Wheel/Tyre options for D2 and legal/safety considerations

[Wil2k]

Hi all,

More brain picking - I've searched the forums and read some interesting discussions on tyres / wheels / pressure etc, but havent really answered my own questions yet. Hope you can enlighten me.

My 01 Disco 2 has currently got 255/55R18 (109H) tyres on the factory alloys I bought it with. What are your thoughts as an option for replacements. I do 80% surfaced roads and am hoping to do some more serious offroad, so I want to have tyres that aren't going to cripple me offroad.

Tyre shop up the road were showing me some Goodyears at $450 a pop. I've read on here that some people rate the Cooper ST pretty highly although dont think it comes in an 18..

I've got the big wheels, so that limits my options a lot. Should I look at 16" rims?

What are the considerations regarding safety and legality if I change my alloys to something smaller? (Speedo, load, handling etc)

Should I pick up a second hand set of steel rims for some offroad tyres perhaps? It would till have to be street legal and safe tho..

I don't have much $$ to blow on this so want to spend wisely and safely :)

Cheers

Wil :D

[Basil135]

The main legal consideration is rolling diameter.

So, if you put 16" rims on, the sidewall of the tyre will be bigger to give you the same overall rolling diameter as the original.

Now that said, there is a small amount of leeway allowed within the specs, and any good tyre retailer will be able to help you with that.

For what it is worth, I had the 18" rims, sold them & bought 16" due to the fact that the tyre choice is much much greater.

If you can afford it, buy some second hand 16" rims for when you go bush, and keep the dress rims for looking good.

[Rosscoe68]

and for my 2c, don't get coopers
sidewalls are ..............

[Wil2k]

Cool. Thanks for the input.

I actually dug out my D2 manual .. :o .. and looked up the recommended tires..

It states :


7J x 16 - use with 235/70 R16 Goodyear Wrangler HP 105 H
or with 235/70 R16 Michelin XPC 105H
8J x 16 - use with 255/65 R16 Goodyear Wrangler HP 109 H
or with 255/65 R16 Michelin XPC 109H

I have deduced that the 7J is narrower that the 8J (which I have now I guess) - and pros / cons to the skinny wheels?

Did i read somewhere here that the XPCs are no longer available?

Changing rims will open up a whole world of tyre options by the looks of it, so I reckon I'll go that path.. will probably be cheaper in the long run too.

Cheers

Wil

[Rosscoe68]

7J is 7" wide. 8J is 8" wide
why they run imperial diameter with metric width and profiles i still don't understand.
in my opinion the 7" rim is a better looking rim than the 8" in 16" for the D2. unless you want to go stupid width, i.e 285/85 , then the 7J will be fine.

yes, the XPC are gooooorn.

[Hendrik]

You can't go wrong with two sets. You will get a lot more out of your play tyres that way, and it leaves you the option of going with an agressive tread like a BFG KM2, MTZ etc as you dont drive everyday with that tyre. Do you have a lift on yours? You can run up to a 285/75, but most people run the 265/65 which is readily available and isn't that big so the cops should care too much. Yes they are an illegal size, but running them only on trips reduces the risk. It still isn't perfect, but in QLD there is just no other way.

Bigger tyres will throw your speedo out, by about 10% if you run 265's. The car will also lag a bit more as the engine has to work harder due to the larger tyres overgearing the vehicle.

[brownrangie]

I currently run BFG AT 255/70 R16 which gives a bit more height (within the law) under the diff over the 235/70. They are a good tyre for the on/off road combination (not extreme muddy stuff) and saves you running 2 sets of tyres.

For the 18 inchers my father runs General Grabber AT2 on his 03 RR and has taken it through the Vic high country and Tassie without any dramas. Just another option to get a bit more agressive over the Goodyears without changing rims. The downside is the lower profile of course.

[stevo68]

Yo Will....I get to respond to one of your posts :D. I would flick the idea of 2 sets of wheels....unless you are looking at running massive muddies off road. Also for better tyre options...would get rid of the 18's and get 16's. As you know I run Maxxis Bighorns....which in a recent 4WD Action tyre comparo of HT's, ATR's and MT's it was determined that the Bighorns and KM2's were the winners in terms of being an all round tyre.

With 18's there is always going to be a profile issue at some point when airing down and going over rocks....even rocks that arent that "extreme". I went through this whole scenario 12 odd mths back...same thing...run road tyres and a 2nd set for off road. Bloody hell....that was from people with out a horde of kids.....or much younger...who could be stuffed. Then there was the old day to day tyre issue. Now as you know I would do well over 500kms a week ++ so would say 80% of my time is on road.....20% off. With the Bighorns I have found them a very reasonable on road tyre and off road they are as tough as hell in all terrains. In 12 mths I have done over 12 off road trips and clocked up over 30,000kms....no issues with them at all.

With the way MT's are these days...especially the Bighorns, KM2's. Mickey Thompsons etc...I reckon if you are serious about doing even a bit of medium to hard off roading...an ATR shouldnt even get a look in....not when there are better MT's which are just as good on road. I can bring the copy of the mag over when I pick up kids on Friday,

Regards

Stevo

[harlie]

What are the considerations regarding safety and legality if I change my alloys to something smaller? (Speedo, load, handling etc)



At the risk of becoming unpopular (legal statements are generally not received well here – but you asked). To remain legal - “The rim diameter may be varied from the standard size but the overall diameter of the tyre must not vary by more than +15mm or -26mm.” (end quote). QLD Transport rules (http://www.transport.qld.gov.au/resources/file/ebde8d0521b67c6/Pdf_modification_motor_vehicles2.pdf)

The last time I used (one of the many) a tyre calculator the largest 16’’ tyre that is legal on a D2 is a 245/70. I also know the insurance companies are now checking these in the event of a good accident.

There is also legislation around speedo accuracy. Basically the speedo must be within 10% but CANNOT read slower than the actual vehicle speed

[beanie_205]

I would flick the idea of 2 sets of wheels....unless you are looking at running massive muddies off road. Also for better tyre options...would get rid of the 18's and get 16's.

I reckon Stevo has nailed it. 18's are just not that suitable for off road work anyway- they will ride rougher, be more fragile (tyres & rims) and if you ever venture anywhere remote and need new tyres you'll be waiting for a while.

I went through this a few months back when I first got my D2, I ended up with a set of BFG Km 2 mud terrains, and they've been great. They are very quiet (The recent mag article stevo talked about has them as the second quietest tyre as tested against other a/t's, muddies AND highway terrains) and so far off road have been fantastic. I went with stock 235/70/16, basically because with new laws they were biggest legal tyre available without the engineering hoo hah- as my daily driver it has to be legal. You might now be able to get 245/70/16 which would also be legal.

last thing- these tyres are great on economy (for a muddie), my around town figures went from 10.7 litres/100km on H/ts to 11.2/100 km. Not bad at all. You could cover the cost of buying 16 rims by selling the 18s.

[Tombie]

18's are just not that suitable for off road work anyway- they will ride rougher, be more fragile (tyres & rims) and if you ever venture anywhere remote and need new tyres you'll be waiting for a while.

What :eek:

The rims and tyres are no less capable, and are easily as strong.
18" tyres are common in a lot of out the way places now.

Only reason to change is $$$ value or tyre selection.

[wanglemoose]

18 inch tyres dont hang onto the top of ruts like 16s (only because there isn't enough sidewall to let them down) damn thing cost me a carton, it was sitting on the diffs with the wheels off the ground. luckily no damage from being skull dragged out.

[ozscott]

Yep...its not that hard...the smaller the rim and the higher the sidewall the better off road...so yes 16's are more off road capable than 18's whether holes or sand - its just not seriously debatable.

Cheers

[CJT]

Check your tyre placard instead of your manual. The trye placard on my D2 V8 has four different tyre sizes compared to the three listed in the manual.

I have;

215/75/R16 on 16x7J = 728.9mm
235/70/R16 on 16x7J = 735.4mm
255/65/R16 on 16x8J = 737.9mm
255/55/R18 on 18x8J = 737.7mm

As stated previously in QLD you can only legally go +15mm over the largest standard tyres size, so largest diameter is 752.9mm.

You can also go up to 1.5 times wider than the standard widest option but not narrower than the lowest option (215 in my case).

So I am going for a 225/75/R16 in either the BF Goodrich MT (744mm) or Cooper STT (750mm) overall size according to supplier websites.

[StephenF10]

...
The last time I used (one of the many) a tyre calculator the largest 16’’ tyre that is legal on a D2 is a 245/70. I also know the insurance companies are now checking these in the event of a good accident.

There is also legislation around speedo accuracy. Basically the speedo must be within 10% but CANNOT read slower than the actual vehicle speed

That seems to rule out the 245/70's. With the 235/70 XPCs my speedo was spot on (as compared to two GPS units), but with 245/70 Goodyear Silent Armors the speedo now reads 2% slow.

Stephen.
'01 D2 TD5 Auto

[beanie_205]

What :eek:

The rims and tyres are no less capable, and are easily as strong.
18" tyres are common in a lot of out the way places now.

Only reason to change is $$$ value or tyre selection.

Fair enough Tombie they are probably as strong- and I've never heard of anyone breaking a 18 alloy rim so i stand corrected there:angel: and as for remote spots you may well be right there too it's a small world these days :angel:- but a 16 rim gives you two more inches of air and rubber between your rim and the corrugated/rocky etc surface you're driving on, so they would cushion impacts better and allow more flexibility with tyre pressures

[harlie]

That seems to rule out the 245/70's. With the 235/70 XPCs my speedo was spot on (as compared to two GPS units), but with 245/70 Goodyear Silent Armors the speedo now reads 2% slow.

Stephen.
'01 D2 TD5 Auto

That’s right, a point always overlooked. If your speedo is correct to start with (most read slightly over because this ADR has been law in the EU for a while) then you also need a speedo mod… My D2 speedo was always 2-3% over when compared to GPS...

However if you're in a big bingle the insurance co won't be looking at how accurate your instrumentation is - they will check the tyres (larger tyres affect braking - thats why the law is there)... Speedo accuracy is only going to be questioned when you say to the officer "I was only going 60 sir, my speedo says so"

[Tombie]

Fair enough Tombie they are probably as strong- and I've never heard of anyone breaking a 18 alloy rim so i stand corrected there:angel: and as for remote spots you may well be right there too it's a small world these days :angel:- but a 16 rim gives you two more inches of air and rubber between your rim and the corrugated/rocky etc surface you're driving on, so they would cushion impacts better and allow more flexibility with tyre pressures

Actually the difference is only 1 inch :)

Also, rim design is very different internally, meaning an 18" rim can have the same air volume as a 16" rim running the same O.D tyre.

Only difference is 1" less sidewall. And often the flex in a tyre is dictated by its construction, not its profile.

I've seen multitudes of tyres offroad and some wont bag out even at 10 psi where others at 18 psi are bulging like crazy.

Elongated tread length is far more capable than a bulging sidewall offroad as it provides area without the width causing drag.

Tread pattern, tyre construction and pressure all have much more effect offroad than profile.

Whilst a higher profile rim *may* provide a marginal amount of extra rubber in event of driving over a gibber and clipping the rim, the actual real world implications are rare and unlikely.

I've driven thousands of km's on 16's, 17's and 18's and noticed no performance degradation in any of them. Its all down to driving style, speed and as mentioned earlier pressure and construction.

[stevo68]

Actually the difference is only 1 inch :)

Also, rim design is very different internally, meaning an 18" rim can have the same air volume as a 16" rim running the same O.D tyre.

Only difference is 1" less sidewall. And often the flex in a tyre is dictated by its construction, not its profile.

I've seen multitudes of tyres offroad and some wont bag out even at 10 psi where others at 18 psi are bulging like crazy.

Elongated tread length is far more capable than a bulging sidewall offroad as it provides area without the width causing drag.

Tread pattern, tyre construction and pressure all have much more effect offroad than profile.

Whilst a higher profile rim *may* provide a marginal amount of extra rubber in event of driving over a gibber and clipping the rim, the actual real world implications are rare and unlikely.

I've driven thousands of km's on 16's, 17's and 18's and noticed no performance degradation in any of them. Its all down to driving style, speed and as mentioned earlier pressure and construction. All I know is that I went from 19's to 18's on my D3....and now 16's on my D2...give me the 16's over the 18's every day of the week. The options for 18's are still limited......though did see a nice pair of Bighorns in 265/70/17's on a D3...but 18's with allowable tyres.....my rims got hammered over rocky terrain due to bugger all side wall.

When I get another D3......I would only look at the diesel 2.7...for the 17inch rims. Even the KM2's in 18's whilst a much better option...I have seen then come off the rim where Smokey and the 16's sailed up. More rubber..more clearance...more options......with 16's....

Regards

Stevo

[optimax90]

That seems to rule out the 245/70's. With the 235/70 XPCs my speedo was spot on (as compared to two GPS units), but with 245/70 Goodyear Silent Armors the speedo now reads 2% slow.

Stephen.
'01 D2 TD5 Auto

after changing from 235,s to 245,s have you noticed a change in the gearing of the auto?

[Wil2k]

Thanks so much for everyone's input! It's been fantastic to hear what you all have to say about yer boots!

The recent posts about speedo accuracy also lean towards the topic of extra stress on gearbox / diff etc etc.

I noticed TJS-70Y posted some new pics of their D2 here.. http://www.aulro.com/afvb/discovery-2/80040-show-us-your-d2.html
and mentions having blown the rear diff (damn!) -- anyone care to comment? The fella at the tyre shop was adamant that larger OD means trouble.

Cheers

Wil.

[TJS-70Y]

G'day.
Just thought I would let you know that the rear diff blew in my D2 as a result of not having a CDL for most of its life. Without it all the weight of the vehicle is put on to the rear diff offroad whilst most of the drive is sent to the front diff.
What happened in mine is that the centre pin in the diff had come adrift. It then had enough force to break free of its containment in the centre. This destroyed a side gear in the process. I have a CDl now fitted and I believe that now with it locked there was equal force distributed front to rear. Ie 50/50. Before it would have been more like 80/20 front to rear. It's hard to say if the tyres caused this as the ground wasn't very slippery. I would blame the cross pin not being secured more than the tyres. The front diff has the same problem, the cross pin is not secured and there is a good chance it would have let go soon too.
I am led to believe that a lot of people that retrofit the CDL into their D2's end up blowing a rear diff. Not all just a few.

Hope that helps.

Thomas

[Tombie]

<snip>Wil.



yes! Contact me if interested.

[preeds]

Hi All
I am new and was told by my tyre supplier (have known him for years so trust him) to ask on a forum if the following option will work for me to upgrade my tyres. Firstly I have a 2002 model TD5 series 2 that currently has 18 inch rims which have limited my tyre choices. I have coopers HT's on at the moment and they just aren't cutting the mustard off road. I have raised my vehilce by fitting Bilstien shocks and King springs to give it about 2 inches lift. I have recently been given the original steel rims (16x7J) from my vehicle (bought my disco from a mate).

The Question........... Can I fit Coopers LT245/75 R16 STT's to my disco? if so will it effect the performance (especially when towing) or what other suggestions do you have. He has also suggested as a fall back 255/70 R 16 ST Coopers as a fall back. I would prefer the STT's as am planning on doing some serious campingin the future (Cape York, Gibb River etc)

thanks in anticipation of someone being able to help
Preeds

[Fluids]

Preeds. Be careful of the 255/70 R 16 S/T Cooper ... THAT particular tyre is NOT an LT construction ... it's passenger construction. I know, I have them fitted to my D2a ... about to fit 2x new ones today ... (previous owner never did a wheel alignment & 1x has scrubbed out) ... they've done 70k so far and still have an easy 20-30k left in them. Grip well, sand/beach work is OK, I have no complaints. (flame retardant suite ON) :) .... came with the vehicle and so far so good (about 14k since I've owned it).

The LT version of that tyre is 255/75 R16.

The std tyre for a D2 is 29" diameter (235/70*16 or 255/65*16 or 255/55*18). The 255/70 I'm running is 30" (3.5% increase) and the 24/75 is 30.5" (4.9% increase) ... I don't think that would be too much change in your final gearing ... folks here seem to be happy with 265/75 tyres ... that's 31.75" .... or about a 9% increase ... !

See *Alloy Wheel & Tyre Size Calculator (http://www.discovery2.co.uk/tyresize.html) for Mr UP's excellent tyre size calculator.

Kev..

[Tombie]

Hi All
I am new and was told by my tyre supplier (have known him for years so trust him) to ask on a forum if the following option will work for me to upgrade my tyres. Firstly I have a 2002 model TD5 series 2 that currently has 18 inch rims which have limited my tyre choices. I have coopers HT's on at the moment and they just aren't cutting the mustard off road. I have raised my vehilce by fitting Bilstien shocks and King springs to give it about 2 inches lift. I have recently been given the original steel rims (16x7J) from my vehicle (bought my disco from a mate).

The Question........... Can I fit Coopers LT245/75 R16 STT's to my disco? if so will it effect the performance (especially when towing) or what other suggestions do you have. He has also suggested as a fall back 255/70 R 16 ST Coopers as a fall back. I would prefer the STT's as am planning on doing some serious campingin the future (Cape York, Gibb River etc)

thanks in anticipation of someone being able to help
Preeds

They will fit and the vehicle will perform fine.

But they are crap tyres... Gibb River Road will tear them to shreds.

[preeds]

Preeds. Be careful of the 255/70 R 16 S/T Cooper ... THAT particular tyre is NOT an LT construction ... it's passenger construction. I know, I have them fitted to my D2a ... about to fit 2x new ones today ... (previous owner never did a wheel alignment & 1x has scrubbed out) ... they've done 70k so far and still have an easy 20-30k left in them. Grip well, sand/beach work is OK, I have no complaints. (flame retardant suite ON) :) .... came with the vehicle and so far so good (about 14k since I've owned it).

The LT version of that tyre is 255/75 R16.

The std tyre for a D2 is 29" diameter (235/70*16 or 255/65*16 or 255/55*18). The 255/70 I'm running is 30" (3.5% increase) and the 24/75 is 30.5" (4.9% increase) ... I don't think that would be too much change in your final gearing ... folks here seem to be happy with 265/75 tyres ... that's 31.75" .... or about a 9% increase ... !

See *Alloy Wheel & Tyre Size Calculator (http://www.discovery2.co.uk/tyresize.html) for Mr UP's excellent tyre size calculator.

Kev..
thanks Kev is all vey confusing as everyone appears to have an opinion about cetain tyres, I just want a decent off road tyre that I will put on whenever I am going camping
Preeds

[preeds]

They will fit and the vehicle will perform fine.

But they are crap tyres... Gibb River Road will tear them to shreds.

Thanks Tombie for your advice do you have any suggestions?
I am after a set of tyres that I can put on whenever I am going bush and will then put my 18inch alloys on for "in town" driving
cheers
Preeds

[bronson]

Ive got some 245/70/R16 cooper stt on my 99td5 disco and i reckon that they are great on gravel rd,sand, mud and they make little noise on the hiway.
Did notice though a slight speedo decrease, and a little less down low, not too much to worry about with a Ecu upgrade.

cheers bronson;)

[preeds]

Thanks Bronson
am currently on coopers site looking at tyres sizes that will fit my disco, they dont have a 245/70 listed in STT, the best I can find is a LT 255/70 16 STT with a diameter of 770mm. My current diameter is 736mm so will increse by 34mm. I have had an ECU upgrade also to my disco but was wondering about performance and also my insurance as they say on Coopers site that you are allowed to go up by 15mm (currently under review to 50mm it states also)

am also looking at the LT245/75 16 STT's with a diameter of 780mm

thanks for advice
Preeds:D

[CJT]

If you want legal tyres in QLD go for the Cooper STT in a 225/75/16. They are 750mm so within legal limits.

[Wil2k]

Tire size calculator (http://www.miata.net/garage/tirecalc.html)

This tyre calculator has more info, speedo change etc etc. :)

[Wil2k]

... pending getting some 16" x 7 rims..

Reckon I've decided on the BFG MT T/A KM2 (LT225/75/R16) - BFGoodrich Tires - Mud-Terrain T/A^KM2 (http://www.bfgoodrich.com.au/index.php?a=tires.off_road_suv&id=275)

Were they the other ones that rated well in magazine article? They'll be my every day drivers.

At 744mm OD they'll keep me within legals, speedo will be about 1.2% slow (close enough for me). They look pretty chunky too! :D

Cheers

Wil

[Wil2k]

yes! Contact me if interested.

PM sent.

Wil

[stevo68]

... pending getting some 16" x 7 rims..

Reckon I've decided on the BFG MT T/A KM2 (LT225/75/R16) - BFGoodrich Tires - Mud-Terrain T/A^KM2 (http://www.bfgoodrich.com.au/index.php?a=tires.off_road_suv&id=275)

Were they the other ones that rated well in magazine article? They'll be my every day drivers.

At 744mm OD they'll keep me within legals, speedo will be about 1.2% slow (close enough for me). They look pretty chunky too! :D

Cheers

Wil Nice work mate.....and yes they are the ones that rated well. In last 2 major tests...the KM2's and Bighorns came up trumps. Will have to see how you find them as maybe tempted to change....though in same size at 265/75 there is almost an 11-12mm diff. Won't look like a nana's car anymore :p

Regards

Stevo

[bronson]

Sorry mate 245/75/r16, sounds more like it, put em on , they're the bomb!!