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forum
Crankset: Standard vs. Compact
I am hoping that someone here can help me with a question I have
When I replaced the crankset when my FSA Omega died I went for the 105 (5800) to match the rest of my groupset. I made the decision (mistake?) of getting a standard rather than compact crankset but now want to change my mind. Is it as simple as changing the chainrings or do I have to buy a whole new crankset?
If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.
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14 comments
Funnily enough I did exactly same as you (replacing fsa omega with 105 5800 but failed to order 50/34). I contacted online retailer & sent it back. Have now ordered correctly along with bbr60 bottom bracket, some grease & a bb tool & i'll swap over later this week.
If you stick with rings you have, i think you'll have to account for chain length & adjust accordingly.
If shop won't have it back i'd cut losses and ebay it & re buy correctly i'm afraid. Good luck.
Unfortunately I did a tour on the bike immediately after fitting it so there is no chance of returning it. I did realise my mistake before fitting it but if I hadn't fitted it I would have missed out on the tour and I did not want to do that.
I have already managed to get hold of the rings for just £39 but wanted to make sure that I can swap them over before potentially spending a rather fruitless afternoon trying to fit them. As opinion seems to be divided on this it looks like I am going to have to give it a go anyway
It'll be fine, as long as they are 4-arm 110 BCD Shimano compatible chain-rings
Not sure why some people were insisting that they were different whilst ignoring the facts, it's not like it's an opinion piece... hey ho.
Edit : Nice price btw.
They are 4-arm original 105 11 speed chain rings so looks like they will fit fine.
Thanks, I was lucky enough to find someone selling them on eBay who had ridden them for 500 miles before changing to Q Rings.
5800 chain rings "BoltCircle110mm" so states Chain Reaction Cycles: http://www.chainreactioncycles.com/mobile/shimano-105-fc5800-11sp-double...
Not an economical replacement for a two chain rings only option. Maybe worth a thought if replacing one only?
If you google replacement rings for the 5800 chainset, the cost of both rings is WAY more than the cost of a whole new chainset with rings.
~€52 for 50/34 on Rose bikes
https://www.rosebikes.com/article/shimano-105-fc-5800-chainring/aid:786501
You will probably be able to get a 39 or maybe 38 tooth inner to fit, but the reason they are classed as compact is because the bcd's are different. Normally 130mm on a standard and 110mm on a compact. On a side note, Stronglight seem to do their own thing.
The BCDs are not different on the 5800, it's 110mm like the other recent Shimano 4-arm chainsets.
I would assume the bolt circle diameter is different for each. If that is the case then it's a new crankset I'm afraid.
The 5800 chainset follows the recent Shimano approach of unified BCD - so compact, mid-compact or standard double will be fine.
Try on the classifieds to see if there's someone looking to swop like for like.
I've just replaced my RS500 chainset with a 5800 105 set. The forged, shaped rings are so expensive you'd be far better off buying a whole new crankset that trying to buy rings for it.
Should be as simple as changing the chainrings and adjusting the chain.