Unisteer/bump steer???

[awr68]

So I'm interested in this Rack and Pinion Kit (http://www.unisteer.com/product.php?productid=16218&cat=250&page=1) Unisteer came out with for the first gen camaros and have a question. I have a '68 Camaro with the DSE coil over kit and UCAs and have also lowered the car 2-3" as well, will the fact that I lowered the car and changed the geometry of the UCA mounts contribute to bump steer?

Unisteer says "The Rack & Pinion that comes with this kit, is a highly modified GM rack & pinion: it has been internally shortened, reducing the width of the ball centers. By narrowing these pivot points, the rack & pinion pivots in the same position as the upper and lower control arms of stock Camaro, replicating the dimensions of the stock steering and resulting in precision rack & pinion steering with no bump steer!"

I hate to buy this kit and have bump steer when I know if I buy the new DSE steering gear I will suposidly have R/P feel and no bump steer...what to do?? I really would like a power rack...just don't want to deal with bump steer issues.

Thanks for all input....

[zuess4u]

So I'm interested in this Rack and Pinion Kit (http://www.unisteer.com/product.php?productid=16218&cat=250&page=1) Unisteer came out with for the first gen camaros and have a question. I have a '68 Camaro with the DSE coil over kit and UCAs and have also lowered the car 2-3" as well, will the fact that I lowered the car and changed the geometry of the UCA mounts contribute to bump steer?

Unisteer says "The Rack & Pinion that comes with this kit, is a highly modified GM rack & pinion: it has been internally shortened, reducing the width of the ball centers. By narrowing these pivot points, the rack & pinion pivots in the same position as the upper and lower control arms of stock Camaro, replicating the dimensions of the stock steering and resulting in precision rack & pinion steering with no bump steer!"

I hate to buy this kit and have bump steer when I know if I buy the new DSE steering gear I will suposidly have R/P feel and no bump steer...what to do?? I really would like a power rack...just don't want to deal with bump steer issues.

Thanks for all input....

I did address this question in the GP fourms, I called Dave Barkte today, but he did not get back to me. You too can call and address the issue to them, I doubt there is a big problem. Installed this system has no bump steer, (stock ride height) if lowered the worst case I can see, is that you add a spacer under the hiem joint that connects to the steering arm. This is just my thought, Unisteer may have a better solution to this, and Im sure they have already addressed this, due to the fact they created this R&P just for guys like us. Im sure they new there would be lowered 1st gens buying their set up. But I would call, as well will I, and find out, because Im in the same boat. Thanks Bob AZ.

[awr68]

Thanks Bob, I did email them this morning but have yet to get an answer...let us know what you hear!! Thanks for the GP too!!

[David Pozzi]

If someone trys this kit, please post back here with the results, good or bad.
Thanks, David

[Salt Racer]

...changed the geometry of the UCA mounts contribute to bump steer?...

Technically, yes. It has effects. But knowing that the outer tie rods need to be lowered even with stock pickup points, G-mod or DSE relocation would help reduce bumpsteer.


...By narrowing these pivot points, the rack & pinion pivots in the same position as the upper and lower control arms of stock Camaro, replicating the dimensions of the stock steering...

:confused: ?? Does this mean that R&P width (center of inner socket to center of inner socket) is the same as pivot center width of inner tie rods on OE drag link? How about the height of socket centerline?

[zuess4u]

If someone trys this kit, please post back here with the results, good or bad.
Thanks, David

Dave, I have been speaking with Dave Batke at unisteer, we will be using their rack on our project, but wont be driving it for a while, but I will post up picks and any measurments you may want to see.

[zuess4u]

Technically, yes. It has effects. But knowing that the outer tie rods need to be lowered even with stock pickup points, G-mod or DSE relocation would help reduce bumpsteer.



:confused: ?? Does this mean that R&P width (center of inner socket to center of inner socket) is the same as pivot center width of inner tie rods on OE drag link? How about the height of socket centerline?

To answer your question on the OE drag link, I would say yes in some cases, but not with the 1st gen suspension. There is no rack made with the same requirments as the first gen. Unisteer/Maval has included an additional steering arm and has re-manufactured a GM rack to solve the bump steer problem and gives the car about 3 more degrees of turning radius.

[zuess4u]

Thanks Bob, I did email them this morning but have yet to get an answer...let us know what you hear!! Thanks for the GP too!!

I spoke with Dave today, and Im glad you e-mailed there site as well. He says if the car is lowered 2'' you may be able to read a bump steer gauge, and only then be able to tell if you have any or not.

Most of us on this site will never know the feeling, most factory cars on the road come standard with bump steer, its not even an option, you get it for free.

Dave says, however if you measure, and think its significant enough, then he would suggest buying Bears bump steer kit.

But he feels strongly even with 2'' of drop you wont see any problems. I tend to agree, but then again, I really want R&P.

[awr68]

Got this reply today to my email asking about b/s and the car being lowered a couple inches as well as the ratio:

67-68 Rack and Pinion

"Hi - in responce to your questions - it will work with a 2" drop - road feel is very good - with a lock to lock of 2.5 turns about the same as a vette - no bump steer - thanks for your interest"
regards " Denny "

Anyone know how the 2.5 turns lock to lock compares to a DSE 12.7:1 box? This seems like a very well engineered kit and a much better price (especially with the GP)that the others out there...

[Salt Racer]

To answer your question on the OE drag link, I would say yes in some cases, but not with the 1st gen suspension. There is no rack made with the same requirments as the first gen. Unisteer/Maval has included an additional steering arm and has re-manufactured a GM rack to solve the bump steer problem and gives the car about 3 more degrees of turning radius.

So in another words, it's physically impossible to narrow the R&P to the same width as OE Camaro draglink and they compensate the length by reducing Ackermann angle. That brings a question of how much Ackermann they sacrificed.

I think we need bumpsteer curve of a Camaro w/ G-mod or DSE mod. I know there are many combination of pitman, idler, steering arms, etc. But knowing bumpsteer curve with OE steering components will let you evaluate whether OE tie rods are too long or too short relative to the rest of suspension.

Aside from IC location, dropping UCA mount by an inch will change required length of tie rods (shorter FVSA). So if they managed to get very small bumpsteer curve with OE pickup location, the tie rods are likely to be too long for G-mod'ed or DSE'd suspension. However the effect of this is much less sensitive than the height change of tie rod center. For example, my car currently has toe-out 1/16" bumpsteer over 27" span at both 2.25" bump and rebound travel. To get rid of this, I need to lengthen tie rods by whopping 2". Changing the height of tie rods will merely shift the bumpsteer curve up or down, and will never get rid of bumpsteer unless I make the tie rods longer.

Note: I don't have a Camaro. I'm just here for a tech talk.



Got this reply today to my email asking about b/s and the car being lowered a couple inches as well as the ratio:

67-68 Rack and Pinion

"Hi - in responce to your questions - it will work with a 2" drop - road feel is very good - with a lock to lock of 2.5 turns about the same as a vette - no bump steer - thanks for your interest"
regards " Denny "

Anyone know how the 2.5 turns lock to lock compares to a DSE 12.7:1 box? This seems like a very well engineered kit and a much better price (especially with the GP)that the others out there...

Is this lock-to-lock number limited by internal stops of R&P or by stops on steering arms? It's kinda vague answer.

If they don't know the exact ratio of R&P, it's better to ask displacement of Rack shaft per one turn of pinion, like 2" of rack travel per one pinion rev. This will let you do direct comparison to the box.

With 5" long pitman arm, 12.7:1 box will displace drag link by roughly 2.37" (at least in the first revolution).

I don't believe when someone says "no bumpsteer". There's no such thing as no bumpsteer - answers like 0.030" bumpsteer at 2" travel are more believable. That said, I'd say it'll be a good deal if the R&P kit cuts down the bumpsteer curve below 0.050" or so at full bump.


My comments may sound negative, but I just want you guys to really evaluate the product before you plunk down big money. I'm not skeptical about Unisteer in particular, but MANY aftermarket companies are known to use customers as guinea pigs. It's just a reality of aftermarket industry.

[zuess4u]

So in another words, it's physically impossible to narrow the R&P to the same width as OE Camaro draglink and they compensate the length by reducing Ackermann angle. That brings a question of how much Ackermann they sacrificed.

I think we need bumpsteer curve of a Camaro w/ G-mod or DSE mod. I know there are many combination of pitman, idler, steering arms, etc. But knowing bumpsteer curve with OE steering components will let you evaluate whether OE tie rods are too long or too short relative to the rest of suspension.

Aside from IC location, dropping UCA mount by an inch will change required length of tie rods (shorter FVSA). So if they managed to get very small bumpsteer curve with OE pickup location, the tie rods are likely to be too long for G-mod'ed or DSE'd suspension. However the effect of this is much less sensitive than the height change of tie rod center. For example, my car currently has toe-out 1/16" bumpsteer over 27" span at both 2.25" bump and rebound travel. To get rid of this, I need to lengthen tie rods by whopping 2". Changing the height of tie rods will merely shift the bumpsteer curve up or down, and will never get rid of bumpsteer unless I make the tie rods longer.

Note: I don't have a Camaro. I'm just here for a tech talk.




Is this lock-to-lock number limited by internal stops of R&P or by stops on steering arms? It's kinda vague answer.

If they don't know the exact ratio of R&P, it's better to ask displacement of Rack shaft per one turn of pinion, like 2" of rack travel per one pinion rev. This will let you do direct comparison to the box.

With 5" long pitman arm, 12.7:1 box will displace drag link by roughly 2.37" (at least in the first revolution).

I don't believe when someone says "no bumpsteer". There's no such thing as no bumpsteer - answers like 0.030" bumpsteer at 2" travel are more believable. That said, I'd say it'll be a good deal if the R&P kit cuts down the bumpsteer curve below 0.050" or so at full bump.


My comments may sound negative, but I just want you guys to really evaluate the product before you plunk down big money. I'm not skeptical about Unisteer in particular, but MANY aftermarket companies are known to use customers as guinea pigs. It's just a reality of aftermarket industry.

Good looking out for us. Your comments are not negative at all. I like the fact you have exsposed the bump steer. And if someone tells you theres not any B/S, it may be due to the fact that they dont want to explain the entire subject.
I may address some of these questions to Dave, but not all. Reason being is I have addressed most of them, and others Im not concerned with due to the fact Im not getting paid to race, nor is it my job.

So, any and every subject or area of building a car can be exstensivley evaluated and discussed, and in some cases its applicatable, and its always appreciated that someone helps with input.

But everyone has a different expectation for there car. And we exspect our car will handle great. Will it out corner a sanctioned GP car? No, but it will look good and handle above the average street car.

And if we dont like the R&P, I will let everyone know.

After speaking with Dave Batke over the last few months, we are pretty sure we will enjoy this product.

[Marcus SC&C]

Just a few more thoughts on bumpsteer. Moving the UCA inner pickups (ala G mod etc.) does change the bump curve but the changes in this case are rather small in the grand scheme of things. You can get about as much change in the bump (steer) curve by changing the caster 3 or 4 degrees (which changes the height of the steering arms and outter tie rod ends). When I`m doing (or redoing) steering I take it for granted that there`s going to be some bumpsteer but I strive to make it small enough that it isn`t noticable. Katz is exactly right (as usual) that you can never dial bumpsteer out until the lengths and heights of the steering points are both perfect. However that takes a HUGE amount of work (and costs customers more money than almost any of them are willing to spend).
I`ve boiled it down to this, the steering arm and spindle swing in an arc (viewed from the front or rear), the tie rod ends also swing in an arc. Ideally the arcs would look like they were drawn with a compass and would overlap exactly but in our world the curves are eliptical and usually way out of sync. There`s most of yer bumpsteer. What I try to do it match the arcs so that the apex of each overlaps at ride height. That way you get very little deviation for the first few inches of bump and droop,where you car is 90% of the time. Even at extreme travel the deviation will still be much less that when the arcs were totally out of sync. You can generally get it good enough that the dial indicator on the bumpsteer gauge just quivers a bit for half of the total travel.unless it`s something with plain god awful steering like a `46 Plymouth. As Katz basically said moving the arcs is most easily done with vertical changes to the tie rod ends,center link etc.
Once you`re at this point I personally don`t think it`s worth going through all the work to fab a new R&P or centerlink and tie rods just to improve the bump curve toward the extremes of travel unless we also correct the poor scrub radius on our older cars which induces bumpsteer-ish effects also. In other words if Dave did his homework and spent some quality time with a bumpsteer gauge their R&P should be able to achieve pretty nice results G mod or no and even if the inner tie rod ends are off slightly inboard/outboard.
Of course if you were building a car from scratch,forget everything I just said and make it perfect because you`ve got no excuse not to. :) I`ll shut up now. ;) Marcus SC&C

[zuess4u]

Just a few more thoughts on bumpsteer. Moving the UCA inner pickups (ala G mod etc.) does change the bump curve but the changes in this case are rather small in the grand scheme of things. You can get about as much change in the bump (steer) curve by changing the caster 3 or 4 degrees (which changes the height of the steering arms and outter tie rod ends). When I`m doing (or redoing) steering I take it for granted that there`s going to be some bumpsteer but I strive to make it small enough that it isn`t noticable. Katz is exactly right (as usual) that you can never dial bumpsteer out until the lengths and heights of the steering points are both perfect. However that takes a HUGE amount of work (and costs customers more money than almost any of them are willing to spend).
I`ve boiled it down to this, the steering arm and spindle swing in an arc (viewed from the front or rear), the tie rod ends also swing in an arc. Ideally the arcs would look like they were drawn with a compass and would overlap exactly but in our world the curves are eliptical and usually way out of sync. There`s most of yer bumpsteer. What I try to do it match the arcs so that the apex of each overlaps at ride height. That way you get very little deviation for the first few inches of bump and droop,where you car is 90% of the time. Even at extreme travel the deviation will still be much less that when the arcs were totally out of sync. You can generally get it good enough that the dial indicator on the bumpsteer gauge just quivers a bit for half of the total travel.unless it`s something with plain god awful steering like a `46 Plymouth. As Katz basically said moving the arcs is most easily done with vertical changes to the tie rod ends,center link etc.
Once you`re at this point I personally don`t think it`s worth going through all the work to fab a new R&P or centerlink and tie rods just to improve the bump curve toward the extremes of travel unless we also correct the poor scrub radius on our older cars which induces bumpsteer-ish effects also. In other words if Dave did his homework and spent some quality time with a bumpsteer gauge their R&P should be able to achieve pretty nice results G mod or no and even if the inner tie rod ends are off slightly inboard/outboard.
Of course if you were building a car from scratch,forget everything I just said and make it perfect because you`ve got no excuse not to. :) I`ll shut up now. ;) Marcus SC&C

Marcus, thanks for putting everything into a better perspective, and revealing how realative or unrealitve a small amount of bump steer is. I ned to fly you out to AZ. to give some lessons to the students. We look foward to working with you and your products, and of course Maval/Unisteer's R&P system, thanks again for all your help. Bob AZ

[Marcus SC&C]

Thanks Bob,keep us posted on the R&P.

Hey Dave (Unisteer Dave). If you`re reading this,I hope you`re going to have the new Camaro R&P at the HotRod and Restoration show in Indy next week. I really want to see it up close. It sounds pretty good so far. :) Marcus SC&C

[awr68]

Just got back from the Portland Roadster Show where Race Tech, a retailer for Unisteer, had one of these R&Ps at their booth...from what I can tell it's a very nice piece. The salesman from Race Tech thought it was a little on the heavy side primarely due to the bracket material thickness being over sized "after all it's only steering" he said...I disagree, and wouldn't change a thing...well if the rack was available in silver that would be cool! This guy is only a distributor and is second guessing the engineering of the product and is going to be coming out with his own soon, actually Speed Tech (he also sells ST parts) is going to be building the new rack with lighter weight parts...I just hope they know what they are doing, as this whole steering/bump thing seems to be tricky and we all know that ST doesn't seem to have any answers when it comes to the geometry of THEIR control arms...Sorry but the salesman was not only dogging Global West but also DSE...rubbed me the wrong way!! Also with this GP we are actually getting a better price than this guy gets...I think that upset him a bit...I guess we're even!! :)

All in all I really like the price and look of this product and cant wait to place an order!!

BTW, The DSE control arms are nicer and more adjustable than the ST arms....

[zuess4u]

Just got back from the Portland Roadster Show where Race Tech, a retailer for Unisteer, had one of these R&Ps at their booth...from what I can tell it's a very nice piece. The salesman from Race Tech thought it was a little on the heavy side primarely due to the bracket material thickness being over sized "after all it's only steering" he said...I disagree, and wouldn't change a thing...well if the rack was available in silver that would be cool! This guy is only a distributor and is second guessing the engineering of the product and is going to be coming out with his own soon, actually Speed Tech (he also sells ST parts) is going to be building the new rack with lighter weight parts...I just hope they know what they are doing, as this whole steering/bump thing seems to be tricky and we all know that ST doesn't seem to have any answers when it comes to the geometry of THEIR control arms...Sorry but the salesman was not only dogging Global West but also DSE...rubbed me the wrong way!! Also with this GP we are actually getting a better price than this guy gets...I think that upset him a bit...I guess we're even!! :)


BTW, The DSE control arms are nicer and more adjustable than the ST arms....

All in all I really like the price and look of this product and cant wait to place an order!!

AWR68, Im glad you were able to check it out first hand. As far as silver I dont know, right now the options are black or chromed. Im not sure you can make the system SUBSTANCIALLY lighter with out compromise, but Im sure with the right material it can be done.

I know in the past a few guys on this site had disagreement with ST, but if they come out and R&P Im sure it will be quailty as well.

By the , for anyone else. We need to keep this GP low keyed as possiable. This was the very thin Dave was affraid of. He didnt want his distributors to know of the price we were getting. So let try to remeber that portion. Thanks for everyones intrest, and I hope Im getting yall the info you need to make your decisions. :scared:

[awr68]

Sorry, I didn't realize we weren't suppose to talk about the price since it's in the GP thread...hope I didn't screw anything up!! These guys didn't seem to be the type to make a big deal of it since they plan on building their own and not selling Unisteer's anymore...hope Im right, again sorry...I was just a little pissed (and probably not thinking) they were slamming GW and DSE, after all they have done for our hobby and the industry that wasn't cool!!

[zuess4u]

Sorry, I didn't realize we weren't suppose to talk about the price since it's in the GP thread...hope I didn't screw anything up!! These guys didn't seem to be the type to make a big deal of it since they plan on building their own and not selling Unisteer's anymore...hope Im right, again sorry...I was just a little pissed (and probably not thinking) they were slamming GW and DSE, after all they have done for our hobby and the industry that wasn't cool!!

Not a big deal, do not sweat it, Im sure everything is fine. And I understand you wanting to get a little defensive. I know how you feel, I play in a band, and there are always critics and haters. And negativity in any business will end up short lived, so I wouldnt worry too much about those cats.

[awr68]

Thanks for understanding!! I bet they wouldn't have been so negative if I wasn't wearing my PT.com sweat shirt and they could see the DSE shirt I had on under it...who knows.....