Tire size change

[lrossnm]

I have an '05 2.5i Outback wagon. I would like to switch out the stock 16" wheels for 17" ones. The dealer told me that this would mess up the cars sensors.

 

Has anyone else done this switch? Is the dealer correct?

 

Feedback please.

[firstwagon]

I have an '05 2.5i Outback wagon. I would like to switch out the stock 16" wheels for 17" ones. The dealer told me that this would mess up the cars sensors.

 

Has anyone else done this switch? Is the dealer correct?

 

Feedback please.

 

You have to match the sidewall size so you don't change the overall diameter of the tire (much).

 

Here's a handy calculator to figure out what size tire to use....

 

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

[Ranger83]

17's on the 06's have the same rolling diameter.

[idosubaru]

if you get larger wheels you get smaller sidewall tires so the actual wheel/tire combo size does not change.

 

but...if you wanted to go with larger rims and tires you can do that as well. the dealer is F.O.S as usual. "mess up the cars sensors"??? what they have "wheel size sensors" on them? ha ha. your limitation will be clearance if you want larger tires too, but you can for sure go up a size or two with no issue.

[rlsimpso]

All I can think is that the speedo would read low because larger diameter tires would be rolling more slowly at the same speed.

 

If you do go with bigger wheels make sure the offset is such that the tires won't rub. I tried to put 215's on in place of the 205's on my stock Legacy wheels and the rears rubbed on the struts when the suspension compressed.

 

As stated if you stay close to the stock diameter and width you should be fine.

 

It should be possible to reprogram to computer to account for the difference, but I am not sure how:confused:

[BruceyWV]

I put 27.5's on mine and the speedo seemed more accurate, according to the roadside construction radar signs.

[rlsimpso]

Try a GPS. I found those "your speed is" signs are off by 1-3 mph some times.

 

I also like the time slips you get on the Ohio Tollway. I hope they never look at them, or I would be getting some tickets:)

[rlsimpso]

Looks like you may have already.

 

City: 39.658193 -79.964263

[BruceyWV]

According to my etrex with the 27's its identical, and with the tripple treads my speedo is fast. I'd trust it after the signs though, because do they also show elevation? All the roads in my area arent flat.

[rlsimpso]

I've been in MI for too long. I think I can remember what a hill is:) They just got some out in Colorado I hear.

 

I-94 is almost dead flat through MI in most places. The Extrex (silver one) I have used does should elevation. I assume it is doing some calculations. Of course you know what assuming does.

[NOMAD327]

There is a new consideration with this question. Thanks to Ford Explorers, a lot of brand new cars have tire pressure monitoring, (I don't know about Subaru's, check your owner's manual) they mostly work by using the ABS sensors to check that one tire isn't spinning a bit faster than the other three. I don't see how that makes any real change over what could mess up the braking part of the ABS system, but it's something that we're not used to considering. On the surface, at least, a set of four identical sized tires shouldn't make any difference in any way.

[rlsimpso]

The tire pressure monitors I have seen strap to the wheels or attach to the valve stem inside the wheel. I also found one that goes on in place of the valve

stem caps. http://www.tirepressuremonitor.com/details.htm

 

This is what new subs have http://www.cars101.com/subaru/tiremonitor.html

 

They have battery powered pressure sensors and transmitters. There seem to be two basic types. One only transmits a signal when the pressure drops below some preset value. The other output the pressure contantly.

 

I would expect wheel speed changes to make traction control come on before doing anything for tire pressure. Wheel speed, steering angle, throttle position, engin speed, roll senors, yaw sensors, and probably other more expensive sensors are used to determine if there is a loss in traction.

 

The tire would need to be close to flat before it would make a signifcant difference in rotational speed.

[vic/se]

I have an '05 2.5i Outback wagon. I would like to switch out the stock 16" wheels for 17" ones. The dealer told me that this would mess up the cars sensors.

 

Has anyone else done this switch? Is the dealer correct?

 

Feedback please.

 

I did it! your dealer is joking!

[stedler]

There are a lot of things to consider when making a tire size change. Going to a larger diameter rim with low profile tires should be ok, use a tire size calculator to make sure your outer diameter doesn't change.

 

As to wether changing the tire size will effect the sensors. I imagine that would depend on wether you are changing the outer diameter.

 

On normal 4wd's you just change the gearing in the diff's so you don't change the amount of torque you generate to the wheels. As well as adjusting the speedo.

 

But Sube's, at least the new ones, have a lot of different sensors for the AWD system as well as the ABS. will changing the size of the tires effect this. Well, if you go with a Larger outer diameter you will through off your braking distances as well as your fuel economy. (bigger tires equal greater rolling resistance, which in turn affects performance and fuel economy)

 

I've seen older sube's with rather large tires on them, but don't know what effect it had.:-\

[Ranger83]

To reiterate: the rolling diameter of the 16" wheels and tires on the 05's and the 17" wheels and tires on the 06's are identical or nearly so. You can look them up on the Bridgestone website.

 

To make the change Subaru simply went to a lower aspect ratio tire - it's done all the time aftermarket as a "+1 upgrade."

 

Your ABS sensors, differentials etc will never know the difference.