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PostPosted: Sat Jun 29, 2019 8:20 pm 
Gold Trader / MacRetro rider
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Joined: Sun May 25, 2008 11:03 am
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Location: Sunny Bournemouth
To utilize a frame better I was thinking of one of these but basically I dont like the look of them and will spoil what would otherwise be a very clean build.

How acceptable are they in use ?, I dont want it to look like one of those odd commuters with 300mm of spacers, so can you reduce them with a hacksaw or are they in differing heights.
Ideally I'd like to add 2" or a bit more. Most look considerably longer than this :?

Anyone tried one of these ? Fork is a white brothers carbon, just a shame the steerer is a bit small. It would drop 1 1/2lb off the build for sure.


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PostPosted: Sun Jun 30, 2019 5:42 pm 
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What stem have you got?


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PostPosted: Sun Jun 30, 2019 6:30 pm 
Dirt Disciple

Joined: Wed Jun 19, 2019 9:21 pm
Posts: 21
????

I prefer ride comfort to looks personally, sorry for the small image

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PostPosted: Sun Jun 30, 2019 6:46 pm 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
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Some steerers don't like them, you risk the chance of the top of the steerer going pop........


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PostPosted: Mon Jul 01, 2019 12:26 am 
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I've never tried one and I don't know about them damaging steerers but the unbranded ones that always seem to pop up on eBay whenever I search for stems seem to be about 4.5 inches long. If the clamp is about 1.5 inches, that's about a 3 inch rise or roughly the target amount. Cutting might be an option but the bolt going through the star nut could be a problem: the bolt will be long relative to the extender if the extender is cut down. With luck, there will be enough thread on the bolt; if there isn't enough thread, you have a problem. In short, cutting might be more trouble than it's worth.


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PostPosted: Mon Jul 01, 2019 12:36 am 
Old School GrandMaster | Rider
Old School GrandMaster | Rider
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Joined: Thu Nov 26, 2015 7:29 pm
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Location: peak district
Have you thought about a stem with rise?


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PostPosted: Mon Jul 01, 2019 1:01 am 
Gold Trader / MacRetro rider
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Joined: Sun May 25, 2008 11:03 am
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Location: Sunny Bournemouth
Supratada wrote:
What stem have you got?


Running with a purple hope 70mm x 20deg, other bits are purple so id prefer to use that one, plus the rise is good for this.

The bike is purely for road use with slicks, so i dont see any undue load or torsion going on to it.

@Cassidy. Far as i can see the star nut bolt is secured by the top cap, so its just really a tube. Need to be sure to cut squarely, but I dont think its like the quill version where the bolt is needed for the wedge rather than just a little torque.

I extended an Amp ones using the quill version, but its not ideal and heavy as hell. Found the internal diameter of the alloy steerer fitted exactly the 1" dia section.

@Mattr.
I cant see how it could damage the steerer as its effectively doing the exact same job as a stem clamp.
Now Im only guessing, but id think the forces on the steerer for it to effectively snap it ,especially when you look at the thing skyhawk has fitted. Thats considerably more height than i was looking at so the tension/compression forces would be considerably greater. And many of the other gigantic set ups also seem to survive.

@Skyhawk.
Sorry bud, but i find that look to be an affront to the eyes. No offence intended, but its **** hideous look to any bike :lol: :lol:
Its the image I have in my head and on the build it doesnt look like it would win any aesthetic prizes, unless its the wooden spoon.
Extremely nice ti frame, pro4's in purple, inc purple rotors,skewers, x2's in purple. and XO drivetrain. So for me the look is important.
Worst comes to the worst id try to hide it with some sort of light battery pack or something. :lol: Ive manitou r7's which are pretty damn light, with a more than enough 265mm steerer. but this frame really suits a rigid fork.


Last edited by dyna-ti on Mon Jul 01, 2019 2:39 pm, edited 1 time in total.

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PostPosted: Mon Jul 01, 2019 7:35 am 
Old School Grand Master

Joined: Mon Feb 11, 2008 9:42 am
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dyna-ti wrote:
@Mattr.
I cant see how it could damage the steerer as its effectively doing the exact same job as a stem clamp.
Yeah, it's clamping to the top of the steerer and then adding a massive lever to it.

dyna-ti wrote:
Now Im only guessing, but id think the forces on the steerer for it to effectively snap it ,especially when you look at the thing skyhawk has fitted. Thats considerably more height than i was looking at so the tension/compression forces would be considerably greater. And many of the other gigantic set ups also seem to survive.
Many manufacturers (of forks and complete framesets) have a maximum numbers of spacers stated in the manual, exactly for this sort of failure. A "good" rule of thumb is 1.5x the diameter of the steerer. But i've seen 30, 40 and 50mm stated. There will be an allowance for risers bars and upright stems etc, but bunging an extra 3 or 4" is probably well outside their design specs!

"Seem to survive" isn't what i'd rely on ;)

Especially when you say
dyna-ti wrote:
The bike is purely for road use with slicks, so i dont see any undue load or torsion going on to it.
.
You can consistently achieve higher loads braking on slick tyres and tarmac than offroad/gravel.

But, saying all that, unless it's a superlightweight thin walled steerer, you should be ok.


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PostPosted: Mon Jul 01, 2019 3:11 pm 
Gold Trader / MacRetro rider
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Location: Sunny Bournemouth
Have to say Matt, its about shear isnt it :?

The projection of the steerer is encapsulated by the extender, so for the steerer to fail, it has to fail while in tension at the back, and compression at the front, meaning the front of the tube has to ripple and fold in on itself, while the rear of the tube stretches and snaps, or fractures and snaps.

What we are doing that would increase(or decrease rather) the shear efficiency.
eg the steerer projection is 40mm. Onto that we can fit a single spacer, then a hope stem. This is what im adding too remember
Fitting the uncut manitou, gives me a projection of 95mm, enough for lots of spacers(some 40mm, which is the number hope for example give you in a pack of spacers. I feel there if 40mm was too much as the shear standard lower, they'd do them in pack with a lower stack

So fitting the manitou puts the stem clamp some 40mm above the headset which is acceptable with a 100-120mm+ reach stem.

" "Seem to survive" isn't what i'd rely on ;) " Especially...

What i actually mean there is it isnt going to be bouncing up and down impacting and causing the front of the bike to shudder as it does offroad. I meant its on a smooth surface. Im always using a 183mm front, so i understand what you mean, but it doesnt apply. Especially when we look at that monstrosities that some riders use on commuting.
Not to cast aspersions on them per say, but most if not all here are more than capable of building, servicing and doing small engineering jobs keeping things running. We likely all share a practical nature, which is probably why were always building bnikes rather than off the peg.
The people you see extending the height dont have this intrinsic understanding and if they could get two extenders on raising 450mm on they would, as they think thats fine. Ive see dozens of well used commuter in for service with gigantic extensions like that.

Whatever the industry safety margin, its more than 40mm up and 120mm out. Or there would be reports of them breaking and there simply isnt.

What i need increases the height but with a shorter 70mm reach. To me it looks like theres less strain on it.

No, actually, :? I cant see this have such a issue. It seems to me that theres less strain put on it.

Also stems of the past were far longer, up to 150mm and more, which as a lever would add considerably more force acting to sheer the top off the steerer and Ive never head of that problem :?


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PostPosted: Mon Jul 01, 2019 3:30 pm 
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I was going to suggest, as it's only a 50mm rise, the insert quill type of quill to ahead converter would surely be the simplest and safest bet? It is extra weight yes, but only a nadge.


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