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Hi all,
Today my friend reversed into a post with my bike on the back of his car, and bent two of my chainrings. I think my driveside crank is damaged too. Everything else appears fine, I have stripped it all down, only got the bottom bracket left to remove.
I have a 2015/2016 (unsure) Rockhopper Sport, with Shimano Acera rear mech (9 speed) Altus front mech, and Specialized Stout chainset. Bottom bracket spindle is square-tapered, 118mm, and has a 73mm bottom bracket shell.
I am struggling to find a replacement chainset.
A guy in Halfords said to get a FC-M3000 (from Tredz - haha!) but not the Octalink. Turns out the one on Tredz is only Octalink. I found the FC-M371 but it seems that is for a 113mm bottom bracket? Looking at the 2016-2017 Shimano Products compatibility information PDF all I can see with respect to 118mm BB is Octalink related.
I could however replace my bottom bracket, but i'm concerned about mmessing up my chainline.
I'm at a complete loss on what components to get - any help would be hugely appreciated.
Check your cranks are damaged, if not, just get chainrings? (or straighten yours)?
Not unusual for badged OEM stuff like this to have an incompatability issue like this IME.
Worst case scenario, you'll need a new BB.
If you are buying a new chainset, then cost of a new BB is bobbins or even included. You do not have to stick with a square taper - octalink would work, or outboard.
If you are keen to stay square taper, then there's a good choice at SJS cycles.
If not then a deore triple (FC-M590) for 9speed will be about £60 including an external bottom bracket. That's what I would go for.
I'm happy to replace my bottom bracket, as the bike was second hand, and now would be a good time... but if I stray from 118mm won't this affect my chainline?
I seem very limited in 118mm square taper bottom bracket options.
Would Octalink or an outboard BB be a straight swap? I have read mixed things.
Please excuse my ignorance - new to changing anything driveline related! Thanks very much for your help.
What's the current chainline?
A 9sp external bb triple will be 50mm
Each square taper or octalink chainset needs a specific BB length so
I found the FC-M371 but it seems that is for a 113mm bottom bracket
Means you buy a 113mm BB.
Unless you really want to stay with a square taper BB, just buy one of these http://www.chainreactioncycles.com/shimano-deore-m590-9-speed-triple-chainset/rp-prod40496 which comes with an external BB.
If your chainrings are bent the new ones may not work with an old chain but you could replace the whole drivetrain with this http://www.ebay.co.uk/itm/Shimano-Deore-Bike-Crank-Chain-Cassette-Bundles-FCM590-44T-48T-Black-/311778711777?var=&hash=item8e2e7be814 for £85
Thank you so much for all of your replies. I couldn't see the wood for the trees before 😯
So, I will replace my bottom bracket. I got a crank puller and shamanic 20 spline socket today, so I'm able to remove the BB now. At least I will give myself more choice in the future with a different BB.
If I get a different BB, is Octalink or an external a direct swap? If so, If I drop to 113mm should I be concerned about chainline? I guess that's only 2.5mm shorter each side.
I don't know what my current chainline is, I'd have to measure it tomorrow.
If I get a different BB, is Octalink or an external a direct swap?
Don't bother with Octalink. It'll be the same price as HT2. Just get that Deore HT2 set from CRC. It'll be a straight swap, trust me.....
🙂
EDIT: Just seen your post PeterPoddy, thanks, based on the findings below o think you're spot on. Will do nicely with my new NanoX pedals 🙂
Centre of frame to centre of middle ring teeth = approx 50 mm (refitted drive side crankset almost fully tight)
Bottom bracket in there currently is a VP-BC73T 73L 118mm and feels a bit grindy for want of a better word but it hasn't had much use.
Cranks are 175mm and straight but aesthetically damaged.
Chainring PCD 125mm.
Bottom bracket in there currently is a VP-BC73T 73L 118mm and feels a bit grindy for want of a better word but it hasn't had much use.Cranks are 175mm and straight but aesthetically damaged.
Chainring PCD 125mm.
The only thing that matters there is crank length, just order the same size 🙂
Ordered, thanks very much, will update with how I get on. Should arrive wednesday.