Is stem length critical to steering?

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DaveP
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Is stem length critical to steering?

Postby DaveP » 16 Aug 2008, 8:30pm

I've been trying to decide between a new frame that is, to all intents and purposes the same size as one that I have been using without too many problems, and the next size up. The reason for considering the larger frame is simply that the top of the headtube is significantly higher, which would allow me to set the bars higher without the need for a big stack of spacers. I'm hoping that a higher riding position would ease the problems I've been having with numb fingers after a couple of hours.
Its a compact style, so the increased seat tube length isn't going to be too critical. The standover height is acceptable. The virtual toptube is longer, but I had thought to offset this by using a shorter stem, which would be about 60mm. Then I noticed that for this size frame the manufacturer is actually advising a stem 120mm long.
Leaves me wondering if I'm making a silly mistake...
Is using a stem so much shorter likely to have an impact on the quality of the steering? Or are they just assuming that prospective purchasers would want to stretch out and get their heads down?

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cranky
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Postby cranky » 16 Aug 2008, 9:22pm

I've been playing around with stem lengths on both my bikes with lengths between 70mm and 110mm with no real difference in handling. I've even read in other posts of people using 'negative' stem length (pointing the stem towards the rider) and cycling quite happily so I don't think it's any big deal so long as your comfortable and your happy with the way it feels.

As to frame sizes, I have a 56cm Ridgeback Genesis Day bike with a very quick frame, just a couple of sizes too small for me. When I went hunting for a new bike I got a 58cm Surly frameset that's about the equivalent of a UK 60cm with a 58cm top tube. The extra height on the steerer makes a huge difference to where you can put the bars.

Incidentally, I only use one spacer, it's 83mm long....
Image

I don't think you should worry too much about experimenting :)
Iain

Ridgeback Genesis Day 2
Surly Long Haul Trucker

cambsos
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Postby cambsos » 16 Aug 2008, 9:50pm

Sorry, but I totally disagree and have found stem length to make a lot of difference to the steering.
From my experience switching from 120 to 60 is going to make the handling much quicker and far more direct.

How about trying a 90 and see what you think?

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andrew_s
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Postby andrew_s » 16 Aug 2008, 11:03pm

It won't make a lot of difference to how the bike actually handles, but it will feel different until you get used to the differing steering input required.
With a zero length stem, you have to turn the bars by moving opposite hands forwards and backwards, but with a long stem you swing the bars from side to side more.

David Cox
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Postby David Cox » 17 Aug 2008, 12:15am

I've found that it depends on the geometry and the forks. On a much loved Bianchi Pro I shortened the stem once to avoid neck/shoulder ache, no problems. But when I reversed it to gain a higher position it spoilt the handling. Steering was less linear and in motoring terms switched from understeer to oversteer. Not satisfying and difficult when riding in a bunch.

With more forgiving geometry of Specialised Tricross and Trek Pilot I've tried various stem lengths with no ill effects on handling.

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Postby Ambermile » 17 Aug 2008, 12:20am

cranky wrote:I've even read in other posts of people using 'negative' stem length (pointing the stem towards the rider) and cycling quite happily


Bugger that - castor angles and all? You'd need arms like a Spanish Bull-Wrestler to get away with it! Well, maybe you'd be OK in a atraight line but you'd never get round a corner! (Unless it was very big one)


Arthur
I make stuff, that's all.

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cranky
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Postby cranky » 17 Aug 2008, 12:28am

Ambermile wrote:
cranky wrote:I've even read in other posts of people using 'negative' stem length (pointing the stem towards the rider) and cycling quite happily


Bugger that - castor angles and all? You'd need arms like a Spanish Bull-Wrestler to get away with it! Well, maybe you'd be OK in a atraight line but you'd never get round a corner! (Unless it was very big one)


Arthur


Castor angle isn't affected by the stem, it's fixed when the fork rake, head angle and wheel size is set. (AFAIK)

Take a look at CJ's post a little way down this thread
Iain



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Ambermile
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Postby Ambermile » 17 Aug 2008, 12:36am

...but the amount you have to move the stem to get the thing to turn... in a wrong way sort of way? Surely the angles are all wrong and nothing good will ever come of it? The further away from the "right" place your stem is, the bigger biceps you need - until eventually you'll look like Kenny Everrett on top of that tank!


Arthur
I make stuff, that's all.

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patricktaylor
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Postby patricktaylor » 17 Aug 2008, 8:00am

The only thing that matters, surely, is the relationship between the steering axis and the position of your hands on the bars. How they are linked makes no difference.

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Cunobelin
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Postby Cunobelin » 17 Aug 2008, 8:19am

Ambermile wrote:...but the amount you have to move the stem to get the thing to turn... in a wrong way sort of way? Surely the angles are all wrong and nothing good will ever come of it? The further away from the "right" place your stem is, the bigger biceps you need - until eventually you'll look like Kenny Everrett on top of that tank!


Arthur


I have a Hurricane Recumbent with "Tilt 'n' Steer" In upright mode the steering is direct, at full speed riding the bars are some 400 mm behind the column, more of a rudder.





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The steering alters in character, but you simply (unconsciously) adapt

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DaveP
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Postby DaveP » 17 Aug 2008, 5:38pm

Well I dont think I'llneed to go to a negative stem length, this time, so I think I'm reassured, especially by the handy reference to CJ's comments, which I had actually seen at the time, but forgotten :oops:

All I have to do now is to come to a decision about the colour. Red? Blue? Custom... :lol:

Nice spacer BTW Ian - definitely the way to go once the washers have been counted!

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cranky
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Postby cranky » 17 Aug 2008, 6:09pm

DaveP wrote:Well I dont think I'llneed to go to a negative stem length, this time, so I think I'm reassured, especially by the handy reference to CJ's comments, which I had actually seen at the time, but forgotten :oops:


For todays ride I used a longer stem with less rise to it, borrowed from my Ridgeback. I'll keep testing stems until I'm happy. I have an adjustable one I can play with too. Great fun for experimenting :)

DaveP wrote:All I have to do now is to come to a decision about the colour. Red? Blue? Custom... :lol:


I like green, it's the new black :)

DaveP wrote:Nice spacer BTW Ian - definitely the way to go once the washers have been counted!


I machined that from solid bar (FC1 alloy), the swarf probably weighs more than the spacer. You could do one easier if you could find a piece of stainless tube to fit over the steerer, that would just leave the ends to hacksaw and file. It's perfectly do-able, no reason to have a tower of spacers on your stem.
Iain



Ridgeback Genesis Day 2

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cranky
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Postby cranky » 17 Aug 2008, 6:13pm

Cunobelin wrote:I have a Hurricane Recumbent with "Tilt 'n' Steer" In upright mode the steering is direct, at full speed riding the bars are some 400 mm behind the column, more of a rudder.


I think the correct nautical term is 'tiller', the rudder's the bit that gets wet :)

Sorry Captain, I'll get me coat...

:)
Iain



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Cunobelin
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Postby Cunobelin » 17 Aug 2008, 6:16pm

cranky wrote:
Cunobelin wrote:I have a Hurricane Recumbent with "Tilt 'n' Steer" In upright mode the steering is direct, at full speed riding the bars are some 400 mm behind the column, more of a rudder.


I think the correct nautical term is 'tiller', the rudder's the bit that gets wet :)

Sorry Captain, I'll get me coat...

:)



Correct!

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Si
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Postby Si » 17 Aug 2008, 6:16pm

I vote "depends on the bike (and the rider)".

On many it will make little difference to if you lop a few cm off or add a few, for instance on my old tourer I went from 100mm to 50mm and handling was the same.

However, the more 'sporty' the bike the more chance that you will be able to feel the difference.

For instance, my fast road bike has the handling of a crit' bike - steering is much more hair trigger than my tourer. Changing the stem length made a noticable change to the handling. It didn't ruin the handling, and I soon got used to it, but for those first few rides I could notice it.