22 replies to this topic

[Kyle Burkhardt]

We did an alingment and balance last week. First one on this car (and miata for that matter). Followed JD's script.

Total wt was dead on NASA rules with me in the seat (213), shirt in the pass side (22), and the 4L fire bottle is mounted in the trunk in front of the spare well in the middle. 2 gal of gas in the tank. No real ballast.

Final weights:

622 603

611 553

The RR was 100 off when we started, but some of that was fixed by unbinding the suspension. We battled back and forth between ride ht and wt and finally settled on keeping it flat vs getting the wt dead on. Confirmed that no track difference or wheelbase difference was causing the problem (BTW, are 99s shorter on the R side?). We settled on the theory that on a car this light, 213 lbs on the L side is just hard to counter balance.

I know some guys put their fire bottle on the rail by the battery, but I didn't like exposing it to damage out there and that was confirmed when I got rear ended at the end of the year--the bottle would have been destroyed.

Any suggestions appreciated.

[Caveman-kwebb99]

We did an alingment and balance last week. First one on this car (and miata for that matter). Followed JD's script.

Total wt was dead on NASA rules with me in the seat (213), shirt in the pass side (22), and the 4L fire bottle is mounted in the trunk in front of the spare well in the middle. 2 gal of gas in the tank. No real ballast.

Final weights:

622 603

611 553

The RR was 100 off when we started, but some of that was fixed by unbinding the suspension. We battled back and forth between ride ht and wt and finally settled on keeping it flat vs getting the wt dead on. Confirmed that no track difference or wheelbase difference was causing the problem (BTW, are 99s shorter on the R side?). We settled on the theory that on a car this light, 213 lbs on the L side is just hard to counter balance.

I know some guys put their fire bottle on the rail by the battery, but I didn't like exposing it to damage out there and that was confirmed when I got rear ended at the end of the year--the bottle would have been destroyed.

Any suggestions appreciated.

I had that problem with my 01 last year with the old wieght and rules! I put my cool shirt in the back right corner! It will be tough with the new weight, not sure how your car was built, the cage may be a heavy one.

[davew]

You don't give ride heights, but you have 39 pounds of cross weight, WAY TOO MUCH. You should be 10 pounds max.

Dave

[Kyle Burkhardt]

Box won't fit in the rear (too tall).

Ride heights are (measured from subframe bolts):

2 7/16 2 2/14

3 9/16 3 11/16

Camber is 3 in the front, 2.5 and 2.25 in the rear (L/R respectively). 0 toe all around.

[davew]

You have chosen a measurement point that is not used by anyone else. What subframe bolts are you using? Subframe to chassis, subframe to subframe brace, subframe to contol arm???

That does not make it wrong, but no way to compare if you are too low or too high.

I would put more camber in the rear and add a little toe in to the rear and toe out to the front. Lower left rear 1/2 turn and the right rear up 1/2 turn

Dave

[Kyle Burkhardt]

You have chosen a measurement point that is not used by anyone else. What subframe bolts are you using? Subframe to chassis, subframe to subframe brace, subframe to contol arm???

That does not make it wrong, but no way to compare if you are too low or too high.

I would put more camber in the rear and add a little toe in to the rear and toe out to the front. Lower left rear 1/2 turn and the right rear up 1/2 turn

Dave

Thanks, Dave. I don't know which bolts they were using (I was in the car!). Couldn't get reliable measurements off anything else (the car's been racing for 12 years). Where do you measure from when your pinch welds look like a bed skirt?

[Kyle Burkhardt]

Thanks, Dave. I don't know which bolts they were using (I was in the car!). Couldn't get reliable measurements off anything else (the car's been racing for 12 years). Where do you measure from when your pinch welds look like a bed skirt?

FWIW, we used the rear subframe bolts on both the front and the rear subframes at the point where they attach to the body.

[Glenn]

Thanks, Dave. I don't know which bolts they were using (I was in the car!). Couldn't get reliable measurements off anything else (the car's been racing for 12 years). Where do you measure from when your pinch welds look like a bed skirt?

I have in the past put perm. marker lines on all 4 corners on the lower rocker panel, it is a consistant measurement although its only relative to your car. At least you can get repeatable results.

[davew]

Rear subframe attaches to the body about 12 inches off the ground???

[Jim Drago]

You don't give ride heights, but you have 39 pounds of cross weight, WAY TOO MUCH. You should be 10 pounds max.

Dave

Says who? That is 50.8 on cross? I have run far more and far less. The heavy set Asian kid that won last week in Atlanta had nearly 52% in his car?
Jim

[Jim Drago]

Box won't fit in the rear (too tall).

Ride heights are (measured from subframe bolts):

2 7/16 2 2/14

3 9/16 3 11/16

Camber is 3 in the front, 2.5 and 2.25 in the rear (L/R respectively). 0 toe all around.

Kyle
Not uncommon for RR to be lighter and a little higher, especially when you have little to no ballast on r/s. The closer you can get them the better, but at your weight and min car weight, you will never get them very close.
Coming from a guy who once had 20 ls of ballast in his car in 2009
Jim

Jim

[Kyle Burkhardt]

Thanks guys.

I had an accident last year and that end was hit (the subframe and suspension were all ok and checked out on the rack). That was always in the back of our head. Good to know that's not out of the range of normal on these cars. Sounds like you agree with my suspension engineer.

[Bench Racer]

Sounds like you agree with my suspension engineer.

Jim-bo, I thought you were over the top with your personal thingy hanging out of your building but this guy has a "suspension engineer".

Sorry Kyle, the devil made me do it.

[Johnny D]

Thanks guys.

I had an accident last year and that end was hit (the subframe and suspension were all ok and checked out on the rack). That was always in the back of our head. Good to know that's not out of the range of normal on these cars. Sounds like you agree with my suspension engineer.

Not sure if you want to equal it up and go over?
Do you have the OEM size battery in there?
Sounds like you didn't use enough bondo on the repair.
J~

[Kyle Burkhardt]

Jim-bo, I thought you were over the top with your personal thingy hanging out of your building but this guy has a "suspension engineer".

Sorry Kyle, the devil made me do it.

Hehe. My secret weapon. He's a long time friend. We came up together in VWs. He was a mechanical engineer and loved the car stuff so much, he went back to school to learn suspensions. He's headed up Grand Am teams, vipers, and ferrari challenge. It was cool seeing him take the analysis of our problem to the next level.

Not sure if you want to equal it up and go over?

That's our next question. What's better: balance or lighter?

Looking forward to driving it this weekend. I bought it last summer and drove it two weekends without doing an alignment and it was cornerbalanced as a SSB car (full interior which I removed) with a driver that weighed 70 lbs less than me. It had a wicked rake to it.

[dmathias]

IMHO forget about measuring ride height from anywhere on the chassis to the ground, it will never be accurate. The dimension that matters is the distance from the top of the shock to the bottom of the bumpstop.

[fishguyaz]

IMHO forget about measuring ride height from anywhere on the chassis to the ground, it will never be accurate. The dimension that matters is the distance from the top of the shock to the bottom of the bumpstop.

that makes alot of sense.
so for a guy with crushed pinch welds where does the 4.5" ride height measured from a good pinch weld correlate to the distance from the top of the shock to the bottom of the bumpstop.
4.5" in JDs guide = X with this method?
what does X =?
thanks

[dmathias]

Why not just measure the shock-to-bump stop gap?

Some bright folks on this site have made a go/no go gauge from a coat hanger.

In the garage I have raised my car with jackstands under the control arm (be very careful doing this, it's easy for a stand to kick-out) so that the weight of the car is on the suspension. Place a driver equivalent of weight in the seat. With the wheels off it's very easy to see the ride height.

[FTodaro]

that makes alot of sense.
so for a guy with crushed pinch welds where does the 4.5" ride height measured from a good pinch weld correlate to the distance from the top of the shock to the bottom of the bumpstop.
4.5" in JDs guide = X with this method?
what does X =?
thanks

I have been told, (see thread in set up guide), 5/8 to 3/4 of an inch

[Juan Pineda]

Kyle,

Wow, your car is really out of square if the ride height measurements you gave are right -- 7/16" twist!

Forget any ground clearance measurements. Measure your bump stop clearance: 5/8-3/4" is the goal. But if your car is really that out of square, then you obviously won't be able to get equal amounts under each shock. Try to EVEN them out as best you can with a minimum clearance of 5/8-3/4".

The LF will always be heavy and the RR will always be light if you achieve 50/50 cross weights, which is a good target unless you are trying to add wedge. The cross weights you quoted are off to begin with. To get CLOSER, raise the LF and RR by 1/2 turn. That will change the cross weights in the right direction while keeping the tilt approximately the same. (The total ride height will increase ~1/16", not a big deal.) If that adjustment doesn't get you to 50/50, then LOWER the other corners by 1/4-3/4 turn. Repeat.

Remember tilt is totally independent of cross weights. You can get 50/50 weight and have the car arbitrarily tilted in any direction. So once you get the weight right, it's time to level the car.

In general I first try to get the 50/50 cross weights while getting the car level side to side without worrying about height. This can usually be done by adjusting only ONE corner at a time. Then I adjust the front and rear heights to achieve my target ride heights. The height of one end of the car can be changed without significantly affecting cross weight or side to side tilt by adjusting BOTH sides of that end by the same amount.

-Juan