Gearing, upgrading TT-02 questions etc.

[Sam_SF]

I really want to compete in local 1/10 rally competitions, but my Himoto car doesnt pass the scale requirements. I want to to put my electronics and engine (except broken servo) onto Tamiya TT-02 chassis. I need my build somewhat competitive with XV-01. I have a brushless KV3210 engine, and as i know, key to compete with better things is proper gearing. So i want to squeeze the most out of my engine while keeping the car good for rallying.
As I calculated, stock 22/70 gearing = 26 KPH.
My 19/48 gearing = 32,7 KPH.
Random  internet guy's reccomended 29/64 gearing = 37,5 KPH
My questions are: Can my gears be compatible with the chassis? Do i need to buy exactly tamiya-branded gears? Most important: Can you recommend me the best ratio for me? How do I know if my calculated "perfect speed" ratio will damage the diffs? Well no one stops me from getting a 55T pinion and 50T spur gear milking them 91 KPH.
Type of races I want to compete in:

 

This Toyota looks like it has too much power... Maybe gear ratio for better steering and acceleration, not top speed? Idk

I'll be on race here tomorrow. Looks like this car (1:27) is too grippy... I actually plan to run my car both awd rally and goof around 2wd drifting
SIDE NOTES:
I know i'll have to "modify" the chassis to be more rally-acceptable and buy some hop-ups like proper shocks and bearings. You're welcome to suggest more things I could upgrade.

[Kowalski86]

A Yea Racing motor mount and Tamiyas high speed gear set will open your options up to non-Tamiya spur gears, so long as it fits under the gear cover.

For shocks I highly recommend Yea Racing shocks, they come with a variety of different springs and offer more adjustability than CVAs, they look neater too.

The turnbuckle kit for the TT-01 will work on your TT-02, it's a cheap upgrade that opens up more tuning options and replaces the goofy plastic ball suspension links.

If you're unhappy with the stock steering, the Yea Racing set should be good enough. I've tried like mad to make the plastic work and my luck hasn't been great.

An aluminum driveshaft will be handy for brushless, stiffer more direct power.

Mark Bryan made a series of videos with some good advice. But I will caution against using hot glue to keep dirt/rocks out. Instead I suggest modeling clay (plasticine), it doesn't dry so you can clean it out easily, and it adds just a bit of weight to the front. Also, you can get it in blue!

Alternatively...you could buy an XV-01 if you're willing to put up with a more finicky, complicated chassis.

 

[Pylon80]

I will add to @Kowalski86's advice above that yeah racing shocks will probably come with drift spec springs - even the softer ones will be way too hard for rallying.

But let's step back for a moment! If you really intend to race, your very first step should be to go to the track where you intend to race. The other racers will give you the best possible advice. The first piece of advice will probably be that upgrading your TT-02 will cost more than buying an XV-01 outright. But if you have the budget, modifying the TT-02 will be a fun journey. It's surprisingly enjoyable to put lipstick on that particular piggy. Ask me how I know!

Regarding your gearing question: again the first step is to verify that your motor is legal for the race class you intend to enter. If that is the case then the racers at the track would be using a similar turn motor. You can then ask them about their XV-01 gearing and apply that to your TT-02. I think it will be easy since both cars share the same internal drive ratio of 2.6 🧐 meaning that if you use the same spur and pinion you will have what they have.

Best of luck!

[Juggular]

3 hours ago, Sam_SF said:

Looks like this car (1:27) is too grippy...

It feels "grippy" when you have too much control at the lower end. You have good control speeding up and down, it doesn't overshoot. The car has enough time to turn left and right... so people would describe it as "grippy." 

If you make the gear taller, you'd get higher top-speed (I understand that higher top speed isn't the goal). The competition looks like you'd never hit the top speed. But a taller gearing would give you a bit less time to control speed and turning. That should make it feel a bit less "grippy."  

I like the video @Kowalski86 attached.  I also seal gearboxes with grease.  But I use plumber's grease.  It's not sticky and easy to wipe out when you clean it. 10 times cheaper than AW grease also.  

The tracks you'd be racing looks very curvy.  Because you'd be turning so much, I may use regular grease on the front diff and use AW grease only in the rear. 

I only run bashers. So in my particular case, I use grease that's a lot stickier than AW. (Even if only one wheel touches the ground, it may jerk forward). 

But sticky diff makes the car resist turning a bit. Normally, that's not a problem, but it tiny resistance could add up if you have to turn every second.  So... for those curvy tracks, perhaps it's better to use AW only in the rear and normal grease in the front.  (A&B wheels would experience greater differential than C&D above.)  Stickier diff in the rear could "plant" the rear wheels to the ground.  If the track is grippy and too curvy, regular grease on both diffs.  It depends on how you drive too, but you get the general idea.   

If it's dirt or grass where you'd have more diff-unloading, you might choose to use AW on both front and rear.  The car would doggedly go forward when diff-unloading can make other cars go hesitant.  

 

[Kowalski86]

33 minutes ago, Pylon80 said:

I will add to @Kowalski86's advice above that yeah racing shocks will probably come with drift spec springs - even the softer ones will be way too hard for rallying.

 

Good call, would the kit springs fit on Yea Racing shocks? I've had good luck with CVAs, it's just a bit tricky finding the TT-02 specific set.

Diff tuning is very important as Juggular shows. I have my "budget basher" TT-02D with clay in the front diff. It makes it a bit "point and shoot" but for a more twisty track it'd make it understeer. 

 

[Pylon80]

18 minutes ago, Kowalski86 said:

Good call, would the kit springs fit on Yea Racing shocks? I've had good luck with CVAs, it's just a bit tricky finding the TT-02 specific set.

As long as the aftermarket shocks are not 'big bore', the kit springs will fit. But even the kit springs can be too hard for rallying. They are silver but in fact they are exactly the same as the yellow springs in the "hard on-road" set (53440)! Instead, I use the rally spring set (53163) on my TT-02 rally car. Ka-ching, another 12$ gets added to the tally 🤣

[Kowalski86]

7 hours ago, Pylon80 said:

! Instead, I use the rally spring set (53163) on my TT-02 rally car. Ka-ching, another 12$ gets added to the tally 🤣

Thats if you can find them, looks like they're out of stock atm.

[Pylon80]

1 hour ago, Kowalski86 said:

Thats if you can find them, looks like they're out of stock atm.

I admit to having bought my set back in 2019 in Japan. This would be really annoying if it became one of these rare and hard to find item. I don't know of any other alternative; even drift springs marketed as super soft are an order of magnitude too stiff. Maybe XV-01 springs would work? You can still get these.

[Kowalski86]

3 hours ago, Pylon80 said:

I admit to having bought my set back in 2019 in Japan. This would be really annoying if it became one of these rare and hard to find item. I don't know of any other alternative; even drift springs marketed as super soft are an order of magnitude too stiff. Maybe XV-01 springs would work? You can still get these.

Agreed, especially with the number of TT-02 builders who'd like to start rallying.

XV-01 shocks might work if the length is the same as a TT-02, or close. Otherwise there should be other aftermarket options.