What is Caster and How Do You Adjust It on Your Race Car

This is a video on what caster is, how to measure it, and how to adjust it. We go through an in depth explanation of what caster is and why it matters to the racer. We also give some specs on what your caster should look like on the average dirt race car. Caster adjustments vary a bit from car to car but we cover a broad overview of how to adjust caster. We also cover the myth of the digital caster gauge.
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[@scumdog88]

You won’t find a better video covering this topic anywhere online Zero bullshit all fact. Thanks RMB racing

[@rockscrambler6700]

Pure Gold! I have 96 f250 with a twin traction beam and no one seems to want to hassle with it so I set out to figure it out myself and this video filled in all the missing pieces.

[@michaelluddeni5717]

Your chassis set up plates are the best that I have seen. The ball rollers/Monoballs give you the most freedom of movement without any bind. I made my living as a race car and parts fabricator in the past, also a driver for many years and have seen many different alignment systems.

[@davecoberly3768]

Bought your set up plates and they are awesome. Keep the videos coming.

[@MrShawnLester]

One of the best video's on Caster Ive seen... good job.

[@marktrevarthen5017]

Thank you, I found this massively helpful and your explanations are really expert and very clear. The one thing I can’t quite grasp still is why / how the bubble gauge works to deliver the measurement … but it’s probably enough for me to know how to use it correctly. Looking forward to more content like this - thank you for sharing…

[@jamesspeck4151]

Thanks much! Your explanations are excellent!

[@reemnasser9105]

Simple explanation. Thanks for the video.

[@HairryTurttleneck]

Nice and clear video, nice job dude!

[@marcuslawson3406]

Excellent video for a newbie, thank you.

[@contractor9391]

Best video online explaining caster. Thank you

[@garyjeffrey4484]

This a very clear and easy to understand explanation of caster. Thank you

[@RMBRacingInc]

Glad it was helpful!

[@JArtMiller]

Excellent explanation of a very technical subject. Well organized thoughts.

[@RMBRacingInc]

Thank you kindly!

[@carlosbah4623]

Very good and clear video. Thanks! ¡Gracias!

[@user-tu4mf2dz4g]

Thanks for all you do...

[@dolansontag3731]

Good tutorial thank you

[@robertjones7695]

Excellent. Very helpful.

[@RMBRacingInc]

Glad it was helpful!

[@kenrego2528]

Very Good Video ! Thank you

[@RMBRacingInc]

Thank you for the feedback. We will have more videos soon.

[@edzinator8499]

Very good detail on caster setup, thank you.

[@prabhuorion9202]

Thanks a lot brother

[@raymondmartin3254]

I like to use 2 plates sheet metal with grease in between to reduce friction for an adjustment plates as well as alignment setting.

[@timchilders3535]

yep, that always works great, been using that method for a long time.

[@EvilChuckie]

To set castor swing the wheel out 20 deg. set the bubble to zero, swing the wheel through 40 deg. (20 deg. inward) and read the guage, this measurement does 'not' reference the ground, its just the change of angle the front wheel swings through, showing the forward/backward angle/inclination of the axle.

[@RMBRacingInc]

You are correct however it is based on level which is a constant and consistency is everything. Thank you for the input.

[@jwickert3]

Well done.

[@RMBRacingInc]

We appreciate the feedback. We will have more videos coming like this.

[@scottprentice8411]

Okay, so next week. When you're talking to your Friends or co-workers. In trying to be impressive on how much you've learned on this video. But just can't remember which way positive caster And which way is negative. And the same with camber. You will now never forget which way is which always remember. Camber Tilt towards The cam. Now After you come home after a hard day's work. And your beautiful young lady is laying on her back with her knees Bent and the knees are away from each other. That's a positive thing if her knees are touching, that's a negative thing. Hopefully we all love motorcycles I do. When looking at a motorcycle. From the side. You will notice the front forks. On the harley davidson chopper things. They have a whole lot of positive caster. A motocross bike has a lot less positive caster. The motorcycle that Rear ended somebody I do and the front wheel is pushed all the way back to the engine. Has negative caster. You will now never forget which way positive. And negative goes as far as caster and Camber is concerned. As far as toe in and toe out just look down at your feet. Have a good day. And I hope this was helpful,

[@RMBRacingInc]

Quite the visual. lol

[@jswappedintegra]

What are your thoughts on the quicktrick alignment setup for caster with the turn plates and their methods?

[@RMBRacingInc]

It is always tough to look at other options unbiased. From what little I have seen of their product it appears they are taking measurements much like a normal car alignment machine. That is not bad in and of itself but you are relying on the wheel being accurate and that causes me concern in the racing world. I very rarely have seen a racing wheel that is true and in the dirt world most of them are bent after one race. I can speak to what I feel are advantages of our plates. Our plates can be used for way more than just Caster, Camber, and Toe. If someone is using our plates and that is the only benefit they get then we have failed. We increase accuracy by eliminating the wheel and tire for better repeatability and there is no need for turn plates. I will admit I do not know that much about quicktrick. I hope that helps answer your question and if we can be of any further help just let us know.

[@kenrego2528]

Interesting!

[@baims8367]

Dave Hammond has found a pretty bad ass ez way to use the little digital guage basically it’s. Some 3/4” flat stock that he built a box the gauge sets in with 2” hanging over that then attaches to bottom of the top ball joint nut and then the gauge is like hanging off of the ball joint nut 🤷🏼‍♂️ seems to work pretty good. For him.

[@RMBRacingInc]

Unfortunately it is not accurate or consistent. It is just a fact that you have to do a sweep to accurately measure. Even the best alignment machines have to do a sweep.

[@Bashvm]

what does caster do for each tire? i know the lf is for jacking force onto the rr but i havent found what it does for the rf. in race videos ive seen the tire roll closer to the side wall while counter steering. seems to help reduce push?

[@RMBRacingInc]

Good question. I think you are confusing caster with some of the other geometry angles. Try to keep it simple. Think of a "caster" on a buggy or roll cart, as soon as you push it the wheel turns to the back side. Caster on a car does the very same thing. It provides directional stability. The more caster you have the harder the steering will is to turn and the more directional stability you will have. It will naturally want to go straight. Now when we introduce two wheels (front tires) that have different amounts of caster that causes a pull in the direction of the tire with less caster. The reason you see RF tires with so much caster is simply to help make the care turn left. This is also why it is typical to run a very small amount of caster on the LF. It has not been my experience that caster has any effect on a "jacking force" however extreme camber during counter steering can cause a jacking force. I hope this helps clarify it further for you. Thank you for the question.

[@marcorivera7571]

Would like to know how to adjust the caster and camber on 1965 Ford falcon, tank you.

[@RMBRacingInc]

All of the same principles apply and you can use a bubble gauge to set caster and camber on a Falcon. When that car was new that was the standard way to measure and set it. As far as adjusting caster and camber on a Falcon you will use shims behind the upper control to adjust it and if I remember correctly it will have a lower strut rod that can also be used to adjust the caster. Hope that helps.

[@davemorgan3016]

I’d like to know your take on how I’m gonna get the car to wanna turn left by itself and we’re running pavement and there’s really no suspension it’s just a straight spindle so there’s no shock there is a Way with HAIM joints to adjust the caster camber but how much split makes it want to turn left by itself and not scrub off any speed

[@RMBRacingInc]

I will try to be of assistance but may need some more specifics. In short, toe will cause drag that scrubs off speed but caster for sure will not and camber should not either. Any split helps the car turn but the more you split the more it turns left on its own. To give you an idea, our cars have so much that if you let go of the wheel even just idling around it will turn left instantly. This also makes loading in the trailer a pain because you are constantly fighting it wanting to turn left. As a general rule you will notice differences in a degree of change but do not be afraid to try large numbers. Experimenting will be your biggest help in finding what works best for your application.

[@smokey4201489]

Is there a video in adjusting camber ?

[@RMBRacingInc]

We apologize that there isn’t. We have just been swamped and have not been able to take time to make it. By all means give us a call at 304-252-7223 and we will walk you through it.

[@mrmxpop]

What set up plates are those and do you recommend brand/model any in particular? Specifically for road course cars. TIA

[@RMBRacingInc]

The setup plate in the video is manufactured by us so it is hard to speak to certain brand or model without being biased. That said our plates utilize a mono ball that allows the plate to move very freely. To our knowledge there is not another plate on the market that does this. If you want feel free to give us a call if you have any further questions on our plates. We try very hard to not sell or push our products in our videos but to keep them completely informational for the benefit of all.

[@mrmxpop]

@@RMBRacingInc Thx for the reply. I have considered making my own and even have a fab buddy who wants to make/market some so who knows where that will take me. Did find these (not to push a brand) and they look cool for about $500 for a set of 4. hammondmotorsports.com/5x5-setup-plates-red/ Thx for feedback.

[@RMBRacingInc]

@@mrmxpop those plates use a one direction roller bearing. They are the reason we make what we do.

[@guruguy6800]

How do you get more camber if your shock is dang near hitting.... Can we move the shock away from the middle and if we move the shock to the side and make a new mount, is there any cons to doing such?

[@RMBRacingInc]

Shock placement can be a major issue and there are pros and cons to its location. We have seen them mounted in all sorts of ways including mounting them outside the upper a-frame. There is a moment center and the angle of the shock does affect its performance. If you are having clearance issues it is most likely on the RF and if you are racing on dirt the main goal is to get the car on the RF and keep it there. You are forced to decide if shock placement out ways the Castor/Camber numbers you are trying to achieve. Most will agree that the Castor/Camber is more important than the the shock location especially on the RF where you do not plan to travel the RF very much. That all said, we would recommend moving the shock to accommodate the castor and camber. Try to keep the lower control arm end of the shock as close to the ball joint as you can and the top can go wherever you need it to go so that it does not hit. Hope this helps and answers your question. Feel free to give us a call if we need to go into further detail.

[@jlmnation486]

How much positive are negative caster do you want in the right front on street stock

[@RMBRacingInc]

You always want positive caster. If you have negative caster the car will be very darty and unpredictable. A good place to start is 3 degrees but if you want the car to turn easier or if the car is a bit tight you can add more to help it turn more.

[@tandybarnes4826]

On the right front for a street stock is that positive or negative

[@RMBRacingInc]

Negative caster is to the front of the car and positive is to the back of the car no matter the side. You always want positive caster. Negative caster will make a car very darty and uncontrollable.

[@tandybarnes4826]

Thanks for the quick reply

[@borismcfinnigan3430]

I have to disagree about measuring off the upright not being accurate. In actuality he best way to accurately measure caster is by directly measuring the kpi (maybe not with a cheap digital level and not just holding it against the camber angled spindle) Which is the reason you wont see an F1 team etc ever using a longacre etc bubble gauge and will measure the kpi directly..... Let's also remember that you eyeballed that plus and minus 20 degree steering angle and the bubble is 100% reliant on the left and right turn angle being absolutely equal to give anything close to a measurement you can rely on. Very good insight and the key is repeatability anyway not necessarily the number.

[@RMBRacingInc]

Appreciate the comments. Some of your observations are accurate but not practical for the average racer as you indicate. We typically do eyeball the angle of the gauge because it is quick and easy and if you vary that by up to 5 degrees either way the resulting value you get is still within less than 1/4 degree off and that is acceptable in most applications. If you wanted to make it more accurate you can use either turn plates or you can take the time to layout your 20 degree sweep on the floor using chalk lines. That said a digital gauge on the upright is still not accurate because you have to have a datum to zero off of and outside of an F1 team you’ll not find that. As mentioned, if a digital gauge could do it accurately John Bean and Hunter alignment systems would use it. We present the most accurate method using the tools available to most racers. Are there imperfections? Yes but we are not racing F1 so we use the tools we have to get the best result we can. Thanks again for your comments and opinion.

[@borismcfinnigan3430]

@@RMBRacingInc Agreed on those points. Like i said though a great video and a great tutorial

[@ralphmossman974]

Hi Boris, this is an interesting problem that I have also noticed.It becomes far more problematic in a road race car when the castor settings go above 10 deggrees. By swinging the wheels at only a 15 degree angle ,and using an intercomp electronic castor guage, the laying back of the top ball joint was unbelievable to get to the 10 degree angle that the swinging the wheels required. I then measured the ball joints and drew them out in real size,and then measured the angle from a zero / 180 degree datum line and it was way, way past 10 degrees.!! I think the swining the wheels method is great up to 4 or 5 degrees, but anymore than that requires a machined surface , like a steering arm , or an adaptor plate that is attached at 90 degrees to the upper and lower ball joint line, and using an electronic level guage. The electronic level guage can be zeroed to the ground plane that the suspesion set up is being referennced to. Anyway Boris, thanks for bringing up the same problem that I had when trying to do a set up that required a large castor setting.

[@robertsamspon4232]

quick question on this... what if i dont have adjustable uppers as you have? i have almost identical setup besides upper is solid. I have slots under the arm, and what looks like a wedge shim. My lower trailing arm is adjustable also from the frame to the lower control arm. im reading -1.5 on driver side, and -3.5 on passenger side. wayyy out of happiness

[@RMBRacingInc]

So if that is your Caster numbers you definitely have work to do. Your question depends on the car. but the fact you mention the lower being adjustable I am thinking it may be a late model and if that is the case you can absolutely use the lower to adjust the caster. If it is a street stock and it is out that far you are probably going to need to do some cutting and welding on the upper mount to relocate it where it needs to be and then you can use shims on the upper to fine tune it. I hope that helps. If not give us some more application info and we will try to help again.

[@robertsamspon4232]

it is a custom chassis under a daytona coupe body " going from track to street". The upper control arms do not have threaded rod ends on it for adjustments, but where the upper control arm mounts to the chassis, it has steel 6" cross shaft to mount it. the cross shaft mounts on top of chassis brackets that are slotted to move the a arm in and out for setup. the shim i was referring to above looks like an "anti Dive shim". After watching your video i played around with the adjustments a bit. I loosed both upper A Arm bolts and got the Spec.s a bit better but what i noticed was..... if i adjust the lower control rod, from the lower ball joint to the chassis, it pulls the lower control arm rearward which looks like it can put the lower control arm geometry in bind not being 90* to the chassis. . Caster +2.5, Camber -1.0, and Ill work out toe at some point. it has Coleman spindles, sweet manual steering rack....... @@RMBRacingInc

[@RMBRacingInc]

Is it possible to post a picture or email us a picture? Using the lower strut to affect the caster a work but you do not want to have extreme pull on it or you are correct it can cause binds. I am sure you can adjust the upper where it mounts to the chassis but an image would help us better identify the best way for you to adjust it. If you need to send us an email, send it to [e-mail].

[@robertsamspon4232]

yeah i can email you, or i could send a photo to your facebook page, so you can view it easy if that would work. Just trying to identify what parts are on it, and how to correctly adjust them. been a can of worms to get sorted out. =) @@RMBRacingInc

[@RMBRacingInc]

Sent you an email. @@robertsamspon4232

[@jasonmorse6672]

does all this also compy to a front wheel drive as well

[@RMBRacingInc]

Caster is same on all cars race or street rear or front and even big trucks. That said the amount of caster you want will probably be a bit different on a front wheel drive depending on the rest of the setup. Just guessing I would look for a couple degrees of split but not having personal experience driving a front wheel I do not want to lead you wrong. One thing is for sure if you want it to turn left more run a bigger split of caster.

[@jasonmorse6672]

Thank you for the help i will put this into my notes and apply it and see what it does will write back and let you know thank you again

[@RMBRacingInc]

@@jasonmorse6672 your welcome and for sure let us know how it goes.

[@tandybarnes4826]

What's your opinion on the hammond caster and camber kit

[@RMBRacingInc]

Are you asking about the digital gauge kit?

[@tandybarnes4826]

Yes

[@RMBRacingInc]

@@tandybarnes4826 probably not the popular opinion but it is impossible to accurately measure caster with a digital gauge no matter who makes it. We speak to this in the video. The issue is having a proper way to zero the digital gauge. 50k alignment machines cannot check caster without a sweep so there is no way a simple digital gauge can do it accurately. You a far better to use a classic bubble gauge and do the sweep. Not that you have to have our setup plates to do the sweep but it is one reason guys really like them. Hope that helps and thank you for the comments.

[@tandybarnes4826]

I can't get on your website

[@RMBRacingInc]

@@tandybarnes4826 we had our website hacked by 4 different people a few weeks back and they literally destroyed it to the point we have to make an entire new site. It will probably be down for awhile until we can get time to make a new one.

[@kernsy6715]

Where can I purchase those caster/camber plates?

[@RMBRacingInc]

You can call us at 304-252-7223 to place an order. We will also have a new website up in the next few months at www.rmbracing.com. We were the unfortunate victims of hacking and the destroyed our website beyond use so we had to pay for a new one.

[@kernsy6715]

Thanks. Can you do a video on setting pinion angle or can you tell me the best way to do that?

[@RMBRacingInc]

@@kernsy6715 We will add that to the "To-Do" list but it may be later this year before we get time to do some more videos but if you would like to give us a call at 304-252-RACE. We would be glad to go over it with on the phone.

[@juniorwhelchel6337]

I run pure stock class how can I adjust the caster on my stock a frames

[@RMBRacingInc]

When you adjust caster on a stock a frame you have to use shims and you have limited adjustability. To add positive caster you will add shims to space the front of the a frame out therefore using the ball joint toward the rear of the car. It is common for guys in stock type applications to remove the factory mount and relocate it being sure to not leave any evidence that it was moved. Guys have been doing it since the 40's. Hope this helps

[@BlackWidowdetailing]

Can bad caster cause the tire to rub the rear fender well

[@RMBRacingInc]

If I understand what you are asking correctly, caster should not affect that but camber could cause that.

[@baims8367]

Any asphalt street stock #s info??

[@RMBRacingInc]

We are way better a dirt than asphalt.That said, I can tell you that you want to use as little toe as possible to prevent scrubbing. I have seen guys getting this down to 1/32 or less but you have to have good tight steering to do this. I would recommend starting at an 1/8 and work you way down. If you ever have darting or wandering on the straights you need to add toe back in. As far as caster, a good rule of thumb is 1 positive degree on the LF and start with 3 degree on RF and you can add or take away to help the car turn as needed. Hope that helps and maybe some others can chime in for a bit more information for you.

[@baims8367]

Thanks for the reply. Hell the track I’m at I got the car working the best and very very well I might add is by setting all my toe off the left front and at 1/2” out. This track is like a bigger style paper clip 😂 and there left front way out like that center off seems to really really works. Who knew. But if it works it works right. Caster on LF is just on the neg side of to Tire temps don’t lie

[@charliesmith7942]

When u ad postive caster to a wheel with camber it will gain more camber as you turn the wheel. Also knows as " change up ". Camber gain.

[@RMBRacingInc]

Sorry for the late response. For whatever reason we are just now seeing this. Caster does effect camber which is one reason it is best to set caster first but I think you may be trying to describe Ackerman. Not sure if that helps at all or not.

[@charliesmith7942]

@@RMBRacingInc Ackerman is when one wheel turns faster than another. This happens when u change the length of the steering arm on the knuckle

[@RMBRacingInc]

@@charliesmith7942 Thank you for the clarification. I know that ackerman is when one travels faster however this change often causes a greater camber gain on the RF than the LF. Just trying to clarify your initial comment but we may have just confused it more. Lol. Thank you for the input. In the future I will try to cover each of these separately to help clarify for everyone.

[@wrighthausracing9641]

Do more videos dude 👍🏻🫡

[@RMBRacingInc]

Thank you. We really want to however we are so covered up right now we can't keep up. We promise we will as soon as we can shake free.

[@jasonmorse6672]

i have a1990 acura integra bone stock pavement circle track car

[@davidwheeler2405]

Who makes set up plates

[@RMBRacingInc]

We manufacture them.

[@davidwheeler2405]

Would like to purchase a set text me how I'm in good job on video made simple for a dumd ass

[@chadha1412]

What chassis is that?

[@RMBRacingInc]

It is the dirt modified that we manufacture called Custom Chassis. This particular car we built in 2014 and belongs to one of our dear customers.

[@codyblack5490]

What if we zero the digital protractor on a bubble level.

[@RMBRacingInc]

That is an idea. One reason we are so against the "digital" measurements is how unrepeatable they are. Take your angle gauge and tap it. Most will jump and not read the same number again. If you can find consistency with it then it may work for you.

[@codyblack5490]

@RMBRacingInc I have a 4ft level set In a vise. A klien digital protractor. If it turns off or I change the orientation of the tool i zero it on the level before I take a reading. It dose jump if you wack the component your reading off of but it returns to the exact reading and checks zero on the level every time. I do understand what your saying and how using the correct tool gives more accurate setting. But if im using something that is accurate within its self then my settings would be accurate to my tool specifically. Atleast I hope. Also in no way am I professional at alignments

[@RMBRacingInc]

@@codyblack5490 Consistency is the most important. If you do not measure something correctly but you do it consistently the same way and the results are consistent you have half the battle won. If we can help in anyway just let us know.

[@algijura]

thought u have to x1.5 to get total caster

[@RMBRacingInc]

No you do not need to do any math. You just have to measure and read it accurately.

[@user-lv2gb5sh6w]

Just watched this video and there's a lot of good information but some misinformation. The bubble gauge just measures the change in the tilt of the spindle as you do the -20 to +20 degree sweep of the steering. There is absolutely no reason that a magnetic digital gauge placed on the brake rotor or the end of the hub and zeroed at -20 degrees, then swept to +20 degrees can't do the same thing. All you're doing is measuring the change in the angle of the spindle and rotor. Also, I don't know how accurate the 20 degrees needs to be, but I don't think eyballing it by the end of the gauge is very accurate.

[@RMBRacingInc]

We will have to agree to disagree. There is no misinformation here. We have no gain in lying to people. We have a very expensive laser alignment system in our shop and have also done testing with multiple 40K alignment systems. The digital system is not accurate. That is the misinformation. Though bubble gauges have human error in the equation we have time and again proved that they are accurate to within a 1/4 degree or even closer if you have the ability. I will say that turn plates, marks on the floor, or just plain steel plates with 20 degree marks on them can make it more accurate. Bubble gauges have been around for over 1/2 a century and they work. Thanks for the comment.

[@monnieweb]

This guy really don’t understand caster. The 4 degrees he measured with the bubble gauge is not the angle of the spindle, it’s actually the amount of camber changer from the 20 degrees back to 20 degrees forward movement. The 2 degrees on the Digital gauge is the true angle of the spindle. All you really need is a base point that you can reference from week to week. The feel of the steering is the main point. You want the car to pull itself into the corner. You don’t want to have to force it into the corner.

[@RMBRacingInc]

We really appreciate your comment and opinion. As an ASE Master certified technician with degree in High Performance Technology, an instructor of Automotive Technology for 6 years and over 20 years in the motorsports industry I assure you I understand caster. I say that so you can be confident that the instruction we provide is true and accurate. We do not provide instruction to try and sell a product. We are confident that if we help educate not only our customers but racers everywhere that racers will be less frustrated and have better results at the track that ensure the growth of our industry and ultimately our business as well. That said, it appears that you have been swayed by individuals in our sport that like to manufacture and sell "cool" products and they are good at marketing them. Rest assured we have presented caster accurately and if you need to discuss it further please feel free to give us a call or shoot us an email. We are truly here to help and we are glad to explain one on one why a digital gauge cannot be used to accurately measure caster. Thank you again for your comment and have blesses day.

[@monnieweb]

I’ve built and raced many round track cars and rest assured, I completely understand front end geometry. If you take the time to understand what I said you just might learn something yourself. Or, we just agree to disagree. Have a nice day.

[@RMBRacingInc]

@@monnieweb We appreciate your opinion and if we can ever be of further assistance let us know and again thank you for the comment.