Anyone using Heidt's Control Arms

[shessel]

Anyone using these? How are they? They offer a set that narrows the track width 1" per side and I'm thinking of ordering a set. Currently the front wheels on my car are setting 1/4" fron the outer fender well and I'm looking for more clearance (without changing wheels). I have a set of US Wheel slots on my car and can't get new ones with a different offset, so I'm looking to other means.

Steve

[dennis68]

Narrowing track width by using shorter control arms...or any other method for that matter is on the top 5 things NEVER to do to your car. You will be ruining your suspension geometry for aesthetic value.

[baz67]

Would it not be cheaper to just buy rims with the correct offset? It would definitly be the better way to go.

[shessel]

It would be cheaper if I could still get these wheels. Nobody's produced slot mags in years, and I really don't want to change rim styles. My only option for new wheels would be ebay, and that's if the style and size happens to be correct.

As far as changing the suspension geometry, please clarify what's bad about it. People change steering all the time (front steer, rear steer, from gear to R&P, ect.). I'm not changing the overall track width of the car as the backspacing on the wheels will put it right back to the stock width. Springs and shocks are all in the stock locations as well as the sway bar end links. SLA arms will allow the wheel to move correctly up and down, as well as these arms are built for better alignment as are several other aftermarket arms out there.

I'm not challenging anyone's thought process here, just trying to understand the product and issues associated with it.

Steve

[dennis68]

Going to a shorter control requires running less offset to maintain track width, that means increasing already bad scrub radius to big time bad scrub radius, maybe unsafe scrub radius. Shortening control arms also changes the location of the lower ball joint which is one of 4 determing points for figuring roll center height and front view swing arm length.

I highly suggest you spend some time buried in suspension geometry fundamental books or research before you go changing major factors like control arm length.

[shessel]

Dennis,

I appreciate your input, that's what I am doing is researching.

Steve

[shessel]

[QUOTE=dennis68]Going to a shorter control requires running less offset to maintain track width, that means increasing already bad scrub radius to big time bad scrub radius, maybe unsafe scrub radius. Shortening control arms also changes the location of the lower ball joint which is one of 4 determing points for figuring roll center height and front view swing arm length.


OK, Denny, I understand what you're saying about SR, but if I'm already running these wheels, and just need to move them inboard for fender clearance, the control arms won't change SR...Correct? From what I was just reading about SR, the line between the ball joints as well as the centerline of my wheels/tires is still a constant, it's just the whole assembly moves inboard 1" on each side. As for the roll center I'm still trying to understand that as it relates for my car, but this car will see minimal track time.

[dennis68]

Correct, if are insistent on running those wheels than changing the control arms will not change SR, I don't recommend it but....

Keep in mind that while concepts like FRCH, RC migration, FVSA, and SR as they are typically discussed on this board typically apply to performance driving but they are also very much important to daily drivers. The factory spent thousands of hours to set design those specifications into that chassis, albeit not without some compromise but it does what they designed it to do. You now want to redesign the entire system (unintentionally but still being considered) without the slightest clue as to how it may affect the chassis and possibly upset the chassis. Possibly to the point that in a panic maneuver you could experience the phenomenon commonly referred to as "jacking" and worse maybe during braking in which case you would lose all control. Are you a little scared yet? Good. This is important stuff you are considering doing your chassis and it would be foolish to attempt such a change without the full understanding of the possible repercussions of your actions.

This is not a flame, more of an educational experience devoid of any substance, I'll leave that to you. Try a search as we have discussed in some depth these aspects before and there also some recommended reading suggestions through most of the more informative threads.

[gchandler]

There are shops that you can take your rims to to have the backspace changed. Somebody would just need to mill of some material from the backside of the rims. You could probably get is donne for no more then a couple of hundred dollars.

[z65mm6]

Don't know if this will help or not but American Racing lists on their website an "ansen sprint" which if they're not a dead ringer they pretty close to the tumbnail in your original post. American Racing lists them in 15x7 with 0 offset 4 inch backspace 15x8 again 0 offset and 4.5 inch backspace, or if your wanting to update to a newer tire they also offer them in the 17X7 or 17X8 again with 0 offset with 4 or 4.5 inch backspace depending on the width.

[Marcus SC&C]

No offense but changing the whole front suspension just to use wheels that don`t fit properly seems about like tearing the front wall out of your house and building a new one because the screen door sticks. ;) What are you running for camber? If it`s setup stock you can gain another 1/4" or more by going to -.5*to -1* camber. It`ll handle better too and with the backward + factory camber curve tire wear shouldn`t be an issue. Also with the stock suspension setup everytime you go over a bump the top of the tire shoots outward making that 1/4" of clearance closer to 0". The G Mod and/or our Stage 1 or Stage 2 suspension packages will neutralize or reverse the + camber curves and make the top of the tire tuck in when going over bumps giving you more fender clearance in jounce. Marcus SC&C

[79T/Aman]

not to mention the change in "lever" on the spring and I don't think the sway bar will fit any more either, so don't do it

[shessel]

Don't know if this will help or not but American Racing lists on their website an "ansen sprint" which if they're not a dead ringer they pretty close to the tumbnail in your original post. American Racing lists them in 15x7 with 0 offset 4 inch backspace 15x8 again 0 offset and 4.5 inch backspace, or if your wanting to update to a newer tire they also offer them in the 17X7 or 17X8 again with 0 offset with 4 or 4.5 inch backspace depending on the width.

Thanks for the info. I was actually poking around last night looking at wheels and saw these. These weren't there when I bought mine, or I'd just have bought these from the start.

[shessel]

There are shops that you can take your rims to to have the backspace changed. Somebody would just need to mill of some material from the backside of the rims. You could probably get is donne for no more then a couple of hundred dollars.

This was another option I was looking at. Most of the people I've talked to are saying not to do this as it will hurt the strength of the wheel. Currently the center of the wheel (lug face) is about 15/16". I'd need to get at least 1/4" off to get a comfortable clearance.

Any opinions?????

[shessel]

[QUOTE=dennis68]Correct, if are insistent on running those wheels than changing the control arms will not change SR, I don't recommend it but....

Keep in mind that while concepts like FRCH, RC migration, FVSA, and SR as they are typically discussed on this board typically apply to performance driving but they are also very much important to daily drivers. The factory spent thousands of hours to set design those specifications into that chassis, albeit not without some compromise but it does what they designed it to do. You now want to redesign the entire system (unintentionally but still being considered) without the slightest clue as to how it may affect the chassis and possibly upset the chassis. Possibly to the point that in a panic maneuver you could experience the phenomenon commonly referred to as "jacking" and worse maybe during braking in which case you would lose all control. Are you a little scared yet? Good. This is important stuff you are considering doing your chassis and it would be foolish to attempt such a change without the full understanding of the possible repercussions of your actions.

QUOTE]

No, I'm not scared, just because I don't know it all about suspensions, doesn't mean I can't drive, or aren't willing to learn before I act. I was kind-of set on using these wheels until I saw the Ansens last night. I'm just going to a certain performance and look and am attempting to way out the options and learn what I need to do to get it done. I'm not "clueless", I do have some knowledge of suspension geometry, just lacking some of the details.

On a side note, I ballparked my scrub radius last night and I'm at 2.5" right now (with the wheels I want to use on the car). I pulled the wheel, set the ride height with the jack under the control arms, marked the floor with a laser level through the centerline of the ball joints, reinstalled the tire and marked the centerline of the tire. I came out within 1/16" doing it a second time. From reading other posts and sites, this isn't the best for racing, but it's not bad for street applications, and its not the 3-4" you were stating above.

I still haven't decided which route I'm going, but I am still looking for opinions of the SR numbers I'm seeing.

[dennis68]

SR is the least of your worries. I'd be far more concerned about how to fix the RC migration, FRCH, and FVSA numbers.

You would be much better off looking for a wheel alternative. The wheel should never dictate the suspension design. You build the suspension, then look for a wheel that will fit it.

[shessel]

Denny,

As far as the RC migration, my car currently sits 3" lower all around as well as I have hotchkis sway bars on both the front and rear. The CG of my car is lower than stock. From what I can tell, I'd be raising the RC alittle with the shortened control arms (no I haven't bought them yet). From what I can figure, the RC and the CG should be farther apart rather than closer (correct?)(the RC lower than the CG), this allows the torque of the twisting body in a turn to be less severe? I'm still trying to understand this, but there's not alot of good info out there that I've found.

Thanks,

[dennis68]

FRCH should be between -1 to 3" measured at ground level. With a 3" spring drop I would bet your FRCH is well below ground level. RC migration is very difficult to predict without a simulation. Shortening the control arms in itself will depend on the pivot and ball joint heights to determine how much affect on FRCH it will have. The shortened arms will have drastic affect on RC migration and camber gain. I'll post an example of what an inch of control change would do my chassis tonight, the visual always helps.

[baz67]

You are correct that you would raise RC, but your RC and CG will be closer together. The CG of a typical lowered Nova is around 18-20". It may be higher than your calculations because it is the CG of the sprung mass we need to worry about. Taking all of your suspension parts(unsprung mass) off will raise the CG. You will lessen the roll moment, but you will increase the jacking forces on the front end. A bad thing. Not to mention the two inches you will lose in track width. Another bad thing.

It seems you want this to be the easy fix. You are playing with fire by changing your front geometry. If this was a drag or show car ONLY than do it. If not than your easy fix is to change the BS on your rims.

Do me a favor and measure the distance from the ground to the center of the front bolthead of the lower control arm. With that known it would be easier to see what your geometry is really doing. I ask because a 3" drop on the front seems a little much. The lower you go staticly the shorter your FVSA. You may already be past the sweet spot of your suspension and by shortening the CAs you may make it worse.

[shessel]

OK, another question...

If raising the roll center is such a bad thing, how come I've read in 2 different places now that the Guldstrand mod "raises roll center" as part of the improvement. The last place I read it was on DSE's site in the FAQ area.

Another site I saw a reference to raising roll center being a positive is on David Pozzi's site in the "how do I do the Guldstrand mod" section. Now, in all fairness to Dave's site, he did mention that the Guldstrand engineer mentioned going any lower with the mod would have a negative effect on roll center.

So which way is it.....What am I missing. Is there a certain number for roll center that allows for the best handling? Am I missing a fine line in setting up the handling here? All the previous posts indicate raising roll center as being really bad.