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Has your MKIII cracked?

31K views 276 replies 68 participants last post by  KevinB 
#1 · (Edited)
Just curious and thought we could have a informal survey. What year, how long you have had it, has it cracked?

07, 5 months, no crack. I love this bike and definitely want to get an extra triangle before some long bike trips this summer.
 
#276 ·
Buddy of mine cracked the rear triangle on his MKIII. Usual spot, drive side bottom of the vertical leg at the front of the chain stay. He replaced it with a stumpjumper EVO, He gave me the frame to play with. I may model it in SW and do a FEA analysis on it for a project. However, I already have a good idea where the stress is....;) I'll also model some extra gusseting to see if I can improve things a bit on the FEA before I make them for real.
 
#7 ·
05 rub cure

pedalingkiwi said:
05 model - ridden since March.06, no cracks:thumbsup: , just lots of tire rub inside the triangle:mad: (running a 2.25, on stiffer than standard wheel) Though I weigh near 200lb kitted, I don't go particularly hard on the trails;)
FYI, I have an 05, had lots of rub on the non-drive chainstay. I got rid of 95% of it by replacing the stock rear wheel. Others have had similar experiences and results.
 
#12 ·
'06 bought in '08. Yes, it got fingered and molested for two years before I brought her home.

Had her tuned, replaced 80% of the stock parts, ( damn near everything but the shock, fork, frame and wheelset).

Cracked the triangle just above the weld on the drive side above the stay after 8 months of hard use. I am a Clydesdale racer (225 lbs) and and hard on everything I ride. :ihih:

Cheers.
 
#16 ·
Bought my '05 comp in july '05.
Found the main frame cracked on the seat tube/ bb weld in december '08, when i pulled it apart to send it off i found the swingarm cracked along the tubing directly under where they usually crack. You couldn't see it unless you took the rear wheel off.
IH looked after me and sent me a '05 team frame.... stoked!, another 3 years of mk3 goodness to come.
 
#19 · (Edited)
just bought a used 07 expert frame (with tire wear on the inside left) and hopefully it will last me a while... at least it didn't crack for that person. :)

Love the new setup. One ride was all I needed with a steep climb I usually can't make to convince me this thing is great for climing as well ! (and clipless pedals). Way down was great, until I landed on my face during a big jump :(
 
#20 ·
That left tire rub is an indication of a cracked or weakened rear triangle. Check over all the welds carefully. Clean it off and get in good light. Before mine completely failed I could pedal hard and pull the rear tire into the non drive chain stay fairly easily.
 
#21 ·
gtdrew said:
Before mine completely failed I could pedal hard and pull the rear tire into the non drive chain stay fairly easily.
I've always been able to do that with a larger tire in a smaller cog, but not easily.

It is interesting you say that, because I have been suspecting that it is the pedaling forces, not the pounding over rocks or drops that cracks the triangle where it does.
 
#22 ·
tire rub

gtdrew said:
That left tire rub is an indication of a cracked or weakened rear triangle. Check over all the welds carefully. Clean it off and get in good light. Before mine completely failed I could pedal hard and pull the rear tire into the non drive chain stay fairly easily.
I checked the rear frame (disasembled) pretty carefully after I received it and reading about all the issues on mtbr. Might have not bought a used frame had I read it before :)
didn't see any airline cracks.

Here is what he said about the rub - though it's more than slight one and definitly to the metal - I guess I should paint that area back and see if my current 2.20 tire rubs, then I know I have a problem...

-------------------
As to the tire rub. It was an issue on earlier frames and was partially resolved on the 2007. I did have slight tire rub using a 2.35in Kenda nevegal tire on a sun singletrack rim. In fact there is a slight tire rub mark on the frame(nothing to be concerned about, not even through the paint all the way). If you're familiar with the 2.35 nevegal you know that is a very big tire. Anything smaller does not rub at all, so the obvious solution is to run a smaller tire! I ran a quick release rear axle and was fine. Obviously, stiffer is better so a bolt on axle would stiffen the rear a little, but I was fine running a 2.25 tire with a QR.

To be brutally honest, there are some compromises(well known in the bike industry) with Iron Horse. The rear isn't the stiffest, the tight tire clearance, paint isn't as durable as a true "automotive style" paint. But you are getting the best rear suspension design in the industry for (hopefully) 3-600$. To step up to a top quality bike with the same suspension design you are forced to look at the turner 5 spot( 2100$ frame only), Ibis Mojo (2k frame) and Pivot Mach 5(2300 frame). I looked at it as a great bargain as the minor problems were quickly outweighed by the ride and performance of the suspension design.

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Well I'm around 190lbs so around 200lbs with camelback, shoes and gear and I would only get minor frame rub with the 2.35 nevegals while standing and pedaling hard. I already have the bike apart now so I can't really measure the clearance. I can only say more than enough tire clearance with 2.25.

-------
Yeah, didn't think the tire wear was too bad, considering what is normal for the frame. I spoke to the frame designer and former product manager of IH about it and he was not in the least bit concerned when looking at it.
 
#23 ·
I have an '07, but it's one of those Performance Bike specials, so it's probably actually an '06.

I've had it for about a year and a half.

So far, no cracks, but I have a history of breaking frames, so it's just a matter of time. (I don't think I ride particularly hard, but I do ride a lot and I weigh just over 200 lbs.) I purchased a MkIII swingarm on eBay yesterday. Hopefully, when it does eventually crack, I'll get a few more months out of the bike with the new swingarm before moving on.

I'll likely get a Turner or an Ibis next. That's some serious money though and I'd prefer to push that day out as far as possible.

Oh yeah, no rear tire rub on my bike.
 
#24 ·
i've never had an issue with tire rub. i recently switched from a qr in the rear to ck fun bolts and let me tell you, it is very noticeable. i was having non stop rotor rub issues and crappy feeling brakes because i couldn't get the rear end to stay where it should be. i'd pedal hard and the rotor would rub. i switched to the fun bolts today and no rotor rub. rear felt much stiffer and more responsive.
 
#25 ·
I had a bit of tyre rub on my 07 Expert. Probably cause by the DT hub always coming loose, the cheesy DT quick release didn't help either. Swapped it for a Shimano, which is better, but the hub needs checking every ride. Some sort of bolt up would be better.
 
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