ok suspension gurus. has anybody done some checking to see how low you can lower a 5th gen civic before running into bump steer problems? i already run the car with a ride height of 5" measured to the jack tabs on the rocker panels with 205/50 falkens and haven't "felt" any problems, but that may have been masked by my running 1/2 inch total toe out. is there any resources out there for the bump steer angles on this chassis??

nate-who will test in the spring, but since the weather sucks and work calls and ...............ok, so i'm lazy.

 

You can learn a lot on jackstands, if you are willing to play around a little. Check your chassis ride height and put the car up in the air. Take off the coilovers and disconnect the antiroll bar, and put it back down on blocks of wood so that the chassis is back at the ride height. You can now position the hubs at the wheel centerline height and see where things are...

Check the steering tie rod to see what angle it is making between the rack and the steering arms. The more it is off of horizontal, the worse your roll/bump steer issues will become. You can also move the suspension up and down and I will bet that a LOT people out there will be a little disappointed to find out how bound up things are - how much resistance there is to the normal movement of the suspension. This should not be the case, ideally, in that motion should be controlled by the spring (force) and shock (damping).

If you really want to get clever, you can make plates to bolt to the spindle, so you can actually move the suspension through its travel and measure the change in toe. An elegant answer that I saw once used rectangular aluminum plates that bolted to the wheel hub and duplicated the raduis of the front tire downward, forward and rearward from the hub centerline - but NOT upward. This allowed them to hang naturally just off of the floor when the car was on blocks as described. It was easy to measure the distance between the front and rear edges of these plates at any point in the suspension's range of motion, at any postition of bump - set by putting a blocks of known thickness under one or both plates.

Understand that, in this case, the rules allowed spacers to change the angle of the tie rod, making it worth all of the trouble...

Kirk

 

work! ick! that is probably what i'll be doing come springtime. i was just wondering if anybody else had done this yet. ya know, corraborating evidence or whatever.

(bump)

nate

 

cant you buy a bump steer gauge? I know formula car guys use it to setup their cars.

 

i suppose i could, but it would still wait towards spring time before i have the time/ambition/weather so i can actually test it. i guess everyone is a spring rate specialist, but the rest of suspension setup........

nate

 

OK - the SHORT answer is "go no lower than where the tie rods are horizontal", if bump- or roll-steer is a primary concern.

K

 

i guess i'm just disappointed that i didn't get a page long post with all sorts of formulae and graphs and such. i'll wait till spring to measure for myself, then i'll have to make just such a post.

thanks for your contribution.

nate

 

Have a look at this page, point number 6.

http://www.woodwardsteering.com/rpi.htm

 

:bookmark:

excellent link. definitely helps in the theory of bump steer and the section on ackerman was excellent too. thanks!

nate

 

back from the dead...

Has anyone moved the mounting of the tie rod end to the bottom of the steering knouckle mounting point, instead of the top to correct the upward angle of the tie rod towards the wheels?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jg &raquo;</TD></TR><TR><TD CLASS="quote">back from the dead...

Has anyone moved the mounting of the tie rod end to the bottom of the steering knouckle mounting point, instead of the top to correct the upward angle of the tie rod towards the wheels? </TD></TR></TABLE>

I thought about that as well, but that hole in the knuckle is tapered...I thought about drilling it out & making a metal bushing tapered the other way, but I am afraid the bushing might wear, or deform, etc. (sloppy steering) - besides, what happens when your suspension tries to move upwards? I'm not sure if that would cause binding or not - I haven't had enough time to spend under the car, and sometimes in practice things are different.

 

our fsae team puts a flat chunk of steel on the hub to simulate the wheel. then we have another peice of metal held off the floor with a bracket sitting next to the "wheel". 2 dial indicators, located a know distance apart (same height, one in front of axle line, other behind it). calibrate the indicators, then move the suspension through its travel. do some trig with the readings you get from the dial indicators, and you have your bump steer.

 

anyone else done the move to the lower side of the knuckle?

 

If you're concerned about it loosening up (a valid concern) you could machine a peice that still utilizes the taper on top and bolts tight on bottom. This of course would only be useful if you have enough room to allow a nut underneath.