I'm in the process of taking off the crank set on a Trek 1500 I just bought to replace it with an Ultegra crank. The crank is a bontrager race crank set. I have the bolts off, but when I went to use the crank extractor, I noticed that the bottom bracket is hollow (you can see all the way through to the other side), which would explain why I wasn't having any luck using my extractor (the extractor should push against the bottom bracket, right). Is there a specific tool that I need for this. I did notice that there is some splining on the inside of the crank if that helps. I'm just stuck. Thanks.

The current model 1500 uses an ISIS spindle crank. I've never worked on that exact model crank but most similar cranks have self extracting crank bolts. Check the following link for help. http://www.parktool.com/repair/readhowto.asp?id=120

Thank you for your reply. That would explain a lot. I read that section of the park tool guide last night and again this morning after your post, but it is just not clear to me. I removed the crank bolt. What is the next step? It seems like the parktool site just keeps identifying different types of cranks but never really says how to deal with each one specifically.

Thank you for your reply. That would explain a lot. I read that section of the park tool guide last night and again this morning after your post, but it is just not clear to me. I removed the crank bolt. What is the next step? It seems like the parktool site just keeps identifying different types of cranks but never really says how to deal with each one specifically.
If it has self extracting crank bolts, there will be a ring (cap in picture) outside of the bolt (fixing bolt) with a hole big enough for the hex wrench. Put the bolt back in (don't tighten). Put the ring back in. Insert the hex wrench and back off the bolt. It will push against the backside of the ring and remove the crankarm. - TF

That helps a lot. Thank you so much. I will give it a shot tonight.

That helps a lot. Thank you so much. I will give it a shot tonight.

Those cranks don't come with self extractor bolts. You'll need a tool like the Park CCP-4 (http://www.parktool.com/products/detail.asp?cat=26&item=CCP-4) to remove the crank. You can also spend 10 cents by using a dime at the end of your current tool so that it can press on the BB spindle. The dime will usually last for a few removals. I've found a dime to be a little too wide for Octalink BBs, but seems to work fine on ISIS.

The cp4 I got last night did the trick. Thank you everyone.