SSM73888
Service Bulletin Details
Public Details for: SSM73888
Issue: low speed manoeuvring front tyre skipping phenomenon
- 2018 - 2017 - 2016 - 2015 - 2014 - 2013 - 2012 - 2011 - 2010 -
Models from 2018
| 2018 JAGUAR E-PACE |
| 2018 JAGUAR F-PACE |
| 2018 JAGUAR F-TYPE |
| 2018 JAGUAR XE |
| 2018 JAGUAR XF |
| 2018 JAGUAR XJ |
Models from 2015
| 2015 JAGUAR F-TYPE |
| 2015 JAGUAR XJ |
Models from 2014
| 2014 JAGUAR F-TYPE |
| 2014 JAGUAR XJ |
Models from 2013
| 2013 JAGUAR XJ |
Models from 2012
| 2012 JAGUAR XJ |
Models from 2011
| 2011 JAGUAR XJ |
Models from 2010
| 2010 JAGUAR XJ |
6/19/2018 SSM73888 - Low Speed Manoeuvering Front Tyre Skip / Jump phenomenon | TOPIx Reference SSM73888 Models E-PACE / X540 F-PACE / X761 F-TYPE / X152 I-PACE / X590 XE / X760 XF / X260 XJ / X351 Title Low Speed Manoeuvering Front Tyre Skip / Jump phenomenon Category Chassis Last modified 19-Jun-2018 00:00:00 Symptom 306000 Tyres/Wheels Attachments 1Picture 1.pdf Content Issue: Low Speed Manoeuvring Front Tyre Skipping Phenomenon Cause: Acute Ackerman angles employed to enhance driving experience Action:This SSM is a guide to explain the phenomenon of front tyre skipping while low speed manoeuvring with full lock applied to the steering causing a feeling of a slight jump, vibration or noise from the front tyres. This is NOT an error state. It is a result of geometry focused for higher dynamic higher cornering speeds, manoeuver, environment and tyre type. Geometry 100% Ackermann Geometry principle means that front lock angles allow for the radius of travel of both wheels to be defined by a common point through the rear axle. However in reality this principle cannot be achieved due to inner wheel lock angle constraints. Typically, vehicles have Full Lock Ackermann levels between 55 and 65%. More sports orientated vehicles have lower levels of Ackermann specifically to improve tyre utilisation. Manoeuver A benefit of low Ackermann can be found at higher cornering speeds when the tyres are generating slip angles. At very low speeds the tyres do not generate a slip angle which results in an aligning torque being applied to the tyres that is absorbed in the tyre. Tyre slip is exaggerated at high lock angles. https://topix.jaguar.jlrext.com/topix/content/document/view?id=902776 Environment 1/2 6/19/2018 SSM73888 - Low Speed Manoeuvering Front Tyre Skip / Jump phenomenon | TOPIx Tyre slip is more perceptible when the friction level between road and tyre is lower, I.e. when there is ice and snow, or when the road surface is wet. Or Brick, car park painted surfaces or concrete containing pea shingle may exacerbate the concern. Tyre Selection Changing the tyres from summer to all season or winter tyres may result in an improvement but there is a trade off in economy, road noise and tyre life. A customer experiencing this phenomenon can choose to fit an alternative tyre at their own expense. A benefit of low Ackermann can be found at higher cornering speeds when the tyres are generating slip angles (represented in picture 1 by the green arrows). More sports orientated vehicles have these lower levels of Ackermann specifically to improve tyre utilisation. Technicians - Please rate this SSM and provide comments so that future communications can be improved. 1 = Poor – Basic information provided – The SSM does not help me resolve the customer concern. 3 = Average – Adequate information provided – The SSM partially helps me resolve the customer concern. 5 = Excellent – All required information provided to resolve the customer concern. https://topix.jaguar.jlrext.com/topix/content/document/view?id=902776 2/2