Chainrings/crankset compatibility

[potsy]

Hi,am about to buy some new bits for my Secteur Sport and wanted some help with it all.
Was going to replace like with like with regards to Bottom bracket,cassette etc,but am not sure about what crankset to buy and does it have to be compatible with the BB.
Was going to get this one-http://www.chainreac...x?ModelID=43206 which is a Sora triple,but would this work with a Octalink BB?
Thanks.

Some spec info as is-

Crank Set: Shimano FC-R453
Chainrings: 50 x 39 x 30T
Bottom Bracket: Shimano BB-ES25, Octalink spline, cartridge bearing, 68mm x 118mm

 

[RecordAceFromNew]

As you can see from this the new chainset requires a Hollowtech 2 bb, so the old octalink will have to go.

I am not sure about this particular one but some Shimano chainsets come with matching bb (and washers to allow fit to 68mm and 73mm bb shells), you might want to give CRC a call? As you can see otherwise the bb needed is an SM-FC4500.

The only curious thing is are you sure the existing chainset is a R453 and the bb is 118mm? I am asking only because the R453 spec sheet specifies a 121mm bb. Because of this unless there is clarification it is tricky to suggest another octalink chainset as an alternative replacement.


Otherwise I don't see why the sora shouldn't work perfectly. It seems your existing chainline should also be 45mm, you are running a triple x 9 speed already, and that the new and old chainsets have the same large ring and tooth difference, all meaning no shifter, front mech, rear mech or chain implications, so it should be a simple replacement (except perhaps depending on how worn the old chainset/chain are you might want to replace the chain at the same time).

Hope it helps.

 

[potsy]

Thanks for the reply I appreciate the help,have taken the info from here-
http://www.specialized.com/gb/en/bc/SBCBkModel.jsp?spid=45855&eid=4951&menuItemId=0
Which is the same as I originally posted,. Am looking at changing the whole lot sometime soon new chain,chainset,cassette etc.
Bit of a minefield if you're not 100% sure of what you need though.

 

[RecordAceFromNew]

Potsy, just in case, it seems the spec you linked to is for a 2010 model while yours I presume is not (and to have worn out so quick)? As you know manufacturers keep the name and change the specs all the time. If I were you I would check exactly what you've got first, otherwise you might be buying something that is perfect for replacing bits on a 2010 bike, but....

 

[potsy]

Mine is the 2010 model,3000+ miles in all weathers has started to take it's toll.
Has had a new chain at 2000 miles and that is all.
Not quite ready for the new bits except maybe the BB which is sounding a bit gritty now,just getting my head around what I need tbh.
Planning to use the hybrid over winter so will try to strip the secteur down then and check the parts I need.
Cheers.

 

[potsy]

Well I've found the Cranks here-http://www.niagaracycle.com/product_info.php?products_id=434715
but according to that it uses a 113mm BB

Definitely stamped on the bike as a 453,so if I take off the cranks and the BB and measure it,should be able to find what it is.
Confused myself more now

 

[RecordAceFromNew]

According to the chainset's official techdoc a double (R450) should use a 113mm bb, and possibly the advert (see the photo?) in your link is a little confused.

If I were you I would check the front chainline before dismantling anything, and then of course the bb length to be sure. The bb's spec is usually labelled on the bb too.

 

[potsy]

Think I've got a bit confused by trying to match exactly what I have now,when all I really want is something that will do the job.
The Sora one i linked to earlier would be ideal if it comes with a BB or does it have to be an Octalink to fit my frame?

 

[RecordAceFromNew]

Whether it is octalink or hollowtech is not determined by your frame, it is determined by the chainset. Your frame can accommodate all types of bb as long as it has standard English thread and is for the bb shell width of your frame.

I am sure you will get there!

 

[potsy]

I am sure you will get there!

Cheers,it might take a while though

 

[potsy]

Well I ordered the removal tool and new BB at the same time,took out the old one today and yes you've guessed it I ordered the wrong size

The spec sheet I linked to said 118mm and it was in fact a 121mm. I'm guessing this is crucial? Will send back the BB for a refund/exchange.
May as well just run the existing one a bit longer and then get the new crankset in the Spring.
I hate bikes

 

[RecordAceFromNew]

Aye, can't say I didn't warn you

BUT if I were you I would try this:

I would put the old bb and chainset back, and measure whether either of the cranks is anywhere less than 3mm from any stationary part of your frame, in particular where the crank arms are near the chain stays and the bb.

If there is adequate clearance, I would then check to see if the front mech has the flexibility to move further in when it is on the small ring, by adjusting the L screw, by a couple of mm. Since the spec sheet says a 121mm bb gives a 45mm chainline, this step is quite important.

If both the above are ok, I dare say the 118mm bb (assuming it is the right octalink, for the right bb shell size) is likely to work just fine, especially if the 121mm one is 1.5mm longer than the old one each side (i.e. the 3mm extension is symmetric, which you can easily establish).

On the other hand, as I said earlier if you are going to get a new chainset then you might want to wait until then because that chainset might well need a totally different bb.

Good luck!

 

[potsy]

Thanks for the above advice, and yes you did say it should be a 121mm,I mistakenly believed the Spec from the Spesh website would be correct,lesson learned.

I'll send it back and put the money towards the crankset instead which takes a Hollowtech BB.
Annoyingly the one I should have bought is out of stock so can't just ask for a replacement anyway.
Still,it's given me a bit of practice for when I do change it all over.
Might as well run this crankset and chain through the winter now,then change it all in March/April time

 

[potsy]

*UPDATE*

Nearly 3 years later I finally got around to buying and fitting the new crankset, went for a Sora triple with Tiagra H2 bottom bracket, I don't like to rush into these decisions
All fitted but needs a test ride once the rain stops, hopefully my main commuter bike will then be back up and running in time for the rest of the summer

 

[Blue Hills]

This must be a record for updating/feedbacking on your own question

But well done - it's the polite/nice thing to do after you've asked for advice - and may of course help others.