Steering vibration=hwy. speed braking:2nd guess mechanic?

[Guest jjohart]

Hi. I put on new Metalmasters brake pads and cross drilled (Nimso?) rotors, b/c the used 280ZXT I bought in September had 10% pad left in rear, and FWIW I decided to change the rotors as well, front and rear b/c I noticed a moderate steering wheel pulsation (shaking) when brakiing.

I've driven the car for about 3 weeks since that work was done, and while actually on the way to the same mechanic for clutch/flywheel replacement, the steering wheel started vibrating on moderate slow braking from 55-65mph. I had the mechanic do a hwy. run with me, and he noticed it (1), but said it could be warped brake hubs, and kinda passed the buck with me by saying to take it to a brake shop with an on-wheel brake lathe.

I kinda threw that idea back at him by telling him I'll leave the car with him (in southern NH-I'm near Boston) for a few days (there's other work to do on the car anyway, but I hate to leave it), so he can farm it over to such a shop. I am wondering what else it could be, since the car wasn't vibrating at all for about 3 weeks. He seemed a bit reluctant about the farming off to another shop, being that he's also hinted that I may need to send the engine head out for gasket work (more on that in misc. tech!!). I figure, with the car being over 20 years old, it's best to keep the same cook on the soup as much as possible, mechanically speaking, even if I have to do without the car for a week or two!

I do need steering column parts replaced, specifically the upper rod and lower joint, if not the steering box, for a slight rubbing and groan felt/heard when doing a hard left (like a turn onto a side road). The mechanic initially jumped on this as source possibility (again, to be tended by someone else at my cost!), but I don't think it's that problem, b/c as I keep repeating, this problem is not static (happening all the time), but it seems to be worse the more times that I press the brake pedal (e.g.,on rte. 3 I went about 10 miles heating up the brakes, and the more I did it, the worse the vibration was, not to mention the smell!).

So, the short question is, what else could it be, other than brake hubs and steering componentry, being that the problem is variant, but becomes more obvious the more one brakes? I keep thinking something might be wrong with the way he mounted the rotors or pads, but he didn't take off the wheels...I felt uncomfortable questioning his work already done (and it has new tires and the wheels have been straightened), and he seemed a little to quick to send me off to another brake shop or something! I'm sure he made an educated guess, but I don't want to take it elsewhere if I can somehow pinpoint what HE needs to do as most likely culprit/solution!!

John-83 280ZXT, 2 + 2

[JMortensen]

Find a different mechanic, first of all. When I worked as a mechanic if I did a job and something went wrong, I would tell the customer rather than trying to pass the buck. If anything else goes wrong when this guy works on the car you're likely not to have it tended to by him, at least not without a lot of resistance.

 

You got cross drilled rotors from Nissan Comp? I don't even remember them carrying cross drilled rotors. Anyway, sounds like they are warped from your description. The problem is that when you lathe cross drilled rotors, you have to chamfer each hole so that there is not a sharp edge, otherwise the pads can get chewed up like a cheese grater.

 

You can check on pricing, but it may be cheaper and easier to get new rotors. I got the PowerStop crossdrilled rotors, which are Brembos, and I've thoroughly abused them and they have yet to warp. I think I've boiled the brake fluid at least 5 times and they're still straight.

 

Also IME Metal Masters will eat the wrong compound rotor in an amazingly short amount of time. I haven't been happy with them on the street, and they are HORRIBLE at the track, so I would suggest that you try a different pad as well. Maybe a stock nissan pad, or a Porterfield R4S pad if you're feeling racy.

 

Jon

[EvilRufusKay]

You definatley want to look for a new mechanic. Anyone that recomends a on the car lathe has probably never used one they S^CK!!! Secondly...what is a brake hub? and why would it need to be turned? As jon said your rotors are warped. IMO never bother to turn rotors. If they are warped toss them and get new ones. If you turn them the metal will be thinner and therfore warp again...SOONER!! It may be that your rears are not adjusted right so the fronts are doing all the work... this would cause higher than normal temps and pehaps warp your rotors. Also as Jon said you may want to try different pads. I don't have much expierience with metal pads but if not matched to the rotor might cause excessive heat.

Try a post calling for people who live in your area to recomend a honest / expirienced mechanic.

 

Rufus

[Guest ZmeFly]

turning rotors only leaves you with less then what your started with. So understand that if in 3 weeks they warped with the NEW amount of metal on them what do you think will happen when they shave off another .030.

 

I also totally agree on the pads, Metal Masters suck arse, get as mentioned Porterfeild pads or Hawk Pro pads. Both are great

[Guest freakypainter]

if used properly an oncar-lathe is the best way to go. When turning the rotors off the car they are often mounted to the lathe differently than they are mounted to the car and a different clamping force can change the runout of the surface. Also, alot of rotor manufactures have different specs on tolerable runout, take that into consideration with shelf life, how much stuff was thrown ontop of them in shipping, on and on, I know alot of people who wont put on a new set of rotors without turning them first. Taking .002 or .004 off a rotor will not hurt anything. Most rotors have a minimum thickness and as long as you are thicker than that spec they are fine.

[EvilRufusKay]

On car lathes are only better in theory. Yes it would be optimal to cut a rotor on the hub which it is mounted however, these units are difficult to set-up correctly. The are light and as such move around a lot. Automakers push these units on dealers because they feel that with less dissassembly time a tech should be able to do a warrenty brake job in half the time. I have used three different types of these lathes and have yet to find one that worked well. As for turning rotors, once again yes this is correct in theory. If you had your own lathe and could set the depth of the cut yourself then yes turning a rotor a small amount would be fine. However, in the real world of mechanics someone is going to remove more than needed. This happens for several reasons, mostly because of time. Get em in and get em out. Rather than take several small slow cuts it is more likely a tech will take one deep quick cut and MAYBE clean it up with a slow shallow cut. Obviously not all techs are the same but....working with many I have seen few that care about how soon you will be back with another warped rotor.

 

I guess I agree with FP but unfortunatly have no faith in someone eles working on my car. Get new and replace.