Originally Posted by
carpediemracing
Mike Engleman was a marathoner before becoming one of the top domestic road racers around.
However...
There are three types of runners that cycle out there.
1. Strong runner that learns to adapt to group riding/racing tactics/ideas. The local strong team is CCNS, headed up by a guy Aidan that used to run 4:30 miles. He is an extremely strong racer but he's also really smart tactically. This makes him a very good racer. He's an ex-pro, current Cat 1, and totally rocks on the bike.
2. Strong runner that does not adapt to group riding/racing tactics/ideas. Locally there are some unnamed very strong riders, ex-runners, who simply cannot wrap their heads around race tactics. They can kill it when it's either a TT or a long climb, when tactics don't count for anything, but in a regular crit or otherwise non-selective course they are lost. They hammer at the front, trying to use their running tactics ("run really fast until no one is left") in a bike race.
One such rider is a friend. In her first crit my brother told her, somewhat facetiously, "go really hard until you drop everyone, lap the field, and then you don't have to sprint". She did just that - she pulled the field around until someone let her wheel go, she lapped the field solo, then she pulled the field around until half a lap to go. She readily admits she's not good with the tactics and group riding stuff.
3. Average runner. They get split up between the ones that understand group riding and those that don't. Either way they're just like the rest of us.
The tactics are a big factor yes, that can make or break the transition to high level cycling.
However, even without the tactics, great runners, while they are instantly solid cyclists usually way faster than recreational or even Cat4 cyclists, have to work pretty hard in general to get to competitive fast levels on the bike enginewise. If strong runners were uniformly only limited by tactics, pure runners would be winning or contending for top spots in the local TT bikes races, but these are invariably won by people who train heavily on the bike.
There are a few runner->cyclist standouts that seems to jump effortlessly to top level cycling, but I wager that these folks would have made that jump pretty similarly without their running background - that easy transition for them to high level cycling was due to their cycling talent, and not their running ability.
However, in general, unless you're a competitive road cyclist who races (particularly at Cat3), expect to get your butt handed to you pretty regularly by fast amateur runners. Even a mediocre-fast runner who cranks out 5ks in 20 minutes will destroy most recreational riders at all except long distances with 4-6 weeks on the bike, purely on their VO2 and leg strength developed from running.