Setup Wheels - The cheap and easy way

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

Jerold

Very Active Member
Build Thread Contributor
Messages
1,906
Reaction score
3,880
Location
San Jose
Arrma RC's
  1. Limitless
If you know what to tweak, setting up the suspension is not that complex. You can use a ruler or calipers if you have them or other random house hold objects.

The Problem
Looking around at all the tools that help you setup your car, makes it clear that unless you spend big bucks, it's pretty much a scam. The cheap molded plastic tools, parallax and the sloppy tolerances of your wheels/tires make the measurements completely in accurate because of the scale. Unless you have a high precision tools and setup you will never get the exact number any of the tools claim.

First is toe. This is what started this whole article for me. On full size car you measure toe in fractions of an inch (or mm) between the front and rear of the tires. The angles are very shallow, maybe 1° or less and almost imperceptible to the naked eye on a full size vehicle.

First the RC tools guys (RPM cough cough) tell you is the angle, which is just false and pretty much meaningless. Measuring an outside dimension of a tire for "angle" doesn't work for all tire diameters. This diagram show two wheel sizes 1" and 4" both at 1° of toe in. You can see they are both 3.62" width in the back. The front varies by .11" which is a huge number when scale it for your car.

1675617929518.png



Even on the large scale RC cars we are looking at about 1/8" difference front/rear. The tick marks on the RPM Toe Gauge are 1/8" wide and tires are never straight on the wonky wheels. My GRPs have a fair amount of run out (more than 1/8") that I can see when I balance them. Add in manufacturing tolerances of plastic molds and the is more slop in the setup and tools than what you are trying to measure. Yeah it's cheap ($10) but don't waste your money on that.

Camber gauges are pretty cool, but they are expensive and still rely on your messed up wheels and a good eye. If you have any angle to you your line of site, you have enough parallax to be off by 1-2°s. Basically the same problem more slop in the setup than you are trying to measure.
1675648820364.png


The Fix
Let me start with, I'm putting this out there because I want people to stop wasting money on snake oil. Could I market this? Yes, but I have a day job and a few extra $$ on the side is more trouble than it's worth. It's also so simple that anyone can make it with stuff laying around the garage. I used ABS from the Tap Plastics scrap bin, but you could use a block of wood as long as it's flat and has clean edges.

What I don't want is to see someone selling them. The idea is free, the design is free (I will post a PDF) and I think anyone seeing this has enough skills to make them. It's something put out in the world for the better good and not meant to be a profit center.

To fix this I had to reinvent the wheel. Quite literately. My fix is to use custom setup wheels and level surface. These are just flat ABS plastic I hacked out in the garage. I was thinking about sending them out to get done in aluminum but I'm cheap and the min order is like $30. So $1 of scrap ABS works fine.

I drew out what I wanted on the computer then stuck it to a plastic sheet. Cut it out with a jig saw and chucked it up in the drill press (redneck lathe) to make the round and consistent. Like I said it's simple and the next version will be even simpler.

Setup Wheels V1
By using these wheels I just measure everything. With calipers or a ruler. It removes a bunch of variables in the running wheels and tires and give clean consistent points that can be indexed over and over. You can also leave them on for storage and work to keep your good tires clean and avoid flat spots.
Setup_wheels.jpg

The holes on the sides provide access to the pillow balls. You can adjust you toe, camber and track width. You can also measure your caster all while they are on. I suppose you could leave them on to adjust your caster, but it's doesn't make any difference.

This set is round, but I realized that it doesn't need to roll and I can make the square. Square wheels will also make measurements much easier and more accurate because I have a level vertical edges to reference I don't need to work around the hub that sticks out. The square wheels are also easier to make, because I can crank them out on my table saw, then drill/cut the access holes, just the same.

Measuring Toe
Toe is simply measuring an equivalent point on the back and front of the wheel and subtracting the front from the back. That difference is your toe setting.

The question is how much toe in or toe out. Typically you want a little bit of toe in (front is narrower and positive number) to help it track straight, or a little bit of toe out (back is narrower and negative number) for better turn in performance (AKA responsive steering). Too much is bad in either direction. If you have it set at 0" toe, it does nothing for you.

With the square wheels (in progress) you can just use a piece of paper and make two marks to get an idea of how much of what you have. The difference of the back to front measurement can be as small as ball point pen or maybe a sharpie. This will put you some where 0.030"-0.060". Which is probably about right for hard surfaces. If you want more or less use a highlighter or marker, the wide end will get you about 0.1". Realistically consistency of setup is probably more important than a few hundredths of an inch either way.
1675664497993.png


Measuring Caster
More caster makes your car track straighter. However, too much caster will make the steering heavy (maybe slow with a weak servo) and can effect your tire wear.

The adjustments are typically done with spacers and it's finite. You can stack the spacer in front of the upper control arm (more caster) or in back (less caster). Just make sure both sides are the same, unless you doing circle track or something like that.

In any case you can measure what you have, record in your setup sheet. Then decide if it needs to get changed.

To measure caster put one hex driver in each pillow ball (top and bottom) on one side, then measure the angle. In the picture it's maxed out at about 20° of caster. You can use a bit of trigonometry to calculate it. :unsure:

Or buy a cheap angle gauge from Amazon.
1675664939193.png

Nah Just use your phone. It's close enough and there is no fine adjustment to do anyway.
1675666385680.png


Measuring Camber
This one is probably the easiest. You can set each side equally using a shim of your choice to measure it - three razor blades thick is a measurement. And if you need an accurate setting you can use a machinist ruler, calipers or feeler gauges.

Camber helps you maximize your traction and handling. The problem is the conditions of the car will change when turning and your tire patch can increase or decrease with weight transfer. The idea is to setup your car so you have maximum traction on the wheels that need it, when you do what you do.
1675669499077.png

Negative camber helps for corners. It can help compensate for the suspension geometry when the chassis leans. However, more is not always better, because it can wreck your tires pretty quickly. With that said the car tires balloon so much during acceleration, it probably doesn't matter much.

Neutral camber works for straight lines. It keeps your tires flat to the ground.

Positive camber is typically on off road vehicle and provides more stability in the rough stuff. ... Or at least I'm told.

To measure it, place something with a right angle (like a speed square) at the base of the wheel, then measure the gap at the top (negative) or the bottom (positive). Then adjust it to your needs.

Again these are very small adjustments and thin items like razor blades, feeler gauges are handy. A heavy duty razor blade is about 0.030".
1675667501682.png

Using my setup wheels, I get about 0.07" of deflection for every 1° of camber.
1675664267891.png


Which means the diagram above (not to scale) shows about 5° of camber.

Conclusion

I hope this helps people get a better handle on their suspension geometry with the ability to measure it and adjust it more accurately. The setup wheels are a simple tool that you can make quickly and cheaply at home. That combined with typical household objects can get your suspension geometry in order quickly.

In the end I would love to see junk like the RPM Toe Gauge go away and be replaced by homemade tools that are better and cheaper. Seriously stuff like that shouldn't exist.

There are two PDFs in the ZIP file. Feel free to adjust them for your needs.
 

Attachments

  • Setup_wheels.zip
    400.7 KB · Views: 88
Ok, I get measuring camber as it's independent to each wheel. But how do you measure toe without referencing the opposite wheel or the vehicle centerline? Would you not need to actually measure the included angle to get it right? As the wheel moves further from zero the distance between the front and back of the wheel gets shorter. I know the distance is small but I spend somedays measuring to the .0001" and there are times small numbers add up. Also with the amount of slop in the assembly most of it is moot, no? Personally I just look at it and turn stuff until other stuff looks close. As I'm probably going to smash into things anyways I haven't got too far into the thought process. Great post!
 
Nice job, there is a lot of great info in there and everyone always has that “deer in the headlights” look when they’re new at it.
I‘m wondering about the caster adjustment. Your method would be great to insure that both sides are equal in the measurement, but I don’t think it’s going to give an accurate number of total degrees as the roll center isn’t very close at all to the two points where the pillow balls are. (I don’t think I explained that very well.) The way the Arrmas are set up, if that number would be accurate then the outboard pivots would be “up and down” instead of really canted as the Arrma hub carriers are. They’re already tilted many more degrees regardless of your caster setting, so if you had actual zero caster then measuring off the pillow pivots would still show several degrees of positive caster because the upper arm geometry is so far to the rear as opposed to the lower arms. Again, I don’t think I’m explain myself very well but to get actual degrees the hub carriers would have to be perfectly vertical when caster was at zero and they’re not. That said, it doesn’t really matter anyway. You just need a certain amount of caster and need to make sure both sides are adjusted exactly the same, and your method seems like it would work perfectly for that.
Your dummy wheel discs are a great idea, we used to get initial 1:1 suspension setups when the car was leveled on stands at all four corners with the wheels off so we could measure off the brake discs, pretty much the exact concept.
Again, nice work, man!
 
Ok, I get measuring camber as it's independent to each wheel. But how do you measure toe without referencing the opposite wheel or the vehicle centerline? Would you not need to actually measure the included angle to get it right? As the wheel moves further from zero the distance between the front and back of the wheel gets shorter. I know the distance is small but I spend somedays measuring to the .0001" and there are times small numbers add up. Also with the amount of slop in the assembly most of it is moot, no? Personally I just look at it and turn stuff until other stuff looks close. As I'm probably going to smash into things anyways I haven't got too far into the thought process. Great post!
So yah, it's a problem not having a full setup table and getting it exactly right. But we don't have a steering wheel to align to and we have trim on the servo. Ideally your trim is set and the tires are straight at power on.

However, I can adjust or set it by using a straight edge and align the front and rear wheels to make sure they have the same gap (D1 = D2) or contact at the same point. Then I know they are roughly straight-ish and symetrical-ish. This is an overly simplified diagram. So yah, it's a problem to get it exactly right. But we don't have a steering wheel to align to and we have trim on the servo.

1675724372515.png

I supposed if you really wanted to be exact you could align the chassis (center brace) with a known line to be parallel, then center your wheels based on that. Maybe use a laser level?
Nice job, there is a lot of great info in there and everyone always has that “deer in the headlights” look when they’re new at it.
I‘m wondering about the caster adjustment. Your method would be great to insure that both sides are equal in the measurement, but I don’t think it’s going to give an accurate number of total degrees as the roll center isn’t very close at all to the two points where the pillow balls are. (I don’t think I explained that very well.) The way the Arrmas are set up, if that number would be accurate then the outboard pivots would be “up and down” instead of really canted as the Arrma hub carriers are. They’re already tilted many more degrees regardless of your caster setting, so if you had actual zero caster then measuring off the pillow pivots would still show several degrees of positive caster because the upper arm geometry is so far to the rear as opposed to the lower arms. Again, I don’t think I’m explain myself very well but to get actual degrees the hub carriers would have to be perfectly vertical when caster was at zero and they’re not. That said, it doesn’t really matter anyway. You just need a certain amount of caster and need to make sure both sides are adjusted exactly the same, and your method seems like it would work perfectly for that.
Your dummy wheel discs are a great idea, we used to get initial 1:1 suspension setups when the car was leveled on stands at all four corners with the wheels off so we could measure off the brake discs, pretty much the exact concept.
Again, nice work, man!

Yes I was thinking symmetry is the easiest way. There are a lot of variables to get it exactly right but in scale we are talking about hundredths of an in difference and I'm not sure that any affordable setup would be accurate enough.

Good point on the pillow balls. They are actually a bit too flexible and will allow you to have an asymmetric track. You could crank one side all the way out and the other all the way in. This would make your chassis off center and it would crab. That's what @ilikehosewater was saying a center line would be useful.

May use the center of the hub and measure to the center of chassis brace would be a good start. Remember the setup wheels have a hard edge and it will be easy to measure.
1675725638180.png

Of course all this changes if you don't have your car level, correct preload in the shocks and ride height adjusted.
 
Last edited:
I show some simple trick - how to test car - if go really straight forward :)

We need flat surface ;-) and whell with flat tyre (like foam) . Car need to be fully equiped - final weight and afer final suspension adjustment

We just remove links from front suspension - and whell freely spinning


have a nice watching ( video is from Typhon test - but later can find next for Limitless)

 
I show some simple trick - how to test car - if go really straight forward :)

We need flat surface ;-) and whell with flat tyre (like foam) . Car need to be fully equiped - final weight and afer final suspension adjustment

We just remove links from front suspension - and whell freely spinning


have a nice watching ( video is from Typhon test - but later can find next for Limitless)

Didn't think of that, but it works!
 
Thanks, Guys, I have struggled with this ( apart from camber which is easy with a speed square ) don't see the need for an expensive setup station for a street bash car.
 
Speedrun car is lottle specyfic car ;-)

Next old video with Limitless and no servo links .

Two test:
-whell max right
-whell max left


;-) I have HUDY setup station for 8 scal3 cars, but always after adjusting on station need little correct on flat concrete surface.

This "no links installed" test really works fine, but with few condition
- final weight of car
- whell with flat shape (not use rubber grp)
- car initially propper set zero camber
- exact this same caster on both
- symettrical TOE,
-----I sugest 0,5 in for backaor less
----- and and 0,5 out for front
(my personal preference)


And my car go with almost not touch steering whell


And additional magic, we need change steering link - to increase steeering precision (resolution)

Finally this makes better precision 6x... and servo "is 6 x stronger"

If someone need more explanation what is this... and why ;-) this need additional topic
Screenshot_20230925_205940_Photos.jpg
Screenshot_20230925_210110_Photos.jpg
Screenshot_20230925_210020_Photos.jpg
 
Have you tested ???
Yes. I used the round wheels on my Limitless. It's not like the fancy setups, but for $1 in scrape ABS plastic it's amazing.

I haven't made or tested the square wheels yet, because my round ones work fine.

They can be made out of anything that ridged, plastic, plywood, metal, etc.. What ever is lying around the house.
 
Straight bars and a digital angle gauge with the chalk test.

IMG_0435.jpeg
 
Old Thread: Hello . There have been no replies in this thread for 90 days.
Content in this thread may no longer be relevant.
Perhaps it would be better to start a new thread instead.
Back
Top