The major source of friction, however, was the Midland's policy of using small engines, adding another if the load warranted it, or for hilly stretches. This had worked perfectly well, for the Midland's track in general was level, but trains were becoming heavier. The other major member of the grouping, the LNWR, had already invested in larger engines for its lines north of Manchester. Another passion imported from the Midland was for standardisation, which, in the case of axleboxes was to prove problematic for future heavier locos.