Brake pads can – and in fact usually must – be replaced on just one axle, as the front and rear axles wear them down at completely different rates. What you must not do is replace the pads on only one side of a given axle, as the left and right wheels on the same axle should always have pads in a similar condition. This distinction between the axle and the side is often confused, and a mistaken assumption here leads either to unnecessary expense or to a dangerous difference in braking force between the wheels.
In short
- Replacing pads on only one axle is perfectly acceptable if the other axle still has sufficient pad wear allowance.
- Replacing pads on only one side of an axle is not permitted and leads to instability during braking.
- Front brake pads usually wear out faster than the rear ones, as they bear the brunt of the braking force.
- It is advisable to select brake pads on a single axle with the same specification for both wheels.
Contents
1. How does replacing pads on one axle differ from replacing them on just one side?
2. Why do front brake pads usually wear out faster than the rear ones?
3. What happens if we replace the pads on only one side of the axle?
4. How can you tell if only one axle needs the pads replaced?
5. What should you check when replacing brake pads on just one axle?
6. Is it a problem to use different brands of brake pads on the front and rear axles?
7. When is it better to replace the brake pads on both axles at the same time?
How does replacing brake pads on one axle differ from replacing them on just one side?
Replacing brake pads on just one axle means replacing both pads – the left and right ones – on either the front or rear axle of the car, whilst leaving the other axle unchanged. This approach is entirely correct and very commonly practised, as the front and rear axles do not usually wear at the same rate. A completely different situation is replacing the brake pads on only one side of a given axle – for example, just the left-hand front wheel whilst leaving the right-hand one as it is – which is incorrect regardless of which axle is involved.
This distinction is sometimes confused, as both terms sound similar, and in everyday language the word ‘side’ is often used interchangeably with ‘axle’. In practice, however, the consequences of confusing these two situations are entirely different. Replacing one entire axle separately from the other is standard, safe practice, whilst replacing just one wheel within an axle is an error that compromises driving safety.
| Situation | Is it permitted |
|---|---|
| Replacing the brake pads on a single axle (front or rear)? | Yes, provided the other axle still has sufficient brake lining |
| Replacing brake pads on only one side of an axle | No, brake pads must be replaced in pairs on the same axle |
| Different brands of brake pads on the front and rear axles | Yes, both axles operate independently |
| Different brands of brake pads on both sides of the same axle | Not recommended; this may affect even braking |
Why do front brake pads usually wear out faster than the rear ones?
When braking, the car’s weight shifts forwards, meaning that the front axle presses down harder on the road than the rear axle at that moment and absorbs a greater proportion of the total braking force. As a result, the front brake pads are subjected to greater stress with every braking manoeuvre, even the gentlest ones, and for this reason they wear out faster than the rear ones. In many cars, the front axle also transmits drive, which places an even greater load on the front braking system compared with the rear axle.
In many cases, the front brake pads wear out after just twenty-five to forty thousand kilometres, whilst the rear ones usually last from forty to sixty thousand, although in practice much depends on the car model and driving style. This is precisely why replacing only the front brake pads, whilst the rear ones are still in good condition, is a normal occurrence rather than an exception to the rule.
What happens when we replace the pads on only one side of an axle?
Replacing the pads on only one side of a given axle means that the wheel with the new pad brakes more strongly and more quickly than the wheel with the old, partially worn pad on the opposite side of the same axle. This difference in braking force between the left and right wheels causes the car to pull to one side when braking, which is particularly dangerous during sudden emergency stops. The greater the difference in the technical condition of the two brake pads, the stronger and more noticeable this effect is.
An additional problem is that the new and old brake pads have different coefficients of friction, even if they are technically from the same manufacturer, which exacerbates the instability of the braking system. Over time, this asymmetry also accelerates the wear of the remaining, older pad, as it operates under unnatural load conditions. Therefore, the rule of replacing pads in pairs on a single axle applies regardless of whether it is the front or rear axle of the car.
How can you tell if only one axle needs replacing?
The most reliable way is to check the lining thickness on both axles directly after removing the wheels, as only such a measurement reveals the actual condition of each brake pad, rather than just an approximate appearance from behind the wheel rim. If the brake pads on one axle still have a clear margin of thickness, whilst those on the other are approaching the minimum limit, this is a sign that it is the latter, more worn axle that needs replacing. Symptoms such as squeaking or vibrations usually appear first on the side of the more worn axle, which makes it even easier to pinpoint the problem.
The car’s age or total mileage alone are not sufficient to definitively assess which axle requires replacement, as the rate of wear on the front and rear axles varies depending on the car model and driving style. Therefore, rather than guessing on the basis of general recommendations, it is worth simply checking the condition of both axles whenever you visit a garage, for example during a seasonal tyre change. Such a check allows you to replace the brake pads exactly when they are needed, without having to replace the entire set just in case.
What should you check when replacing pads on just one axle?
Before replacing the brake pads on the specified axle, we always start with a thorough diagnosis of the entire braking system using computerised technology, to ensure that the problem really is with the brake pads, and not, for example, the caliper or the disc. We also check the other, seemingly serviceable axle, because sometimes what appears to be the obvious cause on one side is actually the result of a problem that is only just beginning to manifest itself on the other side of the car. Carrying out this comprehensive check of the entire system – even when the replacement involves only one axle – helps to prevent the customer returning with the same problem a few weeks later.
After fitting brand-new, fully genuine brake pads to the specified axle, we carry out a series of tests to confirm that the brakes are working correctly on both wheels of that axle before the car leaves the workshop. We service both passenger cars and vans in this way, and the service is used by both private customers and companies with vehicle fleets, for whom replacing only the worn axle is often simply more cost-effective than replacing the entire set as a precaution.
Is using different brands of brake pads on the front and rear axles a problem?
Using different brands of brake pads on the front and rear axles is not a problem in itself, as both axles operate independently of one another and do not need to have identical friction material specifications. The situation is quite different within a single axle, where it is recommended to use pads from the same manufacturer and with the same specifications on both sides to ensure consistent and predictable braking performance. Mixing different brake pads on the same axle increases the risk of uneven braking, even if both pads are brand new.
In practice, this means that when replacing the front axle only, there is no need to match the new pads to those still fitted at the rear; it is sufficient to ensure consistency within the axle being replaced. This flexibility makes it easier to plan future replacements, as the front and rear axles can be serviced separately, each according to its own wear pattern, without the need to synchronise both replacements on the same date.
When is it better to replace the brake pads on both axles at the same time?
If both axles are approaching the minimum lining thickness at roughly the same time, replacing them together in a single visit to the garage is simply more convenient and avoids having to make two separate visits in quick succession. Similarly, it is worth considering replacing them together if you are also planning to change the brake fluid, as it is more convenient to bleed the system once, covering the entire braking system, rather than separately for each axle.
However, there is no technical reason to replace both axles at the same time simply because one of them happens to require it, if the other still has sufficient lining remaining. It is best to base the decision on the actual condition of the brake pads on each side, rather than on a desire to sort the matter out once and for all, as replacing an axle that is still in good working order prematurely is simply an unnecessary expense.
Summary
- Replacing the brake pads on just one axle – either the front or the rear – is entirely correct and very common in practice.
- It is only prohibited to replace the pads on just one side of a given axle, as this leads to instability during braking.
- The front axle usually wears out the brake pads faster than the rear, which is why both axles often require attention at different times.
- It is worth checking the condition of both axles at every visit to the garage, so that the brake pads can be replaced exactly when they are needed.