Below is a selection of helpful descriptions to some FAQ's and common problems associated with clutch and braking systems.
Commonly felt under braking conditions as a shaking steering wheel or pulsing through the vehicle, brake shudder/judder is a common issue among many vehicles. It is commonly referred to as disc thickness variation or DTV. There are a number of causes including unevenness of mounting hub/flange, caliper piston/slide pin issues, brake pad material transfer, uneven torqueing of wheel nuts, etc. It is critical that all these above items are checked, cleaned and lubricated where applicable when servicing any brake system. See the below link for a handy visual explanation.
Brake squeal is most commonly caused by the vibration of the disc pad in the caliper or caliper cradle. The resonance is passed between the pad and the caliper piston, and often presents as a high pitch squeal. There are a few core causes of this such as poor disc condition, worn or missing retaining clips, lack of pad shims, etc. Many brake pad manufacturers now produce their pads with chamfered edges, a central slot down the centre of the pad and a composite steel/rubber shim to reduce the chance of squeal. Through many years of in-house testing, we have identified which compound pads are particularly suited to certain vehicles, and of course which are best avoided (prone to developing brake squeal). Give us a call and we would be happy to discuss what we recommend for your car.
Can present itself when either cold or hot, shudder is often the result of a slight glazing of the flywheel and/or pressure plate friction surface and the clutch plate. Under heavier usage can be caused by an unevenness of the flywheel and pressure plate friction surface/clutch plate after prolonged heat cycles.
Flywheels should ALWAYS be machined when performing any clutch replacement. It is for this reason we recommend a particular type of clutch to suit each individual application, rather than a one-clutch-suits-all approach. Remember, many clutch manufacturers will no longer warranty a new clutch unless the flywheel is machined at the time of install.
It is also important to note that with many high performance clutches, the significant increase in clamping force and more aggressive friction materials only magnify the problem. The trade off for the increase in performance is sacrificing a small amount of comfort and driveability. Consider this carefully when selecting your next clutch if this is a trade off you are willing to make.
Brake fluid is one of the most important yet most overlooked aspects of many braking systems. Like engine oil is vital to your engine, so is brake fluid to maximising your braking potential.
Over time your brake fluid will absorb moisture due to its hygroscopic nature. The boiling point of your fluid is significantly reduced once moisture is absorbed into the system. This is seen on the labels of all good brake fluids advertising both wet (absorbed 3.7% water by volume) and dry (new, unopened bottle) boiling point. Once boiling point is significantly lowered, it may cause a 'spongy' pedal feel, and negatively affects the braking performance of your vehicle.
The other downside of neglecting regular fluid changes is component longevity. As many hydraulic cylinders are alloy or cast iron, any moisture present over time will cause corrosion inside the bore, and can lead to complete brake failure.
As a rule of thumb, we recommend flushing and replacing your brake fluid at least every 2 years/40,000kms
Dual mass flywheels
We are constantly asked which is better: a dual mass flywheel (DMF) or solid mass flywheel (SMF). The answer is different depending on the users expectations. Many late model (particularly diesel) vehicles come from the factory fitted with a dual mass flywheel. The benefits are smooth clutch operation, and reduced idle noise. By their dampening design, they are there to absorb and minimise any vibration/noise between motor and driveline. The signs of a worn DMF can present as clutch disengagement problems, significant noise from the bellhousing or a complete lack of drive. Although expensive to replace, a DMF is the more comfortable option and will not change a cars behaviour.
SMF conversions have become particularly popular for 4WD and commercial vehicles as it eliminates the weak point of the DMF under heavy loads. Another benefit is that a heavier duty clutch can be fitted, and when clutch replacement time comes around again, the flywheel can simply be machined and reused rather than replaced. Cost in many cases is also significantly less, but it does have its drawbacks. As the dampening effect of a DMF is taken out, it can on some cases lead to an increase in driveline noise/vibration at certain RPM. As always there is a trade-off, but the design of SMF conversions has improved to the point where many can't tell the difference in driveability between the two.
In some unique makes/models, we have found through experience that SMF conversions are simply not suited. Contact our friendly staff to see if it's the right choice for you.