I've heard many people referring to the "rake" that C5s are supposed to have - 1/2" lower in the front than the rear, right?
Well, I was wondering where this rake should be measured from... the reason I ask is, I lowered my car on the stock bolts on the weekend; 2 turns was all I could get on the left rear bolt, so I just went with 2 turns all around as to not mess with the corner weighting.
When I was done I measured from the frame to the ground at the four jack "puck" locations and the measurements were almost the same front and rear. Where are the measurements for the 1/2" rake supposed to be taken from?
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'02 EB/MR Z
Halltech Stngr, LGM Pro LTs, Stock Tune, 4 18" R2's on OEM Rears
11.86 @ 118, 1.82 60' (F1's), best 60' 1.80 (R2's)
80% Track, 20% Driver, 100% Z
Whenever you lower the car, you need a new alignment. If you want to set the car up right, you need to corner weight the car. This is done after the initial alignment by placing a scales under each wheel. The object is to get the opposite corners to have a 50/50 weight distribution. This is measured from left front to right rear and right front to left rear. The distribution is accomplished by the raising or lowering the car. This is how T1 cars are set up.
If you don't set the car up properly and you don't spend anytime on road courses, then whatever rake you have right now does not make a difference. In any event, a 1/2 inch isn't enough. That's still 4 x 4 territory.
Angel,
Do not corner weigh the car unless you are racing.
Even DE cars do not need to be corner weighted.
I suggest you pick up 2 longer bolts for the rear. Many hardware stores and supply places have them for around $7.
Measure the current ride heights at all 4 corners.
Install the new bolts.
Get ride heights even again.
Then continue lowering equal amounts side to side and front to rear to keep the rake.
Good luck with it.
Dave
Sabot: This is exactly the info I was looking for. The shipping holes... are those the same as the "jacking" holes? They are the "slots" in the frame located roughly at the front and rear edges of the doors, correct?
Dave: I'm not sure why you wouldn't want to corner weight the car? Without corner weighting it is possible that the front right and rear left tires could be supporting the majority of the cars weight, causing ridiculous understeer turning left and similar oversteer turning right (or vice-versa)... not my idea of a well set up car, regardless of what it's being used for. Tuning the suspension for improvements on the track will also pay off on the street, no?
Bobby: I always wondered why my lawn wasn't as green as it could be!
Gary: I think the rake in the car's factory setup (front being 1/2" lower than rear) is there for aerodynamic reasons - it probably has no effect on handling, except maybe at high speeds. You're right - slamming it and setting it up right is where I want to be. Right now it IS a 4x4 - I think the previous owner may have even had the front end LIFTED because, even with two full turns taken out of the bolts my front end is still higher than another guys Z that I work with!
Angel,
What I said was you don't need to corner weigh the car unless you race it. No doubt corner weighing would be the ideal thing to do even for a street car but few people do it.
The cars come from the factory with ride heights and rake within an acceptable range set by GM. If you lower the car similar amounts side to side and front to rear then you should still be within those ranges.
I used to spend 5 hours corner weighing my race car. It is time consuming. I would not want to pay current shop labor for that job.
The weights change when the gas tank is full or empty and when you have a passenger, etc.
Pure race cars are more sensitive to changes in weighting than street cars.
I have been doing DE events for 20 years with corvettes and have never had one corner weighed. Other than the T1 guys I have never heard of anyone at the track corner weighing theirs.
I am not saying you shouldn't. You are right, corner weighing is the best way to go if you want to spend the time and money.
Dave
I guess the biggest reason for wanting to corner weight the car is I think the stock setup has already been messed with and I have no idea where it is right now... had I owned the car from brand new I'd be less worried, but I actually get the feeling that the front of the car was RAISED from stock, and the rear left bolt had HALF as many threads showing as the right one did. This doesn't seem right to me; the car is clean underneath with no signs of accident damage or anything like that, so I doubt the frame is twisted. I just want to be sure that I'm getting the most from the car, that's all.
Angel,
Now I see your concern.
GM has recommended trim heights. If you can get the car back to those heights you should be fine. The trim heights are measured from 4 spots on the frame.
Again, corner weighing would be the best way to go.
BTW: it is not uncommon for there to be different amounts of threads showing on the bolts from side to side. I have seen them differ as many as 4 threads from the factory. That is why just turning the rear bolts up until 2 threads are showing is not correct.
If you get a price for corner weighing the car I would like to know. Please post if you do. Thanks.
Dave
Maybe I can find a shop that'll just let me drive up on thier scales and see where the car's at, take it home to make an adjustment, and go back again the next day...
Yeah right... it'll likely cost an arm and a leg! At least I'll sleep well knowing the car is set up right!
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