What tire pressures are you using in each corner? What are your tire temps
when coming off the track? Other items to consider early -- less air in the
rear tires will reduce understeer as will an anti-roll bar in the rear.
Duncan
(Texas)
Sent from my iPhone
> On Sep 19, 2015, at 12:21 PM, John Hasty <jhasty@mhc-law.com> wrote:
>
> Wow...and all this time I just thought old, narrow tracked, front engined
> English cars naturally pushed (NASCAR term) in right corners!
>
> Sent from my iPhone
>
>> On Sep 19, 2015, at 11:21 AM, "Marcel Van Mulders"
>> <van.mulders.marcel@telenet.be> wrote:
>>
>> Barry,
>> The cross weight 2% off is a lot and should be avoided. It should be very
>> nearly to 50% with the driver on board. So forget about the goal that the
>> left front wheel and the left rear wheel should have the same load.
>> About Schroedar's explanation : that is right when the car has very much
>> power (more power understeer out off a corner because of the faster
>> acceleration when the inner wheel has more load/less traction loss( better
>> load distribution on the driven wheels)). A simpler explanation with that
>> weight distribution for our less powered cars is the left front wheel being
>> more loaded than the right front wheel(when the car is at rest), hence more
>> understeer in a corner to the right than in a corner to the left. Maybe we
>> have to accept understeer in slow corners but it can be equal left and
>> right, when the cross weight is 50%, driver included.
>> Most circuits are clockwise, so most corners are to the right : moving
>> weight to the right is always a good thing. Battery, fire exstinguisher and
>> fuel tank should be as far to the right as possible. I've moved the complete
>> body of my car(TR4A) an inch to the right in respect to the chassis :
>> without driver, the left weight is equal to the right now and the front to
>> rear is 50.2% whith 25 litres of fuel.
>> This is all only an opinion of course, without pretending that it is correct
>> or important!
>> Marcel
>> -----Oorspronkelijk bericht-----
>> Van: Fot [mailto:fot-bounces@autox.team.net] Namens Barry Munson
>> Verzonden: zaterdag 19 september 2015 6:12
>> Aan: 'FOT'
>> Onderwerp: [Fot] TR3 Weights
>>
>> Amici - With the recent string discussing weights and currently dealing with
>> a TR3 which understeers in hair pins and decreasing radius corners (right
>> turns being the worst) but is neutral and very controllable in high speed
>> corners, left or right, I took the opportunity at a recent event to explore
>> the weight distribution on the TR3 and using the data try to determine
>> whether I had a tire issue or there was something inherent with the weight
>> distribution that was contributing to the understeering problem.
>> First a bit of background. The car is a 1959 TR3A that I use as my daily
>> driver in the summer and it takes me a day to convert it to racing
>> configuration. The weights below are for the car in its racing configuration
>> but includes the battery in its stock position, heater, windshield wipers,
>> headlights and front and rear bumpers. The car has a complete TR6 front
>> suspension (2 deg. neg. camber, 3 deg. pos. castor, 1/32 toe-in), TR6 comp.
>> front coils and comp. rear leaf springs and a 7/8 anti-roll bar.
>> Static weight, ie no driver, but with 5 gals. of fuel is 2009 lbs.
>>
>> LF - 564 RF - 518
>> LR - 462 LR - 465
>>
>> Front wt. - 1082 53.9%
>> Rear wt. - 927 46.1%
>> Left wt. - 1026 51.1%
>> Right wt. - 983 48.9%
>> Right Cross wt. - 980 48.8%
>>
>> I include these weights more for information than anything else since the
>> more relevant weights are with the driver and all his equipment in the car.
>>
>> With the driver and equipment the total weight was 2221 lbs.
>>
>> LF - 638 RF - 515
>> LR - 547 RR - 521
>>
>> Front - 1153 51.9%
>> Rear - 1068 48.1%
>>
>> Left - 1185 53.4%
>> Right -1036 46.7%
>>
>> Left Cross wt. - 1159 52.2%
>> Right Cross wt. - 1062 47.8%
>>
>> So what does this mean and how do I interpret it especially considering the
>> understeering problem that I'm dealing with. Well that's not easy. I'll
>> include a couple of quotes to see if that clarifies the issue - or maybe
>> not......
>>
>> From Per Schroedar, Grassroots Motorsport - " ....Left cross weight >50% the
>> car will likely understeer in a right hand turn because right rear tire
>> carries more load so the car drives off the right hand turn better. But in a
>> left turn the opposite occurs and the handling is worse. In almost all cases
>> the loss of corning performance in one direction is greater than the gain in
>> the other direction." Not sure that I completely understand this.....
>>
>> From Dennis Grant, Autocross to Win, Farnorthracing.com -
>>
>> "Adjusting corner weights is one of those things that is part of your
>> baseline setup, but finding any sort of agreement on just how to set corner
>> weights is next to impossible. It seems everybody has their own favourite
>> formula and magic sequence.
>>
>> I'm no different.
>>
>> My method takes as a given that your car is, being production based, almost
>> certainly left side and front end heavy, thanks to the packaging of the
>> driver (offset left) and the engine/transmission (offset front). There are,
>> of course, exceptions, but for the majority of us, the physical distribution
>> of weight inside the vehicle is asymmetrical - and so then will be the
>> corner weights.
>>
>> No amount of twiddling spring perches or cranking down on load bolts can
>> compensate for 200+ lbs of driver offset 10 inches left of the vehicle
>> centreline. Unless there is a corresponding mass in very nearly the same
>> location (in plan view) the corner weights will be offset left.
>>
>> So then, the question becomes how to best minimize the effects of the
>> asymmetric weight distribution. If we have to live with it, at least we can
>> reduce the effects and keep things reasonably balanced.
>>
>> Unless you only have left turns to deal with, you don't want to talk about
>> "cross weight" or "wedge". Those can be helpful in setting up a car that has
>> purposeful lateral static weight distribution bias because all turns are in
>> the same direction, but we don't play that game. It doesn't help at all that
>> most electronic racing scales sold in North America are intended for the
>> roundy-round guys and so will happily show you cross weight like it was the
>> magic ticket - it isn't.
>>
>> Instead, I like to set up a car so that it has equal left weight front and
>> rear; that is, the portion of the left side weight on the front wheels is
>> the same as the portion on the rear wheels, by percentage. If the car has
>> 52% front left weight, then it should have 52% rear left weight. Why? So
>> there's no diagonal bias and no static twisting moment. It seems to keep the
>> car more predictable."
>>
>> OK, using Grant's thought process and his Corner Weight Calculator here's
>> what the TR3's corner weights would look like:
>> Take 23 lbs out of the left front and right rear and add 23 lbs to the right
>> front and left rear which would give you the following distribution -
>>
>> Left Front - 615.2 Right Front - 537.8
>> Left Rear - 569.8 Right Rear - 498.2
>>
>> Front Left - 53.34%
>> Rear Left - 53.37%
>>
>> Left - 1185 53.35%
>> Right - 1036 46.65%
>>
>> Left Cross wt. - 113.0 50.11%
>> Right Cross wt. - 1108 49.89%
>>
>> Hmmmmm need to think about this.........
>>
>> Barry.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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