Hello all,

I recently purchased a '15 Z51 M7, and I'm planning on my second HPDE ever at the end of this month. Besides the steps in the GM track prep guide, what else would members here recommend doing beforehand?

Last DE was in my CVT WRX (yes, really) which worked fine, except for the near instant brake fade. So, I plan on getting some pads so I don't need to worry about that at least. Any recommendations? Sounds like XP12 front, XP10 rear is a popular setup.

I kind of don't want to mess with the track alignment as well, since I've had some bad experiences with shops messing that up. Am I just giving up a little grip with the lower camber and toe, or will that kill the tires on track?

 

How much life left in your current brake pads? Basically, you are still a novice and probably won't be pushing the car that hard. Change your brake fluid to something that has a high dry boiling point. Not just DOT 4 since that is no guarantee of high dry boiling point. Ford DOT3 fluid has a 500 degree dry boiling point and is a great fluid. There are others such as Wilwood 570 which is a DOT 3 570 degree fluid. Wilwood 600 EXP is a DOT 4 that will get you close to 600 degrees. Also Ferodo, Castrol SRF $$$$, etc.

You can change to race pads but I doubt you need to at this point in your driving experience.

The problem with the alignment is you really don't know for sure what you have. You don't necessarily need to go all the way to -2 deg camber but you do need at least -1.3 deg of camber. Anything less could result in tires that are pretty badly chewed up on the outside edges. The track alignment doesn't necessarily need to cause severe wear on the tires when you drive on the street. Just make sure you have a slight bit of toe in on the front wheels. Yes, the track alignment asks for a slight bit of toe out because that helps turn in but I doubt you will be needing that extra bit of turn in at this point.

Also rear caster is adjustable on all C7s and can cause issues in at the limit maneuvers. However, getting that adjusted properly can be problematic no matter what type of shop you take it to since not many shops have the proper equipment. It isn't part of the normal alignment machine measurements and isn't listed on print outs. It has to be adjusted using a special guage and and adapter fastened to the back side of the rear knuckles with the mechanic under the car making the adjustments.

Make sure you get the oil changed over to Mobil1 15W50. If you live in a climate where ambient temps don't drop into the 30s you can get by with leaving the 15W50 in the engine after the event. The thicker oil doesn't damage the engine and 15 weight oil will work fine during startup in 40 deg ambient temps.

Bill

 

I've got new-looking pads, honestly. It's a used car, maybe the dealer changed them before sale? I will probably leave them alone for now. I also have Motul RBF 600 to put in, may not be the best fluid but I do have new, sealed containers of it.

Certainly doing 15W50 - I'm in Texas, so ambient temps aren't a problem. Well, they are, but not because it's too cold.

I'll call the dealer and ask about the caster procedure and gauge - I figure if they have it and know what's going on, they should be able to align the car. I also have a local speed shop that does track alignments, though I'm not sure the have done C7s yet.

Since this is a used car, I plan to check and top-up the diff and trans as well. You never know...

Thanks for the advice!

 

This is the track alignment specs in my 2016 owner's manual. It calls for toe in on the front and rears.

Front (per corner)
. Caster: +7.0 degrees
. Camber: -2.0 degrees
. Toe: 0.05 degrees toe in
Rear (per corner)
. Caster: 0 degrees
. Camber: -2.0 degrees
. Toe: 0.05 degrees toe in
Thrust Angle: 0 degrees

I ran pretty much this alignment at COTA the other day and was pretty happy - well balanced car. I had a speed shop do my alignment - they have the tools to ensure the rear caster is set right.

I also use Motul RBF600 - no issues for me.

 

Make sure any shop you call has the tools. The adapter is critical because that is what provides the attachment point for the suspension's steering axis. The method used to measure caster on the front wheels might not be able to be used on the rears if there isn't enough room to turn the wheels. If there is room, the only way to set it on the alignment rack would be to back the car onto the machine and set rear camber, disconnect the tie rods and then turn the rear wheels 15 deg to either side of center and measure/adjust caster. Then reattach the tie rods, measure camber again and go through the process again until you get both camber and caster set correctly (camber affects caster and caster affects camber). Once that is done then reattach the tie rods and set toe in (sitting backward on the ramp the machine would be reading toe out since the rear of the tires would be toed out as far as it knows). Then turn the car around and set the front alignment and double check the thrust angle.

Back in the old days of the C2 and C3 that is basically the method GM shops used to do 4 wheel alignments because they only had two wheel alignment machines then. Back the car onto the machine, set rear, turn car around and set front.

Bill

 

Any experience with the Wilwood 570?

 

Yes, I have used it quite a bit. However, I did move to the Wilwood 600 EXP after having some issues with boiling the brake fluid on my C6Z. That was more a function of poor brake cooling and caliper design on the C6Z than the brake fluid. There wasn't a brake fluid on the planet those calipers couldn't boil.

Bill

 

Hi Bill,
Did you saw any advantage on the Wilwood 570 compared to the stock brake fluid?