Regarding a bowing grand carriage.One possilble solution is to reset the carriage. To do this the piano has to be removed, all of the set screws or bolts loosened inspected and taken out,if necessary. The carriage should be inspected for bends and the sliding parts freed. The tricky part is getting the exact size and configuration. For this it is helpful to have a person at each leg.Tighten the bolts with box wrenches, not pliers,or crescent wrenches, and the piano put back on. Drill all the way through for extra set bolts if deemed necessary. If it still bows, at least you have experience when it comes to installing a new one. Richard Moody ptt
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