D3 tyre size selection from 235/70r17 to...

[sinistr]

Hey guys,

The current tyres fitted to our D3 are coopers in the size 235/70r17 on LR 17 inch alloys.

During the last offroad trip, whilst the car performed well I did notice a couple of occasions where the front protection guard caught some of the taller centers of ruts and I can only out that down to the tyre profile.

I considered 18s but the overall diameter of the common sizes is the same if not smaller than the current Tyres.

In order to get better clearance, I need taller profile tyres - not 245/65 - I need 245/70 or 255/70 if I can to increase the overall diameter.
265/65r17s sound great for the overall width and would be taller but the fact they won't fit the spare wheel area turns me off those.

I did think 'Johnson rods' would be great BUT they won't make the diff sit any higher - period, so it's a bit if a waste.

Also thinking about BMW 17inch wheels as the offset is 42 compared to 50 odd on the standard wheels, can put a thicker tyre on there and the whole wheel will sit further out (increasing track width), again spare wheel compartment to think about there.

I've not seen many 255/65 or 255/70 tyres, 245/70 is popular on prados etc.

What are your thoughts guys?

Thanks in advance. Mike

[SBD4]

Mike, with Johnson Rods or better still GOE Rods or Llams you do get the additional clearance at the diffs.

[Graeme]

255/65 are the same OD and 245/70 and 265/65 are only slightly larger OD and fit the spare wheel recess but 265/65 may be a little wide for the LR 7" rims. I suggest changing to 245/70 for far more brand options rather than height increase but as already stated there are indeed options to raise the vehicle when required.

I use the X5 rims currently fitted with 245/70 but am considering changing to 265/65. The X5 rims really need special nuts with extended shanks to have enough threads because the common taper nut does not.

[gghaggis]

I'm not sure where you heard about the tyre not fitting the spare well? The larger 265/70R17 will fit (albeit deflated and with the fibreglass divider removed), so the 265/65R17 shouldn't be an issue.

There's a lot of choice in 265/70R17, which is probably as big as you'd want to go.

And a suspension lift (rods or LLAMS) will give you an overall increase in height - it's only with live axle setups that the clearance under the diffs doesn't change.

Maybe you should come to our seminar in February ?
:)

Cheers,

Gordon

[LeighW]

Hi Mike - I have had a lot of experience with both 245/70 and 255/65x17 tyres on the original 17 inch LR rim.

From my experience the 245/70 is about 3.5 mm taller (7 mm overall diameter larger) than the standard tyre size. It is also the tyre size that matched my speedo to the GPS reading as the standard size was always consistently lower. BTW, I run 38 psi both front and rear.

However the 255/65 is almost 20 mm wider but only about 0.6 mm taller on the 7 inch rim. Whilst the difference might seem small the tyre is almost too "baggy" for the 7 inch rim and when towing does not exhibit the same straight line stability as either the 235 or 245 section widths.

From my observations in your instance I believe the 265/65 would be far too baggy (except in the sand) and would be very susceptible to sidewall punctures more easily and be very floaty at speed due to the amount of sidewall flexibility. This might be overcome with increased pressures but I doubt it is a viable solution. Another point is that tyre manufacturers do NOT specify the size 265/65x17 for any rim less than 7.5 inches. To stay on the correct side of you insurer you might like to consider the last point.

Taller tyres are always going to place extra loads on your drive-train and throw your speedo readings out. I suggest looking at 18x8 inch wheels with a 265/65x18 tyre. This will give an extra 10 mm ride height and meets tyre manufacturers' rim recommendations. You just need to remember that at 100 km/h indicated on the speedo you would be doing about 103 km/h.

HTH

[sinistr]

thanks for the replies and advise guys - sorry about the delay - back at work this week and its been crazy to say the least.


Mike, with Johnson Rods or better still GOE Rods or Llams you do get the additional clearance at the diffs.

Thanks SBD4, do you know where I can get information on the lift of the diffs/cross members? I've looked on the next but everything just speaks of suspension lift using the airbag and settings - I thought the diff and unsprung components would stay at the standard level and the rods only give lift on the airbags?


255/65 are the same OD and 245/70 and 265/65 are only slightly larger OD and fit the spare wheel recess but 265/65 may be a little wide for the LR 7" rims. I suggest changing to 245/70 for far more brand options rather than height increase but as already stated there are indeed options to raise the vehicle when required.

I use the X5 rims currently fitted with 245/70 but am considering changing to 265/65. The X5 rims really need special nuts with extended shanks to have enough threads because the common taper nut does not.

Graeme - there's a set of BMW X5 rims locally for sale for under $100 (cheap) but only come as a set of 4 (why oh why). When you say special nuts you mean longer - as the X5 wheel offset is larger the actual recess would have to be deeper, perhaps its just for the convenience of the access plus the fact the LR nuts have these special hoods on them - i understand what you mean as I've used longer threaded nuts on my race car for the convenience factor.


I'm not sure where you heard about the tyre not fitting the spare well? The larger 265/70R17 will fit (albeit deflated and with the fibreglass divider removed), so the 265/65R17 shouldn't be an issue.

There's a lot of choice in 265/70R17, which is probably as big as you'd want to go.

And a suspension lift (rods or LLAMS) will give you an overall increase in height - it's only with live axle setups that the clearance under the diffs doesn't change.

Maybe you should come to our seminar in February ?
:)

Cheers,

Gordon

hi Gordon, I had a look at your site - i'll certainly try and make the seminar - sounds like theres particular way of setting these cars up and driving in comparison to the standard 4x4.

Regarding tyres - its the deflation part i'd rather steer clear off and have a tyre which fits without deflating/dismantling any of the stock parts.

again - i'd like to understand more about the rods and how they lift the axle part of the suspension?


Hi Mike - I have had a lot of experience with both 245/70 and 255/65x17 tyres on the original 17 inch LR rim.

From my experience the 245/70 is about 3.5 mm taller (7 mm overall diameter larger) than the standard tyre size. It is also the tyre size that matched my speedo to the GPS reading as the standard size was always consistently lower. BTW, I run 38 psi both front and rear.

However the 255/65 is almost 20 mm wider but only about 0.6 mm taller on the 7 inch rim. Whilst the difference might seem small the tyre is almost too "baggy" for the 7 inch rim and when towing does not exhibit the same straight line stability as either the 235 or 245 section widths.

From my observations in your instance I believe the 265/65 would be far too baggy (except in the sand) and would be very susceptible to sidewall punctures more easily and be very floaty at speed due to the amount of sidewall flexibility. This might be overcome with increased pressures but I doubt it is a viable solution. Another point is that tyre manufacturers do NOT specify the size 265/65x17 for any rim less than 7.5 inches. To stay on the correct side of you insurer you might like to consider the last point.

Taller tyres are always going to place extra loads on your drive-train and throw your speedo readings out. I suggest looking at 18x8 inch wheels with a 265/65x18 tyre. This will give an extra 10 mm ride height and meets tyre manufacturers' rim recommendations. You just need to remember that at 100 km/h indicated on the speedo you would be doing about 103 km/h.

HTH

thank you Leigh, I won't be towing anything excessively - small boat every now and then or a car trailer with a little light Honda on it, so nothing major - however sidewall strength is important.

the 235/70s OD is 760.8, 245/70 OD is 774.8 (14mm - 7 each sidewall), 255/65 OD is 763.3, 265.65 OD is 776.3 and 265/65/18 OD is 801.7 (biggest difference).

The current wheels do show 5km faster on the speedo than the GPS so I assume 245/70 will read a bit closer (1.8km difference) - and are a good fit on that rim. As you said 265/65 is designed for the 7.5 inch rim - shop won't even fit them for me on the 7 inch rim.

I might look into the 265/65/18s because the sidewall is tall and allows for decent deflation otherwise stick to 245/70/17 :)

thanks again for your thoughts everyone - need to read more about the suspension rods. :)

[Graeme]

Being independent suspension the diffs are attached to the chassis so raising the suspension also raises the diffs.

LR wheel studs are shorter than normally fitted to other vehicles using standard taper nuts because the LR nuts have a shank that goes most of the way through the rim. When X5 rims are fitted special nuts that also have shanks that go into the rim hole are required. There's a thread on here about the X5 rims and sourcing appropriate nuts.

[BobD]

Being independent suspension the diffs are attached to the chassis so raising the suspension also raises the diffs.



Because the diffs are attached to the body the front cross member is what usually touches the ground first, instead of the diffs, which touch the ground first on a live axle 4WD. This cross member gets closer to the ground when you hit a bump so you need to go slower than you would in a conventional live axle 4WD to minimise the suspension compression and hence keep the front cross member as high as possible.

The first time I drove my D4 off road at Bartons Mill I drove the D4 like I drive my Patrol and bashed the cross member really hard on the ground on ruts which the car could easily clear at slower speed. I quickly learnt that slower is good in a D4. Due to the traction control you rarely need momentum except in sand, where touching the centre of the track with the cross member doesn't matter much.

Go to Gordon's course and buy his book and all will be revealed.

Bob