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Does a relaxed HT angle equal sloppy steering?

2K views 16 replies 6 participants last post by  his dudeness 
#1 ·
My 07 SJ FSR Comp lacks straight-line stability when traveling at slow speeds. The bikes straight-line stability improves with speed. For example, I can remove my hands from the handlebars and track straight when I am speeding down a hill or pedaling quickly on a flat surface. However; the opposite is true when my speed is under 10 MPG whereby removing my hands from the handlebars would cause the bike to steer left or right disrupting my balance. Compared to my old 04 SJ FSR, the 07 SJ has very little on center steering feel. I replaced the OEM SP-2 3x AHEADSET headset with a Cane Creek S-3, which did not cure the problem, although the S-3 bearings are noticeably smoother than the OEM AHEAD sealed bearings.

Is this lack of straight-line stability at low speeds caused by the frame's relaxed head tube angle? The HT angle for the 07 SJ FSR frame is specified as follows: 70.5 degrees for low/short, 69.5 for low/mid and 68.5 for low/long. I am not sure what the "low" notation means but 68.5 is a relaxed HT angle, which equates to a lot of positive caster on the front wheel. Is this why Gary Fisher came out with the G2 fork geometry to compensate for the lack of straight-line stability at low speeds?

The only other possible problems that can cause poor steering are frame alignment issues, unparallel HT ends, out of dish wheels, bent wheel axels, worn-out head set bearings, incorrect pre-load on the HS bearings or bent fork drop-outs. None of these problems are very like with a new bike that has never been in a wreck before-right?
 
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#2 ·
Wow, I think you've already figured it out. But I'd say yes -- thinking of an extreme example, like choppers. And yeah, I think that's what Fisher G2 claims to fix. Keeps the steeper HTA for quick steering, but increases the trail for stability at speed.

Edit -- I got G2 backwards - from Fish website:

"G2 Geometry started out as a project to improve the slow-speed handling of Fisher bikes. Fisher's existing Genesis Geometry already excelled in climbing, descending and handling at speed. The one area we wanted to improve its handling was in tight singletrack and technical climbs.

G2 accomplished this by increasing the amount of fork offset. This reduced the amount of trail to make it steer quicker without changing the rest of its handling characteristics. While increasing the offset, we reduced the reach to the handlebar to allow the rider to weight the front wheel more accurately.

The difference between too much trail and too little has been experienced by all of us. Think about going around a really sharp turn: take it too tight, and too slow, and you'll dab to the inside. You've oversteered.

Now think about the last time you over shot the same turn: you've understeered and ended up in the woods. Why does this happen? A good part of steering performance rests in the amount of trail. Too much trail and you'll oversteer (some feel this as wheel flop or dive) at slow speeds and understeer (overshoot the corner) at high speeds. Too little trail and you'll understeer at slow speeds and oversteer (feels twitchy) at high speeds. "
 
#3 ·
Another thing I noticed is that the bike favors turning left if I hold it still or walk the bike while holding the seat. I believe this left turn tendency is from my front brake caliper, which is mounted to my Fox Float RL fork with a 203mm adapter. This little weight (the caliper) hangs off the backside of the fork with a long bracket that slightly upsets the balance of the fork. All of the other bikes I owned had 160mm front disc brakes, which did not seem to upset the steering balance. I wonder if a large diameter heavy 203mm rotor contributes to this unbalanced steering response as well?
 
#5 ·
My xc bike is a Pitch with a upgraded Fox 36 on the front. The head angle is probably around 67.5 or so because the added travel and increased axle to crown height on the fox raises it higher than the Pike that it came with. Honestly, I haven't noticed any problems with the bike being unstable at any speed. The front end wanders a bit on steep climbs but its not a nuisance and is expected from the increased height of the front end (cranking in my talas would solve that problem if I cared). But cruising on flat ground she's straight as an arrow regardless of whether I have my hands on the bar or not. I'm running an 8 inch rotor in the front as well and haven't really noticed anything different than when I'd run a 6 inch rotor.

Are you really that peeved about having the bike wobble back and forth a bit when you're riding at 10 mph or less? Honestly, who cruises without hands at such a low speed? What variable you haven't thought of is that your seat height could be a bit too high, the resulting "wobble" side to side of your hips would very easily make your bike feel unbalanced at slow speeds. Is your stem straight and your headset properly installed? Also, keep in mind that any bike traveling at low speed has less momentum which creates less stability... If you are very slowly riding a bike without any hands that front end is going to do whatever it wants unless you've got the Jedi master balance skills. Slow speed and an unweighted front wheel:nono:.
 
#7 ·
I was running a 100mm x 15 degree Thomson Elite stem and Easton EA30 high rise handlebars on my XL frame until my last ride where I reinstalled the OEM 120mm stem and the OEM low rise handlebars. I was a little surprise to discover that 1) my hands and arms were more comfortable with the longer OEM 120mm stem and 2) the steering felt a little better (maybe because the handle bars are stiffer or the stem is a little longer). Still the 07 SJ's steering feels sloppy compared to my old 04 SJ FSR and just about all of the other bikes I remember riding.

Maybe the HT ends need to be refaced. However the cups are pressed up tight against the HT ends and the head set has never loosed up so I am not sure if refacing would do anything.
 
#8 ·
I think I may have found the problem, the top head set cup is not tight against the back side of the head tube. I discovered this by shinning a flash light around the HT and HS seam and eyeballing any light that bleed through joint. The gap is very small and will not allow my 0.08” feeler gauge into the opening. The front and sides of the top HS and HT do not seem to have any visible gaps and the bottom HT and HS joint also seems void of any spaces as well. Could this little gap cause steering problems?
 
#9 ·
You've got to be an engineer dude.


Ok, here it is AGAIN. Check your seat height, if your seat is too high then your hips WILL wobble and your bike will feel unbalanced with handling.

The headset interface with the head tube wouldn't cause any poor handling UNLESS you can tell that the headset is noticeably loose. Tighten your top cap down if that happens. When you installed your new headset (and I'm hoping that you installed it and not someone else) did the top cup slide easily in (like could you do it with your hand)? Or did it require a headset press and a bit of elbow grease to get it in? If the latter is the case then your headset was installed properly. If the headset was installed properly then your headset is NOT the problem.

What was the fork on the last bike you had? Older Stumpys had more of a xc feel whereas the newer stumpys have a more all mountain feel. I believe that the 07's have a longer travel fork in the front (I could be wrong), if thats the case your handling woes are caused by the longer fork as well as the taller axle to crown height.

I didn't even see you mention your tires, doesn't the 07 come with Resolutions? Throw on a knobbier tire front and rear, preferably with more of a square profile and a wider width... your bike will track in a straight line remarkably well.

How is your rear suspension set up? If its too soft (and it just might be regardless of what manual you used for your setup) the bobbing, no matter how minute will throw off the foward momentum and give you up/down side to side momentum.

What headtube setting do you have the frame set at? If its set to be slack, your bike will want to wander a bit, if you set your head tube angle to the steepest setting (70 degrees?) your front end will track better in a straight line.

Your body naturally has a dominant leg/arm, it will inevitably pull your bike in one direction regardless of how glassy smooth you can spin. Getting your bike to fit properly will help to alleviate this problem.

Instead of trying to find all the possible "what ifs" of why your bike doesn't cruise straight as an arrow at or below 10mph, why don't you just enjoy riding it at 11mph and above? You'll go mad trying to figure out the fact that you bought a bike with a 5 inch fork that is designed to handle descents confidently but maybe not slow speed "no hands" riding quite so well.

The more travel a bike has, typically the sloppier the handling will be, this is due to the length of the fork, the amount of rear travel, how the frame is designed, and the geometry of the bike. If you buy a slack geometry bike it wont be as "sharp" or on point as say an Epic which is designed to have excellent straight line tendencies so as to be the most efficient for racing.

And FYI... I have an Sworks Roubaix... a $8,000 road racing bike. Take your hands off the bars at 35 mph and she'll hold a line for days... try doing it at ten or below and your face will become best friends with the asphalt. And this is with a ROAD bike with a very experienced rider using it, not a mtb. Honestly dude, you're really worrying about something that you shouldn't have to worry about. If you want better straightline riding at low speed, sell the Stumpy and buy a hardtail... that'll be the straightest riding thing around if all you want to do is ride without hands at 10 mph or below.


I'm not trying to be a d!ck, and I'm not trying to make you feel like an idiot. But honestly man, just ride the bike. How often are you going to be mountain biking with no hands at or below 10 mph? Do you realize just how unsafe that is??? An unweighted front wheel and barely any momentum equals you not having a good time the second that front tire hits ANY obstacle in the trail, because you WILL crash. If you are mountain biking with no hands at that speed then I'm sorry to say it, but you are not using the bike to its abilities in any way and you are an idiot who will hopefully learn a valuable lesson very soon. If you bought this bike for your paper route or something... maybe you need a beach cruiser.
 
#10 ·
I almost forgot... yet again another pearl of wisdom.

If your 07 Stumpy is equipped with a brain, it's going to be located on the left side of the bike. Since the bike is therefore weighted more to one side... it runs the possibility of pulling to that side. Just more food for thought for ya.
 
#11 ·
It could be as simple as having the cables cut to an un equal length. Cables coming out of the shifters & brake levers will turn the wheel if not cut evenly. Put the bike in a stand with the front wheel down slightly and see where the bars stops. It will find it's own centered position based on the cable setup.
 
#12 ·
Unfortunately, my bike was not equipped with a Talas fork with adjustable travel, so I can not drop the travel down to100mm and test out the feel of a steeper HT angle.

Getting back to my gap between the top of the HT and the HS cup, I am not sure if the small gap is causing the problem because the fork-handle bars turn very smoothly throughout its 180 degrees of travel (no binding) and the HS has never loosened up.
 
#13 ·
bwalton said:
Unfortunately, my bike was not equipped with a Talas fork with adjustable travel, so I can not drop the travel down to100mm and test out the feel of a steeper HT angle.

Getting back to my gap between the top of the HT and the HS cup, I am not sure if the small gap is causing the problem because the fork-handle bars turn very smoothly throughout its 180 degrees of travel (no binding) and the HS has never loosened up.
When you're stopped and your feet are on the ground grab a handful of front brake and push foward on the handlebars. Rock back and forth on the handlebars, if you get a significant amount of play, popping, wobbling, creaking, etc then your headset could be the problem (and I said COULD, not that it is)... If thats the case then you need to give a huge middle finger to the bike shop that installed your headset, take it back and make them reinstall the thing... unless they've ovalized the head tube in which case you get a new frame. But you keep saying that the headset runs smooth and spins well, if your headset was loose enough that it would affect your handling you'd know it as soon as you touched the bike or picked it up (you'll hear a very obvious rattle of your fork inside the steerer tube). From hearing what you have said and not by seeing the bike in person I'm about 99% sure that the headset isn't your problem. This is coming from a guy who's been wrenching on his own stuff for 14 years and wrenching in bike shops for another 5 years or so.

But seriously man, you just keep posting your woes... why don't you post about our suggestions that you have tried? If you posted what has and hasn't worked for you then it'll be easier for us to decipher your problem. Have you tried anything that we've suggested? Or are you just still freaking out about your headset?

You might want to re-read your owners manual (very carefully this time). I believe the Stumpy's have adjustable geometry without having to use a Talas fork. My 06 Enduro was this way, as is the new Enduro SL, all the Demo bikes, SX trail, big hit, etc. I could have a steeper or more slack head angle by using a different shock shuttle or moving the shock to a different bolt hole in the linkage. Examine how your shock is mounted in the frame, is there a foward shock mount or rear mount that appears as though it could be removed and mounted back up in a different way? Where the shock mounts to the rear linkage is there a alternate bolt hole to use? If not then you just might have to get used to the fact that you bought a longer travel bike (companies will change bikes around here and there from year to year) and the more slack geometry will cause your front wheel to wander a bit.

My Pitch has six inches front and rear... it has been PRO built (as in every part was removed from the bike after it was pulled from the box and re-installed with proper torque settings and with facing the headset and bb), the bike couldn't possibly be built any better because it was built by not just me but with the assistance of friends at work who are professional race team mechanics. It has no creaks, no squeaks, and is sound as a pound. Honestly man this bike couldn't be built better by anybody else, by all means it is functionally PERFECT... but guess what? It still wobbles a bit side to side if I'm riding with no hands at low speeds. But why would this happen if the bike was built so well? I have 6 inches of travel, my frame is just a bit small so that when I'm on flats or climbs my extra tall seatpost changes the intended weight distribution for the bike (which means that my body puts a lot of side to side sway on the bike), also the geometry of the frame is designed around a 140mm (5.5 inch) fork while I put on a 150mm (6 inch) fork.

My Demo 7 is the SAME EXACT STORY. More so because the 7 inch fork is taller and the geometry of the bike is even more slack.

The problem is not the bike dude, you just gotta understand that. Hop on a epic sometime. The super steep geometry, short travel fork and rear end, stiffer suspension setup, and light weight will make it track straight at low speeds without hands on the bars. Yet your bike has an extra inch in the front, 3/4 of an inch in the back, has more suspension bob, weighs more, has more of an upright riding position and you can't seem to figure out that it's for these simple reasons listed above thats causing your bike to wander a bit. Due to the slack geometry and relaxed angles, you are putting more weight on the rear than the front... if you want your bike to track in a straight line better then put weight on the bar, that means put your hands on the bar. This isn't a problem or a defect or a fault with the bike, it is simply how it was designed. I really doubt that engineers sit up late at night and ponder on how to build the straightest tracking 5 inch mountain bike when the rider isn't using his hands on the bar. They're more concerned with climbing efficiency, descending prowess, making the thing weigh less than a boat anchor, and putting a smile on your face.

But really though, is it that much of a nuisance? What about when you have your hands on the bar and are flying through some twisty singletrack descent? I'll bet your bike goes EXACTLY where you want it. If you can't stop complaining then sell the bike and get a epic. It has less travel and more aggressive xc geometry versus the long travel and relaxed geometry of the Stumpy. I'm sure that for the collective1% of the time that you ride your bike with no hands at low speeds the epic will track much straighter. But the stumpy is going to be more fun for the other 99% of riding that you'll inevitably do with your hands on the bar. Otherwise, put a Talas on the front, or just buy a 4 inch fork... it wont be as fun as a five inch fork and it'll make your bike look and behave like a retard at Chucky Cheese, but it'll track pretty straight when you are hands free at or below ten miles an hour (apparently this is where you do the bulk of your riding anyway).

Look dude, I know my replies are long. But if you actually read them you'll see that you are worrying about something that isn't a big deal to worry about. Most mountain bikers with this type of bike experience the same exact thing as you. We just deal with it because the ten minutes of a bike ride where the bike wobbles a bit beacuse I'm riding no handed is nothing compared to the three hours of fun that I'll have with that straight tracking bike when my hands are on the bar. Does any of this make sense to you? I just feel like none of this is sinking in, you're severely beating a dead horse here.

Geez dude, just give me your bike. I'll happily ride it.
 
#14 ·
Ok, I saw a small hairline gap between the bottom of the HS cup and the top of the HT and measured that it was about 0.005". This gap was visible only on the back side of the HT, the front and sides of the HT had no visible gap. According to Cane Creek, the maximum allowable gap is two thousands of an inch or 0.002". Clearing something was wrong so I brought the bike in yesterday to have the HT faced. The Mechanic said he had to remove about 0.007" of material from both ends of the HT in order to get them to come out parallel.
The steering does feel a little better and more on center but it feels like it tracks on rails when I let all of the air out of the Float RL fork and steepened the HT angle by about 2 degrees to about 70 degrees. With 50 psi the fork sags half way through its 5" of travel and the HT is positioned to about 69 degrees and the bike still tracks very well and at 80 psi the HT angle is at 68+ degrees and the tracking starts to suffer. I wish I would have bought the Expert with the Talas, which I would have set to 100mm.
 
#15 ·
His dudeness, thanks for the detailed responses. All of my previous rides had HTAs of 70 degrees or steeper, which had a totally different steering feel than my current setup. It is amazing how 1 degree can effect the steering characteristic of a bike so much.

The Epic is the only dual suspension mountain bike that Specialized offers that comes with a 70 degree HTA anymore. Even the FSR XC HTA has been relaxed to 69 degrees along with a longer wheel base.
According Specialized the 07 SJ FSR should have a HTA of 69.5 degrees when the fork travel is set to 120mm. At 100mm the HTA is 70.5 degrees and at 130mm the HTA is 68.5 degrees. The 08 SJ FSR’s HTA is 68.5 degrees with the fork travel set at 120mm. So Specialized slackened the HTA for 08 even more than the 07 models.

I will order some spacers from Fox on Monday and reduce my Fork’s travel to 100mm and see how the steering feel improves. My rear shock has never compressed through it’s full travel, so the rear suspension seems to have an effective travel of 100mm with a 120mm travel fork up front. A 100mm fork should balance out the chassis .
 
#16 ·
bwalton said:
My rear shock has never compressed through it's full travel, so the rear suspension seems to have an effective travel of 100mm with a 120mm travel fork up front. A 100mm fork should balance out the chassis .
If you've never used all the travel, drop the pressure a little. If you're not occasionally using it all, what's the point of having it? Then just ride it -- give yourself a good chance to enjoy a bike with more travel both ends as designed. If you still don't like the SJ, yeah, you could change it, or try an Epic...
 
#17 ·
Yeah man, enjoy the bike for the way that it was intended to be. I'd give it a lot of riding time before deciding to cut down the travel. The frame was designed around a fork with that type of travel... you'd really only want it to be reduced if you were climbing. For general all around riding I'd keep the fork the way it is, it'll feel more balanced on descents (which is why we buy full suspension bikes). If you really have a problem with it, maybe see about swapping out for a fork with Talas down the road. Trust me, there will be times when you'll want full travel, and that bike is going to want to descend at its full travel to make the best use of its geometry... modifying your fork to 100mm will make you feel like you're going to go over the bars on most descents.
 
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