OK, so, I know that tyres and wheels are different and I know they have different sizes and such, but, what will fit on an i30?
I've seen some wheels I like the look of, and the Bob Jane website handily tells me I can have the largest most expensive ones for an i30, but I don't think anything more than 15" or 16" is worthwhile. I've heard larger can affect road noise and ride quality, as there's less rubber between rim and road.
So, my question is, what size could I comfortably (safely?) go out and buy and have fitted, and are there other factors that contribute the decision making process, technically speaking?

Thanks in advance

[rustynutz]

You probably need to consider what sort of roads you'll be driving on.....

If you intend driving on a lot of rough or dirt roads,personally I don't think I'd go for anything larger than 16". (the SX has 15")
Another factor is, the larger (diameter) you go in wheel size, the more costly the tyres will be....also, as you've made mention of, the ride quality will suffer due to the fact that the tyres need to be a lower profile to keep the overall diameter the same...

Cheers 

Mostly it will be made roads. To and from work is almost exclusively freeway, and long Sunday drives will be the same.

If I get 15", can I use the stock tyres? What does width and offset refer to?

[Surferdude]

nemisis,

offset relates to where the mounting point at the back of the wheel hub (the part that mates up to the disc hub) is in relation to an imaginary line drawn through the wheel. It's important not to fiddle with offset as the vehicle manufacturer designs his whole suspension and handling around this. But, unless you buy something really wild like a super deep dish style, you're unlikely to run into trouble. Also, if you deal with Bob Jane, they should generally advise you properly. They're liable under the law if they misadvise you.
Any modification to the offset can have a seriously dangerous effect on steering and braking stability.

Width is simply the distance between the inner and outer rims (where the wheel weights clip on) of a wheel and dictates what size tyre can be fitted.
 What Russ said about tyre pricing is right, except that the popularity of 17" (particularly 235/45R17) makes them generally cheaper than a lot of 16" stuff just based on the volume of production.
If you've got 15" wheels now, 16" or 17" should be OK.

For more detailed explanations about wheel specs just google "Wheel offset", or "Wheel width" for sites with diagrams which will make it easier to understand.

[rustynutz]

If you want to stick with the original tyres (which apparently are pretty ordinary) I'd be tempted to stay with the standard rims until the tyres are worn out, then upgrade to new wheels & tyres.

Here are some links you may find helpful:
http://en.wikipedia.org/wiki/Wheel_sizing
http://www.gomog.com/allmorgan/wheeloffset.html
http://www.usacomp.com/terms.htm
http://www.1010tires.com/WheelOffsetCalculator.asp
http://www.1010tires.com/tiresizecalculator.asp

Cheers 

Thanks for the help

I don't necessarily want to keep the default tyres, just looking at options to reduce cost is all. 

It seems to me an important number in all this is PCD - if the bolts don't match the holes in the wheel, it's a problem.  Can you tell me the PCD on an i30?
I'm confused because the Bob Jane site is telling me wheels with a PCD of 110 are ok, but so are wheels with a PCD of 114.3. I would think a difference in pitch of that much would have some sort of repercussion. Offsets also vary between 45 and 48.

Fitment guides list 5x114.3, 45 offset, and 16" diameter with 3, 4 or 6" width... does that sound right?

[rustynutz]

I think I'll leave it to Trev (surferdude) to explain all that stuff, it's getting too deep for me....

Cheers anyhow...

[Surferdude]

Thanks for the help

I don't necessarily want to keep the default tyres, just looking at options to reduce cost is all.  

It seems to me an important number in all this is PCD - if the bolts don't match the holes in the wheel, it's a problem.  Can you tell me the PCD on an i30?
I'm confused because the Bob Jane site is telling me wheels with a PCD of 110 are ok, but so are wheels with a PCD of 114.3. I would think a difference in pitch of that much would have some sort of repercussion. Offsets also vary between 45 and 48.

Fitment guides list 5x114.3, 45 offset, and 16" diameter with 3, 4 or 6" width... does that sound right?

Speedy Wheels have this page which clarifies PCD and Offset.

http://www.speedywheels.com.au/wheel-tech.htm

I cannot imagine how you can have 2 suitable PCDs. However, having said that, there are available some "multifit" wheels so maybe this is what they mean. My personal advice is to stay away from multifit wheels.

Pretty sure the correct PCD is 5 x 114 but I've seen someone else post this on here so maybe whoever it was will confirm it.
Re 16" diameter with 3, 4 or 6" width not sure what the 3 or 4 are doing there. i30 rims are 5.5" or 6" wide to start with (in 15" and 16" diameter).
And I think offset of 35 to 45 is OK. Again, someone on here will know for sure.
I'm at home today but will be in one of our stores tomorrow and with access to more in the way of catalogues so I'll try to add some more detail tomorrow night.

Awesome! Thanks so much for the help. Levelling up my wheel knowledge in a day is great I'll be well prepared when I go out to buy some.

[de Bounce]

Another resource is the The Wheel & Tyre Bible
More info about wheels, tyres and all things cars than most people would ever need to know

[Surferdude]

Confirming the PCD is 5 x 114.3
In  15" stuff the offset is 47P (positive) on steel wheels and 50P on alloy wheels.
With 185/65R15 the OD (Overall Diameter) is 621 mm
With 195/65R15 the OD is 632 mm
These are generally 5.50J15 rims

In 16" stuff the offset is 50P for an OD of 632 mm (on 205/55R16
Normally 6.00J16 rims

For 17" (225/45R17 on 7.00J17 rims you have offset of 56P and 632 mm OD.

You can get minor variances in the OD from brand to brand and sometimes even with different patterns of the same brand but they aren't enough to have any detrimental effect.

I must admit I was surprised to notice the differences in offset between steel and alloy wheels but i guess it makes sense if you think about it.

Thanks so much for the info, surferdude. New question, if the offset is 50P, what does that mean for wheels listed as 45?

[2i30s]

I'm interested to know also Trev. 

[Surferdude]

^^^^^
Don't know.
But I'll make some more enquiries.
I suspect that 5mm wouldn't make a great deal of difference but there must be some sort of guide for this.

Somewhere. :-\

[2i30s]

^^^^^
Don't know.
But I'll make some more enquiries.
I suspect that 5mm wouldn't make a great deal of difference but there must be some sort of guide for this.

Somewhere. :-\

Again, thanks so much for the help. I'm amazed - normally forums are not this helpful

[Surferdude]

Again, thanks so much for the help. I'm amazed - normally forums are not this helpful

It's no problem neme.
The i30 forum IS different.
Real people, real cars, genuine participation. 

I've been here a little over a year now and enjoyed it immensely.

[2i30s]

hey guys i sussed out a handfull of rim offset searches and found that you have a negative or positive offset.if you lay the rim on its face and measure from the hub face to the outer edge of the rim you get the offset distance,positive. measure from the front of the rim to the hub face gives you the negative offset.  i hope Ive explained it rite and not assed it about. anyhow you get the jist. 

[Surferdude]

hey guys i sussed out a handfull of rim offset searches and found that you have a negative or positive offset.if you lay the rim on its face and measure from the hub face to the outer edge of the rim you get the offset distance,positive. measure from the front of the rim to the hub face gives you the negative offset.   i hope Ive explained it rite and not assed it about. anyhow you get the jist.  

I'm not sure about that.
If you look at the wheel from the front and draw a line through the rim extremities from the machined surface which mates to the hub, a positive offset will have more than half the rim inside of the line. A negative offset will have more of the rim outside the line.
That's how I understand it anyway. Not sure I've explained it any more clearly than 2i30's.
I need a sketch but I'm away from home.

Thank God fro Google

Here's some.

[2i30s]

hey guys i sussed out a handfull of rim offset searches and found that you have a negative or positive offset.if you lay the rim on its face and measure from the hub face to the outer edge of the rim you get the offset distance,positive. measure from the front of the rim to the hub face gives you the negative offset.  i hope Ive explained it rite and not assed it about. anyhow you get the jist. 

I'm not sure about that.
If you look at the wheel from the front and draw a line through the rim extremities from the machined surface which mates to the hub, a positive offset will have more than half the rim inside of the line. A negative offset will have more of the rim outside the line.
That's how I understand it anyway. Not sure I've explained it any more clearly than 2i30's.
I need a sketch but I'm away from home.

[Surferdude]

hey guys i sussed out a handfull of rim offset searches and found that you have a negative or positive offset.if you lay the rim on its face and measure from the hub face to the outer edge of the rim you get the offset distance,positive. measure from the front of the rim to the hub face gives you the negative offset.  i hope Ive explained it rite and not assed it about. anyhow you get the jist. 

I'm not sure about that.
If you look at the wheel from the front and draw a line through the rim extremities from the machined surface which mates to the hub, a positive offset will have more than half the rim inside of the line. A negative offset will have more of the rim outside the line.
That's how I understand it anyway. Not sure I've explained it any more clearly than 2i30's.
I need a sketch but I'm away from home.

Too quick for me. Post now includes pics.

[2i30s]

we knew what we meant,but pics speak better. 

[agentr31]

im not going to read through the whole lot...

BUT

our cars have a 114.3 x 5 PCD...

a 35+ offset WILL NOT WORK... look at my avatar and see just how much they sit out... 45 ~ 55 will work... i wouldnt go past 45+ unless you want a 'tough stance'

[Surferdude]

im not going to read through the whole lot...

BUT

our cars have a 114.3 x 5 PCD...

a 35+ offset WILL NOT WORK...

True Ian. I have no idea why I posted the "35" way back up at th eyop of the page. Typo maybe.  Anyway, the later stuff clarifies what our cars have.

[2i30s]

my rims are 38+ offset. they only just sit level with my mudguards/fenders. look in petrol pics, my hatch pics and mods, and you'll see what i mean.