D3's and 275X60X18 tyres

[cockie55]

Does anyone see any fitting problems with putting 275 X 60 X 18 rubber on a D3 instead of factory 255 X 60 X 18???

For instance spare wheel well size appears to be capable of handling the extra diameter but I am not sure.

Thanks

[WhiteD3]

There's some threads on the subject here in the D3 Zone but I'm pretty sure they won't fit (at least inflated) in the spare wheel well. Also in QLD they're illegal, being > 15mm wider than the factory fit:(

[cockie55]

Thanks for the heads up WhiteD3. I stumbled accross this interesting info.

NextStepDesigns Blog Archive LR3 wheel & tire specifications and options (http://blog.nextstepdesigns.com/?p=46#comments)

[daveyb]

I have 285/65/18's stuffed up there. 18psi and remove the rubber bump stops. She'll fit - just a bit cozy!

[rob4play]

I went for the Cooper LTZs 285 60 18 and loved them on a recent high speed Gold Coast, Immaninka, Walkers Crossing, Birdsville, Big Red. Quilpie, Roma and back to Gold Coast trip, fully loaded with camper trailer.
See another post "Cooper LTZs" anyone tried them - I will update that one later this week re wear etc. My spare fits pretty easily with 20psi
The only thing the dealer senior service guy had to say was that they cannot be sure just how the DSC etc works with the oversize tyres i.e. desensitises etc and be aware that if you have a problem they will most likley not look at it till you go back to the original mfctr spec re size etc. So keep your originals. I replaced about 1/2 way through the life of the wranglers so I could keep them as a backup for this reason. For me thay have lived up so far to all the good reports I have read especially those out of the US. The blocks are spced enough that they throw out the mud rather than slicking up and deflated for sand just great. I just stayed in hi ratio 2nd and 3rd for Big Red and a doodle - no chipping from the hard stuff either. They do wear quicker than the Cooper ATRs or HTs though. On road have not noticed ad increase in noise yet and are really planted with very good braking. Rolling resistance is higher and fuel consumption does go up a bit even when you compensate for distance/speedo error due to the larger circumference.

[rmp]

It is easy to work out what oversize tyres do to DSC, and it's not desensitizing it.

DSC basically works by looking at what the car is doing -- yaw, lateral G, steering wheel angle and much more -- and also what speed it's going. Oversize tyres will mean the car is travelling faster than what the sensors say. Therefore, the DSC's calculations are thrown out and it won't make the corrections it needs to as it doesn't think it's going that quick.

Now what effect that has in practice is open to question. If the tyres are just a little larger or smaller that would probably be within a margin of error. But the greater the variation from stock the greater the difference. Hence, ESC-equipped vehicles are likely to have greater restrictions on mods than non-ESC vehicles.

[rob4play]

Hi Robert,
Sure I fully agree with what you say, really a play on words. I have an electroics engineering background with a lot of past history in complex systems both military and commercial. Suffice to say that without being privy to the actual software algorithms used etc it is only a best guess as to what the effect will be when you alter some of the parameters around which some of those algorithms etc were designed. My point I guess in saying desensitise is that assuming the responses and interventions are increased with speed the effect could well be with oversize tyres that those interventions/responses could well be reduced for the actual speed, given the system is fooled into believing it is travelling at a lower speed to actual.
Either way my experience to date fits with the thoughts of the dealer that no negetive effects would be experienced regarding system response while at the same time experiencing the very positive benefits (more specifically off road of course) of the larger tyre and more agressive tread pattern designed around a 70/30 ratio of road/sand to dirt/mud.
Interesting enough the dealer also stated that when setting up a brand new vehicle or changing between landrover wheel sizes, that is one of the parameters they are required to programme in for that vehicle. It may simply be to compensate and therefore take out any speed error that comes in with change in overall circumference and therefore keep all responses in line with actual road speed.
Not having seen the method of entry I would suspect that it is simply a standard set of limited choice determined by the OEM wheel and tyre sizes available. If you could simply program in the actual rolling circumference or diameter then the system should be able to compensate for any tyre size within reason that physically fits within the parameteters of articulation clearance etc. While there maybe other subtle differences to the vehicle goemetry under dynamic conditions such as yaw etc I would suspect given the nature of the vehicle it would have a minimal effect. For a race car pushing the bounderies of course a different scenario.
At the end of the day no matter the techno jargon etc the end result for me anyway is a huge improvement over the OEM tyre option both on road and off. I have forgotten but off the top of my head the difference in circumference is around 4.7% larger and this was borne out when comparing speedo readings in convoy with 2 other TDV6s both with 18" wheels and new Wranglers give or take.

[rmp]

Hi Rob

Yep I agree with all that too! I know there are around 160 parameters for the ABS algorithim, imagine how many there'd be for ESC. I agree the effects would be minimal and ESC would still save your life but perhaps not in the very rare occasion where it would have done on stock tyres but not on oversize. But all this is speculation without testing. The ESC would have a margin of error as rolling circumference does change with tyre wear and inflation.

Interestingly a device to reset the speedo for larger tyres does exist for the JK Wrangler, important as those people are wont to fit tyres of 35" and beyond to their cars which is a significant difference to their standard 32". I can't see anyone going that much beyond the D3's stock size, so less of a problem here.

In fact, for the D3 I advocate keeping tyres the same diameter. Firstly that's legal, secondly no warranty problems, thirdly less drivetrain stress and less rotating mass, and no clearance issues, snowchains still fit, and I've heard of one D3 with oversizes that worked fine for ages and then, over a big, big pothole, bottomed out and broke a sensor somewhere. The small increase possible with the D3 doesn't translate to a lot of extra ground clearance (and g/c is diameter increase / 2 anyway), and the D3 does well on g/c as it is. I don't think the climbing ability of a oversize that'll fit the D3 is significant relative to stock either.

My $0.02 worth.

Note this is not to be confused with rim diameter, which is not at all necessarily related to overall tyre diameter. On that subject I'm all for 17s, if they fit your vehicle. Land Rover's push to fit ever-larger rims is wrong, or at least not providing the option of smaller ones for all models.

Also a more aggressive pattern and stronger tyre is definitely what is needed for touring.

A 275/65/18 is +24mm greater diameter than the stock sizes which are 763mm +/- 1mm, but actuals will vary dependent on the tyre and its tread wear.