A new track in DFW area, it looks a little like Cresson.

 

Hey X25,
Saw your post earlier on the fender molding mod. Here are couple photos of the same setup you did but using the APR Z06 specific canards to clear the molding. check them out, looks really clean.

 

That actually looks pretty good! Well, if only I knew what I'd exactly do when I ordered my APR kit : )

 

So how was Spring Mountain?? Baylor said you guys were practicing your wet driving skills.

 

It is an impressive facility, and was pretty good experience! Unfortunately, I was a bit sick the first day, which progressed to headache and a little fever next day, and I had to bail out very early on second day : (

I also finally got to meet Baylor and also Tim from Boardwalk Chevy; nice to meet you guys!

In other news, I drove to Idaho the very next day once I got back from Ron Fellows to pick up my new truck. I was hoping to get a bit of snow on my way back to play with my new truck's 4x4. I got my wish, and then some! After 5 hours of driving through snow, I was finally back home at 2 AM :P

 

Nice truck! Duramax?

 

Yep, the new Duramax rated at 445HP / 910 ft.lb. I think RAM still does a better interior, but this truck is hard to beat in terms of functionality. The only real issue is the turning radius with the long bed, which is amplified by the unusually restrictive max tire turn angle, but I think I'll be OK : )

 

Update
Just received and installed extensions for the coilovers!!



The extensions gave me 0.5" up front, and about 1" at the rear.



Decided to put a clear coat on the springs, since I scratched them quite a bit during my fiddling prior.



The front bolts were a little bit too short. I sourced grade 8 5/16"x24 bolts at 3" long, along with washers and a lock washer. It fit perfectly.



Front coilovers installed with the extension.



As you can see, there's a bit of a change in the geometry of the coilovers, since the pivot point of the front mount is now elevated 0.5" higher than the original mount location for fronts. No such change for the rears, since the the distance of pivot point from the rear mount location is same. I am not sure what the impact of this change would be.


Numbers:
My ideal numbers that I initially setup were 685mm front, 720mm rear. This preserves the 35mm original rake of the stock suspension (past the wheel/tire change)


LF, RF, LR, RR

• Initial, extension installed. 3, 3, 3, 3 (mm preload all around); 205 lbs ballast, 100% fuel.
  • 675, 683, 726, 735.
• Final, with 10, 3, 3, 0 (total pre-load in mm).
  • 684, 685, 729, 730 (height in mm from ground to center fender line).

Remarks:

• The front height extension was just right, the rear extension increased rear minimum height more than needed by 10mm. This means, now I have 10mm extra rake. I am not sure if this is important or not, since such changes often happen even when you put different diameter tires.
• The pivot point of the front suspension is now elevated from the lower control arm surface by 0.5". Again, I am not sure if this is important. The rears are fine, since the pivot location is still the same.
• I finally got rid of most of the preload!

It's still snowing around here, but I will try to test it out as soon as the season opens up!

 

strait rate springs can not be preloaded. You need to corner weight the car to set the spring purches.

 

I'm not sure if I understand what you mean; why would they not be pre-loaded? Actually, changing the preload is the only way to set the driving height of these coilovers, and I got the extensions to get rid of most of the preload I had to do to achieve the ride height I was looking for.

 

I guess it's the word "preload" that I have a problem with. I have had a number of drivers try to tell me that preload increases spring rate. It does not, a strait rate spring is that rate though all of its travel.
If you are really interested in getting everything out of your coilovers , you need to get some scales, and get your corner weights. Then add turns or reduce turns to even out the corner weights. I have seen drives with some real reductions in lap times with a good corner weight session .

 

OK so you were trying to say that the effective spring rate would stay constant since it's not a variable rate spring. For the record, I never said preload increases spring rate. Corner weighing is always a consideration, but so far I avoided buying the scales to do it.

 

More pictures of your wheels and the car?

Did you paint the chrome lip yourself?

-Josh

 

Regarding getting good height measurements
Ever since I removed and inspected my coilovers, and realizing it was not springs' culprit, I was trying to make sense of why it settled so much after initial install. I have been testing various ideas, and I think I finally have a much better idea.

Here are a few tips/remarks I came up with (some I knew, some I realized recently):

• Drive a bit, only then fine-tune: Once you do the initial setup, you should drive a bit, try to load the suspension a bit, and get back to the garage to re-measure. This made measurable difference. Perhaps it gets rid of any binding control arms get into during the install?
• Roll back and forth: I just realized about this. Do you remember alignment shops moving the tires back and forth? That actually makes a difference, especially if you're on a platform (like the wheel cribs I used). On my wheel cribs it helped the tires center themselves better. Since the wheel cribs' available tire patch space is very limited, I needed to put them dead-center, especially at the rear with the 325 tires.
• No hand brake or gear: It goes without saying, that you should not have the hand brakes or leave it on a gear. It also means it has to be as flat as possible, but I'm hoping you've ensured that already.
• What you do effects the cross-weight: This must be obvious when you think about it, or if you ever corner-weight-balanced a car. For instance, if you increase the height of LF, most of the weight transfer will move to the RR. This will also mean that you will need to check back and forth on cross corners when you're making major adjustments.
• If using platform/cribs, make sure to verify the measurements on the ground: Especially if you're using very large tires, the cribs/platforms might alter the numbers.

My ready-for-track height numbers

• If you recall, I was trying to get to 685F 720R (which is about 15mm drop from stock height); look how close I got!
• The biggest changes were caused by driving a bit, and increasing the height of LF, which in turn lowered RR (which was alread at 0 preload), which in turn allowed me to remove the 3mm preload at LR as well, bringing down the rear height nicely.
• Overall, I am pretty happy with the much lower preload values, of course assuming 17mm (~0.7") height drop is enough to begin with.

 

I am changing over from z51 calipers to z06 calipers and am having a hard time removing the front brake line from the fixed brake connection. Any tips or ideas on how to get to the connection to remove it?

 

Those lines are a softer kind of metal, and they don't like abuse. Do you have flare nut wrenches? Those wrenches increase the surface, making it less likely to snap. You can also try vice grip if surface is already damaged.

Good luck!

 

I took the bolt out of the brake line bracket and removed the suspension sensor. That allowed me access to the line and I was able to remove it. Installed S.S. lines with my new z06 brakes thanks to your posts. Thanks!!!

 

I am sure everyone has a procedure that they like to do or that works for them. That being said when you do car setup treat each one like a science experiment in that you try to make everything as repeatable as possible and try and control as many variables as you can so that when you do make a change you can more tightly control what is going on. That being said this was a typical way we did the ALMS GT2 car.


Pad and testing conditions: Since you have to move the scales to different locations and race tracks you do need to make sure when you setup your scales they are done as flat and level as possible to the world. If you have to shim or adjust anything make sure that the lifting blocks or pads are not sitting on anything that compresses (grass, dirt, carpet, wood....) That way you know the pad isn't going to change your results. Make sure to control wind blowing over the car too...even cars without aero are going to change the weights so if you are outside and it is windy, try to get a tent around it and don't have a fan in front of the car blowing across it.

Car: Try to make the car the same each time. So if you weigh the car with 40lbs of fuel...try and make sure that is what is in it. Of course street cars are a lot harder to pump out and put fuel back in...with the race cars we would pump them dry, weigh the fuel going in and make sure it was the same weight of fuel each time (typically 1/2 a fuel load). Also need to control rolling stock, again for the ALMS car we had one set of wheels and tires that were confirmed not to be bent, tires round, and were never driven on. They were put on only to go on and off the scale pads and that was it. No flat spots or bent wheels and were kept at the same tire pressures for ever scale setup. Next time you are on the pad, take 2psi out of one tire and see how it changes your numbers. Ballast was the same too, we tried to use the driver, but if not would find someone close to the average weight and that person was used each time, and they can't be working on the car, need to be in driving position. Lastly make sure everything else is in race config. If you have a drink bottle, fill it. If you have a cool suit fill it.

Now you will typically have to take the car on and off the pads to make changes. Never jack the car up on the pads. When the car rolls on or rolls off it is rolled by the wheels only. Do not push on the frame or body work to twist the car. Also make sure one front and one rear end link is un-hooked....don't want the bars coming into the equation either.

If you have to jack the car up and set it back down, find a "happy" and consistent way to bounce it once it hits the ground and do this the same each time. Typically we would have one guy at the front and one guy at the back that would bounce the car at the same time for the same number of times. Roll the car back on the scales by the tires only past the scales and then back onto them forward. If you had to make a toe change make sure the car was rolled enough to straighten the rubber out on the tire so it isn't being pushed one way or the other.

When the car goes on the pad, make sure the tires are as centered on the pads as possible as being shifted fore or aft will change it too.

If you have shocks that have a gas pressure adjustment or fill port....which the G2's do. Keep track of shock pressures over the year as they shouldn't vary much but we would check them at the start of every weekend. Keep in mind also when you check them you will loose approx 10% pressure due to the loss in volume when you do it, so you have to make sure to keep nitrogen on them when you do it or you will just keep bleeding the shocks down.

Now the above is at the pro level and I'm sure I am forgetting a few things but you get the idea. Not everything listed above would be needed for the weekend racer but you get an idea when you do something at home and roll it on and off the numbers change and you wonder why...probably to do with some of the above...and we even saw changes of 2-3 lbs just going on and off the pads.

 

Great read, thanks for sharing Anthony!

I suppose the main take here for everyone is that 'measuring accurately with the measuring tape' does not mean much unless you keep your environment in tight control. I've learned a lot on this matter in the last few months, but it appears there's still much more that can be done if you will race the car. We cannot do everything right, but we can at least do the same wrongs, so at least the measurements would be as repeatable as possible.

My biggest revelation was measuring over the wheel cribs vs. the ground. The rear tires are too big, and don't fit the wheel cribs perfectly, causing discrepancy at measurements. This had a lot to do with my high initial 'settlement' numbers, since I measured the second set of numbers on the ground - lesson learned!

Anthony, thanks for your advice and being patient with me; your advice is always much appreciated.
- Do you think 0.67" height drop is a good compromise?
- I could actually get a nitrogen tube and check the pressures once every few months; do you think that would make sense? I am thinking if it indeed doesn't need frequent rebuilds like some other brands do, perhaps at least checking the pressures once a year would make sense.

With every new car, I am amazed that I still learn just as much new stuff on cars.

 

A lot of that, in the science experiment keeping everything replicable, requires a consistent driver

My laps still vary too much for me to know what I like I wish I ran laps within .5 seconds every time

edit: running race stuff (tires, pads, etc) that won't fade through the session definitely helps a lot with that. Tuning with street tires is damn near impossible IMO. They change too much from lap to lap. They go from too cold to just right to overheated in 3 laps. Heck, I've had them go from good to greasy through one lap. Turn 2 was great. Turn 9 was sketchy