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What difference does a longer stem make?


Chitts's picture

By Chitts - Posted on 25 June 2011

Hi Folks,

What difference to the handling will it make going from a 90mm stem to a 130mm stem. If it matters this will be on an Anthem x29er and I ordered the wrong length stem and am trying to understand what it will mean for the feel of the bike.

[Mod. moved to MTB gear - the question relates to an Anthem 29er]

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Rob's picture

AFAIK... Stem length will affect 3 things (at least - I'm no expert in this):

1. General handling: a shorter stem is more 'twitchy' as you have to move the bars less to turn. Think about how far you have to push a door open from the side near the hinge versus the other side where the handle normally is.

2. Weight distribution: a shorter stem will leave you further back which is better for technical riding (less OTBs). Sometimes you might get more traction too. That said, most climbers prefer a longer stem if they stand a lot.

3. Cockpit room: Go with something too short and you'll be smashing your knees on the bar. Too long and you might be stretching too far out which won't be so good for your back/neck.

FWIW, 4cm sounds like quite a lot to remove, but...

Having said all that - I recently shortened the stem by about that much on the crosser due to the neck problem I'm recovering from and can't say noticed much difference (handling wise) at all. Of course - I haven't been riding it off road or in twisty stuff so you wouldn't expect to notice either.

What is it you think is wrong with what you've got? I mean - if the fit is wrong and you have to change, you have to change, right?

Chitts's picture

Rob Said "1. General handling: a shorter stem is more 'twitchy' as you have to move the bars less to turn. Think about how far you have to push a door open from the side near the hinge versus the other side where the handle normally is. "

On a 29er, would "more twitchy" not be better given sttering in tight corners etc is not a 29er strong point?

The Athem 29er bar......is not great and I bought a Easton carbon bar but it is a 25.4mm vs the Giant stem at 31.8mm.

......'s picture

shorter stem will give you a less stretched out riding position. It depends more on the size of your bike and the size of you. I ride a large frame with a short stem. I feel that this gives me a nice riding position, and a more in control feel. I disagree that the shorter stem makes the bike more twitchy, i feel it gives you greater control. If you feel cramped in the cockpit, the easy answer is a longer stem. In saying that 130mm is a bloody long stem. Most riders have around 100mm on there stem.

Brian's picture

Doesn't Chitts say going from 90 to 130mm Puzzled

Little-Ditty's picture

The increase from 90mm to 130mm seems a bit excessive to me. In fact, I don't think I have ever heard of a 130mm stem on a Mtb before. That seems too much? You don't need to move your bike's dimensions around by more than 10-20mm before you are getting major geometric changes to your riding position.

My suggestion would be to alter other aspects of your bike rather than just changing the stem. Sure, change the stem, but not be 4cm. Try moving your seat backwards on the cromoly rails by 5mm to see if that helps.

You can also alter your apparent 'reach' if you have spacers both above and below where your stem attaches, by moving any spacers that are below your stem to all being above the stem. Or, your steerer tube could be cut and shortened by 5-10mm and removing the corresponding spacers (if this is possible).

Or you could adjust your handlebars by 'rolling' them forwards which should find you another ~5mm in reach.

Or you could get some wider handlebars which, if you add maybe 1-2cm per side, will mean your arms need to stretch out more and will also mean you have a slight increase in reach distance.

Finally, go to a professional at a local bike shop who can 'fit' you out on your bike and make more concrete suggestions about how to change your riding position and geometry on the bike. Sometimes you might pay a small fee for that, sometimes if they like you it can turn out free.

Cheers.

muvro's picture

To OP, You said you ordered the wrong stem, what length did you order and why?

As said, going to a 130mm stem is a massive change. The only advantage going to a longer stem (apart from trying to create more room in the cockpit) is climbing ability both in and out of the saddle by putting your weight further forward on the bike. However, the disadvantages IMO outweigh any advantage that it may have given. ie; reduced accuracy in steering (or increased vagueness in the steering, however you want to look at it), weight further forward means decending can be made more difficult and more chance of OTB on steeper/larger roll downs.

CharlieB's picture

Given you are not exactly long shanks, and maybe a touch vertically challenged… I would have thought that 130 is going to be a long way away.

Steal one off your other bike first to try.

+1 all comments above re impact of longer stem. Plus it will make it even harder to loft your front wheel (because your weight is further forward over the front wheel). But if that was where you wanted to get to, I would not be starting from where you are.

Chitts's picture

....I will just get a 90mm stem and shelve the one I purchased as a 130mm. As said it was a purchasing error and I just wanted to understand the difference it will make. Given it was reduced to $20 but was from overseas, it will not pay to send it back!

As to CharlieB's comment about me being vertically challenged.....I guess you have had ample time to evaluate that while riding behind me Eye-wink

Logan's picture

I find this effective for shortening a stem. Put yourself in a grade above your station and then just suffer and eat stem for the next hour on the bike. Low and behold your 130mm stem becomes a 80mm stem.

hawkeye's picture

After losing the top cap off my integrated steerer/stem the other week, I discovered that it it was 110mm and not 100 like I thought, and had been using on the old bike. (Duh!)

New bike (a Rize) seems to steer a lot better, and the front feels a lot more planted, while also being more stable. The old one (a Jekyll) was a bit understeery with the same rubber, even though they run identical forks and head angle. Obviously the slight increase in weight on the front wheel makes a difference to handling, but I was surprised the small change made such a noticeable difference to feel.

So I'm guessing 40mm is probably gonna make a big difference. Smiling

Pants's picture

If you have already ordered it, why not throw it on and see how it goes?

Little-Ditty's picture

Hawkeye, just because the Jekyll and Rize have the same suspension travel doesn't make the geometry identical. There will always be measureable differences between two different frame models. Although I would not say that this comparison was totally opposite, like apples and oranges, maybe more like oranges and mandarines? Smiling

ps's picture

I dont think the stem length directly impacts the steering response but happy to be corrected by an engineer or anyone more knowledgeable. Agree it changes body position and weight distribution which does have a huge impact on handling and steering feel.

btw my wife's XS specialized came standard with what looks like a 20 or 30mm stem.

......'s picture

Steering response has to do with lots of things, it has to do with the angles of the frame, with stem length, body position on the bike, rigidity of the frame and wheels, tyre pressure, tyre selection etc etc etc.

Stem length definataly contributes

hawkeye's picture

Ditty, yep I'm aware of that Smiling ... hence the reference to head angles. They're supposed to be different between the two if you believe the offical specs, but when you stand them next to each other on level ground, the forks are clearly parallel.

I realise other geometry differences such as chainstay length will have an impact on steering, but from my (admittedly limited) understanding, head angle (axle trail, to be more accurate) and weight bias (affected by stem length ... amongst other things) have the biggest impact for a bike of any given size.

Feel free to correct me if I'm wrong - always willing to learn Smiling

ps's picture

Let me clarify where I am coming from in my assumption that stem length doesn't have much impact on steering twitchyness. My specialized epic mountain bike comes in 4 sizes and the stem length varies from 75mm to 105mm. My expectation is that the bikes designer tries to achieve the same feel for a person who fits the small with the 75mm stem as a person who fits the large (me) with a 105mm stem. Given the handlebars are much longer than the stem my high school science tells me that its actually the handlebar that provides most of the leverage for the steering. I think the main reason the stems vary on given bike model is to get the bars away from taller peoples knees when they get out of the saddle. just my 2c

Agree there will be a difference in steering input/feel etc if you need to change a stem on a bike to get it to fit you but my experience has been that thats mainly weight distribution.

Personally I couldn't tell the difference a change of 10mm had to the steering of my road bike when we swapped the stem a few weeks ago

Brumma's picture

I think one of the greatest effects of a different length stem is the change in weight distribution and the effect on climbing, descending and control in the air. A shorter stem shifts your weight back and allows you to get over the back wheel while descending, keeping low and loose and unweighting the front end to float over obstacles.
In the air, because a shorter stem allows you to get behind the saddle, you can let the bike come up underneath you as you jump which means you're more stable in mid-air rather than flying dead sailor. When I first got my Reign, it came with a 110mm stem and I crashed a lot after getting airborne… I switched to an 80mm stem and became a lot more stable in the air.
The trade-off comes when you combine a slack head angle with a shorter stem and start climbing. Because your weight is further back and you're sitting in a more upright position its easier for the front end to lift off the ground on a steep climb and I think that's where the twitchy steering really starts to show.

nz_kgb's picture

I am going to come at this from a slightly different perspective from everyone else; rather than look at weight distribution and body position, it is helpful to also consider what a shorter/longer stem does to where your hands are in relation to the front wheel.

Think of where your front wheel touches the ground is the "impact point", for want of a better description. This is the first point of contact that your bike makes with the ground, the jump, the tree root, the rock.

Having established that, lets imagine exactly the same bike with a 130mm stem. The distance between my hands and the "impact point" of my wheel is relatively short as I am quite a way in front of my headtube. Of course things like stem angle, head angle, handle bar rise etc etc all make a difference too.

Take the same bike, same handlebars etc and put a 40mm stem on (about the shortest you can go if you are running 31.8 bars). You have just shifted back 90mm (about 4" in old measure) from the "impact point" of your front wheel.

So what does this mean on the trail? Well firstly, when my front wheel hits a tree root, I have more time to react with a shorter stem. Why? Because the distance between when the front wheel impacts the tree root and the time my hands are over the obstacle is greater, therefore giving me more time to react.

Secondly, tip your bike in the air to simulate going down hill. With the shorter stem, the trail has to be quite steep before my hands go in front of the "impact point" of the front wheel, again giving me more time to react when riding down a trail. Try it - you will be surprised at the difference!

However, as a couple of people have already intimated, on the flip side, if you angle your bike uphill with the shorter stem, you are defintely further back from the "impact point" of the front wheel with a shorter stem. This does mean that you have to consciously move your weight forward when climbing to weight the front wheel and keep it on the ground.

So, what sort of riding do you do? If you like grinding up fire roads and love burning your thighs up long climbs, a longer stem will suit you down to the ground. If, however, you enjoy blasting down singletrack and feeling balanced and in control of your bike, no matter what the trail throws at you, then a shorter stem is defintely the way to go.

My wife and I both ride medium Nomads, we both run 40mm stems and we both much prefer riding down the hill. On my singlespeed, which is a small 16" frame, I have gone to a 50mm stem for slightly more knee clearance, but still enjoy the sure-footed way that the front steers on the descents.

How do you conteract the twitchy steering that the others have spoken about (as this is something that genuinely comes into play with a shorter stem). Go for wider bars. Here in Nelson, because of our tight native trails, 740mm is ideal, anything wider and you have to use a lot of body english to get through some of those trees. But wider bars is a whole different topic again.

I know what I am talking about is quite different to the change between a 130mm and 90mm stem, but similar reasoning applies - go for the 90mm stem and then, when you are ready, wind that down to a 40mm stem and feel the difference - you will be surprised.

Cheers,

K

jcl's picture

no doubt a local store would have given you the right advise and no doubt done a swap if you bought the wrong one

nz_kgb's picture

But not necessarily had the one you were looking for in all the different length options.

To be honest, the options for us locally here are really limited, meaning online is a suitable option, even if we do have to sell off some mistakes on TradeMe.

......'s picture

it's always good to have a few spare stems, headsets, cranks etc etc in the spare parts box.

Macr's picture

I see where you are going, but I think it does effect twitchiness.
Lets look at it 2 ways. First from the stem point of view.
Fit 2 stems on a fork. 130mm on the bottom and the 80mm, just above it.
Now run a piece of string around your steerer to create a V out the front.
Now measure how much deflection each stem has to move from centre,to run parallel with the string.
The longer stem takes a lot more deflection to reach the same point, whereby proving that the shorter stem is twitchier, as it takes less deflection to reach the same angle of steering.
Now factor in cockpit space. It may be 80 for someone and 110 for another, but if you lengthen both to create more room, you still have the same ratio of greater deflection the longer you go.

Now from the wheel
Same set up with the 2 stems, but add 2 sets of bars.
Whilst holding the shorter bar, get someone to twist the wheel from side to side.
Now try that with the longer bar.
Which is easier to stop the twisting motion?
The longer bar will be.
Once again proving that a shorter stem in twitchier.

Finally, I have just reduced my stem on my 29er, from 110mm to 80mm, just the other day to gain more traction on the rear wheel (as my weight was to far forward) and to speed up steering to get around tighter switchbacks.
I rode the same bit of track two days in a row and noticed that I was cornering the switchbacks a lot tighter, with the shorter stem. The added benefit, was I could loft the front wheel a lot easier.
If I went any shorter, I would likely have even more traction on the rear wheel, but I think the front would start to lift. So stem choice in this case is a compromise to find the best balance.

Does that all make sense?

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