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Fun with corner weighting at DTM

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Old Mar 23, 2008 | 06:15 AM
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Fun with corner weighting at DTM

First track event of the year is now less than a week away! When I last posted about my suspension revisions on DC Evo Club (http://forums.dcevoclub.com/showthread.php?t=9371), I had purchased a bunch of Whiteline and Energy Suspension bushings and bits, pulled the suspension apart, taken the pieces to DTM to have the bushings and so forth installed in the arms, and taken the pieces home to reinstall everything.

Next step in the process was to corner balance my Evo for the first time at DTM.

Although I've had my coilovers for a year and did a bunch of autocross and track events last year, when I had installed the coilovers I just set the ride heights even on both sides and kept approximately the stock rake. I thought about corner balancing the car, but my general impression was that our cars were pretty close (i.e., RF+LR about equal to LF+RR corner weights) even stock and it wouldn't make much difference. Besides, I didn't have time with all of the other things that I was more worried about (brakes, tuning, etc.) and didn't know a thing about how to corner weight a car.

Last year at the end of the season I told Nick that I was interested in getting more focused on optimizing setup this year, including corner balancing. So, yesterday we put the car on the scales for the first time and were pretty astonished with how off the cornerweights were.

Ideally, the crossweight (RF+LR) should be equal to 50% of the total weight. It's okay if it's a little off, but mine was not even close. The crossweight was off by over 300 lbs. and the percentage was around 43%! The biggest offender was the front left corner, which was over 1100 lbs. with me in the car, while the right front corner was well under 900 lbs. Also, the LR was substantially less than the RR.

My first thought was that I must of really messed up something when I installed the coilovers. Nick asked me how I set ride height and at first I couldn't remember. I mentioned that I thought maybe I had measured from the fenders (which is a bad thing to do). Anyhow, we dropped the front wheels off and Nick took the measurement the right way. Turns out that it was dead even on both sides, at which time I recalled that I actually had done the measurements using a micrometer and points on the suspension rather than the body. This was good news for my ego, but bad news for fixing the corner weights.

Anyhow, I won't go through a blow by blow of the process, but the long and short of it is that after numerous adjustments we got it dialed in well and the hugely assymetrical cross weights were nearly even. What was the most striking was how much tiny adjustments affected the corner weights. I think even Nick was surprised at this, but then when we considered that my car has much higher spring rates than the vast majority of Evos that come through the shop, it made some sense.

Anyhow, I'm very glad that the car is now corner weighted and I have no doubt that getting rid of the 300+ lb. differential is going to help a bunch. In a theoretical sense, corner weighting ensures that the car will turn right and left comparably well, but it's also known that when the cross weights are off, the degree to which the car is advantaged in turning one way, is much less than the degree to which the car is disadvantaged the other way. In other words, you pick up overall grip in both directions by corner weighting.

It was a ton of fun going through the process and learning how to corner weight a car. It also taught me a lesson about making assumptions on set-up. Thanks a bunch to Nick at DTM for being so patient and spending so much time walking me through all of the steps. It's not a complex process once you understand it (and its not entirely intuitive by any means), but it is definitely one that requires precision and attention to detail to do right.

Next stop is a DTM alignment and then some tweaks in the engine/tuning department before hitting the track.

Thanks for reading.
Old Mar 23, 2008 | 06:28 AM
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How much do they charge?
Old Mar 23, 2008 | 06:59 AM
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I'm sure that Rich would help you out for free...now that he's an expert!

BTW Rich...what time did you finish last night?

Originally Posted by mievoIX
How much do they charge?

Last edited by 59EVO; Mar 23, 2008 at 04:37 PM.
Old Mar 23, 2008 | 08:55 AM
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Nice rich... can't wait to see it at the track.
Old Mar 23, 2008 | 09:07 AM
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Originally Posted by mievoIX
How much do they charge?
DTM's normal charge is $150 from start to finish with adjustable aftermarket coilovers (there isn't anything they can do with just springs).

If you have more specific questions, I would give Nick a call (703-327-7047) or send a PM to "DTM."
Old Mar 23, 2008 | 09:15 AM
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Originally Posted by 59EVO
I'm sure that Rich would help you out for free...now that he's an expert!

BTW Rich...what time did you finish last night?
Me, an expert?! HAH!!!

We were there pretty late. By the time everything was put away and cleaned up it was close to 9pm. Your dog wouldn't have been happy with you if you had stuck around til the bitter end

Last edited by EVO8LTW; Mar 23, 2008 at 08:01 PM.
Old Mar 23, 2008 | 04:39 PM
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The survived and everything was dry when I got home!

I would've liked to have stayed, but my carpet would've suffered!



Originally Posted by EVO8LTW
Me, an expert?! HAH!!!

We were there pretty late. By the time everything was put away and cleaned up it was close to 9pm. Your dog wouldn't have been happy with you if you had stuck around til the bitter end
Old Mar 24, 2008 | 11:28 AM
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Originally Posted by EVO8LTW
DTM's normal charge is $150 from start to finish with adjustable aftermarket coilovers (there isn't anything they can do with just springs).

If you have more specific questions, I would give Nick a call (703-327-7047) or send a PM to "DTM."
THANKS.
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