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Rim Sizing?


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16 replies to this topic

#1 Urban Coyote

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Posted 29 November 2012 - 09:12 AM

I'm going to start looking for a nicer set of summer rims for my new 2009 Impreza. As long as the bolt pattern is 5 x 100 (or 5x4) I should be good regardless of the rim size...15 instead of 16 for instance?

What does the '100' stand for exactly and is there any wiggle room in that measurement for rim sizes?

The stock tire size is 205/55 R16. If I were to find a very nice set of 15 rims would I would be safe to run 195/65 R15, or a 205/60 R15 on the car?

Thanks!
UC

#2 1 Lucky Texan

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Posted 29 November 2012 - 09:28 AM

well, the new rims 'should' be hub-centric (or corrected with an adapter) and have the correct offset (within a few millimeters anyway). And they must clear the caliper. Going down in size might mean caliper interference.

a shop like Tirerack or Discount Tire would likely only recommend correctly sized rims. shopping the used market, you will need to confirm fitment.

you might wanna read some of the 'sticky'/FAQ threads here; http://forums.nasioc...isplay.php?f=88

no wiggle room on the 5x100 unless you somehow change your hubs. I THINK the 100 is the diameter of the circle on which the center of the 5 lug holes are positioned. basically, it's the spacing of the lugs. Some newer Soobs have larger spacing so, be careful.

Edited by 1 Lucky Texan, 29 November 2012 - 09:38 AM.


#3 Urban Coyote

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Posted 29 November 2012 - 09:36 AM

That's just it....what exactly are all of the measurements I should be concerned with? When you say "hub-centric" what exactly do you mean and what is the correct number for a 2009 impreza.... same with offset?

Sorry, I never concerned myself with rim sizing before so this is a new learning curve for me right now. Doing a general Google search for impreza rim size came up with surprisingly little info.

#4 1 Lucky Texan

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Posted 29 November 2012 - 09:45 AM

if a rim is positioned/centered by close fitment around the hub - it's considered hub-centric. If some rim from a different car is fitted, the hole for the hub might be smaller or larger. larger 'might' be OK - but an adapter could be required - otherwise you are relying on the lugnust to center the rim (lug centric) and take all the load. Might be OK - but not advisable.

The offset is basically how the wheel is positioned to place the load directly under the bearing. If the offset is wrong, the rim will be pushed-in or pushed-out and, in addition to possibly rubbing on the strut/spring , or the fender, it puts an offset load on the wheel bearing which might lead to early failure.

much of this info applies; http://en.wikipedia....ki/Wheel_sizing


most people would opt to +1 the rim size for new summer rims. so, look at 17 or stay with 16.

Edited by 1 Lucky Texan, 29 November 2012 - 09:54 AM.


#5 porcupine73

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Posted 29 November 2012 - 10:38 AM

Often the aftermarket wheels will come with aluminum rings to go over the hub to try to make the wheel center correctly on the hub. So that they don't have to stock 4000 different wheel types it seems like they usually go with the largest hub bore on any vehicle that wheel will fit, and also double drill the lugs, so like it might be drilled for 5 lug 100mm lug spacing and also 5 lug 114mm or some other size.

#6 1 Lucky Texan

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Posted 29 November 2012 - 10:57 AM

Often the aftermarket wheels will come with aluminum rings to go over the hub to try to make the wheel center correctly on the hub. So that they don't have to stock 4000 different wheel types it seems like they usually go with the largest hub bore on any vehicle that wheel will fit, and also double drill the lugs, so like it might be drilled for 5 lug 100mm lug spacing and also 5 lug 114mm or some other size.



the SSRs and the Enkeis I've had were both made 'for' soobs and had no adapters or xtra holes.

But i have seen aftermarkets like you describe.

(does Enkei make the OEM rims for subaru?)

#7 Caboobaroo

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Posted 29 November 2012 - 09:38 PM

Your car has the 5x100mm like you said. The 5 is the number of wheel lugs and 100mm is the distance between two studs. Not two studs next to each other but with one inbetween them. There are some other variables that you can look further into like wheel width and backspacing.

Really you should be able to fit a 16", 17", or an 18" without much issue. It also depends on the size of tire you want to run as well. The larger diameter of wheel you go, less sidewall of the tire. It's great for handling purposes but it can also give you a slightly harsher feel of the road. Also keep in mind how much tires will cost you over the years and sizes can vary in price considerably.

Tire Rack is always a good place to start. They can ship you a wheel/tire package with TPMS sensors already together and you would just need to bolt them on and go.

#8 edrach

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Posted 01 December 2012 - 11:22 AM

No one has mentioned rim width. Most of the OEM wheels are 6 to 6-1/2 inches in width (for 16" diameter). I purchased a set of nice RS rims and mounted tires on them and found the rear tires rubbed on the struts. I didn't realize the RS rims were 16x7" and would cause the rubbing. A pair of 5mm spacers in the rear solved the rubbing problem.

#9 wentz912

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Posted 01 December 2012 - 01:15 PM

Five lug patterns are actually measured from the center of one stud, to the outside edge of the stud two over from it.

#10 Urban Coyote

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Posted 02 December 2012 - 05:36 PM

Thanks for all the input.

I was hoping to potentially size down by one rim size as tire for 15's are quite a bit cheaper than 16's around here. I don't skimp in the quality of the tires I buy, but was hoping to potentially save a little on the size. My new Impreza came with pretty much the cheapest tires on the market so I'll probably be buying both a new summer and winter set in the next year.

Unless anyone has experience with Goodyear Nordic winter tires? Are they any good?

Edited by Urban Coyote, 02 December 2012 - 05:59 PM.


#11 edrach

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Posted 02 December 2012 - 07:12 PM

Thanks for all the input.

I was hoping to potentially size down by one rim size as tire for 15's are quite a bit cheaper than 16's around here. I don't skimp in the quality of the tires I buy, but was hoping to potentially save a little on the size. My new Impreza came with pretty much the cheapest tires on the market so I'll probably be buying both a new summer and winter set in the next year.

Unless anyone has experience with Goodyear Nordic winter tires? Are they any good?

My choice for winter tires are Hakkis (Nokian), Hankook and Toyo in that order (all studless for me). Summer tires I've settled on the Conti DWS all weather tires (don't think they come in a 15" version).

#12 porcupine73

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Posted 02 December 2012 - 08:04 PM

You would need to make sure the 15" wheels will clear your brakes of course.

#13 Setright

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Posted 03 December 2012 - 11:50 AM

I would strongly recommend sticking with the factory 16 inch rims.

Not meaning to be cocky or offensive, but since you know little about rim fitments and measurements, you are likely to run into other problems...that will cost you more than you stand to save on lower-priced tyres.

#14 Urban Coyote

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Posted 03 December 2012 - 01:37 PM

Nope, you don't sound cocky, but it also has to be understood that in order to learn you have to ask questions and try to gain experience. You can't learn by remaining mute and expecting to gain knowledge by osmosis alone. That's why I ask lots of questions...to gain knowledge so I can make the best choices possible. If you don't ask, you can't learn. I'm sure most of the Subaru gurus on this board didn't start out as experts.

#15 Setright

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Posted 03 December 2012 - 05:00 PM

Indeed, I agree :D

#16 Setright

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Posted 03 December 2012 - 05:14 PM

Back on track:

I don't think 15 inch rims will clear your brakes on the front. They might JUST fit, but the balancing weights that are used on the rims might foul the brake caliper. All depends on the balance in the tyre and where the weights need to go. It also depends on the rim design, some spokes will clear, some might not. The brand "Speedline" make 15 inch rims that fit over the old Turbo brakes - 295mm discs, I expect your car has 277 discs.

I think Texan already mentioned it, but ET is another very important measurement. This the distance from the geometrical center of the rim, to the face where it makes contact with the hub. This measurement affects how far in, or out, the wheel will sit. Subaru's generally run 50-55mm. This is quite a large ET and allows for longer suspension arms, meaning less wheel geometry changes as wheels move up and down.
You do NOT want to stray far from the standard value on your car, which as I recall is 55mm.

So...15Jx6.5 ET55 5x100 is probably what you are looking for.

15 inch outer diameter
J - the shape on the "shoulder" on the rim where the tyre bead rests.
x times
6.5 inch rim with
ET55 "rim offset" of 55 millimeters
5 bolts
x100 spaced 100mm


You might be able to make it work with a 6.0 inch rim, or maybe 7.0. The important thing is to have a rim width of approximately 80-90% of the tyre width. This allows the sidewalls to work as designed.

You can get away with an ET of 50, which will move the wheel out by 5mm, compared to stock - and give you a better chance of the spokes clearing the brake caliper, but the inside diameter is still gonna be tight.

#17 Urban Coyote

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Posted 04 December 2012 - 05:36 AM

That's fantastic, thank you very much!

I've learned a lot and will make sure to take care when searching for a new set of rims. Onward and upward as they say :)




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