Numbness is more dangerous than pain.

Numbness is the main cause of Charot's foot called Neuropathic arthropathy:
http://en.wikipedia.org/wiki/Neuropathic_arthropathy

When numbness is present, one cannot feel where pressure and injuries are occurring in the foot.

If you search Charcot's foot on Google, and click on images, you will see some horrific things that result from numbness.

I'll give a further example. I met a medical doctor at a conference once, and he was moving about with a little leg walker where one kneels on a pad and pushes along while walking on the good leg. The subject was B12 and he came up by me where I was sitting to ask the presenter a question during the break. She was busy so I asked him about his situation. He said he did a very stupid thing. And I had to agree when I heard his story! Here goes.... He bought a pair of new golf shoes and did not break them in properly. He developed a blister on the ball of his foot. Which hurt like the devil. He had a special meeting coming up for a golf game and get together and rather than miss it or not participate, he numbed his foot with a lidocaine shot. (I am thinking he was a podiatrist or DO), and did the golf date. What happened? His blister which was telling him to not walk on it until new skin formed ....became 100 times worse, the tissue beneath the skin ulcerated and he could NOT heal it up! He was at this conference to do his CE but also learn about B12. He had been on his kneeling walker for over 6mos, had been hospitalized with a severe infection requiring Zyvox antibiotic, which then lead to a neuropathy! His future was guarded still as the tissue that ulcerated out, while his foot was numb wouldn't grow back.
So the ulcers and horror pics on the Google search reflect that result too.

Pain, as terrible and wearing as it is, is really our friend, when it comes to neuropathy. It tells us to stop whatever is causing the pain. And there are times we need to listen to it.

The bike riding is less weight bearing and may be less dangerous than the boarding you are doing as long as the resistance is kept low and you don't put too much pressure on your feet. But I myself have learned that if you continue to do weight bearing or pressure causing activities when your feet are numb...you risk injury and that injury may not heal up in the end.

So do be careful.