Thread: Increasing Tyre Sizes on Models with ESC in Queensland

Hi, IMO those regulations should be your last concern, increasing the tyre diameters on vehicles which are using the VSS(vehicle speed signal) via CAN-BUS in all the system's managemenst(including engine, transmission and ABS) can have crytical effect for safety and lead to increased EGT, all those systems were ''calibrated" from factory for standard dimension tyres and pressures, any modifications will mix up the overall vehicle's behaviour. Read carefully the owner's handbook about tyres and you'll see that even incorrect pressures can be a problem. Fitting bigger tyres will give you ONLY more ground clearance eventually a ''macho" look while all the other systems will be affected including power and off road enhancements, think twice and make serious research about the impact before you play with the dimensions

Originally Posted by BradDS10

2. Has anyone contacted Land Rover and had success in them “approving” a larger tyre size (not likely I understand)?

Can you check what the factory approved "accessory" options for tyres were for your model / year. There maybe a 20" rim option that gives a larger rolling diameter, thus you've got your approval.

Originally Posted by Dorian

Can you check what the factory approved "accessory" options for tyres were for your model / year. There maybe a 20" rim option that gives a larger rolling diameter, thus you've got your approval.

Generally a rim diameter increase is matched with lower aspect ratio tyres to give the same overall roiling diameter.

Thanks for your replies so far guys:

Sierrafery - I don't disagree with you with respect to a considerable tyre increase but the sizes we are talking about are 22mm diameter increase (11mm ground clearance) from the largest diameter OEM option, I'd like to think most would agree is sensible and in the aim of achieving additional footprint on sand is a reasonable approach. I haven't considered this on a completely uninformed/ un-researched basis. There would need to be a decent range of tolerancing for the ESC wheelspeed (as affected by tyre diameter). When you consider the manufacturer in writing their algorithms for ESC needs to take into account many variables that can impact on the wheel speed - tyre wear, rolling resistance (as affected by different rubber compounds, tread patterns, pressures and brand sizing, as examples) different tyres pressures (including those unexpected from flats etc) and range of OEM wheels and tyre size combinations. There is a 3% diameter change from the largest OEM size availiable on the DS which is coincidently very similar to the OEM largest to smallest (smallest being the temporary use spare).

I am also aware of JLR using a 255/55/R19 on one of their demonstrator day Discovery Sports recently which is the same diameter as the 255/60/r18 I mentioned.

Definately an interesting topic to ponder on and discuss!


Dorian - Good suggestion and this is something I have already investigated, the largest diameter OEM on the DS at least is the 19 inch 235/


loanRangie - You're on the money they generally "adjust" the profile to get a similar diameter although the range of diameters seems to be 21mm from the temporary use spare

I have a set of wheels with larger 255/60/R18 than the 235/60R18OEM tyres

That's 3.25% difference, what i can say and that's tested is that i fitted 3.34% bigger tyres(255/70/16 instead of std 255/65/16) and the EGT increased with 100*C under load and the breaking distance with aprox 2m from 60km/h while the TC didnt work so well as before..

Hi sierrafery,
I appreciate your advice as it has plenty of logic and meritto it. However ultimately, like a lot of people (including no doubt numerousowners of vehicles with ESC on this forum) I am keen to use the bigger sizetyre. I am currently using a second set of wheels with OEM sized tyres as I amtrying to do things by the book and in line with my insurance.
The reference to 3% I made was “There isa 3% diameter change from the largest OEM size available on the DS”which is 255/60r18 vs. 235/55r19 and according to Page Not Found 2.7% which I simply rounded up.
I acknowledge you have done the testing for your vehicle andhave no doubt on your results given the scenario you tested. There are howevermany variables around this outside of simply the size: were the tyres of thesame brand/make, same condition (i.e. new), same type (AT vs. HT/ RD - impacts actual contact patch),comparable pressures, same environmental conditions, was the speed based on the speedo or Actual/ GPS etc. Like for like thelarger tyre should have better braking performance based on having a greatercontact patch (this is more relevant to a non-ABS vehicle but a sophisticated/quicker ABS system would also be impacted less). We are also comparingElectronic Aids and computers from 16 years difference to the D2 (which is afantasic vehicle btw – my dad has a ’99). I did do a few thousand k’s on the255’s and could not pick up on any differences with road (including wetweather) or beach driving except it had perceptively more grip. I do note your comments about exhaust temps an this is logical given potential different loading.
You have actually given me an idea, I might try to find somefree time over the next few weekends to test the two sizes on a quiet rd under60-0kph braking (noting that the tyre brand, type and condition is different).
J

Any Queenslanders knowledgable on this. Surely there are some Discovery 3/4 owners who are experienced on it?

Thans.

Just wondering if the road speed is actually taken into account, or does the system only monitor the ABS reading from each wheel, and ally that with yaw/accelerometer readings?
Is there any option in the management system (via IID/Faultmate etc) to adjust wheel/tyre size? Most vehicles offering optional wheels/tyres would need some form of adjustment.