Disco 2 265/70r16 on standard height DII?

Stanleysteamer said:

Yes we got it! You don't get Disco 90s!!
Yours must be either an Anniversary model or a yank or a special, or a very late and very expensive one.
(Lost interest now.)

Click to expand...

+1 ...though what has a ''90 auto'' Defender which LR has never made automatic from factory with a D2 which is the subject of this thread ?.... some guys just want to seem interesting while it's not the case and that IMO full of sh*t reply was for no practical use... unless the OP wants to defeat a ''Landcruiser"

Interesting thread (in parts)
So is the bigger tyres likely to put any more strain on the vehicle than you would towing?
Is it likely to have such a vast effect going a little bit bigger? Are these theories or practical evidence based on using these sized tyres from personal experiences?

andy85 said:

So is the bigger tyres likely to put any more strain on the vehicle than you would towing?

Click to expand...

Not more but maybe the same... depends on the trailer's weight and the vehicle's tyre's size.... IMO on 265/70/16 it's aprox like with a 1.5 T trailer without being one hooked

andy85 said:

Are these theories or practical evidence based on using these sized tyres from personal experiences?

Click to expand...

Did you read this whole topic?... i think that the link in post 4 is clear that it's personal experinence confirmed by gauges mixed with technical arguments based on hard study... most of the ''smart guys'' who are stating that bigger tyres on a untuned D2 Td5 are not an issue haven't ever seen an EGT gauge .... btw, do you know what EGT means without searching on the web about it ?

Iv not read the link yet no,but I sure will be doing so later.
Yes,exhaust gas temps,something I’ve seen yourself post about a hell of a lot on here,which was the reason behind the question of is it any more strain than a trailer for example .
I realise there’s many variables involved,but an extra 1.5t worth of theoretical strain is quite a lot
I’m due to get myself an egt gauge and rig it up,this has reminded me to.

andy85 said:

Interesting thread (in parts)
So is the bigger tyres likely to put any more strain on the vehicle than you would towing?
Is it likely to have such a vast effect going a little bit bigger? Are these theories or practical evidence based on using these sized tyres from personal experiences?

Click to expand...

Strain on the vehicle is a difficult thing to quantify. Bigger tyres and pulling a trailer are different things. And of course what weight of trailer?

Bigger tyres effectively increase your overall gearing. So you will get higher mph per 1000rpm. i.e. you'll be able to cruise at the same speed but with less revs on the engine. The downside is, taller gearing can blunt acceleration and you may find in some situations you don't have the power to pull the gearing successfully or need to drop down where you didn't before.

However in defense to this example. The D2 with either the Td5 or RV8 should have more than enough power in stock form to pull these tyres. And the tyre size is no overly big. It is in fact a standard Defender tyre size. While the Defender and Discovery run different transfer box ratios, there is a well established practice for several decades running a tyre of this size on Range Rover classics, Discovery 1's and Discovery 2's. All of which have similar gearing and kerb weights.

For towing, the main issues are likely to be a slightly taller 1st gear when pulling away, which may result in slightly more clutch slip. Not a problem for a caravan or occasional towing, but if you tow 3 - 3.5 tonne regularly, you might want to consider all options. Also the taller tyres will raise your rear tow hitch, even more so if you combine them with a lift. Without a drop plate or similar, you may find t harder to tow some trailers correctly.

As for the differences going for a bigger tyre. They will give you more clearance, and are in many ways the best for of "lift" you can give a vehicle. You'll increase ride height below the diffs, but also the sills and chassis rails and the front/rear bumpers. Thus improving approach, departure and breakover angles off road.

Larger tyres also tend to roll over the terrain and obstacles better too, especially with a relatively large and heavy vehicle. This isn't to say smaller tyres can't perform, but as a rule a taller tyre is likely to perform better in many situations. A taller tyre while retaining the same rim size will also provide more benefits when you air down, as you have more sidewall and will have a longer footprint.

300bhp/ton said:

As for the differences going for a bigger tyre. They will give you more clearance, and are in many ways the best for of "lift" you can give a vehicle. You'll increase ride height below the diffs, but also the sills and chassis rails and the front/rear bumpers. Thus improving approach, departure and breakover angles off road.
Larger tyres also tend to roll over the terrain and obstacles better too, especially with a relatively large and heavy vehicle. This isn't to say smaller tyres can't perform, but as a rule a taller tyre is likely to perform better in many situations. A taller tyre while retaining the same rim size will also provide more benefits when you air down, as you have more sidewall and will have a longer footprint.

Click to expand...

I think the benefits of taller wheels and higher profile tyres are well understood. What is clearly not appreciated by the majority of drivers (myself included until reading this thread) is the increased strain on the engine and the reduced longevity and reliability that may result. You are right that measuring engine strain is not straightforward, but EGT is a reasonable one given that it directly provides warning of a potentially damaging situation.
These tyres are indeed standard fit on Defenders, and as you say the gearing difference is offset by the gearing in the transfer box. So presumably those who fit Disco transfer boxes to Defenders with standard tyres are also at risk of over temping their engines.

300bhp/ton said:

And the tyre size is no overly big. It is in fact a standard Defender tyre size. While the Defender and Discovery run different transfer box ratios, there is a well established practice for several decades running a tyre of this size on Range Rover classics, Discovery 1's and Discovery 2's.

Click to expand...

i respect your opinnion and the rest of your post has a kind of logic for me ... though the gist of it is that nor RRC, D1 and Defender Td5(same engine /different management) have VSS involved in the engine management like the D2... and as i have EGT gauge and ECT gauge too i can say that i've seen the aprox same readings with my loaded boat attached(Shetland 560 with Suzuki 4 cyl injection engine... about 1.5 T all in) on 255/65/16 tyres like with no trailer and same vehicle on 255/70/16 .... so as i can trust myself and made various tests with nanocom live data too i insist... DONT MESS WITH TYRE SIZEZ ON A DISCOVERY TD5... PERIOD ... if you want to compare the D2 Td5 with other LRs compare it with those which have the VSS involved in the management, i insist on the link from post nr 4 in this topic https://www.landyzone.co.uk/land-rover/255-65-or-255-70-pros-and-cons.292220/#post-3620824 and the copied thing from WSM in 9 https://www.landyzone.co.uk/land-rover/265-70r16-on-standard-height-dii.351209/#post-4672032 before other comments. in the end i can say just: "To each his own"

Si Click said:

I think the benefits of taller wheels and higher profile tyres are well understood. What is clearly not appreciated by the majority of drivers (myself included until reading this thread) is the increased strain on the engine and the reduced longevity and reliability that may result. You are right that measuring engine strain is not straightforward, but EGT is a reasonable one given that it directly provides warning of a potentially damaging situation.
These tyres are indeed standard fit on Defenders, and as you say the gearing difference is offset by the gearing in the transfer box. So presumably those who fit Disco transfer boxes to Defenders with standard tyres are also at risk of over temping their engines.

Click to expand...

I struggle to believe stock tune Td5's are getting excessive EGT's just because of a slightly bigger tyre.

It's not as if the Td5 is only a couple of years old. People have been modding them for 20 years now.

A friend of mine runs a modded Td5 in a Defender, with an extra tall 5th gear, which gives similar mph/1000rpm in top as a 1.2:1 transfer box would. In all cases his EGT's are well in check according to the gauge he has fitted. Even when touring in Tunisia and 4 hour plus 80mph cruising runs.

300bhp/ton said:

A friend of mine runs a modded Td5 in a Defender,

Click to expand...

.. OK m8. then keep comparing the Defender with the D2 despite of the facts from my own findings which i revealed and the technical backup which i supplied... or just simply call me liar ... if nothing bad happens in 50K miles doesnt mean it's OK, it's only a warning for those WITH UNTUNED vehicles, take it or not.... depends how long each owner want to keep his vehicle without complete overhaul...i hope i'll be buried in mine as it is

sierrafery said:

.. OK m8. then keep comparing the Defender with the D2 despite of the facts from my own findings which i revealed and the technical backup which i supplied... or just simply call me liar ... if nothing bad happens in 50K miles doesnt mean it's OK, it's only a warning for those WITH UNTUNED vehicles, take it or not.... depends how long each owner want to keep his vehicle without complete overhaul...i hope i'll be buried in mine as it is

Click to expand...

I don't believe I called you a liar or even anything remotely close. I didn't even "quote" you

300bhp/ton said:

I don't believe I called you a liar or even anything remotely close. I didn't even "quote" you

Click to expand...

I didnt say you did... but if you keep contesting my own findings(which i've sincerely revealed for the posterity) you'll have to

sierrafery said:

I didnt say you did... but if you keep contesting my own findings(which i've sincerely revealed for the posterity) you'll have to

Click to expand...

I think the info you provided is very interesting.

And I'm not disputing any of it on a technical basis. Only that the D2 has been about since 1998 and people have been modding them for a long time. Not just here but in the USA too (V8's not TD5's, but they must use the same TCS/ABS). And I'm surprised if it such a potential issue, that more isn't said or made of it. And not just with Land Rover's, but all the other makes of 4x4 that are modded with bigger tyres.

I did think your brake test was interesting, although 2 metres isn't a huge amount and could easily be caused by changes in the ground conditions, driver reaction times or the tyres.

300bhp/ton said:

Only that the D2 has been about since 1998 and people have been modding them for a long time.

Click to expand...

... also the LR forums are full of posts with cracked Td5 heads + HG failures + warped exhaust manifolds and too few owners who have EGT and ECT gauges fitted and in most cases those who have extra gauges have proper power tuning too... i'm wondering why?
i reiterate that i'm against bigger tyres on unmodified D2's not on tuned ones...

sierrafery said:

i reiterate that i'm against bigger tyres on unmodified D2's not on tuned ones...

Click to expand...

Noted.

I shall bear in mind in future topics. Thanks for the info and links.