Differing tyre size for spare

True. Another alternative is just to buy a tyre, and learn how to change it. Second-hand tyres in that size are a dime a dozen.

Yeah, a decent second hand 265/70/17 can be had for around $50 and is a lot lighter to carry without a rim. You can get it put on a rim at any of the little towns if it's needed and saves waiting for a replacement to get delivered. Get a plug tyre repair kit for most on the road emergency fixes. Make sure the tool is metal not plastic or it can snap off and you'll spear your hand. It's not pretty, I've seen it happen. The ARB kit is very good.

Thanks Michael H9. I have a good puncture repair kit but will it work on a punctured sidewall? I'm driving Mt Dare to Birdsville on the French Line & Rigg Rd and I can't see any small towns on my map. Are there places out there not on the map?

It depends on the size of the hole in the sidewall. It is not uncommon for them to be 20, 30, 50 mm long or even larger. If your repair kit consists of externally applied plugs only then they won't be able to do it.

If you are not familiar with all the equipment to repair tread, shoulder and sidewall damage then have a look through the Rema Tip Top and Beadell Tours website

I've seen 4 to 5 plugs put into a sidewall as an emergency repair. It's certainly not road legal of course but you can drive on it if you have to. You'd be very unlucky to get a sidewall stake on the main Simpson tracks, they mainly occur on overgrown or disused tracks or cross country travel. You can see them put quite a few into a Land Rover Discovery sidewall on Ron Moon's Great Australian Bight Youtube video but that was a really tough pretty virgin track.

As mentioned you need to stick with the same rolling diameter but I would seriously consider if you need to carry a second spare?
There is nothing between Mt Dare and Birdsville but on a trip like that I find one spare and a decent repair kit is ample.
Travel with what you feel comfortable with but I haven’t carried a second spare in over 10 years. For me the benefits of the weight savings outweighs the chance I would need it.

I'd carry a second spare and be done with it. The extra 30 - 40 kg is neither here nor there in the overall scheme of things.

Regards

It's here, around my waist....and my wife said I shouldn't be carrying it. :-)

This happened at Kidson Bluff, on CSR, in Aug, 2019. Continued to drive on it till about Halls Creek, adding a string or two, every day or so.



When travelling from Mt Dare towards Dalhousie, resist the temptation to travel on the short cut, and go through Bloods Ck. Less risk of tyre damage that way.

Bob

Thank you all for your replies. What prompted my question was the fact there is a 27mm diameter difference. I was thinking that equates to 13.5mm each side. Which is about the difference in tread thickness between a new tyre and a worn one. But I won't be doing that now. I will heed all the advice on this excellent forum.

If you use the second spare for emergencies only, and as you say in desert country, the the difference in tyre rolling radius won't cause you any mechanical problems. The tyres can 'slip' in the dirt and your diff will be working a bit harder, but no harder than when going around a corner when the inside wheel has to travel less distance than the outside wheel. I wouldn't mix those tyres on bitumen though or if you are doing lots of rock work where the tyres cannot 'slip' easily and if you get 'axle wind up' additional load will be placed upon the drive line. As others have said, a 265/70R17 tyre & rim can be purchased inexpensively say from tyre shops where ppl with too much money have traded in their tyres and rims for a larger size or a flasher set of mags, etc. In addition to carrying a tyre temporary plug kit, for emergencies, also consider carrying a few spare tubes, vulcanising or cold patches, some tyre sleeve repair material and an el cheapo lever operated bead breaker and rubber mallet. Also learn how to use them and how to mount and demount a tyre on a rim.

Yes a couple of hundred bucks isn't much in the scheme of things.

Economics comes into play as well. I was wondering around the Wheatbelt in WA the other day without two spares - Hardly "remote" so why bother. Got a flat (unfixable)...mmm, wasnt going home for another week or so and figured I couldnt drive around with no spare.

Of course closest town didnt have same brand/type and no second hand ones of a similar size. Solution...brand new tyre, same size another brand (mickey thompson). Cost $540. Yippee. Lesson learnt.

Moral of story, carry two spares when away from larger cities even if not "remote".

Cheers
Greg

You don't need a second spare until you really need one.
Dave.

Bob Y wrote “ When travelling from Mt Dare towards Dalhousie, resist the temptation to travel on the short cut, and go through Bloods Ck. Less risk of tyre damage that way.”

And takes around the same time. We pulled our Tvan through the rocky ‘short cut’ (& quite enjoyed it actually) but the advice from Bob is good. We didn’t damage any tyres, but the risk of doing so was high. Very rocky often difficult to see where the track was, & with some pretty good washouts to get around too. We went Dalhousie to Mt Dare, left at the same time as others who took the Bloods Ck route & we both arrived at Mt Dare within minutes of each other.

You can see the difference in size in this image. I would not mix these two sizes to avoid diff damage.

The OP already put up the difference in his original post - correctly in mm so why put this up - particularly in inches when the OP has already agreed that the difference is too great and is not going to proceed with his proposal.

@Ozziecruiser The other post does not show a side by side comparison . Many people refer to tyres and rims in imperial size especially the heights. When have you see are 16x8 rim referred to as 40.6cm x 20.3cm. So your post was totally unnecessary. I was only trying to help....the end

Well as the OP has already decided what to do - as I said your post is not needed - and the tyre sizes (not wheel size) he was talking about are metric so metrics should be used.

Yeh all good Dozer. I have 2 sets of 5 tyres. A set of 18" and a set of 17". The 17" which are almost new & 10 ply, get put on when I'm going on corrugations. So I was asking if when I put the 17" on could I use one of the 18" as a second spare. Thanks for your input.

I think the problem is mental. When you're remote and you kill a tyre, then you're remote without a spare anymore so the mind games begin. I had 3 flats in a day on the Oodnadatta Track once, and I didn't have an extra spare, but I got by with a repair kit and local repair shops.

I take your point - we had a puncture in Central Bolivia which we repaired, then 13 Km later another which was unrepairable. Then a couple of hundred Km (on the same surface which had given us 2 punctures in 13 Km) to the nearest village. They were unable to help, so another couple of hundred Km to a town where we were able to buy a new tyre (hauled in on "chicken run 'bus" from La Paz in two days). It was a little unnerving, as you say, however worked out OK.

PS: 42 deg C when we changed the unrepairable tyre...