When did toe-out become toe-in?
 

Having started racing back in the 90s, I'm surprised that many recent setup guides and discussions suggest that front toe-out provides straight-line stability and discourage the use of front toe-in altogether. Two examples are the Essential Off-Road RC Racer's Guide and Invisible Speed. I actually thought there was a mix-up in Joseph's book the first time I read it and I'm quite sure (edit: evidence given below) it was the exact opposite in the 90s, where 1/10 buggies almost always ran toe-in and never toe-out, as recommended by numerous setup guides.

Even today, you can find full-scale racing explanations that suggest front toe-in improves straight line stability whereas front toe-out gives more initial steering (see, for example, https://suspensionsecrets.co.uk/toe/). To my understanding, many of the explanations given (shopping carts, ice skating, wheels being disturbed on a straightaway) can be interpreted just the other way if we consider the second wheel on the front end.

Surely, there must be a way to figure this out based on engineering principles rather than polls among drivers (as done in the Essential Off-Road RC Racer's Guide, no offense to the authors of this excellent book).

You want slight toe-in in the rear while keeping the front end straight or slightly toed-out
Front end:
- Toe out: Inside wheel has more turning angle than outside wheel. Entry steering will increase and will decrease on mid/corner exit. Front end will be more stable as it becomes less twitchy
- Toe in: inside wheel turns less than outside wheel. Lose of corner ability and stability. Undesired effect.

Rear end:
- Toe in: rear end wheels point to the inside. Both wheels pushes each other, creating an effect where the rear end tries to center the front end. Usually results in better grip and more stability.
- Toe out: undesired effect. Each traction wheel wants to go opposite sides. Rear end becomes very unestable

I'd probably ask ray_munday that question. He explains things from an engineering standpoint and has some fantastic videos on suspension and generating traction and adjusting car dynamics.

I do agree that back in the early days (I started in the 80's) toe in was used on lower bite surfaces to stabilize the car.

What's changed? The cars have way more tunability and our setup completely different. Suspension tuning doesn't work in a bubble so the overall package may cause differences to the impacts of toe. Also, track surfaces are wildly different and most have way more grip than we did in the last century.

That being said, I don't have the answer for you. Hopefully someone can come and elaborate from an engineering standpoint.

From an engineering perspective front toe-in is inherently stable, while front toe-out is unstable. Best way to understand is imagine what happens to both setups with a slight turn of the wheels. With front toe-in the wheels are still both pointing inward until you exceed the toe with turning input, so they will re-center. With front toe-out even a slight change in steering angle results in one wheel pointing out more than the other, which will pull both wheels in that direction.

this is why all full size road cars have front toe-in. Front toe-out will cause faster turn-in and more responsive handling at the expense of straight line stability.

In full size car racing generally front toe-out can be helpful on small tight tracks and front toe-in is better on higher speed tracks… but zero toe is a good compromise and is probably the most common (also seems to be the most common in RC)

The only cars that will ever use rear toe-out are drift cars.

That's what I had learned early on. However, this is exactly the opposite of what the two books say.

Perhaps you mean overall toe out, otherwise oval cars can use toe out on a couple corners of the car.

Rc10, are these books speaking of certain types of cars specifically when discussing these subjects.

I remember some 20 years back, I was told that front toe-in was the way to get the car stable, and toe-out to be more or less avoided. Today's cars and setups all have front toe-out as their basic setting, sometimes going close to neutral, but never into toe-in. For stability people look to the rear toe-in instead now. I noticed the change after my break from the hobby, but never questioned it much, since so many things had changed (e.g. in on-road, cars suddenly no longer had front diffs or front one-ways, but spools instead) - and it all worked well (for me actually even much better than before - but I think I sucked at setup back then anyway.), not even mentioning brushless, LiPos and 2.4GHz radios. I just went on and embraced all the new things and never shed a single tear for the old.

You also have to account for suspension slop some where. I think that's what is making such a large difference between racing real cars and our small ones. Real cars can keep nearly all slop out of every joint. Especially a race car with metal spherical joints at every point.

While our offroad rcs are barely a pile of trash held together with hopes and dreams in comparison. Er uh I mean off road cars have a lot of slop. Can you tell I don't like it? But theres no simple way to reduce slop like real cars, as all metal would increase costs too much and add far too much weight.

The key thing to understand is real cars, all slop in the front suspension will addup and give you toe out. Thats why if you have a bad tie rod, the inside edge of your tires gets destroyed. This applies to all cars FWD, AWD, RWD. Suspension issues in the rear are not cut and dry though and arent important to this discussion. I think the front end all going to toe out with slop phenomenon is where the rc tuning weirdness comes in. If you want meaningful toe in at the front, you have to add up all this slop and it over powers any positive aspects of the toe in would have normally.

You also have to realize which is which. As in Front stability, or the ability go in a consistent straight line at high speed, and rear stability for corner entry and exit. Front and rear toe in and out do very different things in different parts of the car and track. For sure an easy thing to overlook when so many other things are on your mind!

In my experience with full scale off road cars, we never use toe-in. Either zero toe or toe-out. On ultra4 cars with full hydraulic steering, I’ve found toe out to be more stable around center and rolls through turns better. For another perspective, I once asked a good friend who is a competitive circle track racer (both dirt and asphalt), he said the same thing, toe-out only for them. I literally grew up in a brake/front end shop that did alignments. If you asked about toe-out, you got a crazy look and an explanation that “engineers say you don’t ever use toe-out”. Fast forward 20yrs, the guy that now owns my family’s old shop brings me a Jeep (crawler build, soft suspension, big tires) says its darty on the freeway and he’s tried everything to calm it down. He was both happy and surprised when I “fixed” it with a touch of toe-out. Engineering and seat of the pants feel doesn’t always line up.

I'm well aware of the difference. Always was. It's just that people 20 years ago were telling totally different things than now (or 8 years ago).

Somebody just uploaded a scan of the setup guide included with RC10 buggies in the mid 90s to an RC10 Facebook group, the relevant page is shown below. The first page says "information given by Cliff Lett [...] and Mark Pavidis [...]". Full post can be found here.


https://cimg1.ibsrv.net/gimg/www.rct...af07e1daec.jpg

Both books are about off-road buggies. Invisible speed has a focus on 1/8 scale. However, the statements about toe seem general.

I personally have never found "straight line stability" to be a thing to worry about on RC cars unless something was broken or way out of whack (like uneven rear toe) so ignore it. Front toe out, slightly more turn in, more aggressive corner entry. Slight toe in, slightly smoother, less aggressive corner entry. I pretty much always run some toe out except for pan cars on carpet where front toe in can help tame and aggressive car.