ScionLife.com

AKgoalie7 · 11-23-2003, 03:24 PM

I've been visiting these forums for a few weeks now, after searching for a SCION webbase after I sat in one at the Autoshow down here in Miami. I plan on getting a scion xA when they arrive down here.

Anyways, I'm trying to decide what I want to do with rims (stock, optional alloys, or some bigger 18's)

Now, How can I look into rims and be safe that they won't mess up my spedometer when I slap them on the car? I'm assuming if I get the TRD 18's, the speedo will be fine? Or will they Adjust it when they put them on? Exactly how does this stuff work? I want to get a nice set of rims without much hassle.

Thanx,
AdaM

rjsalvi · 11-23-2003, 03:42 PM

Check here:

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

smilygo · 11-24-2003, 03:22 PM

You need to worry about the overall diameter of tire with wheel. You can calculate the overall diameter of the OEM tire (180/60-15). Whatever you get should be very close to the OEM diameter. OEM is approximately 23.74" in diameter. As long as the new diameter is within +/- 3% of the OEM, you wouldn't have any issues with speedometer. I came up with following calculation.

Width AR Wheel Diameter %
185 60 15 23.7401622
195 50 15 22.6771695 -4.48%
195 55 15 23.44488645 -1.24%
205 50 15 23.0708705 -2.82%
205 55 15 23.87795755 0.58%
205 50 16 24.0708705 1.39%
205 45 16 23.26378345 -2.01%
215 40 16 22.7716572 -4.08%
205 40 17 23.4566964 -1.19%
215 40 17 23.7716572 0.13%

There are may helpful Website to do this.

quadraphonic · 11-25-2003, 12:40 AM

That's assuming the speedo is based on the 15s. If it's similar to the echo, the speedo measures are actually based on the smaller 175/65R14 tire size, not the 15" option.

smilygo · 11-25-2003, 01:09 AM

It looks SCION and Echo are slightly different even though they share the same engine and suspension components. In Japan, Echo (called Patz) is on 175/65-14 while iST (Japanese name for SCION) is on 185/65-15. I personally visited Toyota dealer in Yokohama to check this out. In California, OEM is 185/60-15.

quadraphonic · 11-25-2003, 01:11 AM

Ok.. wasn't sure on the OEM tire specs.. you CAN get OEM 15s on the echo as well, but the speedo isn't calibrated for them.

I wonder if the gear ratios are altered to push the different OEM tires and the added weight..