Castor/Camber Angles.
Discussion
We have fitted a LSD to our 1380 sprint Mini this season which has resulted in significant weaving on the straight especially off the start line on cold Miglia slicks.
Front camber is 1.5 degree neg. and castor angle is 5 degrees. Would an increase in castor angle to around 7 degrees, or more , reduce the weaving or should I look elsewhere? Or do we just live with it as it does not appear to effect performance?
Front camber is 1.5 degree neg. and castor angle is 5 degrees. Would an increase in castor angle to around 7 degrees, or more , reduce the weaving or should I look elsewhere? Or do we just live with it as it does not appear to effect performance?
Increasing the castor will result in increased self centreing of the steering so I can appreciate why you are heading in this direction. It will load the steering up and make it heavier, running 7degrees+ of castor is not uncommon on the circuit cars.
Fitting an LSD exaggerates the Long/Short side driveshaft set-up that the Mini has as standard. Unequal length driveshafts will always give you some torque steer issues. I think JKD did a diff/diff cover set up whereby you ran two equal length (short) driveshafts and if you really want arrow straight traction on cold slicks, this is where I'd be looking. It'll come at price tho'.
Failing that, get down the gym and build those biceps up...
Fitting an LSD exaggerates the Long/Short side driveshaft set-up that the Mini has as standard. Unequal length driveshafts will always give you some torque steer issues. I think JKD did a diff/diff cover set up whereby you ran two equal length (short) driveshafts and if you really want arrow straight traction on cold slicks, this is where I'd be looking. It'll come at price tho'.
Failing that, get down the gym and build those biceps up...
Not really sure about the equal length driveshaft thing. I assume what happens is that the longer shaft is looser and winds up, throwing the car onto the short shaft wheel which then grips more and then you get a weave set up when it throws it back onto the other wheel. The LSD would prevent it unloading through the diff and so make the problem more marked. The question is how can you set the suspension up to minimise this influence.
The answer to that is to get it low, a lower roll centre will speed up the frequency of "wobble" hopefully to a point where it doesn't have time to react. The same goes for upping the tyre pressures a bit and perhaps running the shocks stiffer. I'd also say that having more offset would minimise the weaving. However, it will fight the steering a lot so you'll have to hang on. Fatter shafts will be a lot cheaper than having a JKD equal length shaft setup.
This is very interesting as I plan to fit an LSD to mine but am allready running with the logic that I don't want the steering to be ridiculous. I reckon getting used to it is probably a good idea!
The answer to that is to get it low, a lower roll centre will speed up the frequency of "wobble" hopefully to a point where it doesn't have time to react. The same goes for upping the tyre pressures a bit and perhaps running the shocks stiffer. I'd also say that having more offset would minimise the weaving. However, it will fight the steering a lot so you'll have to hang on. Fatter shafts will be a lot cheaper than having a JKD equal length shaft setup.
This is very interesting as I plan to fit an LSD to mine but am allready running with the logic that I don't want the steering to be ridiculous. I reckon getting used to it is probably a good idea!
It is possible that it just needs getting used to. They do tend to pull you from one side then the other, always found it quite alarming on a mates hill climber especially testing on his drive over cattle grids etc(well not his drive, it belongs to the national trust and its 1/2 mile long!)
Didnt seem so much of a problem when actually hillclimbing in it at an event, you'd just floor it and hang on.
Didnt seem so much of a problem when actually hillclimbing in it at an event, you'd just floor it and hang on.
I have never managed to get to grips with LSD's in Minis. They are, I'm sure, very necessary for hill-climb and circuit cars, but really not much use for a rally car or a fast road car.
My old friend Russell Brookes who did the RAC Rally in a Mini a few years ago reckoned that having an LSD cost him many minutes and my son did the Ypres Historic Rally as a co-driver in a Cooper 'S' and went into a ditch because once the right hand wheels went onto the grass on a tightening left-hander, application of power just made the wheels still on the tarmc grip and the car steered right, straight into the ditch. In my car, on the very same bend the next year, I just lifted off a bit to get some oversteer, then banged the power back on with the outside wheels still a bit on the verge.
LSD's are very unforgiving if you get it a bit wrong, especially in the wet. It takes a lot of nerve to put full power on in a tightening bend if your entry speed is slightly high. Without an LSD you may spin, but with one you'll understeer off. They completely transform the handling characterists of the little car, adversly in the opinion of many.
Just be sure you're fitting one for the right reasons is my advice, for what it's worth.
My old friend Russell Brookes who did the RAC Rally in a Mini a few years ago reckoned that having an LSD cost him many minutes and my son did the Ypres Historic Rally as a co-driver in a Cooper 'S' and went into a ditch because once the right hand wheels went onto the grass on a tightening left-hander, application of power just made the wheels still on the tarmc grip and the car steered right, straight into the ditch. In my car, on the very same bend the next year, I just lifted off a bit to get some oversteer, then banged the power back on with the outside wheels still a bit on the verge.
LSD's are very unforgiving if you get it a bit wrong, especially in the wet. It takes a lot of nerve to put full power on in a tightening bend if your entry speed is slightly high. Without an LSD you may spin, but with one you'll understeer off. They completely transform the handling characterists of the little car, adversly in the opinion of many.
Just be sure you're fitting one for the right reasons is my advice, for what it's worth.
Hmmmm, this is interesting. My mini is nothing like a road car really, I run the minimum offset to keep the steering as loose as possible but otherwise it's set up to grip as much as possible. I found that with my last full beans engine, on very fast twisty stuff and on uphill corners, I'm spinning one wheel too much. Everytime, I think "If that wasn't spinning, I'd be up there now" and use the usual throttle feathering, etc. What I'm looking for is something I can hang onto more and despite heavy steering, go faster. One of the snags with an LSD is that the information is so different on whether they are any good or not. I suppose the only way to go is to try. But I doubt that there are any LSD'd minis like mine in Cornwall. I'd set mine weak (40lbs). I don't generally find myself on loose stuff too much and as a rule of thumb, driving in lanes with loose gravel/mud/leaves, I tend to take it easier to avoid stuffing the car.
Trickey seems to say that an LSD can actually help do really tight corners (apart from you need mega arms) and a few other people have said it transforms the car. My whole point of the mini is twisty stuff, not going 120mph on a dual carriageway. So, if an LSD helps that, great, if it doesn't, not interested. As they say, if you can't compensate for an LSD's bad manners, you shouldn't be behind the wheel of a car which needs one. Hmmmmm.
Trickey seems to say that an LSD can actually help do really tight corners (apart from you need mega arms) and a few other people have said it transforms the car. My whole point of the mini is twisty stuff, not going 120mph on a dual carriageway. So, if an LSD helps that, great, if it doesn't, not interested. As they say, if you can't compensate for an LSD's bad manners, you shouldn't be behind the wheel of a car which needs one. Hmmmmm.
i ran a quaiffe 'lady diff' in my road car, but took it out when i swopped the diff ratio as i didnt feel that i drove the car hard enough to warrent it tbh.
on the other hand i couldnt imagine driving my racer on the limit without a lsd.
the think to remember with lsds is that diferant makes have differant affects on handeling, so one persons opinions dont really offer a 100% answer as to what they are like. many off them can be adjusted to offer differant torques and ramp angles, all which makes them work in different ways.
i dont think that weaving is a sign of a lsd problem, more likley its a suspension problem.
i also dont think that the equal length shafts are much more than a gimmick, ive seen a well thought out letter somewhere explaing that they make little or no differance
on the other hand i couldnt imagine driving my racer on the limit without a lsd.
the think to remember with lsds is that diferant makes have differant affects on handeling, so one persons opinions dont really offer a 100% answer as to what they are like. many off them can be adjusted to offer differant torques and ramp angles, all which makes them work in different ways.
i dont think that weaving is a sign of a lsd problem, more likley its a suspension problem.
i also dont think that the equal length shafts are much more than a gimmick, ive seen a well thought out letter somewhere explaing that they make little or no differance
Just a quick word on the un-equal length driveshafts. It's not the length itself that causes the issue. It's the different CV joint angles that the lengths cause. As one tightens up it drags, thus causing the steering affect.
Also, an lsd will affect the handling, but as to wether that's good or bad depends upon what you like. Some prefer it, some can appreciate the benefits, but just can't get on with the other affects. The gear types are supposed to be a bit "softer" but I've not driven one so can't say what they're like compared to a plate type.
Also, an lsd will affect the handling, but as to wether that's good or bad depends upon what you like. Some prefer it, some can appreciate the benefits, but just can't get on with the other affects. The gear types are supposed to be a bit "softer" but I've not driven one so can't say what they're like compared to a plate type.
Thinking about the physics involved, it doesn't bear any relation to the driveshaft angles. I have lowered mine until the wheels are concentric within the arches. At the front, this means the shafts are just about flat. It weaves under accelleration just like the others do. I think it's about weight transfer onto wheels which are trying to slip, the first wheel to break (irregularities in the surface, balance of the car) causes the other wheel to grip, etc, etc. So, I'd say it was more about getting your ride height, stiffness, tyre tread, etc sorted.
Without having a massive degrade into the physics involved, I think equal length shafts are bullshit. There will be a SMALL influence due to the differences in "twist" and CV angle, but putting them into context with the bigger factors, it strikes me as a waste of money. Build 2 identical cars (apart from driveshafts) and drive them on the same piece of track and I reckon the difference will be minimal. To quote Clarkson "If it makes a blind bit of difference, I will eat my hair"
Without having a massive degrade into the physics involved, I think equal length shafts are bullshit. There will be a SMALL influence due to the differences in "twist" and CV angle, but putting them into context with the bigger factors, it strikes me as a waste of money. Build 2 identical cars (apart from driveshafts) and drive them on the same piece of track and I reckon the difference will be minimal. To quote Clarkson "If it makes a blind bit of difference, I will eat my hair"
i had a conversation with a transmition designer a while ago, he ran the dias and lengths through his programs, and came back with a figure of twist fo the long verses the short,,i suggested he experimented with diamaters untill hre found how much thicker the long shaft had to be before it had the same twist characteristics as th short, it was something like 1 or 2 mm increase,
i have never suffered torque steer in my cars, one of them had little torque but the other most certainly did,.
carl
i have never suffered torque steer in my cars, one of them had little torque but the other most certainly did,.
carl
Cara Jynwyth said:
Without having a massive degrade into the physics involved, I think equal length shafts are bullshit. There will be a SMALL influence due to the differences in "twist" and CV angle, but putting them into context with the bigger factors, it strikes me as a waste of money. Build 2 identical cars (apart from driveshafts) and drive them on the same piece of track and I reckon the difference will be minimal. To quote Clarkson "If it makes a blind bit of difference, I will eat my hair"
So why do many manufacturers now utilise a two part driveshaft with an extra support bearing on the long side if it makes no difference? I'm sure that's an expense they would be only too happy to remove.Mr2Mike said:
Cara Jynwyth said:
Without having a massive degrade into the physics involved, I think equal length shafts are bullshit. There will be a SMALL influence due to the differences in "twist" and CV angle, but putting them into context with the bigger factors, it strikes me as a waste of money. Build 2 identical cars (apart from driveshafts) and drive them on the same piece of track and I reckon the difference will be minimal. To quote Clarkson "If it makes a blind bit of difference, I will eat my hair"
So why do many manufacturers now utilise a two part driveshaft with an extra support bearing on the long side if it makes no difference? I'm sure that's an expense they would be only too happy to remove.Vehicle manufacturers try wherever possible to have equal unsupported lengths, My Puma has a support bearing on the "long" shaft and the Outer portion of the longer driveshaft is the same part No. as the short side shaft
Edited by FWDRacer on Monday 2nd July 15:20
I think the point Carl was making is that the effect is negligible on a mini. Yes, many modern cars have these 'equal' length shafts, but the also have the gear box hung on the side of the engine meaning one shaft would be 3 times the length of the other, not a few inches longer.
The mini has more fundamental limitations within its suspension geometry which contribute to its interesting handling, what you need is a very good setup.
Having said that, I do run equal length shafts
i just don't think it makes much difference.
The mini has more fundamental limitations within its suspension geometry which contribute to its interesting handling, what you need is a very good setup.
Having said that, I do run equal length shafts
i just don't think it makes much difference. Maybe the lsd magnifies any pulling caused by different drive shaft lengths.
The nastiest Mini I've ever had the misfortune to drive on the road was an ex-works Mini Clubman 1330 with an 8-port head, 649 cam, twin Webers, a tight LSD and a close-ratio box. It was on Dunlop 'green-spot' racing tyres. I was asked to evaluate what configuration changes could be made to make it driveable as the person in whose keeping it was reckoned it had an engine problem. I drove it down the road and it was misfiring and had mega-heavy steering. My buddy said the engine was sick, but I persevered, gave it a load of throttle and, at about 5500, it all came together. It pulled all over the road, didn't handle and when I got to a roundabout it took both hands to put the necessary lock on in 1st gear at 5000 rpm. On a track it might have been great with the revs over 5500 at all times, but for anything else it was useless. In fact it was bloody dangerous. The solution was a replacement engine with a 276 cam, a 'nice' 5-port head, twin 1.5" SU's, 10.5:1 c.r. and a standard gearbox and 3.76 diff. That made it very nice to drive and still quick enough for road use.
The nastiest Mini I've ever had the misfortune to drive on the road was an ex-works Mini Clubman 1330 with an 8-port head, 649 cam, twin Webers, a tight LSD and a close-ratio box. It was on Dunlop 'green-spot' racing tyres. I was asked to evaluate what configuration changes could be made to make it driveable as the person in whose keeping it was reckoned it had an engine problem. I drove it down the road and it was misfiring and had mega-heavy steering. My buddy said the engine was sick, but I persevered, gave it a load of throttle and, at about 5500, it all came together. It pulled all over the road, didn't handle and when I got to a roundabout it took both hands to put the necessary lock on in 1st gear at 5000 rpm. On a track it might have been great with the revs over 5500 at all times, but for anything else it was useless. In fact it was bloody dangerous. The solution was a replacement engine with a 276 cam, a 'nice' 5-port head, twin 1.5" SU's, 10.5:1 c.r. and a standard gearbox and 3.76 diff. That made it very nice to drive and still quick enough for road use.
pete
i bet that old ex works thing had a old cam and pawl type lsd fitted, they where crap and worked by winding them selves up - with the resultant weaving, driving on mud would let the wheels spin and sort its self out. the modern plate type diffs dont really show this sort of problem - mine has a full race one fitted and bar the slight 'tugging' feeling as it grips its not really noticable - bar at low speed turnings where you can hear (and feel) it snapping and cracking. i wouldnt want to drive it as a everyday car as it really takes a bit of heaving until its rolling and the castor and engine power lightens the steering up.
this is why a lot of the really hi-po minis now run the electric power steering kits - this lets the driver dare take one hand off the wheel to change gear, due to the diffs being so 'tight'. a mate of mine designed the kit after finding that he was unable to undo the seatbelts after a 20 min stage due to the effort of holding onto the wheel! - this was due to 160 bhp in the forests rather than a weaving problem!
i bet that old ex works thing had a old cam and pawl type lsd fitted, they where crap and worked by winding them selves up - with the resultant weaving, driving on mud would let the wheels spin and sort its self out. the modern plate type diffs dont really show this sort of problem - mine has a full race one fitted and bar the slight 'tugging' feeling as it grips its not really noticable - bar at low speed turnings where you can hear (and feel) it snapping and cracking. i wouldnt want to drive it as a everyday car as it really takes a bit of heaving until its rolling and the castor and engine power lightens the steering up.
this is why a lot of the really hi-po minis now run the electric power steering kits - this lets the driver dare take one hand off the wheel to change gear, due to the diffs being so 'tight'. a mate of mine designed the kit after finding that he was unable to undo the seatbelts after a 20 min stage due to the effort of holding onto the wheel! - this was due to 160 bhp in the forests rather than a weaving problem!
You are quite right Rich, it was an early Salisbury type, or so I believe.
I also drove Peter Horsburgh's rally car - the one which got stolen last Dec - at a group rally car test day. He had a 649, an lsd, a Weber and a 3.9 final drive. On the 1/4 mile drag his car was quickest, but on the more twisty handling course, mine was a good 2 seconds quicker than his, even when he drove mine. I really couldn't get to grips with his with the lsd, nor with Sid Ormerods similar car when I drove that on tarmac. Pete Horsburgh was so impressed with the 'friendly' handling of mine that he took my spec and re-built his exactly the same (286 cam, 3.9 diff, 11:1 c.r, etc). On the next event our times were really very similar and in a straight line the cars were identical.
Personally I wouldn't use an lsd in a rally car, even on tarmac, but for racing and, probably, hill-climbing I'm sure they are a 'must'. Off the line an lsd is just wonderful and when I wa taking some 0-60 times in my car the wheelspin was the factor having most effect, not the power or gearing (I got it to an average of 7.5 seconds).
I also drove Peter Horsburgh's rally car - the one which got stolen last Dec - at a group rally car test day. He had a 649, an lsd, a Weber and a 3.9 final drive. On the 1/4 mile drag his car was quickest, but on the more twisty handling course, mine was a good 2 seconds quicker than his, even when he drove mine. I really couldn't get to grips with his with the lsd, nor with Sid Ormerods similar car when I drove that on tarmac. Pete Horsburgh was so impressed with the 'friendly' handling of mine that he took my spec and re-built his exactly the same (286 cam, 3.9 diff, 11:1 c.r, etc). On the next event our times were really very similar and in a straight line the cars were identical.
Personally I wouldn't use an lsd in a rally car, even on tarmac, but for racing and, probably, hill-climbing I'm sure they are a 'must'. Off the line an lsd is just wonderful and when I wa taking some 0-60 times in my car the wheelspin was the factor having most effect, not the power or gearing (I got it to an average of 7.5 seconds).
I ran a Salisbury plate diff in my rallycross mini for years without any real problems apart from screwing the splines off output shafts. Even using sticky A2 Avons on 8" wheels, weaving wasn't a problem, once everything was WARM.
Biceps and press ups went hand in hand though!
Regards
Chris
Biceps and press ups went hand in hand though!
Regards
Chris
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