Disco 2 Wheel/Tyre Options

I was given advice to start a thread for this, and it's good advice so here it is.

I have a D2 which is beautifully original. It's an 04 Landmark so it has 18" wheels, with badly worn 255/55/18 road tyres. I want AT tyres (BFG AT KO2 is what I have decided on), but I need to decide on wheel sizes. It's a huge spend to buy 5 tyres, and I don't want to make a mistake. So I am trying to get as much advice as possible before pulling out the plastic.

I have already bought some wheels from JohnLad on here. Lovely set of wheels, bought in haste perhaps. Not a problem, I will resell those if necessary. And at that point I am leaning towards thinking this is necessary, especially after reading countless old threads on this topic. The wheels are Disco 3 wheels. I have spigot rings as was told I would need those, but I didn't realise I would need new wheel nuts too, and then the tailgate spare carrier will need changing, and at this point I am starting to go off the idea in a big way. I have little spare time, even less spare money, and no desire to customise my Disco any more than necessary to get a nice ride with a bit of off road ability (a tiny bit). That also doesn't account for what may well also be necessary... modding the suspension/arches etc. I am told that won't be needed, but from what I have read, I think there is a chance it will be needed.

I can't find it now but I did just read a thread with a stick on it which was SUPERB. It explained in fine detail the issues, the changes etc, and going by that authoritative post, the wheels I have bought will definitely be oversized my my D2. This confirmed it http://www.discovery2.co.uk/tyresize.html

My 18" wheels with very low tread measure up at 28.5" overal diameter, but I think 29" is where they would be with the same tyres with new amounts of tread. The 17" D3 allows I bought with BFG AT KO2s on measure 31.25" overal diameter. That's quite a difference, and I really don't want to cause any issues with my Disco, nor do I want the speedo knocked out (I know all vehicles speedos are "out" to some extent).

I now have three choices:

1. Buy BFG ATKO2s for my 18" rims.
2. Fit the 17" D3 alloys and see if they work
3. Buy 16" alloys and buy some BFGATKO2s for those.

After reading for hours and hours (LZ and elsewhere) it seems that most people think the 16" wheels perform best, in particular 255/65/16 (which gives an exact match for overall diameter of the 18" wheels I have on now). I therefore tempted to go for that.

My Disco does handle nice round bends, but the steering is very heavy which could be a power steering issue, but I suspect not as it's not terrible, just a bit heavy and has a tendency to wander towards the ditch occasionally! I know that's probably the worn tyres (legal, but nearly illegal). I would like a slightly softer ride, hopefully without sacrificing too much road holding ability. I don't mind giving up a bit, but I don't want it to feel like a boat. On the other hand I do look forward to a bit of a softer ride as this feels quite harsh and where i live the roads are **** (that proves I live somewhere in the UK!) and I woiuld like to go off the beaten track a LITTLE. NOt a lot, mostly road driving, but I wouldn't feel comfortabl even down a bumpy lane with these 18" tyres on. It just feels too hard on the vehicle.

So maybe anyone with experience in these matters could offer some votes or thoughts. Would 16" be the way to go, or would that become too wallowy and boaty on the road? Would the 17" fit for definite without rubbing the arches etc? Or maybe the 18" could stay, but add a bit of profile, so instead of ordering AT tyres in 255/55/18, I could (maybe?) go for 255/60 or 65 profile for a bit more cushioning. I am totally stuck, and need to decide in the next day or two really. So any input would be appreciated. Thanks all.

Option number 3

Sierraferry advises that an oversized tyre messes up the fuelling and causes high exhaust gas temps. Its sound advice as gearing is stuffed beyond a 235/70/16 anyway. Those 31.5” tyres are big and will require a remap to get going. Not ideal. They looked nice tho : )
I recommend 16s with either 235/70 or 245/70 tyres on. Handles great on 16s for me ( with ACE). BFG ko2 are nice.

Thanks both of you. Just one point...

ronsealdeath said:

I recommend 16s with either 235/70 or 245/70 tyres on.

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Everything I have read suggested 255/65/16 tyres being "best" or at least most standard. Maybe that's not the case. But When i used that comparison checker (http://www.discovery2.co.uk/tyresize.html) and enter the tyres on my D2 (255/55/18), it shows that I need 255/65 to keep the rolling circumference the same. Which makes me wonder, are the wheels/tyres on my disco actually correct, closest to stock?! Maybe not, I am now curious about that.

ACE - Just looked that up as I didn't know about it. Mine being an 04, looks like I probably have that.

Can I just ask, since I was fairly decided on 255/65/16, can you tell me what differences I would notice with your suggestions of 235/70 and 245/70 please?

Dammit! I just double checked what I said above, and I am wrong. I always think about the "profile" figure (55/65/70) as a measurement, but it's not is it, it's an aspect ratio (as my friend explained to me a while back!) So I stand corrected (there's a novel occurrance!)

255/65/16 is pretty much identical to current rolling circumference on 255/55/18. But SO is your suggestion of 235/70 (bit smaller) and 245/70 (bit bigger) - both basically the same circumference. Hmm, so it does look like I have a few options for 16" wheels. I wonder what the most popular choice is, especially for 80% road driving with a bit of field work, shooting, farm tracks etc. 235 seems a bit of a jump and a fair bit less rubber on road (and my disco sticks to the road quite nicely now), but 245 seems a nice compromise. I think I read that less rubber on road also means slight mpg improvement. I am going to assume I won't notice that as it's probably a tiny theoretical difference, but i would rather go in that direction than wider I think.

Anyway, all great stuff, I am learning. Thanks agian.

255/55/18 is a standard 29" wheel size for a D2. I have KO2s in that size on my ES and they are excellent on road and OK for gentle off roading/green laning. Unless you are planning to lift your D2 I would not go any bigger. You will get a slightly softer ride with the higher profile of a 16" wheel, but the main limitation of the 18" hub over the 16" is that the lower profile does not allow you to reduce tyre pressures for soft surfaces. 255/55/18s are also a bit too small for overlanding and tyre pressure flexibility would be a real issue, so I have bought a set of 16" alloys and my plan is to wait until the current tyres are worn out (so at the rate KO2s wear I have plenty of time to put the cash aside) and then consider a 2" lift, HD bumpers and 265/75/16 or 235/85/16 Toyo Open Country for overlanding and put 265/65/18 KO2s on the 18" hubs for road/occasional off road use. Note the point on increased power requirements though a remap and an EGT gauge are sensible choices.

Si Click said:

255/55/18 is a standard 29" wheel size for a D2. I have KO2s in that size on my ES and they are excellent on road and OK for gentle off roading/green laning. Unless you are planning to lift your D2 I would not go any bigger. You will get a slightly softer ride with the higher profile of a 16" wheel, but the main limitation of the 18" hub over the 16" is that the lower profile does not allow you to reduce tyre pressures for soft surfaces. 255/55/18s are also a bit too small for overlanding and tyre pressure flexibility would be a real issue, so I have bought a set of 16" alloys and my plan is to wait until the current tyres are worn out (so at the rate KO2s wear I have plenty of time to put the cash aside) and then consider a 2" lift, HD bumpers and 265/75/16 or 235/85/16 Toyo Open Country for overlanding and put 265/65/18 KO2s on the 18" hubs for road/occasional off road use. Note the point on increased power requirements though a remap and an EGT gauge are sensible choices.

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Agree totally with all that, but would still encourage you, even with ACE to consider your shocks.

Si Click said:

...265/75/16 or 235/85/16 Toyo Open Country for overlanding and put 265/65/18 KO2s on the 18" hubs for road/occasional off road use. Note the point on increased power requirements though a remap and an EGT gauge are sensible choices

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I'd say that for those tyres remap and EGT gauge are both compulsory cos it's almost 9% difference

I have had a remap, but I don't want to go oversized. EGT - i think that means exhaust gas temp? Not learned about that yet but I have decided to sell these wheels and get a set of 16" wheels, then fit BFG AT KO2s, and have done with it.

So the only two decisions left are whether to go for:

1. 235, 245, or 255 width

2. 65 or 70 profile.

If i can't decide I will probably plump for 245 70 - seems a reasonable compromise if I don't know what the difference will be between them. my guts say go for 255, more width 'must' be better, but I know these asssumptions can often be a mistake!

More width = more grip = harder ride
So the opposite is true too.

john snoo said:

If i can't decide I will probably plump for 245 70 - seems a reasonable compromise if I don't know what the difference will be between them. my guts say go for 255, more width 'must' be better, but I know these asssumptions can often be a mistake!

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My advice is to go for 245/70/16 and you'll be OK, 255/70/16 doesnt mean just more width but bigger circumference and weight too, a power remap which was not dedicated for bigger tyres will keep good throttle response but the EGT will still rise.

Stanleysteamer said:

More width = more grip = harder ride
So the opposite is true too.

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I didn't know grip would affect firmness of the ride. interesting thanks.

sierrafery said:

My advice is to go for 245/70/16 and you'll be OK, 255/70/16 doesnt mean just more width but bigger circumference and weight too, a power remap which was not dedicated for bigger tyres will keep good throttle response but the EGT will still rise.

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Thanks. I have a friend with a set of 16" wheels, so I can get 245/70/16 on those. A friend of mine says I should go for 235/70/16. Can't really understand why, he does like a comfy ride though!

john snoo said:

A friend of mine says I should go for 235/70/16. Can't really understand why, he does like a comfy ride though!

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That's he standard dimension beside the 255/65/16 and the best choices, i recommended you the 245/70 seing that you are thinking to 255/70 already.

john snoo said:

I didn't know grip would affect firmness of the ride. interesting thanks.



Thanks. I have a friend with a set of 16" wheels, so I can get 245/70/16 on those. A friend of mine says I should go for 235/70/16. Can't really understand why, he does like a comfy ride though!

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It is not the more grip that gives the harder ride it is the low profile, more metal less rubber in the diameter of the wheel means less flex which gives the harder ride. Maybe my comment was too simplistic. Imagine for a minute a wheel that is 16" metal diameter and 1" rubber, there would be nearly no material to flex, so hard as rock.
Now imagine a wheel with 1" of metal at the centre and rubber over the 16", that would flex like mad, which would be more comfortable, wouldn't it?
Neither of these wheels could be used, well the first could just about be used for slowish speeds. In the beginning some lorries ran on solid tyres, i,e, no flexibility hardly at all.
But by exagerating the characteristics, I hope you now get why a low profile tyre gives less comfort.
By the way, the only reason a tyre keeps a car on the road is due to a thing called "slip angle" This is where, when you turn the wheel, the centre of the wheel moves around its vertical axis and the tyre running surface, where it touches the road, doesn't turn immediately, by the same amount. The difference between theses two angles is called slip angle. See this.https://www.f1technical.net/forum/viewtopic.php?t=6496
Don't know if this clarifies things for you or makes them more confused!
Basically if you snatch a wheel to a new angle the tyre will slip, i.e. lose grip and the vehicle will skid, whcih is why you should "feed" a car into a bend not try to wrench it round. Up to it's limit of traction, a low profile tyre holds the road very well, but it loses grip less progressively, i.e. faster than higher profile tyres, as less rubber prevents larger slip angles. So you will find your self in a skid faster with low profiles if you do not know their limits.

Thanks. Yes your comment confused me a bit as you seemed to be saying wider surface contact gives harder ride. I understand why the lower profile is the cause of "hardness" in the ride, and why the reverse is true.
Interesting stuff re slip angle.
Would the vehicle feel noticeably different to drive between 235/70 and 245/70? I am thinking theoretically extra grip/contact but probably not noticeable, wheres the extra 0.5-1 MPG might be noticeable with fuel prices the way they are

Not much, if at all.

thanks. Yes thats what I thought, but the extra sidewall may be noticeable off road. So it sounds like very little loss to road performance by going from 255/55 to 235/70, but a huge difference off road, and gentler ride. Sounds like a plan!

Ok, i think I have some 16" wheels lined up. They have 235/70/16 tyres on so they must be the right width (7J).
Looks like they are significantly cheaper in 16" than 18", this seems a good price https://www.camskill.co.uk/m64b0s22...Eff_:_F_Wet_Grip:_B_NoiseClass:_2_Noise:_74dB

If anyone knows a way to beat that price, hit me

thanks. progress at last!

PS, now's the time to be sure about 235 or 245. Now that I realise the "profile" is actually an aspect ratio, I think the 245 will mean slightly bigger sidewall. The price is pretty much the same. And with advice being never to go down in size, only up (a small amount), I am thinking of maybe going for 245 after all. I wonder if the change from 255/55/18 to 235 width might be more noticeable (road grip wise) than going instead for 245 width. Any votes would be appreciated, especially from anyone who has used both (if there is any difference noticeable on the road).
245 seems the theoretical better choice according to the 'rules' on overall diameter:




(That's if I am right in thinking 245 is even an option on 7J wheels)

john snoo said:

Now that I realise the "profile" is actually an aspect ratio,

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Thort you'd already got that!
So 245/75 means the tyre is 245mm wide and the sidewall height is 75 % of that.
And so on.
but the word "wide" is a measurement made where? That is the question!
This one says "section width"
https://www.bridgestonetyres.co.nz/how-to-read-your-tyre-size
This one says "the width of the tyre" which is really stupid as that changes when you inflate it!
https://www.protyre.co.uk/car-help-advice/how-to/find-out-your-tyre-size
and others say "tread width" but as we know some of the tread doesn't touch the road under normal circumstances.
And as this explains
https://www.tyresizecalculator.com/charts/tire-width-for-a-wheel-rim-size-chart
You can of course have wheels of different widths and then you need to ensure you have the right tyes for these widths. This is a question that has yet to be asked on this thread, but it too affects handling greatly.

john snoo said:

Ok, i think I have some 16" wheels lined up. They have 235/70/16 tyres on so they must be the right width (7J).
Looks like they are significantly cheaper in 16" than 18", this seems a good price https://www.camskill.co.uk/m64b0s229p135310/BF_Goodrich_Tyres_SUV_4x4_BF_Goodrich_ATKO2_All_Terrain_TA_BF_Goodrich_AT_KO2_-_235_70_R16_LT_104_101S_RWL_TL_Fuel_Eff_:_F_Wet_Grip:_B_NoiseClass:_2_Noise:_74dB

If anyone knows a way to beat that price, hit me

thanks. progress at last!

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That is a pretty good price, I paid more for one the other day, i think, without going out to check the actual size but it is a standard tyre for the rim. But that price was fitted and balanced. If you are just buying the tyre, that will need to be factored in. Unless you can fit and balance them yourself, or have a m8 who'll do it for you.
anyway, good progress!