UKH

I'm looking to change chainset/bb as it is 15 years old and past it's best. And probably obsolete as it is Truvativ ISIS 68/108mm. Bike is Cannondale caad 5. 2x9speed shimano 105 if that helps.

Any advice on the compatible options would be appreciated. I know one option is to get a new bike but I'm quite attached to this one! Thanks.

You will probably need to change the cassette and chain too, otherwise the new tooth shape on a new chain set will be a poor match to the worn chain and cassette

You can still pick up ISIS BB though it might limit you on available chainsets. Bit of Google-fu will turn up what is and isn't compatible. Bike Radar (website) and such like will have loads of advice.

Do you have a torque wrench?

No, but I can borrow one.

In that case you should be able to fit the new one yourself. If you can first remove a 15year old bottom bracket..

What crankset have you already got because Shimano 105 would have been Octalink rather than ISIS?

I use Octalink on all my bikes. I have a pair of "new old stock" 105 cranks that I put on my roadbike at the end of last year, they are lovely. I have Shimano LX Hollowtech-1 on my MTB. I have and will continue to replace chainrings and bottom brackets before switching to a Hollowtech-2 or other outboard bearing systems, which In my opinion are a flawed design.

The cranks are definitely Truvativ ISIS as it is marked on them. I had assumed the BB would also be made by Truvativ, but I  don't know  for certain. It seems a bit strange that the bike doesn't have a matching Shimano chainset - I bought it new.

Anyway it's interesting what you say about Hollowtech as I was thinking that may be an option with a Shimano chainset. What don't you like about them, I've heard they can creak?

Also getting hold of 9 speed stuff now seems a bit problematic. I haven't considered the Octalink, 9 speed chainset option yet so I'll  have a look into that. Complicated innit. I might get a new bike yet!

Cheers for your thoughts.

cost cutting, Shimano chainsets are expensive.

Having separate bottom bracket cups that require the user to set the preload is a flawed design (compared to a one piece cartidge bottom bracket) that is prone to misalignment and rapid failure.

I'm still running 8speed on all my bikes. 105/XT level kit is not available, but I don't care about the few extra grams from using cheap entry level cassettes that are still widely available, 8speed chains cost less than a tenner I use 10 or 11speed chain rings because they are backward compatible. 

Hi,

I have same bike as yours, from new. Last year I renewed chainset, BB, derailiers, brake levers(it originally had shimano tiagra)I put Shimano 105 set on.  All fine except front derailier wont shift to big rim at moment as Ive put larger tyre size on for comfort!

"All fine except front derailier wont shift to big rim at moment as Ive put larger tyre size on for comfort!"

? you're front derailleur wont shift onto the big ring because of the tyre size ?

After changing my groupset , then subsequently changing the cables again I found it took a few goes to eliminate cable stretch, also easy to misalign the inner cable guides to cause friction. Did you fit a cable extender screw in the front derailleur cable?

Yes I didn't get that either. A wide tyre would foul the chainstay first looking at my bike.

Hi,

when front deraliers on small chain wheel(inner) the tensions off cable.  When I select larger chain wheel(outer) cable is tensioned which pulls the lever mech(point where vcables attached to deralier) downwards/inwards(cantilever effect) and so into larger size tyre.  I can possible ways and read about them to rectify it, by filing down cable attachment lever, putting a packer under deralier attachment band etc, but at moment with 11 speed Im happy.

Thanks, did old BB come out OK and are you happy with new Hollowtech BB?

You'll probably need to buy extractor tool to remove old BB, new ones are easy to fit, not so much to worry about with these old alu frames.