Some info about bumpsteer

Topic: Some info about bumpsteer (Read 3541 times) previous topic - next topic

Some info about bumpsteer

Reply #15 – March 15, 2007, 10:11:50 PM

Yeah, I don't think it's meant to extend that much, if at all. Collapse yes, but extend? Not so much.

#45 will some out of #47 however....I've done it.

Lowring the rack up to 1" though is not going to lengthen the steering shaft 1".....

Some info about bumpsteer

Reply #16 – March 15, 2007, 10:15:17 PM

I don't think extending the wheelbase moves the P/S rack at all. That would screw up the ackerman.

Hey, if you're doing all this upgrading...you might as well buy a '03-'04 Cobra rack and MM shaft and call it a day (and another $600)

Some info about bumpsteer

Reply #17 – March 16, 2007, 11:09:24 AM

Heh, as a matter of fact I have an 03 Cobra rack, just arrived this week :). Now to determine if it's really a Cobra rack or not, any ideas? I'm sure there's a number on it, I just don't know what it's supposed to be.

Some info about bumpsteer

Reply #18 – March 16, 2007, 12:25:29 PM

http://www.corner-carvers.com/forums/showthread.php?t=25628&highlight=cobra+rack

See post #24 for the rack codes, but the entire post is chock full of good tech.

Some info about bumpsteer

Reply #19 – March 16, 2007, 01:58:31 PM

Sorry to veer off-topic, huge thanks for the link, it appears my 03 Cobra rack is not after all, it's a 99-01 "SJ" rack, I paid 85 shipped for it, I'm going to see what the seller says about it and hopefully work it out the nice way. Any input appreciated, just PM me.

Some info about bumpsteer

Reply #20 – March 16, 2007, 08:30:55 PM

Quote from: JeremyB;134797

I don't think extending the wheelbase moves the P/S rack at all. That would screw up the ackerman.

well i cant speak for all aftermarket kmembers, but mine moves the rack with the wheelbase. makes sense to me. push the control arm and spindle forward, move the rack to match.
03 cobra rack, or 00R rack would be nice. not currently in the budget, but maybe one day.

Some info about bumpsteer

Reply #21 – March 16, 2007, 11:21:52 PM

I guess that makes sense from a cheap perspective, but from a performance perspective, moving the rack forward lessens ackerman (not necessarily the end of the world), and moves the engine up an inch (bad for CG).

MM adds 3/4" WB w/o moving the rack forward.

Some info about bumpsteer

Reply #22 – March 16, 2007, 11:44:11 PM

That doesn't give you the best ackerman or engine CG (I assume the engine is moved forward too).

Some info about bumpsteer

Reply #23 – March 17, 2007, 09:48:07 AM

no, the engine is in stock location.

how exactly does moving the rack and spindle TOGETHER affect the ackerman effect, enlighten me? :hick:

[SIZE="1"]
please google "ackerman effect" and "toe out on turns" before responding[/SIZE]

Some info about bumpsteer

Reply #24 – March 17, 2007, 11:34:03 AM

Optimum Ackerman for our vehicles is with the rack moved back a bit. This is still valid when you add SN95 spindles.

I have designed and build suspensions from scratch. I know what Ackerman is.

It is mostly an intellectual point. It isn't going to noticeably affect performance on a road course. In our case (Baja SAE), maneuvering at or near the steering lock was quite important, so we added a ton of Ackerman.

Some info about bumpsteer

Reply #25 – March 17, 2007, 12:04:35 PM

ok fine, im glad you know what ackerman effect is. i still dont see your point that moving the rack with the wheelbase will "screw up the ackerman."

Some info about bumpsteer

Reply #26 – March 17, 2007, 12:16:49 PM

It won't, I don't have any clue why I wrote that.
I reserve the right to withdraw inane posts. :hick:

Where is ADAMS when I need it?

Some info about bumpsteer

Reply #27 – March 17, 2007, 09:36:56 PM

I have a book on RC cars that explains Ackerman, I should dig it out...:hick: