I ordered my xB last Friday and I already have a list of mods for it. First things First - i'm going to put 17" x 7.5 rims on it but I am wondering if this will affect the odometer reading?

My previous car had bigger rims and I never had the odometer looked at. When I was doing highway speeds (60mph), the speedo would read that im doing 80 mph. In addition to that, the odometer would move up 1 mile even though I hadn't traveled a mile. I would drive, lets say, 8 tenths of a mile but the odometer would pick it up as 1 mile...

Having said this, i dont want this problem on my new xB. Does the odometer/speedometer components needs to be changed/modified when i put on bigger rims? I know you can compensate by changing the size of the tire, but i dont want to risk it. along with 17" rims i want to be riding on a big tire (potholes here in nyc are insane....)... anybody running this sorta setup have any comments?

i appreciate your help,
- sh00k

 

There are no speedo/odo components to change out to correct for the problem if you change to a TIRE that has a larger (or smaller) outside diameter than the OEM tires.

The only way to keep from having this problem is to make certain that the outside diameter of your tires remains the same as the stock tires. This means when moving to a larger wheel diameter on must move in turn to a lower profile tire to maintain the overall size.

Keep in mind, too, that the electronic odo on the xB appears to be a few percent LOW in it's readings while the speedo face is marked a few percent high...

(The speedo can actually be corrected with a new speedo faceplate that has the markings shifted slightly so that they are correct - I don't know of any commercially available replacements for this purpose, though.)

Check around in the 'Tread and Butter' forum here at ScionLife, or possibly even in the tech section. I suspect there are tables showing what size tire one must use with a given wheel size to maintain a reasonably accurate odo...

 

In terms of overall diameter, the closest 17 inch tire size to a stock 185/60/15 is a 215/40/17. Granted the selection wont be as large as say, a 205/45/17, but it will be much closer to the correct diameter.

 

I saw what tomas is talking about but can't remember where......anyway ........i found that the 205/40/17 rim and tire selection would keep the diameter the same as the stock outside diameter and it seems all normal since i made my upgreade........good luck .!!

 

Hey - does the 215/40/17 size tire have good meat on it? I ask this because NYC potholes are insane. I had a friend get two flats (passenger side front + rear) by hitting one speedbump!!! He was riding on 17" rims with very thin tires - i dont know the size...

 

The 205/40/17 tire is actually smaller than stock. Not by much, but it is.

The 215/40/17 is a closer match if you have to have a 40 series. The sidewall when calculated out is 3.39". For comparison the sidewall on the stock 15" wheels is 4.37".

If you want a slightly wider tire you can go with a 225/35/17. These should work really well with your 17x7.5 wheels. They are an even closer match to the stock tire diameter than the other two listed options. The sidewall on these tires calculates out to be 3.1".

So if you want more sidewall, go with the 215/40. If you want a wider tire that closest matches your stock diameter, go with the 225/35. And most importantly, make sure your wheel has enough backspacing/offset. On a 7.5" wide wheel you need at least +35mm offset in order to clear your fender.

Hope that helps. Good luck.

 

Stock Tire - 185/60R15 >Search Tires Tire 1 - 205/40R17 >Search Tires Tire 2 - 215/40R17 >Search Tires
Section Width: 7.28 in 185 mm
Section Width: 8.07 in 205 mm
Section Width: 8.46 in 215 mm

Rim Diameter: 15 in 381 mm
Rim Diameter: 17 in 431.8 mm
Rim Diameter: 17 in 431.8 mm

Rim Width Range: 5 - 6.5 in
Rim Width Range: 7 - 8 in
Rim Width Range: 7 - 8.5 in

Overall Diameter: 23.74 in 602.99 mm
Overall Diameter: 23.45 in 595.63 mm
Overall Diameter: 23.77 in 603.75 mm

Sidewall Height: 4.37 in 110.99 mm
Sidewall Height: 3.22 in 81.788 mm
Sidewall Height: 3.38 in 85.852 mm

Radius: 11.87 in 301.49 mm
Radius: 11.72 in 297.68 mm
Radius: 11.88 in 301.75 mm

Circumference: 74.58 in 1894.3 mm
Circumference: 73.67 in 1871.2 mm
Circumference: 74.67 in 1896.6 mm

Revs per Mile: 876.1
Revs per Mile: 886.9
Revs per Mile: 875.0

Actual Speed: 60 mph 100 km/h
Speedometer1: 60.7 mph 101. km/h
Speedometer1: 59.9 mph 99.8 km/h

Speedometer Difference: - Speedometer Difference: 1.232% too fast Speedometer Difference: 0.125% too slow
Diameter Difference: - Diameter Difference: 1.23% Diameter Difference: 0.13%
This is the scoop I found this calculator for you to see

 

Try this tire calculator too:

http://www.miata.net/garage/tirecalc.html

 

Excellent.

Keep in mind, too, that the difference in displayed speed or distance for EITHER of those optional tires is LESS than the differences in different brands of tires in the stock size, and decidedly less than the difference one would see from simple tire wear...

===

Speaking of "stock" tire size(s), the bB stock size is the 185/65R15 and the xB is 185/60R15.

In the xB Service Manuals both sizes are shown for the xB.

From empirical data the tire size actually distributed on the xB in the US was changed without changing the calibration of the odometer, since the 'error' in the odometer matches the 'difference' in travel distance for those two sizes.

The speedometer "error" is a planned difference, actually specified in the Toyota provided data for the xB. This difference between indicated and actual speed is purely from the way the US speedometer face is printed.

Here is the info direct from the xB Repair Manual:



Note the designed-in "error" - for example at an actual 80MPH the lowest the speedometer is allowed to indicate is 82MPH. It is not allowed to indicate 80MPH at an actual 80MPH, and this error will get worse as the tires wear.

As delivered, the odometer is roughly 3 percent low and the speedometer 3 percent high - "right on" is not an option.

Enjoy the info!

 

Stickied at the top of Tread and Butter:

FAQ: Wheel Fitment - ** Post Your Wheel/Tire Info Here**
https://www.scionlife.com/forums/viewtopic.php?t=348

 

http://1010tires.com/TireSizeCalculator.asp

 

im not sure if this is true at all or would work on are xbs but my dad asked about it when he got 20 and bigger tires on his yukon xl they told him there was a place in town that could reflah his speedo for him. Like i said im not sure if theres any truth to it because we never followed up on it but i could see it being possible

 

What if you're riding on 18" and you went to a 35 series instead of the 40 series, would there be a big diference. I was also wondering if I should get a wider tire instead of 215. I'm riding on sum AXIS TC Evo 18x7.5 w/ Dunlop 215/40

 

What everyone needs to understand is that only one component of the tire size by it's self is absolutely worthless. To properly discuss a tire and its merits for a particular application we need all three major components of the tire size. For instance, if you have a 215/40/18 we need all three numbers. The tires cross section width is the first number (215) the sidewall aspect ratio is the second (40) and wheel diameter ( 18 ) is the third.

Now to the question posed by Iheartdabox...

Assuming you stick with a 215 tire moving to a 35 could be a good move for you. The calculated diameter of the stock tires is 23.74". The calculated diameter of your 215/40/18 is 24.77" Approximately 1" larger in diameter than stock. The 215/35/18 has a calculated diameter of 23.93", or 0.19" larger than stock.

The reality is, according to Tomas' post and Toyota's speedometer calibration either of those tires are actually in spec. But remember, as you change your width, it affects the height of the sidewall, even if you maintain the same aspect ratio.

And just so you know, a 215 width tire is great for a 7.5" wheel. In fact, the widest I would even consider for a 7.5" wide wheel is 225. Going beyond that, the tires become to wide for the 7.5" wheel.

Good luck.

 

Wow, thanks for the great info guys. With all that information, then, I am wondering - what size of tire can you use on an 18x7" rim - if you want to stay closest to stock "diameter"?

Is it possible to get a meatier tire on an 18" rim yet still stay close to the factory guage/calibration numbers? or would you have problems like the mileage/speed being incorrect?

my apologies for this semi-redundant question.... i dont know what size to go with... i want the look of the 18s, but i also want enough meat for the huge potholes that nyc has - AND - i want the factory calibrated odometer/speedometer to remain fairly accurate! lol!

thanks in advance, everyone!
- shook

 

First and foremost, judging by Tomas' post using the words accurate and factory odometer/speedometer in the same sentence is laughable. Even at the stock tire height they speedo and odo aren't accurate.

Running an 18"x7" wheel I would probably run a 215/40/18 tire if I was worried about pot holes. This is a little bit taller than the high end of the stock calibration (185/65/18 JDM Spec.), but shouldn't affect your speedo too much. If you think you are talented enough to miss the xB sized pot holes, then a 215/35/18 should be fine.

 

Better yet with the size of the pot holes in NYC I'd stick with a 16 inch wheel and not have to worry about it. 17's maybe but with a tire more like 215/45/17, the speedo would read low but you can always adjust the needle a little to compensate

 

Good advice, Jethro - that's exactly what I decided to do! I am sticking with the same size rims that Scion offers - they'll be 16x6" rims - When I hit huge bumps, they wont go flat, plus they'll be cheap