Received: from CIVE.RI.CMU.EDU by K.CS.CMU.EDU; 12 Jan 87 16:03:29 EST Date: Monday, 12 January 1987 16:02:57 EST From: Henning.Pangels@cive.ri.cmu.edu To: bovik@k.cs.cmu.edu Subject: tire balancing, static vs. dynamic Message-ID: <1987.1.12.21.1.3.Henning.Pangels@cive.ri.cmu.edu> My question on the general BB was: ---------- 10-Jan-87 09:37 Henning.Pangels tire balancing question From: Henning.Pangels@cive.ri.cmu.edu What are the differences between "static" and "dynamic" balancing? Pros and Cons? I have gotten some inconsistent information on this, so I'll have to try and get the answer via statistics by asking many people. Bovik doesn't seem to have the real scoop on this, but I'll forward any useful information I may get. ---------- ... and here are the replies I got. 43? 10 Jan 87 Fil.Alleva@speech... Re: tire balancing question (1041) 44? 10 Jan 87 Roy.Maxion@A.CS.C... Re: tire balancing question (521) 45? 10 Jan 87 Balas.Natarajan@H... balancing. (438) 46? 10 Jan 87 Hank.Walker@gauss... Re: tire balancing question (1079) 47? 10 Jan 87 John.M.Jourdain@M... wheel balancing (846) 48? 10 Jan 87 David Nason In-Reply-To: Henning.Pangels's bboard message of 10-Jan-87 09:42 It's simple (once you know the difference). Static balancing means that the tire is placed on a device that allows the mechanic to add weights to the rim of the tire until it is level with the ground (ie. all sides of the tire now balance the tire statically). Dynamic balancing means that the is tire spun up to road speed and with the aid of a strobe light the mechanic can figure out exactly where to place the weights so that tire is dynamically balanced to eliminate wobble and vibration introduced by the tire and wheel. A statically balanced tire might still vibrate a little. Dynamic balancing is better but more expensive and not normally nessecary for most small cars because the tires are smaller. ---- Message 44 (521 chars) is ---- Received: from A.CS.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 11:47:20 EST Date: 10 Jan 87 11:45:04 EST From: Roy.Maxion@A.CS.CMU.EDU Subject: Re: tire balancing question To: Henning.Pangels@cive.ri.cmu.edu I can answer your question, but it's just complicated enough that I'd really prefer it if you'd phone me. I can tell you in a few minutes. If you're looking for recommendations of what to do, get the tires balanced dynamically (if you have a car that you care about). Give me a call. Roy Maxion x7556 ---- Message 45 (438 chars) is ---- Received: from H.CS.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 14:11:30 EST Date: Sat, 10 Jan 87 14:05:25 EST From: Balas.Natarajan@H.CS.CMU.EDU To: henning.pangels@cive.ri.cmu.edu Subject: balancing. static balancing: balances moments about pivot dynamic balancing: balances moments of inertia about pivot. moment ~ mass x radius while moment of inertia ~mass x radius x radius bottom line is that tires need dynamic balancing. ---- Message 46 (1079 chars) is ---- Received: from GAUSS.ECE.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 14:35:26 EST Received: by gauss.ECE.CMU.EDU (4.12/4.7) id ; Sat, 10 Jan 87 14:35:24 est; Date: 10 Jan 1987 14:31-EST From: Hank.Walker@gauss.ECE.CMU.EDU Subject: Re: tire balancing question To: Henning.Pangels@cive.ri.cmu.edu@gauss.ECE.CMU.EDU Message-Id: <537305514/dmw@gauss> In-Reply-To: Henning.Pangels@cive ri cmu edu's bboard message of 10-Jan-87 09:56 Dynamic balancing is always better than static balancing. In static balancing, they put the wheel on its side on a pivot, and add weights here and there until it stays level. This is done by hand usually. In dynamic balancing, they mount the wheel on an axle in the normal position, and then spin it up. The wheel vibrates, and the vibrations are measured by the machine to determine where to put the weight. Most gas stations only do static balancing, while tire stores have dynamic balancing machines. Dynamic balancing is better because it measures the wheel under conditions similar to use. It costs more, but I always get it. ---- Message 47 (846 chars) is ---- Received: from ME.RI.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 14:37:33 EST Date: Sat, 10 Jan 87 14:22:02 EST From: John.M.Jourdain@ME.RI.CMU.EDU To: pangels@cive Subject: wheel balancing Leaving out all the technical details, when a wheel is statically balanced, it is put on a little stand which simulates the axle of your car and is balanced by adding little weights to the rim.(kind of like balancing a see-saw). When a wheel is dynamically balanced, it is actually spun, as it does on the car, and the balancing is done to eliminate any wobble when the wheel spins. It is possible for a wheel to be statically balanced, and still wobble like crazy when spun at a high rate of speed (like when you go 55 mph). I would advise that you always get your wheels dynamically balanced, even though there is sometimes an extra charge for it. -john ---- Message 48 (1229 chars) is ---- Received: from C.CS.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 15:06:31 EST Received: ID ; Sat 10 Jan 87 15:06:09-EST Date: Sat 10 Jan 87 15:06:08-EST From: David Nason Subject: Balancing To: henning.pangels@CIVE.RI.CMU.EDU Message-ID: <12269869491.39.NASON@C.CS.CMU.EDU> The basic difference is that static balancing is done while the tire is not moving (you've probably seen the tripod-like devices...the tire rests horizontally on a floating hub topped by a bubble glass like those in carpenter's levels...the guy puts lead weights on the edges of the rim until the bubble indicates level balance). Dynamic balancing is done while the tire is spinning. Some remove the tire and attach it to a machine. Others simply jack the car up a bit and roll a device containing a high-speed spinning wheel against the tire to start it moving. Various measurement devices are then used to check for wobble indicating balance problems. Some are better than others. Dynamic balancing is supposedly better in any case than static balancing. But I couldn't guess who you would ask for an "expert" opinion other than maybe a full-fledged tire dealer like Goodyear or Michelin. D. ------- ---- Message 49 (427 chars) is ---- Received: from BD.SEI.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 15:08:09 EST Date: Sat, 10 Jan 87 14:57:16 est From: dvk@sei.cmu.edu Message-Id: <8701101957.AA06857@bd.sei.cmu.edu> To: henning.pangels@cive Subject: Tire balancing Static balancing balances your tire while it is standing still. Dynamic balancing does it while it is spinning. Since your tire spends most of its time spinning, dynamic should be better. -Dan ---- Message 50 (764 chars) is ---- Received: from FARADAY.ECE.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 18:24:05 EST Received: by faraday.ECE.CMU.EDU (4.12/4.7) id ; Sat, 10 Jan 87 18:21:52 est; Date: Sat, 10 Jan 87 18:21:52 est From: Edward Czeck Message-Id: <8701102321.AA26824@faraday.ECE.CMU.EDU> To: Henning.Pangels@cive Subject: Tyre Balnacing Static Balancing balances the tire along the axail coordinate (z), this is ok but the tire is still lopsided along it rotational axis (theta). A dynamic or spin (or computer) balance balances along both the theta and z axises. The differences is felt by the ride (shakes in the steering wheel is usually a balance problem and not in alignment.) A spin balance is well worth the $3 or $4 you pay. Ed. ---- Message 51 (1496 chars) is ---- Received: from GAUSS.ECE.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 18:35:26 EST Received: by gauss.ECE.CMU.EDU (4.12/4.7) id ; Sat, 10 Jan 87 18:34:00 est; Date: Saturday, 10 January 1987 18:33:58 EST Sender: James.Fisher@gauss.ECE.CMU.EDU From: James.Fisher@gauss.ece.cmu.edu To: pangels@cive.ri.cmu.edu Subject: tire balancing Message-Id: <1987.1.10.23.26.11.James.Fisher@gauss> Hi. The following paragraph is quoted from a pamphlet I acquired the last time I visited Goodyear. TYPES OF WHEEL BALANCING: Tire and wheel assemblies can be balanced in two ways - statically and dynamically. In static (up and down) balancing, the assembly is mounted on a freely moving spindle. If, following rotation, one point on the tire and wheel assembly consistently pulls to the bottom, it has a heavy spot and weights are placed diametrically opposite to counterbalance this weight. If the assembly is not out of balance, it will stay at any position. On the car, a tire and wheel assembly that is out of static balance will thump and cause flat spots. Dynamic (two plane) balancing reveals whether a tire is unbalanced up and down, and also whether one side of a tire and wheel assembly is heavier than the other. Dynamic unbalance is reflected in a noticeable vibration sometimes described as @i[shimmy]. Dynamic imbalance is corrected by equalizing the weight on both sides of the tire and wheel assembly. Radial tires should always be balanced dynamically. Hope this helps. jim ---- Message 52 (657 chars) is ---- Received: from ML.RI.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 18:46:29 EST Date: 10 Jan 1987 18:45-EST From: Hans.Tallis@ml.ri.cmu.edu To: Henning.Pangels@cive.ri.cmu.edu Subject: Re: tire balancing question Message-Id: <537320707/tallis@ml.ri.cmu.edu> In-Reply-To: Henning.Pangels's bboard message of 10-Jan-87 09:42 Henning, In static they just put the wheel on a support and tack on weights until the thing balances. In dynamic they spinthe thing, typically (always?) using a computer to analyze it for inbalances. I think a while ago I read some reasonably independent source saying that dynamic was worth the extra couple of bucks per wheel. --Hans ---- Message 53 (2199 chars) is ---- Received: from ME.RI.CMU.EDU by CIVE.RI.CMU.EDU; 10 Jan 87 21:53:21 EST Date: 10 Jan 1987 21:34-EST From: Steven.Berman@me.ri.cmu.edu To: Henning.Pangels@cive.ri.cmu.edu Subject: Re: tire balancing question Message-Id: <537330898/berman@me.ri.cmu.edu> In-Reply-To: Henning.Pangels's bboard message of 10-Jan-87 09:42 Henning, The truth of the matter is that the static balacing is truly useless. I'll explain the differences: A tire balancing procedure is intended to even out the weight distribution on the axle/tire system by attaching small weights (1-8 ozs.) to the rim of the wheel hub. When properly balanced, a wheel system will not vibrate at high speeds. The vibration is due to harmonic resonance caused by the rotating wheel and an imbalance in weight distribution. Hence, when balacing a wheel, it is important to consider the entire wheel system with the axle. Since the axle/rotor (drum in case of drum type break on rear wheel) is never quite perfectly balaced, it must be included in the balacing procedure. Static Balace: 1) Wheel (tire and hub) are removed from car, and placed on a leveling machine. 2) A bubble level on the machine indicates weight imbalace. 3) Weights are attached to compensate. Dynamic Balace: 1) Wheel is left on the car. (This is @i[very] important!) 2) A machine is attached over the hub (like a hub cap) which allows the placement of varying weight around the circumeference of the hub. 3) A large motor spins the tire up to about the equivalent of 70 miles per hour. 4) Small controls on the front of the machine place weight on the hub, and are adjusted to eliminate vibration. The mechanic places his hand on the fender to feel the vibration. A good mechanic will repeat the procedure several times until no vibration is felt. 5) The wheel is stopped, and the machine has a pointer indicating where to place the weights, and how much to put on. Since the dynamic procedure balances the tire and axle systems, it is far superior. However, note that in doing this, if you rotate your tires, or change the tire, and replace it in a different rotational orientation, your balancing will be for naught. Good luck, -Steve- ---- Message 56 (1284 chars) is ---- Received: from C.CS.CMU.EDU by CIVE.RI.CMU.EDU; 12 Jan 87 09:51:52 EST Received: ID ; Mon 12 Jan 87 09:45:51-EST Date: Mon 12 Jan 87 09:45:47-EST From: Matt.Mason@C.CS.CMU.EDU Subject: dynamic balance To: henning.pangel@CIVE.RI.CMU.EDU Message-ID: <12270335460.14.MASON@C.CS.CMU.EDU> >From Symon, "Mechanics", Addison-Wesley 1971, p 446: "If a wheel is to spin freely without exerting forces and torques on its bearings, then it must be not only statically balanced, that is, with its center of mass on the axis of rotation, but also dynamically balanced, that is, the axis of rotation must be a principal axis of the inertia tensor, as any automobile mechanic knows." I doubt that automobile mechanics know about inertia tensors, but to get a true dynamic balance, you have to spin the tire. This might also explain why they put weights on both the front and the back of the wheel. If you just want to shift the center of mass, you wouldn't bother with the back of the wheel. But if you wanted to shift the principal axis of inertia, without shifting the center of mass, you would have to use the front and the back. As you might have guessed, I'm more than a little interested in the question. Could you forward any other responses you get? ------- ---- Message 59 (788 chars) is ---- Received: from A.CS.CMU.EDU by CIVE.RI.CMU.EDU; 12 Jan 87 11:51:37 EST Date: 12 Jan 87 11:45:26 EST From: David.Black@A.CS.CMU.EDU Subject: Re: tire balancing question To: Henning.Pangels@cive.ri.cmu.edu Static Balancing: The tire is balanced while sitting still; doesn't require any expensive equipment, but it's easy to screw up. Dynamic Balancing: The time is spun by a sensitive machine that detects any rotational imbalance and tells the technician exactly how much weight to add and exactly where to add it. The required machine is not cheap, so most places charge extra for this, but it's also almost impossible to screw up. Advice: get dynamic (or 'spin' balancing). Virtually all tire warranties are void if the tire wears out because it wasn't balanced properly. --Dave