looking at getting a set, it seems a waste to buy 4 for the drive axle, can i not leave 2 steel ones on the inside?
Yes you can on my last lorry I treated myself to a set of durobrites and kept the steel inners without no trouble at all
alloy against steel encourages rust.
I had the wheels on the lorry for about 6 yrs before I sold the lorry with the wheels it passed every mot and never caused me any problems I was going to buy some old ally wheels to put on the inside when I bought the durobrites but was told there was no need just use your steel ones which I did
ellies dad:
alloy against steel encourages rust.
simple , paint the mating faces with coppa slip 
Dissimilar metals in direct contact result in corrosion. Aluminium does not like copper even more than it doesn’t like steel. Add salt, water and a bit of dirt to keep and retain the moisture and the nice shiny alloys will deteriorate albeit not very quickly.
i was told you could buy something (rubber/plastic?) thats like a thin wheeltrim that goes between them so the 2 wheels never actually touch
ellies dad:
alloy against steel encourages rust.
So what metal is the hub made of that these wheels are to be seated on ?
1970commer:
ellies dad:
alloy against steel encourages rust.So what metal is the hub made of that these wheels are to be seated on ?
now why didnt i think of that! surely that blows the above argument out of the water ?
cav551:
Dissimilar metals in direct contact result in corrosion. Aluminium does not like copper even more than it doesn’t like steel. Add salt, water and a bit of dirt to keep and retain the moisture and the nice shiny alloys will deteriorate albeit not very quickly.
common or garden grease ■■? 
syramax:
ellies dad:
alloy against steel encourages rust.simple , paint the mating faces with coppa slip
Silicone grease is much better choice but a lot more expensive.
Galvanic corrosion is an issue and a common visible example is round the hinges on trailer doors where the door is faced with aluminium. Often when you unbolt the hinge there is just white dust behind.
Stainless to aluminium is about the worst for it and a lot depends on how much moisture can get in as it’s an electrochemical reaction, like inside a battery.
With metal lumps, like wheels and axles, that large nothing’s going to rot away but if the wheels are removed infrequently they could be very stubborn. Might be worth putting a bead of sealant round the whole circumference where the two wheels interface to keep the water out.
I’m sure I’ve heard about alloys not liking sitting on a steel hub. I may be wrong, won’t be catastrophic in most cases but I’m sure there have been some cracking or rusting examples.
American trucks where they’re big on alloy wheels can come with factory aluminium hubs.
Lots of US trucks only run alloys on the outer drive wheels.
Should be with high temperature nylon spacers according to their US literature:
On occasion Alcoa aluminum truck wheels are operated dualed with a steel inner wheel. When this
application occurs it is recommended to use a high temperature nylon spacer, because of corrosion
issues. In the event a steel inner wheel is used, extreme care must be exercised to properly seat it to
the hub or drum prior to mounting the outer aluminum wheel
Own Account Driver:
Should be with high temperature nylon spacers according to their US literature:On occasion Alcoa aluminum truck wheels are operated dualed with a steel inner wheel. When this
application occurs it is recommended to use a high temperature nylon spacer, because of corrosion
issues. In the event a steel inner wheel is used, extreme care must be exercised to properly seat it to
the hub or drum prior to mounting the outer aluminum wheel
Thats what i was thinking of, just found some, Alcoa sell them, there called Discmates
It may be a problem, but only if you have to use wheels with 32mm stud holes and retro wheel nuts because the studs arn’t long enough for alloys, the sleeve won’t pass through the steel wheel which will have 26mm stud holes.
Big Joe:
It may be a problem, but only if you have to use wheels with 32mm stud holes and retro wheel nuts because the studs arn’t long enough for alloys, the sleeve won’t pass through the steel wheel which will have 26mm stud holes.
If you use front wheel nuts it should overcome this issue.
Got a couple of neglected ones off ebay to go on the inside in the end, seemed the easiest solution