If a tool finds a collapsed section of host pipe, a front expander can lead the tool off track and could snap the winch line. Grundocrack tools with rear expanders are much more likely to stay inside of the host pipe.

When a front expander encounters sediment in host pipe it can lift the tool off course. Grundocrack tools equipped with a rear expander are a lot less affected by sediment since the majority of the tool is already inside the host pipe. The tool can then act as a guide to assist in maintaining accuracy and grade, while the bursting is left to the rear expander. It is recommended to clean old lines before all bursts.

Often, tools are unable to navigate bends with a large front expander. Smaller Grundocrack tools with rear expanders are able to better navigate gentle bends in host pipe. A schnoze guiding head is also effective when used with rear expanders.

Sometimes a point repair clamp causes stoppage of a burst because the front expander is too large to gradually spring the clamp open. A rear expander allows the use of a larger, more powerful Grundocrack tool that can still fit within the host pipe to provide the gradual splitting action required to conquer point repairs.

In a successful job, old pipe must be compacted outward as it is being burst. However, certain types of soils and host pipe materials, or upsizes of more than one pipe size, may cause a front expander to "push" pipe well ahead of the pneumatic tool, rather than burst from the inside out. In severe cases, pipe pushing may cause blockage and possibly stalling of the tool. A Grundocrack tool equipped with a rear expander and a guiding head schnoze works well to keep the burst working from the inside out, compacting pipe fragments outward.