This is a demonstration of measuring what is referred to as stud circle run out the studs were
referring to are these wheel studs and everyone assumes that these studs of which there are five
here on this axle flange they assume that these studs are equal centered or equal distance from
the center of this axle shaft out to the hole that they were drilled the hole drilled in the
axle a flange here where you pull the stud through but as it turns out these are not on a perfect
centerline with the centerline of the axle shaft and the difference between the holes the distance
between the holes in the center of the axle shaft is called studs circle run-out so wheel studs and
what does that have to do with anything? well if you have wheel stud circle run-out instead
of these studs just rotating nicely as you drive down the road they'll be kind of orbiting up and
down kind of like an egg rolling down the road and it can cause your tire and wheel assembly
to be moving up and down as you drive down the road also which can cause a first order tire
speed related vibration so for vibration diagnosis this is a check that you would do if your tire and
wheel assembly run-out was excessive on the vehicle but not off of the vehicle so see my
other YouTube video on checking tire and we'll assembly run out on the vehicle but if it has
excessive run out while it's bolted up to these wheel studs but then you Center it on a wheel
balancing machine and check the run out there and the run out is acceptable then the problem must be
either in the wheel studs or in this circular center part of the axle flange here where the
wheels are supposed to be centered now all factory wheel are hub centered which means this Center
ring here is what the wheels are centered on - and the wheel studs just simply clamp it down to this
axle flange but on a lot of aftermarket wheels to be universal they don't just use this hub to
Center the wheels instead they use the wheel studs to Center the wheel, well if theirs wheel start
run out and that's how you're centering the wheel then the wheel of course is going to be moving up
and down as you drive down the road so I'm going to demonstrate here how to measure wheel stud run
out and go from there okay so I've got a dial indicator set up here as you can see and I've
got the dial indicator plunger with a wide tip let me zoom in here so you can see the wide tip
there we go so this black tip that you see here is a really wide tip it's part of a kit a contact
point set that I have purchased from Starrett contact points debt set number 25R and in this
kit it comes with a big selection of tips that will fit on a dial indicator and it's a wonderful
set but this this tip here is part of this set and I like this tip or the roller tip the roller tip
would work great also the Starrett 25W but either of those work great because they will glide back
and forth easily over this wheel stud so what we want to do is find the high spot of every wheel
stud here and compare it using the dial indicator to see what is the difference between the highest
high spot and the lowest low spot so the way that we do that is I've got the plunger set up on the
dial or on the with the wheel stud so I'm just going to rotate the wheel stud or the axial one
way or the other and I'm need to find the high spot of the wheel stud now notice if you watch
this dial indicator as it comes around it'll get to a point where it stops and then it'll change
directions but I did not change directions at that point where it stops getting real close we passed
it right there where I've got the dial indicator zeroed that's the high spot of this stud and then
if I keep going then it goes back the other way so one more time I did not change directions but
notice the dial indicator goes towards zero stops turns back around and goes the other way and you
need to for consistency's sake just because of how the dial indicator is mounted I’ve got a magnetic
base holding this on you need to be rotating the flange and with the wheel studs in the same
direction when you check each wheel stud so right there I’m going to zero it okay so now I’m going
to roll the axle shaft until it gets to the next wheel stud over here okay here we go so now we're
going to find the high spot of this wheel stud notice it is looks like about three thousandths
of an inch different it's high spot is three thousandths of an inch different than the previous
one so we've got three thousandths stud circle run out so far so let's continue on around to the
next wheel stud so you've got to do this on every single stud I’ve found problems on vehicles that
couldn't be fixed the so called can't be fixed vehicles that were about to be purchased back
by doing this very check there was a vibration they balance the tires and wheels assembly of
course and couldn't find any problems but okay there's our high spot right there so about four
thousandths of an inch difference between that first stud and this one and it ended up not
being the tires and wheels at all it was the hub assembly that the hope and bearing assembly on
the front of a Dodge truck that ended up having excessive stud circle run-out okay check this one
up too far this one's a little closer only about a half thousand difference and then let's check the
last one come back around here by the way you may be noticing that I'm checking this the stud simple
run out deep inside here where the wheel actually sits you don't want to check it out on the end
of the stud because that's not where the wheel sits and you will get more run-out out on that
end of the stud because they're never in perfectly straight so here we go let's check this last one
and it looks like it it's about a 1 thousandth of an inch difference so between or by comparison on
the 5 wheel studs we started by zeroing the dial indicator on this stud and then we had
three thousandths four thousandths about two and about one and then back to zero here so the holes
that were drilled for those wheel studs to go in are contributing about a four thousandths run out
to the tire and we'll assembly as you drive down the road and the maximum allowed specification
on these typically is around ten thousandths of an inch but every vehicle manufacturer may have
their own specs so be sure to look it up in the service information but typically ten thousandths
is the maximum now you can do what's called match mounting so if this stud was zero and this one was
four thousandths less that means this was the high spot this is the low spot if you can find the high
and low spot on your tire and wheel assembly you can rotate the wheel assembly on the studs to try
to reduce overall tire and wheel assembly run out and that's why if you ever take a hub cap off or
go to take lug nuts off and you see a wheel stud that's got a paint mark on it and a brake rotor
drum or whatever that has a paint mark on it and a will maybe that has a paint mark on it somebody's
gone to the trouble to match mount those and it's a good idea to always put those back where they
were because even if you didn't break anything imagine putting it a 180 degrees off of match
mounting you could actually cause a vibration to occur that was not there before you worked on it
and of course every technician hates hearing the customers say ever since you worked on my
car it's got this vibration or whatever has gone wrong and when in fact it may you may have caused
it by undoing the match mounting work that someone else has done so this works it doesn't matter how
many wheel studs you have just check the highest check the high spots of each stud compare the
highest one to the lowest one anything over ten thousandths of an inch the entire axle shaft or
hub and bearing assembly on the front or rear if it's a front-wheel drive would need to be replaced
and just a word of warning just because it's new does not mean it is good I mean this was new at
one time on that Dodge truck I was telling you about we replaced the hub and bearing assembly and
the replacement one was worse than the one we took off it ended up taking a third hub and bearing
assembly and this is a 3/4 ton four wheel drive truck the left front hub and bearing assembly it
took a third one before we got one that had stud circle run-out within specifications so this has
been a demonstration of measuring stud circle run-out for the purpose of reducing first order
tire speed related vibrations by match mounting tire and wheel assemblies to the wheel studs