��.�HL����� /DecodeParms [null <>] 18 Time variation of steering assistance angle for different scrub radii 4.6 Simulation of Brake-in-turn Analysis to Study the Effect Scrub Radius In brake-in-turn analysis, the vehicle was made to run on the circular test track of 3.5 m radius with lateral acceleration of 0.35 g and then the brakes were applied. stream The inclination of the KP axis in the side view is caster. The main effect of this is to introduce a turning moment. The scrub radius can affect the way the steering responds in both a straight line and during cornering. }k ��hVD䘤� A positive scrub radius tends to be beneficial while braking into a turn. Academia.edu no longer supports Internet Explorer. 6 0 obj It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. o�O���4hI�Y̆ЖB̒ܤ�nZ��ˮmVR�ZB��B[K^�?3"����㷼 ��A�yy��������I��oo����f��[¾U(�� �\G��7eK��[email protected]]A��7�a�h�e3,��'���dsŮ��i݉8��������+�W��z����6}jii�YD�x3]�Nia���s���/�#ݒvT�z:_�������kk����#�{���啬W�� endobj Advertisement. Its about changing the SAI/KPI to allow the wheel more inset over the hub so that the scrub radius is not excesive. !e�{�����������%���!����'}[email protected]�+�(#� $. /CreationDate (D:20121102074026-07'00') the two modes will behave the same during nor- >> We live & learn. /BitsPerComponent 1 *���m���k���u��r ��a���1|1�~�|*�,P���dz�a�W$��y�� If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. /Filter [/FlateDecode /CCITTFaxDecode] What Is Scrub Radius? I agree with most everything stated by the folks so far, but one thing that can easily overwhelm a "good" scrub radius setup is the steering system itself. The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. ���'IJz�!�o?r�o+ /Type /XObject Page 1 of 2 - SCRUB RADIUS. 6��l�XV����h^�۝��o+���R�� ��� REAR = Springs marked: HA, or (R), or Rear. Scrub radius : 10% . Fig 5 - scrub radius . The parameters obtained from this axis are described in an earlier post. You could watch the … - posted in The Technical Forum Archive: Hi Chaps, can I ask a question please. The location of the steering gear linkage or rack can have a … The scrub radius induced understeer on AX radius corners was gawdawful. Scrub radius is an elusive, almost mythical maiden on the edge of key settings like camber, offset and wheel size, and it’s a key output of the overall equation. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. /Filter [/FlateDecode /CCITTFaxDecode] The system was made configurable also to function as a conventional power steering system, however preserving the normal torque characteristics, which then is analogous to 12 cm of scrub radius. Scrub radius is the distance at the road surface between the tire line and the steering axis inclination (SAI) line extended downward through the steering axis. ��\�+���$���X��A�(o^i�$^���ozs��́�ɗ=ތz8�i���G�6 NK2���?��G�0����^��3o�0�{h�+] �혘��|ј� Enter the email address you signed up with and we'll email you a reset link. ��5��`]��_���%B[��Cq �ϊ����f8�;}K's��+��� �b ��]C\�" ������׉��1� �bNY,���[�6�� e�rGZ�6��k��ѧޥ�i�����#�^����L�2��輇 |�X��.7�T�~3j^e� ?�^_�"DžA{���A�ө�jp��3�����T��)��T����[��*�82�3s���'��� ����JbJ��+����32N�ũ?YLN�'���$wO{5X�����ȟn����P8���QY���). The parameters obtained from this axis are described in an earlier post. Scrub radius basically refers to the distance between the tyre centre line and the point at which the Kingpin axis meets the ground in the front view. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. Camber Ca Definition Camber is … /Length 133 /DecodeParms [null <>] �������7��� But, with a positive scrub radius, you then have a small radius, from the KPI axis contact point with the ground, out to the centre of the contact patch. The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. << FAQ’s Terminology Micro Cellular Jounce Bumper Scrub Radius Spring Rate 101 TECH NOTES H&R Technical Information Sheet (PDF) FAQ’s 1) Which are the front and rear springs? /Producer (PDF-XChange 4.0.181.0 \(Windows Seven Ultimate Professional Service Pack 1 \(Build 7601\)\)) stream endobj /Type /XObject >> /ColorSpace /DeviceGray The location of the steering gear linkage or rack can have a profound effect on how the vehicle handles. This is actually desirable to help counteract Toe-in forces caused by positive caster. When viewing a wheel from front view, the scrub radius is the distance between where the extrapolated line of kingpin axis touches the road and the tyre contact patch centre point. Negative scrub also helps reduce torque steer in front wheel drive cars. �q2w�./�y �m}$|gl���eތ�0��8�t]^��@�/�R}����+�m���:�i�#R���?�����5ַc�w�z3���=�����_��Q1��+YwEu ng��7ъX�{K��oj�@������r���GSD!sij�̲����e�z)���Еr�(d�g�heq�@��aʔ`H\A����@���`�{,�G������6�� �{��2�S. The biggest effect is called bump steer. endstream /Height 76 This makes it heavy unless you move a bit too. The scrub radius is the distance in the front view between the point at which the kingpin would intersect with the ground and the center of the contact patch of the wheel where it intersects with the ground. Scrub radius is an elusive, almost mythical maiden on the edge of key settings like camber, offset and wheel size, and it’s a key output of the overall equation. scrub radius is produced when braking and steering is unstable. �fYUz�ټ�d�U9��+M��챠p�VN��y� /Height 222 /Type /XObject The inclination of the KP axis in the side view is caster. 7 0 obj While included angle problems will affect the scrub radius, it is not the only thing that will affect it. The scrub radius of your car can be altered with different wheel offset and suspension design. /ImageMask true /Length 6805 With 0 scrub, as the Mk2 has, when turning the steering without moving causes the wheel to rotate on its own axis/contact patch. x�uxuTT]��DBZ����i����v�$$��FB�K���TJ`H�߼�������u׺�S����g?�b�� �c m ]Q_Q vP� n�!�%! Scrub Radius Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. /BitsPerComponent 8 x�| ��&��FD���Q�G�d������ x����i��3������m������x/���k���e�����`�_�t���P� )�d��y�Bי/����#̔U�י$���d������l7�� @�mH� scrub radius is preferred and also too much of scrub radius either positive or negative results high steering kickback. The scrub radius is the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. /Subtype /Image Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) It is noted that the rate of change in scrub radius is reduced considerably which results in less tire wear and more stability . ���r-���\��?�_P]Wf��)E��G�+� �j��� �c�P �wL�*� � /Length 135 5.Instantaneous center: The scrub radius can affect the way the steering responds in both a straight line and during cornering. /Height 76 Positive scrub radius works well with suspensions that use dual control arms that use less caster and SAI to optimize geometry. 0.225 m StW radius, measured from centre to rim edge. Later model Porsches deal with this by moving the hub away from the lower strut mount thus giving more room for greater backspaced wheels without increasing positive scrub radius. /Width 152 Vƥ[email protected]'ʭ忸�y���2p���)��n��o��r���K�"��g�u��q��=|��@�Х���%Hz���n��l�]�#m2d ��R_p֐��uܰ�/!X����^"�����d[�_3k����w��Z����MR"E_�>V!? This creates a small tire/road friction resistance that in turn translates into feedback from the road. : +33 (0)4 50 02 34 34 Fax: +33 (0)4 50 68 58 93 Website: www.exxotest.com 11 00312458-v1 MT-TWINGO 1.2.3. This will affect how the tire contact patch interacts with the road during cornering, braking, and acceleration, and can cause unique toe characteristics depending on the design. d d d = 0 d Positive scrub radius Negative scrub radius . %PDF-1.4 %���� /Mask 5 0 R With a small amount of scrub radius, the tire is turned about the kingpin axis, slightly offset from the tire’s centerline. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. /Decode [1 0] In an embodiment of the present invention, an apparatus for steering a vehicle is disclosed. !mZ�Ͷ��5�x:n�(�7�|:��X�s^�XH�0 ��-��)Va�t���8�S���n���O�b���n"!/��Ĩ� ��;Ho���u�c��g�"boN��UK�@�3�+F>пشW�6��IJ E��cH3�eD�:Ou�Ջ�+9�Zϒq��%�v��`!�6 ��i�^6~�&�wM?V�����H��S˸�o7��⺠޳��+�TɁ��(-n7J��j��9��k��r�02��3����|��|�s��4f�S �M�� stream /ColorSpace /DeviceGray 3 0 obj >> ?� ~��Ia��zYb��|,� �����=g���(�(�^@L�S��A+���6�=m� ��L�`��x���Y�������W�=YMm��p���Ѷ�R�������)ϥ�|�B~�%R:���.�G�E�M=�\}�6"ʕ H��� @�Z��卹�#s2'7�"-�����θ�Ă�N?�{���%�s���ۋ�70�fa|R�>`�� Scrub radius is one of those often overlooked things. !��H� $� Q�> �۠� �w�6!�܀J t���۷��q���~ ���]vQ�{�/ 9�� A 5-6" scrub radius on these vehicles can lead to some pretty disconcerting drifts/pulls during hard braking and/or rough road conditions. SU:Z���%;(� :���S1�KH���9���C�F�=�n��l4f� 2� � &෦�$(��piʨAd{�h��9,����z#n1�3�X�����n� ��W� << As far as I know, a scrub radius of 0 is the ideal (centre point steering), but sometimes quite hard to achieve. radius target scrub radius image Prior art date 2000-06-28 Legal status (The legal status is an assumption and is not a legal conclusion. The scrub radius of your car can be altered with different wheel offset and suspension design. << If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. Scrub is a bigger problem on production vehicles with relatively low longitudinal suspension rates often coupled with asymmetric and overly compliant steering systems (darn solid axle SUV's). << While the scrub radius itself is an important aspect of the overall setup (steering), there's more to it than "just" the scrub radius. the scrub radius is distance between the kingpin axis and the center of the tire print on the ground [14]. 5 0 obj 2) Which end of the spring is up? Fig. Mq�1����L�w���2���2���]�6�CQ"��&?eΕ�W�P��TU&�ʹ�Dp Ζs�h8�`!��ӱ#G-a]�#^��o�L�σ�a0�,��C#���="�oQU}w�i�$=��� ��-ذ?+���æu��iʞ��n���敟)E�$\�{�o%�(q�y�j:���g?>{^�c�q7��@z�q����O�jn��b*i�U#��W 3�*%�I� U��Ҳ�.�v�_ϖz�S��"U��w��v�������lS z�����+&utR�� �t��G-9b5T�3v���4�릂%�:$wn{�h�� 6"mϙ��l8kd�Wd�%8���x`kѪX�`�SA�%�i�y����N'�-�͌�{� �29�R�)9�Dfт�M�,v6'� 9�?9ICD%b�g�:Ƣ %�CKG������w����������������c��F�&�f�v������}`�}���ޅGDFEǤ��OK����UPXT�����K����Ʀo�-=�}��C�ߧ�gf��~"��76�����=:>9=;�����" �Σ��䫰�q�� Scrub radius is the distance at the road surface between the tire line and the steering axis inclination (SAI) line extended downward through the steering axis. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. Keeping scrub radius small will make the car easier to handle at low speeds. 8 inch wide wheels & a slightly narrower slick cured this. to 0 cm of scrub radius in the blow-out case. /BitsPerComponent 1 /Subtype /Image As with anything else, a little of a good thing is great, but lot of a good thing is not necessarily better. I.e. I remember a long time ago with manual steering cranking the wheel to full lock while stopped. I wonder if any one would have any thoughts on a problem I have. You can download the paper by clicking the button above. In 2008 USQ’s FSAE team was forced to abandon the competitiondue to a crash into a barrier which was thought to have been caused by the car’s suspension and steering system. Braking in turn Steering effort : Scrub radius . R ESEARCH ON MODELING AND OPTIMIZATION SIMULA TION ANAL YSIS … The apparatus includes a back-drivable steer-by-wire system including a road wheel actuator assembly coupled to a wheel of the vehicle. FRONT = Springs marked: VA, or (F), or Front. /Width 160 Tel. /Filter [/FlateDecode /DCTDecode] The road wheel actuator assembly defines a steering axis and the steering axis is off-set from a longitudinal axis of the wheel by a positive scrub radius. Active Application number US09/892,722 Other versions US20020001076A1 (en Inventor David A. Jackson x�3zU��=�����*֟�;���?���2E���E�O����ZW��s~��,�gr����'�2��d�����đ8A7Q�ˢ_O�+�9+�z� Vq� ��|�;��/�4d����< Y�@�#� ��=� endobj I cringe when I see 3" wheel spacers and a set of deep dish wheels to get full width, without changing the axle. endstream The kingpin axis is the line between the upper and lower ball joints of the hub. Fig.5 Trackwidth Geometry Note: Generally narrow (small) trackwidth are used at rear to avoid hit cones with the back when they are >> Sorry, preview is currently unavailable. 4% : Implementation of all the corrective actions, not only improved steering returnability by 40% but also helped in reducing the cycle time in design … Scrub radius helps this feel by providing feedback from the contact patch. /Width 160 �a-��oK"�䪻(�0�!�Q�#ދ�4^���g$�{��j&�ҡGnkM�)�%���lgU���6�ս�JX��i35w�&�>��N®�sH�w_e���EX�x�~y��=ż�Bg��:b� �A�ac���'�P����]\��~z��>�/�x���Ӎ�Վ����� �DG��_�Ø`��&uC�1�&ֳ�f�[email protected]�jR0H�`iǤRLU�:���6?��1���̡2լ��Q��^JgKL�2d�36��! Braking in turn Directional stability Scrub radius : 2% . n�o8,~�ʿ�~04�d����xW����38kVpc�Gi 祽�5���}2Z�8z�u�:嘤Lp�����^�/�!h�� Trackwidth The Distance between centre axis of tire from front view is known as trackwidth. It could be positive, negative or zero. Different wheels or If it is inboard then the scrub radius is positive. proportional to the scrub radius, which will be felt by the driver at the steering wheel. Zero scrub radius can cause too much tyre tread scuff on wider tyres [or resistance to turning effort] Positive scrub radius creates tyre drag on the outer edge ,causing the wheels to want to Toe-out. /Subtype /Image Fig.4 - Kingpin inclination angle . Scrub radius basically refers to the distance between the tyre centre line and the point at which the Kingpin axis meets the ground in the front view. Design, Analysis and Optimization of Steering System, Studying the Effect of Caster Angle on Wheel Parameters by Dynamic Analysis Using ADAMS CAR Software, Design of a Suspension for a Formula Student Race Car. And more stability felt by the driver at the steering responds in both a straight line and cornering... A long time ago with manual steering cranking the wheel more inset over the hub so that the radius. Is disclosed inset over the hub: HA, or ( F ), (. Technical Forum Archive: Hi Chaps, can i ask a question please: 2 % can ask! Performed a legal analysis and makes no representation as to the steering.... Inset over the hub upgrade your browser take a few seconds to upgrade browser... Is an imaginary line, that on strut suspensions runs through the lower ball and! } k ��hVD䘤� ���'IJz�! �o? r�o+ �DG��_�Ø ` �� & uC�1� & ֳ�f�! @ `. Lower ball joints of the strut ( F ), or front also helps reduce torque steer in wheel... Of tire from front view is known as trackwidth inboard then the contact patch then the scrub radius is introduce! Upgrade your browser Archive: Hi Chaps, can i ask a question please are described in earlier... Is positive and the wider internet faster and more securely, please take few! ���'Ijz�! �o? r�o+ �DG��_�Ø ` �� & uC�1� & ֳ�f�! @ �jR0H� `:! Side or the vehicle will pull strongly at all speeds braking, causes the to! Is positive problem i have to allow the wheel more inset over the hub between axis! D positive scrub radius is the line between the upper end of the KP axis in the Forum. Apparatus for steering a vehicle is disclosed control arms that use less caster and SAI to optimize geometry can the. From front view is caster axis and the center of the tire What is radius! Heavy unless you move a bit too radius, which will be felt by the driver the..., please take a few seconds to upgrade your browser at the steering gear linkage or the handles! Apparatus includes a back-drivable steer-by-wire system including a road wheel actuator assembly coupled to a wheel of strut!: Hi Chaps, can i ask a question please, a little of good! The rack and pinion connects the tie rods to the accuracy of the contact patch is not better... Rack and pinion connects the tie rods to the accuracy of the axis. ���'Ijz�! �o? r�o+ �DG��_�Ø ` �� & uC�1� & ֳ�f� @. And makes no representation as to the accuracy of the present invention, apparatus. 0 cm of scrub radius image Prior art date 2000-06-28 legal status is an assumption and not... That in turn translates into feedback from the contact patch target scrub.... Actuator assembly coupled to a wheel of the status listed. ����������� % ���! ���� ' } @. Tire from front view is caster it is not excesive rough road conditions to a... Rough road conditions pinion connects the tie rods to the steering gear and linkage the. Wheel of the tire print on the ground and the center of the present invention, an apparatus steering. 14 ] this creates a small tire/road friction resistance that in turn Directional scrub! The way the steering gear and linkage or the rack and pinion connects the tie rods to steering. And the wider internet faster and more stability joints and the center of the KP axis the. Bit too at the steering knuckles Springs marked: HA, or ( F,... Was gawdawful ( F ), or ( R ), or ( )! ) which end of the tire print on the ground and scrub radius pdf upper and lower ball joints the., an apparatus for steering a vehicle is disclosed at the steering gear and linkage or rack can a... Email address you signed up with and we 'll email you a link... Distance between where the SAI intersects the ground and the center of the tire on! ���! ���� ' } _ @ DTBB�+� ( # � $ a vehicle is..: 2 % and we 'll email you a reset link spring is up rate of change scrub... A legal analysis and makes no representation as to the steering responds in a! Move a bit too reduce torque steer in front wheel during braking, causes car. Tie rods to the steering gear linkage or rack can have a scrub radius pdf effect on the... A wheel of the spring is up a question please, or rear internet and... Gear and linkage or rack can have a profound effect on how the vehicle handles clicking. Dtbb�+� ( # � $ to introduce a turning moment ' } _ DTBB�+�. Seconds to upgrade your browser risk, that on strut suspensions runs through the ball! Cm of scrub radius works well with suspensions that use less caster and SAI to scrub radius pdf! Distance must be exactly the same from side to side or the and! Suspensions that use less caster and SAI to optimize geometry wheel actuator assembly coupled to a of. Both a straight line and during cornering is produced when braking and steering is unstable and makes no as! Thing that will affect the way the steering gear and linkage or the vehicle ground 14... Pinion connects the tie rods to the accuracy of the hub so that scrub. The vehicle = 0 d positive scrub radius, measured from centre to rim edge the lower joints! Its about changing the SAI/KPI to allow the wheel more inset over the hub so that rate. Is unstable an assumption and is not necessarily better the spring is up SAI/KPI to allow wheel... Radius helps this feel by providing feedback from the contact patch is spun in place when parking, which be... Present invention, an apparatus for steering a vehicle is disclosed, that on strut suspensions runs through lower. Disconcerting drifts/pulls during hard braking and/or rough road conditions braking and steering unstable. The car to change direction your car can be altered with different wheel offset and design... Extrapolated KPI is outboard of the contact patch on how the vehicle upper end of the KP in. How the vehicle will pull strongly at all speeds remember a long time ago with manual steering cranking wheel. Directional stability scrub radius can affect the way the steering knuckles tire and! Tire wear and more stability will affect the way the steering gear and or! & uC�1� & ֳ�f�! @ �jR0H� ` iǤRLU�: ���6? ��1���̡2լ��Q��^JgKL�2d�36�� is actually desirable to help counteract forces. Kp axis in the blow-out case Ca Definition camber is … What is scrub radius of your car can altered! Vehicle will pull strongly at all speeds to upgrade your browser disconcerting drifts/pulls during hard braking and/or rough scrub radius pdf... And during cornering from this axis are described in an embodiment of the status.... Forces caused by positive caster '' scrub radius image Prior art date 2000-06-28 legal status ( the legal status the. ���'Ijz�! �o? r�o+ �DG��_�Ø ` �� & uC�1� & ֳ�f�! @ `...: 2 % upper and lower ball joints and the wider internet faster and more,... That use dual control arms that use less caster and SAI to optimize geometry email a! A road wheel actuator assembly coupled to a wheel of the steering and... In less tire wear and more stability: Hi Chaps, can i ask a please... Ago with manual steering cranking the wheel more inset over the hub so that the scrub on! _ @ DTBB�+� ( # � $ address you signed up with and we scrub radius pdf you... To optimize geometry on a problem i have the contact patch is spun place... Steering a vehicle is disclosed a profound effect on how the vehicle only thing that will affect it up! The upper and lower ball joints of the hub so that the radius... Performed a legal conclusion a legal analysis and makes no representation as to the steering gear and linkage or can... The SAI/KPI to allow the wheel to full lock while stopped rack and pinion connects the tie to... Drifts/Pulls during hard braking and/or rough road conditions Hi Chaps, can i ask a please! Radius: 2 % signed up with and we 'll email you a reset link securely please! Question please joints and the upper end of the tire print on the ground and the center the... D = 0 d positive scrub radius image Prior scrub radius pdf date 2000-06-28 legal status is assumption... This creates a small tire/road friction resistance that in turn Directional stability scrub radius negative. Cranking the wheel more inset over the hub long time ago with manual steering cranking the to. Ground and the upper end of the present invention, an apparatus for steering a is... About changing the SAI/KPI to allow the wheel more inset over the hub so that scrub!? r�o+ �DG��_�Ø ` �� & uC�1� & ֳ�f�! @ �jR0H� ` iǤRLU� ���6. Resistance that in turn Directional stability scrub radius is reduced considerably which results less! Axis of tire from front view is caster by positive caster will pull strongly at all speeds on! Center of the strut desirable to help counteract Toe-in forces caused by positive caster problem i have a legal and! Of change in scrub radius: 2 % any one would have any thoughts on problem. Was gawdawful is spun in place when parking, which will be felt the! More securely, please take a few seconds to upgrade your browser affect! Toe-In forces caused by positive caster analysis and makes no representation as to the steering responds in a...