LegendsRacer - Legends & Bandolero Racing Forum

LEGENDS => Setup and Handling => Topic started by: racer0x on March 02, 2014, 08:25:13 pm

Title: bumpsteer
Post by: racer0x on March 02, 2014, 08:25:13 pm

I'm workin on getting rid of my bumpsteer .I have finally gotten it to bump out But it still bumpe out an eighth of qn inch in an inch of travel....any idias???

Title: Re: bumpsteer
Post by: justfreaky on March 02, 2014, 08:54:09 pm

More info...
Dirt or pavement. Know you are in Mass.
How are you measuring this? (I assume in the shop and using a jack to measure travel, etc...)
What is the problem you are having? (Tight or losse in or out, etc...)
They make spacers to help adjust the rack and rod ends.

Steve

Title: Re: bumpsteer
Post by: racer0x on March 02, 2014, 10:30:01 pm

It is  asphalt  and I am useing a longacre bumpsteer guage.as far as what  its doing we haven't turned a lap yet. But I'm pretty sure its not good when it bumps out an eighth of an inch in an inch of travel.

Title: Re: bumpsteer
Post by: justfreaky on March 02, 2014, 11:00:23 pm

I figured pavement.
1/8th isn't too bad.
Bump steer, for short track cars, should be zero on the left front (or as close as you can get) and .040 -.0625 outward per inch of spindle travel on the right front.
The piliminary design factor to help prevent bump steer is to have the tie rods parallel to the lower control arms, and same length as the lower arms. This allows the lower control arm and tie rod to swing together in the same arc.
(Straight out of dang near any chassis book)
I've got a few pages on how to set bump steer.

Steve

Title: Re: bumpsteer
Post by: racer0x on March 03, 2014, 12:50:00 pm

That's where I started out was level with the lower arms but that way it  bumped in twice as much! I think most of it has to do with tie rods that are too short.

Title: Re: bumpsteer
Post by: justfreaky on March 03, 2014, 01:01:47 pm

Do you have a copy of Dwarf Car Technology?
On page 41-43, it shows how to make a simple graph and explains what the likely causes are.

Steve

Title: Re: bumpsteer
Post by: s10custom on March 03, 2014, 06:05:56 pm

Could you share those pages??  ::)

Robert

Title: Re: bumpsteer
Post by: justfreaky on March 03, 2014, 08:18:18 pm

Robert,

I'll see if I can scan the pages and post.
Basically, the charts are just some graph paper split in half (toe in/toe out) and measurements at 1/4" increments in both bump and rebound.

Steve

Title: Re: bumpsteer
Post by: s10custom on March 04, 2014, 11:29:13 am

I would appreciate that. You mentioned adjusting the rack, but I thought the only thing you could do there was to bolt it into it's mount, that it ahd to sit flat in the mount.

Robert

Title: Re: bumpsteer
Post by: VMS Motorsports on March 04, 2014, 11:37:15 am

I think he was referring to the rack end rod end spacers, not adjusting the rack itself