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Discussion Starter · #1 ·
I'm a complete noob when it comes to wheels & tires. I just got my new bone stock 2012 xB. My question is can I put bigger (maybe 18") wheels and tires without requiring any adjustment to any other component in the car? I was reading online and it says that if you go bigger, it may throw some sensors and saftey features off. What's the deal with xB?

Thanks :)
 

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No problem, just make sure the combined height of tire and rim are very close to OE. The other primary consideration is if you increase the width of the tire from OE, then you could run into fender clearance issues, particularly when turning. Another consideration is typically, the taller rim plus lower profile tire weighs more than the OE, so the usual experience is gas mileage and acceleration go down, whereas braking distance goes up, however; the cool factor is definitely a win :)!
 

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To Trevor's point, everything has a trade-off. The factory setup is probably the most efficient for the vehicle but looks lame. Style is up to the individual but fact of the matter is if you don't want to trade one thing for another, you have to leave it stock.

I have definitely lost mpg and increased the stopping distance. AND my MPH is off by about 2 mph at 60 and 5 mph at 75.....this ratio increases by mph. I GPS'd a few trips on the highway to and from work and benchmarked some specific mph readings and just adjusted my driving accordingly.

Gotta pay to play.
 

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Discussion Starter · #6 ·
MiniFridge, thats exactly how I want mine to looke like :) very nice.

So what about the scion website? when you build&price, they give you option for bigger wheels. Does the dealer adjust the mph and braking issue after installing bigger wheels? I understand mpg issue will stay.
 

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I'm not sure about either. But I would bet that if you asked Toyota, they probably recommend their TRD Big Brake kit with the TRD 19" wheels. With that being said, it's not dangerously different you just have to account for the difference and be aware of it. I think the added rotating mass with my wheels is about double the factory wheel/tire setup and they are larger overall diameter because I wanted 20's.
 

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The stock brakes are already "overkill" for a vehicle the weight of the xB2. It's designed for bigger rims, but come w/ the minimal size (16s) that will fit over the brakes.
Unless you go for massive, heavy rims, the xB's brakes are sufficient. W/ lighter-than-stock rims/tires, the xB is downright scary-fast to stop (a good thing for me).
 

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So what about the scion website? when you build&price, they give you option for bigger wheels. Does the dealer adjust the mph and braking issue after installing bigger wheels? I understand mpg issue will stay.
My 08 RS5.0 XB came with 17" alloys from the factory, my speedometer is 2MPH faster than my actual speed.
 

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I'm bit of a perfectionist and this is definitely 'turning me off' :confused: So there is no way to have correct speedometer after going big?
Please, it's just arithmetic. Here's a calculator to help you find a tire/rim combination that gets you as close as practical to OE :)!

Tire size calculator

It's purely your choice what you go with, no cards held back.

I had to choose tires for winter driving and the final height unquestionably throws off my speedometer. My choice was to go with a slightly taler tire on my OE steel rims, but the error is less than 5% and it works fine for winter here in DE (just have to keep the speedometer error in mind). Different folks will have different considerations on this topic, you just have to decide what works for you :)!
 

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I'm bit of a perfectionist and this is definitely 'turning me off' :confused: So there is no way to have correct speedometer after going big?
As a perfectionist, the whole thing with the speedometer is not quite accurate from the factory. As the OEM tires wear down,they get smaller and the reading changes. If the error with bigger wheels is only 2% (that would be 2 mph @ 100 mph), I ,myself, wouldn't have a problem with that.
Car companys can't really controll what size wheel/tire combinations owners put on their cars other than clearance considerations, therefore speedometers are really just approximate indicators of ground speed. If one wants really accurate speed,maybe using GPS,just saying.
 

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Discussion Starter · #13 ·
Ok, that calculator tells me that if my stock tire is 205/55-16 then for 18" wheels, I should go with 215/40-18 tires to keep the speedometer best accurate possible. What you guys think of 215/40-18? Any other 'issue' I should know about this size?
 

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Mine is barely off and I've got 235/45R17 it's not a big deal if you're 2ish miles off.
 

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Ok, that calculator tells me that if my stock tire is 205/55-16 then for 18" wheels, I should go with 215/40-18 tires to keep the speedometer best accurate possible. What you guys think of 215/40-18? Any other 'issue' I should know about this size?
Also check your wheel offset. A nice calculator is at
Custom rims, wheel tire packages for your ride - RIMSnTIRES.com
click the Fitment Guide link on the left side under Tools, then enter your car, then click Compare Sizes near the top of the new page. You can compare the stock 16" wheel/tire to whatever new wheel/tire combo you are considering. The tool will estimate wheelwell and brake clearance. The tool will also estimate % error for the new wheel/tire combo.
 

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Another consideration to think about is the factor of hydroplaning. When tires get wider,the resistance to hydroplaning changes.So just remember not to go fast when the weather is bad. It doesn't take much water on the road to reduce traction.
Be safe.
 
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