Thread: Advice for Disco 4 Buyers

Originally Posted by gghaggis

fit 285/55/20 LTZ's

This size is theoretically 32.3". Does this size fit?
Should it be 285/50/20? These have 3mm (theoretical) taller sidewall than 255/55/19 - identical in my world.

Originally Posted by gghaggis

Agreed, but remembering that the real-world difference is smaller when considering AT-shod vehicles (which all touring cars should be) and that the additional ability/power of the 3.0 ltr D4 will more than compensate for the difference.

Cheers,

Gordon

OK well that moves it into a 3.0 vs 2.7 debate not a tyre profile debate as power has nothing to do with profile...and rim issues aside the 3.0 is a lot more expensive than the 2.7. For many that'll be the deciding factor, especially as the 2.7 has adequate power. I do love the 3.0, but on the other hand, it's a lot of extra money.

Doesn't the 3.0 also have a newer ZF gearbox than the 2.7? What is that worth in the real world of driving?

From Land Rover;
Fitted to both the automatic LR- TDV6 3.0L and LR-V8 variants, the upgraded ZF6HP28 Automatic Transmission features:
• Adaptive shift strategy which adapts to driving styles and surface conditions
• 10% faster shift response times (sport shift)
• Improved fuel economy through a wider range Torque converter lock up
The ZF6HP26 Automatic Transmission is fitted to the 2.7 TDV6 variants.

From Wikipedia;
ZF 6-speed auto
6HP19 — longitudinal smaller version of 6HP26
6HP21 — longitudinal 2nd generation of 6HP19 2007–
6HP26 — longitudinal 2000–
6HP28 — longitudinal 2nd generation of 6HP26 2007–[1]
6HP32 — longitudinal bigger version of 6HP26
6HP34 — longitudinal 2nd generation of 6HP32[2]

Originally Posted by wombathole

Doesn't the 3.0 also have a newer ZF gearbox than the 2.7? What is that worth in the real world of driving?

From Land Rover;
Fitted to both the automatic LR- TDV6 3.0L and LR-V8 variants, the upgraded ZF6HP28 Automatic Transmission features:
• Adaptive shift strategy which adapts to driving styles and surface conditions
• 10% faster shift response times (sport shift)
• Improved fuel economy through a wider range Torque converter lock up
The ZF6HP26 Automatic Transmission is fitted to the 2.7 TDV6 variants.

From Wikipedia;
ZF 6-speed auto
6HP19 — longitudinal smaller version of 6HP26
6HP21 — longitudinal 2nd generation of 6HP19 2007–
6HP26 — longitudinal 2000–
6HP28 — longitudinal 2nd generation of 6HP26 2007–[1]
6HP32 — longitudinal bigger version of 6HP26
6HP34 — longitudinal 2nd generation of 6HP32[2]

Off road all that transates to what ? I would think not a lot unless the conditions were pretty extreme. Perhaps we can persuade one of the mags to put the same tyre type and tread pattern onto a 2.7 & a 3.0 litre and do a comparison in extreme conditions.............but what would it really compare. The power, the gearbox or the tyre configuration. I suspect the gearbox used on the 3 litre has more to do with the power now being fed through it than anything else. ( particularly for towing )

As for the tyres, I will probably stay with the 18's on my D4, but look at a nominal increase to a 265/60. It has a minimal impact on rolling diameter. I have quoted this article previously, but check the December 07 issue of 4x4 Australia. A good article on low profile off road tyres, and one of the test vehicles is a D3. Yes it's old, but still a good read.

Overlander have stated that they will have a 2.7/3.0 comparison in a month or so.

The gear ratios for the 2.7 and 3.0 are exactly the same. Fuel economy is better or will be once the 3.0s loosen up, but not by very much in cruise.

Something else re low profile, they give a rougher ride than high profile. Again not saying they're bad, it's just another pro/con to consider.

Originally Posted by rmp

OK well that moves it into a 3.0 vs 2.7 debate not a tyre profile debate as power has nothing to do with profile...and rim issues aside the 3.0 is a lot more expensive than the 2.7. For many that'll be the deciding factor, especially as the 2.7 has adequate power. I do love the 3.0, but on the other hand, it's a lot of extra money.

Power and profile are somewhat related in terms of off-road ability, especially in sand. Up to a point, more power will compensate for the reduction in flotation. It's not just profile (sidewall height) that determines low pressure footprint. The radius of curvature of the tyre will also constrain the longitudinal footprint elongation, and for the same size sidewall, a larger diameter tyre (ie on a larger rim) will elongate further. So to a limited extent, the larger rim size compensates for the lower sidewall. Which is one reason why many people voice surprise at the lack of drama a 19" AT-shod D3 has in sand.

Where of course, low profile tyres are at a disadvantage, is sidewall and rim damage. Which is why I looked at fitting the internal beadlocks. They protect the rim and sidewall. Unfortunately there are none in the 19" size as yet, although Opposite Lock are looking into it for me (they make a 20" and a 19.5" size??!). Hence my comment on the 20" rim. But of course, that requires oversize tyres ......

As a tow vehicle, I'm sure the 3.0 ltr would be the better choice. And from all the above, I don't think the 19" rim will limit it in anything but serious off-road conditions (which is what I want to get around). Costwise I'm not sure about the D4, but doesn't the difference buy you a lot more than just the larger engine/gearbox?

Cheers,

Gordon

The cost does buy you more than just the engine, but even after you've added all the options to the 2.7 the 3.0 has it's still quite a difference. And add the cost of the tyres, 5 x 17 vs 5 x 19 (or 20). The difference is still several thousand and that's assuming you took all the 3.0 options which you may not want. For some that will not be any problem, for others they'd rather spend the money on tyres, bar, rack and carrier for the same price as another 40kw and 200Nm.

Re profile agree to some extent in principle - yes simply powering through at speed can see you across rather than going slowly relying on flotation. I do the latter all the time in my Defender ;-)

However, in the case of the 2.7 vs 3.0 both are pretty powerful and the power only makes a difference when you don't have enough of it, a car with say 200kw isn't necessarily going to have a massive advantage over one with 150kw, not like two cars with 100 and 150. As engines become more and more powerful they are output limited in the lower gears to the headline figure is rarely achieved. It also assumes that power can be brought to bear and in twisty inland tracks that is not necessarily the case. It's not unlike driving something like an M3 onroad, it's not often you can really utilise all that grunt. However, it's nice to have it.

Yes a larger diameter tyre will work better than a smaller one, but as you say that brings its own problems. I think a 19" rim is fine offroad....on a 37" tyre!

I agree the 3.0 would be the better towcar due to a much stronger engine. If all I was going to do was tow an onroad caravan that's what I'd buy for sure. Not that the 2.7's bad though.

A 19" D3 would be able to air down nicely and on sand the rim shouldn't be damaged...but do it often enough and sooner or later there will be damage.