BJ1042輕型載貨汽車前懸架設(shè)計(jì)【前雙橫臂獨(dú)立懸架】,前雙橫臂獨(dú)立懸架,BJ1042輕型載貨汽車前懸架設(shè)計(jì)【前雙橫臂獨(dú)立懸架】,bj1042,輕型,載貨,汽車,懸架,設(shè)計(jì),前雙橫臂,獨(dú)立 附錄A：英文翻譯 附錄A：英文翻譯 指出正確的方法 外傾角，后傾角和前束：它們是什么意思？ 汽車上三個(gè)主要校正參數(shù)是前束，外傾角和后傾角。大多數(shù)愛(ài)好者都能很好的了解這些設(shè)置的含義以及它們所涉及到的。但是很多人可能不知道為什么要設(shè)置這些特定的參數(shù)，或者它們是如何工作的。讓我們簡(jiǎn)單的了解一下懸架調(diào)整的一些基本的方面。 了解前束： 如果車輪設(shè)置時(shí)將它們的前面的邊緣互相靠近一點(diǎn)，這對(duì)車輪就叫做車輪前束。如果前緣互相遠(yuǎn)離，這對(duì)車輪就叫做負(fù)前束。前束的大小用車輪與車輪的平行線的夾角的大小表示?；蛘吒ㄋ椎恼f(shuō)，就是輪距在前緣和后緣的寬度變化的大小表示。前束的設(shè)置影響三個(gè)主要的方面：車輪的磨損，直線行駛的穩(wěn)定性和轉(zhuǎn)彎操縱特性。 為了減小輪胎磨損和動(dòng)力損失，當(dāng)汽車直線行駛時(shí)安在車軸上的車輪應(yīng)該指向正前方。過(guò)多的前束或者負(fù)前束導(dǎo)致輪胎的磨損，因?yàn)檫@對(duì)車輪總是相對(duì)行駛。過(guò)大的前束加速輪胎外側(cè)邊緣的磨損，相反的過(guò)大的負(fù)前束時(shí)導(dǎo)致車輪內(nèi)邊緣磨損。 所以如果零度的前束能減小輪胎的磨損和動(dòng)力，為什么還要前束角呢？答案示前束的設(shè)置對(duì)直線行駛的穩(wěn)定性有主要影響，上面的圖示展示了有關(guān)的機(jī)構(gòu)。由于車輪中心的控制，前束使車輪趨于向前交叉轉(zhuǎn)動(dòng)。在這種控制下車輪之間彼此之間運(yùn)動(dòng)不協(xié)調(diào)，就沒(méi)有了翻轉(zhuǎn)的后果。 當(dāng)一側(cè)車輪受到外界干擾時(shí)，這個(gè)車輪受到相對(duì)于車軸向后拉的力。這個(gè)運(yùn)動(dòng)同時(shí)也拉著另一側(cè)的車輪向相同的方向運(yùn)動(dòng)。如果干擾較小，這個(gè)受干擾的車輪將會(huì)變化很小，或者導(dǎo)致直線行駛而不是輕微的前束。但是注意輕微的轉(zhuǎn)向輸入，車輪的旋轉(zhuǎn)軌跡仍然不能描述變化。車輪吸收了路面的干擾而不使車輛改變行駛方向。這樣，前束提高了汽車直線行駛穩(wěn)定性。 如果汽車設(shè)置成負(fù)前束，但是，前輪平行以便輕微的干擾使這對(duì)車輪呈現(xiàn)轉(zhuǎn)動(dòng)的趨勢(shì)。并且每一瞬間中心位置的角度變換都將使內(nèi)側(cè)車輪比外側(cè)車輪有更小的轉(zhuǎn)彎半徑。因此汽車總是能轉(zhuǎn)彎進(jìn)入想轉(zhuǎn)彎進(jìn)入的地方，而不是直線行駛。所以很顯然負(fù)前束增強(qiáng)轉(zhuǎn)彎的趨勢(shì)，而前束減小這種趨勢(shì)。 前束汽車（左）懸架的偏轉(zhuǎn)不能像負(fù)前束的汽車（右）使車輪產(chǎn)生轉(zhuǎn)動(dòng)： 在特定的汽車上前束設(shè)置是在直線行駛穩(wěn)定性和快速轉(zhuǎn)彎能力之間的平衡。沒(méi)有人想讓他的車在柏油路上瘋狂左右徘徊的行駛并且不停的調(diào)整方向。但是賽車手們希望犧牲一點(diǎn)穩(wěn)定性而能夠快速的轉(zhuǎn)彎。因此城市汽車一般都設(shè)置成前束，而賽車都設(shè)置成負(fù)前束。 對(duì)于獨(dú)立懸架的汽車，前束也必需設(shè)置在汽車的后輪。前束設(shè)置在后輪上本質(zhì)上也會(huì)使輪胎磨損，產(chǎn)生方向穩(wěn)定性和轉(zhuǎn)彎特性，就像在前輪一樣。但是很少遇見(jiàn)在后論驅(qū)動(dòng)的賽車上在后論設(shè)置負(fù)前束的，因?yàn)檫@樣做會(huì)產(chǎn)生過(guò)多的過(guò)度轉(zhuǎn)向，尤其是當(dāng)動(dòng)力提供時(shí)。前輪驅(qū)動(dòng)的賽車，另一方面，經(jīng)常設(shè)置成一點(diǎn)負(fù)前束，這樣導(dǎo)致的過(guò)度轉(zhuǎn)向和過(guò)大的不足轉(zhuǎn)向相抵消。 同樣需要記住前束在汽車從靜止到運(yùn)動(dòng)會(huì)有輕微的變化。在獨(dú)立懸架前輪驅(qū)動(dòng)的汽車上應(yīng)該注意。當(dāng)驅(qū)動(dòng)轉(zhuǎn)矩加到車輪上時(shí)，車輪推著自己前進(jìn)并產(chǎn)生前束。這是另外一個(gè)原因?yàn)槭裁辞拜嗱?qū)動(dòng)汽車在前輪設(shè)置成負(fù)前束。同樣的，當(dāng)在公路上行駛時(shí)，非驅(qū)動(dòng)輪將產(chǎn)生負(fù)前束的趨勢(shì)。在后輪驅(qū)動(dòng)汽車上應(yīng)該被重視。 給定汽車上設(shè)置前束和負(fù)前束的大小由所屬的懸架和所期望的操縱特性決定。為了改善乘坐舒適性在公路汽車的懸架鏈接處安裝了有關(guān)的軟橡皮套，因此當(dāng)運(yùn)載時(shí)鏈接處的變化很均勻。相反的，賽車連接用鋼制的球形支承或者非常硬的氨甲酸乙酯。金屬或塑料的套管提供最適宜的硬度。和控制懸架連接剛度。因此，城市汽車比賽車要求更多的靜態(tài)前束。這樣在任何時(shí)候套管都能允許車輪呈現(xiàn)前束的情形。 應(yīng)該注意，設(shè)計(jì)師已經(jīng)用套管裝在普通汽車上來(lái)提升性能。為了使瞬間反應(yīng)最合適，有一點(diǎn)前束在后輪上來(lái)促使產(chǎn)生偏離角而在后輪上產(chǎn)生轉(zhuǎn)彎力是很好的。通過(guò)允許在A-arm懸架上側(cè)面鏈接的順從，后軸會(huì)有一點(diǎn)前束當(dāng)汽車進(jìn)入直角時(shí)，直線行駛沒(méi)有轉(zhuǎn)彎的道路上，套管仍然保持狀態(tài)并且允許前束設(shè)置一個(gè)角度使汽車車輪加速磨損和提高穩(wěn)定性參數(shù)。這種設(shè)計(jì)使一種被動(dòng)四輪轉(zhuǎn)向操縱系統(tǒng)。 后傾角的影響： 后傾角是一個(gè)主銷軸線相對(duì)于鉛垂線向前或向后傾斜的角度。如果主銷向后傾（上部被設(shè)置的比下部靠后），那么這個(gè)后傾角是有利的，如果向前則是不利的 當(dāng)汽車直線行駛時(shí)有利的后傾角有使車輪沿直線運(yùn)動(dòng)的趨勢(shì)，因此后傾角被用來(lái)提高行駛穩(wěn)定性。購(gòu)物車的車輪傾角用圖例更清晰的解釋這種裝置造成的趨勢(shì)。購(gòu)物車的轉(zhuǎn)向輪設(shè)置的車軸比車輪接地點(diǎn)靠前。當(dāng)車被推動(dòng)向前時(shí)，轉(zhuǎn)向軸拉著車輪前進(jìn)，當(dāng)車輪制動(dòng)時(shí)它就直接停在轉(zhuǎn)動(dòng)軸的后面。使車輪跟隨轉(zhuǎn)向軸的力是成比例的根據(jù)轉(zhuǎn)向軸和接地點(diǎn)距離——距離越遠(yuǎn)，力越大。這個(gè)距離被認(rèn)為是“主銷拖距”。 由于許多設(shè)計(jì)考慮因素，將汽車車輪轉(zhuǎn)向軸安裝在輪轂的正確位置是合理的。如果轉(zhuǎn)向軸設(shè)計(jì)成垂直的，軸線就與車輪接地點(diǎn)重合。拖距就是零，就沒(méi)有傾角。車輪本質(zhì)上就可以繞接地點(diǎn)自由旋轉(zhuǎn)（事實(shí)上，輪胎自己會(huì)產(chǎn)生一定的后傾角影響根據(jù)“氣胎拖距”現(xiàn)象但這種影響比機(jī)械式后傾角產(chǎn)生的影響小很多，因此忽略不計(jì)）幸運(yùn)的是只要傾斜前軸至有利的位置就可以產(chǎn)生后傾角。由于這樣的安排前輪的橫斷面與地面的交點(diǎn)在輪胎接地點(diǎn)之前，因此會(huì)產(chǎn)生與主銷后傾角一樣的效果。 從幾何學(xué)上考慮傾斜的前軸還有另外一個(gè)對(duì)懸架來(lái)說(shuō)很重要的作用。因?yàn)檐囕喯鄬?duì)于一個(gè)傾斜的軸旋轉(zhuǎn)，車輪當(dāng)其旋轉(zhuǎn)時(shí)會(huì)增加后傾角。這種效果最好想象成極限的情況當(dāng)前軸水平而轉(zhuǎn)向輪轉(zhuǎn)動(dòng)，車輪就很容易改變后傾角而不是保持方向不變。這種效果引起外側(cè)車輪轉(zhuǎn)動(dòng)產(chǎn)生不利的傾角，而內(nèi)側(cè)車輪獲得有利的傾角。這些傾角改變?cè)谵D(zhuǎn)彎時(shí)是有利的，雖然有時(shí)可能過(guò)大。 大多數(shù)汽車對(duì)傾角設(shè)置并不是很敏感。不過(guò)必須保證兩側(cè)車輪有同樣大小的傾角，從而避免汽車往一個(gè)方向行駛的傾向，這是很重要的。當(dāng)作用較大的傾角來(lái)提升汽車的直線行駛穩(wěn)定性，它們也同樣會(huì)提升轉(zhuǎn)向性能。3到5度的后傾角是典型的設(shè)置，而小角度后傾角用在重型車輛上來(lái)保持合理的轉(zhuǎn)向性能。 像購(gòu)物車的車輪的拖距是由轉(zhuǎn)向軸的后傾拉著車輪直線行駛形成的。 外傾角是什么： 外傾角時(shí)車輪相對(duì)于汽車垂直線的向前或向后的夾角。如果車輪向汽車方向傾斜，是車輪負(fù)外傾角，如果遠(yuǎn)離汽車傾斜是正外傾角。（請(qǐng)看下一頁(yè)）。車輪所能提供的回轉(zhuǎn)力在很大程度上取決于相對(duì)于地面的角度，所以對(duì)于汽車行駛性能來(lái)說(shuō)外傾角是一個(gè)主要影響參數(shù)。一個(gè)很小的負(fù)外傾角就會(huì)產(chǎn)生很大的回復(fù)力矩是很有意思的，主要在負(fù)1/2度左右時(shí)。它是由外傾角的推力提供的，這個(gè)力是由輪胎橡膠面與地面的接觸處的橡膠變形產(chǎn)生的側(cè)向力導(dǎo)致的 為了在轉(zhuǎn)彎時(shí)使輪胎的性能最優(yōu)化，懸架設(shè)計(jì)師們的工作需要設(shè)定輪胎的外傾角總是在一個(gè)負(fù)的小角度。這將是一個(gè)非常難的工作，因?yàn)樵谵D(zhuǎn)彎處底盤(pán)轉(zhuǎn)動(dòng)時(shí)懸架必需垂直地傾斜一定距離。因?yàn)檐囕喭ㄟ^(guò)一些鏈接與底盤(pán)相連，而這些鏈接必需轉(zhuǎn)動(dòng)才能使車輪轉(zhuǎn)動(dòng)，當(dāng)?shù)妆P(pán)上下跳動(dòng)時(shí)車輪會(huì)產(chǎn)生很大的外傾角變化。由于這個(gè)原因，車輪相對(duì)于靜止時(shí)的傾斜越多，保持一個(gè)穩(wěn)定的外傾角就越困難。因此，當(dāng)車輪較大或輪轂剛性較軟時(shí)對(duì)于設(shè)計(jì)者來(lái)說(shuō)在客車上提供平順的乘坐感是一個(gè)挑戰(zhàn)，而小車輪和高剛度的賽車就不會(huì)使設(shè)計(jì)師頭疼。 了解外傾角與路面和外傾角與底盤(pán)的大小的區(qū)別是很重要的。為了保持相對(duì)于地面理想的外傾角，懸架必需被設(shè)計(jì)成當(dāng)?shù)妆P(pán)向上傾斜時(shí)車輪相對(duì)于底盤(pán)的外傾角才能更加趨于負(fù)值。在46頁(yè) 下部的例子告訴了為什么是這樣的。如果懸架被設(shè)計(jì)成保持外傾角相對(duì)于底盤(pán)不變，那么車身轉(zhuǎn)動(dòng)就使外傾角相對(duì)于路面的正外傾角減少。因此，為了減少車身轉(zhuǎn)動(dòng)的影響，懸架必需被設(shè)計(jì)成靠近車輪的上部（也就是，獲得負(fù)外傾角）當(dāng)?shù)妆P(pán)向上傾斜。 當(dāng)懸架運(yùn)動(dòng)時(shí)保持理想的外傾角使輪胎有最高的效率，設(shè)計(jì)師們經(jīng)常配置乘用車的前懸架使獲得正外傾角當(dāng)車輪向上運(yùn)動(dòng)。這樣設(shè)計(jì)的目的是為了減少前邊緣相對(duì)于后邊緣的側(cè)向力，這樣汽車將會(huì)在得到最大的支撐時(shí)具有轉(zhuǎn)向不足。轉(zhuǎn)向不足比過(guò)多轉(zhuǎn)向更安全更穩(wěn)定，因此這樣對(duì)于量產(chǎn)的汽車時(shí)可取的。 因?yàn)槎鄶?shù)獨(dú)立懸架被設(shè)計(jì)成當(dāng)車輪相對(duì)于底盤(pán)上下運(yùn)動(dòng)時(shí)外傾角可變的，我們?cè)O(shè)置的外傾角當(dāng)我們校正的汽車不是典型的那種轉(zhuǎn)彎的汽車。然而，它真的是我們校正外傾角的唯一參考。對(duì)于比賽，在靜態(tài)下設(shè)置外傾角是必須的，測(cè)試汽車，在那時(shí)在方向上的靜態(tài)參數(shù)改變?cè)跍y(cè)試結(jié)果中會(huì)顯示出來(lái)。 為了比賽選擇合適的外傾角的就最好辦法就是當(dāng)輪胎還是熱的時(shí)候立即測(cè)量胎面的溫度曲線。一般而言，內(nèi)側(cè)輪胎邊緣比外側(cè)輪胎邊緣熱一點(diǎn)是合適的。但是，輪胎要能承受比理想的溫度曲線高的工作溫度是很重要的。因此，可以提供有利的額外的負(fù)外傾角使輪胎承受這個(gè)溫度。 （右上圖）正的外傾角：車輪的下部比上部靠的更進(jìn)。（左上圖）復(fù)外傾角：車輪的上部比下部靠的更進(jìn)》（中間圖）當(dāng)懸架傾斜時(shí)沒(méi)有外傾角，當(dāng)汽車轉(zhuǎn)彎傾斜時(shí)這會(huì)造成很大的正外傾角。這能使駕駛員操縱緊張。（下圖）沒(méi)有緊張感：在傾斜時(shí)獲得外傾角的懸架將補(bǔ)償車身的轉(zhuǎn)動(dòng)。協(xié)調(diào)動(dòng)力上的外傾角是懸架調(diào)整的神奇效果。 附錄B：英文原文 Pointed the Right Way Camber, Caster and Toe: What Do They Mean? The three major alignment parameters on a car are toe, camber, and caster. Most enthusiasts have a good understanding of what these settings are and what they involve, but many may not know why a particular setting is called for, or how it affects performance. Let's take a quick look at this basic aspect of suspension tuning. UNDERSTANDING TOE When a pair of wheels is set so that their leading edges are pointed slightly towards each other, the wheel pair is said to have toe-in. If the leading edges point away from each other, the pair is said to have toe-out. The amount of toe can be expressed in degrees as the angle to which the wheels are out of parallel, or more commonly, as the difference between the track widths as measured at the leading and trailing edges of the tires or wheels. Toe settings affect three major areas of performance: tire wear, straight-line stability and corner entry handling characteristics. For minimum tire wear and power loss, the wheels on a given axle of a car should point directly ahead when the car is running in a straight line. Excessive toe-in or toe-out causes the tires to scrub, since they are always turned relative to the direction of travel. Too much toe-in causes accelerated wear at the outboard edges of the tires, while too much toe-out causes wear at the inboard edges. So if minimum tire wear and power loss are achieved with zero toe, why have any toe angles at all? The answer is that toe settings have a major impact on directional stability. The illustrations at right show the mechanisms involved. With the steering wheel centered, toe-in causes the wheels to tend to roll along paths that intersect each other. Under this condition, the wheels are at odds with each other, and no turn results. When the wheel on one side of the car encounters a disturbance, that wheel is pulled rearward about its steering axis. This action also pulls the other wheel in the same steering direction. If it's a minor disturbance, the disturbed wheel will steer only a small amount, perhaps so that it's rolling straight ahead instead of toed-in slightly. But note that with this slight steering input, the rolling paths of the wheels still don't describe a turn. The wheels have absorbed the irregularity without significantly changing the direction of the vehicle. In this way, toe-in enhances straight-line stability. If the car is set up with toe-out, however, the front wheels are aligned so that slight disturbances cause thewheel pair to assume rolling directions that do describe a turn. Any minute steering angle beyond the perfectly centered position will cause the inner wheel to steer in a tighter turn radius than the outer wheel. Thus, the car will always be trying to enter a turn, rather than maintaining a straight line of travel. So it's clear that toe-out encourages the initiation of a turn, while toe-in discourages it. With toe-in (left) a deflection of the suspension does not cause the wheels to initiate a turn as with toe-out (right). The toe setting on a particular car becomes a tradeoff between the straight-line stability afforded by toe-in and the quick steering response promoted by toe-out. Nobody wants their street car to constantly wander over tar strips-the never-ending steering corrections required would drive anyone batty. But racers are willing to sacrifice a bit of stability on the straightaway for a sharper turn-in to the corners. So street cars are generally set up with toe-in, while race cars are often set up with toe-out. With four-wheel independent suspension, the toe must also be set at the rear of the car. Toe settings at the rear have essentially the same effect on wear, directional stability and turn-in as they do on the front. However, it is rare to set up a rear-drive race car toed out in the rear, since doing so causes excessive oversteer, particularly when power is applied. Front-wheel-drive race cars, on the other hand, are often set up with a bit of toe-out, as this induces a bit of oversteer to counteract the greater tendency of front-wheel-drive cars to understeer. Remember also that toe will change slightly from a static situation to a dynamic one. This is is most noticeable on a front-wheel-drive car or independently-suspended rear-drive car. When driving torque is applied to the wheels, they pull themselves forward and try to create toe-in. This is another reason why many front-drivers are set up with toe-out in the front. Likewise, when pushed down the road, a non-driven wheel will tend to toe itself out. This is most noticeable in rear-drive cars. The amount of toe-in or toe-out dialed into a given car is dependent on the compliance of the suspension and the desired handling characteristics. To improve ride quality, street cars are equipped with relatively soft rubber bushings at their suspension links, and thus the links move a fair amount when they are loaded. Race cars, in contrast, are fitted with steel spherical bearings or very hard urethane, metal or plastic bushings to provide optimum rigidity and control of suspension links. Thus, a street car requires a greater static toe-in than does a race car, so as to avoid the condition wherein bushing compliance allows the wheels to assume a toe-out condition. It should be noted that in recent years, designers have been using bushing compliance in street cars to their advantage. To maximize transient response, it is desirable to use a little toe-in at the rear to hasten the generation of slip angles and thus cornering forces in the rear tires. By allowing a bit of compliance in the front lateral links of an A-arm type suspension, the rear axle will toe-in when the car enters a hard corner; on a straightaway where no cornering loads are present, the bushings remain undistorted and allow the toe to be set to an angle that enhances tire wear and stability characteristics. Such a design is a type of passive four-wheel steering system. THE EFFECTS OF CASTER Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative. Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. The mechanism that causes this tendency is clearly illustrated by the castering front wheels of a shopping cart (above). The steering axis of a shopping cart wheel is set forward of where the wheel contacts the ground. As the cart is pushed forward, the steering axis pulls the wheel along, and since the wheel drags along the ground, it falls directly in line behind the steering axis. The force that causes the wheel to follow the steering axis is proportional to the distance between the steering axis and the wheel-to-ground contact patch-the greater the distance, the greater the force. This distance is referred to as "trail." Due to many design considerations, it is desirable to have the steering axis of a car's wheel right at the wheel hub. If the steering axis were to be set vertical with this layout, the axis would be coincident with the tire contact patch. The trail would be zero, and no castering would be generated. The wheel would be essentially free to spin about the patch (actually, the tire itself generates a bit of a castering effect due to a phenomenon known as "pneumatic trail," but this effect is much smaller than that created by mechanical castering, so we'll ignore it here). Fortunately, it is possible to create castering by tilting the steering axis in the positive direction. With such an arrangement, the steering axis intersects the ground at a point in front of the tire contact patch, and thus the same effect as seen in the shopping cart casters is achieved. The tilted steering axis has another important effect on suspension geometry. Since the wheel rotates about a tilted axis, the wheel gains camber as it is turned. This effect is best visualized by imagining the unrealistically extreme case where the steering axis would be horizontal-as the steering wheel is turned, the road wheel would simply change camber rather than direction. This effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber. These camber changes are generally favorable for cornering, although it is possible to overdo it. Most cars are not particularly sensitive to caster settings. Nevertheless, it is important to ensure that the caster is the same on both sides of the car to avoid the tendency to pull to one side. While greater caster angles serve to improve straight-line stability, they also cause an increase in steering effort. Three to five degrees of positive caster is the typical range of settings, with lower angles being used on heavier vehicles to keep the steering effort reasonable. Like a shopping cart wheel (left) the trail created by the castering of the steering axis pulls the wheels in line. WHAT IS CAMBER? Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber (see next page). The cornering force that a tire can develop is highly dependent on its angle relative to the road surface, and so wheel camber has a major effect on the road holding of a car. It's interesting to note that a tire develops its maximum cornering force at a small negative camber angle, typically around neg. 1/2 degree. This fact is due to the contribution of camber thrust, which is an additional lateral force generated by elastic deformation as the tread rubber pulls through the tire/road interface (the contact patch). To optimize a tire's performance in a corner, it's the job of the suspension designer to assume that the tire is always operating at a slightly negative camber angle. This can be a very difficult task, since, as the chassis rolls in a corner, the suspension must deflect vertically some distance. Since the wheel is connected to the chassis by several links which must rotate to allow for the wheel deflection, the wheel can be subject to large camber changes as the suspension moves up and down. For this reason, the more the wheel must deflect from its static position, the more difficult it is to maintain an ideal camber angle. Thus, the relatively large wheel travel and soft roll stiffness needed to provide a smooth ride in passenger cars presents a difficult design challenge, while the small wheel travel and high roll stiffness inherent in racing cars reduces the engineer's headaches. It's important to draw the distinction between camber relative to the road, and camber relative to the chassis. To maintain the ideal camber relative to the road, the suspension must be designed so that wheel camber relative to the chassis becomes increasingly negative as the suspension deflects upward. The illustration on the bottom of page 46 shows why this is so. If the suspension were designed so as to maintain no camber change relative to the chassis, then body roll would induce positive camber of the wheel relative to the road. Thus, to negate the effect of body roll, the suspension must be designed so that it pulls in the top of the wheel (i.e., gains negative camber) as it is deflected upwards. While maintaining the ideal camber angle throughout the suspension travel assures that the tire is operating at peak efficiency, designers often configure the front suspensions of passenger cars so that the wheels gain positive camber as they are deflected upward. The purpose of such a design is to reduce the cornering power of the front end relative to the rear end, so that the car will understeer in steadily greater amounts up to the limit of adhesion. Understeer is inherently a much safer and more stable condition than oversteer, and thus is preferable for cars intended for the public. Since most independent suspensions are designed so that the camber varies as the wheel moves up and down relative to the chassis, the camber angle that we set when we align the car is not typically what is seen when the car is in a corner. Nevertheless, it's really the only reference we have to make camber adjustments. For competition, it's necessary to set the camber under the static condition, test the car, then alter the static setting in the direction that is indicated by the test results. The best way to determine the proper camber for competition is to measure the temperature profile across the tire tread immediately after completing some hot laps. In general, it's desirable to have the inboard edge of the tire slightly hotter than the outboard edge. However, it's far more important to ensure that the tire is up to its proper operating temperature than it is to have an "ideal" temperature profile. Thus, it may be advantageous to run extra negative camber to work the tires up to temperature. (TOP RIGHT) Positive camber: The bottoms of the wheels are closer together than the tops. (TOP LEFT) Negative camber: The tops of the wheels are closer together than the bottoms. (CENTER) When a suspension does not gain camber during deflection, this causes a severe positive camber condition when the car leans during cornering. This can cause funky handling. (BOTTOM) Fight the funk: A suspension that gains camber during deflection will compensate for body roll. Tuning dynamic camber angles is one of theblack arts of suspension tuning. TESTING IS IMPORTANT Car manufacturers will always have recommended toe, caster, and camber settings. They arrived at these numbers through exhaustive testing. Yet the goals of the manufacturer were probably different from yours, the competitor. And what works best at one race track may be off the mark at another. So the "proper" alignment settings are best determined by you-it all boils down to testing and experimentation. John Hagerman is a mechanical engineer who works for the U.S. Army as a vehicle test engineer at the Aberdeen Proving Grounds in Maryland. John started autocrossing at the age of 16 in a Triumph Spitfire and switched to road racing a few years later. Lately, he has been playing with a Sports 2000.