Tyre width for Defender 110's

[Luke]

To throw a bit of light on the tubeless rim thing; insurance aside, it's the nature of the rim that causes the danger. Mass produced steel rims are simply two pieces of stamped sheet steel spot welded together. the join in the base of the rim is a fairly deep V; as the wheel turns, the bit of V facing the road is slightly more open than the rest, i.e. a given piece of tube will see the V opening and closing against it like a pair of pincers! This is true for quite a few production cars, hence the insurance blanket ban. I don't know about original equipment LR rims though. The relatively cheap white 5 spoke wheels are welded all round the rim so shouldn't present a problem. Imho, if you take a set of wheels proven with tubes the insurers won't even know. The only pb I see is the danger of pinching the tube during the wrestling match with the tyre levers. I've got split rims and I love them.
Tyre size: Rich mentioned in the Unimog post that he had searched for 20" mog tyres and wheels for his 101, which is essentially a series. Perhaps you could elighten us with your experiences Rich. Otherwise Michael has some fairly convincing arguments.
Good luck
Luke

[SandyM]

I believe that Land Rover Wolf rims are designed to be used with either tubed or tubeless tyres.

The bit about the vee in a tubeless-only rim opening and closing as the wheel rotates, and pinching the tube is interesting. Does that apply to alloy tubeless rims too?

Unimog wheels on a 101 would be interesting. The usual diameter of a Mog tyre is around 41"! Of course the tyres on a 101 are usually nearly 36" anyway, but that's still around 15% bigger...

Actually the 101 isn't really a Series vehicle. The chassis was entirely new, and the engine and transmission were taken from the Range Rover, though the diffs and shafts are Salisbury, front and rear. The diff ratios are very low, 5.4:1 (compared to 3.54:1 for Defenders). The low diff ratio has its own problems (a very small pinion gear).

I'd love to hear how it runs with Mog tyres though, Rich!

Regards,

Michael...

[Luke]

Alloy wheels are molded, of all the tubeless rims, they have the smoothest inside, therefore I would imagine they would damage the tubes the least. The spot welded rim is a design solution adopted to exploit stamping techniques already well known in the mass production car market where if you can save a penny a rim you've made a fortune. The piece of tyre in contact with the ground being wider, it puts a greater lateral force on that part of the rim. Perhaps less the case with tall tyres, I've only been involved with road cars (don't ever buy a Renault auto (
I'm not completely au fait with the LR time line, I've long laboured under the illusion that the RR took its bits from the 101; you live and learn :^)
Cheers
Luke

[Chris Scott]

Bigger and esp wider tyres ultimatly stress the wheel bearings - even on TLCs I have heard. But in my experience in the sand, the bigger your engine the less critical your tyre choice, pressure or even if you use low range or 4WD or not. 2.5s always get through the dunes, but need a fair amount of thrashing which sounds brutal when you're usd to 1500 rpm.
Standard 750s are fine otherwise they'd be using something better in the dz.
More ccs (and a trans to suit) make it easier. I have to say though, I used a Td5 auto up north and it never felt stretched like a Tdi even if I didnt find any decent ergs. Nor did anything break much in a hard month. It makes me wonder about LRs...

Talking of which, does anyone go for the side-to-side steering trick used uphill in soft sand to app'tly 'drain' away the build up of sand infront of the tyres? I keep forgeting to try it but I would have though it creates more drag, Is it all in the mind?

CS

[Andrew Baker]

Michael,

I am fully in agreement with your views on larger or wider tyres - yes it's easier and with less down side to go wider, which is what I may yet do.

I have heard of Disco's stripping their half shaft splines with larger tyres, but I think they have a smaller number of splines than 110's.

You say that if there is increased backlash in a diff, then failure becomes more likely. Does this also apply to factory or military reconditioned units, who have already had one life, where the gears are worn to some extent, but still usable? I ask because after last years trip to Algeria, my salisbury diff bearings became noisy, and the whole axle was replaced with a factory or military unit, the (ex-miltary specialsts) didn't know which. It was in a wooden crate, the axle covered in wax and complete with brakes, so maybe it was a factory job. It runs quiet until about 55 mph when it's starts to whine merrily on the over-run (under power at this speed it's ok). I've had recon gearboxes and transfer boxes in the past and they have all whined to some extent, allegedly because of the mix of gears form several units. I don't know if this argument holds with salsibury diffs though. I don't expect a sensible answer from the place I bought it from, what's your opinion?


Regards,
Andrew.
----------------

Chris,

If I remember correctly, we found ourselves frequently using the swinging steering wheel technique on the long steep dune climbs last year. As you start to lose traction you turn the wheel to either side rapidly and maybe you suddenly regain grip and surge off in an unplanned direction. It seemed that once you dig in to the soft sand going straight ahead you dug in further, like a submarine diving. Turning the wheel, you (usually) shot out of the rut of soft sand, back (if available) on to a firmer surface and kept on moving to the top. Possibly the distribution of soft/hard patches on certain dune ascents is more random than in a flat windblown area of soft sand, and so you have a chance to find firmer going by swinging the wheel. I'm probably talking total balderdash, but that's the impression I got at the time....

Regards,
Andrew.

Regards,
Andrew.

[SandyM]

Originally posted by Andrew Baker:
Michael,

I am fully in agreement with your views on larger or wider tyres - yes it's easier and with less down side to go wider, which is what I may yet do.

I have heard of Disco's stripping their half shaft splines with larger tyres, but I think they have a smaller number of splines than 110's.

You say that if there is increased backlash in a diff, then failure becomes more likely. Does this also apply to factory or military reconditioned units, who have already had one life, where the gears are worn to some extent, but still usable? I ask because after last years trip to Algeria, my salisbury diff bearings became noisy, and the whole axle was replaced with a factory or military unit, the (ex-miltary specialsts) didn't know which. It was in a wooden crate, the axle covered in wax and complete with brakes, so maybe it was a factory job. It runs quiet until about 55 mph when it's starts to whine merrily on the over-run (under power at this speed it's ok). I've had recon gearboxes and transfer boxes in the past and they have all whined to some extent, allegedly because of the mix of gears form several units. I don't know if this argument holds with salsibury diffs though. I don't expect a sensible answer from the place I bought it from, what's your opinion?


Regards,
Andrew.

Hi Andrew,

As a rule, the crownwheel and pinion should always be exchanged as a matched pair, and I think (I hope) that anyone reconditioning a diff would adhere to this rule. Having said that, I have no idea how bad it actually is to mix and match, and I'd have no hesitation in doing it in an emergency.

Diff whine on the over-run is often a sign of a worn crownwheel/pinion set, OR, in the case of a recon, it might be that the diff has been incorrectly shimmed. (There is a laborious process required to set the pinion depth, which affects how well it meshes with the crownwheel). Also, have you checked the oil level, and that you don't have gunk in it? These are not the only possibilities, however - see the URL at the bottom of this post.

I don't think the backlash can be checked in situ (but I might be wrong). If the whole diff is withdrawn as a unit (NOW you wish you had a Rover diff, not a Salibury!), a dial guage can be used to measure how much the pinion can move back and forth without it moving the crownwheel. Actually, if you play around with a "spare" diff, you can soon get to feel whether the backlash is within spec or not. It's worth checking it this way anyway, and comparing it with others that are known to be in good condition. There is a surprising amount of backlash allowed (and indeed mandated). Hence all that Land Rover transmission clatter if you blip the accelerator up and down while driving in a lowish gear.

Like you, I've had several Land Rovers (and other vehicles) which have had some diff whine, and lasted like that indefinitely. So unless there are some other symptoms, it might not warrant too much angst.

Hope this helps a bit.

Regards,

Michael

P.S. Also, see http://www.ring-pinion.com/tech.shtml

[rclafton]

Hi all

Yep - I run Mog tyres on my 101 now

They are about 37.5 inches tall compared to a standard bar grip being about 35 inches

The michelin 900x16 tyres (including XS's) are only about an inch smaller than the mog 20 inchers so its not that far out of spec really as its very common to run michelin xzl's on a 101 in 900x16 format and they measured when new to 36.5 inch

Unfortunalty I havn't tried these tyres in much serious sand yet - morocco supplied small dunes etc and the truck had no problem with these but no airing down needed.

My experience with continental bargrip tyres in 900x16 format is that they can be aired down to less than 10psi (in fact they have to otherwise they don't squash out as there so tough)

The concern I might have with mog rims & tyres is that the tyre is of a lower profile so the effect of airing down may be less on the footprint.

Would love to try the truck with a set of 900x16 xs's - anyone got room for a set in the boot the next time they pass genoa ?

The other advantage for me is that the mog tyres are cheap - 50-70 euros each

The other vehicles with me used either track edges (235/85) or wildcat all terrains (255/85)

If your spending some serious time in africa i think i would stick with the 235/85 as it can be replaced easily with a 750/16 (in fact 1 of my friends spares is a warn 750/16 nicked from John craddocks old tyre pile at a show)

The BFG track edges have shown themselves to be good tyres all round - good road manners, not bad in sand and will dig you out of mud. Run on landrover rims with tubes we have had 1 puncture in 9000 miles on trips - the wildcats on the otherhand produced 3 punctures in 1 trip




------------------
Rich
LR101 300Tdi Ambi 'Tiggurr'

[SandyM]

I don't think the lower profile of the Mog tyres would make for a significantly smaller footprint, pressures being equal. But the bigger diameter rims definitely reduce the chances of a low-pressure tyre coming off the bead.

For that, and other reasons, I prefer a bigger rim size, other things being equal (and of course, not to extremes).

[Andy Blois]

Backing up to the bit about LR transmissions. Coil sprung transmissions (90/110/RR/Disco) are just as liable to diffs breaking and shafts snapping. They look more reliable then Series vehicles because they are permanent 4x4. In my 90 I managed to ping every shaft and diff, one under warranty! In the end I fitted Ascroft shafts and Quaife diffs, cost a lot of money £500+ per axle, but never had to replace another shaft or diff. Quaife diffs centres were similar money to 4 pin Rover diffs and had added benefit of increased traction.

On the subject of gearboxes it is worth reading David Hatherill's piece on gearboxes in Camel Trophy vehicles <a href="http://www.worldoffroad.co.uk/showpage.asp?pageid=432">"Protect your Box"
</a>

Andy

[Yves]

7.50R16, 235/85R16 and 265/75R16 all have about the same rolling radius, so in emergency you can replace them with 7.50R16 which are available all over the world.

Bye, Yves

[SandyM]

[QUOTE]Originally posted by Andy Blois:
Backing up to the bit about LR transmissions. Coil sprung transmissions (90/110/RR/Disco) are just as liable to diffs breaking and shafts snapping. They look more reliable then Series vehicles because they are permanent 4x4.

They are more reliable because they are permanent 4x4.

Not only that, but they have much higher spec side shafts than the older series vehicles. And the diff ratios are 3.54 instead of 4.7, so they have significantly larger pinions. Finally, coils springs are generally a little kinder to transmissions than leaf springs, since most of the danger to transmissions is posed by shock loading.

Quaife diffs centres were similar money to 4 pin Rover diffs and had added benefit of increased traction.

I have no personal experience of the Quaife diffs, but they have a good reputation. Likewise, an ARB centre in a Rover-type diff makes it much stronger. However, the ARB potentially doubles the strain on some axle components, so it's a mixed blessing - you get the greater strength, but if you decide to use engage the lock, you might need the extra strength.

The Quaife won't put any additonal strain on any axle components, but like any friction-based TAD, it will sap engine power. At least with traction-control you can switch the damn thing off! :-)

Michael...


[This message has been edited by SandyM (edited 13 January 2003).]