warped rotors

I would just get centric premium rotors from rockauto.

I have run multiple variations of premium rotors on all my cars. The e-coat makes them pretty for years, and I just get the non-slotted, non-cross drilled for no added stress and wear.

Huh? You had them turned, then your mechanic told you (after turning) the discs are warped? Might be time to seek a different mechanic.

Truth is that its nearly impossible to warp an iron disc, at least on a street car. They'll crack and break, but "warping" is very uncommon. Vibration, 99% of the time, comes from uneven pad deposits on the disc face and is mostly evident under light-medium brake pressures. If the discs were turned properly, they should be flat and without any pad material, so the mechanic's diagnosis is wrong. If you had them turned and didn't bed in the pads again you likely caused the same issue after turning. Bedding pads (especially performance/racing) is a vital step in maximizing your brake system.

There could be something else going on as well. Applying brakes increases the forces on the front suspension so its pretty common for suspension/steering issues to be worse under braking. Bent wheel? bad tire? ball joint? wheel bearing?

As for your disc question, I've been using Centric's discs for several years on both my street cars and the chump car. Never had a disc issue and (on the race car) they've taken 10-20hrs of abuse at a time.

I hope you have swapped tires around/ had them balanced to verify balance, an tire/wheel trueness.

Worn and loose tension rods will cause the same "vibration" under braking symptom. I have personally seen this and fixed this issue on many other Nissans that use a similar tension rod style such as the Z32 and Q45.

While it is true that it is a rare thing to have a warped rotor on the Z31, it certainly isn't impossible. These rotors could have been cut once (or even twice) before thinning the material to the point of warping. And even so, do you know what happens to a warped rotor after it is turned true again? It warps very soon thereafter. Be sure to check your caliper pins for excesssive lateral play, an often overlooked cause of pedal pulsation. Also a +1 on a suspension component and wheel bearing check as well…

On a Z31 it is rare due to the bolt-on design of the rotors and their thickness, it is usually caused by pad deposits after sitting (as Bremsen stated above). However, I will have to politely disagree with his statement on the near impossibility of warping a typical rotor and that they will crack and break first. I have done literally thousands of brake jobs and never seen a cracked or broken rotor on a street driven car… ever. I see warped rotors almost daily in nearly every foreign and domestic car produced in the last 20 years. More frequently than the pad material running out is that the rotors become so warped that it is unpleasant to drive. This seems most prevalent in small to midsize Japanese cars and most minivans. Aftermarket parts exacerbate this situation but even many cars suffer from this with oem equipment. Rotors are now considered disposable and very seldom are cut, only exception being large trucks.

Deposits are caused by overheating the pad compound and it transferring material in spots or smears onto the disc face. Once it starts, the material continues to build in those areas which leads to vibration and the run out you likely see when measuring. The reason you see it so often on small cars and minivans is that the systems are small and have poor (or no) ventilation. Compound that by marginal OE pad compounds (and even worse aftermarket crap) and most peoples inability to properly use their brakes, I'm not surprised you see a lot of it. It probably doesn't take more than a 200* to overheat a duralast pad. This is why its so important to bed in performance and race pads. Having that layer does a ton for preventing uneven transfer and it maximizes the friction between the disc and pad.

As for warping a disc, on the Z31 or otherwise, think about how much heat would be needed to deform/warp a cast iron disc. Certainly more than one would see during any normal road usage and nothing that a standard OE road pad with street tires could produce. How hot does your turbo manifold get? Does it warp? On top of that, cast iron is pretty hard and brittle, so its not like force is going to taco one like a wheel rim. If it gets smacked, it breaks into pieces.

And I've done my fair share of brake jobs as well....lol. Except most of what I do is a little more heavy duty than what you find on a Caravan or Camry. Well maybe on a Camry.

The warpage is mostly from braking hard and then holding the calipers shut while stopped, for example at a stoplight…

It's not only the total temperature, but the uneven heating/cooling under pressure, while pad material welds itself to the rotor, often made worse by the fact that half the rotor is exposed to fresh air, while the other side is typically almost covered with a dust shield

All it takes is a handful of these events overlapped to create a serious imbalance, and apparent "warping"

As an addendum: many aftermarket rotors are HT250ish iron, which is quite soft, barely harder than 7075 aluminum, good quality rotors are made between HT300-HT350, and racing rotors are sometimes made of ductile iron, which loosely is categorized as HT450-HT500

http://www.stoptech.com/technical-su…nd-other-myths

Thank You everyone for your contributions. To clarify, I originally took the rotors off and had them turned at Car Quest. When that didn't clear up the problem I took it to one of

two mechanics which I trust locally. I do occasionally have days of spirited driving down the mountain (Paris) and have had at least one other rotor issue after a particularly intense run.

Problem solved. It was just the rotors. The guy I buy my tires from locally offers lifetime wheel/ tire balance for free.

WOW! What a difference in how nicely the front end handles compared to before. Thank You all for your input.