My experience running a TD-2 on an indoor carpet track

[CptMookie 55]

Disclaimer. I have never raced before and prior to this, I have been on a track two or three times.

I have been to drift tracks many of times, and I am pretty happy with my results, but buggy racing is where my interests has always been. So when news come out that an indoor track was opening up twenty minutes away from where I live, broke my bank and bought a TD-2+mods.

This car (and its four wheel brother) have always been on my wish list. I have sought after this car for so long that I actually bought four or revive-rc's Avante bodies in advance sometime last summer. Here is where I want to post updates and hopefully receive build tips and advice. Believe me though, I am consuming as much as I possibly can already, and this community has been such a huge well of knowledge. So yeah. Thanks to everyone here. 

Anyways. Here is the build and my thoughts so far.

1. TD-2 Chassis
2. Revive-rc polycarbonate body.
3. Jconcepts Drop Step rears (preglued)
4. Jconcepts Swaggers (preglued)
5. Motiv MC4 17.5.
   1. I tried the Tamiya 54894 17.5TBLM-02s. This motor just cannot get up to the speed I needed to clear the jumps. So I took an old motor from my Kyosho RB7.
6. Savox 2265MG.
7. Radiomaster MT12 ESLR version TX and RX.
8. Hobbywing XR10 Stock Spec ESC.

These are the mods I have on the car:

1. Slipper clutch
2. I am using the TB03 .06 mod spur. This will not fit onto the slipper unless you use a specific bearing that took me a week to get shipped to me. The bearing number is SR166-2RS. 
3. Matching pitch pinions (I have tried 26 and 29 - I prefer the 26) FDR = (64 / 26) x 2.6 = 6.4 fdr
4. Aluminum diff nut
5. TRF buggy shocks
   1. The front ones are too long for the TD2. So currently I am using a yeah racing set for the fronts.
   2. I ordered front and rear big bore that state they fit.
6. XV-01 rear hubs.
   1. You need this to fit standard competition wheels with standard offset.
7. DB-01 universal shafts.
   1. You need this to replace the TD2 outdrives. You will also need a large spacer so that the pins clear the hole. I use a large o-ring.
8. I have Zee shorty packs that are a wee bit large for the battery slot. So I cut some material out near the bullet connections. (eek I know. I also hate dremeling out plastic on a new chassis)
   1. I also removed the top bracing over the battery area. I needed to do that so that I could repurpose the holes for a battery retaining system. I am looking for alternative better ways to retain the Zee shorty pack. I do not have alternatives and I invested way too much on this build alone, and I don't want to waste a two set of the listed batteries.
9. The adjustable rear arm bracket that allows for more toe adjustment.

I think that is it.. There will definitely be some more adjustments, but for the most part I think this is a good baseline.

[CptMookie 55]

Off the bat, here are some things that were identified (the guys at the track actually identified these for the most part).

1. The suspension is too stiff. Need different oils or other suspension, I am hopeful that the big bore will address this (and the shock kit I bought separately)
2. So if you use the yeah racing XV-01 rear hubs like I did, be aware that those already add toe in. This accompanied with my rear adjustable mount, meant that it was WAY toed in. Need to fix that.
3. I need to find a way to mount the battery better. Currently its fine, and isn't going anywhere. However, it does utilize a hole in the chassis in a way that is not intended.
4. Also I do not have an answer for this issue, but I hope that someone does. The steering is... off. I reset my endpoints, and zeroed it as best I could on the trims and physical arm. However it finds a way to drift one way or another every now and then. I think it has to do with the chassis slop. Or maybe I took one too many hits and it is starting to cause some slop. :shrug:
5. The slipper clutch needs to be as tight as possible on a carpet track. A lot of traction meant it was barking at me all the way until I had it pretty much maximum tightness.
6. The ball diff on a carpet track is going to be replaced. The guys at the track recommended a gear diff because the traction here on carpet is too much for a ball diff. I ordered the Yeah Racing one, and we shall see...
7. Also I ordered a set of rear DB-01 suspension lower arms. This is because if you do the hub mod like I did (XV-01 hubs and DB-01 out drives) you will need to dremel a ton of material out so that the shafts fit. I tried the RB7 (not stock version) and those outdrives did not work as well as the DB-01 out drives.

[CptMookie 55]

Also note: The shocks seen in the pictures is taken before a lot of these mods were applied. Thats why you may see that the rear shocks are not the tamiya trf buggy ones.

[River19 65]

Cool stuff.

I race carpet off road weekly along with clay with 2 different cars of the same model (TLRs) and the guys at the track have you headed in the right direction on the diff....geared is standard for high traction carpet.

The steering slop.....are you using any sort of Tamiya "servo saver"?  If so......I would consider ditching that for a direct solid arm ASAP.

Suspension.....start with oils or piston changes (the internal disks in the shock).....perhaps some pistons with additional holes for good flow might help.  You could also think about springs.

What is your ride height set at? Usually we are running 15-18mm ride height F/R, lower if we can get away with it depending on the jumps etc.

How was traction? Usually traction is very high and if anything you are trying to avoid traction rolling in higher speed corners.

 

[CptMookie 55]

2 hours ago, River19 said:

Cool stuff.

I race carpet off road weekly along with clay with 2 different cars of the same model (TLRs) and the guys at the track have you headed in the right direction on the diff....geared is standard for high traction carpet.

The steering slop.....are you using any sort of Tamiya "servo saver"?  If so......I would consider ditching that for a direct solid arm ASAP.

Suspension.....start with oils or piston changes (the internal disks in the shock).....perhaps some pistons with additional holes for good flow might help.  You could also think about springs.

What is your ride height set at? Usually we are running 15-18mm ride height F/R, lower if we can get away with it depending on the jumps etc.

How was traction? Usually traction is very high and if anything you are trying to avoid traction rolling in higher speed corners.

 

All fantastic stuff right here. Thanks!

Currently I am running a solid servo horn, and just got done adjusting some things. I found that I think I missed some bushings in the front arms where the arms meet the chassis. That's causing some slop. 

As for the suspension in the front, I used the softest springs and the softest oil I had (Tamiya yellow soft). You are right on the money what I'm gonna do next. I need to change the piston heads.

I don't have much plans to deal with corner traction other than gluing the side walls. I also plan on upgrading with some anti roll bars.

My ride height is 24mm.... Is that bad?

[River19 65]

We're talking racing toy cars so there is no "bad" per se...... :-)

It depends on the car, driving style and goals.  24mm may be kinda high assuming a high level of grip on the carpet as it raises the roll center of the car.

The anti-roll bars are a great idea and I was going to mention those but I didn't know if they were available for the car or not.

Once you address the things you can it just comes down to driving what you have.  While a great car setup is ideal, driving skills are the biggest element.  I have spent several "practice" sessions at the tracks on off days when there is crappy weather and it makes sense to be indoors.......all in the name of improving my driving as that is the limiting factor in results not the car setup.  Even when I finish dead last, I still have fun.

[Howards 593]

You can use a ball diff on carpet - it just needs to be tight so it won’t slip - but this might mean you don’t get the diff action you need. 
 

If it’s still barking with the slipper done up tight then it might be the diff slipping. You can check for this by holding the spur and one of the drive wheels whilst forcibly turning the other drive wheel. If the slipper is slipping you’ll see the slipper shaft turn with a smooth action . If the diff slips first you’ll feel a grittier action and the slipper shaft will remain still. 

[CptMookie 55]

4 hours ago, River19 said:

We're talking racing toy cars so there is no "bad" per se...... :-)

It depends on the car, driving style and goals.  24mm may be kinda high assuming a high level of grip on the carpet as it raises the roll center of the car.

The anti-roll bars are a great idea and I was going to mention those but I didn't know if they were available for the car or not.

Once you address the things you can it just comes down to driving what you have.  While a great car setup is ideal, driving skills are the biggest element.  I have spent several "practice" sessions at the tracks on off days when there is crappy weather and it makes sense to be indoors.......all in the name of improving my driving as that is the limiting factor in results not the car setup.  Even when I finish dead last, I still have fun.

I managed to get it to 16/17mm so I'm pretty happy with that for now. The next thing is to soften the suspension. I'm gonna buy the lightest three weights at my local drift track and I'm gonna bore out some of the piston hole material (and I'm hopeful to knock it out today).

I love the idea of racing this thing against some mugens and TAs. That's what's at my track so far. It sounds like a blast.

[CptMookie 55]

1 hour ago, Howards said:

You can use a ball diff on carpet - it just needs to be tight so it won’t slip - but this might mean you don’t get the diff action you need. 
 

If it’s still barking with the slipper done up tight then it might be the diff slipping. You can check for this by holding the spur and one of the drive wheels whilst forcibly turning the other drive wheel. If the slipper is slipping you’ll see the slipper shaft turn with a smooth action . If the diff slips first you’ll feel a grittier action and the slipper shaft will remain still. 

Oh 100 percent. I am going to run some laps with both (when the gear one comes in) and see if there's a huge difference. I don't anticipate much difference. 😎

[Howards 593]

Would be interested to know if you tweak the front sus so that the chassis can bottom out. Bit weird that the TD2 will bottom out the shocks before the chassis. The TD4 doesn’t do this with the 4wd shock arrangement.

[CptMookie 55]

12 hours ago, Howards said:

Would be interested to know if you tweak the front sus so that the chassis can bottom out. Bit weird that the TD2 will bottom out the shocks before the chassis. The TD4 doesn’t do this with the 4wd shock arrangement.

I noticed that as well. It's a strange design choice and I almost think it's just an oversight?

Anywho, I am messing with the suspension and I think the front is too light for any meaningful adjustments to be made. I'm thinking weights? Or boring out the pistons to soften the suspension? I've already tried soft springs and oil.

[BloodClod 366]

On 5/5/2024 at 12:46 PM, CptMookie said:

I noticed that as well. It's a strange design choice and I almost think it's just an oversight?

Anywho, I am messing with the suspension and I think the front is too light for any meaningful adjustments to be made. I'm thinking weights? Or boring out the pistons to soften the suspension? I've already tried soft springs and oil.

Enjoyed reading this thread. 

I'd recommend adding weights to the front end, from my experience it will help a lot for high grip running. The TD2 front end is very light - good for stability on lower grip surfaces, but I've found it makes it hard to tune the suspension when you need to.

[Losi XXT-CR 292]

On 5/4/2024 at 2:22 AM, River19 said:

Cool stuff.

I race carpet off road weekly along with clay with 2 different cars of the same model (TLRs) and the guys at the track have you headed in the right direction on the diff....geared is standard for high traction carpet.

Can I ask what is the issue with the ball diff? Is it that the diff centre can spin?

Back in the day we all ran ball diffs carpet racing. I don’t recall them being an issue.l if setup and adjusted properly (this wasn’t Tamiya cars though). I know motors and batteries have changed. But we used to run some fairly pokey setups still. 

[River19 65]

34 minutes ago, Losi XXT-CR said:

Can I ask what is the issue with the ball diff? Is it that the diff centre can spin?

Back in the day we all ran ball diffs carpet racing. I don’t recall them being an issue.l if setup and adjusted properly (this wasn’t Tamiya cars though). I know motors and batteries have changed. But we used to run some fairly pokey setups still. 

My understanding and the basic overall vibe from other drivers is that ball diffs allow slippage by design and on lower traction surfaces like clay and loose dirt etc. that slippage and very linear power delivery is a bonus to keep things under control and keeping things straight.  To get a ball diff to minimize slippage and lay down the power aggressively in a high traction application like carpet, you would run that ball diff really really tight and at that point it becomes more hassle form a maintenance standpoint than it is worth.  

A geared diff on carpet lays down the power much more aggressively as the last thing you really need is slippage as there is no danger of the rear end stepping out under power due to the high level of traction.

A ball diff can certainly be run on carpet, but you aren't gaining anything from what a ball diff does well and in fact it probably is hurting acceleration from corners and hurting lap times.

YMMV

[Losi XXT-CR 292]

15 hours ago, River19 said:

My understanding and the basic overall vibe from other drivers is that ball diffs allow slippage by design and on lower traction surfaces like clay and loose dirt etc. that slippage and very linear power delivery is a bonus to keep things under control and keeping things straight.  To get a ball diff to minimize slippage and lay down the power aggressively in a high traction application like carpet, you would run that ball diff really really tight and at that point it becomes more hassle form a maintenance standpoint than it is worth.  

A geared diff on carpet lays down the power much more aggressively as the last thing you really need is slippage as there is no danger of the rear end stepping out under power due to the high level of traction.

A ball diff can certainly be run on carpet, but you aren't gaining anything from what a ball diff does well and in fact it probably is hurting acceleration from corners and hurting lap times.

YMMV

Thanks. I'm still not 100% convinced on this though. A ball diffs main purpose is to allow each wheel to rotate at different speeds, so that you can go round corners without needing the inside wheel to skip and spin up. In a real car you'd actually want a limited slip diff (LSD) as opposed to and open diff, which allows the wheels to rotate at different speeds, but not to the point that you spin all the power away on one wheel, i.e. an LSD limits the amount of slipping or wheel rpm variation. The gear diffs I have are all very "free" and open, meaning the spin very easily, so if you lift a wheel they will spin that wheel and reduce power on the other wheel. Even the fluid filled diffs on my VX-01T. thicker fluid, should in theory produce more of an LSD. But overall the geared diffs I've seen are more akin to open diffs than LSDs. The ball diff is still probably a bit more LSD by design, although not like a viscous or ATB diff we'd use in a real car.

I do agree that in a straight line with lots of grip, a gear diff will not slip, unless it is jump teeth or shredding them. While a ball diff can, with enough force be rotated. But back when I used to race we'd run 10T brushed motors and carpet tyres and not have diff slipping issues. At least with the Losi and Schumacher vehicles I used to race and watch. A modern LiPo brushless system on 3S or maybe a 2S 6.5T motor is more pokey, but I'd guess many racers are probably running less power than the old brushed setups. I've also just had a look at the Schumacher website and it looks like their current 2wd Cougar uses a ball diff still.

 

I would also say/assume that the slipper clutch should be what you allow to slip, not the diff, hence the name. It is there to protect the driveline and regulate power to the wheels. But I will freely admit I have no experience with Tamiya ball diffs. But I struggle to believe they are fundamentally any different to others. You'd also have to question why Tamiya choose to fit ball diffs to their more expensive race orientated vehicles such as the TD2, while the entry level vehicles like the Lunchbox get a gear diff as standard.....

[Howards 593]

How did you get on in the end?

[River19 65]

On 9/3/2024 at 10:45 AM, Losi XXT-CR said:

Thanks. I'm still not 100% convinced on this though. A ball diffs main purpose is to allow each wheel to rotate at different speeds, so that you can go round corners without needing the inside wheel to skip and spin up. In a real car you'd actually want a limited slip diff (LSD) as opposed to and open diff, which allows the wheels to rotate at different speeds, but not to the point that you spin all the power away on one wheel, i.e. an LSD limits the amount of slipping or wheel rpm variation. The gear diffs I have are all very "free" and open, meaning the spin very easily, so if you lift a wheel they will spin that wheel and reduce power on the other wheel. Even the fluid filled diffs on my VX-01T. thicker fluid, should in theory produce more of an LSD. But overall the geared diffs I've seen are more akin to open diffs than LSDs. The ball diff is still probably a bit more LSD by design, although not like a viscous or ATB diff we'd use in a real car.

I do agree that in a straight line with lots of grip, a gear diff will not slip, unless it is jump teeth or shredding them. While a ball diff can, with enough force be rotated. But back when I used to race we'd run 10T brushed motors and carpet tyres and not have diff slipping issues. At least with the Losi and Schumacher vehicles I used to race and watch. A modern LiPo brushless system on 3S or maybe a 2S 6.5T motor is more pokey, but I'd guess many racers are probably running less power than the old brushed setups. I've also just had a look at the Schumacher website and it looks like their current 2wd Cougar uses a ball diff still.

 

I would also say/assume that the slipper clutch should be what you allow to slip, not the diff, hence the name. It is there to protect the driveline and regulate power to the wheels. But I will freely admit I have no experience with Tamiya ball diffs. But I struggle to believe they are fundamentally any different to others. You'd also have to question why Tamiya choose to fit ball diffs to their more expensive race orientated vehicles such as the TD2, while the entry level vehicles like the Lunchbox get a gear diff as standard.....

There are many ways to approach setup and what works for one may not work for all.  I'm not entirely sold on the ball for dirt/clay and gear for carpet as a 100% fact in all situations.  You asked the "why" behind the common approach and at least in mainstream racing scenes it appears that people find the ball for low grip/gear for high grip setup an easy starting point.  That being said, most racing scenes are limited to a small number of car models with the typical AE & TLR models dominating most fields........perhaps a lot of this approach to diff setup is born from how the diffs from this particular manufacturers perform on each of those surfaces.

Like everything else in racing........nothing can replace actual track time and testing, find what works best for you, but don't forget a large component of "what works best" may be how much maintenance each setup requires.  The absolute fastest setup might be a total PITA when it comes to requiring constant rebuilding etc

[Howards 593]

I suspect on carpet tracks you want the most differential action possible because they tend to have more and tighter bends -  but their very high grip nature means a ball diff, set up loose enough, will slip too much, prematurely wearing the contact surfaces out. 

Have a bunch of gear diffs I was going to fit to my TDs when next doing carpet racing and over the winter. I have a hunch they'll be quicker with them on carpet, especially the TD4.