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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
They are 8.5

If the Startech are 8.5” and the Modulars are 7” and I fit the same width tyre to each, 265, then the tread will sit ~20mm further out on the Modulars?

If I fitted 235 tyres to the Modulars they would sit 5mm further out?

I guess I have to go with a compromise unless I find something the same spec as the Startech.
Post #711167 6th Jun 2018 8:54pm
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
I can get wolf style wheels at ET20 but they are 6,5” I guess it wouldn’t be a problem fitting 265/75R16 to these, however, would the narrower width cause the tyre to bulge enough to effect its diameter making them incompatible If they were on the same axel as a Startech.
Post #711192 7th Jun 2018 6:50am
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
Posts: 11240

United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey
If you're planning to use to completely different sized wheels and tyres then you're chasing the wind if you just want them to look nice. It would be far better to just make sure that the track widths are similar.

As for sharing spares, I personally would never mix the wheel and tyre size combinations that you've mentioned on one axle of a Land Rover. You don't say what size tyres you have on the Startech's but I'm assuming something relatively exotic in Land Rover terms if they're on 18x8.5 wheels.

How to resolve that really depends on what you plan to use the trailer for. If it's off-road, expedition type use, then you'd be much better off with a full set of the same sized wheels, either alloy or steel, using the same tyres throughout. If, however, it'll only be 'light duties' then abandon the idea of a second spare and either bite the bullet and get two matching Startechs or fit anything you like as long as it's the same diameter. You can always still use the vehicle spare on the trailer but I'd suggest that the need to do so would be extremely rare.

Some years ago when I towed a trailer a lot off-road, I used alloys on the tow car (a Discovery 1) and steel wheels on the trailer (Desert Wolf). Both the wheels and tyres were the same size though, so I could swap them about if necessary, with a spare set of the appropriate wheel nuts. Darren

110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak

"You came in that thing? You're braver than I thought!" - Princess Leia
Post #711199 7th Jun 2018 7:42am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16809

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
I've crunched some numbers to calculated the positions of the outer bead seat of the rim, and the outer shoulder of a 265 tyre, both with respect to the hub face, thus:

8.5" ET20 rim - outer bead 87.95 mm - outer shoulder 112.5 mm

7" ET0 rim - outer bead 88.9 mm - outer shoulder 132.5 mm

7" ET35 rim - outer bead 53.9 mm - outer shoulder 97.5 mm

6.5" ET20 rim - outer bead 62.55 mm- outer shoulder 112.5 mm

So the last option, the 6.5" ET20 Wolf rims with a 265 tyre will put the outer shoulder of the tyre (and hence the tread surface) in the same position as the wheels on your Defender. Since you want to mix diamteres, you would need to make sure however that the rolling diameter of the tyres were the same, which should be the case provided that your Defender tyres are 265/65 x 18.

Personally I would not mix 18" and 16" rims on the same axle, however for emergency use I don't really see that it is any different to using a "space saver" spare on a car; provided the rolling diameter is the same, or at least very nearly the same, then it is unlikely to cause any damage. Handling and traction/braking performance may be affected.

Although it is not something I would do myself, for road-oriented touring it is unlikely to be a problem, especially as punctures are rare nowadays. For an overland, or off-road-oriented trip, personally I wouldn't be using 18" in the first place since off-road there is a marked advantage in having a 16" rim with a deeper tyre section.

Ultimately I am afraid you must decide!
Post #711206 7th Jun 2018 9:01am
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
I have come to the same figures as above.

Tyres as below;

Defender 265/65R18
Trailer 265/75R16

Using the Wolf 6.5 ET20 wheels I can use 265 width tyres and have the same track as the Defender.

Rolling diameter using diffrent width rims works out at 2mm of difference. (Not a problem)

Looking on the BFG site, the rolling diameter of the tyres are very close, and the 2mm brings them nearly exactly the same.

I don’t plan to mix 16/18 on the same axel unless I completely shred a tyre and it can’t be repaired. However, if the tyres have the same diameter mixing them won’t cause a problem with the LSD and as long as I’m not traveling at high speed, which I won’t be with a trailer on an overland trip, I’m guessing handling shouldn’t be an issue either.

Trip is; Milan to Capetown so I’m sure 18” on the Defender is not 100% the best option, and I would be better with a complete set of the same, but that’s what I’m going with...
Post #711209 7th Jun 2018 9:17am
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
Thanks for the input.

Think I will go Wolf.

Will post some pictures of the build.
Post #711212 7th Jun 2018 9:21am
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey

Click image to enlarge
Post #711215 7th Jun 2018 9:29am
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davew



Member Since: 02 Jan 2012
Location: North Yorkshire
Posts: 888

England 1990 Defender 90 V8 Petrol PU Auto Rioja Red
Sorry but that look like a really bad design.

If the CoG is behind the axle or too far above it you'll end up with horrendous handling problems on road and a tendency to tip over off road (or on road when the handling gets bad). Not to mention the dentists bill when you unhook the trailer and the hitch smacks you in the face ! Smile

Putting two spare wheels as high as you can and as far behind the axle as you can makes no sense for an off road trailer that's renowned for being sensitive to correct loading. Made even worse by extending the body out behind the chassis. You also appear to have a fridge door/locker behind the axle which, again, is one of the heaviest items in the trailer other than the batteries and water.

If you list all the items you want to carry, alongside their weights, then multiply that weight by the distance from the axle (-ve for behind the axle +ve for in front). If, when you add all those figures together, it's not positive by a few kg then you need to rethink your design and where everything is going to be stored. In addition to this, do the same for the left and right positions relative to the centre. At all times bear in mind that you also want the heaviest items as low as they can practically go to give improved stability.

On my trailer the 2 very large batteries are mounted right at the front of the body in the centre, the fridge is positioned to run lengthwise on the RHS, water tanks balance that on the rear LHS between the wheel arch and the rear. With just those items (and the tent) on mine, water containers full, it's slightly nose heavy and then when we load it with cooking equipment, food, clothing etc... we tend to load heavier items towards the front. Before hitching up I always lift the rear legs a few inches and make sure that the jockey wheel stays on the ground fairly firmly but at the same time it doesn't take too much effort to lift the front and the trailer drops back down when released. I suspect that, if you were to build something along the lines shown, even if it was slightly nose heavy, as soon as you start to lift the hitch it would just keep going as the spare wheels moved further back relative to the axle. http://www.yorkshireoffroadclub.net/
Post #711246 7th Jun 2018 1:38pm
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
Posts: 11240

United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey
I've got to agree with Dave - that design has far too much weight behind the axle.

My old Desert Wolf trailer also had a spare on the rear but it had a much shorter overhang. It also had a large fridge, two batteries and one of its' tanks in front of the axle and towed beautifully.


Click image to enlarge
 Darren

110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak

"You came in that thing? You're braver than I thought!" - Princess Leia
Post #711333 7th Jun 2018 8:35pm
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
Thanks for the feedback.

I hadn’t come to actually starting a thread showcasing the initial design, however you have given me some things to think about already.

With the current design and loading arrangements the centre of gravity is still forward of the axel but now I’m thinking it should be further forward.

What sort of distance should the C of G be in front of the axel?

I’m guessing it makes much more sense to extend the chassis of the trailer at the front?

I will rethink the design and create a build thread in the next few days.

Thanks again
Post #711461 8th Jun 2018 5:52pm
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
Posts: 11240

United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey
There's two aspects to this: firstly, achieving a decent nose weight, say 75-100kgs and secondly, keeping the CoG as low as possible. Where the CoG is in relation to the axle will depend on what achieves the nose weight.

I think you said you're starting with a Sankey chassis? It shouldn't really be necessary to alter that as they tow very well, although some people do to lower the hitch and/or increase the load space. As a good rule of thumb though, I'd keep my load within the confines of the chassis, i.e. don't extend it backwards beyond the line of the original tub, and make better use of the space over the A frame. The method of calculation that Dave describes above is the scientific approach to getting a good balance but it just really leapt out how high and far back the twin spare wheels were on the sketch design that you've shown. If you did nothing but put those wheels on the front over the A frame it would probably go a long way to solving the problem.

Incidentally, the official mounting point for a spare on a wide track is on a special bracket over the A frame. Darren

110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak

"You came in that thing? You're braver than I thought!" - Princess Leia
Post #711516 8th Jun 2018 9:21pm
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Yannis



Member Since: 02 Feb 2015
Location: Oxfordshire / Milan
Posts: 400

United Kingdom 2015 Defender 90 Puma 2.2 CSW Corris Grey
So I have decided to extend the front of the trailer by 55cm.

This allows the spare wheel to be mounted on the front, as well as a battery box. This should make it a little easier to load up the trailer and keep a nose weight around 75/100kg.

Making a bit more room at the front, means I can still open the back door with the spare wheel over the area of the a-frame.

Now, what is the best way to do this?

I have seen a few like this;


Click image to enlarge


Or would it be better like this;


Click image to enlarge


The wood is to imitate where the new steel will fit and the chassis be cut. Either a straight cut with the extension butted against the end or an angled cut that will attach to the side of the extension.

Hope it’s clear

Yan
Post #745839 15th Dec 2018 2:19pm
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LandRoverAnorak



Member Since: 17 Jul 2011
Location: Surrey
Posts: 11240

United Kingdom 2013 Defender 110 Puma 2.2 USW Orkney Grey
I think as long as your welding is up to scratch, I'd say whichever is easier to build. There doesn't appear to be any significant difference, otherwise. Darren

110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak

"You came in that thing? You're braver than I thought!" - Princess Leia
Post #745849 15th Dec 2018 3:51pm
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