Largest tyre sizes on a standard ratio driveline?

[twr7cx]

What is the largest tyre size that anyone has run on the standard ratio driveline of their D2?

I am currently running 255/70R18 which are 32.05" or 814.07mm. Personally, I prefer the vehicle like this. The revs are lower on the highway (and the torque converter still locks up at highway speeds), and with the VNT and exhaust modifications it is still fast enough without any negative effects on the fuel economy.

[gavinwibrow]

Don't you also have a 2" lift?

[twr7cx]

Don't you also have a 2" lift?

3". I have a 2" suspension spring lift and 1" suspension spacer lift based on the Les Richmond White Tiger kit.

But my question for this thread does not relate to rubbing. It relates to the vehicles driveline ratio/gearing. The larger the tyre, the more it slows the vehicle down, meaning you have to work the engine harder to move and probably also stresses the driveline more. I'm curious as to how far others have gone while retaining the standard driveline ratios.

[walker]

On my last D2 I ran 32" everyday but then ran 34" simex's offroad. Standard axles but with ARB lockers. The 34's were ok, but it did mess up the auto gearing.

This time round I am running 33" as everyday tyre but with 4.12 ratio diffs.

[twr7cx]

This time round I am running 33" as everyday tyre but with 4.12 ratio diffs.

What do you think 33" would be like every day? I am looking at fitting some 285/75R16 which are around there. Considering I have been running and am used to 32", I'm hoping the further 1" increase may not be too bad?

[bob10]

Been doing a bit of research into this topic, as I will be buying new tyres in about 18 months. The advice given to me was, from tyre dealers almost to a man, was, if you are travelling in remote areas, the most common sizes are - 265x 70, 245 x 70 [ because most Toyotas & nissans run those sizes]almost any other size , if you have a problem in a remote area, cold see you waiting for delivery, at a very high price. According to them. Bob

[walker]

They are running 265/70 but on a 17" rim

The 285/75-16 is a very very common tyre out there. I would not run that size without altering the diff ratio's. The Disco will handle it but fuel economy goes up and performance goes down. The auto tends to hunt as well

[Slunnie]

What do you think 33" would be like every day? I am looking at fitting some 285/75R16 which are around there. Considering I have been running and am used to 32", I'm hoping the further 1" increase may not be too bad?

I ran like that for quite a while. It's fine with the TD5 auto at least. Used a bit more around town and a bit less on the hwy, but fuel economy was inconsistent.

[walker]

I ran like that for quite a while. It's fine with the TD5 auto at least. Used a bit more around town and a bit less on the hwy, but fuel economy was inconsistent.

I knew you would be on here contradicting me Slunman!:p

We have always had different ideas about what size tyres run nicely. But that could be to do with the difference between TD5 and V8. I just think 33's are too much for the V8 on stock diffs.

[brenno]

I'm running 33" (285/75R16) BFG KM2's on standard gearing.

Probably a little sluggish off the line, but I don't race it. ;)

Let's face it, it's still quicker than a TD5 :wasntme:

I'll go to 4.12's (or 4.37's if I go to 35's) one day.

[Slunnie]

I knew you would be on here contradicting me Slunman!:p

We have always had different ideas about what size tyres run nicely. But that could be to do with the difference between TD5 and V8. I just think 33's are too much for the V8 on stock diffs.
Have we always disagreed on tyres? Thats not to say that we are not both right though.... or both wrong. :lol2:

I added TD5 auto thinking that you were running the V8 and that there are some pretty big differences. Actually, I suspect the thing that will make the biggest difference from what I've seen is the gearbox, with the manuals really not responding well to big tyres when offroading and in that gnarly low range stuff. I do hear what you're saying about the difference between TD5 and V8 also, and they can be so very different. I recall towing with a Pajero V6 and the TD with the differences being quite stark in the way power was delivered and how the autos responded.

[Thingy]

How noticeable is the taller gearing when running 235 85 16 or 265 75 16 in low range when going down hill with a standard ratio ?

[jafir]

How noticeable is the taller gearing when running 235 85 16 or 265 75 16 in low range when going down hill with a standard ratio ?

Those are stock size tires on a defender, and the defender has the same low range transfer case and axle ratios, so I'd bet it will do just fine on low.

[twr7cx]

Cheers all. I think I will give the 285/75R16's a go. Being on 32.05" already, it's not a huge increase. And with the automatic TD5 it seems less effected by the larger tyres. I also have the VNT fitted, ECU remap, Ashcroft HD torque converter, etc which should help. My vehicle gets 450km to a tank regardless of tyre size, weight carrying or towing, so I doubt it will effect my fuel economy.

[walker]

Those are stock size tires on a defender, and the defender has the same low range transfer case and axle ratios, so I'd bet it will do just fine on low.

I thought the Defender had lower gearing in the transfer case or is that only in high range?

[Landover]

I thought the Defender had lower gearing in the transfer case or is that only in high range?

Only in High Range.

[walker]

Cheers all. I think I will give the 285/75R16's a go. Being on 32.05" already, it's not a huge increase. And with the automatic TD5 it seems less effected by the larger tyres. I also have the VNT fitted, ECU remap, Ashcroft HD torque converter, etc which should help. My vehicle gets 450km to a tank regardless of tyre size, weight carrying or towing, so I doubt it will effect my fuel economy.

Another thing to think about is offset when running 285's. I am not sure how they will go on standard rims. I plan to put mine on Zu rims which should give me enough room between inside of tyre and inside guard.

[twr7cx]

Another thing to think about is offset when running 285's. I am not sure how they will go on standard rims. I plan to put mine on Zu rims which should give me enough room between inside of tyre and inside guard.

Les Richmond Automotive has a set of 16" x 8" steel rims in black round style to supply me with. They are +30mm offset so should solve that issues. I have a 3" suspension lift and the 32" don't rub, so hopefully the extra 1" should be fine too.
Once fitted I will assess if I need larger flares...

[AndrewGJones]

The larger the tyre, the more it slows the vehicle down, meaning you have to work the engine harder to move and probably also stresses the driveline more.



First bit is wrong, the last bit is right. Larger tyres speeds you up for any given revs, but off the line you are working the clutch/ drive line harder to get moving.

larger tyres also increase the side pressure on the wheel bearings and wear them out faster and decrease the mechanical advantage of the axle. More adverse torque is presented coming back from obstacles/bumps in other words.

Or in other other words, you need a stronger axle.

same principle as using a breaker bar onto a recalcitrant bolt; the longer the bar gets the easier it is. In this example the axle is the bolt, and the tyre the breaker bar and the rock is, well, you!

I was tempted to increase tyre size to get road speed up on the freeway, but decided it's probably better to get a roamerdrive instead to preserve the off-road ratios.

[brenno]

Another thing to think about is offset when running 285's. I am not sure how they will go on standard rims.

Got mine on standard alloys... No issues. Having said that, I don't know what the previous owner has had done to it (if anything) to prevent issues. I don't have rubbing at all though.

Given the choice, personally I'd go to +6 offset steelies, for nothing other than a wider tread and increased stability to somewhat negate the lift.

[twr7cx]

Given the choice, personally I'd go to +6 offset steelies, for nothing other than a wider tread and increased stability to somewhat negate the lift.

+6mm will push them out by 51mm each side which is beyond the largest increase allowed. I'm going to stick with the +30mm. On 32" tyres, I can still run the standard steeing stops and not have any reduced steering, so shouldn't need to go wider.

[twr7cx]

First bit is wrong, the last bit is right. Larger tyres speeds you up for any given revs, but off the line you are working the clutch/ drive line harder to get moving.

Yes, speed was the incorrect term used by me, I should have said reduced acceleration. I was attempting to make reference to the effect felt by the driver due to the larger tyres - the vehicle feels slower as the acceleration is reduced and the engine has to be worked harder to get up to the speed.

[brenno]

+6mm will push them out by 51mm each side which is beyond the largest increase allowed.

I take it you're talking legal increase??

Sorry, I don't understand your argument, unless Tassie has far different rules on this.

Going to 33's is beyond the largest increase allowed too isn't it??

My point is, if either option (larger tyres or wheel track) is going beyond legal increase, then both being beyond legal increase is the same thing. If you're looking to keep it legal, then the point of going to 33's becomes invalid anyway.

[twr7cx]

I take it you're talking legal increase??

Sorry, I don't understand your argument, unless Tassie has far different rules on this.

Going to 33's is beyond the largest increase allowed too isn't it??

My point is, if either option (larger tyres or wheel track) is going beyond legal increase, then both being beyond legal increase is the same thing. If you're looking to keep it legal, then the point of going to 33's becomes invalid anyway.

Yes, 33" will require an engineer approval and speaking to them (as I've detailed in other threads), because of some similarities between the Defender and Discovery 2 axel and the Defender being able to run up to 33.7" without engineer certificate, they are willing to proceed with approval.

As for increasing the offset further they were not willing to consider it.

[brenno]

Yes, 33" will require an engineer approval and speaking to them (as I've detailed in other threads), because of some similarities between the Defender and Discovery 2 axel and the Defender being able to run up to 33.7" without engineer certificate, they are willing to proceed with approval.

As for increasing the offset further they were not willing to consider it.

Ah ok... I wasn't aware you were getting it engineered.

Good luck with it then. As I said, I'm running 33's with 2 inch lift on standard offset alloys, and have no rubbing or scrubbing. ;)

[walker]

That's good to know Brenno, I was a bit worried about rubbing with the 285's. I'm only running a 2" lift at the moment but that should be irrelevent as the compressed height will be the same as yours unless you have extended bump stops.
My Zu rims arrived today (well 3 out of 5 arrived, hoping the rest turn up tomorrow) can't wait to get the 33's fitted.

[Landover]

I was looking at going up to 285 75 16 or 255 85 16 from 32's,for off roading. Has anyone used 33's with a standard ratio D2 TD5 Manual. I want to know if it's to much for the manuals drivability

[Slunnie]

I was looking at going up to 285 75 16 or 255 85 16 from 32's,for off roading. Has anyone used 33's with a standard ratio D2 TD5 Manual. I want to know if it's to much for the manuals drivability

Not having a manual, but having done a lot of difficult driving with many that do have manuals, they are all good drivers but the manuals really don't do crawling or slow controlled work very well and the reduction in gearing makes this pretty untidy at times,especially when you are at that point where you really want things to be going well. My opinion is that in a manual, if you're putting larger tyres on, and you do difficult technical 4wding, ie not just tracks, then you really need to look at 30% transfer gears at least.

[walker]

Why not just change the diff ratios?

[twr7cx]

I'm running 33's with 2 inch lift on standard offset alloys, and have no rubbing or scrubbing. ;)

It's the standard offset that allows you to not have the rubbing. With pushing the wheels out you are putting them closer to where the guard metal comes down and this is what it fouls on. Hopefully my extra inch of lift is enough to compensate for this. I want the offset to widen the track for looks, handling and stability, and to retain good turning circle.

[walker]

Not sure if that thinking is correct.

Firstly it is the inside of the tyre that rubs on the inside of the wheel arch, especially when on lock.

Second, a lift won't make any difference to rubbing. Although it does sit further away from the guard at rest, when articulating offroad, the wheel on a 2" lift will compress just as far as a wheel on a 3" lift unless extended bumpstops are used.

What tends to happen is that many off the shelf springs just used harder springs to gain the lift so the wheel doesn't compress as much. This will cause less/no rubbing but you have lost articulation and wheel travel.
At the moment I think I am at about a 2.5" lift but I have custom springs which are 170lb on front and 270lb on the rear.

[twr7cx]

Firstly it is the inside of the tyre that rubs on the inside of the wheel arch, especially when on lock.

I have found that with 32" and 33" tyres I do not have any inside rubbing when I use +30mm offset rims or 30mm wheel spacers. If I use standard offset wheels they rub on the front control arms.


Second, a lift won't make any difference to rubbing. Although it does sit further away from the guard at rest, when articulating offroad, the wheel on a 2" lift will compress just as far as a wheel on a 3" lift unless extended bumpstops are used.

As you point out, extended bump stops need to be used. I have a 3" lift, on the front my bump stops are extended by 30mm (have used orange urethane bump stops) and on the rear my bump stops are extended by 50mm (using Les Richmond Automotive White Tiger spacers). This is to avoid over compressing my Bilstein +2" shock absorbers (which are spaced up by 2" using Les Richmond Automotives White Tiger spacers).

Because of this, I retain the added benefits of the +2" lift, but avoid the rubbing.


When I had 255/70R18 which are around 32", they first rubbed on the inside on the control arms for the front differential - so I fitted 30mm spacers to solve this, they then rubbed on the outside of the tyre up the top on the factory flares due to being pushed out closer to the flares - this was with a 2" lift. With a 3" lift I do not have this issue.