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MountainBikeReview.com's Forum Archives - Wheels & Wheel Building
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rank in order of significance, the following variables (7 posts)
|  rank in order of significance, the following variables | einke
Jun 12, 2003 9:44 AM | | that will make a wheel LATERALLY stiffer?
Increase spoke count
Increase spoke cross lacing (ie radial, 2x, 3x)
Increase spoke gauge
Increase spoke tension
Increase hub flange
Increase rim width
Increase rim depth
(and anything else I may have forgotten) |
| re: rank in order of significance, the following variables | seb at home
Jun 12, 2003 9:00 PM | | Based on the anylisis in Jobst Brandts book, I'd say the most signifigant by far it over all spoke stiffness.
That means thick spokes and / or more of them.
Increased rim width may spread the load over more spokes, but seems a poo reason to build using an otherwise unsuatable rim.
increases to hub flange and rim depth will improve bracing angle and decrease spoke length, which could help, but mostly in cases where bracing angle is so low as to cause trouble. The biggest gains are already past on a good MTB front wheel...
Increasde spoke cross also means increased spoke length and decreased barcing angle. Radial lacing thoretically gives the most lateral stiffness. An added bonus is that it allows all spokes to be "heads in", meaning you get an extra 2-4mm of flange width on half your spokes, for even MORE bracing angle, plus full lateral stiffness a all points on the rim.
Its hard to say just what good all that lateral stiffness will do yah, though. Lateral stiffness seems a pretty minor factor in bike handling. |
| radial lacing = stiffest?? | einke
Jun 13, 2003 3:36 PM | | Really? hmm... well, I'm asking because I have a mavic crosslink and the front wheel is so flexy it's driving me nuts. It's radially laced with 28 butted spokes (2 mm to 1.8 mm in the middle).
When I stand up to pedal, the wheel flexes so much that the rim rubs against the brake pads. It's so bad I can feel the resistance (let alone the annoying scrubbing sound).
I already swapped out the front skewer to a chromoly bolt on, but I haven't felt an increase in stiffness. The fork is a Judy XC from '99 so that may be contributing to part of the problem.
Would tightening all the spokes help? Would replacing the spokes with thicker spokes help? or should I just get a new wheel (I really like the gray anodized rims, they look so cool in the sun...)? |
| radial lacing = stiffest?? | seb at home
Jun 15, 2003 9:11 PM | | I built a 28 spoke radial with 2.0 / 1.8 DT spokes and ride it almost every day on my Singlespeed. The rim is a Sun 0ºXC, a sturdy but not outlandishly heavy XC hoop. The hub is xtr- very normal flange design.
The result is pretty dang stiff laterally. Considering I'm wrenching the bars for extra torque when I go up hills I'd think I'd notice the flexing- and I do, but that's about the only time, and its quite tolerable. It certainly doesn't cause the problems you mention. I did have some scrubbing, but it ended up my fork (a 99 manitou magnum, even lamer than yours) was cracked enough to let the stanchion rotate slightly! You may want to check that. I've a rigid fork now, and can run my pads less than 1mm from the rim.
I'm guessing therefore the problem with your wheel is not a design flaw. How heavy are you? I'm about 180, and more a spinner than a masher. I run a front wheel on my road bike that has 24 spokes that are even thinner, and again- its noticable that it flexes laterally, but not troublesome. The wheel handles abuse so well I'm considering it for cyclocross.
Unless your spokes are quite loose (very dull tone whem plucked), they are not going to decrease lateral stiffness.
Replacing the spokes with unbutted ones would make the wheel about 20% stiffer- reducing lateral movment under a given load 20%. Hardly sounds like its the solution to such radical flexing. A new whel with more AND thicker spokes might be called for.
Another common source of lateral rim displacment is impropperly adjusted cones / bearing tension. If the wheel can wiggle on its axle, its not gonna stay centered under a lateral load. A stiffer skewer won't help this, as a skewer is just a tension bolt that presses the fork blades against the cones. |
| radial lacing = stiffest?? | einke
Jun 17, 2003 8:08 PM | | strange thing is... I'm only 120 lbs! You'd think that issues like strength and flex wouldn't be a problem...
I've checked the bearing adjustments a number of times and I'm pretty sure they're properly tightened.
The wheel is so flexy that it rubs against the brake pads once I step out of the saddle (without even pulling on the bars). The only way I can get the wheel not to rub is if I TRY by applying the "wrong" pressure to the handlebars (which is kinda stupid... b/c I spend i more i energy and get i less i power, defeating the whole purpose of getting out of the saddle in the first place...)
anyway, I think it's time for a new wheel. Do you think I should go with 3 cross or radial? Which would be laterally stiffer?
thanks for the help seb. |
| try the wheel on another bike befre replacing | Seb
Jun 18, 2003 10:24 AM | | To me it sounds like it could be your fork at fault. Even without cracks, worn forks (w/ bad sliders) can "flex" a fair bit. A wheel flexing that much and not showiung any other failures just seems WIERD.
Try the wheel on another bike. If it does the same thing- well, I can't say why it would, but you might as well replace it.
A nice conservative bet would be 32 spokes laced 3 cross. It may not the thoretical max for lateral stiffness, but a solid bet for a durable wheel. It won't be much heavier than 28 spokes, and certainly no less flexy. Radial spokes really should be stiffer than 3x laterally, but the diffrence is small and the durability of 3 cross makes it a good choice.
As a light rider, you should be able to get away with light spokes and rims, so the wheel need not be more than a few grams wieghtier than a 28 hole radial.
Mike Garcia at Odds and Endos can surely hook you up with a light front hoop that won't wiggle around on yah- quite likely comparable to your current wheel, if not lighter. |
| didn't think of that | einke
Jun 19, 2003 5:56 PM | | good idea, i'll try it on my other bike... but then the other fork is a sid... well, i'll try it anyhow and let you know how it turns out.
thanks for all the help. |
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