Straight Axle Camber

[Zachalanche]

I'm interested in possibly putting .5 -1 degrees of negative cambur in my 9 in rear housing. has anyone done something similar? what were your methods, and what potential problems could I run into (premature bearing wear, axle failure etc.) thanks in advance for your input.

[DynoDon]

The NASCAR boys run rear end camber on the Ovals. On banked tracks I think they will run somewhere in the area of 1.5-2 degrees positive on the left and 1.5-2.0 degrees negative on the right. On Flat track some teams will go to Zero Camber and on Road Race courses anywhere from zero to 1.8 degrees negative.
But that is with full floating axles and that helps to relieve some of the wear issues at the splines. On a non floating axles, I would not consider more than 3/4 degree or I think you will have wear issues with both the axle spline and the diff spline.

[Zachalanche]

I am running non floating axles. your recommendation lines up with my idea of staying under an 1 degree. should I be trying to add any toe?

Also more info: this is for a car that will be set up mainly for open road racing and used occasionally on track days at millermotorsports park.

[exwestracer]

With non-floating axles, you are really going to put some strain on the outer bearing seat radius area. We normally try to tweak the housing as far out as possible, but that is using a floating axle shaft. With non-floaters, you would want to bend the housing IN as far as possible, but that ends up turning the housing into a giant banana... Dead splines will end your day, but breaking the flange off the end of the axle could end your life...

Open road racing? Are you sure it's worth the risk? Mark Donohue tested the idea on his 1969 Trans Am Camaro (to the point of using CV joints at the ends of the axle shafts) and found out it wasn't one bit faster, even on the tires of the day. With modern low-profile tires, the need for counteracting sidewall flex is greatly reduced. The NASCAR guys did it (I believe they are now limited to 1deg) because they run right on the ragged edge of traction ALL the time, and it added a little life span to the right rear tire.

I'm sure there will be all sorts of conflicting opinions and examples of it being done, but non-floating axle shafts are designed NOT to bend, and that's exactly what you are asking it to do. Just my $.02 from having been there.

[DynoDon]

Ray, I think the current rules for Cup limit them to 1.8 degrees, WITH full floaters. And I agree, it's not worth the effort. I ran .5 degree in my Tiger and could never tell the difference, on old Bias Ply Race Tires. I thought about this just last week as I was prepping the rear end for the Falcon and I stayed at Zero. Putting enough strain on the little 8" 28 spline as it is - but I do like the light weight!

[silver69camaro]

It's not too hard, but you have to know what you are doing.

First you'll have to start with a housing with no ends on it and the center section installed. Install the housing ends onto the axles (Ford 9" here), and mock up the axles to your camber and toe and tack the ends to the tubes. If you're good, you can fully weld the ends with minimal alignment change. I've found this method to be more accurate then bending the tubes. Also, because of the slop in the splines, it doesn't stress out the bearing because the axle is perpendicular to the bearing surface. It works really well.

On a stock width housing, you'll have to move the axle vertically about 3/8" of an inch for about 1/2 degree of camber, so you may have to increase the weld area on the tubes. Add some toe as well, about 1/8" total. Doing this really closes the gap between solid axle suspensions and independent.

[Nessumsar]

CV joints at the ends of the axle shafts

I have always wanted to try this. So much so I have been looking around for an axle in junkyards. It seems like the eaisiest, and most practical way to add camber/toe to the rear of our cars. I also like the idea of it being adjustable by use of tie-rods.

[Zachalanche]

It's not too hard, but you have to know what you are doing.

First you'll have to start with a housing with no ends on it and the center section installed. Install the housing ends onto the axles (Ford 9" here), and mock up the axles to your camber and toe and tack the ends to the tubes. If you're good, you can fully weld the ends with minimal alignment change. I've found this method to be more accurate then bending the tubes. Also, because of the slop in the splines, it doesn't stress out the bearing because the axle is perpendicular to the bearing surface. It works really well.

On a stock width housing, you'll have to move the axle vertically about 3/8" of an inch for about 1/2 degree of camber, so you may have to increase the weld area on the tubes. Add some toe as well, about 1/8" total. Doing this really closes the gap between solid axle suspensions and independent.

from what I can tell griggs racing does it the way you described
http://picasaweb.google.com/griggsracing/RearAxle#5479036531229244434

[Zachalanche]

With non-floating axles, you are really going to put some strain on the outer bearing seat radius area. We normally try to tweak the housing as far out as possible, but that is using a floating axle shaft. With non-floaters, you would want to bend the housing IN as far as possible, but that ends up turning the housing into a giant banana... Dead splines will end your day, but breaking the flange off the end of the axle could end your life...

Open road racing? Are you sure it's worth the risk? Mark Donohue tested the idea on his 1969 Trans Am Camaro (to the point of using CV joints at the ends of the axle shafts) and found out it wasn't one bit faster, even on the tires of the day. With modern low-profile tires, the need for counteracting sidewall flex is greatly reduced. The NASCAR guys did it (I believe they are now limited to 1deg) because they run right on the ragged edge of traction ALL the time, and it added a little life span to the right rear tire.

I'm sure there will be all sorts of conflicting opinions and examples of it being done, but non-floating axle shafts are designed NOT to bend, and that's exactly what you are asking it to do. Just my $.02 from having been there.

point well taken. This does however leave me curious how much there is to be gained with this. and perhaps if I determine at some point that lack of rear camber is limiting perfromance then maybe it is time to build a floating rear end.

I am also curious how much camber is possible before the non floating axle begins to bend.

[silver69camaro]

from what I can tell griggs racing does it the way you described
http://picasaweb.google.com/griggsracing/RearAxle#5479036531229244434

Yep, that would be the same concept.

[exwestracer]

I am also curious how much camber is possible before the non floating axle begins to bend.

If you attempt to relocate the housing end to gain camber, you are bending the axle and putting side load (down) on the diff side gears. Remember there are no bearings in there. If you bend the axle tube at the center, you get a banana but you are only loading the splines. Either way, at 3/8" offset for .5deg as Matt has suggested(or more), something is going to be unhappy....

[exwestracer]

I have built a system to "split" the axle in half, using a splined coupler and floating inner axle shaft. I'm running a floating outer end as well, but this would elimnate a lot of the bind; as the offset is split between 3 sets of splines and the axle bend is minimized. PM me if you're interested in how it works.

Having said that, I still don't think it's worth it in the OPs application...

[rentedmule]

Couldn't you just run camber tires rather than modifying the axle?

[Wicked]

I agree, trying to run a camber rear axle is asking for trouble as far as wear goes.

The point of negative camber is so that after the car has taken a set/rolled in a corner, that the tire is still flat on the ground for maximum contact patch. On a front engine car and considering the height of the COG and proximity to the front axle, camber is required to ensure a good contact patch during roll. With a live axle, the tires surface and axle will always remain parallel to the ground. Not as much to be gained on the rear.

The other issue with camber in the rear is you significantly reduce your tire patch during forward acceleration.

[Gitter Dun]

I just came across this thread this morning and I find it funny because I was looking at some recent track photos of my car in the corners yesterday and my front tires look flat but my rear tires show alot of side load and I was thinking of a way to remedy this. The first thing that came to mind was IRS but I am interested in hearing more about adding neg. camber to straight axle set ups. I think the first thing to do would be to talk to John Griggs and ask him if he has had any issues with his housing set up. Griggs does alot of road racing so I'm sure he would know of any issues by now. Anybody here know John very well?

[Wicked]

post the pics...just curious to see them.

[Gitter Dun]

post the pics...just curious to see them.

Here are a couple of picks showing lateral loads on rear tires. Not sure if it would be worth building neg. camber into rear axle but that is one idea I am thinking about.

https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif

[Wicked]

Here are a couple of picks showing lateral loads on rear tires. Not sure if it would be worth building neg. camber into rear axle but that is one idea I am thinking about.





Generally if your wearing the front more than the rears, you need more rear sway bar. That would increase the load on the rear tires and reduce the load on the fronts. I have built a rear sway bar for a front drive car in the past. Before the rear bar, the front were doing all the work. With the rear bar added(and adjustable) we can make the rear tires wear faster and do more work than the fronts in the corner. This is especially handy on a fwd car making 532whp.

In your case, your car appears to be doing the opposite. This is probably because you have not only the lateral load but also the motive force from the rear wheel drive. Perhaps you need a larger front bar(smaller rear bar would effectively do the same thing but would allow for more total body roll) to make your fronts work harder. If would also reduce the load on your rears and allow for better out of corner acceleration.

How do your tires wear after a track session? Does it push or is it loose in corners? What about under braking?

[Gitter Dun]

Tire wear is fine but I notice the rear tires getting hotter than the fronts when I'm checking tire pressures. Car handles great until the rear tires get hot and then the car starts to get loose. The loose condition typically happens during the late afternoon sessions when the track temps are there highest. So far the car has been behaving well under braking but I should probably up grade soon. Reason I say this is because I noticed the brakes starting to fade during my fastest sessions. Once again, seems to be happening when track temperatures are the highest.

You make a good point though, I going to see who makes a bigger front bar.

[Wicked]

Tire wear is fine but I notice the rear tires getting hotter than the fronts when I'm checking tire pressures. Car handles great until the rear tires get hot and then the car starts to get loose. The loose condition typically happens during the late afternoon sessions when the track temps are there highest. So far the car has been behaving well under braking but I should probably up grade soon. Reason I say this is because I noticed the brakes starting to fade during my fastest sessions. Once again, seems to be happening when track temperatures are the highest.

You make a good point though, I going to see who makes a bigger front bar.

Reason I ask about the brakes is to understand the handling bias.

[U_SAY_GO]

Do you have adjustable shocks? Taking out some rear rebound may also help what you are describing.

[Gitter Dun]

Do you have adjustable shocks? Taking out some rear rebound may also help what you are describing.

Yes, I do have single adjustable QA-1's but currently researching other shocks. It makes more sense to try and transfer work to the front of the car. I think I am going to take some weight off the rear also. I currently have a DSE 1 1/8" hollow front sway bar. I'm thinking of trying a 1 1/2" front bar and see what happens.

[silver69camaro]

With a live axle, the tires surface and axle will always remain parallel to the ground. Not as much to be gained on the rear.


Well, that's not exactly true. You don't always want the tire parallel to the ground, because tires perform their best with some degree of negative camber (the amount depends on the tire used).

My experience is this: adding rear camber will give you enough rear grip to require a heavier rear bar. That's a pretty big deal. If you don't think adding rear camber will help rear grip, then you need to try it for yourself.

[Norm Peterson]

Up to at least 0.75° total angle (considering camber and toe) in a non-floating axle shouldn't be any problem. That's about where the total has been in the axle that's been under my Malibu for 15 years of use and somewhere around 100,000 miles.

A little history - this isn't the original axle for the car due to loss of a C-clip while on the road that trashed everything inside, so some of that "misalignment" could have been the result of ITS original car being totalled. The diff has been replaced twice since, first time due to an opportunity to swap limited slip 3.27's in where the replacement axle had 2.56 (open). Second time was due to ring and pinion gear tooth breakage (EFI 355 + Tremec + 26 spline corporate 7.5"/7.625" is kind of iffy), at which time I replaced the driver side axle shaft due to the splines starting to show some twist.

But there have been no failures directly attributable to that axle housing/tubes having a little over -0.5° camber and there being somewhat less toe. Yes, I'd like to trade some (most) of the excessive toe for a little more negative camber.


Something else to consider - a solid axle with wheels and tires actually has a "roll stiffness" of its own just due to the fact that tire vertical stiffness is finite. Somewhere around 1°/g worth is probably a good enough number to use in most cases. IOW, if you see an end-on picture of a car cornering up around autocross-hard and you measure it with a protractor to have 4° of roll, 1° of that is apparent roll from tire deflection and the chassis/suspension roll stiffness is a little higher than you might have first thought at 3°/g instead of the whole 4°/g.


Norm

[exwestracer]

Well, that's not exactly true. You don't always want the tire parallel to the ground, because tires perform their best with some degree of negative camber (the amount depends on the tire used).



When that tire is 20" wide, it helps a lot! :secret:41861

[MrQuick]

Here are a couple of picks showing lateral loads on rear tires. Not sure if it would be worth building neg. camber into rear axle but that is one idea I am thinking about.

https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif


thats actually normal with the low RC you get with leafs and the sidewall you have. Also didn't help with leaky locked up shocks. Remember with all the mods and at that speed the force has to be applied somewhere right? Its to the tires where it belongs. Playing with air pressures would help with temp readings.

You would gain more putting the money into a dampning system that actually works. A link or IRS suspension would add adjustibility/tunebility to the mix.

To add, upgrading to larger brakes will help you go deeper into the turns and will help you carry more speed out of them.

You get to that bank we always talked about? LOL

[Gitter Dun]

I was wondering when your arse was gonna chime in. Got an iron on the fire and hoping it follows through. If so I hope to drop the car off in about a month. Yes, we still have alot of work to do.

[MrQuick]

I was wondering when your arse was gonna chime in. Got an iron on the fire and hoping it follows through. If so I hope to drop the car off in about a month. Yes, we still have alot of work to do.

I like to sit back and analyze other responses before I chime in. I hate echoing something that has been added already.

edit: in your case would be a band aid for your existing suspension deficiencies. ie shocks, tire pressures, tire contact patch, weight balance.
What we do not see or interpret from your photo is your speed, if your accelerating and if you at the correct apex for that particular turn.
Lets go with the small stuff and work your way up to the advance stuff.

We had a few track cars running camber in the rear and then we noticed seal failure. That was back in the 90's and the technology that exists today might make it worth the effort. I believe the Speedway floater that JCG's is setting up might be the hot ticket. Lets see how that performs.


Being able to adjust camber and toe would be something I am looking at now.

[Wicked]

Well, that's not exactly true. You don't always want the tire parallel to the ground, because tires perform their best with some degree of negative camber (the amount depends on the tire used).

My experience is this: adding rear camber will give you enough rear grip to require a heavier rear bar. That's a pretty big deal. If you don't think adding rear camber will help rear grip, then you need to try it for yourself.

Matt,
Please respect that yours isn't the only experience or opinion.

My response was in reference to adding camber to a solid axle and the wear issues(bearing, etc) that could result. I never said camber in the rear is useless. My point was the gain was small compared to the drawbacks for what he's asking. You obviously have done this yourself and tested it fully back to back with a standard live axle?

I have multiple vehicles running INDEPENDENT rear susp and of course we prescribe rear camber. But the point of the camber is to yield a mostly flat tire patch when the vehicle has taken a set in the corner(i.e.roll, camber gain in compression).

Bradley Buchanan
Mechanical Engineer
Honda

[silver69camaro]

Bradley,
My mistake, I misinterpreted your post. There shouldn't be any bearing or wear issues if done properly, and the gains are pretty big. I can see how the gain may seem minimal compared to the work involved to get to that point, as most people don't have the resources I have, and I know sometimes I take that for granted.

In my experience, the rear roll stiffness needs to be increased by about 8-10% to bring the vehicle back to a neutral state after camber is added (and I believe part of that is attributed to the large tire stagger). I'd be interested to run 0 rear camber in my BMW to see if the change is as dramatic. I should also note that along with the increased camber is toe-in, which does wonders as well.

If you're a ME from Honda, perhaps you can answer this for me: Do most OE's run high amounts of rear camber to keep the vehicle in a state of understeer? Or is there another reason? Just something I've always wondered about.

[Wicked]

Bradley,
My mistake, I misinterpreted your post. There shouldn't be any bearing or wear issues if done properly, and the gains are pretty big. I can see how the gain may seem minimal compared to the work involved to get to that point, as most people don't have the resources I have, and I know sometimes I take that for granted.

In my experience, the rear roll stiffness needs to be increased by about 8-10% to bring the vehicle back to a neutral state after camber is added (and I believe part of that is attributed to the large tire stagger). I'd be interested to run 0 rear camber in my BMW to see if the change is as dramatic. I should also note that along with the increased camber is toe-in, which does wonders as well.

If you're a ME from Honda, perhaps you can answer this for me: Do most OE's run high amounts of rear camber to keep the vehicle in a state of understeer? Or is there another reason? Just something I've always wondered about.

Trust me, I'd love for my normal job to be in a more high-performance capacity.

Is your Bimmer IRS? Really just depends on much work the rear is already doing.

In most of our multilink rear suspensions, we only adjust toe at the factory. The toe is adjusted via a cam bolt on one of the lower links. The toe change also affects the camber. Depending on the vehicle, camber range is between 0 and -1 degrees or so at normal ride height. When loaded the suspension does gain a lot of camber. This is just result of the upper arm being shorter than the lower. This obviously doesn't yield the best camber curve, but is more compact.

The toe in setting(0.08 degrees per side) helps to maintain an understeering vehicle. On the Odyssey, the lack of a rear sway bar is another "feature" that helps maintain a safer understeer tendency. On our race version(yes, race minivan), we built an adjusteble rear bar setup. The car also makes 532whp at the front wheels....so having the rear do a little more work was a necessity.

[funcars]

Another thing to be cautious of is the change that can occur from toe in to toe out because of pinion angle change. The more camber you have the better control you need to have of the pinion angle. I have a 1.5 degree negative cambered rear using a full floater and I could not run it with leafs even though I have extra stiffness in the front of the leafs. It got very nervous coming off corners. It is best to use a link type of suspension that does not change pinion angle as much. In regards to effectiveness they do make a difference in grip and will require suspension rate changes as mentioned previously. My first experience with a cambered rear was a transaxle Alfa with a DeDion rear that I changed to cambered. A DeDion behaves similiar to a live rear except for being lighter and having less suspension anti properties. It made the car far more predictable at the limits. It gave me confidence to try the cambered rear on my V8. It made a larger difference with the powerful but heavy pig Mustang I drive. Still will never be a true sports car, but does increase grip noticebly.

I had stock car products set up my housing, but speedway engineering does them too. SCP has changed names so I'm not sure what they do now. I do not worry about durability of the axles, the drive plates or the hubs - it is beefy stuff and well proven. I went to 5x5 wheels so I could use all of the brake hats, etc available for cup cars. There several different types of hubs for floaters as well with superspeedway being the strongest (and heaviest).

Many times you can find new surplus stock car parts at less than 1/2 cost if you look around and call folks like Tex racing and some of the cup teams. Another option is to buy a used (but not crashed and bent) floater housing with plus and minus camber and have speedway cut off the plus side and match the camber of the neg side with a new cambered tube. Crowned axles are about $125 each new and new hardened drive plates can be had for about $60 if you look.

[exwestracer]

I had stock car products set up my housing, but speedway engineering does them too. SCP has changed names so I'm not sure what they do now. I do not worry about durability of the axles, the drive plates or the hubs - it is beefy stuff and well proven. I went to 5x5 wheels so I could use all of the brake hats, etc available for cup cars. There several different types of hubs for floaters as well with superspeedway being the strongest (and heaviest).

Many times you can find new surplus stock car parts at less than 1/2 cost if you look around and call folks like Tex racing and some of the cup teams. Another option is to buy a used (but not crashed and bent) floater housing with plus and minus camber and have speedway cut off the plus side and match the camber of the neg side with a new cambered tube. Crowned axles are about $125 each new and new hardened drive plates can be had for about $60 if you look.

If you are determined to try it, and want to go to a floater, companies like Coleman and Winters make pre-cambered "kits"; where you have a straight flange on the housing, and only the bolt-on floater snout is cambered. This offers the advantage of being able to buy ends with different amounts of camber built in, instead of tweaking the actual housing.

[Skip Fix]

I want to think Herb Adams showed using as small cut in the tubes(10/12 bolts) and slow rewelding to get some camber back in one of his books or news letters back in the late 70s early 80s.