Hello,

I have a brand new SirrusX 2.0. It came with 170mm length crank. If it's reasonable, I would like to replace the crank with 165mm arms. I have always felt the stock length arms on my former bike were a touch longer thay ideal for me, and as I am short of inseam, and getting older, I thought it would be the ideal time to make the change. I've been amazed what a challenge this appears to be. Initially, we simply contacted Specialized to see if I could order their 165mm set that they use on the smaller bikes in the series. They are not currently available. I bought an inexpensive crank on ebay which would accomodate the correct chainring size with 165mm arms. But, it appears this was made for a wider bottom bracket, or perhaps a wider cassette. It has a chainline of about 51mm, whereas my SIrrusX has about 47mm. I know the bikeshop can navigate this better than I ever could, but not sure I want to pursue it if it's simply going to result in costly modifications.

My initial sense is that simply replacing the stock bottom bracket (122.5mm spindle length) with a narrower one, perhaps 115mm spindle length, may well correct the chainline and run reliably.

Is there a downside to making this change? I guess I should simply take it back to the shop, provide them with the crank I was able to purchase and see if they can make it work. Let them determine if simply swapping bottom bracket will make it work.

Any other advice?

Thank you,
Rob