# Madone 2011 6 series loose fit seat cap



## loetleen (Aug 11, 2010)

My new Madone 2011 6.5 was supplied with a seat cap which has a rather loose fit. As you can see in the picture, tightening the bolt with 6 Nm results in a rather odd compressed cut-out with even some deformation of the carbon at the top right of the cut-out. 
Does anybody have a similar experience?


----------



## Tlaloc (May 12, 2005)

*Cracked Seat Mast?*

Is that a crack in your seat mast below and to the right of the clamp? It looks like someone over-tightened your clamp and crushed the seat mast. It's hard to tell from the picture.


----------



## loetleen (Aug 11, 2010)

Tlaloc said:


> Is that a crack in your seat mast below and to the right of the clamp? It looks like someone over-tightened your clamp and crushed the seat mast. It's hard to tell from the picture.


That is just a bit of masking tape to keep track of the seat cap position. Meanwhile it has been replaced by a fine line of waterproof ink.


----------



## Trek2.3 (Sep 13, 2009)

Look in your spare parts bin for a rubber shim from one of your headlight or tail light kits. Slip it inside the seat mast cap and tighten. I'm sure that you won't have to go beyond 6nm.

Trek's QC on seat mast caps is crap. I've got "120" mm caps that measure 120, 125 and 130, although they were all packaged as 120 mm products.


----------



## loetleen (Aug 11, 2010)

Trek2.3 said:


> Look in your spare parts bin for a rubber shim from one of your headlight or tail light kits. Slip it inside the seat mast cap and tighten. I'm sure that you won't have to go beyond 6mn.
> 
> Trek's QC on seat mast caps is crap. I've got "120" mm caps that measure 120, 125 and 130, although they were all packaged as 120 mm products.


The seat cap is perfectly keeping its set height when tightened at 6Nm (may be even less). That is not the problem. My concern is more about the rather large difference between the inside diameter of the seat cap and the diameter of the seat mast. There is close to 1 mm between the two which is causing the excessive compression of the seat cap as you can see in the picture. This could of course be solved with some sort of thin foil around the seat mast but one would expect this to be designed as a nice snug fit in the first place.
My question: does anybody with the new circular seat cap have the same experience?
The part number of the seat cap is 413478, Bontrager Trek Madone seat cap. And more concerning: 'made in China' where the 6.5 frame itself is Wisconsin built.


----------



## Trek2.3 (Sep 13, 2009)

loetleen said:


> My concern is more about the rather large difference between the inside diameter of the seat cap and the diameter of the seat mast. There is close to 1 mm between the two... .


1mm isn't much "tolerence" on a non-precision part. Remember that it does have to move up and down easily. I put grease on my seat mast and don't have this problem (yet?). A coating of grease might fill up a single mm of space.


----------



## rubbersoul (Mar 1, 2010)

notice the stress riser on the right hand side?


----------



## loetleen (Aug 11, 2010)

Trek2.3 said:


> 1mm isn't much "tolerence" on a non-precision part. Remember that it does have to move up and down easily. I put grease on my seat mast and don't have this problem (yet?). A coating of grease might fill up a single mm of space.


I did of course apply a liberal coat of Tacx carbon assembly compound to prevent the carbon seat cap from slipping down over the carbon seat mast. But that of course doesn't keep the seat cap from being squeezed together as grease would not either. Grease on these carbon parts would make it slip down no matter how tight the bolt is turned.


----------



## loetleen (Aug 11, 2010)

rubbersoul said:


> notice the stress riser on the right hand side?


top right hand side of the gap is indeed showing a stress deformation of the carbon composite material. That is exactly my concern and makes me wonder whether anybody else has the same experience.


----------



## jhendrix731 (Nov 3, 2010)

I've got a 2010 6.9, same frame as the 2011 6.5, and ive got the identical stress formation on my seat cap. I wouldn't be concerned but if it is an issue it should be covered by warranty.


----------



## loetleen (Aug 11, 2010)

jhendrix731 said:


> I've got a 2010 6.9, same frame as the 2011 6.5, and ive got the identical stress formation on my seat cap. I wouldn't be concerned but if it is an issue it should be covered by warranty.


Thanks for telling me.
My LBS checked with the TREK representative here in the Netherlands and they confirmed that these particular seat caps have all the same inner diameter. He also confirmed that the stress mark on the seat cap wasn't caused by exceeding maximum torque and shouldn't worry me. The latter is in particular important for possible future warranty claims. Especially since this frame is a replacement under warranty for a 2009 Madone 6 series frame that developed some tiny cracks at the base of the seatmast.


----------



## icsloppl (Aug 25, 2009)

loetleen said:


> Thanks for telling me.
> My LBS checked with the TREK representative here in the Netherlands and they confirmed that these particular seat caps have all the same inner diameter. He also confirmed that the stress mark on the seat cap wasn't caused by exceeding maximum torque and shouldn't worry me. The latter is in particular important for possible future warranty claims. Especially since this frame is a replacement under warranty for a 2009 Madone 6 series frame that developed some tiny cracks at the base of the seatmast.


It may not be an issue with crushing the seat mast but it sure as he11 is an issue with the cap.
Note that carbon structures have effectively no strength once they have reached their fatigue limit. This part will break and you will get an unusual surprise when it does.


----------



## tellico climber (Aug 14, 2006)

loetleen said:


> Thanks for telling me.
> My LBS checked with the TREK representative here in the Netherlands and they confirmed that these particular seat caps have all the same inner diameter. He also confirmed that the stress mark on the seat cap wasn't caused by exceeding maximum torque and shouldn't worry me. The latter is in particular important for possible future warranty claims. Especially since this frame is a replacement under warranty for a 2009 Madone 6 series frame that developed some tiny cracks at the base of the seatmast.



I have the exact same stress marks on my 2011 6.5 seat mast also and I am the only one who has ever tightened my seat mast and I am using a torque wrench. I only tightened to 6.5nm which is a little under the max stated on the clamp. I had never noticed them until today after reading this thread and decided to check mine out also. I called my LBS and they said not to worry about it.


----------



## SilverBack14 (Mar 31, 2010)

I have the same stress mark on my seat mast. I pointed this out to the LBS when I picked the bike up. They said it's fine. So far so good.


----------



## kylant (Jul 18, 2009)

I just got my 6 and have the exact same issue.

But I also have something else going on that could be a huge issue. I have noticed that my clamp has actually pinched/indented the mast itself. I set my seat height and torqued to Treks specs using my 1/4" drive torque wrench. I noticed the outer seat mast doing the same as the pics above so decided to remove it and take a look, thats when i discovered the issue with the frame mast. I took it to my LBS today to have a look and they were not sure. They said bring it back on Monday to have the Trek rep look at it. 

I just got this frame, and finished the build on Monday. I haven't even ridden it yet:mad2: 

Anybody else have the issue i have?

please advise

thanks


----------



## jkjas (Mar 26, 2011)

*Same Problem!!!*

I have a 2011 6.2 Madone. Post does not slip but the seatcap is clearly a larger diametre than the seatpost. My concern is that the cap is actually 'hinging' at the clamp as it bends horizontally (gathering the play in the oversize cap. In my seatpost the lacquer is already scored by the leading and trailing edge of the seatcap. My LBS has reported it to Trek Australia - they apparently said it was usual for the seatcap to be a loose fit. I'm not sure I like it though.


----------



## Trek2.3 (Sep 13, 2009)

loetleen said:


> Thanks for telling me.
> My LBS checked with the TREK representative here in the Netherlands and they confirmed that these particular seat caps have all the same inner diameter. He also confirmed that the stress mark on the seat cap wasn't caused by exceeding maximum torque and shouldn't worry me.


*Get it in WRITING.* It it's not in writing, in 3 months it won't have happened.


----------



## Road Hazard (Feb 5, 2011)

2010 Madone 6 here.

I have the same exact stress marks, except on both sides, like a mirror image of yours at both "edges" of the round part of that cutout in the seatmast.

4200 miles and no problems. I always figured that part was built to flex and the crack was the clearcoat.

Incidentally, I have another paint crack on both sides of the fork where the aluminum dropout is bonded to the carbon fork. That one worried me good for a while but after two shops said it was alright, and another couple hundred miles of field testing, I believe there is such a thing as clearcoat/paint cracks that are not structural.


----------



## millman (Mar 7, 2010)

I just picked up my 6.2 yesterday and specifically looked for the pinching. Everything was uniform and no stress. The tech said it was with the older style cap. Also I got the 5 mm offset. What offset was yours ?

Millman


----------



## FSonicSmith (Jan 2, 2003)

I have a 2011 6.7 and my LBS (a Trek Store) tells me that this is a known product defect that Trek is in the process of addressing. My seat mast is cracking. That is the least of my problems. See my separate post.


----------



## swiftbiker1 (Jun 16, 2011)

I have also the same bycicle and I did put some tape to make the tube bigger and tight it to 6Nm. With that solution it looks fixed correclty. Without it was moving and create a scratch on the paint seat mast. 
Without tape even at 7Nm it was still moving !!


----------



## wetPNWbiker (Jun 29, 2011)

*2010 Madone 5.1 seat cap slop*

I also had a loose fitting seat cap on my Madone 5.1. It rattled incessantly. There was at least 1.5 millimeter play fore and aft and a half a millimeter play side to side. No cap cracks that I could see. I tried making up the difference with applying electrical tape to the top of the mast just to cure the rattle, but the cap still sliped over time when riding on rough roads. The fix is a liberal buttering of seat post paste (with the grit) inside the seat cap, then tightening the bolts to spec. My seat cap had no paste inside when it slipped. It seems hard to believe that there should be this kind of play between these two parts since everthing else on bike fits so perfect, but the paste works well, though doesn't completely cure the rattle. I haven't found a commercial source of this paste, just the LBS.


----------



## mfmartinez85 (Dec 2, 2011)

hello! i know this is a old post but i just got a new six series madone from a warranty on a 2009 5 series madone due to the seat mass cap bolts snapping all the time a totally of 8 times ( i lost count after 6). i upraded for a grand. well ive got the same issue as the poster loetlean and jhendrix731 with a crack in the seat cap mass. i wanted to know what has happened since then?? have you had complete failure in the cap itself?? ive owned this bike for two weeks and this is becoming a nightmare! i plan on taking the bike to my LBS and get a full refund on the frame. i cant afford a faliure in a race and injury myself and other riders. im done with TREK

i hope to hear some testimony from any users out there so i can have some ammo when i go into the shop today


----------



## Tlaloc (May 12, 2005)

*Torque Wrench?*

It's likely that all of these problems were caused by over-tightening the bolts. Certainly crushing the seat mast will be attributed to this. Do you own a torque wrench? You should never tighten any bolt on a carbon frame without using one.

One's posts are much more readable when they don't contain incorrect capitalization, punctuation spacing, spelling and vocabulary.

Please post a follow-up describing what happens at your Trek dealer.


----------



## mfmartinez85 (Dec 2, 2011)

Tlaloc said:


> It's likely that all of these problems were caused by over-tightening the bolts. Certainly crushing the seat mast will be attributed to this. Do you own a torque wrench? You should never tighten any bolt on a carbon frame without using one.
> 
> One's posts are much more readable when they don't contain incorrect capitalization, punctuation spacing, spelling and vocabulary.
> 
> Please post a follow-up describing what happens at your Trek dealer.


thanks tlaloc,i apologize for bad grammer. im from the spell check generation.

yes i do have a torque wrench. i bought one when i kept snapping bolts on the '09 seat cap. its a ritchey tourque key set to 5nm. the limit for the new mass is 7 nm. i've done everything right.


----------



## wetPNWbiker (Jun 29, 2011)

*Madone 5 series seat mast cap*

For me, the problem became managable when I excessively 'buttered' the inside of the mast cap with waxy assembly greese that has the grit and tightened the bolts to spec. It still rattles a bit when I hit a rough spot in the road, but it has not slipped down nor have the bolts become loose since I put in the greese. I think these parts (mast and cap) don't match up so well, but its probably hard to manufacture a perfectly fitting cap to a seat mast with little tolerance. I'd ask for a new Bontrager cap before opting out of the whole bike. Maybe you just got a bad cap.


----------



## mfmartinez85 (Dec 2, 2011)

wetPNWbiker said:


> For me, the problem became managable when I excessively 'buttered' the inside of the mast cap with waxy assembly greese that has the grit and tightened the bolts to spec. It still rattles a bit when I hit a rough spot in the road, but it has not slipped down nor have the bolts become loose since I put in the greese. I think these parts (mast and cap) don't match up so well, but its probably hard to manufacture a perfectly fitting cap to a seat mast with little tolerance. I'd ask for a new Bontrager cap before opting out of the whole bike. Maybe you just got a bad cap.


after my problems with my 09 seat cap bolt snapping 8 or 9 times (and im not joking) the option of getting a new cap which they would give me isnt an option. when i got the new frame under warranty i was under the impression that the cap problem was fixed. i wish i would have seen this forum and thread 3 weeks ago and i would have made a different decision since i was given the option to upgrade to a 6 series madone from the 5 series they warranted for $1000.

thanks for all the help everybody has been most helpful. i will post what happens after i get back from the shop. i live in dallas,tx and bought my TREK at richardson bikemart. they have been giving me great service with my issue with the 09 madone seat cap. i hope they continue it when i go in today. ive been very patient and nice about everything.....you catch more flies with honey than vinegar


----------



## mfmartinez85 (Dec 2, 2011)

*new frame!!*

so i took my bike up to my LBS and they wanted to take care of me by replacing my seat cap, they explained to me that the crack isn't a concern but for piece of mind they'll put a new one on. i asked to speak to a manager and i explained to him that i wasn't happy with trek at all and don't feel safe at all on the bike. the owner of the shop comes out and we talk about the issue and my lost faith in TREK. i ask for a refund and he does me one better he swaps out my 2011 6 series madone for a 2011 s-works sl3 tarmac at no charge. im a very happy customer!! rbm took good care of me!

to all the trek owners i wish you the best with your seat cap mass


----------



## early one (Jul 20, 2010)

Here is Trek giving the mast the Bo Jackson test.


----------



## mfmartinez85 (Dec 2, 2011)

Id like to see the results after about 3 000 miles of use on the cap mass


----------



## Tlaloc (May 12, 2005)

mfmartinez85 said:


> Id[sic] like to see the results after about 3[sic]000 miles of use on the cap mass[sic]


What the [email protected]#$%^& ia a "cap mass"? Is it a mast or a cap?


----------

