Wheel Offsets - the "will this wheel fit" thread

[AKKO]

Adam, what diff is in yours?
It may not matter as much depending...

 

[Scradam]

Stock AYC diff.

 

[Scradam]

Will 18x9.5 +38 255 rear and 18x9 +40 245 front clear the suspension?

I've test fit 18x9.5+38 before, but with 265s and they didn't fit.

 

[it's.simon]

The rims should fit, the tyres won't. You will need a 225/40 or 235/40 and some guard rolling. As for the front 9+40 seems very high offset, you might hit something on the inside. You will definitely rub the wheel well on full lock.

 

[mills_88]

9.5+40 will not clear the inner suspension arm on the front. My 9.5+30's and 8.5+40's were both mm's away so that size would have to hit.

 

[Scradam]

The wheels I'm looking at tonight are only 9" +40 on the front, Matt.
Reckon they'll be good on full lock?

I did test fit my housemate's old starcorps on the rear just now.
Same size. 18x9.5 +38 255/35/r18.
Not even a Credit card space between the suspension and tyre.

(I couldn't lower the car off the jack because they need special wheel nuts, but I'd definitely need a flare trim and guard roll with 255s!)

 

[it's.simon]

For those who know me and my car, i am a bit of a fitment and stance fan. After two major defects, I've gotten a little bit CEEBS.

Now running matte black Enkei RPF1 in 17 x 8 +35. Now to some (and even myself) that size sounds LAAAAAAME but after putting on some 245/45/17 the fitment is spot on ace! Even with epic low and heaps of neg camber it still sits darn nice (in my opinion). So there you go, sounds fail but chunky tyre for the win. The overall diameter is slightly taller now so i get a bit more ground clearance now too woo!

Pics to come later. Cheers dudes!

 

[mcs]

get those pics, as that is the same specs as me, maybe next time ill go fat tyres.

 

[Scradam]

Ok, so I ended up buying the wheels. They came with 265/35 on the 9.5j rear, which I can bolt to the hub but the tyre is touching the suspension.

I really don't want to downsize from my current 235r17 evo 7s, but to I think I'm going to have to go 225/40 front (9j), 235/40 rear (9.5j) to get the same rolling diameter.

Pic attached is 245 front.

Edit:
Actually, according to stevep's wheel calculator. 235/40 front, 255/35 rear will give me <3mm difference in rolling diameter. Much meatier tyres!
I'm really uncertain about this. I've read from other sources that stretch doesn't change rolling diameter at all, due to the bands inside the tyre being of fixed circumference.

 

[GMan]

For those who know me and my car, i am a bit of a fitment and stance fan. After two major defects, I've gotten a little bit CEEBS.

Now running matte black Enkei RPF1 in 17 x 8 +35. Now to some (and even myself) that size sounds LAAAAAAME but after putting on some 245/45/17 the fitment is spot on ace! Even with epic low and heaps of neg camber it still sits darn nice (in my opinion). So there you go, sounds fail but chunky tyre for the win. The overall diameter is slightly taller now so i get a bit more ground clearance now too woo!

Pics to come later. Cheers dudes!

I see these wheels on Ebay and Gumtree every now and then. Yes, please show us some pics when you get a chance

 

[Dice]

Will they clear Brembo?

 

[Scradam]

Using a piece of string, I've solved the age old question of how tyre stretch influences rolling diameter.

Some people who are running staggered wheel widths might be interested to know this.

According to stevep's calculator, I worked out that there should be a 6mm difference in diameter for a 265/35R18 tyre on a 9.5j wheel and a 245/40R18 tyre on a 9j wheel.

Measuring this (via string around circumference of wheel), I found it to be 12mm. Which pretty much matches up with the tyre specs on tyre manufacturer's websites (10mm).

I confirmed this with some more heavily stretched wheels. 235/40R18 10j vs 225/40R18 9j measured 9mm difference.

And lastly, I found a set of wheels with tyres that should be 2mm difference in diameter according to tyre manufacturers.
225/40R18 8.5j vs 255/35R18 9.5j measured exactly 0mm difference!!

So, to conclude: Tyre stretch does NOT influence rolling diameter.
If it does, it is negligible.

This is because the metal belts inside the tyres are of fixed circumference, the sidewalls simply bulge or flatten to reach the bead seats of the rim.

To calculate rolling diameter, use the simple formula:
2*(tyre width * profile%) + (rim diameter * 25.4)
eg. 255/35/R18
2*(255*0.35) + (18*25.4) = 635.7mm

 

[steveP]

Thanks for your info and testing. I will take it into account when revisiting the wheel calculator program.

 

[AKKO]

Caveat being same type/model/manufacturer of tyre all round in my experience (with reference to rolling diameter calcs).

 

[it's.simon]

Pretty sure a 235/40 for example stretched or not will always be a 235/40. The rolling diameter will never change, instead of diameter consider the circumference instead. The circumference of any given tyre will remain constant irrespective of how much or how little it is stretched. The only difference would be that the sidewall won't seem as "tall" because the sidewall is sitting stretched at an angle as opposed to perpendicular to the road. Another thing to consider would be the internal diameter of the tyre, if the sidewalls are flared out wouldn't the internal diameter of the tyre be bigger? Probably marginal difference but I would guess much added stress to the sidewall and it would handle terribly without any form of rollover characteristics of a normally fitted tyre.

To be honest I didn't think it was an age old question, logic and reasoning could have figured it out without research. If you really want to run staggered widths, you would need to run staggered profiles also in order to match them as closely as possibly. For example 225/40 and a 245/30 (I made this up, they probably don't match).

That's my observation anyway, don't take my word for it LOL.

Edit* I didn't read the last part of your big post, I'm just repeating you. I just did an extremely knob post.

tl;dr: I agree.

 

[Scradam]

The 'age old' part was added as an afterthought for dramatic effect, haha.

Looking forward to these pictures you promised, Simon. I need some inspiration for fitting fatter tyres under there

I see so many references all over the internet that suggest a change in rolling diameter due to stretching.
Just thought I'd clear this up for everyone else who might be in the same boat I was.

In extreme cases, the very edges (shoulders) of the tread can stretch and become curved, which may cause the tread to thin out a little, but as we both said, the change will be negligible.
I suppose the only significant thing this would change is the size of the contact patch and the lateral stiffness of the tyre.

Here are some combinations that are calculated to be approximately equal in rolling diameter. (within 0.3%)

• 235/40R18 & 265/35R18 & 235/45R17 & 265/40R17
• 225/40R18 & 255/35R18 & 225/45R17 & 255/40R17
• 215/40R18 & 245/35R18 & 215/45R17 & 245/40R17
  
• 205/40R18 & 235/35R18 & 205/45R17 & 235/40R17

I'd advise people to confirm this using your tyre manufacturer's website. Tyres dimensions can vary with tread design.

Thanks for your info and testing. I will take it into account when revisiting the wheel calculator program.

Cheers for the great program, Steve. It's been extremely handy for me and I'm sure countless others.
If I get some time in the next few months, I might look at replicating some of its functionality in Javascript for the non-windows users.

 

[MR2QIK]

Hey everyone,

Getting the itch to tinker with the legnum. Got a decent set of 19x8.5 +35 rims @ home which have been whored around a few of my cars. Planning to paint or powdercoat them pearl white to match my FL Leggie. Unsure how I'll lower it.

I'm sure they can fit, but:

Tyre size? 225/40/19 ok? Want 40 due to comfort.
Clearance or guard issues requiring modification or roll?
Anyone know a cheap painter or powder coater in Western Sydney?

 

[trotty]

Hey everyone,

Getting the itch to tinker with the legnum. Got a decent set of 19x8.5 +35 rims @ home which have been whored around a few of my cars. Planning to paint or powdercoat them pearl white to match my FL Leggie. Unsure how I'll lower it.

I'm sure they can fit, but:

Tyre size? 225/40/19 ok? Want 40 due to comfort.
Clearance or guard issues requiring modification or roll?
Anyone know a cheap painter or powder coater in Western Sydney?

Hyper performance coatings in Penrith production place. He does my ceramic coating and powdercoated pipes. Very reasonably priced and great work.

 

[mills_88]

Sorry for the delayed response Adam, don't come on here too often these days.

Looks like they fitted alright in the end, did you end up having any clearance issues or do you still have a few mm to spare between the wheel and suspension arm / tyre and inside of the guard.

 

[tails]

I run staggered wheels (9 rear and 8 front). I run the same size tyre on both (235 45 17). From memory, the rolling diameter difference was like 1%, I can't remember exactly but it was low enough for me to stop caring.