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New Member
As a newbie I try to keep an ear to anything that gives me a clue to improving my stock, most of which has been purchased second-hand. I notice that certain suppliers offer new wheel sets and except for replacement of missing trucks, I wondered if there was another reason for these being available. I have made the assumption that using metal wheel sets, versus plastic, not only adds a more solid base on which the car can run, but it also adds weight. I have considered just going ahead and buying new metal wheel sets to replace all of my plastic ones. One item that came up, however, was that an all metal wheel set wherein the axle is metal, too, may cause a problem with polarity and other electro matters, since all of the power to the engines is transferred by the track. Is this a valid concern? Is the best resolution to use metal wheel sets with plastic axles, rather than all metal?

Is it a good idea to upgrade my stock, so to speak by replacing all plastic wheel sets with metal?


All metal wheel sets are insulated on one side by the manufacturer, so no problem there with regards to shorts.

Though it can be expensive to convert if you have a large fleet, it is worth the effort. Increased weight lowering the certer of gravity is the birst benefit. Metal wheels also do not collect the crude from the rail that plastic wheels do. Another benefit is the clickety clack sound. If you want to add lights to a piece of rolling stock, all you'll need to do is add electical contacts to the truck for power pick-up.

I have rolling stock from many different manufacturers and eras with many different trucks and levels of quality. All have been equiped with metal wheels and where necessary have had the trucks either replaced or modified for screw mounting. Axle lenght is sometimes a concern, but Micro-Mark sells a truck tuning tool that can solve this problem. I haven't looked back and will never run plastic wheels again.



New Member
Wow, thanks for the input. Now I have also heard that there are different measurements for wheel sets, like 36" being appropriate for passenger cars and 33" for all other rolling stock. Is that accurate?

The same questions for the different styles of trucks, is it just a matter of style and realism? For example, I see Bettendorf and arch bar trucks. Are we just talking more expense for more realistic look or is there a functional difference? I have heard that some of these more expensive trucks have real springs, instead of just stamped impressions of springs.

Regarding lighting up the insides by installing metal wheel contacts, where do you get those? I have an engine that I repaired, but the copper contact pieces were missing so I had to rig contact with a piece of ordinary copper wire. Of course, the copper wire is not of spring metal quality, so it only stays in contact in an on and off manner. I would love to be able to install a better contact to the wheels that can be used on both engines and rolling stock.

Sure appreciate your quick and very informative reply.

Trucks and Wheels

The way I understand wheel diameter is that 36" wheels are/were used on passenger equipment and freight equipment over 100 tons. Trucks are a different matter altogether. It's about era and safety with them. Here's a link to a pdf article posted at Model Railroader. To/Art... Railroaders guide to freight car trucks.aspx

You can also Google "freight car trucks" and you'll get all sorts of information.

As for model trucks I'd stick with the cast plastic trucks. The self centering, sprung trucks can cause you lots of headaches unless everything is absolutely perfect. The more moving parts there are, the greater chance of having Murphy show up unannounced.

To make pick-ups you need sheet brass or phosphor bronze. Phosphor bronze is best as it doesn't corrode like brass. You can also buy various types of pick-ups at your local hobby shop.

Hope this helps.



The tonnage has exceptions so I would always look it up to be sure, but the rule of thumb is as follows:

Look at the LT WT and Load Limit weights on the sides of the cars. Add them together

If the number is:

less than 220,000lbs - use 33"
less than 286,000lbs - use 36"
less than 315,000lbs - use 38" (rarely used)

If it is more than 315,000lbs, then it probably has more than 2 trucks, which distributes the weight so that they can use standard sized wheels (and so that they don't damage the rails)

28" wheels are an exception. The usage of these wheels are not dictated by weight, but for clearance purposes. 28" wheels are mainly used in tri-level auto racks (bi-levels use 33s) and front runners. Some other intermodal cars may use 28s.

Most modern (1990s to present) railcars use 36" wheels, 50 foot box cars (not excess height) use 33s, most freight cars with friction bearings use 33s, all 40' box cars use 33s, and most modern tank cars use 36s. (older tank cars may use 33s)
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Furthermore steer clear of the wheelsets that have metal wheels but plastic axles like Kadee and P2K, they tend to get the axle endpoints damaged when pulling them in and out of the trucks, and not roll as well as those with metal axles. Intermountain wheelsets are my standard.
I strongly urge everyone to standards check all their equipment, it'll save you a ton of headaches in the end. Standards check should include the following;

Metal Wheelsets (improved rolling ability and less prone for derailments, also keeps track clean).
Kadee Couplers (won't bend break or slip, and holds better)
Coupler Height check (should have no less than 75% coverage on a coupler height gauge, I prefer 85%)
Couplers should swing side to side freely, but still center (I prefer Whisker couplers for their superior centering ability)
Wheel Gauge check (NMRA gauge)
Both trucks should rotate freely, one truck should have limited side to side rocking ability while the other should rock side to side freely.
NMRA weight (use a dietary scale to check weight. I follow the NMRA standard up to 60' cars, but then limit longer cars to that weight so they don't get too heavy).

At the club my equipment rolls along flawlessly while others who do not standardize their equipment spend the whole time cursing their equipment due to all the derailments and pull-aparts. Spending the time to go through your equipment is vital to the enjoyment of the hobby.


Master Mechanic
Furthermore steer clear of the wheelsets that have metal wheels but plastic axles like Kadee and P2K, they tend to get the axle endpoints damaged when pulling them in and out of the trucks, and not roll as well as those with metal axles...
Again I have to disagree with this advice. If the end points of these nylon axles are being damaged, they are simply not being inserted correctly. The way to insert nylon axles into a truck is to spread the sideframes apart wide enough to allow the axles to be inserted into the journals without being bent or damaged. This does not damage the sideframes at all, and ensures a damage free fit.

The problem with a needle point metal axle in a nylon bearing is over time, the bearing gets worn down faster than if the needle point was of a similar material. The harder material will always wear the softer material faster.

I have nylon KD wheels from the 1970's, that are still rolling as well as when they were inserted into Athearn trucks. I can take cars with this setup, set at the "top" of my layout, and these cars will not stop rolling until they're at the "bottom" of the layout, in the staging yards a good 75' away. Not even my best metal trucks, (Central Valley), roll quite that well. Almost, but not quite. These show almost no wear at all, while some metal axle trucks I had were on their 3 or 4th nylon truck. In fact I only use metal axles now in metal trucks only, due to the wear problem I have experienced over the years.
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I'm having wheel problems too.

There is more to this than wheel diameter. The axle length from point to point varies with different manufacturers.

Some of my cars use 1.080 inch axel point to point.
Some of my cars use 1.00 inch point to point.

So where can a person find dimensions of the wheel sets??


Here's a somewhat incomplete list by Reboxx (owned by the guy who is also co-owner of Intermountain, the Reboxx wheels come from the same factory as Intermountain)

IMO metal wheels with metal needlepoints roll better with less friction, but some people swear by P2K wheels or Kadee wheels (which works to my advantage when I want to divest myself of them after swapping in Intermountains! :D) Athearn makes good wheels, the older wheels had axles made of delrin as are the trucks, making for very low friction and decent rolling qualities. Those are pretty much the only wheels (besides Atlas wheels) where I don't swap them for Intermountains.

Metal couplers are a must (most people use Kadee). Plastic couplers uncouple easily and if you run a long train, the weight of the train will cause the coupler shank to twist and uncouple. Make sure to check the coupler height (the kadee height gauge is like 3 bucks) since misaligned couplers will cause uncouplings.

NMRA recommended weight is also... well, recommended! If the car is too light, it may derail if in front of heavier cars, or derail at the end of the train from bouncing over switches, or if you reverse the train. Cars that are too heavy may wear out the trucks faster, and you won't be able to pull as many cars with your engines. Rule of thumb is, measure the car from coupler to coupler. Take the measurement in inches, divide it in two, and add one. That is the NMRA's ideal weight for a freight car. Some RTR cars may be about an ounce underweight. Usually, that isn't a problem.


Here's a somewhat incomplete list by Reboxx (owned by the guy who is also co-owner of Intermountain, the Reboxx wheels come from the same factory as Intermountain)
I was confused at first. Their web page links are backwards. The link for wheelsets by axle length are really by manufacturer, the link for wheelsets by manufacturer are actually axle length.

IMO metal wheels with metal needlepoints roll better with less friction, but some people swear by P2K wheels or Kadee wheels (which works to my advantage when I want to divest myself of them after swapping in Intermountains! :D)
Metal to the correct plastic should be very low friction. It should be better than plastic to plastic.



years ago I spent the money on a set of Kadee sprung metal roller bearing trucks, and they rolled like crap. I also have a friend who has installed the P2K wheelsets into several cars, and many of them don't roll all that well. On the other hand I've installed the Intermountain wheelsets in hundreds of cars and they always find every little grade or slope in the layout. In fact it can be a little bit annoying as loose cars love to roll away. I'll repeat, stay away from plastic axles and save yourself the headaches.

Dollie's Dad

Gandy Dancer
Interesting discussion, and seemingly good arguments on both sides. I lack the experience to make any recommendations beyond endorsing the use of metal wheels. I haven't used my equipment enough to know the long-term effects of metal axles vs. plastic. Logic tells me plastic should work just fine, though.


Master Mechanic

I've been in this hobby seriously since I was 8 back in the 1950's. I consider getting "serious" as the first craftsman kit I ever built. I still have that car. Since then I've built hundreds if not thousands of craftsman kits of all types. Almost half my loco roster is kit built locos, all regeared and can motored equipped.. I still do some professional painting, and custom model work.

I've had metal axles rub thru Athearn journals over a period of years with heavy operation and I've had metal trucks destroy the ends of plastic axles. Before there was a thing as a "truck tuner", all we used were drill bits to ream the journals out with to get better rolling qualities out of the truck, and it worked very well too.

I also know that a harder object will wear down a softer object much faster than similar materials. IIRC, its an engineering principle that bearings should be made of similar materials to insure long life of the bearing and the item it supports. Sure has been proven to me over the years with axles in trucks.

I still put nylon axles into nylon trucks and metal axles into metal trucks.


Well, it appears that we might be splitting hairs so to speak. I did a little testing with a new from package P2K truck and another Accurail truck sideframe set with intermountain wheelsets. I put both trucks on a 16" section of track and slowly lifted one end. Both trucks usually started rolling at the same moment. Occasionally the IM wheels took a ever so slight lead. I then turned the trucks on their side and used my hand to get one wheel spinning. The IM wheels generally stayed spinning longer, but only by seconds. It feels like the P2K axle has a faint cast line that can't be seen, but can be felt in the spinning of the wheel. It's that cast line that I believe has caused problems with some wheels in the past. The old Tyco equipment was similar, but with a much worse cast line that caused those cars to roll so poorly. I remember when I bought my first Athearn cars years ago as a kit. Those steel axles rolled so much better than the tyco cars I owned up to that point.


Well-Known Member
Say Ron,

As far taking an axel out from a side frame on freight cars anyway I've always slightly twisted the side frames vertically, one pushed away slightly and the other moved toward yourself which creates a greater diagonal distance and the old axel false out or the new one goes in easily.

This was the only way years back it could be done due to all metal sprung truck frames.

The other thing is if your using metal wheels & axels you need to be sure to put the insulated wheels on the same side of the truck to avoid shorts and if one truck is removed from a tender that picks up power for the engine motor be sure both trucks have the insulation on the same side or again they'll short out and they have to be on the opposite side from the engine pick-up side.

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