Does an LSD increase torque steer?
Discussion
Ask here.
I think a few of the guys use them
http://www.turbominis.co.uk/forums/index.php
Although I know my turbocharged Mini torque steered like a b
d even with an open diff...never used a LSD in it
Suspension setup would play a big aprt also.
I think a few of the guys use them
http://www.turbominis.co.uk/forums/index.php
Although I know my turbocharged Mini torque steered like a b
d even with an open diff...never used a LSD in itSuspension setup would play a big aprt also.
Edited by stevieturbo on Wednesday 5th May 12:01
I swapped to a quaife ATB in a heavily tuned Maestro turbo and got a significant improvement in the torque steer. Not gone by any means but better. As I understand it, and it makes sense, the problem in the Maustro and other FWD cars is unequal length drive shafts but I/m not sure if this applies to a mini as I have never worked on one.
If you're getting torque steer it's indicative of sloppy suspension setup.
Anything which causes it to transfer a load unduly onto one wheel for starters and causes a positive feedback cycle where you get a weave is no good.
Stiffen up your bushes, run less KPO (wheel offset), run the car stiffer and lower so it is less liable to transfer weight slowly, you'll see this increases the rate of weave and then almost eliminates it. I went a step further and lowered mine until the driveshafts were flat, to negate any imbalance caused by different driveshaft angles (I suspect are very low).
I got rid of a lot of the weave this way.... most of it was caused by too much offset and too much slop. Work out where your slop is and perhaps alter the tow-out a nadge, ie give it a 1/8" more tow out so when you are booting it, the wheels will tend to pull into a straight line (ie not tow in).
I haven't tried it yet, but I've fitted a plate LSD to see me out of corners quicker. It will make it a beast to drive, but I gather a Quaife is a kinder animal. It may make the steering feel a bit less self-centering so perhaps it may be an idea to increase the castor angle to get more drag/feel, but again, all this tuning takes it away from being a nice granny mobile.
I wouldn't fit an LSD until grip out of corners becomes an issue.
It shouldn't influence torque steer that much, however, it will reduce the weave you get when one wheel loses a bit of traction (like over a drain cover) It will affect the steering to a degree. The more hardcore the LSD, the more hardcore the steering.
It's the price you pay for being FWD and fast.
Anything which causes it to transfer a load unduly onto one wheel for starters and causes a positive feedback cycle where you get a weave is no good.
Stiffen up your bushes, run less KPO (wheel offset), run the car stiffer and lower so it is less liable to transfer weight slowly, you'll see this increases the rate of weave and then almost eliminates it. I went a step further and lowered mine until the driveshafts were flat, to negate any imbalance caused by different driveshaft angles (I suspect are very low).
I got rid of a lot of the weave this way.... most of it was caused by too much offset and too much slop. Work out where your slop is and perhaps alter the tow-out a nadge, ie give it a 1/8" more tow out so when you are booting it, the wheels will tend to pull into a straight line (ie not tow in).
I haven't tried it yet, but I've fitted a plate LSD to see me out of corners quicker. It will make it a beast to drive, but I gather a Quaife is a kinder animal. It may make the steering feel a bit less self-centering so perhaps it may be an idea to increase the castor angle to get more drag/feel, but again, all this tuning takes it away from being a nice granny mobile.
I wouldn't fit an LSD until grip out of corners becomes an issue.
It shouldn't influence torque steer that much, however, it will reduce the weave you get when one wheel loses a bit of traction (like over a drain cover) It will affect the steering to a degree. The more hardcore the LSD, the more hardcore the steering.
It's the price you pay for being FWD and fast.
Tangent Police said:
If you're getting torque steer it's indicative of sloppy suspension setup.
Anything which causes it to transfer a load unduly onto one wheel for starters and causes a positive feedback cycle where you get a weave is no good.
Stiffen up your bushes, run less KPO (wheel offset), run the car stiffer and lower so it is less liable to transfer weight slowly, you'll see this increases the rate of weave and then almost eliminates it. I went a step further and lowered mine until the driveshafts were flat, to negate any imbalance caused by different driveshaft angles (I suspect are very low).
I got rid of a lot of the weave this way.... most of it was caused by too much offset and too much slop. Work out where your slop is and perhaps alter the tow-out a nadge, ie give it a 1/8" more tow out so when you are booting it, the wheels will tend to pull into a straight line (ie not tow in).
I haven't tried it yet, but I've fitted a plate LSD to see me out of corners quicker. It will make it a beast to drive, but I gather a Quaife is a kinder animal. It may make the steering feel a bit less self-centering so perhaps it may be an idea to increase the castor angle to get more drag/feel, but again, all this tuning takes it away from being a nice granny mobile.
I wouldn't fit an LSD until grip out of corners becomes an issue.
It shouldn't influence torque steer that much, however, it will reduce the weave you get when one wheel loses a bit of traction (like over a drain cover) It will affect the steering to a degree. The more hardcore the LSD, the more hardcore the steering.
It's the price you pay for being FWD and fast.
In my experience,albeit from rallying 30 years ago, using a plate diff on a Mini,(especially on loose surfaces )means a large steering wheel is required unless you're built like Arnie! It can be very tiring wrestling the steering on a long event. Just pray you don't get a driveshaft failure at an awkward moment,the results can be very expensive.Anything which causes it to transfer a load unduly onto one wheel for starters and causes a positive feedback cycle where you get a weave is no good.
Stiffen up your bushes, run less KPO (wheel offset), run the car stiffer and lower so it is less liable to transfer weight slowly, you'll see this increases the rate of weave and then almost eliminates it. I went a step further and lowered mine until the driveshafts were flat, to negate any imbalance caused by different driveshaft angles (I suspect are very low).
I got rid of a lot of the weave this way.... most of it was caused by too much offset and too much slop. Work out where your slop is and perhaps alter the tow-out a nadge, ie give it a 1/8" more tow out so when you are booting it, the wheels will tend to pull into a straight line (ie not tow in).
I haven't tried it yet, but I've fitted a plate LSD to see me out of corners quicker. It will make it a beast to drive, but I gather a Quaife is a kinder animal. It may make the steering feel a bit less self-centering so perhaps it may be an idea to increase the castor angle to get more drag/feel, but again, all this tuning takes it away from being a nice granny mobile.
I wouldn't fit an LSD until grip out of corners becomes an issue.
It shouldn't influence torque steer that much, however, it will reduce the weave you get when one wheel loses a bit of traction (like over a drain cover) It will affect the steering to a degree. The more hardcore the LSD, the more hardcore the steering.
It's the price you pay for being FWD and fast.
stevieturbo said:
Torque steer has nothing to do with driveshaft length.
If you set your car up dead right, you always get a pull to the right first, don't you? (assuming you are on the flat, dead ahead)(Left wheel has the short shaft) Gets off the line quicker and the car tips onto that side which digs in, until the reaction chucks it on the other wheel which then gives you less of a weave. The weave right caused by the left wheel digging in is caused by the longer shaft flexing instead of digging in straight away. All you need is a small amount of difference for the left wheel to get the upper hand.
I've had that in all my minis. If you rigged an equal length kit, it would still do it, but with no preference as to which way.
Anyway, if you can't drive with a bit of torque steer, you shouldn't be using a car that needs an LSD.
I gather plate diffs are particularly arduous at low speeds. Big steering wheel is definately the go.
Edited by Tangent Police on Wednesday 5th May 20:34
stevieturbo said:
So do you think that a different length shaft somehow changes the amount of torque at the wheel ??
No chance.
Are you aware of the amount of twist that each shaft has relative to each other? An unstable setup which is prone to positive feedback (like sloppy bushes) only needs the tiniest difference to upset it. Get in any mini and see that it pulls to the right. No chance.
The shafts actually deform/rotate a fair amount, even big ones like landrover shafts. All you need is the weight to transfer momentarily onto one wheel a nadge more and then the cornering effect weights that wheel up and off you go. Then your suspension reacts and chucks it onto the other wheel, etc.
Watch it pull right everytime.
Can you explain if this is not the initial factor, what causes the initial inbalance? A solution would be running shafts with an equal torque deformation. Ie a fat long one. That would be the test.
Edited by Tangent Police on Wednesday 5th May 22:14
Tangent Police said:
stevieturbo said:
So do you think that a different length shaft somehow changes the amount of torque at the wheel ??
No chance.
Are you aware of the amount of twist that each shaft has relative to each other? An unstable setup which is prone to positive feedback (like sloppy bushes) only needs the tiniest difference to upset it. Get in any mini and see that it pulls to the right. No chance.
The shafts actually deform/rotate a fair amount, even big ones like landrover shafts. All you need is the weight to transfer momentarily onto one wheel a nadge more and then the cornering effect weights that wheel up and off you go. Then your suspension reacts and chucks it onto the other wheel, etc.
Watch it pull right everytime.
Can you explain if this is not the initial factor, what causes the initial inbalance? A solution would be running shafts with an equal torque deformation. Ie a fat long one. That would be the test.
Edited by Tangent Police on Wednesday 5th May 22:14
By your reckoning....if a car had equal length shafts it would have no torque steer. That is of course nonsense.
Even cars with the intermediate shaft so that both shafts are the same length/angle etc can still suffer from torque steer if they have enough power
So that throws that theory out the window.
Traction available at each tyre, suspencion geometry, tracking etc will all play a big part though. As will a diff.
In some respects an ATB style diff should be the worst possible thing for torque steer, as it will continually switch drive from one wheel to the other when traction is lost. However that isnt the case.
If you apply 100lbft to a 6" extension bar....the other end still see's 100lbft.
Likewise if you apply 100lbft to a 24" long extension....does torque at the other end get any less ?
I'd like to see the maths calculation to show how it wouldnt be the case ? Ive never seen a driveshaft so soft and flexible that it is twisting so much as to not apply all the torque from the diff, to the wheel.
Hell. Even on a Subaru, which has as close to equal length front shafts as you could get....with enough power, you can get a lot of torque steer.
Edited by stevieturbo on Thursday 6th May 00:18
The bottom line is that we can both have our opinions and the only way to truly prove it is by testing.
Surely the true test will be someone using a JK/KAD superduper equal length driveshaft kit. I assume that's why they make it.
Why do minis always pull to the right then?
(the bottom line is that I'd rather react to the pull, than bugger about with equal length shafts on an old car)
Surely the true test will be someone using a JK/KAD superduper equal length driveshaft kit. I assume that's why they make it.
Why do minis always pull to the right then?
(the bottom line is that I'd rather react to the pull, than bugger about with equal length shafts on an old car)
Stevieturbo is correct.
In addition tyres can also contribute to torque steer just by their construction.
The LSD won't contribute to or fix torque steer.
The LSD will enable you to get a lot more traction when one driven wheel exceeds it's torque drive capability by still allowing the other to provide some drive.
Different designs have different characteristics, but if traction in these situations is a problem generally it's a benefit.
They are not a cure-all though, and cannot overcome poor tyres, poor geometry, poor design or poor driving.
In addition tyres can also contribute to torque steer just by their construction.
The LSD won't contribute to or fix torque steer.
The LSD will enable you to get a lot more traction when one driven wheel exceeds it's torque drive capability by still allowing the other to provide some drive.
Different designs have different characteristics, but if traction in these situations is a problem generally it's a benefit.
They are not a cure-all though, and cannot overcome poor tyres, poor geometry, poor design or poor driving.
stevieturbo said:
Torque steer has nothing to do with driveshaft length.
Rubbish, it is very well known and well documented to be a major contributor to torque steer, if not the major contributor.http://www.mscsoftware.com/support/library/conf/ad...
http://books.google.co.uk/books?id=PSZYeTXR8awC&am...
http://www.infrastructure.gov.au/roads/vehicle_reg...
There are also some very good SAE papers on the subject
stevieturbo said:
So do you think that a different length shaft somehow changes the amount of torque at the wheel ??
No chance.
No, what it changes is when it arrives at the wheel. The longer shaft winds up and bananas, delaying the torque arrival, the shorter one less so. When it springs back you tend to make things worse with the over correction put in to keep it straight, it's all downhill from there and you often end up letting off, straightening and trying again.No chance.
The Cooper S Works that PH ran as a long termer had a factory mechanical LSD (which I believe was quaife-type) and I cannot recommend it highly enough. The car was running ~210bhp but had no significant problems with torque steer and the way you could get on the power in a corner was phenomenal, it would tuck in and tighten it's line when you got on the gas (almost like a RWD) rather than trying to wash out like every other FWD car I've driven.
fatjon said:
stevieturbo said:
So do you think that a different length shaft somehow changes the amount of torque at the wheel ??
No chance.
No, what it changes is when it arrives at the wheel. The longer shaft winds up and bananas, delaying the torque arrival, the shorter one less so. When it springs back you tend to make things worse with the over correction put in to keep it straight, it's all downhill from there and you often end up letting off, straightening and trying again.No chance.
And again....show me a fwd car with these magical equal length setups that doesnt suffer from torque steer when they have some power.
The bottom line is, they ALL still have torque steer.
So clearly these equal length shafts havent done much at all.
If the OP wants to read an authoritative paper on the subject instead of reading ill informed rubbish go to the SAE website and download SAE paper 2007-01-3656. It is well researched, presented by acknowledged industry experts and peer reviewed. It is also quite easy reading which is an unusual bonsu for an SAE paper.
Having had direct practical experience of trying to lay down 400+ BHP in a FWD car I did considerable research into the subject including a lot of reading and learning before spouting. Sorry I can't post a copy as it is copyright but it's change out of tenner to get your own. It does not cover any advantages of diff types on the problem but a little thought on the subject and a mental picture of how the problem occurs does seem to agree with my "feeling" that the ATB diff did help significantly. There are some suggested methods on minimising the problem but since it's mainly a paper for car manufacturers egg head departments the solutions are not terribly practical for retro fitting. One of the simpler ones is to add a second joint to the longer shaft which reduces the banana component but not so much the twist component, at least so far as I can picture the physics of it. Again, no idea how much of this applies to a Mini layout as it's not one I have worked on, although I have one coming at the weekend for a 1293 turbo conversion in conjunction with a friend of mine who just loves them.
http://www.sae.org/technical/papers/2007-01-3656
Having had direct practical experience of trying to lay down 400+ BHP in a FWD car I did considerable research into the subject including a lot of reading and learning before spouting. Sorry I can't post a copy as it is copyright but it's change out of tenner to get your own. It does not cover any advantages of diff types on the problem but a little thought on the subject and a mental picture of how the problem occurs does seem to agree with my "feeling" that the ATB diff did help significantly. There are some suggested methods on minimising the problem but since it's mainly a paper for car manufacturers egg head departments the solutions are not terribly practical for retro fitting. One of the simpler ones is to add a second joint to the longer shaft which reduces the banana component but not so much the twist component, at least so far as I can picture the physics of it. Again, no idea how much of this applies to a Mini layout as it's not one I have worked on, although I have one coming at the weekend for a 1293 turbo conversion in conjunction with a friend of mine who just loves them.
http://www.sae.org/technical/papers/2007-01-3656
fatjon said:
stevieturbo said:
Torque steer has nothing to do with driveshaft length.
Rubbish, it is very well known and well documented to be a major contributor to torque steer, if not the major contributor.ks.Why do powerful minis (the proper ones) suffer from torque steer when they have very nearly equal length driveshafts? Why does my current car suffer from torque steer when it has equal length driveshafts and a very heavy duty jackshaft?
Driveshaft lengths probably have the least impact on torque steer, provided they aren't ridiculously flimsy. Suspension compliance and e.g. scrub radius are vastly more dominant effects.
Edited by Mr2Mike on Thursday 6th May 13:45
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