Bachmann HO Train Wheels

[blitterell]

I need to buy some Bachmann HO Wheels, but I see that there are 2 different sizes; 33" and 36".
I have no idea which I should buy; please advise. 

[richg]

Measure the diameter of the wheels. Multiply by 87 to determine the size you need.
Look at the wheels side by side. The larger will be 36 inch. The smaller, 33 inch. This should apply in most cases with Bachmann HO scale rolling stock.

Rich

[blitterell]

Thank you for you answer; however, I measured the diameter and came up with .5 inch X 87=43.5 inches.  I still don't know which size to buy.

[Woody Elmore]

One eighth inch is close to the 3.5 mm used in HO. It is a tad too small but still useable. Measure the wheel's diameter with any ruler. If the wheel measures a little more than three eighths inch it is probably a 36 inch wheel. Less than that should be 33 inches.

The best suggestion for anyone getting into HO is to get an HO ruler and an NMRA gauge.

[richg]

Dimensional info.

http://www.urbaneagle.com/data/RRstddims.html

Many years ago I use to figure the size with a Drafting Compass an a ruler with fine divisions. Ok, old school. I guess the Drafting Compass is still sold. I learned to use whatever i could find.
I had the actual diameters from the Kadee catalog so it was easy to figure this stuff out.

Below is a very useful tool for figuring sizes.

I bought one like this about 25 years ago and it served me very well.
http://www.micromark.com/economical-vernier-caliper-5-inch-capacity,6473.html

I now have this one.
http://www.micromark.com/digital-caliper-with-standard-numerals-6-inch-capacity,8094.html

There are all kinds of online calculators if you find some thing in Metric as many manufactures specify Metric a lot today.

Rich