Helical lsd under braking

[xu5]

Do torque biasing helical limited slip differentials, like Quaife and the like work under braking, so would increase traction under braking and delay one wheel lock up? FWD in this case.

Edited by xu5 on Friday 30th October 10:04

[GreenV8S]

I wouldn't expect them to. They're activated by drive train torque so would not normally come into play during braking. (Friction plate LSDs similarly tend to have some friction added by ramps and only the friction resulting from preload would be effective during braking.

[Boosted LS1]

They are torque biasing but only while both wheels have some grip. With zero grip on one wheel there won't be torque transfer. Interesting question OP. I wonder if grip just comes down to the tyres whilst braking. I need to thunk for a moment :-)

[xu5]

I was also under the impression that the torque biasing only came into effect under "positive" torque from the engine. But reading Quaife's marketing bumph they say it also helps under heavy braking. I am just trying to get my head round it.
I can kind of see how it might.....kind of....
I guess with a helical lsd it may not matter if it is accelerative or declarative torque it would still operate the same? Where as a plated diff can be set up to operate differently in either load?

Edited by xu5 on Friday 30th October 17:39

Edited by xu5 on Friday 30th October 17:40

[xu5]

Just bumping this in case anyone has further input.
My car does now have a torque biasing diff fitted and I can't say I notice it doing anything under braking, although I don't often brake very heavily. ABS still seems to come on under roughly the same conditions.

[tapkaJohnD]

Boosted LS1 said:

They are torque biasing but only while both wheels have some grip. With zero grip on one wheel there won't be torque transfer. Interesting question OP. I wonder if grip just comes down to the tyres whilst braking. I need to thunk for a moment :-)

I have a Quaife ATB. Some years ago I was at Le Mans, and broke a half shaft, where it was enclosed in the wheel bearing. I didn't know, at first, as drive continued, with torque transferred to the opposite wheel. But driving home, I could only go slower and slower, until I had to call RAC Rescue, leave the car and go home with friends.

I presume that remaining friction between the broken ends provided the 'grip' to enable the transfer, and as they wore away that transfer was less and less. Afterwards, Quaife pronounced the ATB completely unworn!
John

[stevieturbo]

tapkaJohnD said:

I have a Quaife ATB. Some years ago I was at Le Mans, and broke a half shaft, where it was enclosed in the wheel bearing. I didn't know, at first, as drive continued, with torque transferred to the opposite wheel. But driving home, I could only go slower and slower, until I had to call RAC Rescue, leave the car and go home with friends.

I presume that remaining friction between the broken ends provided the 'grip' to enable the transfer, and as they wore away that transfer was less and less. Afterwards, Quaife pronounced the ATB completely unworn!
John

Without friction, an ATB cannot pass drive from one side to the other. A completely unloaded side like you suggest should result in pretty much no drive at all

Wavetrac and possibly some others claim their ATB with internal friction plates allow drive to continue even with an unloaded wheel, as drive would still be biased towards the one with grip.

I can safely say though that my Wavetrac will absolutely allow one wheel to spin quite easily, and have many logs to prove it. So I'd question their claims.
They also claimed I could get uprated steel shims in lieu of the standard carbon for even more friction......until of course the unit was already purchased and arrived with spare carbon shims, because they better steel ones were not available for my model.

Pretty piss poor service.

That said, the actual diff unit itself is a very nice piece and of good quality. But it will spin one wheel.

[b14]

stevieturbo said:

Without friction, an ATB cannot pass drive from one side to the other. A completely unloaded side like you suggest should result in pretty much no drive at all

Wavetrac and possibly some others claim their ATB with internal friction plates allow drive to continue even with an unloaded wheel, as drive would still be biased towards the one with grip.

I can safely say though that my Wavetrac will absolutely allow one wheel to spin quite easily, and have many logs to prove it. So I'd question their claims.
They also claimed I could get uprated steel shims in lieu of the standard carbon for even more friction......until of course the unit was already purchased and arrived with spare carbon shims, because they better steel ones were not available for my model.

Pretty piss poor service.

That said, the actual diff unit itself is a very nice piece and of good quality. But it will spin one wheel.

Interesting - are you effectively saying that it doesn't lock in all scenarios? I did some research before fitting the LSD to my car and in the end wanted the more established Quaife, which I don't regret, sounds like might have been the best choice. Wavetrac is sold as being superior to Quaife as it locks in all conditions including when one wheel is off the ground, which nearly sold it to me.

[stevieturbo]

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