What will an extra ...
 

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[Closed] What will an extra 15mm on my stem do for me? Ooh err..

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Another idle musing, well maybe not. Had the current bike over a year now. When I demoed it I was hovering between size L and XL but went for XL because I prefered the extra reach while standing but because my stiff back found the seated position a bit of a stretch I specced a 35mm stem as opposd to the standard 50m and had an extra 10mm spacer added under the stem to make it comfortable.

Back has loosened up a bit now and I think I could cope with a bit more stretch while seated and I am getting the feeling that I need to get further over the front while descending. I'm still a bit stuck in my old school short, high, steep 26" ways of hanging over the back. Should I be sorting my body position or bits of the bike or both?


 
Posted : 08/05/2021 10:22 pm
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And bump for show...


 
Posted : 08/05/2021 10:23 pm
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hanging off the back can be as a result of a reach that is too short, especially if the bars are comparatively low.if the fit isnt right its impossible to change your body position without compromising how the bike handles, particularly in corners. i would experiment, you wont know until you try.

this might be useful http://yojimg.net/bike/web_tools/stem.php


 
Posted : 08/05/2021 10:38 pm
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Roll your bars forward. You might get another 15mm or so of length. Bars with a lot of sweep may feel weird like this. But you can test out the extra length.


 
Posted : 08/05/2021 11:35 pm
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Forgot to say, pretty sure I have a 50mm stem in the shed that will fit so wouldn't take a lot to try it.


 
Posted : 08/05/2021 11:40 pm
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The only way to know is to try the longer stem and see how you like it.


 
Posted : 09/05/2021 2:39 am
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If the standard stem was 50 it should handle well with that stem surely. Just put in on and try it, it is only a 5 minute job after all.


 
Posted : 09/05/2021 7:05 am
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Just found two 50mm stems in the shed, one higher rise than the other not sure how much rise they have though. Spoilt for choice!

@sailor74

hanging off the back can be as a result of a reach that is too short, especially if the bars are comparatively low

So, are you saying I should keep the bars high? I thought lowering them would have the effect of pulling me forward. Good link thanks!


 
Posted : 09/05/2021 8:55 am
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So, are you saying I should keep the bars high? I thought lowering them would have the effect of pulling me forward. Good link thanks!

My thinking is that, for seated position, you are basically rotating around the bottom bracket. If you fit a longer stem and move the bars forward, you also need to slide the saddle forward and move the bars downward a bit to have everything in the same relative position.

However, you just need to try different setups and find what works for you on the terrain you ride. The only thing that matters is whether you are comfortable on the bike.


 
Posted : 09/05/2021 9:16 am
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@thols2 I am more concerned about getting a better standing, descending position and getting further over the front of the bike. Seated position is fine at the moment but I think I could deal with a bit more seated stretch if a new bar position would benefit the descents.


 
Posted : 09/05/2021 9:26 am
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i recall building up a bike and using a stem i had to hand that matched something random...was unpleasantly surprised by how poor the handling felt...swopped the stem and felt great...can't remember if longer or shorter but 15mm made a big difference...at least for me...as to moving seat forward...1 thing at a time is a good rule


 
Posted : 09/05/2021 9:43 am
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generally if you are riding a short reach bike (relative to your own body size) you would want the bars higher in order to weight the front wheel standing up, especially down hill.
if you extend the reach with a longer stem then you would likely run less spacers and 'lower' the bars to achieve the same.
note that a longer stem has the effect of raising bar height and lengthening reach at the same time assuming the same spacers.

stem length might not be your problem though and you may find that rolling the bars forward and/or adjusting your lever angle will allow you to get your elbows out more thus shifting your weight forwards.

ive only ever worried about how a bike rides/feels when stood up, you shouldnt be tackling anything of any significance sat down.

i wouldnt be afraid to try out extremes either, i remember Fabien Barrel used to turn up and win races races with 40mm of spacers under his stem bucking the 'slammed' trend at the time. then one day he turned up on what looked like a stretched out chopper and 'forward geometry' was born.

i used to spend hours repeating the same 30 second run adding and removing spacers, changing stems, altering rebound and compression 1 click in/out, adjusting bar roll, lever angle etc etc. you have to find what works for you, but that also changes over time as your riding evolves and/or the conditions change.

my only word of caution is that its easy to go down the rabbit hole of becoming all OCD about your setup!


 
Posted : 09/05/2021 10:06 am
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I did the opposite around a year ago - 10mm shorter stem, 10mm riser bars instead of 30mm and a flat headset cap instead of a 15mm rise cap and its made a huge difference to the feel of the bike when descending, much more than I expected and for the better


 
Posted : 09/05/2021 11:12 am
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I’ve messed around with this a fair bit too. Found that I don’t like it when the hands get too close to being in line with the steering axis and that there are very obvious changes in steering feel as you approach that. If you lay a metre rule or piece of string between the centres of your grips, you’ll see that it passes pretty much through the centre of the steerer with your 35mm stem. So basically you have an effective stem length of zero.

Going to a 50mm stem whilst changing nothing else will be like going from about 0mm to about 15mm, not like going from 35 to 50.

Try it, it’s an easy swap and you may be surprised.


 
Posted : 09/05/2021 12:31 pm
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@chiefgrooveguru you're right about that, I can see it while riding that the grips are lining up with the steerer cap.
Just been out for a couple of hours on the same stem and made a concious effort to get low and further forward while descending steep stuff. Definately felt more in control but suspect a longer stem might make that a bit easier. Will try the swap and see.


 
Posted : 09/05/2021 1:37 pm
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15mm is a big difference to me, I recently rode someones bike with a 70mm stem and it was horrendous, personally I can't get on with 35mm stems, I run a 50mm stem and holding a piece of string from bar end to bar end at the back of my grips the string is in line with my stem cap bolt, bar heights and roll can change that completely though and every spacer under the stem reduces reach slightly. You can get 40 or 45mm stems, unite even do a 42.5mm stem if you're running 35mm bars.


 
Posted : 09/05/2021 7:28 pm

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