Saturday , 24 September 2022

Diff-icult Question

The RC Doctor - Return

Diff-icult Question

Hi Doctor-
This question is about the Differential setup you have on your site: I’m running a Tamiya TA05R and I use it mostly for racing so speed is crucial. I also need to be able to take some serious turns. I have two aluminum differentials in the car now as it’s a 2-belt driven car. But I just got a one-way diff and also a solid axle. What do you think about a solid axle in the front and what would you advise for a good combination? Thanks!


Hey Hayden,
First off I’d like to commend you on using your TA05R for racing. That car gets overlooked often simply because it’s not all carbon fiber and colored aluminum. I’ve had one and loved how it handled!

In regards to your diff setup, let’s take a quick look at all 3 options; spool (or solid axle), one-way and the actual ball or gear diff. That area of the site pretty much explains all 3 types so we won’t go into them again, however the typical use in touring car racing is to use a ball diff (or gear diff) in the rear and either a one-way, spool or ball/gear diff in the front.

The one-way diff has pretty much gone the way of the dodo. It used to be the preferred method for making a touring car extremely fast around the track, especially in the corners. The downside to the one-way was the elimination of brakes; unless you’re a pure stud with your brake control, any braking down with a one-way resulted in your car looping out and crashing. In fact, most major races don’t allow the use of the one-way diff, so manufacturers and tuners have done alot of homework to get a TC to turn without it.

The ball/gear diff has been the preferred setup for quite some time. It can be tuned to act like a spool or close to a one-way, but still allows the use of brakes. The downside of this setup is the fact that it needs to be tuned; it’s just another thing in the drivetrain that has to be optimally set for the entire setup to work.

The spool has now become one of the favored options to use in touring car racing. It’s a set-it-and-forget-it item, allowing you to fiddle with the other tuning options to get your car to handle. Once you do, you gain the benefits of excellent turning plus the use of brakes.

So, what’s the best setup for TC racing? I would start with the spool up front and a ball diff in the rear. Depending on your track surface, you should be able to set your ball diff once and leave it alone. Work a bit of traction in the rear of the car before turning to the front; a car that pushes is much easier to drive than a car that is loose. Once you’re happy with the rear-end traction, move to the front. Get aggressive with your tuning to get as much steering as possible.

Good luck!
The Doc

About Tony Phalen

Tony Phalen - As an avid RC enthusiast, Tony has been building, bashing and racing RC Cars for over 25 years. He has raced everything from 1:18th scale trucks to 1:5 scale motorcycles and everything in-between. He's also worked on both sides of the industry fence; working at and with many major manufacturers (as well as being a sponsored driver) to working for a high-profile industry magazine. During this time he has learned many tricks, tips and techniques and has transferred that knowledge to CompetitionX - the most informative RC website on the internet!

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