Hey, it's Freddie with CJ Pony Parts. When shopping for aftermarket wheels, two common measurements
that you're going to come across that a lot of people get confused by, are offset and back
spacing. In today's video I'm going to show you how to find offset and back spacing and
also help you understand what they are. In this video we're going to be working with
this TSW Bathurst Wheel. It measures 18 by 8 inches and has 40 millimeters of offset and
6.07 inches of back spacing. I'm going to start off by showing you how to find the
true width of the wheel. If you recall earlier I said this is 18 by 8 wheel which means it's
8 inches wide, but not the actual width of the wheel. The 8 inches means from bead to
bead. This is for the tire. If you actually measure the width of the actual wheel you'll
get 9 inches which is not right. To find that 8 inches you measure from the bead to the bead.
And that is eight inches. If you're shopping for wheels or if you have a set of wheels laying
around and you want to find the true width of them you're not going to measure from the outside to
the outside. You measure from the bead to the bead and that is the true width of the wheel. Now that
you know what width is, we're going to talk about offset. Offset of the wheel is the relationship of
the face of the hub to the centerline of the wheel. So imagine if this line right here is
the center of the wheel, zero offset would mean the face of the hub on the inside of the wheel
is dead center in the wheel. If the face of the hub moves towards the front of the wheel, that's
positive offset. If the face of the hub moves towards the rear of the wheel or the inside
that is negative offset. In the case of this wheel this wheel has 40 millimeters of positive offset
which means it's 40 millimeters towards the front of the wheel. So we know what offset is, now we're
going to talk about back spacing. Back spacing is the amount of wheel that sticks out past the face
of the hub. Since this wheel is eight inches wide it has 40 millimeters of offset or an inch and a
half of offset so it's going to have six inches of back spacing. There's six inches of wheel from
the face of this hub sticking out. Now that we know what back spacing and offset is I'm going
to show you how to find them. To find the offset you're going to want to put the wheel on a flat
surface and then measure to the surface that it touches. We're using this cardboard because
it's completely flat and it goes right across the top of the wheel, giving us a nice flat line.
We're now going to measure from this cardboard down to the table that the wheel is sitting on.
And as you'll see, it is exactly 9 inches. Now we don't need the true width of the wheel for
this like I stated earlier, it doesn't need to be 8 inches but this measurement is from
the bottom of the wheel to the top of the wheel and this is 9 inches. So write that down, 9 inches.
So now that we know the actual width of the wheel is 9 inches, as you can see right here,
you're going to need to find the center of the wheel to find the offset. So just simply divide
this number in half so half of 9 is 4 and a half so the very center of this wheel is at 4 and a
half inches. For this part we're going to measure from the face of the hub to the top of the wheel.
So from the face of the hub to the top of the wheel, you can see it is exactly six inches. So
six inches from the face of the hub to here is six inches of back spacing. So now we're going
to find how much offset this wheel actually has. We got our measurement of nine inches wide, that
is the width of the entire wheel, and then we divided that number in half to find the center
line. That's four and a half inches in the very center. And then we found out we had six inches
of back spacing and the very center of the wheel is four and a half inches so six minus
four and a half gives us an inch and a half or forty millimeters. So now the hub is right here
and so now since this is further towards the front of the wheel it's positive offset so we have 1.5
inches or forty millimeters of offset. If this were the opposite direction though, if the hub
was back here, it would be negative offset. So now that we know how to find offset and back spacing,
what are the practical uses? Why do you even need to know those numbers, how's it going to help you
at all? Well we'll talk about offset for right now. Now with offset, with a positive offset you'll get
more of a flush flatter look just like this wheel. It's got positive offset so the hub is closer to
the front and as you can see the spokes have a very slight dish but overall it's kind of flat
actually. If you want more of a lip on your wheel or a dish or a bold look you're going to move the
hub back so you're going to get negative offset. It's going to take the hub back and everything
is going to go in. Offset can also affect how much wheel sticks out past your fender or how
much wheel doesn't stick out past your fender. In this case this wheel also has 40 millimeters
of positive offset, so that means the hub is just a little bit further from the center out towards the
car, which means not much of the rim is sticking out. If the wheel had a lot of negative offset the
hub was further back in, more of the barrel will be sticking out and it will come out past the fenders.
The more positive offset you have, the further the wheel is going to be in from the fender, the
more negative offset you have, the further this wheel is going to stick out. We have the car up
in the air now so we can show you exactly what back spacing is. Back spacing is super important,
especially if you're going to get wider wheels and I will show you why. This wheel has six and
a half inches of back spacing, and when I turn the wheel watch how close it comes to hitting
right here. That comes within about maybe three quarters of an inch maybe even half an inch to
almost hitting right here, so like I said this wheel has six and a half inches of back spacing
and as you saw it came within about a half an inch maybe three quarters of an inch to having
contact right here so if you either got a wider wheel or change the offset to where you have more
than six and a half inches of back spacing maybe seven even seven and a half, you'd probably run
into clearance issues which is not good. So when shopping for wheels make sure you know how much
offset you can have or how much offset you want. So in this case six and a half inches of back
spacing on this wheel is absolutely perfect. If you wanted to run any more back spacing
you're probably going to run into clearance issues so when shopping for wheels make sure
you know how much back spacing you can run and hopefully this helps you out. So I've showed you
what offset and back spacing is and also how to find it. Now all that's left is for you to go out and get
some awesome wheels. We have tons available at CJ Pony Parts.com and I'll see you next time!