2021 TREK Emonda SLR 7 crank problems

Solarch

New Member
Bought a 2021 TREK Emonda SLR 7 with Shimano Ultegra Di2 for my 18-year old son who is a development athlete. But I was disappointed by the, practically non-existing, clearance between the right crank arm and the chain that has caused the chipping of the crank arm. When the chain is on the big front disc (52 teeth) and on the lower (heaviest) gear (11 teeth) there's barely any space between the crank and the lower part of the chain (there is a 1mm gap when the bike is on the stand but when my son rides the bike and presses hard on the pedals the gap is zero). The seller says that that's the way the bike was when it was unboxed and suggested to use a washer between crank and frame. But is this right? Has anyone had any similar experience? Because other that this setback the bike is beautiful and powerful. If I made this post in the wrong place please let me know. You can also see a relevant video on YouTube at the link below. Thanks.

View: https://www.youtube.com/watch?v=ZW2vcDd61bQ
 

accountantpete

Brexiteer
Hi - that's an inherent problem of the bike design and the crank design so you are doing nothing wrong.

The only solution I can think of is to do what I have to do as standard on my BB30a bottom bracket/Shimano Ultegra Cranks and that is to get some thin shims and place them on the crank spindle between the cranks and the BB cups. This will move the crank arm outwards and stop the interference. You can pop similar shims on the non-drive side to maintain symmetry.

(you need to get shims that match the diameter of the crank spindle - are Ultegra's still 24mm like mine? - this is the kit I use (you need just the shims not the cups)

568788
 
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si_c

Veteran
Location
Wirral
Yeah, unfortunately not a huge amount that can be done there. You have two choices, either shims as mentioned above - this will adjust the Q factor ever so slightly, but I sincerely doubt it would be noticeable. The other choice is to get a rubber boot that covers the end of the crank - they are intended for MTBs but you should be able to get one to fit the ultegra crank.

Personally I'd go for the shim route - a 1mm shim would probably suffice - and then touch up the cranks with some nail varnish to hide the existing marks. My cranks all have similar marks from striking curbs when dropping off the pavement and similar so I'm not overly fussy about the appearance side of things but eliminating that strike. Something like this should be good enough.
 

Ajax Bay

Guru
Location
East Devon

accountantpete

Brexiteer
Yeah, unfortunately not a huge amount that can be done there. You have two choices, either shims as mentioned above - this will adjust the Q factor ever so slightly, but I sincerely doubt it would be noticeable. The other choice is to get a rubber boot that covers the end of the crank - they are intended for MTBs but you should be able to get one to fit the ultegra crank.

Personally I'd go for the shim route - a 1mm shim would probably suffice - and then touch up the cranks with some nail varnish to hide the existing marks. My cranks all have similar marks from striking curbs when dropping off the pavement and similar so I'm not overly fussy about the appearance side of things but eliminating that strike. Something like this should be good enough.
I think those spacers move the hollowtech cups out - same effect though.

PS

I have presumed OP is using Shimano/hollowtech similar to the video.
 

iluvmybike

Über Member
That doesn't look right to me - in years of looking after bikes I have never seen one with clearance as small as that - no way should it touch the crank even when standing up on pedals.
 

Ajax Bay

Guru
Location
East Devon
Tried to find something useful on this:
(From 2012 - so an issue (even) then going to 135 OLN): https://bikerumor.com/2012/11/28/te...spacing-affects-road-bike-chainline-shifting/
" SRAM: I think heel clearance is not really the question, as nothing changed. Heels usually touch the chain stays. The real question should be about the cranks running into the chain because the 11t is further outboard. And yes this is a concern on frames with short chain stays and 135 OLD. "
"FSA: We could very easily add 5mm to our crank spindles and supply them with spacers, but that’s not what people want. They don’t want wider Q factors."
 

si_c

Veteran
Location
Wirral
Definitely need to move the crankset outboard ever so slightly, I've just checked my disc braked road bike - 135mm OLD with Shimano cranks - and there is minimal distance between the chain and the arm, about 3mm or so from the inside edge.

PXL_20210114_142458129.jpg
 
OP
S

Solarch

New Member
Thanks so much for your prompt input guys. I contacted the local dealer and we've set an appointment for Monday as he already had reached out to Trek in Wisconsin asking for help. They sent him a type of "washer" and suggested a methodology to solve this issue. Will keep you posted on this, thanks again.
 

Ajax Bay

Guru
Location
East Devon
You CANNOT be alone (with this issue), unless your son is a 'special case'.
And rather difficult to anticipate. Hope he gets good enough to get on a team who provide his bikes..
 
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OP
S

Solarch

New Member
OK, so here's an update on this issue. The local TREK representative received a proprietary 1mm-thick washer from TREK. He inserted it into the right part of the crank arm and (obviously) we now have a reasonable clearance between the crank arm and the chain, about 2mm. Having ridden the bike for many many kms, the problem of the crank scratching the chain never surfaced again. The question though is why should this happen in the first place and also if by slightly changing the symmetry of the left and right distances of the cranks to the centerline of the bottom bracket, we create another problem.
 

Ajax Bay

Guru
Location
East Devon
The resultant increase in Q factor of this spacer washer insertion is unlikely to have any effect on your son's riding: it's about 0.4%.
Theoretically the wear on the left bearing might increase (?2%) more bending, but since your son is top level for age, you'll be changing the BB well before that shows up.
 
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