Do slammed stems mean bike fits have gone out the window

Discuss light weight issues concerning road bikes & parts.
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themidge
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by themidge

mattr wrote:
Sat Aug 11, 2018 9:59 pm
themidge wrote:
Sat Aug 11, 2018 9:47 pm
but one had spacers and the other didn't, I'd say that the latter fitted 'better'.
You'd be "wrong" then. ;)

There is no benefit to having no spacers to achieve a fit. Within certain limits.
I never said there was a fit (position->rider) benefit to slamming the stem, just that a frame that fits without spacers technically fits (position->frame) better (spacers are a compromise). The only actual 'benefits' of a slammed stem are a slight increase in stiffness and better looks.

Edit: to put it another way, you wouldn't design a customs frame and use spacers, would you?

by Weenie


DamonRinard
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by DamonRinard

themidge wrote:
Sun Aug 12, 2018 10:56 am
...you wouldn't design a customs frame and use spacers, would you?
Hi themidge,

I would. Positions change.

Cheers,
Damon
Damon Rinard
Engineering Manager, Road Bikes
Cycling Sports Group, Cannondale
Ex-Kestrel, ex-Velomax, ex-Trek, ex-Cervelo

tarmackev
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by tarmackev

I’ve done a huge amount of fits on people over the years who should be on an endurance bike but who insist on an aggressive aero bike. 35mm of spacers with an stem ruin the look of any bike, especially aero bikes.
It does seem that slammed stems were more popular 5 or 6 years ago, also on bikeradar forum “show your bikes” section.
The comments are generally “screw the bike fit, just get rid of all your spacers”.


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mattr
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by mattr

I have. My custom frame is designed around 10mm of spacers to meet the nominal fit.
From a biomechanical/equipment perspective a fit with no spacers is a poorer fit.
It means you have no margin for injuries/changes in flexibility or changes to bars, stem, shifters. All of which have different shapes/reach/effect on stack.
The change in stiffness is miniscule, especially when you actually do the analysis. And a longer head tube (to meet your "no spacers" requirement) allows the steerer to flex more between the bearings anyway.
There is aslo a school of thought that says that slamming the stem adds a stress riser between the top cap and stem. I'm not sure how they get to that. But some manufacturers have recommended a spacer under the stem, then in the same way some recommend one above the stem, mostly ignored.......

mattr
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by mattr

tarmackev wrote:
Sun Aug 12, 2018 11:34 am
35mm of spacers with an stem ruin the look of any bike,
35mm of spacers is getting into "this bike is the wrong size/wrong bike" territory........

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ergott
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by ergott

DamonRinard wrote:
Sun Aug 12, 2018 11:16 am
themidge wrote:
Sun Aug 12, 2018 10:56 am
...you wouldn't design a customs frame and use spacers, would you?
Hi themidge,

I would. Positions change.

Cheers,
Damon
Right on.

jlok
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by jlok

I stopped buying bikes that I couldn't ride with stem slammed. e.g. the relatively long and low (at least for me) Aeroad is out of the question.
Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

mdeth1313
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by mdeth1313

mattr wrote:
Sun Aug 12, 2018 11:44 am
I have. My custom frame is designed around 10mm of spacers to meet the nominal fit.
From a biomechanical/equipment perspective a fit with no spacers is a poorer fit.
It means you have no margin for injuries/changes in flexibility or changes to bars, stem, shifters. All of which have different shapes/reach/effect on stack.
The change in stiffness is miniscule, especially when you actually do the analysis. And a longer head tube (to meet your "no spacers" requirement) allows the steerer to flex more between the bearings anyway.
There is aslo a school of thought that says that slamming the stem adds a stress riser between the top cap and stem. I'm not sure how they get to that. But some manufacturers have recommended a spacer under the stem, then in the same way some recommend one above the stem, mostly ignored.......
Also kills the resale value (if you think like that).
Speedplay is the devil!

mattr
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by mattr

Christ, i have enough issues with trying to actually give dickhead sellers money to ever get involved with actually trying to take money off them.

Haven't sold a bike in 20 years.

fogman
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by fogman

Bicycles are to be primarily ridden, not photographed. So someone buys one size larger frame size so he can slam his stem. Ends up with either a:
1. Short nubby seat post,
2. Short nubby stem which compromises handling,
3. Saddle slammed forward which puts the knee forward of the pedal axle.
4. Any combination of the above.

On the other hand, someone buys the correct size frame but still slams the stem. He now may be compromising power and comfort for aerodynamics and esthetics.



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It's all downhill from here, except for the uphills.

BdaGhisallo
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by BdaGhisallo

ergott wrote:
Sat Aug 11, 2018 4:23 am
alcatraz wrote:
Do you think the fit these pro's use when racing is what they or a top fitter would recommend for recreational riding?

/a
Not sure what you are suggesting. These are the most extreme positions for speed. Recreational riding would only mean a less extreme position and likely more spacers/less saddle to bar drop.

I also don't think they ignore comfort since they ride a full time jobs worth of hours in the position. I have a feeling when when they get off the bike after a hard day's work it's the legs that are sacked not their backs or neck. Again they have much higher w/kg than most so their legs are supporting their upper body.

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And let's not forget that the pros also have less upper body mass to support than the average fit enthusiast or racing cyclist. That will help them achieve and maintain a more "extreme" fit than the average amateur could sustain.

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Lelandjt
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by Lelandjt

wilwil wrote:
Fri Aug 10, 2018 11:15 am
Or are bike fits not as neceassary as they are made out to be and the body justs adjusts?
I've been saying this forever.

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Lelandjt
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by Lelandjt

AJS914 wrote:
Fri Aug 10, 2018 3:21 pm
. In reality they would be better off on a smaller frame with a couple of spacers and a longer stem.
Why is a long stem and spacers better than a short stem and no spacers? I assume we're saying the handlebar stays in the same position. I prefer the steering of a shorter stem and in theory no spacers on a longer headtube is stiffer and stronger than the opposite. The only downside I see to upsizing the frame is 50g more frame weight. 6'1.5" here on a 61cm with 110 stem slammed. I liked the steering with a 100mm stem better but I like the stretch with my new 110.

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tymon_tm
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by tymon_tm

Nefarious86 wrote:
Sun Aug 12, 2018 2:54 am
After 5 attempts at being "fit" including a go by the most respected bloke in the country for fit I still had pain every ride. Roll forward to cracking it and doing my own thing 40mm lower and 20mm longer and life is much better. I still get pain in my T5-6 at times but its 100% more manageable with a more stretched position. Image

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holy cow, I thought I'm the only one having similar issue - according to all the wisdoms of the cycling world, my bars should be at least 20mm higher and 10-15mm closer. but riding that way I feel like sitting on a kitchen stool peeling potatoes. even climbing with bars so high and so close feels awkward. and yes, I do experience lower back pain as well - mostly when I ride a lot in the drops, and for whatever reason (like climbing) stretch up for longer periods. however, if I stretch a bit while climbing, holding the shifters, all is fine and yummy.

and no, I don't think slamming is popular - I can't remember last time a saw anyone with a slammed stem, or a properly long one for that matter (I used to ride 130 and 140mm, but with Aeroad's geo 120 is enough)
kkibbler wrote: WW remembers.

by Weenie


istigatrice
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by istigatrice

fogman wrote:
Sun Aug 12, 2018 2:55 pm
Bicycles are to be primarily ridden, not photographed. So someone buys one size larger frame size so he can slam his stem. Ends up with either a:
1. Short nubby seat post,
2. Short nubby stem which compromises handling,
3. Saddle slammed forward which puts the knee forward of the pedal axle.
4. Any combination of the above.

On the other hand, someone buys the correct size frame but still slams the stem. He now may be compromising power and comfort for aerodynamics and esthetics.
Except this is less true on some smaller frames. The shorter stem doesn't affect the handling nearly as much as "bad" trail and front center. If you buy a bike to ride hard you want to make sure it doesn't throw up any handling surprises (and long trail + short front center results in nasty surprises for me).

Also there's nothing wrong with putting the knee forward of the pedal axle. In fact a new study has suggested this places less strain on the knee. It's all about how your body functions. My body doesn't respond well to setback because it tightens up my angles - I'm better off with a more forward position. Reference for the less strain in forward position: https://www.tandfonline.com/doi/abs/10. ... 18.1466906

So I agree that a bike is meant to be ridden but your other 4 points aren't true, especially for smaller riders and those with shorter legs and poor hip rotation.
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

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