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awkward steering on ~1990 mtb's with 26" wheels

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awkward steering on ~1990 mtb's with 26" wheels

Old 07-15-13, 06:52 PM
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TallRider
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awkward steering on ~1990 mtb's with 26" wheels

I have two large older mountain bikes (circa 1990, with 26" wheels), and they both feel funny when steering/turning, as if the front wheel is going to flop over instead of self-correcting, and I will lose control. It *feels* as if there is a narrow range of angles in which the steering will self-correct.
Of course this is not a problem with hands on the bar, but it means that I am uncomfortable riding no-hands on either bike. (I am generally very comfortable riding no-hands, to the point of sometimes sending emails from my phone while riding on a twitchy-handling road bike with crit geometry).

Has anyone else encountered this? What is it called and why does it happen?
The two bikes are a Diamondback Sorrento and some giant Panasonic, both low-end with horizontal dropouts and non-suspension fork design.


I figure there is some geometry issue here, but I don't know the proper term for it. I also don't know whether this type of steering is common to large bikes of that era, or perhaps has nothing to do with bikes of any size from that era. I may just have two large 26"-wheeled bikes with poor geometry.

The steering on both bikes feels this way if I put fatter or thinner tires (which will effectively change the trail value of the fork), so this feeling of steering is robust to tire size and it isn't just the result of a very specific trail value.
EDIT: the headsets on both bikes are in good shape and properly adjusted.
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Old 07-15-13, 07:01 PM
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If it's stable over at least a small range of angles then no-hands should be OK as long as the bike does not want to dive to one side. Turning no-hands of course is another issue. Those bikes may just have a rather slow response, or if they have knobby tires that could be part of the feel. I would not worry about it, especially as both act the same way.
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Old 07-15-13, 07:08 PM
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I haven't worried about it much, but I have always been curious what this is, what it's called, and why it happens. Hence this thread.

I am able to ride no-hands, but feel seriously weirded-out by doing so - that is, I'm not confident that it is stable over the small range of angles. My 1992 Trek 830 Antelope (a larger version of the one pictured here) never felt this way, nor has any other bike I've ridden. This is why I wonder if this steering has something to do with the era (1989 or 1990) or really large mtb's from that era.
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Old 07-15-13, 07:17 PM
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It's been a while since I've had a bike from that time period, but if anything I remember them being more stable with slower handling.

Dumb question, but are the headsets in good shape?
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Old 07-16-13, 09:00 AM
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My '88 Diamondback is like that. Lots of trail, so that it's really stable at speed, but it also has a lot of wheel flop at low to zero speed.
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Old 07-16-13, 09:38 AM
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You might measure rake, trail, and head angle, the compare with other bikes with different stabilities via test rides.
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Old 07-16-13, 09:47 AM
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High trail and flop are 2 sides of the same coin.

low head angle + what ever rake..

you may want to find out if the fork alignment is straight..

blades can be bent out of line ahead of each other and not equidistant at 50mm each, from the centerline.

might have been like that for 20+ years..



early MTB were a Cruiser bike with derailleurs, and rim brakes ..


I have a low trail, Folding bike , small wheels ,
Bike happens to really handle better with Weight on the front end..

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Old 07-16-13, 10:32 AM
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Pretty sure forks are aligned, although I haven't checked. The flop feeling is equal to either side, though. I'd consider it unlikely that two bikes of the same type/size/era have exactly the same misalignment issue, unless it's a design issue.

Perhaps what I am feeling is simply par for a low head angle and a large amount of trail? Combined with the fact that a 26" wheeled bike for a really tall guy puts the vast majority of the weight over the rear wheel.
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Old 07-16-13, 10:39 AM
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Trail is also something you can Measure. if it actually matters.

might be simpler to just not ride no hands , accept the handling for what it is.

Pragmatically, if that is the only bike you ride, changing to another bike will feel Odd.
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Old 07-16-13, 11:15 AM
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I don't expect to fix or change either bike, I just want to understand why they feel this way.

The strange feeling persists on both bikes whether run with smaller tires (which effectively decrease the amount of trail) or larger tires (which effectively increase the amount of trail). So I conclude that the feel of the steering is not highly-sensitive to the exact amount of trail.

I don't ride either of these bikes frequently. The Diamondback is setup as a singlespeed mtb (horizontal dropouts and all) and I'm not doing much no-hands riding in that context anyway. The Panasonic is going to be a singlespeed commuter in case I ever live in a flattish area, but there's more downside to the feel of the steering in that context.
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