Can you get a good cross balance weight in front without a spare?

Maxhouse97 · 09-08-2010, 06:45 PM

Took out the spare, and with my fat ass in the driver's seat, my right front seems to lock up before the front left. Can those of you that run without a spare get good cross weight balance taking into account the spare's right side positioning and the driver's left bias?

Tyson Schmidt · 09-08-2010, 06:58 PM

Cross weight is independant of actual weight distribution. It can be changed by raising or lowering the adjuster on one corner, or both opposing corners. In other words, the mass stays the same, but the load on that corner can be changed through jacking.

(Ideally you would have both, which would result in both front L/R weights being identical and both rear L/R weights being identical at the same time, which would of course also give a 50/50 cross weight as well.))

So my guess would be the extra weight was helping mask a pre-existing corner weight imbalance.

Maxhouse97 · 09-09-2010, 02:59 AM

OK so you are saying that I should be able to get a good corner balance regardless of the weight. Is there any ill effect to driving with all of that weight on the driver's side (battery and driver in an already light front end)? I imagine that is why the factory put the spare on the passenger side, but I figured the 50lbs wasn't worth just making sure the cross weights were good.

tonythetarga · 09-09-2010, 03:39 AM

The spare played a role in crash safety more than anything else. As far as weight and corner balance goes, think about all the race cars or guys that convert their cars to track cars and strip out all the stock interiors and drop hundreds of pounds from all areas of the car. The corner balance 're-arranges' the cars weight over the wheels, taken with the driver in the car (or simulated weight) and 3/4's of a tank of fuel.

Wil Ferch · 07:02 AM

Not to sound rude....but the original question underscores a fundamental lack of understanding of getting proper corner weights. As someone here said, WHERE the various heavy masses are located is un-changable ( unless of course....you DO change things like battery location), but basically things "are where they are"....like the engine in the back, and this aspect is unchangable.

Let's go from there..... a 911 has a typical 40/60 front-to-rear weight distribution. Jacking around corner weights will do NOTHING to ANY TWO ADJACENT WHEEL TOTALs. Meaning?---> the rear ( if it started at 60% weight).....will always have 60% weight as a TOTAL of the rear two wheels. Aha !.....each *individual* rear wheel can be "off"....but the sum total of the two rear wheels will always be 60% if you started with 60%.

Same with the sides. If you started off with a 2% bias toward left...the TOTAL of the LF and LR will ALWAYS show 2% bias toward the left. The individual wheel-load may change.

How do they change?.... Increasing the press-weight of the RR will similarly affect the diagonal LF, and likewise any change on the LR will similarly affect the RF. Core---- any change at one wheel will similary affect its diagonal. Height and weight.

Also....targeting equal diagonals only makes real sense for (say) a formula car, where the architecture is equal in all plan-view directions. This is not true of our "tin-can" cars....the driver is off to the left, the battery to the left, spare to the right, etc, etc......

Interesting tidbit---> I had a spirited exchange with Randy Blaycock (sp?) a while back on these pages, a known recer, and I learned an important point. My original view was that each of the 4 corners of the car had a "different" target value based on where the vehicle's masses were located ( engine to rear, battery and steering hardware to the left, etc, etc)...therefore my thinking was that each front may end up different ( yet proper) accordingly, if we target "true corner balance". He convinced me that setting up a car, instead, with EQUAL FRONT ( Left-to-right) set up....although not truly "balanced" but now "weight-jacked"....is actually a good idea. That way, under heavy braking.....you get both front wheels to tend to lock up the same way. This is more desirable than getting true "corner-balance", and having the fronts lock unevenly under heavy track braking. The small "negative" setting up a car this way... is that the car will have ever-so-slightly different left vs right turn-in characteristics....but it is a compromise worth doing in promoting better threshold braking characteristics....

See.....simple ! ....