135mm OLN hub in a 130mm alloy frame?

[Brucey]

I agree; quite a lot of frames are not exactly as they are meant to be, and it isn't that difficult to respace wheels to suit.

cheers

[The utility cyclist]

frames crack by fatigue because in use, they see an alternating stress. If you 'spring' a frame then you increase the mean stress, and as the plot above suggests, the tolerance for cyclic stresses is reduced whenever you do this, i.e. the frame is more likely to break via fatigue.

Steel frames can usually be cold-set to a new dimension but aluminium frames usually cannot, not without a significant risk of damage, anyway.

cheers

Nice graphic but meaningless because you're not stretching the frame constantly, maybe 6 times a year if you're really unlucky with rear wheel punctures and.or are a bit anal with cleaning.
But let's get down to nuts and bolts, how many actual failures in 130mm OLN alu framesets from fitting 135mm hubs?
Tell you what, start by contacting Spesh given the Globe range at least had this as the std setup on the whole range (I know because I own two and gave one to my partner), get back to us with a failure rate?

[Vorpal]

Can you explain what I'm seeing here?

What's in my mind is that a one-off flexation which is then locked in place and cannot then move/flex is very different to say a badly-specced tubeset (the Vitus 979 one spring (arf!) to mind) where constant flexing is taking place.

Am I misreading?

But when you force it further open, you increase the stresses in the rear triangle. The variable stresses, which occur naturally in use are on top of that.

Yes, I get that, but then I lock it in position with the QR and an axle, and little or no deflection occurs thereafter, shirley?

Bike frames flex all the time. They aren't large movements, but they are there; road vibration, potholes, bumps, dropping off a kerb into the carriageway, etc.

Aluminium does not have a fatigue limit (see viewtopic.php?f=1&t=121480&p=1232577&hilit=fatigue+limit#p1232577 for more information). That means that it will break eventually. And it will break where the stresses are highest. Increasing the stresses in the rear triangle is likely to reduce the life of the frame. What I cannot tell you is what that means in terms of the actual life of the bike. Chances are quite good that you can ride around with it for years. But it may be worth googling your frame model for failures and see if others have reported rear triangle failures before proceeding.

[Brucey]

frames crack by fatigue because in use, they see an alternating stress. If you 'spring' a frame then you increase the mean stress, and as the plot above suggests, the tolerance for cyclic stresses is reduced whenever you do this, i.e. the frame is more likely to break via fatigue.

Steel frames can usually be cold-set to a new dimension but aluminium frames usually cannot, not without a significant risk of damage, anyway.

cheers

Nice graphic but meaningless....

no.

Just no. Don't believe me (or any other competent engineer/materials scientist) for some reason?

FWIW I see plenty enough aluminium frames that break in the rear triangle even when they are not sprung. Sprung ones are worse.

The thing that helps kill the frame is the static stress, upon which the alternating stresses are superimposed. The static stress varies with how stiff the back end is and how far it is sprung. If you build a frame that isn't super stiff and needs to be sprung a couple of mm, it might have a reasonable lifetime. If you take a typical aluminium frame and spring it 5mm, it is much more likely to break.

[andrew_s]

meaningless because you're not stretching the frame constantly, maybe 6 times a year

The frame is stretched all the time the wheel is in place. The fact that the amount of stretch doesn't change is of no relevance.

If you say you've stretched a chainstay 2.5 mm to accommodate the wheel, and then stomping on the pedals shoves the BB over another mm, the stretch is changing from 1.5 mm to 3.5 mm every pedal stroke. What Brucey's graph shows is how much more damaging that is to the life of the frame than the change between +1 mm and -1 mm that you get with a frame that's not been sprung.

[zenitb]

Looking at breakages that I have personal experience of, both the steel items bent rather than fractured .. My old Reynolds 501 steel mountain bike frame, and my riding buddy Phil's Muddy Fox MTB frame (steel Tange Infinity tubing ..I was devastated to see that frame written off). The key thing is with both of these incidents is that the bike rode on for a while, not necessarily completing the mission, but not immediately dumping the rider off either.

In contrast the aluminum things I have broken have just failed catastrophically .. see the pics of my (26 year old) seatpost and my (14 year old) Marin East Peak frame. One minute fine, next minute - bang. In the case of the Marin in was only the front mech cable that stopped the frame snapping in two (the shifter was destroyed in the process though!).

Ok not a scientific study but this is why I would instinctively avoid forcing or bending any of my alu frames.. fear of catastrophic failure.. !!! Plenty of 130mm hubs out there to choose from