Ultimate track alignment for Z/28 suspension?

[X25]

Originally Posted by White_SS/RS

Wider tires like the 305 are going to be more particular about camber adjustments. The tire pictured above, most likely ran on the OEM alignment of -1 to -1.2 shows the desperate need for camber. The problem though is the OEM suspension design just doesn't allow for what it really needs. Camber plates will have to be an essential part in obtaining something optimum. My guess, since it’s really going to depend on the track and driving style that -2.5 would be a minimum starting point. My thoughts on running more caster… It can be an advantageous way to maintain camber throughout the turning arc, possibly gain some camber but mostly it’s going to help the car return to center and track better, but it’s not going to make up for a lack of camber. I’ve found that you may as well run an optimum track setup if you track more than a few times a year because you’re going to wear out your tires on track before they become a problem on the street anyway.

Makes sense. I honestly don't care about a bit more wear at the street, and in my experience, excessive toe is a much bigger problem than excessive camber at the street anyway. I think I will stick to my plan of -3 / -2 camber with zero toe, will shoot for 7 degrees caster, with camber prioritized if I have to compromise.

If the car feels too lazy during turn ins, I can then add a bit of negative toe up front. The recommendations mentioned above have too much toe for my taste. Once a car starts dancing in brake zones due to too much toe, I start braking early, negating all the gains that toe would allow in turn in. For someone who only does autocross, though, more toe would make sense.

There is also different alignment targets for rain/wet, but let's keep that out of scope

[White_SS/RS]

X25, I think your on the right track. Toe is definitely a tire killer and with the added caster I'm sure it will have good on center feel. I have a very slight amount of negative toe -0.10 a side which hasn't been too bad since it basically puts the tire at the same angle as the OEM just on the negative side of the scale, but like you I'm not too inclined to go much more extreme than that since I do see more street miles

[Mgizzle]

I would think that -3 camber is overkill but X keep in mind we dont have z/28 bearings on our 1LEs, the Zs are stiffer and a different PN. That could add to your issue vs guys who own z/28s. To me camber adjustments been very simple by using a tire temp gauge like the longacre one. Check outboard, middle and inboard of tire on all 4 and write it down. This gives you the answer of how much camber you need and also if your pressures are too high or too low. I go for slightly hitter inside and then even drop to outboard. This tells you your tire is flat in corners and in straight line the inboard is hotter. If your midd of tire is hotest your pressures are way too high.

I always ran 0 toe too but always see guys run positive camber on all 4 as GM recommends and the cars drive nice. It helps with turn in and gives you better toe when suspension is compressed in corners I believe.

As far as pressure, if you are close to 40 psi you are not using the tire in my opinion, you are past the best grip. On the 1LE once I am past 36psi car is all over the place.

[Nor Cal ZL1]

Originally Posted by Mgizzle

I would think that -3 camber is overkill but X keep in mind we dont have z/28 bearings on our 1LEs, the Zs are stiffer and a different PN. That could add to your issue vs guys who own z/28s. To me camber adjustments been very simple by using a tire temp gauge like the longacre one. Check outboard, middle and inboard of tire on all 4 and write it down. This gives you the answer of how much camber you need and also if your pressures are too high or too low. I go for slightly hitter inside and then even drop to outboard. This tells you your tire is flat in corners and in straight line the inboard is hotter. If your midd of tire is hotest your pressures are way too high.

I always ran 0 toe too but always see guys run positive camber on all 4 as GM recommends and the cars drive nice. It helps with turn in and gives you better toe when suspension is compressed in corners I believe.

As far as pressure, if you are close to 40 psi you are not using the tire in my opinion, you are past the best grip. On the 1LE once I am past 36psi car is all over the place.

This, start gathering tire temp data and you will be well on the road to your perfect set up.

[AG1LE]

Originally Posted by Mgizzle

I would think that -3 camber is overkill but X keep in mind we dont have z/28 bearings on our 1LEs, the Zs are stiffer and a different PN. That could add to your issue vs guys who own z/28s. To me camber adjustments been very simple by using a tire temp gauge like the longacre one. Check outboard, middle and inboard of tire on all 4 and write it down. This gives you the answer of how much camber you need and also if your pressures are too high or too low. I go for slightly hitter inside and then even drop to outboard. This tells you your tire is flat in corners and in straight line the inboard is hotter. If your midd of tire is hotest your pressures are way too high.

I always ran 0 toe too but always see guys run positive camber on all 4 as GM recommends and the cars drive nice. It helps with turn in and gives you better toe when suspension is compressed in corners I believe.

As far as pressure, if you are close to 40 psi you are not using the tire in my opinion, you are past the best grip. On the 1LE once I am past 36psi car is all over the place.

[X25]

Originally Posted by Nor Cal ZL1

This, start gathering tire temp data and you will be well on the road to your perfect set up.

Yep, I'm trying to find out the best starting point, which will also increase my chances of hitting the sweet spot. Afterall, alignment is harder to change than tire pressures. I'll probably get measurements with a pyrometer once I hit Oregon Raceway Park. Since we do open track days as a member of the ORP club, I can easily pull over to the hot pit, check it out, and go back out without having to deal with 20 min sessions I have to go by in other tracks.

Mgizzle, by bearing, do you mean the hubs? Hubs are a wear item, and if they are different part #, I can just replace them with Z/28 hubs when they start giving up Considering the weight of these cars, though, I can't imagine having too much of a difference (deflection) between hubs.

My '13 Z06 came with ZR1-spec (SKF) hubs from factory, and even though they were much more stout, I did not feel any difference between those hubs and what came with my '06 Z06 and '12 Grand Sport. Well, I'm not good at feeling subtle differences, though, so it might just be my numbness, too : )

[Nor Cal ZL1]

I would start with Justice Petes specs then. I know he checks tire temperatures, so.I would trust his info as your start point.

Off to google Oregon Raceway Park. Might have to check it out.

[Mgizzle]

Originally Posted by X25

Yep, I'm trying to find out the best starting point, which will also increase my chances of hitting the sweet spot. Afterall, alignment is harder to change than tire pressures. I'll probably get measurements with a pyrometer once I hit Oregon Raceway Park. Since we do open track days as a member of the ORP club, I can easily pull over to the hot pit, check it out, and go back out without having to deal with 20 min sessions I have to go by in other tracks.

Mgizzle, by bearing, do you mean the hubs? Hubs are a wear item, and if they are different part #, I can just replace them with Z/28 hubs when they start giving up Considering the weight of these cars, though, I can't imagine having too much of a difference (deflection) between hubs.

My '13 Z06 came with ZR1-spec (SKF) hubs from factory, and even though they were much more stout, I did not feel any difference between those hubs and what came with my '06 Z06 and '12 Grand Sport. Well, I'm not good at feeling subtle differences, though, so it might just be my numbness, too : )

The zl1 and z/28 use SKF hubs too, 1LE doesnt. While the 1LE does have better bearings than a stock SS there is a reason the other two higher peformance variants use SKF. Easy swap and I notice the difference since I run CTS V rotors (co cast). I have a lot of pad pry back/knock backafter curners, have to prime brake pedal with left foot into some turns to remove travel. Like you I plan to swap them after I destroy these rotors.

Fyi, I also saw a few very good infra red sensors that easily mount to our plastic wheel liners if you want to monitor tire temps during actual driving. I saw them for 150 bucks and it read one tire. Again, if somebody really wants to go serious.

[X25]

Originally Posted by Nor Cal ZL1

I would start with Justice Petes specs then. I know he checks tire temperatures, so.I would trust his info as your start point.

Off to google Oregon Raceway Park. Might have to check it out.

I don't think those specs would work out for me, since I don't like high toe setups. It might be a good starting point for someone else, though, or perhaps more so for autocross.

Originally Posted by Mgizzle

The zl1 and z/28 use SKF hubs too, 1LE doesnt. While the 1LE does have better bearings than a stock SS there is a reason the other two higher peformance variants use SKF. Easy swap and I notice the difference since I run CTS V rotors (co cast). I have a lot of pad pry back/knock backafter curners, have to prime brake pedal with left foot into some turns to remove travel. Like you I plan to swap them after I destroy these rotors.

Fyi, I also saw a few very good infra red sensors that easily mount to our plastic wheel liners if you want to monitor tire temps during actual driving. I saw them for 150 bucks and it read one tire. Again, if somebody really wants to go serious.

I'm using StopTech BBK; perhaps it's a bit less noticeable with those BBKs. CTS-V/ZL1 calipers come up with huge pads, which perhaps make it more vulnerable to such knock-back? The OEM calipers might flex more, too. The StopTech pads are substantially smaller; perhaps half their size. Yes, we should switch to SKF (OEM Z28) next time; sounds like a plan!

Himm, such a sensor array would be amazing to play with! I could slowly go around all tires during the day if they're easy to switch to the next tire. Yet another toy to play with..

[Nor Cal ZL1]

I would at least try jp's set up. Looks less expensive than your destroyed tires to adjust the tow to -.25 and back if it you don't like it. Personally I think his specs look like a great starting point for track use. If nothing else you need at least -.5 more negative camber minimum to start baselining the tire temps.

[White_SS/RS]

I'm pretty sure the 1LE, ZL1 and Z28 all use the same hubs. There was much discussion and literature about it, specifically regarding the 1LE using the ZL1 bearings. It should be noted that the more stout variant is only about load capacity and longevity not tolerance accuracy. Anyone seeing more than a few thousands in deflection should replace them regardless of type.

[White_SS/RS]

Here is a list of parts and numbers to bring your car to The ultimate track car spec for the various C5 models

[X25]

This is a great list; thanks for sharing!

[cdb95z28]

Originally Posted by White_SS/RS

I'm pretty sure the 1LE, ZL1 and Z28 all use the same hubs. There was much discussion and literature about it, specifically regarding the 1LE using the ZL1 bearings. It should be noted that the more stout variant is only about load capacity and longevity not tolerance accuracy. Anyone seeing more than a few thousands in deflection should replace them regardless of type.

I thought the same until Mgizzle stated otherwise. He would know I looked up what wheel bearing part #s apply to the 1LE, ZL1 and Z/28 and SS, they are not all the same

Z/28 and ZL1, same bearing front and rear, # 25954415, $250 each

1LE front, #23103115, $135 each
1LE rear, #23103121, $188 each

SS front, #13580685, $174 each
SS rear, # 13589510, $174 each