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adjustable stems and carbon

Old 01-31-22, 09:05 AM
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goldfinch
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adjustable stems and carbon

A biking buddy of mine is having back and neck issues when riding more than about 40 miles. She would like to be able to raise her handlebars. Unfortunately, she has a carbon fork and steerer, so a stem extender is out. Is it safe to use one of these adjustable stems that adjust from the top rather than side? https://www.amazon.com/gp/product/B0...7ACO5T769&th=1

Last edited by goldfinch; 01-31-22 at 09:07 AM. Reason: add image
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Old 01-31-22, 09:19 AM
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My preference would be a an adjustable stem that clamps to the steerer in the conventional way for a threadless stem.

Here is one choice: https://www.nashbar.com/ritchey-4axi...317009/p848194
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Old 01-31-22, 10:06 AM
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Given the same bar location (height) I would think the stress the stem placed on the steerer would be pretty much the same regardless of a, locked tight, hinge in the stem's middle or not. The imaged stem still has a pinch bolt type of clamp, just like the steerer risers I have installed.

Did she buy the bike from a LBS? Has she approached them or the bike brand for any limitations the carbon steerer has? Has she sought out a fitter who has experience with aging riders (and more to the point those riders who are not racer heads) There's a lot more to a well fitted and good handling bike then bar height. and I wonder if she has the wrong bike for her current needs. Andy (so many possibilities but so little data).
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Old 01-31-22, 03:13 PM
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Originally Posted by goldfinch View Post
A biking buddy of mine is having back and neck issues when riding more than about 40 miles. She would like to be able to raise her handlebars. Unfortunately, she has a carbon fork and steerer, so a stem extender is out. Is it safe to use one of these adjustable stems that adjust from the top rather than side? https://www.amazon.com/gp/product/B0...7ACO5T769&th=1
I dont see why a carbon steering tube should be any different from an alloy one in terms of stem compatibility.

People really do think carbon is fragile like glass? A steering tube is made to withstand 5Nm of clamping force, and take the abuse of having up to a 120mm or even 140mm long stem + handlebar + rider weight + rattle over potholes or cobbles. I doubt the position of the hinge on the stem makes any sort of difference.

My question with the above pictured stem would just be: how to you tighten the headset cap, there doesnt seem to be one?
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Old 01-31-22, 05:55 PM
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Some hinged stems (that are threadless) have a preload bolt at top of the portion that goes over the steerer. Once the headset preload is done the stem extension angle is set.

Many carbon steerered fork manufactures have published (often a s a warning sticker on the fork) a stem max height above the upper stack of the headset (or how much spacer below the stem can be installed). I have taken this limit as an example of how carbon steerers are not the same strength as metal ones (as I have yet to know of similar limits being placed on Al or steel steerers).

IIRC carbon fiber is very strong in tension but far less so when stressed across the fiber. When a force is placed across the fiber it's the resin strength that counts. Compressive forces that a clamped stem places on the steerer can and do deform carbon steerers. It's not uncommon to see this on service jobs. Add vastly increased leverage from a way higher bar location (then the designed intended) and the "working" strength of a steerer might not leave much safety factor. Andy
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Old 01-31-22, 08:03 PM
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Originally Posted by goldfinch View Post
A biking buddy of mine is having back and neck issues when riding more than about 40 miles. She would like to be able to raise her handlebars. Unfortunately, she has a carbon fork and steerer, so a stem extender is out. Is it safe to use one of these adjustable stems that adjust from the top rather than side? https://www.amazon.com/gp/product/B0...7ACO5T769&th=1
Seems safer to use a steeper stem. For example: Dimension Threadless Road Stem: 90mm; 125 Degree; Black; 1-1/8"; 31.8 - Modern Bike.

Sorry, please ignore! As veganbikes pointed out:

Originally Posted by veganbikes View Post
Dimension has made it quite clear: Dimension stems are not intended for use with carbon handlebars or carbon steerer tubes ...
https://www.dimensionbikeproducts.co...00102_INST.pdf

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Old 01-31-22, 09:04 PM
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Originally Posted by SoSmellyAir View Post
She is already using a very steep stem. I am thinking of going with the steep stem and then adding "riser" drop bars, like the Surly Truck Stop. I am squeamish about the carbon steerer and the adjustable stems that are top hinged.
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Old 01-31-22, 09:59 PM
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Originally Posted by SoSmellyAir View Post
Dimension has made it quite clear: Dimension stems are not intended for use with carbon handlebars or carbon steerer tubes (it is listed in your link where you say it seems safer)
https://www.dimensionbikeproducts.co...00102_INST.pdf


I would check with the manufacturer of the fork and see what they recommend if you plan on just going the roll the dice fitting route. Otherwise I would go the bike fitter route which is a better route and will lead to a more comfortable experience over all on the bike. Listen to Andrew R Stewart on this one he made some really excellent points. Though again I would check with the manufacturer if you intend on using other higher rise stems.
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Old 02-01-22, 08:22 PM
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Based on the fact that stem extenders are not suitable for carbon steerers and that top loaded adjustable stems are at best iffy, she ordered the riser handlebar instead. We will see it is enough to make a difference. She has extremely long legs compared to torso so getting a good bike fit is hard for her.
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Old 02-03-22, 09:37 PM
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Getting a bike fit is easy. Getting a bike that fits might be a bit tougher but the bike fit will really help.
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Old 02-18-22, 06:50 PM
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Success. The riser handlebar made a big difference. Tested over several long rides so it looks like we solved her problems with fit.
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