experimenting with stem offset

MinorThreat · Mar 9, 2011

'bout time. I'm still wondering why handlebar perches aren't forged into the top crowns to begin with.

big-ted · Mar 9, 2011

But seriously, didn't Azonic do this ages ago with a stem that clamped directly on top of the steerer tube, as this was before dual crown forks?

Curious to see how it works out though.

zdubyadubya · Mar 9, 2011

kinda similar to straitline's 28mm stem. its what i run. I like it. I like to get over the front of the bike alot (in a bad way) and it helps me to stay more balanced.

xy9ine · Mar 9, 2011

cesar_rojo said:
One last thing, with Ti bolts (all M6) is 64.5gr.

oh noes!

as a wc pro, what's your perspective on the heated topic of ti stem bolts? worthwhile performance gain or batsh1t insane?

klunky · Mar 9, 2011

azonic hammer stem

w00dy · Mar 9, 2011

This will put your hands behind the steering axis with the bar sweep. I get the feeling this will ride kinda funky, like a BMX with the bars back too far.

Nice solidworks work, though. Let us know how it works. I'm curious to hear how it actually feels.

Deano · Mar 9, 2011

the basic idea is sound i would say, but not everyone has the chance to test on both size frames to see what works.. but its great if you can test and let us know what you think about it

Tomasis · Mar 9, 2011

i think it is interesting idea going larger than one needs but with almost 0cm stem.

Myself I have a frame which is a bit short but I go for 63mm stem. Sort of reversed thinking

I usually get behind front wheel, but Im thinking that at quite slack headangle, 0cm is at advantage because one could to attack more in front also gets longer wheelbase.

I guess cornering will feel different with short frame/63mm and large/0mm.

Anybody tried that?

Tomasis · Mar 9, 2011

klunky said:
azonic hammer stem

I used to have this though it was a bit too high.

If I think more about it, it was not bad.

big-ted · Mar 9, 2011

klunky said:
azonic hammer stem

It was the O stem I was thinking of. Bars literally on top of the steerer tube.

RedOne · Mar 9, 2011

I went for a Race Face Atlas FR Stem on a large Summum for the same reason. Will mount it in the 30mm position, as soon as my Limited Edition Frame arrives (bored waiting).
Will be interesting to compare it to the pretty short Morewood Izimu with longer stem I rode the last years.

But changing bar height or fork length by sliding the stanchions through the fork crowns will be impossible with your stem especially with straight or low rise bars.

thom9719 · Mar 9, 2011

Cesar, I'm curious as to how you'll like this set up. I've gone back to a steeper headangle as I don't feel like I am getting enough weight over the front tire and feeling my front end slide out, especially in flat corners. I was riding a 62* head angle and am going back to 63.5 I've even gone the other way and run 55mm stems to extend the weight over the front wheel. When I really fight it and try and force my body forward, the front wheel seems to hook up better, but the goal is not to fight the bike. Also, I'm just shy of 6'3 so I'm already on a long wheel base bike, which makes the straight rough smashing a lot easier. That might be why I don't notice as much of a difference in the slacker head angles through the rough as someone on a small (short) frame would.

-KT

WBC · Mar 9, 2011

I went to a 30 mm stem, large frame, and steeper head angle this year, and I like it quite a bit. The wheelbase is similar to what I was riding before and the bike is just as confident on the steeps as before, but it turns more quickly when I need it to and I feel like I have more control hitting steep lips and more precision on super tech lines where you need your front wheel to go exactly somewhere.

It's that gary fisher genesis geometry!!

Commencal-guy · Mar 9, 2011

Wouldn't you want a longer stem on a slacker HA DH bike? to put more weight in the front when attacking the courses/ turning? Cesar can you enlighten your knowledge?

jon-boy · Mar 9, 2011

Yeah, seems a little bit backwards in logic to me too. I get that it will quicken the steering with the slack HA but I guess the shorter stem will make it easier to move your weight onto the bar and thus onto the front tire. I'd have to draw some diagrams on where the force is acting with that short a stem though..

Bikael Molton · Mar 9, 2011

big-ted said:
It was the O stem I was thinking of. Bars literally on top of the steerer tube.

everything about that photo is horrific.

Is that nasty stem on top of a threadless converter?

JCL · Mar 9, 2011

I'd like to run something similar but I'm not sure I have enough reach/stack in the frame. If you ride steep stuff it can only help to have more weight behind the front axle IMO.

Steve M · Mar 9, 2011

Commencal-guy said:
Wouldn't you want a longer stem on a slacker HA DH bike? to put more weight in the front when attacking the courses/ turning? Cesar can you enlighten your knowledge?

Imagine you drew up the geo of a DH bike, with a specific wheelbase, BB height, chainstay length and bar position (relative to the axles)... then just steepened the head angle by a degree or so (remember the Mondraker is MEGA slack) while keeping ALL the other points in the same places relative to each other. Seems to me that's what Cesar is trying to do by running a slightly longer TT, slightly steeper HA and shorter stem, and I think it makes sense to try - less trail without changing the weight bias of the bike.

- seb · Mar 9, 2011

Zero-length stems were all the rage 10 years ago - there were a few different options. We started at 130mm XC stems, decided shorter was better, right down to 0mm, and then a couple of years later it "stabilised" on 40-50mm ish.

I'm sure there were negatives to 0mm stems, but I never rode one so can't really comment. All of your theory sounds good to me though - my only query would be the actual steering. I can demonstrate what I mean with my arms in front of me and imagining a 0mm stem versus a 300mm stem (to exaggerate the effect) but struggling to put it into words. Your elbows need to do more work to pivot about a shorter stem. Or something like that

Of course we hardly ever turn the bars anyway really, biking's all about the lean as we all know. Let us know how it goes!

eatmyshorts · Mar 9, 2011

Clip ons could be interesting

sgarstin · Mar 10, 2011

Something to consider:

Length and slackness (including center of mass being rearward, acheivable with a shorter stem) will obviously give you stability in rough/steep.

When you hit a corner at the bottom of the rough/steep, suddenly that stability advantage compromises your ability to execute the corner, because the force of your weight on your front and rear wheel is stretched over a greater length (46" vs 49" wheelbase as a general example).

So when does it come to the point where the advantages of going faster in "rough/steep/whatever" stability are compromising your cornering speed? That is the question...

This is an important part of downhill courses, being able to come through a rough strait section with ample stability, whether it be steep or not, and then hit a corner fast and getting as much traction as possible.

Although shouldn't you be telling us Cesar?

Doesn't Fabien run a relatively long stem with very rolled forward handlebars? Do you still work and test with him?

trib · Mar 10, 2011

Have you experimented with custom crowns at all? Affects the rake and yaw(?) and all that. Not entirely connected to what you're trying to do but it seems odd that no one makes offset crowns to move the front axle. Well not anymore anyway

captainspauldin · Mar 10, 2011

trib said:
Have you experimented with custom crowns at all? Affects the rake and yaw(?) and all that. Not entirely connected to what you're trying to do but it seems odd that no one makes offset crowns to move the front axle. Well not anymore anyway

Couldn't the same effect be achieved w/an adjustable headtube(like what the mondraker has) or an angleset?

Pegboy · Mar 10, 2011

I think what he is trying to do is replicate the cockpit dimensions (length) of a medium frame with a slack head angle(62*), BUT increase the frame size (which he suspects will increase stability), and, steapen the head angle (which he suspects will offset the negative handling traits of riding a frame that is larger). So, no, this could not be achieved with just an angleset/adjustable headtube.

captainspauldin · Mar 10, 2011

Pegboy said:
I think what he is trying to do is replicate the cockpit dimensions (length) of a medium frame with a slack head angle(62*), BUT increase the frame size (which he suspects will increase stability), and, steapen the head angle (which he suspects will offset the negative handling traits of riding a frame that is larger). So, no, this could not be achieved with just an angleset/adjustable headtube.

Maybe I'm missing something, but couldn't you run a +1/1.5/2* sleeve or anglest to steepen the head angle/shorten the wheelbase?

Pegboy · Mar 10, 2011

Yep, you could and then you would have a bike that is less stable at speed which is the opposite of what he is trying to achieve.

Read the OP again and I think you will get it.

Pelle · Mar 10, 2011

I was thinking about trying this when I looked at getting a 2011 Demo. I wanted to try a medium size which are just a bit big for me and use the 28mm Straitline stem or make ones similar to what Cesar is gonna try.
I´m from moto and I don´t think it would feel wierd having the bar right on top of the crowns.

vinny4130 · Mar 10, 2011

i like the idea, i wanted to try a short stem before, i have the straitline shown i tried it on a giant glory ( I'm 5'7" glory was a med size) looked sick but i didn't like the handling. the front wheel on off camber turns would climb up causing me to lose the rear end, the first time was violently. this sounds like a dramatic affect but when i get something new and different i will try it on the same trail over and over this affect was consistent and happened in the same turn over and over body position helped but i continued to fight the front end; i went back to a 50mm problem solved.

i felt this was from a mix of 2 things the front end was now too short and my weight was back causing the front to wander more, and the dreaded steep head angle of the giant

.
Cesar i wonder about your thoughts on long top tube short stem/bar mount? i think the bar mounts look great!!! I also think your frames look sic, even better in person! i wish the frames were easier to get in the U.S.

-Vince

bullcrew · Mar 10, 2011

Stuck a canfield drop stem on and I think the lower height is a bigger imoprovement over length. It put my weight over the bars to push the front end down and doesnt wandrr as fast. Feels a bit more controlled, I was not all for the idea of it but it dropped into my lap the other day so I tried it and Ill be sticking with it... Doesnt have to be this particular one its the lower height that made the difference for me...

Steve M · Mar 10, 2011

captainspauldin said:
Maybe I'm missing something, but couldn't you run a +1/1.5/2* sleeve or anglest to steepen the head angle/shorten the wheelbase?

I don't think he wants to shorten the wheelbase... just steepen the head angle.

Sam B · Mar 11, 2011

captainspauldin said:
Maybe I'm missing something, but couldn't you run a +1/1.5/2* sleeve or anglest to steepen the head angle/shorten the wheelbase?

No... the two components of steering are head angle and fork offset (Note: assuming same wheel size / axle height). You can effect steering feel with different head angles or different offsets. I am not totally sure, but I believe the moto world is pretty set on head angle (around 64?) and adjusts fork offset more between different bikes.

Also... different forks have different amounts of offset. Small differences... but a 40 and a Boxxer are different. And back in the day... a Monster T had a ton more offset than the other forks on the market.

I am always interested to hear how peoples experiments work out, so I say go for it Cesar. Personally I would be into trying a shorter stem (more like 30mm but not 0mm) if I could run a slightly steeper head angle and a fork with less offset to keep my trail the same. Basically shorten the stem by whatever amount is necessary to keep the handlebar position the same with the steeper HA. Not talking a drastic HA change.... only a degree or two to bring it back closer to the 65 zone. I am currently around 63 I think...

captainspauldin · Mar 11, 2011

Socket said:
I don't think he wants to shorten the wheelbase... just steepen the head angle.

Gotcha so the only way would be w/a crown that moves the fork forward and at the same time steepening it.. I'm sure steepening the head angle 1-2* won't make a large shorter than or the same length as a medium, but i get it..

bizutch · Mar 11, 2011

The only logic of using that setup that I can think of is for a smaller rider wanting to ride a longer platform frame and still stay in a neutral position rather than too far forward. I was actually contemplating the opposite the other day.

With head angles tilting ever backward, it can make for a more crowded cockpit depending on the design. That would mean to achive the same reach and balance point for a rider on the same frame (slacker head angle), you'd need a LONGER stem.

Also, if you've got a 62 degree head angle and a 10mm reach stem, aren't you losing leverage on the front? It would take more input to get the wheel to turn.

Just random thoughts....

vinny4130 · Mar 11, 2011

bizutch said:
Also, if you've got a 62 degree head angle and a 10mm reach stem, aren't you losing leverage on the front? It would take more input to get the wheel to turn.

thats why you run 40" wide bars.

Jeremy R · Mar 11, 2011

Sam B said:
I am always interested to hear how peoples experiments work out, so I say go for it Cesar. Personally I would be into trying a shorter stem (more like 30mm but not 0mm) if I could run a slightly steeper head angle and a fork with less offset to keep my trail the same. Basically shorten the stem by whatever amount is necessary to keep the handlebar position the same with the steeper HA. Not talking a drastic HA change.... only a degree or two to bring it back closer to the 65 zone. I am currently around 63 I think...

That is what I did recently, and it made a huge difference to how I feel on the bike.
My dh bike has a long top tube for me and a 65 head angle. I went with the longer top tube so I could get some wheelbase length for stability. But the combo of a long top tube and a 50mm stem put me too forward on the front.
I slapped on a 35mm stem and was instantly pissed that I did not run it like that all last season. It feels perfect now.
It got my weight off the the front of the bike, and now it steers great with the short stem and 65 head angle, and the I still have the stability I need from the longer wheelbase.

rgrim · Mar 15, 2011

Good luck with the race and like the concept of a shorter reach mount. Have you played with rake at all?

experimenting with stem offset

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