Hello

I have recently installed a Steeroids power steering kit on my C3 and presently running it without power assist (awaiting pump/brackets etc.). The front end have been dialled in according to the specs listed at VBP, “Advanced street” but it seems like I have a lot of “bump steer” on uneven roads. It is particularly bad when braking and hitting an uneven spot at the same time or driving slowly – almost to the point where it is dangerous due to the car rapidly shifting direction (especially when braking hard during spirited driving).

Will the “bump steer” disappear when I add power assist or is there some secret numbers for the front end alignment that will minimize the problem?

Greetings from Denmark

Regards
Karsten Horn

 

Nice looking car, Karsten!!

I notice some bump steer after I installed Steeroids last summer. I assume that's because of installer error. The instructions (which I didn't think were very good) say:

"Spacers have been provided to adjust bumpsteer. Stock ride height setting has been preassembled. To adjust, match the tie rod angle to parallel the lower control arm when vehicle is on the ground."

The instructions make it sound so simple, but it's not. First, what is "stock ride height" and how do I know if my car is at stock ride height? I could probably look in my GM Shop Manual for stock ride height measurements and measure ride height of my car, but...

Matching the tie rod angle to parallel the lower control arm was a rough guess at best for me because the shape of the A-arm is irregular. I am planning to adjust the tie rod angle this spring. I need to find the pivot points of the A-arm, get a line between them, and actually measure the angle of the tie rod to this line. I am assuming I will need to change the spacers.

Does SpeedDirect watch this forum? I will send them the link to this thread and see if they will share some tips with all of us.

 

This is how I do it. First you need to measure a distance between one tire and the other, at the front as high up as possible or about the middle of the tire.
It sure helps to have a drive on lift for this.
Anyway I measure from one tread, any tread on one side to a spot on the other tire, any spot but remember which spot you measured. You can use masking tape and put a line.
I then jack the car up 3 inches and again take this measurement. You will find this measurement less then the previous measurement.
This is toe in and represents only one tire, remember the back kicks out an equal amount.
I then pull down on one of the outer tie rods joints. I know you can't do that with a tapered tie rod installed in the steering arm.
But if you pull it out of it's taper you will see as you lower the outer tie rod that tire straightens out, the measurements gets larger, going back to the original reading. The amount you pull it down, out of the taper is the amount you need to lower that joint to get zero bump.
You would be able to correct the reading by 1/2 to get rid of all bump since you are only working with one tire.
I remove the strearing arm, I know this is a pain but not too difficult. I then drill and tap the tapered hole for a 16mm bolt. I then replace the outer tie rod with a 5/8th rod end.
Now you can add washers between the rod end and the steering arm and just thread a 16mm bolt through the rod end, washers and into the steering arm to remove all traces of bump.
You do NOT need a specail bump gage to get close, You can get down into the 1/8th range, even the 1/16 the range without dial indicators. You can read 1/16th on a tape measure.
Keep adding washers until you get the toe in back to normal with the car 3 inches up.
Going down in difficult and requires longer tie rods to correct.
I have a special hook that pulls a car down and collapses the suspension for doing the compression side but again you need an assortment of tie rod sleeves and drag links.
You can get very close with just a tape measure but again a drive on ramp really helps.
Good luck.
I used the dial gages in the end and settled for .007 toe change over 7 inches of travel. But I was very annal about this.

 

Thanks for the good replies, especially the quoted message is very interesting and I like the method. However, when looking under my car there is no way that I can shim the outer tie rod ends in order to make it even with the lower A arm. My car is lowered for sure but not that much I think. Maybe there should have been an adjustment feature at the inner end of the tie rod, on the big iron plate that goes on the rack and pinion. The inner end link is placed in the upper left corner and plenty of room for adjustment down further if designed differently.

When I did the alignment of the front, I did it with the wheels in the air - Was that wrong??


Yet again, big thumbs up for the good replies.

Regards
Karsten Horn

 

Definitely Wrong. You need the wheels on the ground with the car rolled ahead. You can't just set it on the ground and set toe. You need the car's suspension settled by rolling the car ahead and then measure the toe.
You have alot of TOE OUT if you set it to zero in the air and then set it down. Toe out will make it dart bad.
Reset the toe.

 

The slope of the tie rod affects the toe in or out on rise. Drop the outer tie rod or raise the inner mounting location does the same thing.
When the car rises the tie rod gets longer so by changing the slope you are preventing this change in length.
If you fix the toe in under rise you might be increasing the toe out under compression.
To fix both rise and compression the length of the tie rod sleeve does this.
On a stock vet you need to drop the outer tie rod and inch or two and lengthen the tie rod sleeves about 3 inches which also means a shorter drag link.

 

I got a reply from SpeedDirect today to my message I sent last night. They forwarded my message to the person in charge of monitoring the CF. He had already seen it and is planning to reply.

There have been some other threads about Steeroids with some questions about the strength of the gussets, rod plate, road feel, etc. I am hoping they will have a comment or two about those topics too. They have always been great to work with, so I am looking forward to their response to this question about bump steer. Stay tuned!!

 

im still waiting to get a replacement rack sent as my 1 st rack was clocked wrong and almost broke the line..also if you install a shim kit gives more solid feel. ihavent driven my vette for almost 2 weeks sitting on a lift waiting for the replacement..maybe they will read this and send it[/IMG]

 

Maybe they will say when they fixed the design problem you had. I installed mine a year ago. They obviously fixed the problem of the bolt rubbing on the line between when you bought yours and I bought mine. That would help narrow down the Steeroids customers who should check their system. As this pic shows, mine has plenty of clearance.



We're all ears.

 

Then I have made a big mistake for sure, I will try to align it again with the wheels on the ground and the suspension fully set. However, that does not solve the other problem as I cannot see the possibility to get the tie rods parallel to the A arms without doing some heavy modification to the Steeroids kit.

Thanks for all the help

Regards
Karsten Horn

 

Hang in there, Karsten. I'm going to wait to see what SpeedDirect has to say. I think they've thought about bump steer already.

 

Norval has already covered the topic pretty well in this thread but let me make a few comments and also address some of the other concerns as well. First off, as a general rule for bump steer the Corvette front end needs the outer tiered as low to the ground as possible with the adjustments available (or the inner can move higher but the outer is easier to adjust without modifications). With the Steeroids kit the tiered end has a spacer(s) to change the angle of the tiered. Additionally the tiered end can be lowered by adding more positive caster to the front end.

As Norval has pointed out Karsten needs to set the toe with the weight of the car on the suspension. A lot of toe out will cause the car to be very unstable. Zero toe will make it 'responsive' to steering inputs (read that as neutral to slightly unstable) which is fine for street driving if you are used to it and prefer it like that. Zero toe is my personal preference but it is not for everyone. If you want your steering more stable then dial in some toe in. 1/32" to 1/16" will make things less 'nervous' feeling.

I think there is some confusion between bump steer and steering responsiveness. Clearly Karsten has overly responsive (unstable) steering due to incorrect toe settings. MN80Vette may have too much responsiveness to his liking that can probably be solved with more positive caster. What are your current alignment settings, MN80Vette? Bump steer issues can be isolated by analyzing what the car is doing while driving. If, while driving, you hit a long bump and the nose of the car changes direction slightly at the peak of the bump then returns to where it was pointing as the suspension moves back to its original position all without you moving the steering wheel then you have bump steer. On the other hand if you hit a rut or a bump and the steering wheel jerks from your hand or the nose darts to one side and doesn't really want to return to center without a steering wheel input then you have a stability problem that can probably be corrected with toe and caster changes. Adding more positive caster with make the steering more stable feeling and will give you more ‘feel’ by way of increased steering effort.

 

@ Speedirect
Only problem is that the original a-arms are not able to give you that extra positive caster, thank god you just resently made the new aluminum upper control arms that are capable of giving more positive caster

you guys should really give a discount when ordering a set of those puppes for anyone that purchased your steeroids system allready

But thank you for replying to this thread, good to see customer support are well at Speedirect

 

When I wanted more positive caster I slotted the original cross shafts 1/4 inch towards the front. This allowed about 5 degrees positive caster without shims or changing the existing camber.
5 minutes on the mill will easily slot the cross shafts.

 

This is a homemade cross shaft with both added positive camber plus positive caster. You can buy offset cross shafts. I prefer to make my own to my own specs.

 

Couldn't you make cross shafts to lower the pivot point also? I think that it would be easier than lengthening the spindles. I'll volunteer to test the prototype

I'll post a pic I drew when I get home tonight.

 

A big for at very good reply, my issue right now is clearly too much toe out combined with the tie rod being out of angle. My only issue now is to get that outer tie rod end further down; it is shimmed as much as possible and still needs to be moved another 8 mm down. I can't do that with the outer tie rod end links supplied with the Steeroids kit.

Another question, is it normal to have a little play in the rack and pinion? I have about 1 cm of play on the steering wheel and it is very clear that the play lies within the pinion itself and not in the linkage. Not a big issue when there is load on the front end but clear to see when car is up in the air.

Apart from the minor issues, this upgrade made a world of change to the original behaviour of that old Vette, it is now much more fun to drive and I'm not even sure that I will apply power assist as I simply love the new road feeling. I'm still thinking about an electrical power steering pump controlled by a Hall sensor. This way I could have assist when needed and the direct feel when doing "spirited" driving on the local back roads.

I will look into more caster as well but would the added caster keep the tight road feel as it is now, with maxed out caster on the stock parts?


Thanks for superb support.

Regards
Karsten Horn

 

Thank you for the thorough explanation. Most of it makes sense. I'll have to look at my car to understand the caster part because I think that's my main problem. According to your explanation highlighted above, I do have bump steer for several reasons.

The first thing I need to do is put on the biggest spacer on the tiered end of the rods. (I hope I can find them.) I quickly eyed the angle of the rod and never checked it again. I think I have the smallest spacer on now.

The other thing is to add more caster. I installed a VBP front mono spring conversion at the same time and had the front-end aligned to VBP "Daily Street" figures: 1/32" toe, 0 deg. camber, 2-3/4 deg pos caster. I think I will leave the toe the way it is and fix the tiered spacer and caster problems first.

I have VBP tubular upper control arms on too. VBP says, "Relocated ball joint mounts are designed to allow up to 5 deg positive caster and greater camber adjustment range for better handling and road tracking."

How do I change caster? How do I measure caster? Or is this something I should just have an alignment shop do once I change spacers?

 

Never mind. I found the answers to my questions. Caster (and camber) are changed by adding or removing shims from the A-arm mounts. And no, you can't just take some length measurements to determine castor angle. I'll take my car to an alignment shop that won't insist on factor alignment specs, but first I need to replace the spacer I have on the tiered end with the wider spacer.

 

Norval i envy your fabrication skill, unfortuantly i do not have the machinery for making components of that caliper.
What excatly does the added camber setting benefit with