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Define "crash damage".
Define "crash damage".
if you need that perhaps you'd better stick to knitting laddie ?
Well, stiffer bars are less likely to bend, if you are thinking of dents, you may have a point when wall thickness becomes very low, but when is that ever an issue?
Maybe you best stick to internet-forum-enineering-pedantry? Oh that's what you are doing!!! 🙄
but when is that ever an issue?
good point, I hadn't though it out that far - I've never seen a dented bar 🙂
However, my point was that increasing the diameter while using the same amount of material would make the bar stiffer but more prone to collapse under impact due to the walls being thinner
couldn't be bothered trawling through all this thread so I'll just pick on TJ (again)
TandemJeremy - Member
Al - yes I have used them, no I didn't notice any difference.Tell me - how much force do you use in steering inputs? Enough to flex a bar significantly? I doubt it.
Look at toys figures - 0.6 mm flex - significant? can you even feel that? Toys - you really think steering inputs are 10 kgs? More like 100 g would be my guess.
TJ - yet again your narrow minded view of riding and poor Motorcycling skillz are clouding your judgement!
Riding a bike is not just about sitting down and steering with the bars is it?, bars have to withstand a riders entire mass X force not 100g or 10Kg! are used to preload/lift a loaded bike and to weight the bike in turns.
All bars and stems flex FACT! And yes it's noticable FFS! I can visually see flex in both bars and stems. Choosing the right bar/stem (actually most bike components) is down to how little you want them to flex in use versus weight.
appologies if you've already realised elsewhere in the thread you're talking out your arse doubt I'll ever read all of it)
I agree that OS is not actually needed (but prob not for the same reasons as you) I use 25.4 bars and stems on all my MTBs (but choose wisely, just like every part I put on my bikes).
Teh oracle has spoken!
All bars and stems flex FACT! And yes it's noticable FFS! I can visually see flex in both bars and stems.
I don' think anyone suggested they didn't, but considering the forces required, how can you [b]see[/b] the flex while applying them ?
er.. with my eyes!
So, Simon what are the forces required? I have no way of measuring fow much force I can exert but I do know I can cause any DH bar/stem set-up I've ever used to flex noticably by pushing one grip while pulling the other.
GW - what you missed was that I was only talking about steering inputs and differentiating the steering inputs from other forces acting on the bars.
I agree that OS is not actually needed (but prob not for the same reasons as you)
Just my point. O?S is notr nessasary.
Waht I find interesting about this debate is in some instances people want bars to flex. Carbon bars to increase conmfort.
My point merely was that a standard bar does not flex enough under steering inputs to mean that OS bars are more precise in steering.
Oh - and with motocycles steering inputs are much higher as gyroscopic stability of the front wheel is much higher.
right - I just tried this out again. as rigid a set up as I could arrange - a set of rigid forks clamped in a vice, stem and bars on the fork stem. My full 80 kgs swinging on teh end of the bar - a few mm flex in the bar, none visible in the light bontrager stem. ( the end of the bar that I was not weighting didn't move)
OS bar and stem - the same.
Now its very empirical but is inline with toys calculations - 100 kg input a few mm flex
Is this critical for MTBing and does it make a significant difference to handling? I doubt it.
edit - did the same with a pair of bars I know to be flexy - very noticable flex in them - I didn't dare put my whole weight on them for fear of bending them
but I do know I can cause any DH bar/stem set-up I've ever used to flex noticably by pushing one grip while pulling the other.
isn't that called "turning" ??
What I mean is, if you don't do an experiment like TJ describes, how can you tell if you're seeing flex in the bars, or the tyres/forks/brakes/imagination etc etc
sfb - I assume he means loading in a vertical direction.
Do DH racers use OS bars?
sfb - I assume he means loading in a vertical direction.
I just tried that, and with the forks locked out it did feel like several mm flex at the bar ends, but I couldn't see because my hands were in the way, and it might have been the tyre...
SFB your OS bars more likely to fail is wrong, a simple sigma=my/I gives:
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So this means a 0.5mm thick 24.5 bar fails at approx300n (30 kg) Having looked at my inch bars I think they have a wall thickness of at least 1.5 . The 1.5 thickness failure of inch bar is 1000n (100kg) which is slightly less than the failure stress of 0.75mm OS bar. So you could have 0.75mm os bar which is the same stiffness and slightly tougher. But no one would do that, you would want it to be stiffer so go for 1mm which is 36% stiffer and 40% stronger. (all based my 200mm long cantilever model).
As regards TJ's argument about steering, he hasn't read my posts carefully enough, I clearly mentioned restoring force, watch any video of someone blasting flat out through a rock garden and the bars hammer in your hands. I personally define steering as guidance of the bike, so not just inputs to change direction but inputs to keep it going where you want.
Toys - with regards to hammering thru rock gardens and the like - I thought the idea was to keep a loose grip and relax? Thus there is some movement allowed? Restoring forces are still a lot smaller than 100 kg are they not?
TJ the truth is you and I have no idea how big the restoring forces are, but having felt some its significantly bigger than 100g.
toys - another thought - grips are rubber and allow some compression - and many folk use padded gloves - this must allow some movement between hands and bars does it not as the rubber compresses? Same as compression / movement in the flesh on your hands?
All I am saying is the few mm of flex in the bars makes no significant difference. The difference between and OS and a standard bar is not significant compared to flex elsewhere in the system.
What do DH racers use?
did the same with a pair of bars I know to be flexy
You've just done a test to determine whether bars flex or not and have determined that they don't....but you know that these other bars are flexy ❓
Whatever their sponsors give them.What do DH racers use?
cynic all - the flexy bars are cheapo alloy ones from a commuter with a 6 inch rise - not MTB bars. Teh branded MTB bars are sigificantly stiffer
And if you had actually read whet I had written you would see that the branded MTB bars did flex a few mm in line with toys calculations.
No one has yet explained why the few mm flex in the bars is so critical compared to the flex elsewhare in the system.
the flexy bars are cheapo alloy ones from a commuter with a 6 inch rise - not MTB bars. Teh branded MTB bars are sigificantly stiffer
Be careful what you draw from this - all Aluminium alloys have the same stiffness, so they will all bend the same amount for the same load. Its how far they bend before they break that separates on alloy and another (along with fatigue, corrosion resistance and a whole host of other stuff). So your cheap bars are more flexy because they are not as thick or not as big a diameter - ie the design is different.
As regards your comment about rubber grips whatever, you can differentiate between these by feel. The flex is all additive - so 20mm at the tyre, 140mm at the shock, 0.01mm through frame and 3 mm on the bars. You can still feel it. The other point is about timescale, bending in metals due to load is almost instantaneous, whereas your grips, tyres and suspension are enormously load rate dependent. I think this is where reducing deformation is most important its all about reducing delay between your input and the bikes reaction and vice versa.
Interesting toys - yes I realise that about the cheapo bars.
I think the only way to settle this would be some blind testing. I remain convinced that the difference in flex between standard and OS bars is not significant. I accept there is a difference but its what - a few mm under a 100 kg load. Or fractions of a mm under a load of a few kilos.
SFB - get some glasses
most DH racers will use OS - there aren't a lot of options for bars wider than 28" left in standard or direct mount stems . I run 28" standard bars in a point1 DM stem (very stiff stem set-up) can feel and see the bars flex if I try to.
TJ - you don't steer a bike by just turning the bars unless you still ride with stabilisers.
Fair enough TJ
I remain convinced that the difference in flex between standard and OS bars is not significant.
Seriously, try road bars, the difference can be huge.
Seriously, try road bars, the difference can be huge.
I think the loads are so much bigger in MTB.