I have been debating these spacers since they were introduced. I have yet to purchase them until hard facts are shown on why we need them or if we even do. Thanks for this thread guys

 

thanks mx5.

i look forward to billman's inspection, analysis, and conclusion

 

Me too.

Here's a picture of what I think the relationship is between operating angle (oa) and transfer effecincy (purley as a function of angle, without any other considerations).



Note how slowly effeciency changes at the smaller angles, below say 20-25 degrees?

If I'm using the wrong equations I won't mind being corrected.

 

The test car is due in June 18th

 

I was hesitant to start the thread, but this is going to be fun.
Sorry if I sounded like I was being impatient.

 

RED MX5 Posted on May 22 2007, 12:04 AM
[QUOTE]If it's an angle problem then the CV joint design on the S2000 is not up to industry standards, and I'm pretty sure that's not the case.

Anyone have any reason to believe otherwise?
SpitfireS? What do you think?

 

Have a look at this:
It looks like the wheel center is higher then the output shaft center.
Not much, but not in line.
I went to have a look at my car and just by eyeballing it, it looks like the axle is going "down" towards the bucket.
I'm at OEM ride hight, with Koni Yellows on high perch.
Lowering and setting the camber back to OEM spec will increase the angle between bucket and axle.
The wheel center will stay where it is and the diff will drop.
With every revolution the spider bearings will travel more inside the bucket.

This drawing is not as exact as measuring on a car, so we certainly need Billmans measurements too (NOW!! ), before we can put this to bed

 

Yea, the buckets pit because the balls move back and forth as the half shaft angle changes with suspension movement. That's normal and happens regardless of the cars ride height. Softer suspension and greater suspension travel, as well as adding in steering angle, should make the pits even longer, but that's just the way CV joints wear. (I think. )

If you look at my graph you'll see that a 6 degree change only makes a small change in the joint's effeciency, unless you're out past 45-degrees. Maybe I should have plotted all the way to 90-degrees, but think about it ... at 90-degrees the joint can't function no matter how much angle the balls and cup allow. You need gears or a flexable shaft to turn 90-degrees. (I think. )

Anyway, the point I was trying to make was that even if the spacers do change the angle, the chage is certainly less than 25-degrees (WAY LESS) and even at 25-degrees the angle only makes a tiny difference in the effeciency of the joint, so stresses don't go up much.

I still wonder about the wear patterns. The ride height affects where the pits develop as the joint wears, and if changing the ride height moves the wear pattern far enough there might be some interaction with the original wear pattern. Think about this for a minute. What happens when the CV joint cups are pitted, and you swap the cups from side to side.

Billman, what happens when you swap worn cups side to side?

SpitfireS, I'm still sticking to "I don't understand how the spacers help anything and want an explination that answers all the questions that have been raised." Actually, it seems to me that the guys making the spacers should be able to explain what they do in terms we can all understand, and if the spacers do anything beneficial then I don't understand why none of them have explained it to us yet. By now I'd expect Billman to have some specific things to measure to support the use of the spacers, but without any understanding of what they're actually supposed to do ...
Well, I just don't know.

 

[QUOTE=SpitfireS,May 22 2007, 07:51 AM]
Have a look at this:
It looks like the wheel center is higher then the output shaft center.
Not much, but not in line.
I went to have a look at my car and just by eyeballing it, it looks like the axle is going "down" towards the bucket.
I'm at OEM ride hight, with Koni Yellows on high perch.
Lowering and setting the camber back to OEM spec will increase the angle between bucket and axle.
The wheel center will stay where it is and the diff will drop.
With every revolution the spider bearings will travel more inside the bucket.

This drawing is not as exact as measuring on a car, so we certainly need Billmans measurements too (NOW!!

 

MX5,
I have half shaft spacers on my car. After my warranty paid $1000 to replace my rear CV joints, I figured the price of the spacers was cheap to keep the new ones from going bad. I got my info from this site that I "needed" these. I really appreciate your efforts to find out how much difference they really make, although it's too late for me I guess.

The only place I disagree with what you've said so far is how Honda surely designed the CV joints to work over the entire range of suspension travel. Yes, I'm sure that's true but you can't expect the parts to last as long at the ends of the travel. Just like you can't expect your motor to last as long if you run it at 9,000 rpm all the time. Right?

JASON