steering arm length....ideal

[jonny8]

If you can get a rack with the required travel and speed (mm/rev pinion) and packaging is not a problem do you want to go for the longest steering arms possible?

[jonny8]

If you can get a rack with the required travel and speed (mm/rev pinion) and packaging is not a problem do you want to go for the longest steering arms possible?

[Cement Legs]

Depends how much bump steer you want to add http://fsae.com/groupee_common/emoticons/icon_frown.gif.

Your steering linkage is closely tied into your front suspension geometry. Both should be worked out simultaneously to iterate to the desired solution having the best compromises.

2.5 cents

[jonny8]

Cement legs,
sorry its late here in the uk,i ment the longest with no/ v.little bump.
http://www.racerpartswholesale.com/images/bsdrawing.jpg

with reference to this i take it the longer you make the steering arm(if using rear steer) the further to the right of line 1 the outer tie rod will be located and thus the more bump. hmm. In that case what do you think would be good length? Am thinking betwen 50 and 70mm?
Thanks

[Travis Garrison]

Edit: I'm an idiot...I see what your getting at now...shorter arms would be stiffer...but I would worry more about rack placment and work on control arm deflection when it comes time to spec wall thickness for those parts...I'd be willing to bet you can save more weight worrying about rack placment (ie, no joints, thinner steering shaft, etc...) than you can by going with short control arms.

-Travis Garrison

[CMURacing - Prometheus]

jonny8-

where did you get that lovely diagram? i've been looking for some books specifically on suspension design to augment my millikan.

[jonny8]

CMU,

I got it off racerpartswholesale.com I believe. Just didi a search on google for bump steer and it was the first hit. Not a bad pic no.

[Dan B]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Travis:
...shorter arms would be stiffer...but I would worry more about rack placment and work on control arm deflection when it comes time to spec wall thickness for those parts...I'd be willing to bet you can save more weight worrying about rack placment (ie, no joints, thinner steering shaft, etc...) than you can by going with short control arms.

-Travis Garrison </div></BLOCKQUOTE>

Care to comment on the shorter arms being stiffer?

[Cement Legs]

How do you plan on adjusting your camber, inboard or outboard? Top or bottom? You may want to look into these before deciding on your tie rod location because they will greatly affect the way you adjust your toe in/out.

[abc]

how will shorter steering arm be stiffer?

[StevenWebb]

i've always thought the best way to go is to have tie rods as long as possible for a few reasons (overall steering ratebeing equal)

longer steering arms mean less force to slop out rod ends/rack/etc will be lower, it also means any slow created there (in mm) will have much less of an effect (in degrees) at the tyre.

longer also means you can change aspects of the car without adjusting toe or rack height. eg if your steering arm was halfway up the upright and really short, you may need to adjust toe if you adjust camber via the top upright clevis, where the change in toe for a long arm may be much smaller, not requiring re-adjustment.

[woodsy96]

Talk about dug up...

I don't believe that your tie rod length has any direct affect on if your camber affects your toe.

It seems to me that the only time you don't need to change toe when you change camber is if your steering knuckle is directly fore/aft of the point the upright pivots about when the camber changes

e.g. if the camber is adjusted at the top upright ball joint then your steering joint must be directly fore/aft of the lower upright balljoint.