Chainset replacement compatability

[foxyrider]

So i'm looking for a new chainset for my gravel/cx/touring bike, it was previously running a Campag Super Record 50/36 which self destructed. Whilst i actually have a spare for a like for like swap (it was 'cheap' at the time okay) i'm thinking of dialing things back to metal cranks and an easier / cheaper fitting/bearing arrangement.

My requirements are 50/36 or 34, 172.5 suitable for 11 speed with a budget of up to £200 - there are buckets of alternatives out there and i'm a bit out of touch with compatability hence this post.

Front runners are Shimano GRX - will that work with road shifters? Shimano 105 obviously will as will Campag Potenza, i'm sure there are a bunch of others from SRAM etc.

I throw it out to you all, what do you suggest?

PS: shifters are Chorus 11, rear mech is Centaur 11 with 10sp Shimano cassette and 11sp KMC chain which all works fine although i think in theory at least i could use 11sp Shimano cassette.

[rareposter]

My requirements are 50/36 or 34, 172.5 suitable for 11 speed with a budget of up to £200 - there are buckets of alternatives out there and i'm a bit out of touch with compatability hence this post.

Front runners are Shimano GRX - will that work with road shifters? Shimano 105 obviously will as will Campag Potenza, i'm sure there are a bunch of others from SRAM etc.

I throw it out to you all, what do you suggest?

PS: shifters are Chorus 11, rear mech is Centaur 11 with 10sp Shimano cassette and 11sp KMC chain which all works fine although i think in theory at least i could use 11sp Shimano cassette.

GRX chainset is either 46/30 or 48/31 so not a match for your 50/36 or 50/34 requirement.

GRX tends to need its own front mech cos the GRX chainset sits a bit further outboard than a road chainset and I'm not sure how nicely that'll play with a Campag shifter.

Normal road chainset combination is 52/36 (semi-compact) or 50/34 (compact) so a compact 105 chainset would do the job.

[Brucey]

.... previously running a Campag Super Record 50/36 which self destructed.....

what failed, exactly?

FWIW GRX uses a chainline that is 2.5mm wider than most road transmissions. I believe it should be possible to reduce this to ~1.5mm by careful choice of BB cups, but I have never done this myself.

[foxyrider]

.... previously running a Campag Super Record 50/36 which self destructed.....

what failed, exactly?

It was a massive chainring bolt failure, the result of which was a broken inner chainring (snapped clean through!) and damage to the carbon spider. It can probably be resurected but i've lost confidence in it and at @ £500 a pop...

[Brucey]

so what actually broke, in what order, and how do you know?

[foxyrider]

so what actually broke, in what order, and how do you know?

As far as i can tell it was chainring bolts first (nothing to check as they fired off into who knows where), one bolt left holding things together, guess chainring moved sideways but being held by the remaining bolt it buckled and snapped. The big ring remained in place and undamaged. The spider at one bolt mounting point has lost a chunk of CF, not sure how. Whilst it was on a slight rise, nothing was under particular stress, i was seated and in a low gear, i stopped as quickly as i could when alerted by the loud bang that something was amiss.

[Cyclothesist]

Most odd and disconcerting! Could it be that you lost the chainring bolts one by one gradually over time but didn't notice until the one or two left gave up the ghost under the strain?

[foxyrider]

Most odd and disconcerting! Could it be that you lost the chainring bolts one by one gradually over time but didn't notice until the one or two left gave up the ghost under the strain?

If they did it was over a thirty minute ride! The whole drive train had been rebuilt a month prior and run trouble free for some 1000km until the point of failure.

[Cyclothesist]

It may well be that chainring bolts were lost during that 1000km after the rebuild until the last remaining one spectacularly gave up revealing the issue. Unless you were specifically looking it would be easy to miss. It's happened to others (lots on line e.g https://bicycles.stackexchange.com/ques ... -chainring).
I suggest that's more likely than all of them suddenly deciding to simultaneously snap or unscrew.

[Brucey]

modern chainsets often use just four chainring bolts and this is barely enough. IME 1000km is a distance that could be covered whilst the chainring bolts were merrily backing out. I learned long ago that chainring bolts can back out, or loosen. Even so, I am still not quite immune to being caught out by the little blighters. They need the threads to be well-greased and they need to be surprisingly tightly done up if they are not to loosen. Even then any new installation can still loosen; they can be tricksy little beggars, no doubt about it. I count myself lucky that I have not had more in the way of related breakages. Al bolts simply don't cut it here; steel or stainless steel would be the materials of choice; I have broken chainring bolts made with brass male parts.

[foxyrider]

It may well be that chainring bolts were lost during that 1000km after the rebuild until the last remaining one spectacularly gave up revealing the issue. Unless you were specifically looking it would be easy to miss. It's happened to others (lots on line e.g https://bicycles.stackexchange.com/ques ... -chainring).
I suggest that's more likely than all of them suddenly deciding to simultaneously snap or unscrew.

After having lost a bolt previously on this chainset, its checked at least weekly, as i was setting off on a ten day tour everything had been checked and tightened as needed just 2 days prior.

But that was then (June), this is now, i need to get the bike running again at reasonable cost and its looking like 105 is the pick unless someone comes up with an alternative?

[Cyclothesist]

Thanks for the reply. It's a mystery for sure. - ?? sabotage??

105 is good. Doesn't suffer from debonding issues unlike the tiers above.

[AndyK]

Dragging it back to the question the OP actually asked...
105 is good. Praxis Works Alba X is good and would also be compatible. Factoring in the cost of the Praxis M30 bottom bracket (and the installation tool), brings the price to somewhere around your £200 mark.
The FSA Gossamer Pro chainset would also be OK - again, factoring in a new FSA MegaExo bottom bracket would bring it well within your budget.
Both are available in 50/34 and 52/36 options with 172.5mm crank arms.

Re. chainring bolts: this one of two places on a bike where I always recommend using threadlock fluid. (The other is on mudguard eyelet bolts if they haven't been provided with a Nyloc nut.)

[Brucey]

105 has always represented some of the best vfm going, and I don't think the current 105 chainset is any exception to this. Obviously the likes of sram , FSA and Miche will offer something which is broadly similar, but unless it is a special offer of some kind, it is unlikely to be better vfm. The shimano BB is basically OK but it is not difficult to greatly improve it, either.

[Cyclothesist]

105 has always represented some of the best vfm going, and I don't think the current 105 chainset is any exception to this. Obviously the likes of sram , FSA and Miche will offer something which is broadly similar, but unless it is a special offer of some kind, it is unlikely to be better vfm. The shimano BB is basically OK but it is not difficult to greatly improve it, either.

Combine it with the Ultegra level BB R60 and you've got a smart durable chainset. Even without Brucey's improvements the BB R60 outlasts most others.