John McCormack Posted April 29, 2020 Report Share Posted April 29, 2020 My long door TR2 has 1 degree negative caster on the left front. All other geometry measurements are well within limits. Do we have a steering expert who can tell me whether this is significant or not and what effect, if any, this might have on the cars steering? I could take the spring out and locate the top wishbone mount as far aft as possible to maybe reduce the caster to -0.5 degrees but I would only bother if -1 degree is an issue at all. Quote Link to post Share on other sites
stuart Posted April 29, 2020 Report Share Posted April 29, 2020 May well make it centre better on steering return from that side, sounds as if the turret is slightly mis-aligned. Stuart. Quote Link to post Share on other sites
John McCormack Posted April 29, 2020 Author Report Share Posted April 29, 2020 9 hours ago, stuart said: May well make it centre better on steering return from that side, sounds as if the turret is slightly mis-aligned. Stuart. Thanks Stuart. The TR specs I believe are for 0 degrees caster. I figured that -1 degree wouldn't be significant and hardly noticeable in driving. The steering on this car however does feel different to my other TR2 which has excellent original steering. The long door car doesn't pull left but it does turn in to the left easier than right i.e. the steering is lighter to the left and heavier to the right. It isn't binding or anything like that and not a major issue (most drivers might not even notice it) but I would like to know what is causing it. With the wheels off the ground the steering is the same left or right, lock to lock. Interestingly, the wheel has slightly more resistance turning away from centre and less resistance coming back to centre, in both directions. The car has a Revington spring loaded steering box top. Quote Link to post Share on other sites
stuart Posted April 30, 2020 Report Share Posted April 30, 2020 This is why the factory went to 3 degrees castor on the TR4 as it makes for better self centring. I have had problems with early chassis when the lower inner wishbone bar has been bent, see attached pictures. Not too difficult to remedy as in bottom picture as that section is available in one piece. Stuart. Quote Link to post Share on other sites
John McCormack Posted April 30, 2020 Author Report Share Posted April 30, 2020 There is no accident damage to the chassis. It is possible that a manufacturing issue at build resulted in the minor variance. It is only a couple of mm in it. I could take the spring out and make sure that all the play is taken up in the right direction to get it as close as possible to 0 caster. But the caster isn't a lot and it could be something else. Quote Link to post Share on other sites
stuart Posted April 30, 2020 Report Share Posted April 30, 2020 8 minutes ago, John McCormack said: There is no accident damage to the chassis. It is possible that a manufacturing issue at build resulted in the minor variance. It is only a couple of mm in it. I could take the spring out and make sure that all the play is taken up in the right direction to get it as close as possible to 0 caster. But the caster isn't a lot and it could be something else. My above pictures were taken from a running driving car, its easy to miss just a small variation in those lower wishbone bars, the early chassis are very flimsy.Have a look straight down from above as you can see it from above just to be sure. Stuart. Quote Link to post Share on other sites
John McCormack Posted April 30, 2020 Author Report Share Posted April 30, 2020 (edited) 2 hours ago, stuart said: My above pictures were taken from a running driving car, its easy to miss just a small variation in those lower wishbone bars, the early chassis are very flimsy.Have a look straight down from above as you can see it from above just to be sure. Stuart. I’ll do that. Thank you. Do you think the caster would have the steering effect I’ve described? Edited April 30, 2020 by John McCormack Quote Link to post Share on other sites
stuart Posted April 30, 2020 Report Share Posted April 30, 2020 2 hours ago, John McCormack said: I’ll do that. Thank you. Do you think the caster would have the steering effect I’ve described? Yes I do TBH Stuart. Quote Link to post Share on other sites
John McCormack Posted May 2, 2020 Author Report Share Posted May 2, 2020 On 4/30/2020 at 11:52 PM, stuart said: Yes I do TBH Stuart. I have been thinking about how to correct this caster angle issue. My old aviator navigation skills included the 1 in 60 rule - if my heading is out by 1 degree I will be 1 mile off track after 60 miles. To move the angle of the vertical link 1 degree I need to move the top ball joint 1/60th of the length of the vertical link. The link is approx 200mm long between the axle and top ball joint, I'll measure it accurately before I do any work. Therefore to correct 1 degree -ve caster to 0 degrees, I need to move the fulcrum pin rearwards by 3.33mm (1/60th of 200mm). I can achieve this by moving the fulcrum pin mounting holes 3.33mm towards the front i.e. to allow the pin to be 3.33mm rearwards.. I expect that there would be enough movement in the lower wishbones and trunnion to allow this. Any problems with this solution? Quote Link to post Share on other sites
Drewmotty Posted May 2, 2020 Report Share Posted May 2, 2020 Sounds ok as a solution but I would use the nylatron bushes in the top wishbones if you really want to hold the geometry. In fact if you have rubber or even poly bushes then the bushes could be at least partly to blame for the discrepancy. Quote Link to post Share on other sites
John McCormack Posted May 3, 2020 Author Report Share Posted May 3, 2020 14 hours ago, Drewmotty said: Sounds ok as a solution but I would use the nylatron bushes in the top wishbones if you really want to hold the geometry. In fact if you have rubber or even poly bushes then the bushes could be at least partly to blame for the discrepancy. Thank you. The top bushes are near new Superpro and it is all secure. Although there is no sign of accident damage I suspect Stuart is right that the pillar is slightly out. It could be as simple as the chassis got dropped on it. Quote Link to post Share on other sites
TomMull Posted May 3, 2020 Report Share Posted May 3, 2020 On 4/30/2020 at 4:49 AM, stuart said: This is why the factory went to 3 degrees castor on the TR4 as it makes for better self centring. I have had problems with early chassis when the lower inner wishbone bar has been bent, see attached pictures. Not too difficult to remedy as in bottom picture as that section is available in one piece. Stuart. Stuart, could you suggest a source for that bottom section. I don't seem to find it from the usual suppliers here in the US. Tom Quote Link to post Share on other sites
stuart Posted May 4, 2020 Report Share Posted May 4, 2020 15 hours ago, TomMull said: Hi Tom I got mine from Colin at CTM though now he has moved to France Im not sure if you could still buy from him, try the email at the bottom of this page. https://ctmengineering.co.uk/the-cars/tr2-tr3-tr3a/ Stuart. Quote Link to post Share on other sites
John McCormack Posted June 1, 2020 Author Report Share Posted June 1, 2020 Problem solved. My garage has been out of action due to a new driveway so I did some thinking and jacked the front of the car up. The right hand brakes and bearing were good. The left hand brake was binding quite badly, the wheel could be turned by hand but only with some pressure and it wouldn't spin freely. I adjusted the brake and then found the wheel bearing was too tight, not binding but quite a bit too tight. Slackened the nut one flat, put more grease in the cap and put it back together. Both front wheels spin freely and the brakes release nicely. This morning was my first chance to take it for a run and the steering is fine, very good actually. It turns both ways smoothly, holds a nice line on sweeping bends (Revington steering box top) and I had a big smile as I covered 25kms. I'm glad I didn't rush into dismantling my new front suspension. It is usually something simple with these cars. Quote Link to post Share on other sites
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