Does offset help or hinder tyre clearance?

[twodoorgaz]

Struggling to get my head around whether changing wheel offset helps or hinders when it comes to tyre clearance.

 

We have 265/75/R16 tyres on boost rims on our 90 currently which obviously clear fine, being a LR standard fitment on some of the older and NAS models. I’ve been saving for a set of the 8x16 rims from Nakatanenga which are ET0 - so the outside wall of the tyre would be pushed outboard by 33mm (boost offset is 33mm, the 8x16s are 0mm).

 

I've heard of people having issues with larger tyres touching the rear lip of the wheel arch spats at full compression off road - usually with the larger diameter’d but narrower 255/85s.

 

I just can’t understand whether the offset (similar to fitting a set of wheel spacers) would make tyre rub concerns better or worse.

 

any pointers in understanding this?

Edited September 4, 2021 by twodoorgaz

[Bowie69]

In that specific case, yes it will make it worse, as the wheel travels further backwards for a given steering lock with more negative offset. 

Too many other variables to be sure much else, tbh. 

[landroversforever]

To give you some idea, with my suspension work I needed 60mm of extra width each side (120mm total for the axle). Having that as 60mm of wheel spacers on one side equated to about 20mm more movement of the tyre at the extremities front/rear. Swapping that to widening the axle inside of the swivels gave that space back at the front and rear.

Spacers in my case gave tyre to shock turret and spring seat clearance at the worst case position. They’d normally give you more clearance to the radius arms too. But will mean the outside of the tyre swings a bigger arc. 

[Escape]

On full compression the tires tuck into the wheel wells. Wider tires or a wider track will reduce space available, so more chances of interference.

[simonr]

As you increase the offset, the wheel will move forwards & backwards more, reducing clearance in the wheel arch.

However, much of the time, the issue is the tyre hitting the radius arm - and increasing offset will improve that.

It will also increase the load on the wheel bearings, make the steering heavier and increase bump steer (the steering getting pulled when you go over a bump) - so I would limit the offset to the minimum possible, unless you are going to lengthen the axle.

[Snagger]

As Simon says, offsets via nonstandard wheels or spacers increase steering, bearing and stub axle wear and will increase the pull from any road defect (pot holes, slick pots, bumps), tyre issue or uneven braking exponentially, as well as running into body fouling on large suspension articulation, so you are wise to minimise it.  What you are planning is pretty reasonable, if you really need such wide tyres (which reduce grip in mud, on wet roads and increase drag in soft sand).  If you do fit that wheel and tyre combination and do have fouling issues, you’d either have to adjust the steering locks, or could fit extended bump stops.