exactly!

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Chad:

Has anyone that you know of ever broken an axle with a PT Car where a full floating axle would have made the difference?

To the best of your knowledge does anyone on this board drive their cars hard enough to justify the expense?

Circle Track Cars, Stock Car Racing etc. are always loaded to one side of the car. I can understand why this would make a difference over 500 miles, especially if they are basically loaded continuously over the length of the race.

Now if changing the rear pumpkin was a necessity, I would understand as putting the exact "Best" gearing is important enough to make a difference.

I know a fair amount of the Bonneville Car use them for that reason. (It sure wouldn't be because of side loading):D

Anyway thanks for responding, I look foward to your imput on these questions.

Ty

Ty,

I really can't answer your first question as I am just entering the PT world myself.

As far as I can tell there are alot of people on this board that drive their cars hard, that is one of the reasons I like this community so much. Alot of people talk, but not many back up what they say. As far as expense, it is not all that different. Maybe 2-3 hundred bucks. As I said the issue is brake kits, i don't know of any street kits with parking brakes.

Your third comment is only partially true. I never dealt with 500 mile races. I was involved with asphalt short track racing on .5 mile paved ovals. Most of these races were between 25 and 50 laps. In these short races I have absolutely seen Moser, Strange etc. axles break due to the side loads. I don't have personal experience yet, but i would think that on most road coarses during the length of a race or hot lapping you could achieve a similar number of cycles with the amount of turns on the coarse.

As far as quick third member changes, you could look at this in several ways. You may not need changes for a particular track, but you would make it easy on yourself to say change from a road trip gear to a track gear to a drag strip gear. Althought any rear with a drop out third member can accomodate this somewhat easily the floater adds to the ease.

I would absolutely run a floater at Bonneville. If for nothing else I keep all for wheels even with a broken axle. That's key! LOL

All this being said, we did not put a floater in our truck project. While we are building it with the PT style, my Dad will see very little if any real track time with it. So the massive amount of choices in brake packages lead us to use a standard 9" custom built.

Later

As do Ford-style bearings and disc brakes.

I fully understand the need for a full-floater setup, but not in our application. Most people here don't really run their cars that hard in comparison to competition applications. Most cars here wouldn't peak 1.5g in a road course, nor do they sustain high lateral loads for very long. The ONLY time I've seen a axle break at the flange was an off-road rig using stock 30 year old axles.

I think the only reason why I'd do it so I can run some crowned axles and -1 degree camber. I'll save the weight and put the cash somewhere else. Does this mean we should run 15" wheels too?

Oh no you didn't!

All good information Matt. I wasn't even going to go down the cambered rear avenue at this point. This is a great thread. I have met alot of people with alot of know how that don't know what a floater rear is. By the way our 9" is hung from one of your tri-angulated 4 links.

i have seen that the full floaters can be ordered with up to 1.5 deg negative camber... doesnt that put alot of wear on th ecrowned axle and on the drive plate?? i mean there are no CV joints in there... just a splines axle that is 1.5 degrees off in allignment??

fabricating some brackets for a corvette caliper shouldnt be rocket science, and if the cambered rears dont wear like a mo-fo it would be cool to run a cambered one just for some added lateral grip

but how much camber then?? .5 or 1 degree? and should one run alittle toe as well to make the tires wear even??

I almost shot water through my nose! Glad you took it with humor, that's how I meant it. Hope that tri 4-bar works well for you. It sure has for us!

Deuce, it does put some wear on the splines...don't expect tens of thousands of miles of use out of them. But it isn't bad. In fact, non-crowned axles can run up to 3/4 degree without excessive wear. I wish I could quantify "excessive", but I can't. If I were to do it (and I'd love to), I'd run a 1/2 degree to be safe. It's tough to do, though.

whats tough??

It's tough to bend the tubes accurately while maintaining that angle with respect to the necessary pinion angle.

...and if you ever change the pinion angle down the road you just introduced some toe into the picture-- which will become additional roll steer. And hopefully you don't find out that it's roll oversteer, especially during a situation when you least expected it. :willy:

I'd love to hear from someone who has driven a cambered rear end on a leaf spring car... I can imagine as you get on and off the throttle and pinion angle changes and things change from toe in to toe out it might get a little exciting. :)