Sprint tri > bike training advice?

[Deleted User]

Hello all,

I have been running for a long time, mainly trail. The last two years I've had the great chance to enter the Ilfracombe Triathlon, which is a particularly hilly Sprint Marathon.

Now - until now I have simply based my training on running and a bit of swimming (I try to train in a swim club - even when i must be the worst swimmer in history!). But this year i want to do intense bike training because although i feel aerobically very fit because all my running / I know i could improve my riding times a lot.

My question is simple: what would you fine people in these very forums suggest as a bike training that wouldn't take more than 3 days a week, aimed for a very hilly 25k route - and that wouldn't force me to stop my strictly running training? (I am aiming for the north Devon Marathon next year as well - so i really want to be able to train for both events in a consistent manner)...

I know that participating in such disparate events means that i will not be brilliant at any of them - BUT at least i want to make sure that my riding improves substantially this year...

Thanks in advance!