Crankset and casette advice needed

janetthompson

I currently ride a double Shimano Tiagra (38/52), with a 9 speed casette (12/25). It's wearing out, so I'm looking to upgrade it to 105 as I replace. My LBS tell me I don't have to change the shifters as they're compatible with the upgrade. So, a few questions regarding this:

1. Where do I measure to and from to measure the crank length? I'm guessing from the middle of the bottom bracket bolt to the middle of the pedal bolt?

2. I can't seem to find a 9 speed 105 casette. Can I use a 10 speed 105 casette instead? Or would I be better off getting a 9 speed ultegra casette instead? (And will the three different components work ok together?)

There's probably more questions, but I can't think of them right now.

Thanks

Janet

Bobbinogs

Just a quick question, when they say "it's wearing out", do they mean the crankset, chainrings, the cassette or all of them?

What are the symptoms?

mrwibble

is your front chainring wearing out? the cassette maybe worn but there could be plenty of life left in your chainrings.

janetthompson

No, it's the chainring that's wearing out. There's at least 6 of the teeth which are worn down or have little bits broken off them . My LBS did say that there was no hurry to change it as it's still shifting ok, but that I would need to do it eventuallylly, so I'm starting my research now. I just figured that I may as well replace the casette at the same time.

Ciclicasati

The 105 9speed cassette is called HG70 I think, HG50 is Tiagra. They are pricey though. I run the Sram PG950 which I got for under £30, coupled with a KMC x9L chain for and dura ace chain rings works fine.
Chainset length is measurement should be stamped on the inside of the crank arm near the pedal base. You can replace just the chainrings or the whole thing. If you have 52/48 chainrings you need 130bcd dimension ones. If you have a compact 50/34 set up you need 110bcd chainrings. Chain rings can also be pricey and you may be better getting a whole chainset and floggin yours on ebay?

This wasn’t a sales pitch but if you fancy one, I have an Ultegra 6700 compact chainset with 170mm cranks available.

appletrees

Crank length will usually be stamped on the back of the crank arms, most likely around the pedal thread. If it isn't, you're correct - centre of bottom bracket axle to centre of pedal hole.