"Scrub Radius"

[George Bynum]

I was using one of the on-line tire and wheel size comparison sites, and ran across a new dimension reported, scrub radius. Google is my friend, but didn't help me much. I gather that it (depending on amount and whether positive or negative) affects "friction" thus fuel economy and also handling.

Would one of you vehicle suspension guys comment on whether it matters?

 

[leeharvey418]

The only friction it really affects is the friction that has to be overcome when turning the front wheels while at a stop.

Unless one gets stupid with wheels and spacers, it'll never be an issue.

 

[Olas]

I've had a few beers so I won't get super-wordy, but this video is the best and most succinct description of scrub radii I've seen so far
https://m.youtube.com/watch?v=As1_XGkrMfI

 

[d00df00d]

Originally Posted By: George Bynum
I was using one of the on-line tire and wheel size comparison sites, and ran across a new dimension reported, scrub radius. Google is my friend, but didn't help me much. I gather that it (depending on amount and whether positive or negative) affects "friction" thus fuel economy and also handling.

Would one of you vehicle suspension guys comment on whether it matters?


Scrub radius affects how your front tire moves as you steer.

If scrub radius is 0, then the tire pivots around the center of the contact patch as you steer. Nice and simple.

If scrub radius is not zero, the tire gets dragged in an arc as you steer. That means more friction, higher steering effort, etc. It also means the wheel's location changes with steering input, which may or may not be a good thing.

I'd expect this stuff to affect handling more than fuel economy, but I can see it affecting both depending on how the rest of the suspension is designed.

 

[Tegger]

Originally Posted By: d00df00d
If scrub radius is 0, then the tire pivots around the center of the contact patch as you steer.

Yep.

Images help a LOT. When Googling for stuff like this, use Google Images, not the default Google Web.

Example search:
https://www.google.com/search?q=scrub+ra...e0OmiVvHFiGM%3A

 

[Le_bow_ski]

If handling is important to you, than scrub radius is something you'll want to pay attention to. Cruising down the highway commuting to work, it probably doesn't matter much in the scheme of things.