NewHilux.net

Since there has been a LOT of questions about it (including myself).. i thought maybe we should have a sticky for it defining what it is, and how its calculated.. please add / amend this so eveyone can understand it..


OFFSET

Offset (ET)

The offset of a wheel is the distance in millimetres between the mounting face and the centre line of the wheel.

Positive offset wheels have the mounting face closer to the outside of wheel, forward of the centre line. This will place the wheel further under the car. These wheels generally have very little dish on the outer rim and a small wheel boss on the back of the wheel. Eg. Subaru & Honda

Negative offset wheels have the mounting face towards the back of the wheel, rear of the centre line. This results in the wheel sitting further out from the car. These wheels can have a deep dish on the outer rim and/or a large wheel boss on the back. Eg. Pre AU & 4WD wheels.

Calculating Offsets

* To find the offset of a wheel, first measure the backspace of the wheel from bolt up face to back edge of wheel
* Measure the overall physical rim width (edge to edge) or add 1 inch to the manufacturer’s stamped wheel size.
* Multiply by 25.4 to convert to millimetres and then divide by 2 to find the centre line of the wheel.
* Subtract the centre line measurement from the backspace measurement.
* This will give you either a positive or negative offset measurement.

In most cases, changing the offset of a wheel will increase the loads on bearings, axles, suspension joints and steering components. For this reason it is important to fit wheels with a correct offset to prevent premature wear or suspension failure.

WHEEL DIMENSIONS

Wheel Width
Width of the wheel measured from outer bead seat to inner bead seat. This is not the same as the physical width of the wheel.

Wheel Diameter
Diameter of the wheel measured from the bead seat to opposite bead seat. The physical size of the wheel will be a larger diameter. Centre line Half of rim width measured from edge to edge.

Rear Spacing
The distance from the mounting face to the outside edge of the back of the wheel. This can be measured by placing a straight edge across the back of the wheel and measuring to the mount face. This distance can be used to calculate offsets.

Hello All

As there is so many questions about offsets and wheel sizes ( probably from me ) So i thought that i would post up the calculator it also has all the favorite mud tyres in the cateldog.

Hope this helps

Wheels and Tyre Calculator

Well since you did that, I'll add to that and include a wheel Backspace/Offset Chart that is very friendly to use -


Aswell as the Manual Calculation method of Converting Wheel Backspace an Offset -




MOD's, this sort of info might be good to be a sticky of sorts in the wheel/tyre section.

Ok.

Great info guys.

Making it a sticky.

I believe the upcoming tyre bible is under Mark @Skog's care.

I'll leave it you mate if you want to integrate the info or not.

The calculator that diego posted up is absolutely fantastic in that is show both wheel options side by side with both specs.

i.e. stock wheel/tyre/offset on left and modified on right, then underneath it expplains how much more or less room you would have inside and outside of the tyre aswell as how much more guard room you'd ned to find for a larger diamter...really good explanation.

If Skog could add the link to his tyre bible aswell as the charts above it would be great. It can only benefit.

i.e. stock wheel/tyre/offset on left and modified on right, then underneath it expplains how much more or less room you would have inside and outside of the tyre aswell as how much more guard room you'd ned to find for a larger diamter...really good explanation.

that is what i think is the best part

im glad you like...

Thanks Brendon. You beat me to it.
Diego. Thanks mate what a great calculator... It explains things well and gives some great comparisons. Ive got a bit of homework as I have to tidy up a few threads, I am going to try an Merge Steve9R's thread into this as well. Then link it all back to the tyre bible thread... And have to go through an edit that as well....... Geeze this MOD gig is bloody hard work....
Cheers
Skog

FYI

NSW RTA Website


http://www.rta.nsw.gov.au/registrati...vsi09_rev4.pdf


Regards,
Marcelo

Chancha_Blanca wrote:FYI

NSW RTA Website


<!-- m --><a class="postlink" href="http://www.rta.nsw.gov.au/registrati...vsi09_rev4.pdf">http://www.rta.nsw.gov.au/registrati...vsi09_rev4.pdf</a><!-- m -->


Regards,
Marcelo

linkie no workie

Just a quick question, what is the profile of a 205R/16C?

I can't find the answer anywhere.

Sam

sam
i'm not sure about the aspect of the 205r/16 its somewhere around 80 i think but the original tyres are 738 or 739mm in diameter
just look them up in bridgestone site
cheers
ken

oldrev wrote:sam
i'm not sure about the aspect of the 205r/16 its somewhere around 80 i think but the original tyres are 738 or 739mm in diameter
just look them up in bridgestone site
cheers
ken

I was just doing the 5km odo check on the freeway and came up only to 4.75km on odo, so give or take a little, 5% difference

I was checking the tyre calculator site as i have 245/75/16 and compared to 205/80/16 it is 5.5% difference.

So for fuel consumption checking I have to add 5% on to total distance on odo.

Sam

Sorry to bring up a dead topic, but I found another tyre size calculator, just input the specs of the tyre&rim and it gives you diameter, circumference and rolling radius

http://www.exploroz.com/vehicle/tyres/sizecalc.aspx

Great find there whitey89.
For you first post that was an awesome find.
Cheers
Skog

Cheers Skog, I was working out if I could fit BFGs to my lux I'm waiting on (even though the tyre supplier for BFG said they didn't have a 15" tyre) to get rid of the standard highway rubber without having to worrying about the boys in blue. Going to go with the 31x10.5R15 ATs

Hey guy's i've tried searching but to no avail! maybe someone can help me out here. I'm currently running BFG A/T 265/75/r16's on the Hilux and i have another set of wheels that i would like to fit two for my trailer and use the other two as spares for the lux. Now the problem i have is that 265's are a little to wide for the trailer and as the spares are required not only for the car but also for the trailer what size tyre can i put on the spares and trailer rims that are thinner but has the same rolling diameter as the 265's.
Hopefully i haven't confused you guy's

235/85x16's......

31.8x9x16

Thanks Mmaaxx

Here is another calculator that converts all different types of tyres.
Very handy for comparing imperial v's metric

http://www.carbibles.com/tyre_size_calculators.html

Diego's first link is now dead..

Here is the replacement.

http://www.rimsntires.com/specs.jsp

Steve