mikeo632
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| posted on 27/7/26 at 02:55 PM |
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Front suspension pick up points - Castor/camber?
Our Locost has been on the road for over 10 years, & has racked up over 11,000 hard miles on road & track. Over that period, we have developed
the car, but the 1 area that has never been good is steering self centring (specifically the lack thereof!).
We were running with max castor, but absolutely no self centring. This caused issues, especially on track days, culminating in my nudging the barrier
last time out, bending a lower wishbone. (That’s my excuse!)
The suspension runs rose joints all round, & as far as I am aware, the chassis is “Book”.
I have 2 new lower wishbones, but really want to take this opportunity to rectify the steering issue, hence this request for help.
On dismantling, the pick up brackets appear to be similar to those in pictures of 750 race cars, although the front ones are rotated slightly
rearwards, so they are at an angle when viewed from above compared to the rears. If we were running bushed mounts, this could never work as the
mountings are not in line, but as I originally spec’d rose joints, I wonder if this was the reason as it centralises the front rose joint in line with
the wishbone?
The top wishbones are asymetrical, allowing greater castor if fitted one way, & when I trial-construct the suspension taking this into account,
(admittedly without spacers either side of the joints for speed of assembly), there appears to be ample visual castor comparing the top ball joint
position to the bottom viewed from above. The centre of the top ball joint appears to be a maximum of approx 4cm rear to the bottom joint.
The help/advice I need is as follows:
Do the current pick up points sound standard/acceptable for the rose jointed suspension to perform correctly on a road/track car?
What castor angle do people set for road/track use?
Is there a way to measure castor using the 4cm measurement approach above? (the car is up on a ramp with the engine currently out).
What camber measurement is best set for road/track use?
Finally, whilst the front end is apart, should the tie-rods from the steering rack to front hubs run parallel to the ground with the car loaded &
on it’s wheels, or should there be an angle up or down between the rack & hubs?
Apologies for the length of post & number of questions, but advice/pics etc would be gratefully received!
PS: Would attach pics, but don't know how!
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mikeo632
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| posted on 27/7/26 at 03:57 PM |
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Pics (hopefully).
Think I have just learnt how to post images?
https://i.postimg.cc/gk9G7ss0/1000016714.jpg
https://i.postimg.cc/DzN9XfY8/1000016733.jpg
https://i.postimg.cc/FKw6KW7B/1000016736.jpg
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JC
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| posted on 30/7/26 at 04:05 AM |
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Hi there,
I can only see your first photo! I find it easier to upload them to the archive here and then paste the forum URL.
Anyway…. I’m sure you have battled your way through the search function on here as Self-centering was always a hot issue back in the day!
What front uprights are you using? From the one photo I could see, it didn’t look like a cortina upright, which is as per book spec?
Front wishbones should be fitted in the orientation that puts the top ball joint as near the back of the car as possible.
Ideally the steering arms should be level when the car is stationary ie zero load.
How bad is the self centering? If you drive hands off in a slight turn, does it return to neutral?
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Rod Ends
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 posted on 30/7/26 at 06:45 PM |
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quote:
What front uprights are you using? From the one photo I could see, it didn’t look like a cortina upright, which is as per book spec?
Agree.
Cortina uprights:
[img]
 
Rescued attachment Cortina-Uprights.jpg
[/img]
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adithorp
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| posted on 1/8/26 at 06:00 PM |
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If you also know the distance between the upper ond lower ball-joints (a), in addition to your 40mm (b) set back then a bit of maths will get you the
castor angle. a/b = sine of your castor
Or if you've got a camber gauge... https://youtu.be/ox1TOwI2tD8?is=q6-pTVkSXzvvUNjO
You probably want 6-8⁰.
Ideally track rods, should have the inner joints on a line drawn between upper and lower wishbone mount centres (viewed from the front). The angle of
the tack rod should parallel to the lower arm (if inner pickups are the same distance appart as the outer joints).
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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