WARNING: Ultra-noob question.

[modern_messiah]

Hi all,

I am not going to beat around the bush and pretend that I know the first thing about cars. In fact in my "Hi, I'm Matt" post in the introduction section I clearly state this is the first time I have taken a keen interest in my ride. (My Vectra is testament to that fact lol)

Anyway, I am picking up my Liberty this weekend and while it is a stock bottom of the line vehicle, I am purchasing the Spec B wheels for it as I like the look (I'm generally not too much of a fan when it comes to after market stuff). I was going to buy them post sale as it was cheaper for me that way.

I got into a discussion with a car keen mate of mine who is busy building a hotrod. I mentioned the wheels and asked if having the stock 17" as a spare would be bad if I actually needed the spare to drive a few km's to a wheel shop in the event of a puncture etc.

He said no because while the rim size my differ the profile wont. I pointed out this was not the case and I got this reply:

lol, actually your right. just checked. typically the ground clearance and arch fill would be achieved via suspension, not changing the rolling diameter.

which actually means your speedo is going to be out when you put your spec b wheels on. unless u change the tyres or get subaru to reconfiguire your dash

the normal liberty and the spec b 3.0 have:

215/45 R17
215/45 R18

The "45" is the profile. 215 is the width, R17 is the rim size. (no, R does not stand for Rim, lol)

Thats a little screwed man...i would still be surprised if thats true (websites can be wrong) but if it is your speedo and odo will be out...

Is he right? It seems odd to me because I have another mate who is even more into his car's (f**king Ford hard nut) and he has changed so many wheels over its not funny yet I have NEVER heard this problem mentioned before. Maybe my first mate is only looking into it too deeply because he is literally building a car at the moment???

And for the record I did not ask him what R stood for lol. I'm not that dumb.

I was going to do the swap myself so any help would be appreciated.

[swingn]

A number of us actually have 17's a spares

Providing you keep the rolling radius as close to stock as possible there should be no problem

To give you an idea... I'm running 18 x 8's with 225/40 rubber... My spare is the stock standard 17 x 7 with 215/45 rubber... Pretty damn close in regards to the rolling radius:)

[modern_messiah]

Ah...problem is the wheels come with the tyres. Far as I can tell they have been ripped straight off Spec B's (They are been sold by the dealer themselves)

[modern_messiah]

Just got a message from the dealer (missed the call). They reckon i wont make a difference on the Liberty. Gave a reason for it but I can't remember the exact wording but it was along the lines of "same car" or some crap...

Not sure whether to take their word for it or not.

[Spec B Wgn]

put it this way... the spare is an emergency tyre

if you have different rolling diameters you dont want to be doing long miles or high speeds with different wheels ... its not good for the diffs

[modern_messiah]

Yeha I fully understand that...its technically a lease car and as part of the requirements on my behalf I must do a certain amount of kilometers. Will the different tyre sizes make a massive difference or will it be minimal?

[Spec B Wgn]

if all 4 wheels and tyres are the same then no problem ..

start mixing and matching different diameters and you may have issues.

[541NTT]

well i have a 2004 GT lib with the stock 17s, i bought the b spec 18s with the factory fitted tyres and they are a larger rolling diameter, the speedo was out but only buy a fraction- not enough to be noticabl or to get you into trouble- i was using my 17" as a spare still.

now i have 19" wheels and still have the 17 as a spare, in the user manual it states that if you get a flat and your spare is a different diameter to the other wheels, you must pop the bonnet- crack open the fuse box and put the spare fuse in the AWD plug, this will disengage the AWD system and make the car front wheel drive only.

then drive home and get your spare off when you get the time (obviously you dont want to be doing massive klms with it on but i dont think its disastrous to be driving around to a tyre shop or home with it)

hope that answers your questions.

[smythie]

the greater the difference in rolling diameter, the more your diffs have to slip in normal driving. Unless the diffs are open, they will be trying to lock up all the time - very bad

[modern_messiah]

Argh contradicting answers

Um, I'll be getting my car serviced by Scorptech Subaru (run by Michael Collins) here in Brissie so maybe it'd be worth asking them? It could be a simple ECU change...

[Spec B Wgn]

Argh contradicting answers

Um, I'll be getting my car serviced by Scorptech Subaru (run by Michael Collins) here in Brissie so maybe it'd be worth asking them? It could be a simple ECU change...

there's no contradicting answers..

if your running the same diamatres on all 4 wheels then no problem

start running 3 X 18's and 1 X 17 and your diffs arent going to like it.

pretty simple as has been mentioned above by other members.

[modern_messiah]

Oh I see...originally I asked if running the larger wheels (on all 4) would create an issue with speed etc, so when I was reading the responses my brain was looking for that answer. So I got confused

But that makes perfect sense now. Thanks for clearing that up

[Spec B Wgn]

all good..

just for the record ...my wifes lib wgn is running 235/35/19 as compared to the stock 215/45/18 and no dramas what so ever.

speedo calibration is spot on as well.

[modern_messiah]

Ah well then, provided I have no hiccups Saturday will be a great day! Thanks for the help fellas.

[CJ1177]

If you do a search on here there are plenty of threads that talk about the accuracy or lack of it of the stock rims so if you get larger rims & matching stock tyre size you will actually correct the speedo.
This is what happened on my car, stock is 215/45-17 with the speedo reading approx 8km over actual speed & I now have 225/40-18 & the speedo is now only slightly over actual, if i had 215/45-18 I'm sure the speedo would be spot on.
I came to this conclusion with the help of a GPS


TIP: if your still worried get a GPS & compare your speed to that, then use a tyre calculator to compare the difference & you will see you will be OK