Rotors..turn or replace? 17-18mm left on min of 15mm

Unless they have any degree or warpage, I personally would NOT have them turned. Just burnish with 100 grit, dry sandpaper and they will work perfect.

 

I cannot see turning them removing 1mm???

That's seems like a lot unless you have a gouge from a rivet or something.

I used to turn Pontiac discs until you could see the casting vanes in the heat pattern on the front face of the disc. ..put's the caliper pistons a little far out in the bore however, and the rust can eat the seals.

 

Change the rotors.. even if you turn them with-in spec. you will probably warp them again.. I usually do not turn rotors if they are straight and have no divets and markings on them. I just scuff them..

R

 

It's possible that they're not really warped at all. A lot of that pulsating/vibrating that you feel can be the result of variations in the coefficient of friction on the rotor surface from the type of driving that you've done. This is why properly "bedding" brakes is so important. A microscopic layer of the brake pad material is deposited on the rotor surface. If it's uneven, you'll feel it.

Go ahead and turn them, you'll be fine.

If I'm doing brakes on my minivan I always use new rotors because they're only $20 each. The rotors on your 308 are many times that much. It sounds like they've got plenty of life left in them.

 

I had a Nissan 200SX years ago that used to warp the front discs every three to six months. The dealer got tired of replacing them under warranty and sent a warped set off to be machined. I was a bit sceptical and not that sure I wanted re-engineered discs on my relatively new motor but I too was getting tired of the constant trips back to dealer for replacement so I agreed.

Those machined discs never did warp again.

May or may not be relevant, just thought I'd share!

Best of luck whatever you decide to do.

 

About 5 years ago, and with about 30 track days on my F355 rotors, I had the surfaces turned/ground (don't remeber which) and did another few trck days. These rotors were about 2mm thicker than minimum spec. ON the last track day there was a new brake judder, where when the brakes were applied you could feel something, it was not a warpage, but a series of fast short sticatto vibrations. When we got back to the shop, there were nice little parabolic depressions on the rotor surface excatly coincident with the pins separating the outside rotor face from the inside rotor face.

We got the disks hot enough to slump under the pressure of pads on their surface!

The rotor thickness does two things. A) it has mass to absorb heat, B) it has thickness to resist pressure indiced yeild. The mass keps the temps down, the thickness keeps the warping/dentation down.

 

I would machine them and see what happens Steve.

I think you will still have enough 'meat' there after they turn them.

 

Ditto 2NA...I thought for sure mine were "warped" due to a shimmy during braking but it was actually the right outer steering rack bushing...very easy to check...not so easy to change...Search corbani dino saga...I actually made my own bushing which is working well 5 years later.

 

Jack it up and wiggle things. It might take a prybar and a bright light to see it.