Anchor Road, Canons Road, Canons Way, Lower College Street, Bridge Valley Road, the Portway, some roads around the Cumberland Basin System and others will be closed early morning until mid-afternoon.
The race starts at 09:30 from Anchor Road, Harbourside.
More top news
Six people have been arrested after an "enormous" cannabis factory was found in a nuclear bunker. The value is thought to be more than £1m.
Storm Doris reached the South West this morning. There have been reports of fallen trees and strong winds across the region.
The company advised customers to "unplug" their tumble dryers and "do not use it" if they are subject to the recall.