Thread: New Boots for D4

Originally Posted by Odysseyman

I believe it’s the longitudinal spread that matters in all situations. The lateral spread is not helpful other than to make the sidewalls even more vulnerable. The chunky tread on the sidewalls will only help protect the sidewall, not provide significant grip, and is more decorative than anything else.

cheers
David

Are these LT's? They tend not to bag as easily and require very low pressures to extend the footprint...but yes 60 profile isn't ideal versus the width or sand work. I now have to deal with stock 265/60/18 and in2 minds about where to go with them. I am thinking 265/65/18 although not much in LT in that size. Going to 275/65/18 is ideal and lots of choice but another inch bigger also saps a little grunt (even off road low range) and increases fuel use. Life is a compromise. Happy problem to have tbough. Cheers

Originally Posted by Tombie

2psi equates to roughly a 0.062” diameter change

Thanks Mike. Can you expand on this and detail where this is derived from so I can understand it better? The reason I ask is because my experience has been that different tyres can behave quite differently regarding sidewall height / rolling diameter vs pressure and also that the relationship between rolling diameter and pressure is non-linear with much bigger effects at lower pressures and minimal effects at higher pressures. The difference between 30 and 40psi is negligible compared with 15 to 25psi, for example. My Radar R5s on the Disco (235/85R16) barely deflect even at very low pressures due to the bonkers sidewalls, where the previous KL71s behaved more 'normally', as did the Goodyear's, BFGs, Coopers, etc run before them. To get to the 75% sidewall height point (sand) I need to run the Radars down to 7-8psi, at near GAWR loading. The others would be at around 14-18psi to get to the same deflection.

My 285/60R18 Falkens are a 31.5"/799mm OD tyre. This compares with my 265/60R18 Achilles spare at 30.5"/775mm. Their true SLR (static loaded radius) at typical loading and road pressures is 385 vs 373mm, a difference of 12mm, or 3%. Most ABS-based traction/stability systems can operate correctly (are essentially insensitive) within a ±6% window, although I understand the LR ones to be a bit more temperamental but haven't experienced that myself as yet.

To clarify I can't see me needing my spare on-road as I run decent tyres that never get more than a few years old nor wear more than a few mm, have a TPMS, carry compressor & plugs at all times and generally pay attention. The Disco is an occasional use toy that only ends up doing 10-15k on a set before replacement and the Rangie is a post-COVID work-from-home low-mileage plaything now. It would be an unexpected off-road catastrophic failure (ie. stake through the sidewall) that would necessitate fitting the spare so would be at low speeds and with the ability to manage the situation (to an extent).

Having said all the above I do recognise it's a bandaid approach and not ideal. Having a matching-sized spare is the best approach, and your spare should be your best (most capable) tyre in my opinion. How's that for preachy hypocrisy ?

You understand me perfectly ozscott, the 255/60R18 Pirelli AT+ are not LT but strangely enough have a higher load rating than the 265 version, but a 265/65, thanks I will have a look and see what I can find. I am not too concerned about LT specifically, as long as the load rating is correct, the current AT+ has certainly held up well and I can certainly say small bump harshness was significantly improved with the AT+ over the D697 which are LT.
275/65 sounds interesting but I suspect same problems with fitment as 285/60, but worth a look, as you said, compromise.


.

Originally Posted by ozscott

Are these LT's? They tend not to bag as easily and require very low pressures to extend the footprint...but yes 60 profile isn't ideal versus the width or sand work. I know have to deal with stock 265/60/18 and in2 minds about where to go with them. I am thinking 265/65/18 although not much in LT in that size. Going to 275/65/18 is ideal and lots of choice but another inch bigger also saps a little grunt (even off road low range) and increases fuel use. Life is a compromise. Happy problem to have tbough. Cheers

Originally Posted by ozscott

Are these LT's? They tend not to bag as easily and require very low pressures to extend the footprint...but yes 60 profile isn't ideal versus the width or sand work. I now have to deal with stock 265/60/18 and in2 minds about where to go with them. I am thinking 265/65/18 although not much in LT in that size. Going to 275/65/18 is ideal and lots of choice but another inch bigger also saps a little grunt (even off road low range) and increases fuel use. Life is a compromise. Happy problem to have tbough. Cheers

Yes, they are LT’s. Both LT265/70 x16 on my old Ford Ranger and LT255/55x19 on my D4.

I would be much less inclined to run ultra low pressures on tyres that were not LT. Even some AT tyres would be vulnerable IMHO.
David

Went for 265/65r18 Nitto Ridge Grapplers. So far a very very nice tyre. 122 load rating and handling onroad better than the HT's. Updates to follow after more miles. Cheers

Originally Posted by ozscott

Went for 265/65r18 Nitto Ridge Grapplers. So far a very very nice tyre. 122 load rating and handling onroad better than the HT's. Updates to follow after more miles. Cheers

They look good

Originally Posted by ozscott

Went for 265/65r18 Nitto Ridge Grapplers. So far a very very nice tyre. 122 load rating and handling onroad better than the HT's. Updates to follow after more miles. Cheers

I was after those as well,but with a six month wait,minimum,for the size I needed,I moved on to the tried and tested KO2.
Lots of great reviews on the nitto.

The Nittos were good on the wet tarmac the other day. A lot of feel once you push them. Cheers