When I’m really going for it, like a race finish not closing a gap my rear wheel starts jumping about. Why?

Regardless of the real answer i’d claim it as a demonstration of the awesome power of your legs, which is what you’re hoping for isn’t it?? 😉

You are badass. Period.

its your bike coughing with fear.

Your real name is Jens

http://www.bikeforums.net/archive/index.php/t-656228.html

backs getting light by the sounds of it.

I guess: You’re in the drops, weight forward – back wheel is unweighted and loses grip slighty with the right/left motion of your legs.

a stiffer wheel would suffer this more than a flexy one.

It’s the sonic boom raising your rear wheel slightly

This happens to be as well. Shifting the weight further back to maintain traction helps, as does focusing on keeping it on the ground (not sure what this changes in my technique though)

I was wondering if it was a size thing?

the link i posted really does have quite a good explanation for this, it has happened to me.

it’s all in the hips.

Have you tried administering less GigaRads? Perhaps adjusting to setting ‘4’ will help.

Watch out, they’ll get ya!

You are pulling up too much in an effort to get more power, and probably rocking about a bit much. Concentrate on pressing down, maybe change up a gear if possible.

bad pedal stroke …

same reason you see many folk strugling to get up a steep muddy climb and the next guy comes along and makes it look effortless – kenta im looking at you ….

Cheers c13. I’ve been working on cadence, I might have a fiddle on the circuit this week. It’s not the sort of thing you can think about whilst it’s happening.

crikey it looks like I’ll be up in the Peak on October 2nd. I think it will be a cross ride from Stoney Middleton way. Any good for you?