McMuffin

So im guessing that AP1's do need them. MY00 is slammed on the stock 16's and i am experencing some of these problems. I just recently purchased a set of spacers im going to see how it works out.

S2KSuzuka

I mis-spoke when I said I thought the axles were longer. I knew there was a reason the ap2 were said to not need the spacers. I didn't make it up, just have a sometimes faulty memory...lol

Mitch

SpitfireS

Adding a spacer between the LSD output shaft & CV bucket does not move the CV spider bearings more towards the LSD and the output shaft "bearings".
All it does is move the CV bucket more over the spider gears.
The axle has a "fixed" CV at the hub, the outer CV, it can't move in or out.
Besides, the LSD output shaft (the whole shaft actually - up to the outer CV)is "floating".
It does not have its own roller bearings.
The output shaft splines grab into the side gear inside the Torsen unit (LSD) and kept in place by the circlip.
The side gears are kept in place by the planet gears.
The planet gears are kept in place by the Torsen housing.
All those gears do not have bearings because the Torsen works on friction and torque and therefore those gears need to be able to move a little.
The bearing you see there only supports the Torsen unit.

RED MX5

Hi JWKim.

I for one am glad to see someone like you finally get involved in this discussion.
This is the kind of input we need to understand all this, and it's always best to get it right from the horses mouth. Just for the record, it is a farry tail that the AP2 half shafts are longer, so when I said that I was not making up another fairy tail, but rather just asking who makes this kind of crap up. If you are saying that the AP2 half shafts ARE longer (which does not appear to be the case) then I don't understand why they have the same part number as the AP1 half shafts. No need for you to get upset about it and accuse me of making up fairy tails when anyone can see for themselves that we're just looking for the facts here.

Anyway, until there is some reason to believe otherwise I'm assuming that we're all on the same team here, and all merely looking for truth and understanding. Your input can only help, and FWIW, I appreciate it. Hopefully you will understand that there are going to be more questions, and won't mind responding to them.

I would encourage you to look at me as a potential customer (because I am) who simply doesn't understand the need for the spacers. I have a modest FI setup and am lowered, and have been told that I need spacers to save my CV joints, and if that's true I need to understand why I need them. It's not that they're expensive, but like many people, I don't make mods to my car that I don't understand. I expect a reputable company to be able to explain how their products work, and don't think that's too much to ask. Hopefully you feel the same way, because I've still got some questions.

I'd like to hear your response to the points SpitfireS raised, but also am a little confused by some other points you raised.

Are you saying that heavier wheels and tires increase the unspring weight enough to use up all the suspension travel ("edge of suspension travel")? I would think that if the aftermarket wheels and tires were actually that heavy then CV joints would be the least of my worries.

I understand. The CV joint is designed to work without excessive vibration at any position within it's operating range, which covers the suspensions full travel. If I had even a small increase in vibration due to lowering my car, my CV joints will wear out much quicker, but the CV joints are fine as long as they are operated within their intended (design) range. Outside that range there will be a good chance that vibrations and other issues will result in a CV joint failure. From what you say, would I be safe to conclude that since I have not had any kind of CV joint problems I must not be getting "even a very small vibration" becuase if I were it would have worn out my bearing "much quicker?" That seems reasonable to me, and based on that, it seems that a 1" drop is not enough to cause the problem you describe here. So how low can I go before vibration DOES become a problem?

Basically I guess I could summarize all the above into two questions.
1) How heavy do the wheels and tires need to be before the spacers are needed?
2) I know I'm OK with a 1" drop, but how much lower can I go before I need the spacers?

Billman will be measureing this soon, but you might also tell us how far the balls move with an inch of drop. Since you guys have already done the R&D you could tell us now rather than making us wait for Bill's measurements. So, one more question.

3) Obviously the ball movement is not linear. No doubt you guys measured and plotted it out during your R&D, but we don't need the entire plot. Just a few data points would be enough, like perhaps the ball movement at 1", 2", and 3" of travel. Can you provide that, or do we need to wait for Bill to measure it?

RED MX5

I do understand how the joints and suspension work (or at least I think I do ), so the drawing didn't help much, but just to be clear, I'm not saying that it does or does not matter, I'm just explaining my understanding of how things work, and asking how/why/when it matters. I've done the best I could to explain my understanding, and am waiting for measurements to help us all figure out what's really going on. Now that we have someone who is making the spacers involved, we should soon have access to some numbers that give us a meaningful explination. If that doesn't happen then we'll just have to wait for Billman to do his measurements. I'm still on the fence somewhat, because we only just had someone who is involved with the spacers join in, and it remains to be seen what we might yet learn.

Mitch, I did not say that you or anyone else made the half shaft length difference up, but SOMEBODY made it up, becaue I've heard it a dozen times or more. This kind of thing doesn't make itself up and post itself on the Web; That takes people and imagination, and it would be easier to understand things like these spacers if that didn't happen.

FWIW, I believed it was true when I first heard it, and I probably repeated it a few times before I found out that it was wrong. Fortunately the conclusion, that the spacers aren't needed on the AP2, is (apparently) correct, even if the explination of why was incorrect. Interestingly, as recently as last week I saw a promotion for the spacers that said they were needed for both the AP1 and AP2, so apparently the vendors selling the spacers don't really understand them either. Do they must make it up, or do they get it from their suppliers?

I'd like to hear from a vendor or manufacturer who claims that the spacers are needed with both AP1 and AP2, so that I could understand their reasoning. I do not believe that they don't have *some basis* for their claim(s), and I'd like to understand them (too).

Anyway, now all we need to figure out is whether or not they're needed on the AP1's, and I suspect that we're going to have to depend on actual measurements to sort this out. Certainly I'd think you get more added vibration from joint angle than from ball/cup position, though they call them "Constant Velocity" joints for a reason, so maybe not. In any event, your comments about the axle length were helpful, because they brought up one of the myths that has been floating around. Too bad JWKin took my comments about it as a flame, but it really is just a fairy tail somebody made up, and the fact that the half shafts have the same part number proves it. LOL, I didn't make it up either, and have told it pretty much the same way you did, because that's the way it was told to me; Faulty memory not-with-standing.

Billman250

Lets rewind, and find out some facts.

There are to many variables to be considered, and myths can dramatically affect the outcome.

Lets start with this...I just measured the outside flange dimension of an AP1 and an AP2 dif about two minutes ago. They are EXACTLY the same. Even if the flanges are different part numbers, how they sit in the dif is the bottom line.

I had a machinist's biz for 10 years so I'm pretty good with a ruler

So lets get this out of the way first.

RED MX5

Very professional approach.

Let's take one issue at a time, and for my nickle, Billman is most qualified to ask them, if not from his extensive experience, then from the amount of respect he has earned here on S2kI over the years.

Bill, I'll throw in questions as they come up, if I feel I must, but I'm more than happy to let you lead the discussion. This is a VERY GOOD approach. Everyone will be able to follow along easily as long as we address one issue and/or question at a time.


[QUOTE=jwkim,May 29 2007, 04:15 AM]Wider/longer flanges does same thing as shaft spacers.

saaboteur

I am following this thread with keen interest. Very informative posts by guys who know the car inside and out.

FWIW, my stand alone turbocharged Saab makes about 300 crank hp on pump, and made ~240fwhp on 111 leaded race gas. The front suspension setup is double wishbone and of course a driveshaft coming from the tranny/diff in the middle. When I R&R'd the left rear axle on my S2k (due to a dead wheel bearing), the whole thing was remarkably similar to my Saab so I felt quite at ease in working on it.

Anyway, the point I want to make is that the Saab made 165 crank hp stock, I've had it lowered for years now and have never had any driveshaft related issues, nor abnormal tranny related issues due to lowering. The older Saabs do blow up their trannies if one runs huge power through them, but that would be stock or lowered ride heights and is another story altogether. The first I'd ever heard of driveshaft spacers was on s2ki.

I'm contemplating some suspension mods to the S2k, and if I need the spacers, then I'm down. If not, then it means another C$200 or so I can spend on other stuff!

If interested, you can link to my page on the Saab from my sig. Here's also a pic of the transmission setup:

http://members.shaw.ca/saaboteur/spg/newst...-difflocker.jpg

RED MX5

[QUOTE=saaboteur,May 29 2007, 05:50 PM]I am following this thread with keen interest.

Billman250

In my book, 20mm is a mile.

This measurement is accurate within 1mm. I wouldn't lie to you guys, have I ever?