[Closed] Crank arm stiffness - Middleburn vs Hollowtechs

I think there's also a debate about how much actual (as opposed to perceived or believed) difference there is, the last test that measured crank flex showed that even Saints weren't [i]that[/i] much stiffer than ST shimanos (tho IIRC Middleburns were even flexier).

Where was that test Al? Thanks.

I can feel a fair bit of twang in some sugino square taper road cranks I have, and none noticed in my Shimanos. Just wonder where Middleburns sit on the scale in between since they look pretty skinny.

Your wheels and possibly rear triangle will be flexing long before your cranks.

That old chestnut ) It all flexes as a system based on stiffness in different areas and where the forces are. And lets say I already have a stiff wheel set, frame, stem, bars etc.

An ancient mbr, from when HT2 first came out, I'm afraid.

ok, ta.

WMB did a deflection test on a load of cranks a while back, but not sure if they had a middleburn in it. I thought the 7s felt pretty dang flexy, and that's something I'm normally oblivious to- I can't tell any difference between my weightweenie Noirs or my old Saints. But these things are so subjective, it could just be in my mind as I'm a h8er 😉

I use both Middleburn RS7 (on a rigid 29er SS) and various Shimano and Raceface external bearing cranks on geared 26in hardtails and FS bikes. The Middleburns *must* be flexier but I can't say I've ever noticed while riding or been bothered by it. As said above, it stands to reason that tyres, frames and wheels will flex long before a crank.

WMB did a deflection test on a load of cranks a while back, but not sure if they had a middleburn in it.

If its the issue I'm thinking of then, yes, they did have Middleburns in it, though it might have been the X-type ones.

If I do remember correctly the difference between the proper 'noodly' chainsets and the stiff ones was so minor (possibly less than 1mm) that I'm not sure people really would notice a difference out on the trails.

[i] As said above, it stands to reason that tyres, frames and wheels will flex long before a crank.[/i]

Wheels, frame, tyres, soles of your shoes.
How [i]much[/i] more can one crank flex than the other, really?

ST cranks have a much smaller axle than HT2 cranks, so are gonna be flexier

The stiffness of the Middlebrn cranks never bothered me but the way the crank arm protruded and rubbed my shoes/foot near my arch had me hating them... but this is a while ago and think they were RS3's but the current designs look similar.

1mm of deflection doesn't sound like much but it all depends on the load needed to do it. All I'm really interested in is whether it's noticeable under SS type hauling, especially when fitted to the kind of bike that will show up a flexy crank, bar etc. If in doubt.. probably best sticking with Shimano.

I went from a set of Octalink Deore cranks to a set of Middleburn RS7's.

Lovely looking crank but I got rid quite quickly as when cranking in the big ring something was definetly flexing/moving causing rubbing on the front derailleur cage.

All bolts,chainring bolts etc torqued and tight,everything adjusted correctly,no problems with gear shifting but definite rub/flex.

Now have set of Kore ext BB cranks and no noticeable flex and definetly no rubbing.
Got Raceface cranks on my roadbike no probs there either, and got a set of old Shimano 600 cranks on my SS which may flex but as theres nothing to rub on i havent really noticed.

It's v difficult to do a meaningful comparison between rs7/8s and other brands unless using the same BB

Comparing an X type to ht2 hone lx and xt I can't tell the difference.... Apart from the finish and far superior preload adjuster.......

You've got to be cranking out some watts to notice ANY flex at all. I know a few fast boys & have had this discussion with them - they said it was almost impossible to notice any flex at all. I certainly can't & my power is 200w at lactate threshold & 300w at CP30.

I'm not saying you aren't stronger but are you sure it's not in your head? Perhaps it's something else on the bike that's flexing as has been suggested..

I'm just asking to see if there's any general opinion, don't know much about non-Shimano cranks from my own use. Not saying they actually are flexy as I've not used them.

300w at CP30

I can out put out over 1200w for brief spells and use Middleburns for my singlespeed so I really don't think you need to worry about them. I really like them and will be buying my third set very shortly.

I don't think you need to be a racer to notice flex in things, just a perceptible rider of reasonable strength / weight etc. It's not because I'm a Hoy-alike or anything but it's not hard to feel the arms flex/twist on a skinnier crank.

My point is you do actually to be really quite strong to get crank arms to flex, I mean really, really quite strong...

You would certainly need to be putting out power a fair way beyond that of your average rider. Ask yourself this: "Are you the quickest in your group by some say or just keeping up or something else in between?" If youre not the quickest by some way then I would suggest that its in your mind - as you wont be making the power needed to get the cranks to twist.

Anyway, your money & your choice. Just offering some advice.

Ps CP30 is a Critical Power test performed as a maximum effort for 30 minutes. Its a reasonable measure of your sustainable power. The tests can be longer or shorter. Its very unpleasant..

I'm not the quickest in any group apart from the slow one, although I'm not usually the slowest and definitely not the lightest. I can definitely feel the difference between my basic truvative ST's and old deore HT1's. And there's a difference between my Deus, XT, XTR and Saint chainsets.

There's so much flex that it's bad, but there's enough that you can feel it.

This gives an indication of the magnitude of arm flex:

[url= http://fairwheelbikes.com/cycling-blog/products/fair-wheel-crank-test-4.html ]http://fairwheelbikes.com/cycling-blog/products/fair-wheel-crank-test-4.html[/url]

That's actually much more than I thought (0.1-0.3 inches), although it didn't measure whats more noticeable, the deflection of the pedals rather than the chainring.

Errrrmmm

Before cranks start flexing does the plastic of your (road) cleats, sole of shoe, foot, ankle, knee not flex/compress a bit more before the actual cranks start to bend?

The whole bottom bracket area flexes before the crank arms for me....

Should go without saying that other stuff is flexing, but, that doesn't mean it's not relevant. When I tried them it was on a scandal- I had a scandal at the time with SLX on it so a very straight compare. And yeah, I'm sure there was a difference, and it felt different from frame flex- pedal seemed to squirm a little underfoot.

The same thing's noticable on my commuter, which is a pretty stiff old mtb but has supercheap shimano squaretaper cranks on it. Much worse on that, naturally! But does make me more convinced that I didn't just imagine it on the middleburns.

(I have an old Soda which flexes like a bedspring, but it's Nice Flex. Cranks feel like Bad Flex.)

I use Middleburns on all my singlespeeds without any problems.

I reckon the pedal axles will be flexing long before the crankarms.

I've never quite understood why crank flex would affect handling. Other than for jumping/manualing...I don't really use my feet as such for controlling the direction I'm going in....I use my legs, hips, torso, shoulders, arms, hands and head.

❓

Pedals have always been there as simply something to stand on.

Al you who can DEFINITELY feel the difference, have huge power outputs, "reckon" this or that...

Do I need aracer to come along and tell you how poor the human body is at measuring stuff like this?

Did you do double blind tests?

Did you isolate the crank in a solid mounting, apply specified loads then measure its flex? Or did you just ride some bikes, with different frames, tyres, tyre pressures etc yada etc..?

Ask yourself this: "Are you the quickest in your group by some say or just keeping up or something else in between?"

Middleburn on my singlespeed and my 5 Spot. Both on square taper.
The 5 Spot was previously XT external BB setup. I haven't noticed any difference in flex although I know there must be different levels of it.
The only times I have ever noticed flex in the crank/bb were when using an FRM Ti bb and when I was running Cook Bros RSR with a Hope BB. Both led to creacking andc chain rubbing on front mexh but with RS7, UNO ring and UN72 on both atm I couldn't quantify it.
I am6'2" with 34" inside leg and size 11 feet so I have fairly big levers to turn the cranks with...

Not directly on topic but...

at uni (mech eng), one of the projects was to work with Middleburn to improve the fatigue life of their cranks to get through the (IIRC) JIS tests.

The guys in the project team (which included mtbers) were pretty unimpressed with Middleburn's engineering skills which seemed to consist of testing a part until it broke then sticking a bit more metal on where it broke. I'd be interested to know how much they've progressed since then becuase otherwise, it'd explain why Middleburn cranks 'feel' a bit flexy compared to better engineered products.

FWIW, I'm pretty confident that I can feel the difference in crank stiffness if there is a significant difference. Whether that actually makes me go faster/slower is very debateable.

example: see the slightly pointy bit of metal on the crank directly opposite the main crank arm - that was added because they used to crack there.
[img] http://t0.gstatic.com/images?q=tbn:ANd9GcRUw7kZlZY8pJGv3CV_Zx36u-LmNNuU1dwu_TsbdbjTIgWIARUx [/img]

clubber - Member
...The guys in the project team (which included mtbers) were pretty unimpressed with Middleburn's engineering skills which seemed to consist of testing a part until it broke then sticking a bit more metal on where it broke...

I find that encouraging.

So we can take it that there's no more metal on a Middleburn than there needs to be. 🙂

Actually surely this is just as valid a method at arriving at a solution by calculating it and then still having to do trial and error testing? (So long as the customer isn't the guinea pig).

cynic-al - Member

Did you do double blind tests?

No you're right enough, it's impossible to know anything without proper testing. What's the weather like? No point in even asking really without lab testing 😉

Comparisons- replaced my nice ancient shimano with crappy nonseries cranks, all other parts on bike the same. Bit of an extreme example tbh.

Comparisons- SLX vs Middleburn, both on Scandals with fairly similiar kit. Of course other parts are different but I don't see them producing the same effect...

it's not some loss of power or vertical squish I (believe I) can feel, tbh I'd be oblivious to all that even if it was in isolation... it's [i]twist[/i] in the arm (and maybe axle?) which equates to the pedal twisting/moving off the horizontal. And the human body [i]is [/i]quite good at detecting this sort of thing, it's how we stand up on slopes and shifting surfaces. If you stand on a floating pier you feel even the smallest swell frinstance. (if a pedal axle comes loose I notice it instantly but the play is very small) Probably would also be more pronounced on flats than SPDs for much the same reason?

Now all that said- it's never a problem, not to me anyway. Bikes do lots of things that are interesting but not really important.

and an overweight gear masher can be a good test rider

you called?

from my experience and moshing the hell out of SS kit and making very non flexy things go all noodly, I can say that I don't notice a massive(if any that I can say is definitively crank flex) difference when compared to xtr hollowtech and things like rotor Agilis and E13 cranks. I have decided that I don't Like Ti bottom brackets though as from a purely subjective point I know I've saves weight but my brain tells me it feels odd under full maul.

So we can take it that there's no more metal on a Middleburn than there needs to be

Not really. There could well be material being used that adds little strength/weakness or small amounts that could be added that would significantly improve them (by 3000% AWESOMZ!) 😉

clubber - Member
...The guys in the project team (which included mtbers) were pretty unimpressed with Middleburn's engineering skills which seemed to consist of testing a part until it broke then sticking a bit more metal on where it broke...

Even if you're using FEA, that's all you do. It's empirical engineering same as has been done in developing anything for thousands of years. FEA just offers you a shortcut as you can obviously just bend them virtually and see where the hot spots are. Doesn't mean you wouldn't have to build one to prove the results though

Absolutely but it was the nature of guesswork that suprised me. As I said, it works but it's not a very effective way compared to what they could have done.

Changed over to old style Sq taper Middleburns (RS7) running on a UN55 for my single speed and noticed no difference whatsoever to previous/current External cranks (Shimano/ Middleburn).
Love the look and love the fact they are made in the UK.

A friend uses RS7s for trials riding and wouldn't use anything else; whilst I have no knowledge on the subject I wouldn't have thought he would be using them if they were flexy.

Orangejohn + the trials guys value their nads......the warantee includes competition use for the 7's.......

With regard to my previous post the issue I had was chain rub when cranking.
No chain rub with deore Octalinks prior to the middleburns and non afterwards when switched cranks again to some ext BB cranks.

Its very possible that the chainrings themselves were flexing but as these too were Middleburns its still not a great advert for them.
I really wanted to like them but theres no way I could put up with the flex were ever it was originating from.

Regards power output ,figures don't always tell the full story,take Mark Cavendish for example his peak power output is nothing like Andre Greipels.
So on paper Greipel should be the faster sprinter,but as most people will have seen Cav has outsprinted him on numerous occassions.

Won't a hollow crank always be stiffer than a scalloped one (like the Middleburn's) for a given weight and material?

Bending moments and all that stuff:

http://en.wikipedia.org/wiki/Bending

I've always assumed that the reason that only Shimano make hollow cranks is because (until recently) they held the patent and wouldn't license it to people like Middleburn.

Whether you can feel the difference is another question. I prefer the Shimano cranks that replaced my Middleburns, but then I also changed from ISIS to HTII.

clubber - Member

Absolutely but it was the nature of guesswork that suprised me. As I said, it works but it's not a very effective way compared to what they could have done.
Posted 7 hours ago # Report-Post

Arguably not, FEA has only really been available to normal people in recent years. The Pace XC bikes used square tubes because it was easier to model than round tubes so they could do it without the aid of a supercomputer!

Even stuff like Aeroplanes wasn't properly designed on computers until the newest generation (A380 / dreamliner).

There's no way a small bike components company in the early 90's would have had access to it. The RS3 was about '94, the RS7 was essentially a forged +machined RS3, and the RS8 is a more machined RS7.

Won't a hollow crank always be stiffer than a scalloped one ..