lars from transition says deffo dont do it 
Bike Forum
to ream or not to ream, that is the question
-
Posted 6 months ago #
-
Go on do it, bet they're updating it for 2012/13 so would be a good excuse for a new frame
It's not like you're doing massive jumps or anything
Posted 6 months ago # -
To be fair no manufacturer in the world is going to say ream my seat tube*
*unless you were wasted at interbike or something
Posted 6 months ago # -
To be fair no manufacturer in the world is going to say ream my seat tube*
*unless you were wasted at interbike or something
Remind me never to get wasted at interbike...
Posted 6 months ago # -
Jedi, keep your eyes peeled. I will be listing my GD this/next week in the classifieds dependent on when the replacement arrives.
I need cash at the moment so I'm swapping it for a less exciting 30.9 upper downer.
Posted 6 months ago # -
We switched from using 30.0 to 30.9 seat tubes on our AM and DH frames when uppy-downy posts became more common. The OD remained the same and I can't see that we've reinforced anywhere else to compensate.
Suspect it will be fine but like Transition I'd not 'approve' it as a mod - ie almost certainly ok but at your own risk.
Posted 6 months ago # -
TJ how does increasing the internal dia by 3% cause it to lose 20% of its strength?
Have you run FEA on it then?
Im not saying you're wrong (yet), but im interested to see your workings.Posted 6 months ago # -
How's the riding simon?
Posted 6 months ago # -
ream it! im sure Graeme will understand and give you a new one if it goes wrong (maybe in your 'decorators radio' paintjob too
)
Posted 6 months ago # -
Jedi - pop into HARRIS Motorcycles in Hertford, they possess all the aluminium working tools and knowhow you could ever want, and then some. They've been helpful in the past for me.
Posted 6 months ago # -
simons_nicolai-uk - Member
We switched from using 30.0 to 30.9 seat tubes on our AM and DH frames when uppy-downy posts became more common. The OD remained the same and I can't see that we've reinforced anywhere else to compensate.Suspect it will be fine but like Transition I'd not 'approve' it as a mod - ie almost certainly ok but at your own risk.
That's at odds with how I thought Nicolai would do things... I'd have thought making tubes thinner would have involved hundred of hours of German engineering
Posted 6 months ago # -
also some seat tubes are externally butted at the seat clamp area so just because it is thick enough at the top does not mean it will still be thick enough lower down
but measure it up and see..
I say go for it.. nothing ventured nothing gained..
Posted 6 months ago # -
TJ how does increasing the internal dia by 3% cause it to lose 20% of its strength?
Have you run FEA on it then?
Im not saying you're wrong (yet), but im interested to see your workings.I assume he has based it on the reduction of cross sectional area because it is about 20% loss. Which isn't far off. As a guide, based on standard beam calcs, the loss of stiffness in the reamed length is about 15% and the increase in peak normal stresses in the reamed length are about 16%. Given that its the junction of the top tube and seat stays etc a bit of FEA would tell you more, my hunch is it would probably tell you its worse than the beam calcs. Whether this reduction is significant is down to how much margin there is on the design...
Posted 6 months ago # -
I can't see why you'd weaken your frame and invalidate your warranty just to fit a dropper, when there are loads of 27.2 ones around.
Posted 6 months ago # -
Well my Helius CC has a 31.6mm seat-tube diameter and a 34.9mm seatclamp, can't see it being too much of an issue* if you ream it to take the 30.9mm post.
How snug a fit is the 30mm one anyway?
*I have no experience in reaming of metals and will no way be held responsible if you get a dropper stuck up yer bum
Posted 6 months ago # -
my Helius CC has a 31.6mm seat-tube diameter and a 34.9mm seatclamp, can't see it being too much of an issue* if you ream it to take the 30.9mm post.
The default tube used at Nicolai is 34.9/31.6. We use a thicker walled tube on the frames for more hardcore use and for XL sizes but the Helius AM, say, is still 31.6 so that's not a weak tube..
How's the riding simon?
Infrequent off road for the last month or so
but heading somewhere hot and dry for December...
Posted 6 months ago # -
matthew_h - Member
The reaming is not done in one big hit, it is done in stages and the bottom of the reamer is not square to the tube so end up with a graduated step, not too likely to be a significant stress riser.
fairy snuff
Posted 6 months ago #
Reply
You must log in to post.
