reducing unsprung wieght

10 replies to this topic
  • tool

Posted August 13, 2004 - 04:08 PM


i was reading an article in MXA about unsprung wieght, and they were talking about a 6:1 theory. that being a one pound reduction in unsprung wieght is equal to a 6 pound reduction in sprung wieght. i dont know if thats true, but i would like to run the lightest tires and chain guide i can.
does anyone know anything about this subject? i.e, which tires are lightest, which chainguide and durable sprockets are the lightest, and does this improve handling or does it help the bike handle bumps better? :thumbsup:
i think im going to lose my brake gaurds at the track tomorrow ( :devil: ), to see if i feel any difference.
anyone know about this "unsprung" business?

  • Satch0922

Posted August 14, 2004 - 01:05 AM


Dunlop 756 is one of the lightest tires on the market. Also Renthal or any aluminum sprocket is the lightest (but less durable. Also Lightspeed makes a great Carbon Fiber chain guide.

The effects of unsprung weight are real. I did the old steel sprocket route a year or so ago and had to spend time dialing in my suspension again.....I went back to aluminum.

My thoughts are (especially on a thumper) if you have an option to replace a part with a lighter it. It all adds up.

  • tool

Posted August 14, 2004 - 12:59 PM


i agree, this is something i havent really noticed until recently. i am 170 pounds and i dont know if my riding style is sloppy or if i am overjumping my 426 too much, but i cringe when im going to bottom.
i dont think i can overcome the 20 pound wieght difference between my 00 and an 03 yzf. thats gotta help the suspension work better. the ergo's look much improved in addition to that.
anyone in colorado want a 426? :thumbsup:

  • INJURY_69

Posted August 14, 2004 - 02:49 PM


I want more theory, doesn't it have to do with revolution (spinning) or lower center of gravity or somethin' ?

  • Satch0922

Posted August 15, 2004 - 02:35 AM


"unsprung" weight is simply that. The weight or components of the bike that are NOT supported by the suspension.

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  • grayracer513

Posted August 15, 2004 - 11:45 AM


I want more theory, doesn't it have to do with revolution (spinning) or lower center of gravity or somethin' ?

Unsprung weight is weight that is not carried by the suspension of the bike. This includes both wheels, axles, brake calipers, and related parts, the lower fork legs, the oil in the forks, half the weight of the front springs (the top half is sprung weight), and the weight measured at the the rear end of the swing arm. The front of the swing arm is effectively supported by the sprung portion of the bike, as is nearly all of the weight of the rear suspension components of a modern MXer.

Unsprung components are those that must follw the contour of the ground, and thus must be allowed to move independently of the rest of the bike in order to do this. This motion needs to be controlled by the suspension in order to keep the wheels in optimal contact with the ground and give the rider the greatest possible control. The simple problem is that the heavier the unsprung components are, the more difficult it is to control them, making the suspension less efficient.

When a wheel hits a large bump, it has to roll up over it and then back down the other side. Ideally, it should never loose contact with the ground while this happens. If the wheel is heavy, its own intertia resists the bump raising it upwards, putting extra load on the tire and rim. once it gets to the top, a heavy wheel will want to keep going up off the top, and resist the efforts of the suspension trying to push it down along the ground. The same thing happens when the ground drops away from the bike. The suspension needs to be able to move the wheel down into the hole to maintain contact with the ground. Lighter components require less control, so the suspension can be "plusher" without sacrificing control.

Rotaing mass contributes more to a resistance to changes in speed (acceleration and braking) and to changes of direction than to suspension operation, but many of the same components are involved.

Center of gravity has more to do with how the bike above the wheels is built, and where the bulk of its mass is. Lower CGs make a bike easier to manage, but it is not a part of the unsprung weight issue.

How's that?

  • Satch0922

Posted August 15, 2004 - 12:00 PM



  • INJURY_69

Posted August 15, 2004 - 01:41 PM



  • tool

Posted August 15, 2004 - 03:53 PM


once again it is grayracer with the wisdom. :thumbsup:

i removed my aluminum brake gaurds (rotor and caliper), at the track for a back to back comparison. very noticable in the braking bumps. not very noticable when landing though.

  • grayracer513

Posted August 15, 2004 - 05:15 PM


Any idea what your disk guard weighs? 'Curious, you know.

  • tool

Posted August 15, 2004 - 08:00 PM


together, the disk gaurds wiegh about 3/4 of a pound. give or take. i also removed my bark buster at the same time. both made a big difference, but removing the disc gaurds definately had more of an effect. even though the bark busters probably wieghed more.

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