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Got a 2019 BMC teammachine with nearly full 105 groupset, nearly fell off the bike at 40 kph when it skipped cassette cogs in the highest gear 50 x 11.
Derailleur alignment looks fine to me, what could be wrong here?
The gears aren't setup properly. Take it back to the shop and get them to sort it.
Chinese gears?
Just joking... 😁
Chain too long?
A combination of poorly set up gears and mashing the gears at a low cadence
Pictures would help, but possibly insufficient chain wrap. Is the top jockey wheel a long way from the sprocket? Fiddle with the B screw, (or take it back to the shop as suggested)
Would take it back but the bike was shipped here.
Chain wrap looked fine too, can post pictures tomorrow!
I'll bet the high limit screw is about 1/2 turn too far in so the 11t isn't quite engaging properly
I’d have said b screw adjustments. I have also once seen an issue of manufacturer’s chain grease leading to slippage, although that was on a Rohloff. It was fine after being degreased and lubed.
Another good suggestion. Also, bent tooth, chain damage (although that would probably affect multiple gears) bent derailleur hanger, kink in cable near an outer ferrule, final cable loop a bit short, cable wrong side of clamp.
That's all I have, could be loads of stuff.
Rims not deep enough?
Or maybe shoes too flexible?
Sorry, couldn’t resist...
Def needs cheap new carbon wheels!
New? Almost always a slightly, not visibly bent hanger.
Hmm, maybe best to leave it with a shop and send the bill to the seller?
Send the bill to the seller?
Best of luck with that.
yohandsome
Hmm, maybe best to leave it with a shop and send the bill to the seller?
The gears quite likely worked perfectly fine before it was dispatched.
The odds are the bike box was transported flat and had something heavy on it in transit, or it was forcibly squeezed into a tight spot in the van, and the derailleur hanger got bent then.
Ideally a derailleur should be removed or otherwise protected when shipping.
Who knows.
Either buy from a local shop you can rely on to help out with post-sales problems, or acquire the skills to deal with them yourself. Assistance-by-internet-concensus is a poor third option.
Frankly, setting up and adjusting gears should be one of the very first things you learn, but having seen how many folk can't even get a tyre on and off a rim, maybe that's #1.
I just don't want to waste time since i don't have a hanger alignment tool. It's fine, i'll take it to my LBS which this thread has convinced me is the way to go.
That’s probably the easiest option.
Personally I’d have a quick go at resetting it up myself.
I’d undo the rear cable from the derailleur and check the upper / lower limit screws initially by hand, to check the chain reaches both fine. It maybe it’s not quite able to get fully engaged in the highest gear - hence your skipping issue.
Once that’s done I’d let the derailleur go into the highest gear and then by hand pull the cable fairly tight through it (making sure the shifter is also in the highest gear and the the adjuster (probably online) is wound one turn from fully inwards).
At that point I’d then cycle through the gears in the the stand and see how the gears are. I’d then fine tune the gears with the inline adjuster until they’re perfect. If you can’t get them perfect either the b screw needs some adjustment so the top jockey wheel is close enough (but not touching) the cassette - or the derailleur hanger isn’t 100% straight.
That will take about 10 mins. If that doesn’t fix it then I’d consider the bike shop.
You can make a rear mech alignment tool with a few bits and bobs. The proper tool is easier and faster, but it's what I have done in the past.
Lots of interesting ideas but epicyclo's psychic powers win the thread for me.
Did you not opt for the HD aero rear 105 mech for big power and max aero ? 🙂
So it skipped up from the 11 tooth cog to the 12 or 13 or whatever the next one up is?
Try adjusting the cable by turning it 1/4 of a turn. How well does the chain run when you have the bike stationary and change up and down through the gears?
Bet you are wishing you now got that fixed gear bike...
@joebristol yep that makes sense - talked to the seller, first they said skipping cogs without skipping gears simply was impossible, very German.
He conceded that it could be the h limit screw or derailleur cable being too tight, and if not that a bent hanger. I loosened the h limit screw 1/2 turn and looks like the derailleur moved a tiny bit, also loosened the cable slightly. Seems to be fine now, but will do some more mashing later to confirm - at least I'll be clipped in :S
@kerley the thought did occur to me, if the chain falls off at some point i might need to convert to ss ;p
I'd be more worried about the snapping forks than the skipping gears
(I assume/hope yours isn't one of the affected models but useful to know, and not having a downer on BMC as having hired them in Tenerife I nearly bought one).
I’d be more worried about the snapping forks than the skipping gears
Given that recall was 3 months ago surely the OP's bike would have been checked before he bought it?
I've no idea where, when or how the OP bought his bike - new? old stock? used? ebay? Evans aka Sports Direct were a big BMC vendor, would you trust them? (he mentions a German seller and there's comments that suggest prior threads which I may have missed). Old story now but the first my local Evans knew about GT going bust was when I told them why I was stockpiling spares. Like I said I hope the OP is unaffected but if I was a Team Machine owner I'd like to be informed and would be double checking.
Crashtestmonkey Evans are doing recall for BMC forks same as they have done for all other warranty recalls but thank you for your concern. 🙄
Given that recall was 3 months ago surely the OP’s bike would have been checked before he bought it?
It's a logical stretch of imagination sure .... How ever given the wait that two local owners of team machines have had for forks exceeding 3 months I think bikes in boxes will be pretty low on the priority list.
I'd certainly be asking the question and not blindly assuming.
Didn't mention I've got an Alu ALR model, not affected by this!