Xoutpost.com - Maximum tyre (not rim) size (Updated with Pics)

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Quote:

Originally Posted by Cole (Post 661329)

Thanks, but this rather defeats the object though as I am trying to get more rubber between the rim and the road... not in terms of width, but in terms of distance from the tar. These options are just wider, but because of the lower profile the net result is that the rim is still going to be 6" from the tar. In fact the 275/55 profile tyre would put the rim slightly closer to the tar at 5.95". In terms of grip they would be better than my standard 235/65/17 tyres due to the bigger footprint, but they would not really offer better pot hole protection, which is what I need.

There is no option to achieve what I want without disturbing the speed calibration... but the average speedo in most X5's over reads by a few % anyway, and a slightly bigger diameter tyre will then actually improve the speedo's accuracy, providing you don't go too big, and then it will under read... (sorry officer but my speedo only said 120kmh... I am sure I wasn't doing 200!);)

I don't think it is appropriate to do that. By doing it, the vehicle height will be raised a little bit and it might result in unstable when at high speed.

Quote:

Originally Posted by rogerkiu (Post 661749)

I don't think it is appropriate to do that. By doing it, the vehicle height will be raised a little bit and it might result in unstable when at high speed.

Sure the vehicle will handle a little worse, but I do not believe it will be dangerously so, not if I only increase total diameter by less than 5%. The X5 with higher profile tyres should still be way better handling than an LT with leaf springs at the back!

In my circumstances I think it will be safer to have a bigger pot hole resitant trye, and to travel at moderate speeds only... after all I can't really fly down these road at 160kmh exactly because of the possibility of wash aways. It is all about compromise, I am not for a moment suggesting that anyone else should do this unless they live somewhere where their roads are unreliable like here.

Quote:

Originally Posted by Cole (Post 662002)

Sure the vehicle will handle a little worse, but I do not believe it will be dangerously so.

:iagree:

You'll compromise the steering precision and the stability to a slight degree, but nothing you can't drive 'around'. If you go the LT tyre route, the biggest problem will be speed rating although there are LT tyres with a H rating which I presume will suffice.

Cole,

This site is handy for checking the relative size of tyres with regards things like rolling circumference, rolling radius, tyre volume etc.

TRC Calculator

Thanks, that site is quite useful... I can remember enough school geometry to do the theoretical circumference calculations based on the tyre size, but what is useful in that site is that they can estimate the dynamic behavior of the tyre under load. It will give a better guide to the amount of speedo and odo error I can expect.

I haven't got around to putting new tyres on yet, I am trying to streeeetch my current set for as long as possible.

Easier than getting the slide rule out!

Ok so now I have bitten the bullet and fitted some bigger tyres. Got stuck in the mud a week or two ago trying to get up to a friend’s mountain cottage and wrecked one of my tyres in the process... so had to get new ones anyway, and after a lot of searching around I finally opted for Pirelli Scorpion ATR 265/65/17.

These are semi off road tyres and will not be to everyone’s taste… and before you all go on at me, I know I have sacrificed on road handling and I know my speedo and OBC will now be affected. I am, however, actually quite pleased with the ride and handling. The tyres are quiet, and the ride is smooth and even a little softer than the standard tyres where (235/65/17).

I had the bass boat hooked on the back this weekend and had to take some serious evasive action to dodge a tractor and trailer (no lights!) in the middle of the road, and the X still handled it really well. I think if I had of been in my old Isuzu KB300 I may not have got away with this, and may not have been here today to write this!

My speedo is now almost exactly accurate when compared to GPS speed, but the odo and OBC now under read by about 5%. The OBC and odo error is not ideal, but I know the error and can compensate for it.

Ground clearance is up by ¾ inch and this is all rubber between the rim and road, as per my original objective...

Intersting that your 265 tyre doesn't seem really too big for your original rims. Mine are 275 and look like balloons! But I use them for the same reason as you, just to cope with the bad state of the roads around here, and also to lift up the ground clearance a bit when the hurricane season occurs.

Cool picture, the one with the red mud all over the tire. :thumbup:

Quote:

Originally Posted by Cole (Post 720693)

Thanks for the update.

I've also got Scorpion ATRs on my 3.0d, but in the standard 235/65 size. I think that they are an excellent tyre as they give nothing away to the OEM Michelins on road in terms of noise, ride, grip etc but are far better on gravel, dirt, mud etc.

Nice to know that the 265s fit okay.