[Fot] FW: TR4A front suspension.

Tue Mar 10 12:13:06 MDT 2015

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Van: Marcel Van Mulders [mailto:van.mulders.marcel at telenet.be] 
Verzonden: dinsdag 10 maart 2015 19:04
Aan: 'Jack Wheeler'
Onderwerp: RE: [Fot] TR4A front suspension.

All the parts are TR-4A-TR6, so the trunnions are 3° (all TR trunnions that
have removable trunnion bolts are handed, trunnions with pressed in pins can
be 0° or 3°).
"...the lower trunnion should rotate around the bolt..." If I understand
what you mean, I don't believe this is correct : the trunnion bolt is
clamping the distance pieces (short pieces of steel tube that slide over the
bolt and rotate in the outer wishbone bushings) onto the trunnion and hence
the bolt, trunnion and distance pieces should rotate together and only the
wishbones can rotate in respect to the bolt (and trunnion and distance
pieces). I have assembled the suspension in this way, eliminating thus the
play of the trunnion on the bolt and this is the reason I had to drill new
holes , more to the rear, in order to get the upperr end of the uprights
between the outer ends of the upper wishbones. All parts and also the
chassis seem to be all right. Maybe I get it wrong anyway with the
assembling of the suspension parts
Marcel.

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Van: Jack Wheeler [mailto:jwheeler1947 at yahoo.com] 
Verzonden: zondag 8 maart 2015 23:40
Aan: Van Mulders Marcel
Onderwerp: Re: [Fot] TR4A front suspension.

Do you have the TR-4A uprights and trunions?  The TR-4A trunion is just the
brass piece that fits in between the lower wishbone arms and a bolt slides
through it, instead of the fulcrum pin (pressed into the trunion), as you
would have had on your TR-3.  The lower trunion should rotate on the bolt,
and the wishbone arm bushings.  There is a left and right hand, and when
properly installed, you should have about 3 degrees of positive castor on
both sides.  I raced a TR-4A for 25 years, so I know the suspension
intimately!  Good luck.

Jack

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From: Van Mulders Marcel via Fot <fot at autox.team.net>
To: fot at autox.team.net 
Sent: Sunday, March 8, 2015 5:35 PM
Subject: [Fot] TR4A front suspension.

In June 2014 I bought Bob Kramer's TR4A racecar after I crashed my TR3 at
the Zandvoort circuit (The Netherlands). It's a great car and it will get
better. Of my TR3, I only kept the engine and overdrive dogbox  Overhauling
the front suspension, I found that the lower trunnion was moving on the bolt
instead of the bushed lower wishbones : the distance pieces in the wishbones
where shorter than original, so the trunnion was not clamped by these
distance pieces when fastening the bolt. Correcting this, the upright has
less play now, only a little in the trunnion, and this upright with
balljoint can't be forced anymore between the outer ends of the upper
wihbones, the balljoint is 1/2" too far to the rear. Turning the upper
wishbones to the rear (by moving the fulcrum pin) isn't a good option,
because binding will occur. I've drilled new holes for the brackets for the
inner ends of the lower wishbones : the suspension is moving without any
binding now but I don't know if I will leave it like that. I wonder if
something is wrong with the uprights? (less than 3° caster?) If I measure
the caster, I find 2.2° on both sides, but probably that isn't proving
anything. The chassis is as new, no damage. Any idea's someone?
Another question : trying to get at zero bump steer, the best I get at by
moving the steering rack is a J : the wheels are toeing in when lowered more
than 3 cm below ride height (minimal to 5cm, then more and more toe in).
Bending the steering arms to the outside, almost touching the brake disks
now, has straightened the J a little.  Is it possible to eliminate the bump
steer completely, or have we(TR4A-TR6) to accept some bump steer in the
least important part of the suspension travel?
Marcel.

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