Hello All, I've searched and found some information on similiar setups, but nothing setup exactly like my car, so I need some help with this. I have a 51 shoebox with flipped spindles, spring drop spacers and cavalier rack and pinion steering. I just recently went with 20" wheels over the 15's and now have greatly exagerated existing bump steer. As it sits there is a slight upward angle on the tierods in relation to the lower A arms. I wanted to see if anyone has this setup and can offer advice on reducing bump steer. My thinking is that I can remove the spring drop spacers and improve it some, but I really like the ride. I can also bend the steering arms down a little more, but that scares me a bit. It seems to me that there is also alot of body roll when hitting bumps that may be compounding the problem. I am not sure, but when the road is unlevel it is like riding in a bowl of jello! Any help is very much appreciated.
put the 15's back on. might not cure your bump steer, but at least you won't look goofy while driving.
My bet would be the flipped spindles and the rack and pinion set up. If a rack is not level in the frame and or mounted too far forward or back it will cause bump steer.
Hehe....figured I'd catch some flack on that. I have moons in the garage so go easy. I have had 10 to 1 compliments on the 20's over the 15's....guess it is just a taste thing. BTW, what is a donk As to the mounting point, it is slightly rearward of the steering arms. However, it is definately level and mounted solid. Here are some pictures as well for those who want to help....they are small, but I think you can see everything. Another note is that I really payed attention to the way it handled driving home. I think the problem is actually three part; slight bump steer, extremely sensitive steering making for easy over correction, and body roll back and forth after the first two.
the tierods must have same legth as the projected a-arms so you not get bumpsteer this my adapter in the on the rack and pinion steering i have shorten the tierods I hope i wright understandeble english is not my own language /Stefan
20's vs 15's is not a "taste" thing - this is a traditional site. donk is equal to dork. listen to what Stefan T is telling you-if you need more of his help just ask. you can also search online at Longacre Racing Online-Tech Article: Front End/Chassis Set up -Bump Steer
I understand perfect and thank you for the help. This makes perfect sense. I guess can also build the leveling into an adapter to correct tie rod angle.
What is that rack and arms out of? Yes by princible your steering arms should be equal length to your lower arms and parrallel with them but should the backward angle of the lower arms be taken into consideration? ie. imagine your lower arm as a straight line between outer bushing and the center of the inner mouting bar. positioning inner tie rod ends at a width relative to that length would perhaps be optimal? or would the arms end up too short causing bump steer? regardless of position, this overall length or a fraction shorter is pretty much optimal for your tie rods. Why a fraction shorter? because when your suspension travels up, the upper (shorter) arm pulls the camber in efectively shortening the distance between the wheel and the chassis. If your tie rod is the wrong length it can and will turn thhe wheel slightly in or out (bump steer). Also consider the racks position fore/aft. It will have an effect on the ackermans principle, ie how much additional toe out you get when the wheel is turned. the further back the more toe out. the majority of this will be determined by the outer tie rods width relative to the KPI. If im loosing anyone, unfortunatly Googleing any of this may not help, there are not enough websites with the hard facts and diagrams, tho they are out there.
How/when was the car aligned ? How much Toe ? In or Out ? How long are the Tie Rods ? You might find your Cavalier rack isn't the best choice.
ChopShop, Thank you and I will have to do some measuring and discect all of this so I can make a more informed reply. I am thinking with the angle of the lower control arm bushings it would be best to have the tierods slightly shorter than the rearward bushing. However, mine are longer. Likely leading to toe in? It is actually very evident when jacking up the car that when the suspension travels up toe in becomes severe. I have not tryed to compress it and confirm the opposite, but someone jumping up and down on the bumper might be enough to see one way or the other if holding a tape on the tires....might try that. However, all of this above looks to me like it could also be an issue even with stock steering components and a lowered front end? Unkl Ian, The car was aligned with the 15" wheels and tires, but not with the 20"s(I know you guys are cringing). I have not measured the toe and I dont know what it is set at. I have not measured the tie rods, but they are longer than the lower control arms by a good measure...maybe 3". I actually think an adapter like Stephan made to correct positioning and angles is best if I can come up with what is actually right for this front end. The funky angle on the lowe arms and the huge difference in lenght between lower and upper is making it hard for me to figure based on what I find on the net. Also, I am not too crazy about welded steering parts, but I have a buddy that can tig weld it so that would make me feel better. Thanks, and anything else is appreciated.
Stephans pivot points make sence when your going straight but what about when taking a turn at speeds. The pivot points certainly wouldn't line up. So my question is...on a stock cavilier rack the bolts for the inners are only about 2 inches apart, near centre. The pivot points of the rack and lower control arms are miles apart. Handles perfect on a cavalier. Seems to me it's the very long rods with a minimal arch travel that makes it work. I'm in the process of racking my 50 and all this info is valuable but i beg to differ on the inners being shortened as long as the rack position, up down forward rearward is the key. But i have to try this. I have thought about flipping the spindles as well but seems to me the 'g' forces would be carried by the upper control arms which are tiny compared to the lowers. I suppose lowered spindles do the same and might not be a concern since may are being used without an issue, as far as i know. I might be out to lunch on my way of thinking so enlightin me if need be.
I am kindof thinking what you are on the long arc issue the more I look at this. I am going to remove the spring drop spacers first and see what happens, but just have not gotten around to it. This will level out the tie rods with the lower arms. Like I also mentioned I think that body roll also has something to do with my issue. It does not have sway bars so the roll adds to the bump steer causing a real wonky feeling. I can also tell you the steering is very fast with this setup which can also give little issue since a slight move causes darting in that direction...light right now. So, I think your going to be fine once it is setup right. Mine just has some work yet.
I think the fact you have no sway bars is a major issue making turns. Even if your suspention was correct it would still feel like crap. The darting i think i'd look at a toe situation. If it darts going strait, try a different toe setting since there isn't alot going on where your going staight especialy if you try it on a known smooth road where the suspention is not moving that much. That may help to narrow things down. I don't think the lowered spring plates has anything to do with things. I'm going to look closley at the stock position of the caviler in regards to height and forward rearward position of the rack to the steering arms. Suspentions travel downwards more than up because the wheels follow the road and when hitting a bump the car lifts abit on rebound with the suspention. Suspetion travels more obviousy.
From reading older threads on here, the flipped spindles always seemed to give the bump steer complaint.
Thank you for the input. I am curious if you have a nice trick for accurately measuring toe in a home garage. I figure I can use a reference point on the tires, but that seems less than accurate. Not too keen on paying the tire shop to do trial and error. As for the lowering plates, removing them would make the tierod track level with the control arms. As it is now it tracks up which on suspension extension causes toe in and on compression toe out. If it is level it should help this fairly dramatically. As to the note about swapped spindles, I think it has to do with the steering arm location. They are located further in and away from the spindle centerline on mine which can also increase bump steer. The only option to fix it would be heating them and bending them out as well as lengthening the tierods. I'd like to think of that as a later resort.
Thats about as basic as it gets for front suspension design, ie. "mkII mustang" or any race car. First point to make is; look at the angles front on. On a lowered shoebox your bottom arm will be close to level. same goes for your upper arm pointing up a bit. on all the road/track cars this about the standard. your steering arm should be angled as the diagram describes. Two question marks remains on a shoebox about the rearward angled arms. And the built-in ackermans angle on the steering arm. First, the rearward angle, in my opinion point "C" would be the center of the bottom arm shaft (in terms of width from the cars centerline). Thats all. The stock steering arm setup is rearward of paralell. as i mentioned before this would give additional toe out in a turn, however the idler and pitman arms push everything forward as you turn left to right. This lengthens the setup causing toe in. Its clearly Fords atempt to compromise, the overall effects will cancel each other out. (stock steering) So what does all this mean? 1. The length of your steering arm needs to be from point "C" as above, to point Z which on the ford is the king-pin (not outer ball joint) 2. ackermans (turning toe out) is built into your steering arm/kingpin setup, so mount your rack and arms parallel from a birds eye view (straight across). 3. Height wise, simply bolt up your outer ball joints and refer to above diagram. 4. As for the spacing between the inner joints, firstly allign both wheels perfectly parallel. Then how I would build Stefans bracket would be determined by where the inner rod ends ended up after following 1,2 and 3. After putting plenty of thought into it I think Stefans setup looks pretty damn good If i dont "clip" my shoebox this is what ill do.
If half the shoebox guys put 20's on their car, they wouyld suddenly realise how bad their geometry was and blame it on the 20's there is no reason the flipped spindels wont work, screw the nay sayers. you need to buy drop steering arms, or heat bend yours. follow the tried and trued geometry setup on your rack and run a sway-bar.
If half the shoebox guys put 20's on their car, they wouyld suddenly realise how bad their geometry was and blame it on the 20's there is no reason the flipped spindels wont work, screw the nay sayers. you need to buy drop steering arms, or heat bend yours. follow the tried and trued geometry setup on your rack and run a sway-bar.
Yep, you are right. When the suspension is right it makes them handle great. However, it also exposes ALL the problems if they exist. I had similiar issues with another car and 18's, but two others worked perfect. The up side is that when sorted out I will have a shoebox that will handle like a sports car....maybe My arms are bent down, but I think they need a little more...it just scares me. Thanks for the above discription. I am gonna digest it a little while.
I suppose...some are just old traditional hotrod guys that are just more open minded I guess Don't get me wrong, I love traditional cars with wide whites...they are cool as hell. But, you know everyone talks about SBC's and such as "belly button". If it is belly button to use an SBC in a hotrod, what does that make wide whites on a shoebox? I like my cars to be different....each to his own.
Hey just some info Im planning on some kind of steering setup for my shoebox what is bumper streer cause most of this went over my head
Bump steer is when the toe setting change due to suspension compression or extension(moving up or down). So, if you are driving and hit a bump the direction the front tires are pointing changes....this is bad and causes a substantial pucker factor.
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