Posted: Thu Apr 08, 2010 2:04 pm Post subject: Never need to ask "will this fit again!"
Alright so here is the crash course in what you need to know when changing your rim size.
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Part One
Wheels and tyres:
This deffinitley applies to Western Australia, and I belive to the eastern states and NZ aswell.
As far as australian gov. is concerned, modifying is dangerous and pointless.
Getting your head around that fact will really help when your choosing the right wheels for your car and budget.
Although this dosnt make it good fun its makes it very simple as your choice is very limited...
Basicly, your wheel has to be available to buy in Australia, there is no real way to get around this, you can import from USA, JAP or China but in the end alot of these wheels do not meet Australian standards (load ratings and stress testing)
As for your tyres **this is key**
They must have the same (or better) load and speed rating - your local tyre store can help you with this.
This makes it pretty hard when upsizing to 19" or 20" wheels, as to get a tyre in a 20" that can hold the same load as a 16" is quite rare and restricts the brands and sizes available to Aristo's (being as they are such big heavy cars).
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when upsizing your wheel (in inches)
the profile of your tyre must reduce so that in the end the overall **rolling diamiter** stays the same.
I'll quicky explain the basics of tyre sizing - say you have a 235/40/R18
We all know the first one is your width - in mm
The second one is your sidewall - what confuses most people is that this is acctualy a ratio!
In this case your sidewall height is 40% of the width of the tyre or roughly 95mm
And lastly fairly self explanitory its to suit an 18" diamiter wheel
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Its gets a little tricky here so stay with me :
Your standard tyre with a rolling diamiter of (X) can change very slightly (3-4%) depending if its brand new or worn.
This it what directly affects your spedo, belive it or not!!!
This is not exact for Aristo's so don’t go around driving 10km/h above the speed limit with bald tyres
If you have a new set of tyres (standard rim size and standard everything) - 100km/h is acctualy about 96km/h
if you have a worn set of tyres (again standard size ) - 100km/h is acctualy about 90km/h (give or take)
YOUR SPEDO WILL NEVER BE PERFECT!
when changing wheel widths and sizes, us in perth (and i belive everyone else in AUS aswell) have to calculate the NEW rolling diamiter of your tyres and make sure its within 3% of the original,
This is LAW and the main issue you will come accross - just pretend it is purley to give you a minimal effect to your spedo.
(You can find some good calculators to do this for you just by searching in google.)
so when changing rim size, you can measure your standard *rolling diamiter* and calculate something that will be the same *rolling diamiter* - in your new rim size, and therefore not affect your spedo's accuracy.
Checking with a tyre store as to what different brands do in these sizes is cruicial as using a 265/35/18 might look great on the back and be a lot cheaper than a 275/35/18
But if your load and speed ratings are not up to scratch your going to have problems.
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Part Two:
Offsets:
again, o so fkn epic, it gets pretty heavy but hopefully i can explain it in a way that makes some sort of sense to you.
ive drawn up a little picture to show you what im on about so take a gander once you've read this.
Basicly OFFSET is a measure of your wheel's point of attatchment to the hub of your car from the center of the wheel. WOW BIG SENTENCE
so for example - a wheel that is 10" wide **(dont worry about diamiter on this it makes no difference)**
5 inches from either side (*the middle*) this would be point '0' or '0' offset.
what we are acctualy looking at is the distance from that point '0' to where the Back part of the wheel sits onto the hub of your car.
Most cars have positive offsets, this would indicate that the place on your wheel where it acctualy meets the hub of your car is infront (towards the face) of point '0'
the further towards the face it is the higher the number it is in + offset.
Using that knowledge you can work out that the higher the offset + the closer together the wheels will sit.
Not only do we not want this; for stability purposes in cornering, but my personal opinion and the opinion of many people on here is that it looks a bit
Lowering your offset (within reason) will get you a better track width (distance between your wheels) giving you better stability and also fill your guards more.
What we call a Fat offset.
For any of this to be relevant you will want to know - What is your current wheel's width, and what is your current wheels OFFSET!!!!!
Using his information you can easliy estimate the position of a wheel in relation to the inner and outer guards of your car as this is where your going to run into problems if you buy the wrong wheel.
And please remember **if you are going to put wider wheels on, you have to adjust your offset to suit**
Changing from an 8" wide wheel to a 9" wide wheel with the same offset will decrease the distance from your inner and outer guards an even ammount (half an inch)
When you start thinking about widths of 10" or greater this can dramaticly effect the offsets and ability to lower your car without rubbing or hitting on either guard.
Clearance over brakes is not my speciality and sadly every wheel is different so i wont touch on this subject.
Let me know if ive just confused the fk outta ya or if you have any questions about anything in specific, or if you can see any major flaws in what I have written, I CBF proof reading it all more than once.
Edited slightly in offset section
As a side note:
A common offset for Fords/Toyota is about 35+ on an 8" or 8.5" wide wheel, this would be your off the shelf aftermarked 17" or 18" rim very 'neat' cheap to get tyres for and is still wider than original equipment.
however as stated before ... a little for some people
Common Sizes
Original fit would be: - Aristoman if you could please confirm this **
205/65R15 or 215/60R15 - for GE modles, may be a factory option for wider rears on GTE
17"
Common 17" sizes would be - 8" or 8.5 Front
Suiting 235/45/17
Rears Commonly 9" or 9.5 Wide
Suits 265/40/17
18"
Common 18" sizes would be - 8" or 8.5 Front
Suiting 235/40/18
Rears Commonly 9" or 9.5 Wide
Suiting 265/35/18 or 275/35/18
19"
Common 19" sizes would be - 8" or 8.5 Front - can fit 9" font with some love
235/35/19 , 245/35/19
Rears Commonly 9" or 10"
Suit 265/30/19 , 275/30/19
20"
Common 20" sizes would be 8" front if your buying from Tempe or alike, 8.5 or again 9" can fit
235/30/20, 245/30/20
Rears Commonly 9" All the way through to 11"
265/30/20, 275/25/20, 285/25/20, 305/25/20
This is just a rough guide for Aristo's
Common offsets for front = 30+ up to 38+ for most sizes between 8" wide and 9" wide
you will run into problems running lower than 30+ on a 9" wide front
Common offsets for rear = again 30+ for the skinnier up to 40+ for the wider (this is if your trying to keep them in the guards)
(thanks to naki boy and shrekvk for info/recomendations)
Last freaked with by FIRSTROUND on Tue Apr 13, 2010 4:05 pm; freaked 3 times in total
Joined: 28 Oct 2009 Posts: 45 Location: taranaki new zealand
Posted: Tue Apr 13, 2010 4:01 pm Post subject:
standard tyre sizes are on a stiker in the drivers door jam. im not sure about gte models as mines only a ge but its 205/65R15 or 215/60R15. you shouold find this info inside the doors of all jap cars. Also most tyre shops should have a chart showing the rowling cecumfrance of all tyre sizes.
p.s even i understod that explantion awsum job. _________________
Joined: 19 May 2008 Posts: 656 Location: Perth - SOR
Posted: Tue Apr 13, 2010 4:12 pm Post subject:
It does bear to comment i think that those are the 'legal by the book' fitment guidelines
if you are a bit more adventurous, you can buy wheels from overseas with little to no issue through people such as jesse streeter ( www.jessestreeter.com ) and you will have no problems even if they arent an 'australian standard' wheel. they're probably better than a lot of the 'generic' cheaper brands you get from local tyre shops.
when it comes to fitment, imo a good fitment is 19x9 and 19x10 on an Aristo. Your offsets will then determine tyre sizes, camber and guard work.
Generally offsets around +25 are pretty nice with some stretched tyres (say 235/35 or 225/35 Front and 245/35 rear). Some minor rolling of the guards will probably be necessary.
This type of setup is easy to run, looks a lot nicer, and is not a dangerous setup. just keep an eye on tyre pressures if you are going to run this setup. Also, you will find your tyres will be below the load rating for a Lexus which is 94. the 235s and 245s will probably be around 91-93 and the 225s will be 85-88.
It does bear to comment i think that those are the 'legal by the book' fitment guidelines
if you are a bit more adventurous, you can buy wheels from overseas with little to no issue through people such as jesse streeter ( www.jessestreeter.com ) and you will have no problems even if they arent an 'australian standard' wheel. they're probably better than a lot of the 'generic' cheaper brands you get from local tyre shops.
when it comes to fitment, imo a good fitment is 19x9 and 19x10 on an Aristo. Your offsets will then determine tyre sizes, camber and guard work.
Generally offsets around +25 are pretty nice with some stretched tyres (say 235/35 or 225/35 Front and 245/35 rear). Some minor rolling of the guards will probably be necessary.
This type of setup is easy to run, looks a lot nicer, and is not a dangerous setup. just keep an eye on tyre pressures if you are going to run this setup. Also, you will find your tyres will be below the load rating for a Lexus which is 94. the 235s and 245s will probably be around 91-93 and the 225s will be 85-88.
mainly touching base on the load ratings - yes agreed its very had to find CHEAP tyres in correct load ratings.
most sports maxx or alike have what they advertise as an XL sidewall (extra load) and thus provide 95/96 on most common sizes
Joined: 27 Aug 2009 Posts: 359 Location: Cairns/Melb
Posted: Tue Apr 13, 2010 4:27 pm Post subject:
I just ordered some 235 40 18 Khumo KU31 from www.option1garage.com.au for $150 each. Awesome tyre and cheap as through them. All other tyre shops are total rip offs and want about double that for the same damn thing. Load rating is 94 too.
Am looking for a decent, cheap 265 35 18 with the appropriate load ratings. I'm glad my new rims came with Michelin Pilot Sports (load rating of 97, standard fitment for McLarens, Ferraris & GT3 porches etc) :-D. option1garage do KU31s for $200 a tyre in that size :-D
p.s i hope this info helps people fight the dreaded Canary, if you can talk some shit about - load/speed/ size/ width/ australian standards to the pits (if you've already got one) or to the officer inspecting. hopefully you will get away with it.
as that is the only issue i come accross, i dont find many people with "dangerous" settups (other than using non hub style spacers) but yeah just sucks when someone pay's good money for wheels and gets a canary and has to put stockers back on to get over the pits when there's might be perfectly legal (if they've "been less adventurous")
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