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this force with movement of its own. The motion amplitude for small duration and amplitude bumps is inversely proportional to the weight. A lighter wheel which readily rebounds from road bumps will have more grip and more constant grip when tracking over an imperfect road. For this reason, lighter wheels are sought especially for high-performance applications. However, the lighter wheel will soak up less vibration. The irregularities of the road surface will transfer to the cabin through the suspension and hence
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stages, with the unsprung mass tending to uncouple them. Likewise, sound and vibration isolation is improved (at the expense of handling), in production automobiles, by the use of rubber bushings between the frame and suspension, by any flexibility in the frame or body work, and by the flexibility of
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Pneumatic or elastic tires help by restoring some spring to the (otherwise) unsprung mass, but the damping possible from tire flexibility is limited by considerations of fuel economy and overheating. The shock absorbers, if any, also damp the spring motion and must be less stiff than would optimally
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The unsprung mass of a typical wheel/tire combination represents a trade-off between the pair's bump-absorbing/road-tracking ability and vibration isolation. Bumps and surface imperfections in the road cause tire compression, inducing a force on the unsprung mass. The unsprung mass then reacts to
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332:-type motorcycles use an integrated engine-gearbox-final drive system that pivots as part of the rear suspension and hence is partly unsprung. This arrangement is linked to the use of quite small wheels, further affecting their poor reputation for road-holding.
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from the brakes may overheat the differential or vice versa, particularly in hard use, such as racing. They also make anti-dive suspension characteristics harder to achieve because the moment created by braking does not act on the suspension arms.
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A beneficial effect of unsprung mass is that high frequency road irregularities, such as the gravel in an asphalt or concrete road surface, are isolated from the body more completely because the tires and springs act as separate
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damp the wheel bounce. So the wheels still vibrate after each bump before coming to rest. On dirt roads and on some softly paved roads, the induced motion generates small bumps, known as corrugations,
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High unsprung mass also exacerbates wheel control issues under hard acceleration or braking. If the vehicle does not have adequate wheel location in the vertical plane (such as a
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In this simplified diagram the wheels, tires, and suspension are all part of the vehicle's unsprung weight, with only its one-piece chassis/body constituting its sprung weight
326:(IRS) similarly reduced unsprung mass by replacing the upper wishbone arms of the suspension with the drive shafts, as well as mounting the brakes inboard in some versions.
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and road noise are worse. For longer duration bumps that the wheels follow, greater unsprung mass causes more energy to be absorbed by the wheels and makes the ride worse.
244:), vertical forces exerted by acceleration or hard braking combined with high unsprung mass can lead to severe wheel hop, compromising traction and steering control.
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or "corduroy" because they resemble smaller versions of the bumps in roads made of logs. These cause sustained wheel bounce in subsequent axles, enlarging the bumps.
172:(or weight) supported by the suspension, which includes the body and other components within or attached to it. Components of the unsprung mass include the wheel
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296:. He presented one of the first lectures taking a rigid analytical approach to suspension design, 'The Tyre as a part of the Suspension System' to the
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suspensions, in which wheels on opposite sides are connected as a rigid unit, generally have greater unsprung mass than
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Unsprung mass is a consideration in the design of a vehicle's suspension and the materials chosen for its components.
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used the driveshafts as suspension arms, thus requiring only the weight of one component rather than two.
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systems, in which the wheels are suspended and allowed to move separately. Heavy components such as the
204:(i.e. as on the drive shaft, and not part of the wheel or its hub) are part of a vehicle's sprung mass.
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can significantly reduce unsprung mass, but put more load on half axles and (constant velocity)
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168:(as applicable), and other components directly connected to them. This contrasts with the
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can be made part of the sprung mass by connecting them directly to the body (as in a
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The term 'unsprung mass' was coined by the mathematician Albert Healey of the
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Healey, Albert 3 (1925). "The Tyre as a part of the
Suspension System".
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in
November 1924. This lecture was published as a 100-page paper.
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Portion of a vehicle not supported by its suspension system
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60:. Unsourced material may be challenged and removed.
277:rear suspension). Lightweight materials, such as
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324:Jaguar's patented independent rear suspension
414:: CS1 maint: numeric names: authors list (
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120:Learn how and when to remove this message
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58:adding citations to reliable sources
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402:Institution of Automobile Engineers
363:"9: The Beginnings of Tyre Science"
298:Institution of Automobile Engineers
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852:Continuously variable transmission
369:. Dunlop Archive Project. p.
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367:The History of the Pneumatic Tyre
184:, and a portion of the weight of
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257:Unsprung mass and vehicle design
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45:needs additional citations for
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887:Automated manual transmission
494:Electronic Stability Control
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962:Semi-automatic transmission
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799:Internal combustion engine
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1098:Hybrid vehicle drivetrain
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987:Transmission control unit
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892:Electrorheological clutch
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196:, and suspension links.
877:Dual-clutch transmission
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847:Constant-velocity joint
361:Tompkins, Eric (1981).
827:Automatic transmission
267:independent suspension
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932:Locking differential
867:Direct-shift gearbox
240:supported by simple
54:improve this article
957:Preselector gearbox
937:Manual transmission
461:Automotive handling
294:Dunlop tyre company
1103:Electric generator
1008:Wheel hub assembly
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897:Epicyclic gearing
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71: –
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65:Find sources:
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43:This article
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32:
31:
19:
1045:Racing slick
982:Transfer box
952:Park-by-wire
947:Parking pawl
862:Differential
837:Direct-drive
819:Transmission
809:Steam engine
754:Part of the
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692:Trailing arm
614:De Dion tube
538:
474:Car handling
410:cite journal
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366:
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287:carbon fiber
275:de Dion tube
271:differential
260:
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242:leaf springs
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223:washboarding
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215:ride quality
211:
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52:Please help
47:verification
44:
1023:Alloy wheel
882:Drive wheel
872:Drive shaft
832:Chain drive
640:Independent
524:Tire / Tyre
499:Fishtailing
467:Main topics
397:Proc. Inst.
342:Sprung mass
253:the seats.
186:driveshafts
170:sprung mass
1108:Alternator
756:Automobile
745:Powertrain
687:Swing axle
677:Multi-link
653:Jaguar IRS
630:Twist beam
593:Suspension
534:Understeer
519:Suspension
312:waste heat
158:suspension
80:newspapers
977:Transaxle
942:Manumatic
912:Gearshift
784:Fuel cell
609:Beam axle
602:Dependent
578:Pneumatic
529:Transaxle
509:Oversteer
484:Downforce
263:Beam axle
238:live axle
232:car with
1151:Category
1136:Category
1075:Tubeless
1060:Run-flat
1040:Off-road
857:Coupling
779:Electric
660:Dubonnet
514:Steering
489:Drifting
400:London:
336:See also
279:aluminum
178:bearings
176:, wheel
110:May 2007
583:Torsion
330:Scooter
283:plastic
208:Effects
202:inboard
190:springs
156:of the
152:is the
150:vehicle
148:) of a
94:scholar
1126:Portal
1086:Hybrid
1050:Radial
1028:Hubcap
842:Clutch
789:Hybrid
758:series
559:Spring
377:
250:filter
198:Brakes
166:tracks
162:wheels
96:
89:
82:
75:
67:
1070:Spare
1013:Wheel
917:Giubo
595:types
561:types
348:Notes
182:tires
174:axles
101:JSTOR
87:books
1157:Mass
1065:Snow
1055:Rain
1035:Tire
573:Leaf
568:Coil
416:link
375:ISBN
318:The
236:, a
154:mass
140:The
73:news
1018:Rim
164:or
56:by
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412:}}
408:{{
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