Ever get confused by all the numbers telling you the specs and dimensions for the wheels on your truck? Adding to the confusion of all the different terms is the fact that both wheels and tires use the silliest combination of metric and standard for their measurements.
So let's clear things up!
For wheels, you have four main measurements: diameter, width, backspace and offset. What are they? Why are they important?
In this post, we're going to take a look and discuss how they affect both the look and performance of your truck, specifically for Toyotas.
Diameter is pretty simple: it's how large the wheel is across the circumference.
The larger the wheel, the shorter the tire sidewall will be. So the first question is, how short do you want your sidewall? For off-road, you want a larger tire sidewall to allow the tire to wrap around obstacles and give more traction. For street, you want a shorter sidewall so you get better handling as the tire won't deflect as much around corners.
You also need to pay attention to what size wheel will fit your vehicle as brakes can come into contact with wheels that are too small.
As we work mostly on off-road Toyotas in our shop, we typically install 17” rims on Tacomas and 4Runners. Some 16” rims can fit the Tacoma, but not the 4Runner.
Width is probably even simpler than diameter. It’s the measurement of how wide the rim is. You want to select a rim width depending on what size tire you're installing.
If your rim is too wide for your tire, then the bead (the part that boa bra bra) can pop off really easily.
On the other hand, if your rim is too narrow, then that will change your tire profile and give worse traction and bad wear patterns.
Keeping with our Toyota theme, we typically recommend a rim around 8.5” that will fit most 33s and most 35s.
Backspace is the measurement from the wheel mounting surface to the inside edge of the rim. This is important because if your backspace is too high (wheel further into the wheel well), then you can rub on the UCA, spindle or frame, depending on your tire size.
A low backspace on the other hand will make the wheel “poke” out of the wheel well, which might be a cool look but is going to affect the scrub radius and cause the tire to rub on the fenders or firewall.
Backspace is affected by how wide the rim is. So if you’re running an 8.5” wide wheel with a 4.5” backspace, then the wheel will be 4” outside of the wheel mounting surface. Of course, where and how much your tire rubs depends on what size tire you’re running.
I typically recommend somewhere between a 4 to 4.75” backspace. However, some people like lower backspace to get that staaaaaaaance.
Our final measurement is offset, which is linked directly to backspace. Basically, offset refers to how far the wheel mounting surface is to the wheel’s centreline. This is the only spec that is in MILLIMETRES for NO REASON.
A lower offset means a lower backspace. Common offsets for off-road people are 0 or -10. However, I’ve seen people who want lots of poke who go all the way down to -38.
Personally, I prefer to use backspace over offset because it makes more sense to me, but offset is very similar. Everybody has their preference, but people that prefer offset are just a little weird.
That’s a wrap
So that’s it! That's the basics on wheel fitment. Hopefully that helped to clear some of the cobwebs and make sense of a topic that's been way overcomplicated.
I’d love to hear from you. What size wheel do you run? Do you prefer offset over backspace? (Why????) Do you like a bunch of poke or prefer a more conservative stance?
Let me know below in the comments and make sure you check our YouTube channel where we share more useful content like this. Or if you're looking for wheels yourself, be sure to check out what we offer!