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Re: TR Front Anti-Sway Bar - Wow!!! teamfat2.dsl.aros.net id f6B6Kex1095

To: Triumphs Mailing List <triumphs@autox.team.net>
Subject: Re: TR Front Anti-Sway Bar - Wow!!! teamfat2.dsl.aros.net id f6B6Kex10958
From: Pete & Aprille Chadwell <pandachadwell@mac.com>
Date: Tue, 10 Jul 2001 23:20:19 -0700
References: <200107110504.WAA07109@blackie.cruzers.com>
TeriAnn wrote:

>I've spent a lot of time chatting with TR3 & 4 racers about suspension. 
>The short answer is you want a stiff front and a stockish rear
>suspension. 
>
>Almost no one is racing with a rear say bar on a TR3 because it makes
>handling less predictable and it doesn't really help high speed cornering.

Fair enough
 I still have a stock front anti-roll bar on my TR6 and 
no rear bar.

Phil Ethier wrote:

>Not invariably for all cars.  Maybe for TR6 cars and TR4 cars. But maybe not
>even for all of them.
>
>Many cars have severe roll-understeer due to camber curve and other
>considerations.  VW Rabbits and MGBs spring to mind.  These cars generally
>will understeer LESS with the addition of a stiff front bar.

Most road cars are engineered with a lot of understeer, because 
understeer is a far more stable condition than oversteer and most 
drivers will react more intuitively to understeer than they will for 
oversteer.  It's safer, in other words.

But Phil, I must disagree
 if you go pick up a copy of Fred Puhn's 
"How To make Your Car Handle" or Carroll Smith's "Tune To Win," 
"Engineer To Win," or "Prepare To Win" or any other credible book 
written on the matter, you'll find this principle echoed frequently. 
It is indeed invariable and applies to all cars.  Race cars, road 
cars, FWD, RWD, 4WD
 whatever.  (well, alright, maybe it doesn't 
apply to a BMW Isetta)  But you must understand that the basic 
principle as set forth assumes that all other factors remain the 
same.  And you are VERY correct to point out that there are many 
other factors that contribute to steer characteristics and that every 
car will require different combinations of tweaks to achieve the 
desired steer characteristics.  But the tweaks will always go in the 
same direction following this basic principle.  Too much understeer? 
Increase rear roll-stiffness or decrease front roll-stiffness.

Also, you would be correct to point out that there are other tweaks 
you can do to effect steer characteristics without fiddling with 
roll-stiffness at all.  Fiddling with camber, toe, tire pressure, etc.

Funny you mentioned VW Rabbit, although I wish you'd mentioned VW 
Dasher instead (basically the same car, suspension-wise) because I 
used to drive a '76 Dasher.  I remember one fast left-hander I used 
to go around doing about 70 or 75 mph in the Dasher
 but I had 
temporarily removed the front anti-roll bar.  Finally I got around to 
reinstalling it, and was curious about whether the info in the books 
I was reading would be backed up by my experience.  With the bar now 
installed, I went around that same bend and the push in the front end 
was much more pronounced
 so much so that I recall thinking I was 
going to strike the telephone pole at the exit of the bend!  Adding 
the front bar again (increasing front roll-stiffness) DEFINITELY 
increased the understeer.  It is truly a universal rule in suspension 
tuning.  Some cars are more sensitive to it than others due to the 
many other variables, weight distribution, tire pressure, bushing 
deflection, alignment settings and suspension geometry just to name a 
few.

I would imagine with Spitfires, because of their swing-axle rear 
suspension and the limitations of that type of suspension, a guy 
would have to approach these things a little differently because the 
type of suspension you'd be dealing with would present other 
problems, but even so
 the principle always applies.  Increased 
roll-stiffness in the front = more understeer and/or less oversteer. 
Increased roll-stiffness in the rear = more oversteer and/or less 
understeer.  I strongly suspect that if anyone has achieved different 
results from this, they have changed SOMETHING else at the same time.

>Your guidelines are time-honored, but not invariable.  Every car's handling
>is a sum of all its parts.  The effect of a change may be unexpected.

Again, this eludes to the many variables that can pollute the 
results.  But I don't believe the principle would be time-honored if 
it wasn't invariable.

>I want to get a front bar for the TR4.  Then I will evaluate if I want to
>try the rear bar I have.  Installing the rear bar alone would be silly:  The
>car already lifts the rear wheel.

Precisely!  I have a rear bar for my TR6 as well, but do not have it 
installed.  You're right
 it'd be silly without going with a beefier 
front bar.  My car is already a handful when the roads around here 
get slick in the winter!

Best regards,

-- 
Pete Chadwell
1973 TR6

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