stock one in my case but it's getting some play by now, so I am going to replace it soon with a high torque one.

I would keep the sway bars, at least for the time being.

I can only speak for myself, but with this setup the car is an absolute pleasure to drive, whether it's on snow, grass, gravel or tarmac. Always balanced and predictable while still keeping that Tamiya character we all like, so not in a boring way. I dare saying it's quite effective too: during our very own Postal Racing events, it never fails to prove competitive and it's  not rare that it grabs the top spot on the podium. 

I hope these little hints will help, although again, I am no expert. 

[DaveBuildsRC 219]

This will help with steering 

https://www.shapeways.com/product/DF3G2VQNT/tamiya-terra-scorcher-bearing-steering-set?optionId=106159107&li=shops

[Andreas W 3016]

Like Ferruz suggests I would go for some toe out in front. To give you a number I have 54mm end to end on the steering rods on both my Terra Scorcher and Thunder Dragon. I have 550 cst oil in front and 400 cst rear (750 cst in the Thunder Dragon front monoshock). I also have internal spacers inside the shocks. On the Terra I have no preload collars in front and only the big ones rear. 

 

My Terra has both roll  bars mounted. Compared with the Thunder Dragon it has a nice off power overstear while cornering,  which is useful on compact, twitchy tracks like we do in the Postal racing. The Thunder Dragon must be flicked to achieve the same effect, which is no success if the speed is low. 

[Twinfan 2314]

I'm not sure toe-out will help if the car already oversteers, that will make the front end even more pointy.

The Terra Scorcher is an older buggy with a higher centre of gravity, so I'd try some slightly firmer shock oil first and see if that helps as less weight transfer and dive should balance the car a little better

[Snappy1 1005]

RC Mart have VQS high caps for $59 US, they have made a huge improvement to my Scorcher

[Saito2 8309]

13 hours ago, Twinfan said:

I'm not sure toe-out will help if the car already oversteers, that will make the front end even more pointy.

That's what I always thought.

I was just debating about the rear sway bar, thinking it might reduce rear grip by making the rear too "rigid". I'll keep it in place for now and look at the suggested shock oils.

I should also swap out the tires just as an experiment to see if that's the source of my troubles. Loose top surfaces might need old school spikes to dig in and find traction.

[Andreas W 3016]

I forgot to mention that narrower front wheels does good and take away some of the on the nose-feel. I run JC Hotshot knock offs in 2,2', which are narrower in front and looks like it has been like that forever. 

[ThunderDragonCy 8974]

Thundershot chassis are very "on the nose". I would suggest unhooking the rear bar for sure. Stiffer oil as suggested above, definitely for the front, or just swap in the piston off the sprue with one less hole. 

Try flipping the B8 to get some rear toe in too. This calms the rear down despite the shortened wheelbase. 

If still struggling, harder front springs, and less grippy front tyres or more grippy rear. Maybe dual block C rear if they are stickier? 

[Saito2 8309]

Still working on trying to make this buggy a bit more neutral. I'm switching to old school oval block tires as they seem to work better on the variety of surfaces I run on (at least they do on my Hotshot cars). 

While installing an alloy A5 part, I was reminded just how very flexible the suspension arms are. Could this contribute to the issues? I always was under the impression that flexible arms (sometimes called "high traction arms") would add steering and lateral grip which might be part of my oversteer/grip roll issues(?). The flex is even worse on the Terra Scorcher as the adjustable upper arms don't give any added support to the lowers. Would installing solid Thundershot uppers be something to try? I normally always run adjustables on these cars just to take the load off the mounts in collisions but the lower arm flex is pretty dramatic. Or, is there something buried in the basic suspension design that gives the Thundershot chassis these characteristics?

[StueyS 49]

I have been running mine recently and have found a couple of things. The rear of the car has very little chassis roll due to a high roll center. I have removed the rear roll bar and lengthened the top link by drilling another hole nearer the rear axle. I am also going to try a softer rear spring. It is also worth flipping the B8 rear mount to get some rear toe in and anti squat. I have also changed the oils to get a better damping balance, although the rear kit pistons (can't remember which ones tbh!) have too much pack with 25wt oil. I'm going to increase the hole size slightly and aim for around 30wt oil.

[StueyS 49]

As the chassis has very little body roll, it can make traction roll worse. Instead of having a more progressive feel it will flip out of nowhere. Removing the roll bars might actually improve the situation.

[Saito2 8309]

Thanks @StueyS. That's exactly how it feels, no progression, just a sudden roll over. Its hard to catch with little/no warning. On slipperier surfaces, it just oversteers and swaps ends. I firmed up the front dampening/removed the rear sway bar and will take your suggestion addressing the rear dampers. Will flipping the rear B8 mount be ok? I pondered it but worried it would angle the suspension pivot pins and put pressure on the the spindly front pin mounts molded into the gearcase. On the other hand, why did Tamiya put that extra set of holes in if it wasn't for that purpose me thinks. 

[ThunderDragonCy 8974]

Flipping the B8 is fine. I also found I preferred mine with solid top arms to reduce the flex a bit. They still give plenty of camber. Maybe try solid front arms and leave the camber links at the back. I really like @StueyS idea about the longer rear camber link. 

[davidwj95 168]

12 hours ago, Saito2 said:

Still working on trying to make this buggy a bit more neutral. I'm switching to old school oval block tires as they seem to work better on the variety of surfaces I run on (at least they do on my Hotshot cars). 

While installing an alloy A5 part, I was reminded just how very flexible the suspension arms are. Could this contribute to the issues? I always was under the impression that flexible arms (sometimes called "high traction arms") would add steering and lateral grip which might be part of my oversteer/grip roll issues(?). The flex is even worse on the Terra Scorcher as the adjustable upper arms don't give any added support to the lowers. Would installing solid Thundershot uppers be something to try? I normally always run adjustables on these cars just to take the load off the mounts in collisions but the lower arm flex is pretty dramatic. Or, is there something buried in the basic suspension design that gives the Thundershot chassis these characteristics?

I've found this thread just as I was looking into the same problem. I took my terra scorcher to a track on Saturday and found it quite difficult to control so I've been looking for ways to make it less oversteery.

 I'd already flipped the b8 part when i built the car so not sure how much difference that made. Today I put 800 cst oil in the front shocks and that has firmed them up a bit. I noticed that the top shock mount actually flexes before there is any compression in the shock absorber. RCMart do an aluminum front shock mount, I was wondering if that might help?

I'm running schumacher block tyres in hard (blue)compound all round, I was also thinking of replacing the rears with soft (yellow) compound.

[Saito2 8309]

54 minutes ago, davidwj95 said:

I noticed that the top shock mount actually flexes before there is any compression in the shock absorber.

Yes!  I had my front end apart last night and was shocked at how flexible the front tower was.

[ThunderDragonCy 8974]

Biggest thing you can do for the balance of one of these cars is different tyres front to rear. I run Schumacher mini spikes or mezzo rear and cut stagger front. Takes a lot of grip out of the front of the car and balances it up. With Schumacher blocks, try yellow rear/blue front. 

[EvilSpike 328]

I'm clearly doing something wrong as my TS just understeers everywhere under power, turns neutrally on part throttle and only oversteers when braking. It gets better when I use the small preload collars on the front end, but then it's dragging it's nose everywhere like a Tory MP over the Westminster bathroom mirrors...

I'm using modern 2.2" wheels, narrower at the front than the rear. Mainly tarmac Absima wheel/tyres on the asphalt but have some Schumacer pinspikes on JC Racing pepperpots too.

[StueyS 49]

Here is a pic of the lengthened upper link. I fitted a new longer turnbuckle 35mm long.

[ThunderDragonCy 8974]

Been through my stock Thunder Dragon thread. It's here if you want to have a read

Highlights pertenant to this thread:

1) I ended up using a way stiffer front spring on the monoshock. Soft touring car spring in the end. 

2) I did the long shock conversion at the rear using Boomerang U parts for the body, and some spacers, but that was on CVA1 style shocks. If the rere is CVA2 just in yellow. Rebuild full length with long eyelets and fit to the top of the narrow tower. My favourite rear suspension setup

[Saito2 8309]

Giving some of these ideas a shot this weekend including @StueyS's camber link mod. Hope to report back my findings.

[Saito2 8309]

Interesting that the Thundershot and Thunder Dragon originally had multiple mounting holes for the upper link on the rear upright while the Terra Scorcher and Fire Dragon only had one set of holes like the re-releases currently all use. I wonder what prompted this, better geometry or durabiltiy issues or ?

[ThunderDragonCy 8974]

9 hours ago, Saito2 said:

Interesting that the Thundershot and Thunder Dragon originally had multiple mounting holes for the upper link on the rear upright while the Terra Scorcher and Fire Dragon only had one set of holes like the re-releases currently all use. I wonder what prompted this, better geometry or durabiltiy issues or ?

The original rear uprights have much higher mounting point whih makes the car even more pointy. The second hole doesn't go all the way through, so I figured it was just something they needed for moulding. I tried using it but had to drill it through. The post Thunder Dragon uprights havd much better geometry. Higher roll centre and much less camber gain. 

[Saito2 8309]

Well, my findings were...that I guess I'm not a fan of this chassis's driving dynamics. Doing some of these mods definitely muted some of the buggy's "pointiness", but it was still present if I push hard enough. There's so much to like about the Thundershot series and I can see why it has its fans, but its not for me I guess.

I ran my Terra Scorcher back to back with a Bigwig of all things, the "top" buggy in each respective 4wd series. The TS was light and lithe. It also did not like a heavy hand at the steering controls. Grab too much steering and the rear end would pivot as if the front end had a spike nailed through it into the ground. Grip roll was reduced but not eliminated. As @ThunderDragonCy and others have proved, there is a lot of potential locked away in this chassis, but it just doesn't suit my driving style.

The Bigwig immediately felt (and looked) bigger and heavier. It also felt much more neutral. I could be totally ham-fisted at the controls, and with the exception of have to slow a bit to reduce understeer (though far better than my Hotshot, which almost requires a brake flick to get the rear end to swing about just to make a respectable turn), I had no issues. Its clear a better driver could extract more from the TS, but that better driver is not me. 

Not including the Avante series, its clear that, in my "Goldilocks" case, the DF01 is probably the buggy that's "just right". The TD4 still calls to me from time to time though.

[Saito2 8309]

As an update, I converted the Terra Scorcher into a Thundershot of sorts. Going to a mono shock in my case reduced some of the oversteer and settled the car in the lumpy grass of my backyard. I think with different tires it might be even better. I was still running the Scorcher's adjustable upper links which may have proven to be an issue. Coming around a turn, I managed to just slightly clip the inner right wheel on my daughter's swing set. It was a light tap and didn't really upset the T-shot's composure, but something on the front end looked "off". Bringing it in, I saw the front inner lower arm pivot had easily pulled out of the hinge pin (mounted to an alloy A5 of course). I don't remember my old T-shot from '05 ever doing that. Perhaps the solid upper arms must be employed to curb this, even if it puts more potential stress of other parts (knuckles, hubs, upper inner arm pivots, etc.) in the event of an impact.