While driving my wife's car on a roadtrip this weekend, it dawned on me that I hadn't checked to see whether my spare tire in the trunk actually fits over the M3 brakes. So once we got home, I pulled it out of the trunk and took a couple measurements of the 16" donut spare that verified, no, it will not clear the M3 brakes. I've been carrying 26lb of dead weight for no reason. Gone now.
This got me thinking about weight some more, and particularly how it relates to roll couples (much of your roll stiffness is dictated by roll center height and CG height) so I decided to add a quick calculation of roll degree change to my weight calculator since I've already modeled the roll center height (of the front at least) here. I assumed 4" for the rear and entered 3" into the calculator as it would average at the CG. While I was at it I ordered an 18.5lb 60Ah antigravity battery.
Playing around with the numbers yields some interesting things! Removing the sunroof on an e46 touring means your car will roll almost exactly 3% less in a corner, these numbers should be almost exactly the same as a regular e46 coupe/sedan with the non-m sedan having the most benefit from the change (taller roof, lighter car). My roof rack setup makes the car roll almost 5% more alone! Anyway, it's attached if anyone is interested in doing their own math. Mine points to a pretty easy 150lb weight removal opportunity which results in 49.8/50.2 F/R weight distribution (again, with a full tank. 51/49 empty), assuming I can make a hitch mount for the bikes that doesn't add a bunch of weight.
This got me thinking about weight some more, and particularly how it relates to roll couples (much of your roll stiffness is dictated by roll center height and CG height) so I decided to add a quick calculation of roll degree change to my weight calculator since I've already modeled the roll center height (of the front at least) here. I assumed 4" for the rear and entered 3" into the calculator as it would average at the CG. While I was at it I ordered an 18.5lb 60Ah antigravity battery.
Playing around with the numbers yields some interesting things! Removing the sunroof on an e46 touring means your car will roll almost exactly 3% less in a corner, these numbers should be almost exactly the same as a regular e46 coupe/sedan with the non-m sedan having the most benefit from the change (taller roof, lighter car). My roof rack setup makes the car roll almost 5% more alone! Anyway, it's attached if anyone is interested in doing their own math. Mine points to a pretty easy 150lb weight removal opportunity which results in 49.8/50.2 F/R weight distribution (again, with a full tank. 51/49 empty), assuming I can make a hitch mount for the bikes that doesn't add a bunch of weight.
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