Paul,
Dogs pull because they think they're helping. It's a fairly straightforward procedure to teach them not to, but it takes some patience and effort. Start off with a short leash. Start walking, with a command like "let's go". As soon as they pull, you stop, and say "no". When the dog looks back he'll stop pulling, and you can start up again. Continuing the walk is his reward for not pulling.

Supposedly you can train a dog to pull on a harness but not a collar, like for skijorring. I haven't been able to do that with my dog, but I haven't put enough effort into it.

Anyways, the springer puts the pull from the dog low on the bike, so he will not pull the bike out of control no matter how hard he pulls.