(also posted on Road forum)

I'm 6'6 and 245 and invested in a 64cm 08' Madone 5.1 (with the Shimano 105 11-25 double cassette)last August. Love the bike but have had a major issue and wanted this groups thoughts.
Whenever the largest of the two crank sprockets is engaged with the 4 largest sprockets on the cassette, I get a grinding noise.
My local LBS has bent over backwards trying to resolve. They have adjusted and realligned it on countless occasions, reinstalled the brackets with differant forms of lubricant. All providing short term fixes. Just yesterday, they replaced the frame (courtesy of Trek) with 64" CM 09' Madone 5.5 frame. The aforementioned resolution steps were all based on the shops consultation with Trek.
Here's the kicker....i rode away with the newly framed bike (also,the Shimano components were reinstalled & Cleaned) and the grinding noise was as severe as ever!
My next step is to have the mechanic ride beside me to see if he can visually/audibly determine what's up.
Would anyone have any thoughts as to what the issue might be?

Thanks in advance!

Let me guess, this is a "compact" crankset and not a standard crankset. Am I right?

What you are doing is called cross-chaining. Largest-to-largest and smallest-to-smallest is hard on the chain and produces a lot of wear. It also inevitably produces rattle or other noises either from hitting components like the front derailleur cage or from the chain itself. The solution is not to cross-chain.

Unfortunately, with a compact crank that just about everyone wants to sell you in preference to a triple crank, the wide front gearing practically demands that you use the entire range of the cassette for both front gears.

That said, however, with everything properly adjusted you should get audible complaining only from the big-big and maybe big-almost as big combos. That it happens on four rear sprockets tells me that either something is very wrong or - more likely - that it isn't adjusted properly.

Is there another bike shop you could take it to?


Btw, you imply that the mechanic doesn't see .. err .. hear the problem on the stand. When does it happen?

Haha damn, did they let you keep the old frame, I'll buy it!! but yeah, you're not supposed to ride in that gear, you're stretching the chain beyond what the rear derailer can stretch out to and the pulleys are grinding against the cassette, (or you're hitting the fr derailer cage like DMF said) it sounds horrible but actually pretty common,,, when youre in your largest cassette gears you should always be on your smaller chainring, vice versa,, also it doesn't sound like youre shop is very good, the first thing they should of done is ride your bike, good luck, maybe take a riding lesson

It can be very frustrating when you have a nice new bike with chronic noises and little problems.

However, from you description it is almost definitely a derailleur adjustment problem. Perhaps take the bike to another shop for a second opinion. Tell them exaclty what your problem has been and ask them to get their tallest tech to take it for a spin to help diagnose.

The only other thing I can think of causing it is perhaps the chainline is off... modern bottom brakets usually have spacers to centre the spindle and align the cranks in the frame - perhaps it was assembled wrong at the factory and they got it wrong again when they reassembled with the new frame.

Keep in mind, though, that on a 10 speed bike, using the large chainring and large cog (or second or third largest cogs) is not good for the drivetrain. When I built bikes I would always try to set the chain so it rubs a bit during cross-chaining.

Also: Are you aware that Shimano STI shifters have a 'half click' or 'trim' adjustment on the front shifter? You might be able to get the derailleur to move slightly over if that is what is rubbing... provided the front derailleur is adjusted properly to take advantage of that feature.

Good luck!

I'd try and find another shop to take a second look, seems like they should've nailed down the problem by now. Although it would seem like some kind of "user error" if they've replaced and cleaned every thing

We had a bunch of trouble with the FD on my wife's Fuji when we bought it. The mechanic would get it adjusted on the stand but in the real world, my wife couldn't get the chain onto the big ring. I'd adjust it during the ride to get it to shift and then she'd get the grinding. Took it in several times but always came back with same issue.

One day we were on a ride and I could see my wife was frustrated. We were only a few miles from the LBS so we rode over there. They adjusted, she test rode, not fixed. They readjusted, she test rode, still not fixed. This went on for a while and my wife was ready to accept that it was operator error but I encouraged her that it wasn't her it was a mechanical issue.

After many more rounds of this, they finally replaced the FD and it has worked perfectly every since. Never give up!

Boy, I can't imagine the shop would have overlooked something like derailleur adjustment.

I think it's the fact he's a big guy and the Madone is a dainty frame. I'm betting it's torque load twisting the stays. Prolly why Trek put him in an upgraded frame since they thought that it was stiffer

"(also posted on Road forum)"
Dang, so thats where my reply went??

Cross chaining,as DMF said... how could the bike shop not known? Even newbie like me know we should never do that, however, Trek still went ahead and tried to satisfy their customers,can't beat that.

Cross chaining might account for the problem with the 2 first or last cassette gears, depending which chain ring you'r using, but with 4 cassette gears there is a mechanical problem.

The OP may not be using the trim on his front shifter correctly. Yes, it could be an improperly set up front derailer.

Maybe nothing is wrong. Bikes are not silent machines

Trek is one of the only bicycle companies that don't have weight limits on there frames. As far as not stiff enough the 2008 Madone's (5 and up) are probably right up there with the stiffest on the market. I think it sounds like cross chaining, but you would think any bike shop would know this, and one of their first suggestions would be not to do it.