Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) ��\�+���\$���X��A�(o^i�\$^���ozs��́�ɗ=ތz8�i���G�6 NK2���?��G�0����^��3o�0�{h�+] �혘��|ј� /Height 76 It is noted that the rate of change in scrub radius is reduced considerably which results in less tire wear and more stability . You could watch the … This creates a small tire/road friction resistance that in turn translates into feedback from the road. 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). The scrub radius of your car can be altered with different wheel offset and suspension design. x�| ��&��FD���Q�G�d������ x����i��3������m������x/���k���e�����`�_�t���P� )�d��y�Bי/����#̔U�י\$���d������l7�� @�mH� As with anything else, a little of a good thing is great, but lot of a good thing is not necessarily better. Positive scrub radius works well with suspensions that use dual control arms that use less caster and SAI to optimize geometry. This makes it heavy unless you move a bit too. stream Fig. << Braking in turn Steering effort : Scrub radius . A positive scrub radius tends to be beneficial while braking into a turn. REAR = Springs marked: HA, or (R), or Rear. Scrub Radius Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. /Length 133 ���r-���\��?�_P]Wf��)E��G�+� �j��� �c�P �wL�*� � >> ��.�HL����� 7 0 obj 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. 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. /Width 160 Tel. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. /Type /XObject The inclination of the KP axis in the side view is caster. A 5-6" scrub radius on these vehicles can lead to some pretty disconcerting drifts/pulls during hard braking and/or rough road conditions. �fYUz�ټ�d�U9��+M��챠p�VN��y� It could be positive, negative or zero. Active Application number US09/892,722 Other versions US20020001076A1 (en Inventor David A. Jackson 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. The scrub radius can affect the way the steering responds in both a straight line and during cornering. 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. /Mask 5 0 R 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. 5 0 obj 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. 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. With a small amount of scrub radius, the tire is turned about the kingpin axis, slightly offset from the tire’s centerline. /Type /XObject FRONT = Springs marked: VA, or (F), or Front. Scrub radius helps this feel by providing feedback from the contact patch. This is actually desirable to help counteract Toe-in forces caused by positive caster. << !mZ�Ͷ��5�x:n�(�7�|:��X�s^�XH�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�� The scrub radius can affect the way the steering responds in both a straight line and during cornering. /Height 76 n�o8,~�ʿ�~04�d����xW����38kVpc�Gi 祽�5���}2Z�8z�u�:嘤Lp�����^�/�!h�� 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. You can download the paper by clicking the button above. The parameters obtained from this axis are described in an earlier post. endstream 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. SU:Z���%;(� :���S1�KH���9���C�F�=�n��l4f� 2� � &෦�\$(��piʨAd{�h��9,����z#n1�3�X�����n� ��W� Sorry, preview is currently unavailable. Different wheels or the two modes will behave the same during nor- 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. /Subtype /Image /Filter [/FlateDecode /DCTDecode] 5.Instantaneous center: scrub radius is preferred and also too much of scrub radius either positive or negative results high steering kickback. /Height 222 /BitsPerComponent 8 Scrub radius : 10% . x�3zU��=�����*֟�;���?���2E���E�O����ZW��s~��,�gr����'�2��d�����đ8A7Q�ˢ_O�+�9+�z� Vq� ��|�;��/�4d����< Y�@�#� ��=� It also reduces the risk, that a lose of traction on one front wheel during braking, causes the car to change direction. 3 0 obj %�CKG������w����������������c��F�&�f�v������}`�}���ޅGDFEǤ��OK����UPXT�����K����Ʀo�-=�}��C�ߧ�gf��~"��76�����=:>9=;�����" �Σ��䫰�q�� /ImageMask true 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. }k ��hVD䘤� << /CreationDate (D:20121102074026-07'00') /Filter [/FlateDecode /CCITTFaxDecode] /Width 152 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 parameters obtained from this axis are described in an earlier post. 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. 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? /ColorSpace /DeviceGray If the scrub radius is small then the contact patch is spun in place when parking, which takes a lot more effort. 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-9b5T�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 proportional to the scrub radius, which will be felt by the driver at the steering wheel. 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. /BitsPerComponent 1 Fig 5 - scrub radius . !e�{�����������%���!����'}_@DTBB�+�(#� \$. endobj SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. 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. �������7��� /DecodeParms [null <>] Keeping scrub radius small will make the car easier to handle at low speeds. %PDF-1.4 /Type /XObject /Filter [/FlateDecode /CCITTFaxDecode] /DecodeParms [null <>] !��H� \$� Q�> �۠� �w�6!�܀J t���۷��q���~ ���]vQ�{�/ 9�� R ESEARCH ON MODELING AND OPTIMIZATION SIMULA TION ANAL YSIS … /Length 135 scrub radius is produced when braking and steering is unstable. I wonder if any one would have any thoughts on a problem I have. Academia.edu no longer supports Internet Explorer. SAI is an imaginary line, that on strut suspensions runs through the lower ball joints and the upper end of the strut. The main effect of this is to introduce a turning moment. /Producer (PDF-XChange 4.0.181.0 \(Windows Seven Ultimate Professional Service Pack 1 \(Build 7601\)\)) Trackwidth The Distance between centre axis of tire from front view is known as trackwidth. �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����� Its about changing the SAI/KPI to allow the wheel more inset over the hub so that the scrub radius is not excesive. ��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���). If it is inboard then the scrub radius is positive. d d d = 0 d Positive scrub radius Negative scrub radius . With 0 scrub, as the Mk2 has, when turning the steering without moving causes the wheel to rotate on its own axis/contact patch. /Width 160 VƥX@v'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!? >> 0.225 m StW radius, measured from centre to rim edge. To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. stream If the extrapolated KPI is outboard of the contact patch then the scrub radius is negative. What Is Scrub Radius? ?� ~��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�>`�� /BitsPerComponent 1 : +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. 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. endobj Camber Ca Definition Camber is … The apparatus includes a back-drivable steer-by-wire system including a road wheel actuator assembly coupled to a wheel of the vehicle. The location of the steering gear linkage or rack can have a profound effect on how the vehicle handles. /Subtype /Image The location of the steering gear linkage or rack can have a … Scrub radius is one of those often overlooked things. I cringe when I see 3" wheel spacers and a set of deep dish wheels to get full width, without changing the axle. endobj While the scrub radius itself is an important aspect of the overall setup (steering), there's more to it than "just" the scrub radius. /Length 6805 4% : Implementation of all the corrective actions, not only improved steering returnability by 40% but also helped in reducing the cycle time in design … %���� 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. Braking in turn Directional stability Scrub radius : 2% . �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. 6��l�XV����h^�۝��o+���R�� ��� 2) Which end of the spring is up? The inclination of the KP axis in the side view is caster. 6 0 obj In an embodiment of the present invention, an apparatus for steering a vehicle is disclosed. Fig.5 Trackwidth Geometry Note: Generally narrow (small) trackwidth are used at rear to avoid hit cones with the back when they are the scrub radius is distance between the kingpin axis and the center of the tire print on the ground [14]. I remember a long time ago with manual steering cranking the wheel to full lock while stopped. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. The kingpin axis is the line between the upper and lower ball joints of the hub. o�O���4hI�Y̆ЖB̒ܤ�nZ��ˮmVR�ZB��B[K^�?3"����㷼 ��A�yy��������I��oo����f��[¾U(�� �\G��7eK��r@]A��7�a�h�e3,��'���dsŮ��i݉8��������+�W��z����6}jii�YD�x3]�Nia���s���/�#ݒvT�z:_�������kk����#�{���啬W�� Page 1 of 2 - SCRUB RADIUS. �DG��_�Ø`��&uC�1�&ֳ�f�!@�jR0H�`iǤRLU�:���6?��1���̡2լ��Q��^JgKL�2d�36��! << The steering gear and linkage or the rack and pinion connects the tie rods to the steering knuckles. *���m���k���u��r ��a���1|1�~�|*�,P���dz�a�W\$��y�� x�uxuTT]��DBZ����i����v�\$\$��FB�K���TJ`H�߼�������u׺�S����g?�b�� �c m ]Q_Q vP� n�!�%! Fig.4 - Kingpin inclination angle . >> /Decode [1 0] stream The biggest effect is called bump steer. to 0 cm of scrub radius in the blow-out case. 8 inch wide wheels & a slightly narrower slick cured this. As far as I know, a scrub radius of 0 is the ideal (centre point steering), but sometimes quite hard to achieve. endstream /Subtype /Image We live & learn. Advertisement. 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. >> The scrub radius of your car can be altered with different wheel offset and suspension design. - posted in The Technical Forum Archive: Hi Chaps, can I ask a question please. 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. /ColorSpace /DeviceGray I.e. Enter the email address you signed up with and we'll email you a reset link. ���'IJz�!�o?r�o+ Negative scrub also helps reduce torque steer in front wheel drive cars. 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. 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