Hi all just wanted some advice on tires.wheels on my BA Ute is it ok to run 235/55 on the rear and 235/40 on the front. its about a 60mm difference in overall size does this cause any problems any advice/opinions greatly appreciated by a noob, cheers in advance.

I am 99.9% sure you will have issues with the ABS. The ABS will (possibly) throw a code beacuse the sensors will be reading too far out. ABS light on = No ABS, No cruise control, unroadworthy. You could get around this by a custom tune and changing ratios in the tune.

100% issue you will have will be legality. Download QLD VSI 19.6 (from here; https://www.tmr.qld.gov.au/Safety/Vehicle-standards-and-modifications/Vehicle-standards/Vehicle-standards-instructions) and you want to read pages 10 to 12 regarding tyre.

Yes good point if I had ABS, I have one of those rare BA's with no ABS, I took it to a tire specialist today and he fitted 245/40's to the front and left 235/55 on the back did all the load calculations checked all the rules and said I'm all good. I even like the look of it but the bA trays are sort of half truck half car anyway. only side effect with the huge back tires is my speedo is about 8% out so at 100km/h i,m actually doing 108km/h but I'll manage that.

But he thanks for your reply.

Spoke to the inspector at Queensland transport and he said I have to fit 245/50 and to the rear and 245/40 to the front which ends up the same diameter as 235/55 anyway one of those rules with no real purpose apparently, basically your front and back have to be no more than 10 difference on the profile even though this means nothing without the tire width as a reference, what a pain.

That 10% aspect ratio law is mentioned in VSI 19.6 (I did say to read it above) but least you don't have an issue with the ABS.

Yes, thanks for your info that's what prompted me to talk to the inspector, now I'm having trouble finding the right tires for the back due to needing a 900kg load rating as the ute is a 1 tonner looks like it's going to cost me big money for the right tires as my tire guy told me that low profile doesn't have that sort of load rating, might have to look at some 265/50's for the rear. The irony of that is they will have a bigger diameter than the 235/55 I'm running now, as I said a rule with no real purpose. But that's life where at the mercy of the regulations.

But thanks your info was spot on.

Why not just 235/45 on the front with the 235/55 on the rear.

This limits the profile change back to the max allowable 10% as well as keeps your load rated rear size. Happy days.

BTW, the rule has a purpose. It so the tyres don't react too differently to steering inputs /direction changes front to rear, this really matters at speed.

What size wheels are we talking about 17" or 18". If 18" that size may be too tall on the front.

Not that it makes much difference but 850kg load rated (102) spec tyres satisfies the 1 tonner requirement.

P.S. My BA RTV has tall 225/70/16 (28.4") fronts and 235/70/16 (29") rears. The front size is only possibly due to lower offset wheels, moving the tyre away front the ball joint. An equivalent 18" rear size would be 255/55/18.

235/45 are actually bigger in the overall diameter of wheel and tire I only have 2mm clearance on the top balljoint with the pro fitted 245/40.
Decided to put 265/50 on the back. I can get them in a 900kg load limit. Because it's a one tonner I can't put normal 700-750kg rated tires on the back.