Car quality rant

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#1175126 13-Nov-2014 12:33

joker97: umm brakes stop the tyres, the tyres stop the car?

But the OP was not stating that the tyres were locking, therefore the tyres were sufficient for the job.

The brakes, by all accounts got too hot causing the rotors to apparently warp.

This can happen on any car where the brakes are used excessively.

I am a fan of upgrading pads, fluid and rotors on my cars, usually for towing purposes as I don't have a light sports car any more.

Above should stop brake fade, in fact if you go for a pad like the Bendix Ultimates I found that they braked better with some extra heat in them... to a point, I never found that point but there will be one.

There is discussion over engine braking with an auto, I believe if this is done, I.e. using tiptronic to change down gears to slow rather than dropping down a gear to hold speed, which are 2 very different things and very different pressures on the trans.

In the end most cars have inadequate brakes for harsher driving conditions, this should be factored in how these conditions are approached. I regularly tow a horse float with horse and all my gear for weekends away, this adds up to 1200+ kg to my cars weight, this needs to be factored in when I choose my stopping, following distances and my speeds.

MikeAqua

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#1175305 13-Nov-2014 16:41

Joker - the problem you describe is poor implementation of a CVT transmission.

A CVT doesn't have fixed gear ratios. It's a variable geometry system that in theory can deliver any power ratio within limits.
In practices we don't want/need infinitely adjustable gears in a car. So for manual selection stepped ratios are offered from within the CVT's range.

In theory the ideal 'Smart' CVT system could: -
- Maintain any constant ratio within it's range.
- Automatically and continually adjust to deliver the perfect ratio for the conditions, utilising as inputs RPM, speed, cruise control, inclinometers, accelerometers and user selected modes - e.g. economy, power, slippery road, hill descent control.

It sounds like your CVT system is just smart enough to be a nuisance.

Mike

ilovemusic

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#1175310 13-Nov-2014 16:44

joker97: umm brakes stop the tyres, the tyres stop the car?

tyres are the only point of contact between car and road so have a big influence on the car's dynamics (handling, accelerating, braking).

Sidestep

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#1175376 13-Nov-2014 18:14

ilovemusic:
joker97: umm brakes stop the tyres, the tyres stop the car?

tyres are the only point of contact between car and road so have a big influence on the car's dynamics (handling, accelerating, braking).

And it's partly modern light vehicle's low profile tires,along with sensitive steering and relatively large rotors, that makes any runout (rotor wobble) so noticeable.

It's likely - as linked by Bung - that your “shudder” was partly uneven deposition of friction material on your rotors, caused by overheating and the composition of your brake pads.
Deposition tends to get worse on any high spots causing a compounding problem.

And rotors, from new, aren't perfect. Just 'within tolerance'. Same with the hubs they mount on.

When I buy rotors I mount them in my lathe, check the specs & return them for another set if they're no good.

Then I carefully cancel the hub runout against the rotor runout when I mount them to avoid an initial on car machining..

I've owned a newer vehicle that only came within measurements by shimming between the hub & rotor due to lax manufacturing standards..

Batman

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#1175378 13-Nov-2014 18:23

is that compound deposition removable?

Fred99

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#1175385 13-Nov-2014 19:08

Sidestep:
ilovemusic:
joker97: umm brakes stop the tyres, the tyres stop the car?

tyres are the only point of contact between car and road so have a big influence on the car's dynamics (handling, accelerating, braking).

And it's partly modern light vehicle's low profile tires,along with sensitive steering and relatively large rotors, that makes any runout (rotor wobble) so noticeable.

It's likely - as linked by Bung - that your “shudder” was partly uneven deposition of friction material on your rotors, caused by overheating and the composition of your brake pads.
Deposition tends to get worse on any high spots causing a compounding problem.

And rotors, from new, aren't perfect. Just 'within tolerance'. Same with the hubs they mount on.

When I buy rotors I mount them in my lathe, check the specs & return them for another set if they're no good.

Then I carefully cancel the hub runout against the rotor runout when I mount them to avoid an initial on car machining..

I've owned a newer vehicle that only came within measurements by shimming between the hub & rotor due to lax manufacturing standards..

Good Lord. This sounds like something from a F1 mechanic's guide to brake engineering - or a service manual for a $100 million aircraft.
I just buy rotors from Supercheap Auto, BNT etc, and throw them on.
If you're driving in such a manner that such "fine tuning" is required to extract the ultimate performance, I hope I don't share the road with you.

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Shop now at Mighty Ape (affiliate link).

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#1175394 13-Nov-2014 19:20

you could see it as the custom ROMs & Kernels of cars I guess ...

Aredwood

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#1175528 13-Nov-2014 23:35

I would probably do the same if I owned a lathe.

Psilan

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#1175633 14-Nov-2014 09:06

Not sure if said already;

This issue has been caused by your driving style. Hard braking. Hard braking to a stop. Sitting idle on your brakes.

If you use your brakes excessively you aren't going to warp discs. It's when you use them on a long run of hills or bends, then you pull over or wait at lights/stop signs and sit there with your foot on the brake heating one part of the disc. You are destroying your pads and damaging your rotors.

Another cause is if the pads are wearing in. If you complete a hard stop to a complete stop while breaking in, you can leave deposits on the disc or wear your pads unevenly.

+lol at race cars engine braking.

Voyager referral - https://refer.voyager.nz/68QKJ8XKK

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#1175687 14-Nov-2014 10:47

no didn't stop, at bottom of hill = 100k open road

ubergeeknz

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#1175700 14-Nov-2014 10:53

Shudder is not from just using brakes hard, brakes are designed to get hot. And I doubt the brake discs or pads on any regular vehicle coming out of a factory today are significantly different to that on a regular vehicle from the 90's.

Shudder is not from "warped discs" - it's almost impossible to warp cast iron discs. It is due to uneven buildup of pad material on the discs. This is usually because of staying on the brakes when stopped, especially while they are very hot (it is best to coast for a while without using the brakes until they cool off a bit, and then release them as soon as you stop) and/or improper bedding in. Where there is more pad material, more collects, and so the problem gets worse over time.

A skim will address this, and if it's not too bad, repeating a bedding in will help too.

Here's a guide to bedding in brakes: http://www.zeckhausen.com/bedding_in_brakes.htm