Read somewhere that increasing wheel size means having lower profile tyres and hence worse offroad performance. Is it possible to increase wheel and tyre size to give better offroad performance? Will this change the accuracy of the speedo?

Karlos wrote:

Read somewhere that increasing wheel size means having lower profile tyres and hence worse offroad performance. Is it possible to increase wheel and tyre size to give better offroad performance? Will this change the accuracy of the speedo?

If I used a FL2 off road I would certainly fit slightly larger tyres with an AT or MT pattern, even an extra inch of clearance would help and would only slightly affect the speedo. Ideal situation is to have a spare set of wheels for off-road as I do with my Disco 3.

BFG's and certainly Coopers are available in 17" sizes.

The speedo accuracy should not be drastically altered as the rolling radius for a 1" larger rim and matching tyre should be almost the same.

Although the tyre and rim go up in internal sizing the sidewall height decreases slightly (detailed as a percentage of the tyre width) and thus the rolling radius remains close to the original.

As for offroad I have no idea about the real world of offroading ....but I can imagine that a larger and/or wider tyre can only help due to the increase in contact area and therefore more grip....look at them Icelandic hill climbing things.....however if you need to lower you tyre pressures (For driving on sand and snow) then a lower profile tyre will give you limited options.

Cheers cotefarmboy!! Talk me into going off road then tell me I have no flamin' ground clearance.....I'll book the bodyshop geometry realignment before we go

You won't need the extra ground clearance for most of Tong, I just like to tackle the really tricky bits.

With Terrain Response and off-road tyres (more for grip) you will be surprised how far you can go. You might ground it a bit but don't be put off by the noise of it scraping the ground here and there, the engineers design all Land Rovers so the critical stuff is tucked up out of the way.

Wish 'Mother Nature' had when she designed men..........or coz she was a bitch thats why she designed us with our critical bits hanging low .....small mercies that she didnt work for Land Rover then

Thanks for the replies.

Based on circumferance I estimate that change in speedo will be approx 5% per inch of increased outside diameter. Going up an inch seems hardly worth it and 10% change in speedo I dont think I could cope with. Was sort of hoping there was a way around this. Couldnt cope with the cost of 2nd set and changing wheels to go off road. So I expect Ill stick to the standard that comes with the Freel2. Probably alter the balance anyway.

Freel2 SE comes with 17" and HSE comes with 18". Was told I could go upto 20" with aftermarket but if they all have the same outside tyre dia and only tyre profile changes then best to stick to the 17".

For your interest: Car sales indicated getting SE with 18" or 19" would cost extra $Aust6000, but could get aftermarket 20" for about $3000.

Karlos wrote:

Based on circumferance I estimate that change in speedo will be approx 5% per inch of increased outside diameter. Going up an inch seems hardly worth it and 10% change in speedo I dont think I could cope with. Was sort of hoping there was a way around this.

To save you time, just enter the original and new tyre sizes in here and it will do the rest

http://www.miata.net/garage/tirecalc.html

cotefarmboy wrote:

To save you time, just enter the original and new tyre sizes in here and it will do the rest

http://www.miata.net/garage/tirecalc.html

Good find.....I was looking for something similar to prove the point.

Gambba, with all due respect of what you say, but you foget that with increasing tyre sizes the flatness of the tyre will decrease. Example: normal tyre 235-65-17, bigger tyre 235-60-18, even bigger tyre 235-55-19. so the balancing factor is the reduced width of the tyre to stay within the correct speedometer reading.

YF

yamaha-fan wrote:

Gambba, with all due respect of what you say, but you foget that with increasing tyre sizes the flatness of the tyre will decrease. Example: normal tyre 235-65-17, bigger tyre 235-60-18, even bigger tyre 235-55-19. so the balancing factor is the reduced width of the tyre to stay within the correct speedometer reading.

YF

You've lost me........

What do you mean by flatness? If you mean this in terms of contact area with the ground when having a lower profile tyre then you have a point and that is why I mentioned tyre pressures.

The width of the tyre is 235 in the case of the LR and this does not need to reduce as you say, so I am not sure what you mean. The reducing figure is the side wall height which is shown as a percentage of the tyre width. If this is what you meant then that is what I already said.

keep it simple chaps, enter the tyre size currently fitted into the calculator (link above) then browse for the new tyre that you want and pop that in. Check the difference in diameter and make a decision. Job Done.

I've considered spare set of wheels/tyres for use at play time!!

Like the idea of getting a bit more ground clearance, but in achieving that I'd up the gearing a little bit (hence discussion about speedo accuracy, but that wouldn't matter off road). I do have a concern that increasing the gearing would have an adverse effect on low speed performance. First gear isn't exactly 'super low' to begin with so anything that pushed the ratio up is porbably not a good idea.

I'll see how we go at Tong at the end of the month and see what others there think.....

By the way, I've taken my wheels off a couple of times already, to clean them after play time. The standard jack isn't perfect but I didn't have any problems using it to take all four wheels off in quick succession.