Just for the sake of any one new to the hobby reading this thread, it is not a case of "most newer O won't run well on O-27." It depends whether the product is scale or traditionally proportioned.
"Many of the starter set locos now seem to have trouble with the tight o27 curves" is also an overstatement. This may be more true of the MTH starter sets, since the Railking line has gone more scale. But as far as Lionel stater locos, many STILL will run fine on the 027. But even before the scale trend, many MTH items were listed as 031 minimum curve, when they in fact WILL run on an 027 curve. I asked MTH about this and was told, that because they did not make their own 027 track, if an item HAD NOT been tested on an 027 curve, it wouldn't be listed as being able to do so. The MTH Railking dump car is listed as 031 minimum, but IT WILL run on and clear the 027 swtich box housing as I've done it myself.
The Lionel starter set GP-7/9/20/38, U36B will all run on 027 curves, as will the 2-4-2, 4-4-2, General and Dockside steamers as well as all the Thomas locos, the industrial switcher, NW2, RS3, the older model centercab switcher, the Alco FA and many others. There are semi-scale steamers that also negotiate the 027 curve. The Harry Potter type steamer will not run on 027 curves unless it is a wider radius curve and I've read here the 0-8-0 starter steamer also has trouble on 027 27 inch curves.
Years ago I spoke with one company CEO about the changes in product labeling. He told me the train market associaties 027 as meaning non-scale or toy, and they were trying to move away from that perception. Which is sort of funny, since they also acknowledge the traditional side of the market is way bigger than the scale side, and most profits are made on the traditional end.
In current Lionel catalogs, the minimal curve listing has often been inaccurate, I suspect partly because of FasTrack being the main track line, but also I suspect out of carelessness: because some products are listed as minimal 027 curve and some are not - even though they will make the curve.
If you look at Lionel catalogs pre 2003 when FasTrack became the starter set track system, you'll see many locomotive types in starter sets with 027 track in 27 inch diameter curves. If one is using 027 track, it simply pays to ask questions before making a purchase.
I've posted this video before, but you can see a wide variety of product ALL making the 027 curve and clearing the 027 switch box housing, including some Weaver cars, which are scale proportioned. I think the Reading loco is a Williams GP38 and the WM loco is the Lionel starter set version of the GP38.
