Uneven braking on Toyota Aygo (2009)

[bastones]

Hi everyone,

I have a 2009 Toyota Aygo which I've had a few years now and over the past six months I've noticed a change in the way the car slows down as I apply the brakes. It's very difficult to describe and it doesn't seem to happen all the time, but often when I'm applying the brakes to stop the car, the car slows down unevenly - in other words, the car judders forward as I'm applying the brakes instead of continuing forward slowing down smoothly. I should emphasise here that this happens with consistent pressure on the brakes, so it's not something I'm doing to cause it.

I know I'll have questions about brake fluid and whether the car wobbles from side-to-side. I've had the fluid checked by a mechanic (who also checked to make sure there isn't air in the system), the brake pads have been checked for wear and the car does not wobble from side-to-side when I apply the brakes. The only possible explanation I can think of is the brake discs could be warped, but then that wouldn't explain why it's intermittent. If this was the cause, surely it would happen every time I apply the brakes? Sometimes braking is perfectly smooth.

I honestly have run out of ideas as to what the cause could be, and several mechanics don't seem to know either which is almost baffling to me. And there doesn't seem to be a pattern I can pick up on - for example it can happen when it's sunny or raining and equally as much during the summer as with the winter with no apparent differences in frequency.

Since I've had the vehicle, there have been two repairs: last year the vehicle failed MOT as a wheel bearing needed to be replaced. Other than that, the brake pads have been replaced perhaps 12 - 18 months ago (and again these were checked recently and regreased within the last six months).

I'm stumped as to what the problem could be. Any advice would be appreciated. I would really like to get to the bottom of this.

Thanks!

[Cyker]

If it feels a bit like driving over gravel then it is probably the ABS kicking in, esp. if it only happens under firmer braking but never under gentle braking.

 

Many things can trigger it from car problems like un-even brakes or tyres losing grip, to road things like wet leaves, manhole covers, crap road surfaces etc.

I find my new Yaris is a lot more ABS-happy on freezing wet days than my old one Mk1 was! Might be because it doesn't have the diesel lump at the front giving it some weight, but also the tyres are wider.

 

 

[Planemo]

My money would be on warped discs as I have had cars that dont do it all the time. Sounds odd, but I have experienced it myself. Went away after a full disc and pad change.

Brake costs are peanuts for the Aygo.

[paulie b]

If it was warped discs then you would feel the brake pedal 'moving up and down' slightly each time you brake and you'd feel the sensation through your foot, is this what you mean by 'judders forward'? If so then, as Planemo has already said, it's an easy fix with new discs. The judder would happen each time you brake though, and would not be intermittent. I strongly suggest you have the car looked at ASAP. 

[Planemo]

With respect I would have to disagree with Paulie. I have had experience of a car that didnt judder at all under 60mph. Hit the brakes at 70 though and it felt like the car was going to rip itself apart. Likewise, I have had ones that are fine at high speeds but become noticeable at low speeds. Pedal pump does not always present itself either, depends on things like master cylinder diameters and the general design of the brake system. Worn bushes are also a consideration, and its fair to say that worn ones will compound the problem, but the initial cause will always stem from the discs (assuming that the wheel bearings are not shot and the wheel bolts are tight...).

[paulie b]

I've certainly learned something there Planemo. When the discs on my old car were warped they indeed juddered through the pedal every time I applied the brakes, lower the speed just meant a more gentle 'pump'. I certainly wouldn't argue with you as I don't claim to be an expert. I think we'd agree that the problem needs to be checked out by a mechanic at the earliest opportunity just in case there is potentially dangerous fault.

However, I can tell you (bastones) with some degree of confidence that if there is an issue with your brakes and you were involved in an accident, you are liable to prosecution. It is your responsibility  as the driver to ensure the integrity of the braking system. If any part of it is found to be defective (and it only takes one part), the least you can expect would be a heavy fine and three points on your license. For safeties sake, please have the vehicle inspected.

[paulie b]

Bastones, I've just re-read your opening post and see that you've already had the car checked by more than one person. Unless you've already been, what about a trip to your Toyota dealership to let them have a look?

I don't think it will be of much use, but I've had a look on the net and come up with this....

 http://www.toyotaofeasley.com/maintenance/common-vehicle-braking-problems-explained/ 

[bastones]

Thank you for everyone's responses. I will read through each one in more detail to decide how best I should proceed forward.

The question was raised as to whether the brake disks were warped but if that was the case I'd imagine the brake judder would occur every time (and a trusted mechanic I saw acknowledged this), however the issue does appear to be intermittent - but regular enough that it occurs most days I'm driving.

Quote

I can tell you (bastones) with some degree of confidence that if there is an issue with your brakes and you were involved in an accident, you are liable to prosecution. It is your responsibility  as the driver to ensure the integrity of the braking system

That is a very inappropriate assertion to make and I am not happy to read that.

[paulie b]

I'm not going to be drawn into an argument, but I find nothing inappropriate in reminding someone of the possibilities should they be involved in an accident and that accident proves to have arisen from system failure. I did however notice that you are posting from overseas so perhaps there was misunderstanding of the issue on both our parts?

You wrote:  'over the past six months I've noticed a change in the way the car slows down as I apply the brakes. It's very difficult to describe and it doesn't seem to happen all the time, but often when I'm applying the brakes to stop the car, the car slows down unevenly - in other words, the car judders forward as I'm applying the brakes instead of continuing forward slowing down smoothly'. 

I think you will agree that the most important component of a vehicle are the brakes, if you are having trouble with your brakes then the most likely cure for this problem is to get the vehicle to a Toyota specialist/dealer with all speed! 

[alan333]

Warped front discs can usually be felt through the steering wheel and the brake pedal.  Warped rears are usually felt through the car and the brake pedal, but not the steering wheel.  Braking hard from fast speeds usually makes the feeling more prominent, but can obviously cause you to lose control of the car - so best left to a professional to diagnose.

[bastones]

On 26/01/2018 at 10:29 AM, paulie b said:

I'm not going to be drawn into an argument, but I find nothing inappropriate in reminding someone of the possibilities should they be involved in an accident and that accident proves to have arisen from system failure.

I don't agree with you.

On 26/01/2018 at 11:54 AM, alan333 said:

Warped front discs can usually be felt through the steering wheel and the brake pedal.  Warped rears are usually felt through the car and the brake pedal, but not the steering wheel.  Braking hard from fast speeds usually makes the feeling more prominent, but can obviously cause you to lose control of the car - so best left to a professional to diagnose.

Yes I think it might be best for another mechanic to take a look. I'll ask them to take a look at the brake disks to see if that's the cause. I can understand why it sounds very likely.

Thanks for everyone's help - I'll let you know what I find out!

[bastones]

Hi everyone,

I just want to provide an update as to what the issue was with my vehicle. It turns out it was indeed the brake disks becoming warped as the disks heated up which explains why the problem didn't always manifest itself. The total cost for parts and labour came to £110 (third party mechanic - not through a Toyota authorised repair centre).

Thanks.