ErichM

So a couple of weeks ago I bought a Madone 5.1 with a 6703 crankset. Since I got it there has always been some noise in the middle ring (39t) but now it has gotten really bad. It is kind of a crunchy grindy noise. The chain is clean and oiled and it doesn't do it on the 30 or the 52 rings.

When the chain is on the middle ring the chain is dead center in the derailleur. Trim doesn't affect the noise. The noise exists on every rear sprocket and doesn't change.

I took it to the LBS I bought it at and they basically accused me of cross chaining and said that the FD was fine, even after I explained it occurred in every sprocket.

I'd like to have some ideas before I bring the bike back to them. It is kind of a crunchy/grindy noise. It *could* be that when the bike flexes the chain is swinging a bit and hitting the derailleur but like I said it looks fine when I get off the bike and look at it.

Has anyone run into this issue? Should I just take it to another bike shop?

If it is normal for the middle ring on the 6703 to make some noise I guess I can live with it. Would a 6700 52/39 be less noisy?

Thanks in advance.

bijan

Try to figure out where the noise is coming from. You say it's dead center in the derailleur cage. So you're saying it's not rubbing on the inside or the outside edges of the cage? Is it rubbing on the bottom then? If it's not rubbing on the cage at all where is the noise coming from?

If it's rubbing on the bottom then adjust the height/angle of the derailleur...

Also as it keeps rubbing the more it's permanently deforming the cage...

ErichM

It isn't rubbing on the bottom either. The problem is it doesn't really make the noise when you turn the cranks with your hand. So I'm having a hard time figuring out exactly what is making the noise. I guess it is possible it isn't even coming from the front. If it was an issue with the back though wouldn't it do it on the small and big rings as well?

The only thing I can think of is that it is rubbing as I pedal from the flex. In which case I have no idea how to prevent that and I will just have to live with it.

I think I'll take it to another shop tomorrow and see what they have to say. I don't really like the one I bought the bike at.

ErichM

You know it sounded like it was coming from the chain ring but perhaps the sound was coming from the rear. I think I'll investigate the RD adjustments tomorrow.

cbfight

The solution would be a trim function for the front derailleur allowing for micro adjustments within the same ring. What kind of shifters are you running?

ErichM

They are Ultegra shifters. Trim doesn't affect the problem and the sound occurs at every sprocket.

I perhaps am looking in the wrong spot for the noise. Perhaps it is the rear derailleur. I would think the issue would exist on the small and large ring as well though? Or is it possible that the RD is out of adjustment and it is only noticeable on the middle ring?

It seems to shift fine.

cbfight

The deraiilleurs can be out of adjustment and still shift acceptably, especially the rear. I personally do this by ear so it's difficult for me to diagnose this over the internet. In general, I listen for a more metallic relatively higher pitched strike sound for front derailleur rub, and a lower pitch rumble that's higher than the baseline I get by playing the cable for the rear derailleur.

I would check:
-Front Der. alignment (chain centered within the caging?)
-Front Der. limits (make sure you account for trim)
-Rear Der limits (Jockey Pulley's aligned?)
-Cable Tension (Just enough to shift through the gears crisply and concisely with no stuttering/lag)

And something I rarely encounter is frame flex causing the drive side crank arm to actually rub the outside of the front der. This is hard to diagnose off the bike but sounds like a light pinging sound every revolution.

I reread your original post and I wonder if the noise you're hearing is simply associated with wear-in. If you typically ride in the middle ring then this wouldn't apply, but if you, in the past, used the first and third rings considerably, it's possible the middle ring's teeth are simply still meshing in with your chain wear level. Long shot though.

ErichM

Thanks for the info! I really appreciate it.
I readjusted the front derailleur a couple days ago and really think it is adjusted very well.

I have been neglecting the rear derailleur and will spend some time making sure it is adjusted properly.

I was thinking it may be from the frame flex like you mentioned, but you say that sounds more like a light pinging. This is more like chain noise than a ping. So I guess I can probably rule out any issue with the FD at this point. I will turn my attention to the RD then. If it still makes the noise I will just put more miles on it and see if perhaps it was a breaking in issue of some sort.

Thanks again!

bijan

If no amount of trimming will fix the problem (as you said in another post) and the noise occurs in every gear then it probably isn't rubbing on the sides of the cage, as there should be at least one gear and cage position that should eliminate the noise.

It is either rubbing on the bottom or some weird angle. Again the fact that it happens in all gears suggests it might not be flex (as that should happen more on the smaller cogs).

Maybe it is the tension from the chain actually driving the wheel, that is pulling the chain taut causing it to rub.

In any case if you bought the bike from them the bike shop should fix it.

If you want to figure it out yourself, then try shifting into the smallest cog in the rear (highest gear), and then turning the crank by hand. If that by itself doesn't do it, have someone else presses down on the rear break gently (or just adjust the breaks that way). Maybe that'll put enough drag on it for you to hear (and see) the rubbing while off the bike.

Also if it was a problem from the rear I think it would affect shifting.

bijan

Again if it is the front derailleur, then you will have to adjust the height/angle, which sucks a bit because you will have to disconnect the cable, then reconnect it once you chain the height and then maybe re-adjust the limit screws. Could end up with a lot of trial and error to get everything working properly. But it should be relatively easy to get it in a state where the middle chainring won't make any noise when used with one (or more cogs), where you can definitely know that the front-derailleur adjustment was at fault.

Also looking at the trek website:
https://www.trekbikes.com/us/en/bikes...done/madone51/

Looks like your bike comes with a double crankset by default. I don't know if the triple is a standard option. So it's possible that the bike shop tossed on the triple without properly accounting for the difference in chainline (the distance from the bottom bracket to the chainrings). Although that should be resolvable by changing the tension, that adjustment/trimming would prevent shifting up or down from the middle chainring (with indexed shifters).

cbfight

Also I don't want to pull the "you may want to look into another LBS" card, but if you purchased a Madone from them, they should be more receptive to your problems. It sounded like they just dismissed you and your problem as operator error without investigation. If you want to do this yourself as a teachable moment, that's fine, but like bijan said, the LBS you bought the bike from should be the ones dealing with this, not you.

bijan

My bad looks like it's also available as a triple:
https://trekbicyclesuperstore.com/pro...riple-2972.htm

Anyways it's a really nice bike, so get the bike shop to fix it. If it's just a few weeks old and you didn't get into any accidents, abuse it, etc. Then I would expect them to do absolutely anything to fix it

desertdork

How close are the inner ring's teeth to the bottom edge of the inner plate of the FD cage when the chain is on the middle ring?

ErichM

I would like to do 99.9%-100% of the work on my bike in the future. I don't think I'm quite there yet but I am learning. I really don't mind doing the adjustments so I can learn what to do. As it turns out the investigation may be harder than the correction will be!

ErichM

That's the WSD you posted a link to. The 5.1 is available as a triple. A lot of dealers are out of 2010 models. I got one of the last 5.1s in my size in my area it looks like, based on other dealer's inventories online.

I was talking to a guy at a different shop and he said the demand for bikes was way higher than they were anticipating and they didn't get nearly enough bikes in stock this season.

Phil_gretz

The thing that's primarily changing between the middle ring and its large and small neighbors is the RD cage angle in response to the change in chain slack.

Maybe the B-screw adjustment must be looked at for your Ultegra RD? Look at the clearance between the upper pulley wheel and the largest cog when you're in the smallest chainring. Is it according to the Shimano spec (check your derailleur instructions)? Is the space too large?

Next, go to the middle chain ring and look at the cage angle. As you pedal the crank forward and backward with your hand, try to listen closely to the chain as it moves between the pulley and the rear cog(s). Change cog in the rear - does the sound change?

This might be your issue....

PG

Bekologist

call me a cynic, but i am not impressed with the new shimano road cranks. our shop is strongly behind the compact crank vs triples, so I haven't had a chance to closely look at a 6703 or a 7903 but the design at the tech docs shows a total abberation of chainring assembly on what should be a simple and straightforward chainring/bolt assembly. the new ultegra triple in the tech docs looks like an 80's mountain crank and thats depressing.

shimano part # Y-1LK 98020.

as to the OPs grinding noise despite the ostensibly correct derailleur placement and adjustement, i vote the crankset itself is funky business.

ErichM

I wanted a compact. There were none to be found.

I plan on getting stronger and getting into racing, so I'll likely at some point switch to a full double. Is the 39T ring on a full double crankset significantly different than the 39T on a triple? Other than the ramps and pins? Or is it the ramps and pins that are perhaps causing the noise?

Bekologist

look at the tech docs of your crank. shimano is no connecting the inner ring to the middle, each ring no longer bolts separately to the spider. but its light(er)!!

difficult to say what the problem is if the obvious derailleur adjustements and alignments are fine..... removing, regreasing and retorquing to spec the entire BB and chainring assemblies is another step in potentially fixing issues of hard to pin down crank noise.

is the chain installed correctly?

CACycling

When we first purchased my wife's new bike, she had a lot of trouble shifting with the FD. Took it back to the shop a few times but it was never resolved. Finally, took the bike and my wife to the shop. Explained the problem, they adjusted and said it was good. She rode it around the block, saw it wasn't fixed and we brought it back in. We went through this cycle several more times until they finally figured we weren't leaving till we were happy. They got serious about correcting the problem and finally determined the FD had an issue. They replaced it and it has been fine since.

Point is, take it back and don't leave till it is right.

ErichM

Well after looking at it today it seems like the sound is just coming from the chain on the ring. I guess it will either "break-in" or be with me forever.

This may be a total noob question (which is okay because I'm new to bike mechanics)... If I wanted to remove the granny ring and put a short cage front derailleur on the front, can I replace the 39T ring with a 39T from a double crank? Since I assume the 39T from a 53/39 doesn't have all the ramps and what have you. I'd hate to have to buy a whole new crankset. I see this https://www.amazon.com/Shimano-Ultegr...4081831&sr=1-8 on Amazon and wonder if it would make sense to use it instead of the 39T I have on there right now? Or is it the exact same ring?

I figure I'd keep the 52T as the big ring, since I don't think it would matter enough to change to a 53...

I wasn't planning on making this change right now, but if I could do it for cheaper than buying a whole new crankset and maybe it would rid me of the noise I'm currently experiencing.

cbfight

Sure you can do that. You don't even need to change the front derailleur. Just make sure you set the low limit stop on the front derailleur so that it prevents the cage from derailling the chain at low cable tension.

It's less than ideal since the chainline won't be as centered as it could be, but it'll run for however long it takes you to do a proper upgrade. When you do get around to upgrading, you'll probably want to replace the chain and cassette anyway, so any "damage" you do (if any, which I doubt) from running in a ghetto standard double will be gone.

Since the chainline isn't actually moving at all your chain noise will likely persist.

ErichM

So the chain line won't be centered because of the bottom bracket correct? But the 6700 group only lists one bottom bracket for both double and triple? And the Madone has a oversized bottom bracket. That was an area I was unclear on in regards to what I would need to do with the BB. I guess I'd just like the shorter FD to avoid as much rubbing as I can... They are pretty cheap on-line anyway.

I guess I don't mind spending a few dollars on the change. I would just hate to spend $270 to replace a crankset when I have 52/39 rings already anyway.

cbfight

You have external bottom bracket cups which don't affect the chainline much. What affects the chainline is the construction of the crank spider in triple configuration versus double configuration. Everything is pushed outward a little bit in the triple to accommodate a 3rd ring.

ErichM

Gotcha, thanks for the info! Really appreciate the help.