Wheel/tire fitment questions

1196 Views 8 Replies 4 Participants Last post by Stanley Yahtzee, Mar 2, 2018

FourSixPony

Discussion Starter · Mar 2, 2018

2018 WRX.. bone stock.. I was looking at wheels, 18x8.75 +35, I was wondering if I could run those and use my stock tires without any rubbing issues?.. sorry if this has been asked before, I’ve been trying to search online but can’t find an answer for the stock tire size. Thanks in advanced.

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zax

· #2 · Mar 2, 2018

What are your OEM tire specifications? There are two different configurations available on the WRX.

Additionally, the offset is a bit low. You might consider a wheel that is closer to OEM offset (+55).

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FourSixPony

Discussion Starter · #3 · Mar 2, 2018

zax said:
What are your OEM tire specifications? There are two different configurations available on the WRX.

Additionally, the offset is a bit low. You might consider a wheel that is closer to OEM offset (+55).

My stock tires are 245/40. I’ve seen people saying that it’s better to run the offset closer to stock, but I’ve seen people running the +35 also, just not in that exact size wheel and a tire that’s not as wide as the 245. I’m having trouble finding wheels that I like, and I really like these but yea, the offset only comes in +35.

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zax

· #4 · Mar 2, 2018

There should be no concern with running that tire on that wheel in terms of sidewall.

FourSixPony said:
but I’ve seen people running the +35 also

That doesn't mean it's correct. In my experience, most people that modify do it improperly. There are disadvantages to running improper offset -- mainly steering feel, suspension calibration, and wheel bearing wear. You might consider finding a different wheel that better suits the design of the car.

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Wrexic

· #5 · Mar 2, 2018

at 18x8.75 +35, assuming you choose an appropriate tire, you'll be just fine as far as rubbing goes. can't speak to steering feel, suspension calibration, wheel bearing wear, or other issues but I haven't noticed anything amiss with mine yet. My current set up is 18x9.5+35 on a 255/40 tire, and i've never rubbed once.

make sure you get the hub rings if your wheel's centerbore is different from the OEM. aluminum better than plastic.

https://www.rimsntires.com/specspro.jsp

^^^that website above will help you get an idea of how your wheelwell clearance/wheel poke will change from OEM to the new wheel/tire setup

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zax

· #6 · Mar 2, 2018

Wrexic said:
My current set up is 18x9.5+35 on a 255/40 tire

Do you understand that the wider wheel changes the demand for the offset? Your experience, unfortunately, is not comparable to a different wheel width.

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Wrexic

· #7 · Mar 2, 2018

zax said:
Do you understand that the wider wheel changes the demand for the offset? Your experience, unfortunately, is not comparable to a different wheel width.

yes that's true, hence why I linked the website above. Ran it based on his OEM specs vs desired wheel, and seems it should be fine (though they didn't have an 8.75" width option), with the only change in clearance being the caliper area, if he keeps the same tire, depending whether he goes 8.5, 8.75, or 8.9. should be fine as far as fender/suspension rubbing goes. I'd recommend he play around with the website and see what works.

That being said, that's only for the clearances/rubbing. I can't speak to how it will affect wear on the suspension, bearings, or how it will change steering feel. but I personally never noticed much difference in feel. I'll let you guys know in however many miles if they caused premature wear on the other parts lol

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zax

· #8 · Mar 2, 2018

Wrexic said:
That being said, that's only for the clearances/rubbing. I can't speak to how it will affect wear on the suspension, bearings, or how it will change steering feel. but I personally never noticed much difference in feel. I'll let you guys know in however many miles if they caused premature wear on the other parts lol

This is exactly the problem. Most people do not stop to ponder what these types of modifications do to the suspension, which would then be operating out of the design parameters.

Suspension is perhaps the most misunderstood component of a vehicle -- just go to a car meet and see what 85% of car enthusiasts have done in the way of suspension modifications. Most of the time, the modifications decrease the performance of the vehicle.

Here are some of the BIG misconceptions:

1. A stiffer suspension always improves performance and cornering. FALSE! A properly calibrated suspension maintains tire contact with the road under varying conditions and under weight transfer. Stiff suspension without good rebound calibration and zero suspension travel is useless (read: most crappy coilovers like BC-BR)

2. Wider wheels and tires mean better cornering. FALSE! The OEM suspension geometry accepts a range of tire widths. Tires that are too wide will keep the suspension struggling to maintain a contact patch and reduce steering feel/performance.

3. Wheels with lower offset increase track and therefore improve performance. FALSE! The OEM suspension is designed for a particular suspension loading that depends on wheel offset. The particular load point of the tire should remain close to OEM meaning that offset should be selected carefully depending on wheel width. Improper offset reduces steering feel, makes the suspension work harder than it should, and puts stress on wheel bearings.

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Stanley Yahtzee

· #9 · Mar 2, 2018

i just ordered some enkei rpf1s in 17x9x45 last night, according to that tool linked above my backspace is only .1" more with a 265 wide tire than my stock wheels are with 235s. is that considered ok or am i doomed?

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