you go wayne...excellent explanation...into my reference manual this text
goes!!
----- Original Message -----
From: wizardz <wizardz@maxinter.net>
To: Wayne Burton <Wayne_burton@bc.sympatico.ca>; <spitfires@autox.team.net>
Sent: Friday, September 17, 1999 2:06 PM
Subject: Re: Spring sag on Spitfire (long)
>
> Thank you Wayne!
> Noone I've talked to before (not the list as of yet) ever believed
> me about the effects of the rear on steering.
> As you mentioned the radius arms... are called that...FOR A REASON!
> To extend the statement abit that .... Wayne made...
> not only does the wheelbase change in a turn (wheel to wheel per side)
> but the outside wheel on the turn...toes out slightly, while the inside
wheel
> will toe in. As Wayne stated.. becoming an active part of the steering.
> this toe change is also affected by rise hieght and body roll.
> Hence the sensitivity to the sway bar and body roll stiffness.
>
> This is also one of the reason a sway bar on the back end of a Spit...
> if setup correctly.... is not a good idea.
>
>
> Paul Tegler
> 1973 BGT - Daily Driver
> Rat - 1980 Spitfire w/ O/D - in re-hab
> Punkin' - 1978 Spitfire - in Superb Shape!
> email: wizardz@toad.net http://www.teglerizer.com
>
>
> -----Original Message-----
> From: Wayne Burton <Wayne_burton@bc.sympatico.ca>
> To: spitfires@autox.team.net <spitfires@autox.team.net>
> Date: Friday, September 17, 1999 3:54 PM
> Subject: Spring sag on Spitfire (long)
>
>
>
> Hello All,
>
> I've been driving and maintaining spitfires since 1978. Currently on my
8th
> one, and I love them :)
>
> I've had all the variations of the rear suspension fixed, swing, rotoflex
> etc. and in every case I still remember the BL service tech's explanation.
> The toe-in of the rear suspension is responsible for keeping the car at a
> correct ride height and removing some of the load from the spring. It must
> be adjusted with the 'normal' weight of the passengers in the car. AND you
> must roll the car back and forward without aid of the engine to settle the
> suspension before starting.
>
> The transverse leaf spring is the upper link of the suspension. The lower
> link is in two parts... The axle (or lower wishbone in the GT6 rotoflex)
and
> the rear RADIUS ARM are the lower link.
>
> The fixed spring will still allow a bit of flex across the spring due to
the
> mounting system and the properties of metal. The swing spring will allow
> more flex across the spring. Therefore, unless there is a definite sag
(over
> 1" in ride height) there is likely not a lot wrong with the spring.
>
> The radius arm is the member which actually locates the rear wheel within
> the wheel arch, and if you look carefully, at the correct ride height, the
> radius arm is not parallel to the chassis of the car or the road. It is
> angled down.
>
> This is what gives the rear suspension in the spitfire an active part in
the
> handling of the car. As the spring compresses on the outside of a corner,
> the wheelbase on the inside gets slightly shorter. The outside wheel gets
> slightly longer. This allows the rear to become part of the steering
system
> of the car. When driving in a straight line, bumps will be effective on
both
> wheels due to the spring, and the lengthening and shortening of the
> wheelbase has no effect. The slight toe in will assist the spring and
shocks
> in bringing the rear ride height to the 'normal' setting.
>
> If the rear toe is not adjusted properly or evenly, or the busings in the
> rear suspension are worn, the handling and 'settling' are affected. In
> addition the tendency to 'sag' one side is enhanced. By having the rear
toe
> adjusted and 'squared' the car will ride and sit evenly when driven and/or
> rolled in a straight ahead condition.
>
> If, however, you normally pull into a curb (parking, etc) you will notice
> that the inside of the corner is usually lower than the outside. Doing the
> opposite will reverse the effect. And if the bushings in the radius arms,
> spring eyes, etc are worn, the effect is worse. This is because the
> suspension doesn't have enough rolling time to settle correctly.
> Additionally, if you back up (reverse), the ride height will actually
> increase slightly.
>
> My current spitfire is a 1963 Mk I (original 1 owner) with the original
> spring. (Yes, I know the prior owner!!) It exhibited serious symptoms when
I
> got the car. After replacing all of the suspension bushings (and many
other
> things, not related to this) the car drives and sits squarely on its
tyres.
> It handles exceptionally well up to the point of 'squealing tire hop'
> (another story), and comes to a rest in my driveway (20' long) straight
and
> true. However, If I turn while coming to rest, the inside of the turn is
> always slightly lower than the outside.
>
> A note of caution, however. I would suggest that you have this done at an
> alignment shop that works on VW bugs, because most of the other shops
don't
> have a clue what '4 wheel alignment' is all about, nor will they attempt
to
> correct the tracking of the rear wheels, which is what I believe most of
you
> are experiencing.
>
> Since I found out about this, it is one of the first things that I have
done
> on any of my Spitfires, and I have never had a serious sag problem. Nor
have
> I replaced any springs, except the one I broke when I hit a curb sliding
> sideways at speed...
>
> Good luck to you all, and I hope that this will 'settle' the spring for
some
> of you at least...
>
> Wayne Burton
> 1963 Triumph Spitfire4
> 1966 Triumph 2000
> 1954 Austin A40 Somerset
>
>
|