Causes of Steering Wobble and Rattles

Preamble:
Having had a look earlier at the philosophy behind F1 vs Stock Cars Tyre designs, we had a glimpse last week behind reasons for constant need to maintain one’s tyre pressures ‘correctly’.

Contrary to what I said last week, I’ve just realised that I’ve already written about the importance of Wheel Balancing AND Alignment during the month of August ’07 itself. For those who tuned in later, please browse thro’ www.indiaautomobile.com/articles/archives/August.

So this week, let’s talk about other related issues, such as ‘Steering Wobbles’ and ‘Steering Rattles’…

Steering Wobbles

These are basically a) those occurring at cruising speeds and b) ones that occur at slower speeds, such as at take off and braking. While the former can largely be attributed to ‘dynamically-unbalanced’ wheels and to a lesser degree to ‘wheel-alignment’, the latter are caused by different reasons, such as – i) Unevenly worn front Tyres, ii) Out of true Wheel Rims, iii) Internally Damaged Radial Tyre Casing, iv) Worn-out Steering/Track Linkages/Suspension Bushes/Members, v) Damaged ‘Knuckle’ Joint, vi) Damaged Wheel End Axle Assy, vii) ‘Out of true’ Front Disc Brake Rotors, vii) Faulty/Worn out Caliper Assys OR sticky Hydraulic Piston/Rings thereof and viii) Defective Engine/GB Foundations, etc.

Steering Rattles

The real crunch here lies in identifying the source of such rattles as more often than not, with wear and tear setting in, a steering rattle gets sort of ‘progressive’ i.e. it can ‘shake’ other members of the ‘system’ into rattling which on their own may not! Such rattles can originate from one or more parts of the steering system as a whole.

Here’s how one can systematically analyse them, as those caused by – i) Premature wear of Tie-rod end/Rack ball joint: These can set in by ignoring the need to have all the five Wheels in good ‘dynamic balance’ all the time. This can be checked out by hoisting the vehicle on a 2-post lift and ‘yawing’ each front wheel horizontally - to ‘feel’ if there’s any slack around them; ii) Rack and/or Pinion wear: This again is a consequence of neglecting to keep one’s wheels in good balance all the times. These can be checked out by – a) parking the vehicle with wheels ‘st-ahead’ on a level ground and b) standing out side the driver side, gently rocking the steering wheel to the left/right. If there’s no slack per (i) above, then a slight steering wheel motion will reflect in front wheels’ motion also. If it doesn’t, it’s an indication of excessive slack between the rack and pinion. If it cannot be rectified by suitably tightening the rack ‘damper-bush’, the only remedy is to replace both with genuine parts at one go; iii) Rack ‘Bush’ Rattles: These are ‘softer-sounding’ in nature and can be pinned down by – a) parking the car on a level ground with engine off and b) ‘rocking’ the stg wheel gently. If one can hear soft thuds from the LHS end of the car even while sitting in the driver seat, the rack bush is the culprit and the only way to get rid of it is to replace with a genuine spare part; iv) St Column Rattles: These are relatively easier to identify as their origin is close by and one can hear them as ‘metallic’ in nature – may be extending upto the pinion. Since most Cars’ steering columns these days have ball bearings at its both ends, the main culprit of such noises is invariably the one or more of the ‘universal joints’ deployed between the steering column and the rack-pinion. This can be set right by getting the stg column suitably ‘tensioned’ at a skilled Garage.

With the foregoing trouble-shoot, most steering rattles can be overcome with lasting success. If not, one is left with no choice but to have one’s steering system suitably overhauled, including replacement of ‘all’ the wear prone parts at one go.

Cutting corners here is not advisable since a half-worn part which was otherwise ‘silent’ will now start rattling due to greater thrusts on it from the replaced/new parts!