Traditional Limited Slip vs. Torque Bias, Please eduficate me! Options

[SirAndy]

Purpose of the car, in order:

Spirited street driving, occasional AX, occasional track days.



Here's what i think i know (IMG:style_emoticons/default/biggrin.gif)

LSD
- Always locks wheels together under acceleration and deceleration.
- Introduces understeer in slow corners.
- Generally considered the better choice for the big track.

TB
- Only locks wheels under acceleration.
- Acts like a open diff if a driving wheel is off the ground.



So, the question is, what should i get for my 915???

The car will never be a dedicated track car, it's mostly driven on the street.
The TB seems to be easier to drive on the street.
However, the slow corner understeer of a LSD could probably be tuned down with suspension settings.

The TB loses it's magick if one wheel is off the ground. In an AX setting, the suspension would need to be pretty stiff to keep both wheels on the ground at all times, would a LSD be the better choice here?


Anyone compared the two back to back in a 914?
(IMG:style_emoticons/default/idea.gif) Andy

[stewteral]

Purpose of the car, in order:

Spirited street driving, occasional AX, occasional track days.



Here's what i think i know (IMG:style_emoticons/default/biggrin.gif)

LSD
- Always locks wheels together under acceleration and deceleration.
- Introduces understeer in slow corners.
- Generally considered the better choice for the big track.

TB
- Only locks wheels under acceleration.
- Acts like a open diff if a driving wheel is off the ground.



So, the question is, what should i get for my 915???

The car will never be a dedicated track car, it's mostly driven on the street.
The TB seems to be easier to drive on the street.
However, the slow corner understeer of a LSD could probably be tuned down with suspension settings.

The TB loses it's magick if one wheel is off the ground. In an AX setting, the suspension would need to be pretty stiff to keep both wheels on the ground at all times, would a LSD be the better choice here?


Anyone compared the two back to back in a 914?
(IMG:style_emoticons/default/idea.gif) Andy

Hey SirAndy,

I believe it is well established that an LSD is the choice for a pure track-car with the advantage of "locking" the wheels for braking. This design also induces a good bit of understeer.

For the street and AX, I would choose the TORSEN (torque sense or ATB) design with it's ability to turn tight corners happier and less induced understeer.

However, NO ONE has mentioned the issue of COST and WORK to maintain an LSD. I ran an LSD when I was running SCCA in a Datsun 510 and after a season,
the clutch plates had worn to the point that the Diff had to be pulled and worked on. The Stock Porsche LSDs use carbon clutch plates (I've been told) and wear fairly rapidly. While Guard has better material replacement clutch plates, they are very expensive! Are you up for this burden?

With the TORSEN there is NO maintenance, other than making sure it has oil. I did quite a bit of emailing with the Quaif guys in England and they swear I could run their diff with ATF or 5 wt oil! I took the whole Diff apart before installing and it is amazingly simple: just worm gears and drive gears: nothing to wear.
I tried cleaning up some rough edges in the carrier with my carbide air tool and found that the material on all the parts was EXTREMELY hard! So I understand why Quaife is so confident about the reliability.

For this reason, I bought a Quaife for my 914 V8 which I run at Willow Springs. It DID cause a bit of understeer, but with the addition of a rear swaybar, it came right. The diff works GREAT and changed the car from SMOKING the inside wheel off corners and 1/2 way up the straights(in an expensive cloud) to just putting the power down.

I'm willing to live without the rear axle "lock-up" under braking as I never had it before...so I have to be a more precise driver.

The Diff in the 915 is the SAME as that in my 930 box, so I have personal experience with the model you would use. It was also pretty easy to set it up myself....All is GOOD!

I hope this helps....it's your decision.

Terry