When the suspension is out of air

Technology & Knowledge
April 27, 2022 2 min read

BILSTEIN advises: Observe the correct tightening torques

 If air suspensions do not appear to be completely tight after a repair, this can be due to quite banal reasons. Defective spare parts are rather uncommon. However, the devil is in the details and defects can often occur if the specified tightening torques have not been observed. The BILSTEIN Academy explains the points to which attention must be paid.

Replacing air springs or air suspension modules is neither rocket science nor a mystery. Nevertheless, there is a small checklist for workshops to follow to ensure that no mistakes are made in the heat of the moment. At the top of the list: Never lower an air-suspended vehicle to the ground with the lifting platform while the system is still depressurised. Failure to do so could cause irreparable damage to air springs or air suspension modules. However, there are also expensive consequences in other areas. Incorrectly selected tightening torques are enough to cause leaks.

„Compressed air connections and residual pressure valves are particularly tricky.“

Rainer Popiol, Head of the BILSTEIN Academy

However, the correct tightening torques should be meticulously observed also for the remaining connections. There are no standard values, but the usual range is between 2 and 5Nm. A torque wrench with this setting range can therefore be selected from the tool trolley before starting repairs. The mechanic can find out the exact values from the vehicle manufacturer’s documentation for each vehicle. Since the specifications can change over the course of time, for example due to technical modifications, it is essential to ensure that the data is up to date.

To prevent leaks, vehicle manufacturers generally specify very precise torque requirements for all connections on air springs and air spring modules. Under no circumstances should these be undercut, otherwise connections could become loose – or they may not be completely airtight.

Tightening them too much can be just as dangerous, as it can damage seals. Even small leaks can cause expensive consequential costs for air suspension systems – even if they are not noticed during driving. The compressor has to work permanently against a gradual loss of pressure and thus wears out more quickly. By the way: Replacements for defective OE compressors are available from BILSTEIN‘s B1 programme.

Photos: Copyright BILSTEIN 2022. Reproduction free of charge if source is named. 

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