just wondering scrub radius question...
just wondering scrub radius question...
(OP)
If rear wheel drive cars generaly have positive scrub and some front wheel drive cars have negative scrub, what would be the effect of giving a rwd car negative?
(apologies if I got the pos and neg around the wrong way)
(apologies if I got the pos and neg around the wrong way)





RE: just wondering scrub radius question...
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RE: just wondering scrub radius question...
Also steering knuckles would need to be more complex or king pin inclination would need to be higher to overcome space constraints. This is also the case with FWD, but the need is greater, so the cost is more easily justified.
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RE: just wondering scrub radius question...
RE: just wondering scrub radius question...
RE: just wondering scrub radius question...
Cheers
Greg Locock
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RE: just wondering scrub radius question...
If it is a large amount (around 20mm or more), Is there a rule to make a negative scrub radius for FWD and a positive one for RWD?
Or, Always the positive one is recomended for the both?
RE: just wondering scrub radius question...
I don't think that rule works, neg scrub always seems better for me for traction and braking stability.
Cheers
Greg Locock
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RE: just wondering scrub radius question...
Actually I knew somethings about that, but, we have two pretty similar cars with a difference on their driving axle (FWD and RWD), and their scrub radiuses (that are according to the post of "bikesrfast"; - and +).
I used to hear about the necessity of negative scrub radius for preservation of stability in unequal braking conditions. As you said, it can be useful for traction stability too.
So, I think, We'd better change our RWD's scrub radius to a negative value instead of making it more positive.
Am I Right?
.
RE: just wondering scrub radius question...
KPI is bad. It has one good effect (returnability from high lock angles), I don't think it makes anything else better.
To be honest for a performance car I don't think neg scrub is at all important - if the steering wheel pulls when braking then you've actually told the driver something useful.
Cheers
Greg Locock
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RE: just wondering scrub radius question...
But I think negative scrub radius has a more important effect in an elastokinematic manner, directly on the tire and its linkages, whitout any need to turn the steering wheel!
& high lock angles?: Do you mean large steering angles which make returnability act reversely?
RE: just wondering scrub radius question...
" Do you mean large steering angles which make returnability act reversely? "
Yes
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.