Aftermarket Wheel Fitment Guidelines

Recently I've been reading about PRIUSchat forum members choosing different types of aftermarket wheels for their Prius Primes. There seems to be some "confusion" about how things work concerning fitment versus what doesn't work, so here's a basic fitment guideline to use when considering your new aftermarket wheels. Take the time & do your research before you buy into your new wheels; there's nothing worse than spending the big bucks to then realize you should've bought something else. As a reference, the Prius Prime has a stock OE wheel size of 15x6.5" ET40 & a tire size of 195/65-15; overall diameter (OD) is 25.0".

1) Wheel Diameter:
a) 15" (Prime OE)
b) 16" (Plus One)
c) 17" (Plus Two)
d) 18" (Plus Three)

Wheel Width:
a) 6.5" (Prime OE)
b) 7"
c) 7.5"
d) 8"
e) 8.5"

3) Wheel Weight:
Less is more, meaning try *not* to buy into heavy wheels if it can be avoided. IMO this would be any wheel above ~18.5 lbs in weight; 17 lbs or less would be great. One of the big problems with buying aftermarket wheels is much higher wheel weight: higher wheel weight (unsprung weight) *negatively* affects the chassis in many ways. Poor fuel economy would probably be first, other issues will be sluggish handling, slower acceleration & braking & increased strut/shock wear.

4) Bolt Pattern:
A Prius Prime has a bolt pattern of 5 X 100, this means there's 5 bolts/studs & it has a pitch circle diameter of 100mm's. Anything Less Or More Won't Work.

5) Wheel Offset (ET) / Backspacing:
Offset is the distance from the center of the wheel to its mounting surface. Offset / ET is measured in millimeters (mm) and a Prius Prime's stock ET is +40. Trying to stay close to this number would be a good starting point. I'd recommend staying within 5mm's of stock if possible, which means an ET of 35 to 45. Backspacing (a slightly older method of doing the same thing) is the distance from the inside edge (back side of wheel) of the wheel to the mounting surface. Also, wheel backspacing is measured in inches while offset is measured in millimeters.

6) Spacers:
Spacers can typically be used for two reasons. First, to help correct a wheel that doesn't already have the proper offset. An example of this would be if you bought an aftermarket wheel with a ET45 and needed or wanted to correct it back to the Prime's OE ET40. A 3mm spacer would get you close by making it a ET42 & a 5mm spacer would get you all the way back to ET40. The second reason is for aesthetics. Some people use spacers to push the wheel/tire farther out giving the appearance of a fuller wheel well. Thin 3mm (1/8") spacers can be used on any Prime without modification. If you need something bigger like a 10mm spacer, you'll need to buy & install longer wheel studs to accommodate the thicker spacer. When shopping for any Prime spacer, realize that you can buy them with the exact 5x100 bolt pattern & 54.1mm hub bore, which should be your first choice.

7) Hub Bore / Hubcentric Rings:
The stock Prius Prime hub bore is 54.1mm's in diameter. This is important because most aftermarket wheels will have a much larger internal hub bore of roughly 73mm's. For example, your stock Prime wheel has a hub bore that's also 54.1mm's. This means the stock wheel is being centered on the hub *before* you tighten down the wheel nuts. The combination of the same hub bore and wheel bolt/stud tightening gives you the best chance for a perfect rolling wheel/tire combo, as relying on *just* the 5x100 bolt pattern does not always equal a good rolling wheel/tire. Knowing all this means it's a very good idea to use a hubcentric ring to convert a generic aftermarket wheel's bigger hub bore to the smaller 54.1mm Prime hub bore. Hubcentric rings are a non-wear item,
so it really doesn't matter if you use metal or plastic.

8) Tuner Wheel Lug Nuts:
Many aftermarket wheels require *tuner* lug nuts for mounting, this is especially true if the wheels you bought are double cut for two different bolt patterns. An example of this would be if you bought a wheel with a 5x100 and 5x114 bolt pattern, it's a virtual guarantee that you'll need to buy tuner lug nuts. Tuner lug nuts are simply smaller diameter when compared to your OE Prime lug nuts, thus they fit inside the aftermarket wheels smaller cut bolt pattern hole. If you're not sure about what style lug nut to use & can't easily find this info, please contact the wheel manufacturer before you try to mount your new aftermarket wheels.

Here are my two favorite wheel/tire calculators. Play with them by entering in different combos.
a) Rim & Tire Size Calculator. Custom Offsets - Wheel-Size.com

b) Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit


Let's sum things up from ALL 8 categories:

1) Pick a wheel diameter that suits you & your style, maybe a 16" or 17".
2) Pick your desired width, maybe a 7".
3) Try to choose a lighter weight wheel if possible; call the manufacturer if you can't find the weight.
4) Absolutely buy a 5x100 bolt pattern wheel.
5) Try to get your offset close to the Prime's OE ET40 if possible.
6) Add spacers if necessary, try to buy 54.1mm hubcentric & 5x100 bolt pattern if possible.
7) Give great consideration to installing hubcentric rings if your new wheels have a hub bore bigger than OE.
8) Buy tuner lug nuts when needed, stock Prime OE lug nuts won't work for all aftermarket wheels.

Good luck,
Rob43

 

Tire guide coming soon...


Rob43

 

^ They're very nice, your Prime looks great !


Rob43

 

No, it's not a problem.

If we were still living in the 1970's you'd have a valid concern, but computers, industrial laser measuring tools, & CNC machining techniques provide us with very straight & true aftermarket wheels today.

I'd actually much more concerned about using a Toyota factory OE 17" wheel from another model car as my planned upgrade, because factory wheels are overbuilt in terms of strength, kinda like a tank. That of course sounds like a great thing, but OE wheels are HEAVY. Heavy wheels are a bad thing for almost any car (unsprung weight), let alone a Prius Prime where having a lightweight wheel & tire is king.


Rob43

 

If modern aftermarket wheels were an issue, you'd read about it on every different car forum. But they're not because of the science used in modern manufacturing techniques.

In the end, you should only buy what you're comfortable with...


Rob43

 

Again, you should only buy what you're comfortable with...

Rob43

 

Bought my new General G-Max AS-05 light-ish weight 17" tires.

I decided on a 205/50-17 size (25.1 OD) which works well with a 7" wide wheel, these are on the lighter side at
19.2 lbs according to General. These are not a LRR tire, but the flip side of that is these are a very good ultra
high performance A/S tire with amazing grip in both the wet & dry so the *fun factor* is really there when you want it. For those that don't know, General Tire is owned by Continental Tire.


Rob43

 

Teaser....

Rob43

 

First question: Are you saying you want to run a 17x8 et30 on the Front & a 17x8.5 et30 on the Rear ???


Rob43