Why torsion bars would not improve the early Sherman

Would fitting Sherman tanks with torsion-bar suspension from the start improve combat performance or battle-damage repair?

Not overall; it could help late overweight variants, but early adoption would delay production and make rapid modular repair harder.

The original M4 inherited a proven suspension and an existing parts base from the M3 production system. Torsion bars could offer greater mechanical reliability once up-armoring and the 76 mm gun pushed later Shermans toward the limits of their suspension. That advantage arrived when the tank was already approaching replacement, however. Earlier adoption would have delayed an already late combat debut and made damaged suspension harder to exchange as a field-replaceable module.