frame cracks

Workshop tales, trials and disasters.
Maintenance tips, techniques and myths.
Technical discussion, description and outright lies

frame cracks

Postby mick243 » Wed Mar 20, 2013 12:57 pm

In july 2012, I became the proud new owner of a "Jamis Exile Comp" 29er......

mid august, the BB started making loud graunchy noises and was replaced under warranty.

late august, the frame cracked at the joint between the top tube and the seat tube. this was replaced under warranty, however it took until feb 2013 for them to get another frame and put it all together. (the store and the Jamis agent seem to be very good in the customer service dept - no issues there, very good IMHO)

last week (mid mar 2013) frame found cracked in the same place.


now, I'm rather tall, and not exactly light, but I do come in under their weight limit, and the seatpost has about 1-2cm more travel before it reaches the limit marked on it. I mostly use it for commuting, with the occasional dirt track thrown in (no real MTBíng or off road as such, I take a roadbike to the same places...)

2 frames in 2.5 months of riding - havent even worn out the factory tyres yet. anyone have any suggestions on whats going on?

frame is stickered as being made of "7005 T6 Alloy".

how many other riders of the same model bike out there? I'm hoping that I'm just really unlucky here and have got 2 dodgy frames rather than it being a widespread issue?
mick243
 
Posts: 210
Joined: Wed Mar 20, 2013 10:44 am

by BNA » Wed Mar 20, 2013 4:46 pm

BNA
 

Re: frame cracks

Postby Nobody » Wed Mar 20, 2013 4:46 pm

http://www.jamisbikes.com/usa/thebikes/ ... _spec.html

Obviously keep chasing the warranty. Hopefully this will be the last time. Keep the MTB for MTBing and maybe get a commuter for commuting. If you want a frame that is less likely to let you down, I suggest getting an over-built (for purpose) steel bike from a manufacturer that isn't interested in promoting weight weenie-ism.

Al doesn't have a fatigue limit, so if you can flex it, it should eventually crack. Steel and Ti have fatigue limits below which stress level they should not crack. Having said that, if you are heavy enough, you'll crack them too. It isn't common for Al to crack unless it has done a lot of kilometres.
Nobody
 
Posts: 6649
Joined: Thu Sep 18, 2008 12:10 pm
Location: Sydney

Re: frame cracks

Postby queequeg » Wed Mar 20, 2013 10:30 pm

mick243 wrote:
frame is stickered as being made of "7005 T6 Alloy".

how many other riders of the same model bike out there? I'm hoping that I'm just really unlucky here and have got 2 dodgy frames rather than it being a widespread issue?


Not a Jamis frame, but I broke two Trek alloy frames in 2 years, both in the same spot, where seat tube meets bottom bracket shell.
Both times the whole bike was replaced under warranty (actually, first time was everything except the wheels).
The alloy frame was obviously not designed to handle the daily punishment of commuting, despite being sold for that purpose.

I now have a Ti frame for commuting. No issues with the frame thus far, but I have destroyed a bottom bracket and a wheel hub, and been through about 4 pairs of disc brake pads in 18 months.
User avatar
queequeg
 
Posts: 2886
Joined: Thu Dec 17, 2009 9:09 am

Re: frame cracks

Postby DavidS » Wed Mar 20, 2013 11:13 pm

My Giant cracked in the same place after 3 years and 21,000Kms. I think if you weigh a bit, like I do, then you do have to be careful how much flex you are putting on the frame via the seatpost. Anyway, next bike on order with a bigger frame!

DS
User avatar
DavidS
 
Posts: 1336
Joined: Wed Sep 22, 2010 11:24 pm
Location: Melbourne

Re: frame cracks

Postby mick243 » Thu Mar 21, 2013 2:15 pm

its kinda odd ( to me at least ) I have several bikes - one is a 20 year old roadie CroMo frame but made very light, zero probs. another is a 10+ year old avanti alloy MTB (26er) doesnt look all that strong, I have bashed the living daylights out of it, destroyed some wheels but the frame is fine....... yet another is a cheapie commuter bike (light alloy cheap chinese manufacture) I was given whilst the jamis was off for repairs - I havent treated it kindly at all, it has done more riding in more places and worse conditions than the jamis and (appart from a few swcrapes in the paint) it still looks and performs like new. from a "looks like" standpoint, the design of the jamis should be the strongest and longest lasting of all of them yet I've killed 2 rather rapidly - and as for the suggestion of " Keep the MTB for MTBing and maybe get a commuter for commuting " if it cant handle a less than 10k commute on more or less flat good quality roads, how on earth will it last more than one "MTB" ride?

now, dont get me wrong - I'm not trying to stir up some jamis hate, I love how the bike rides - its faster and more comfy than either the roadie or the commuter, and "should" outperform the avanti 26er I have on the trails.

anyone here a frame builder - is there a design/manufacturing flaw in the jamis? can it be strengthened? one Idea I came up with was a longer seat stem to transfer the load farther down (at the moment, it only just goes past the top tube) but its already got a 400mm stem - do they come any bigger?
mick243
 
Posts: 210
Joined: Wed Mar 20, 2013 10:44 am

Re: frame cracks

Postby master6 » Thu Mar 21, 2013 5:45 pm

mick243 wrote:only just goes past the top tube) but its already got a 400mm stem -



I'm not surprised by the result. Schoolboy physics would explain what's going on here.
master6
 
Posts: 2661
Joined: Tue Feb 24, 2009 4:37 pm
Location: depends on who is asking, and why.

Re: frame cracks

Postby Nobody » Thu Mar 21, 2013 6:50 pm

mick243 wrote:and as for the suggestion of " Keep the MTB for MTBing and maybe get a commuter for commuting " if it cant handle a less than 10k commute on more or less flat good quality roads, how on earth will it last more than one "MTB" ride?
This was in regard to when the problem is fixed. Since you have other bikes to commute on, please ignore...

mick243 wrote:...do they come any bigger?
If you don't have the 21", then yes.
http://www.jamisbikes.com/usa/thebikes/ ... p_geo.html

master6 wrote:
mick243 wrote:only just goes past the top tube) but its already got a 400mm stem -

I'm not surprised by the result. Schoolboy physics would explain what's going on here.
Agree. If the 400mm post is at its insertion limit, it's usually a sign that the frame is too small.
Nobody
 
Posts: 6649
Joined: Thu Sep 18, 2008 12:10 pm
Location: Sydney


Return to The Shed

Who is online

Users browsing this forum: thamete



Popular Bike Shops
Torpedo 7 Torpedo7 AU
Ground Effect Ground Effect NZ
Chain Reaction Cycles CRC UK
Wiggle Wiggle UK
Ebay Ebay AU

“Bicycles BNA Twitter
“Bicycles BNA Facebook
“Google+ BNA Google+
“Bicycles BNA Newsletter

> FREE BNA Stickers
> BNA Cycling Kit
cron