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Author: Subject: ideal scub radius
bart

posted on 29/2/20 at 05:36 PM Reply With Quote
ideal scub radius

Hi all
ok the question , if we forget about front upright design what scrub radius would be best
I have some ab performance uprights and can adjust the wheel off set to get 12.5 to 32.5 mm scrub radius
as I have not set the suspension lengths yet.
Fyi king pin 5.16 deg and castor 7.5 deg , ive set the castor at 7.5 so I can if wanted tilt the car up at the back and still have a decent castor max minus 1 deg

so wheel offset , set it to give 12.5 22.5 or 32.5 ?





BE ALERT > BRITAIN NEEDS LERTS

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SPYDER

posted on 29/2/20 at 06:06 PM Reply With Quote
Since you are using his upright design why not ask Andy Bates for a recommendation? He might be along in a minute.
I suspect he'll need more information though.

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AdamR20

posted on 1/3/20 at 07:05 AM Reply With Quote
There is no optimal, you need to tailor it to your personal preference and car use.

Higher values give 'heavier' steering and more feedback. Reduced (and negative) values the opposite.

From memory I'm running at least double your max value, and other kit cars have been near to 3 figures and still driven well.

That is quite a lot of caster btw... would usually expect to see numbers around 5.

[Edited on 1/3/20 by AdamR20]

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phelpsa

posted on 1/3/20 at 01:19 PM Reply With Quote
We had 110mm on our locost at one point and it was fine on crossply slicks, although the front corner weights were only about 85kg.... If I was designing for a lightweight car I would target 50mm. The only real downside to high scrub is the kick you get as the inside front locks, in a heavy car this can be quite aggressive.
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pekwah1

posted on 2/3/20 at 05:02 PM Reply With Quote
Out of interest, i have a striker with inboard suspension and a top pivot, how do you calculate scrub on this setup?
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AdamR20

posted on 2/3/20 at 06:06 PM Reply With Quote
Over 100! It was you I had in mind Adam when I mentioned that

Inboard suspension is no different: https://www.wheeldictionary.net/suspension_cutaway.jpg

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phelpsa

posted on 3/3/20 at 10:54 PM Reply With Quote
quote:
Originally posted by AdamR20
Over 100! It was you I had in mind Adam when I mentioned that

Inboard suspension is no different: https://www.wheeldictionary.net/suspension_cutaway.jpg


Just checked the Westfield geometry and thats at 85mm with Et13 wheels and 540mm tyres. Cortina uprights have a lot of scrub built in!

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