Now maybe I got this all wrong but reading all about people throwing cars into the hedge and wiggling the rear ends out all over and the mention of slippy diffs preventing this as had me hovering over the keyboard too post this for a while.......

LSD's make the back end wiggle more ? Or have i got it wrong ?



A wheel is struggling for grip, the lsd gives it some grip (as such) this tends too give the car rear steering (presuming its rwd) I'm sure NsDev will confirm this as he most prob runs a locked diff which makes the problem even worse, imagine you get both rear wheels airborne, the rear lands on the left rear 1st, with an open diff all the power would go too the right wheel and you would carry on in a straight line, with a locked or LSD the left wheel would once it landed have drive and steer you too the right ?

This would be pretty much the same with wheel spin, if one wheel is spinning the other as little or no drive so you carry on in a straight line, a LSD gives it some power/drive and also give you rear wheel steering.

Maybe I got it wrong, but Ive always had the impression that LSD can bite back much more than open diffs, and yup i got a LSD on mine.

Discuss.

Having driven the formula student car a couple of times in anger, and that is fitted with a Quaife ATB, its seems that once you get into a slide with it if you put the power on and keep the front wheels straight then it automatically corrects itself as both rear wheels are trying to push forward the same amount.

It also seems to make it easier to do full on huge opposite lock powerslides and keep them under control.

I believe with an LSD it is easier to slide around if you want to, and when you do its more controllable.

Whether those things are true or not I dont know, but thats how it seems to me.

David

I was trying to figure out the engineering of spinning your car out on the straight.

The only senario I could come up with is if you had an open diff, and one wheel lost traction on a localised really slippy surface, the diff you dirct the power to the spinning wheel, which suddenly regained traction.....right turn Clyde

quote:

---

Originally posted by Jon Ison
Maybe I got it wrong, but Ive always had the impression that LSD can bite back much more than open diffs, and yup i got a LSD on mine.
Discuss.

---

"Having driven the formula student car a couple of times in anger, and that is fitted with a Quaife ATB, its seems that once you get into a slide with it if you put the power on and keep the front wheels straight then it automatically corrects itself as both rear wheels are trying to push forward the same amount."

This can only be true if both have the same amount of grip ?


"It also seems to make it easier to do full on huge opposite lock powerslides and keep them under control."

Thats why you can do donuts with an LSD, your getting power too the loaded outside wheel which on an open diif you cant.

"I believe with an LSD it is easier to slide around if you want to, and when you do its more controllable."

I thinks its far easier too provoke a slide with a LSD, not sure about control it, on the race track maybe but not a bumpy wet road.

"maybe if i'd had a standard diff originally i might have not spun due to losing traction on one wheel. "

Exactly, you lost grip on one wheel power went too the "non spinning but as grip wheel" and steered you off the road.



BTW not trying too provoke a full scale told you so argument hear, just dispel a few myths and maybe assist anyone thinking a LSD will make for a more stable car on the road.

Oh yes, maybe I should mention that that was on a perfectly dry and flat track. It will undoubtedly make a lot of difference if you start adding bumpy and slippery roads into it. The FS car is barely controllable in the wet (well its ok if you are gentle), but whether thats down to the LSD or not, I dont know.

I am only putting an open diff in the Locost, as I personally cant see the benefits of one in a road car. Other than being able to leave 11's everywhere instead of 1's

David

In my experience Jon you are dead right in principle.

An LSD equipped car is more "back endy" to drive, but is easier to feel what is happening and (for me, and this is only my "feel" not science) more predictable.

The big problem I have with non LSD equipped cars is corner exit wheelspin on the inside wheel (this is on tarmac not grass by the way!).

The LSD prevents this, usually by provoking a loss of grip on both rear wheels rather than one!!!

Whilst this is NOT a plus in terms of performance, you do know when it is going to happen (i.e. when you open the throttle!) whereas without the lsd, you wait for that horrible snatch as the inside wheel regrips, and you always have to keep an armful of lock ready for when it does.....which to a crap driver like me is not desirable!



On the grasser with a welded diff its all a bit different really, as you rarely stop wheelspinning. With an open diff you would lose a huge amount of corner speed as the inside wheel would just spin away all the time. As for handling, difficult to say as dirt is very different to tarmac, and the car is always sideways anyway.

quote:

---

Originally posted by Jon Ison

BTW not trying too provoke a full scale told you so argument hear, just dispel a few myths and maybe assist anyone thinking a LSD will make for a more stable car on the road.

---

quote:

---

Originally posted by Jon Ison
"Having driven the formula student car a couple of times in anger, and that is fitted with a Quaife ATB, its seems that once you get into a slide with it if you put the power on and keep the front wheels straight then it automatically corrects itself as both rear wheels are trying to push forward the same amount."

This can only be true if both have the same amount of grip ?


"It also seems to make it easier to do full on huge opposite lock powerslides and keep them under control."

Thats why you can do donuts with an LSD, your getting power too the loaded outside wheel which on an open diif you cant.

"I believe with an LSD it is easier to slide around if you want to, and when you do its more controllable."

I thinks its far easier too provoke a slide with a LSD, not sure about control it, on the race track maybe but not a bumpy wet road.

"maybe if i'd had a standard diff originally i might have not spun due to losing traction on one wheel. "

Exactly, you lost grip on one wheel power went too the "non spinning but as grip wheel" and steered you off the road.



BTW not trying too provoke a full scale told you so argument hear, just dispel a few myths and maybe assist anyone thinking a LSD will make for a more stable car on the road.

---

My two pennies worth having driven both in a number of different cars....

When pushing a LSD equipped car holds on for longer but when the back end starts to slide it snaps away, with an open diff as one wheel starts to break traction and the car slides away gently and you can more easily catch it.

However if you want the back out LSD's win every time as once you have caught the slide you can more easily balance on the throttle.

LSD's make it more of a drivers car.... but in many ways more dangerous as they can catch you out !

I also found that the old powerloc diffs with plates tend to snap in and throw you about, the viscous ones are far better.

Cheers Mark

I seem to remember a conversation about the merits/demerits of LSD's with someone far more knowledgable than me, and if i understood him correctly, LSD's become more of a handful in lighter cars when exiting corners, IIRC his view was LSD's were not necessary in a 7, and that sierra ones in particular are not overly suited to lightweight cars.
All the above may be bullshit BTW, or i may have misunderstood . Iv'e recently put a quaife ATB in mine, but not driven it yet to compare with the sierra one

Perhaps it depends on the type of LSD. iirc the Sierra type have a tendency to "snatch" and someone said this was due to the diff being set up for a much heavier car. Not sure if this is a "feature" of clutch-pack friction-plate LSD versus Torsen or viscous LSD.

The only vehicle I've had with an LSD was a big Aussie Ford Falcon V8 utility, and that had the most awesomely controllable power slides (think Vauxhall Monaro without the weight of most of the rear bodywork!)

As someone else mentioned, the ideal is to get the suspension to work correctly so the tyres stay planted over bumps, and you won't need to worry (as much) about spinning tyres.

Rally cars use LSD for better turn-in than a locked diff will allow.

[Edited on 9-2-06 by locost_bryan]

As you read this, keep in mind most of my experience is with heavy cars with a fair bit of horsepower (blessed excess) .

When you lose traction with an open diff in a straight line the vehicle will stay straight because the other rear tire is still planted. With a LSD both rear tires are spinning and it will kick out. Usually to the right due to the powertrain layout. Tires only have so much traction. If 100% of the tires "stiction" is used to try to keep the tires from spinning, there is 0% to keep it from sliding sideways.
If you are doing a smokeshow with LSD a single person can push the car sideways. Same goes for braking and cornering. If you use 100% of the stiction on braking (lock up) you have no stiction left to turn the vehicle and it goes whatever direction the inertia is going. Usually straight into the weeds.
I have found in the corners that open diffs can be NASTY to control if you have a lot of bodyroll. In a single powerslide its fine, but if you have to over-correct and create a fishtail happens is the spinning tire will switch from side to side as the weight transfers. It always spins the easiest tire. That can be a real handfull.
I had an open diff for a while in my camaro which could spin the tires pretty easy. If there was a little dust on the left tire and not the right the left tire would spin, then when there was no more dust the tire would catch and switch to the right tire spinning. In a straight line that would kick the back out about a foot w/o warning. This is in normal driving, not full throttle.
Long story short, a good LSD that has the correct amount of slippage for the vehicle is better than an open diff in every area.

Agree with the susspension set up comments, and maybe the wet bumpy road comment of mine was missleading in this area, all I was/am trying too do is dispell the myth that an LSD will prevent you from chucking your car into the hegde bottom, it is actually capable of chucking it in there for you, more so than an open diff.

I agree with all your comments above John, but one I have some reservations on. The bumpy wet road bit. This is nothing really to do with the LSD and everything to do with suspension setup.

Over-stiff springs and incorrect damper rates (which I would say most sevens suffer from) combined with an LSD will all reduce grip in those conditions. The thing is it's not the diff at fault but the suspension. This needs to keep the available grip at each wheel as equal as possible, which it won't with most of the spring rates I hear mentioned on here!


Keep the setup nice and soft, keep away from chav tuning ideas like:

Big wheels with low profile tyres (wreck grip on the road, especially on a car too light for the tyre design)

Stiffer springs than necessary (often necessitated by the above ride height issue which reduces geomatrical roll control)

Poor dampers/damper setup, remember damper rate is directly related to spring rate.

Syd,

Not sure you can Generalise

I think the problem with the 7's is there is TOO MUCH GENERALISATION

Each car should have its suspension set-up and balanced on its own merits, taking into account the wheel size, weight distribution, tyre size, what the purpose of use is etc. etc.

I know 13's are preferred, but plenty of people use 15's well. Some even risk 17's but these are cosmetically great but 'apparently - according to them' awful to drive with...

As for LSD - they are proven to work well with high powered cars, you just have to know how to use them

Sliding a car around with an LSD is completely different to an Open Diff. I personally prefer the LSD as it's more progressive, as for it making the backend come out quicker how can you tell? You swapping the diffs over? I'd look at tyre inflation and suspension set-up before blaming the poor old Lucy in the Sky of Diamonds

So to sum up - Balance is the name of the game

Just my observations - no personal attacks intended, no flaming wars please

[Edited on 9/2/06 by muzchap]

Ok, you do have to watch out when generalising, I will agree, but the setups employed by a LOT of sevens are just wrong, for any seven unless it's been filled with cement!

My constant bugbear is the rear ends of these cars. Especially live axle ones. The ratio of sprung to unsprung weight is awful on these, and really is the only major downside of the live axle setup. it means that the springs and dampers are CRITICAL, as slightly too stiff on either and traction is destroyed.

Likewise I hear of 175lb/inch rear springs being used on BEC's on the road........great for practising ice-racing but not very good at getting anywhere very quickly!

On a track you can concentrate on suspension settings which control geometry. On the UK highway, just maintaining some semblance of traction on our incredibly uneven roads is of much higher importance. Controlling the geometry is of little importance if the wheel has been bounced into the air by a bump, due to stiff springs, dampers and tyres.

To give you some idea, one of my other car related "interests" is with the Opel Manta Owners Club, where I repeatedly make a recommandation on car setup regarding springs and dampers.

The setup I recommend is (bearing in mind the manta weighs in at 1065kg ish):

400lb front springs

160lb rear springs

std rear antiroll bar in dry conditions, disconnect in wet.

std front antiroll bar, 2mm thicker with very sticky front tyres fitted

Bilstein competition dampers fitted all round (don't know the rates but from experiance I know that they work, unlike the others that I have tried which were supposedly "adjustable"!!)

Now I get ignored almost without exception, especially on the rear springs, as 160lb is the std rate and everybody insists on "lowered and uprated" springs for some reason!

It was therefore, brilliant to find a track-dayer with a bog-std manta GTE, who was willing to use my recommended setup, and then took it on track and was quicker than all of the "modified" cars there, despite his soft setup. The 16v cars were merrily spinning wheels up all over the place, while he just drove around them!

Great Post - full of useful information

Sometimes the 'manufacturer' knows best

Lumps of lead in the boot?

Cheers,

Murray

Heh heh probably of limited use to us locosters but decided the cobwebs needed clearing from my trumpet!

Dunno why I'm posting it, but here's the thread from the OMOC forum (just got to clear the last of the dust from the trumpet!!



""""""Author Topic
captkirkirkham


just to let anybody interested know how i have got on with trackdays in my 87' gte hatch. suspension:front, bilstein shocks, rally design 400lb springs. rear, bilstein shocks standard springs. poly bushes all round. brakes, front, carlton discs, vectra calipers, maxtorque pads,(rally design). rear, standard drums. wheels, 15'' OZ toyo proxes tyres.

went round cadwell park! wow, car felt great, wheels and tyres make abig differnce managed to embarass a bmw M coupe(321bhp)!. i know he couldn't have been giving it everything but he was quite surprised to see me up his ring in the twisty bits.
the car is just sooo much fun, obsene for what it has cost!
gearing not quite right, too big a gap btween 2nd and 3rd, managed to spin locking back wheels.
now just need a cage and racing seats and harnesses, oh another 100hp would be nice. forgot to say, brakes pretty good too, not much feel, too much travel but they did the job with no fade at all.

Mantastic
Rank - Senator





Hi,

don't know if you remember me, you bought a set of GTE wheels off me a good while ago and I gave you a bit of advice on the springs and dampers etc I think.

Take it they worked nicely then!!

Great to hear of another manta being used for the right thing!!!

Cheers,

Nat.

OMOC - 5716




sorry, meant to add, to reduce the brake padal travel, strip and re-assemble the rear brake shoe adjuster assemblies. They seize up and generally get crap with age. If they have seized then the pedal travel will get long. To check this, if you pull up the handbrake then press the pedal and the travel has shortened, the adjusters need tweaking.

As usual, Haynes manual says it all so I won't go into detail.

Cheers,

Nat.

OMOC - 5716


captkirkirkham
Rank - Rekord




hi nat, yes i remember, have you still got the mad peugeot 205? thanks for the advice. the only thing i am wondering about is the ride height. even though i put the lowered springs on the front it still seems excessively high, big gaps between wheel and arch. surely it would be beneficial to get it a bit lower, centre of gravity and all that? if so what are best springs to get. i know you said not to lower at rear but the number of very low mantas i saw at billing did make me wonder.


Mantastic
Rank - Senator





I wouldn't worry too much about the ride height. The centre of gravity is only a real issue if it is pulling the car over on it's roll axis. As long as the body roll isn't excessive then don't worry.

I would think the body roll will only become a serious issue if you put slicks on, but then brakes etc will become serious issues then as well!!!

Many (well, most) of the cars at billing were lowered for looks mainly.

If you lower a manta, you really need to alter the wishbone lengths to get the roll centre heights back where they need to be, i.e. lowering the car will not help roll control at all!! What most people confuse with good roll control is the use of much stiffer springs when lowering the car, these then reduce grip over bumps!

I would leave well along on the suspension now, and go for weight reduction, which can help the handling more than you think, replacing the glass in the hatch with perspex will help lower the centre of gravity a bit, as will fitting low mounted competition seats. Battery in the boot, or even better in a box in the rear footwell. Take out the heater box etc. All this will help performance (and be kinder to the brakes too, less to slow down!!)

I have sold the RWD Peugeot 205 now, I'm now building a Caterham copy (Stuart Taylor 7 chassis and panels) with another 16v vauxhall engine on throttle bodies again, hope to do a few trackdays with this, should be quite quick, 200hp and 550kg!!!

The autograssing has been going well too, got first in club and second in the east midlands league in class 9!

Cheers,

Nat.

OMOC - 5716




Oh yes, meant to add, I have a cage for a manta too. It's not great so you may not be interested. I don't think it is MSA approved as it only seems to be 2mm wall tubing not 2.5mm, but it is a full 6 point cage with rear diagonal, email me on n.seviour@ntlworld.com if you are interested.

OMOC - 5716


captkirkirkham
Rank - Rekord





well b***er me, been looking for a cage for ages, then two come along. went across to wales yesterday and got a cage from 'daishag', proper job.

not thought about moving the battery before, excellent idea.
i am in the process of trying to get some seats, have been doing some bidding on ebay. don,t suppose you know anybody who might be selling any?

caterham copy, mmmmmm nice, 200bhp even nicer!


Mantastic
Rank - Senator



The cage Daishag was selling was much better than the one I have, you did the right thing getting that one, it is a proper msa spec one.

Seats depend on how much you want to spend and how handy you are at making mounts for them. A handy place for contacts for this sort of thing is www.locostbuilders.co.uk the site where I get a lot of info for the kit car. Several people that post on this forum make seats in GRP/Kevlar.

Try Yorkshire Rally spares too www.yorkshirerallyspares.co.uk they usually have something laying about.

cheers,

Nat.

OMOC - 5716 """"""

.....just read it and realised I was plugging this site too!

A lot depends on the type of diff --- plate LSDs I don't like -- very nasty action in contrast I found Jack Knight pawl LSD very good on Imps --- gentle but definite action made the car handle a lot better on tight bumpy corners eg the Knockhill harpin of old.

I have read this thread and am now worried that I have the wrong diff.

I want a car that never gets the rear end out or if it does, it does do in a very gentle, progressive way that is easily caught and controlled.

I have a sierra viscous coupling LSD. on a few occasions when using large amounts of throttle in low gear, the rear end has started to come round. On a good dry road it doesn't happen but once or twice it has. Lifting off the throttle (I know its not the best way to solve it but I'm a big scaredy cat and it just happens) sees the tail go back through the straight ahead with one or two little shimmys and normal service is resumed.

Would I be better off with an open diff?

Whilst I wouldn't really want to rebuild, I wouldn't mind saving a bit of weight. I'd rather have the "safer" system of the two.

[Edited on 9-2-2006 by smart51]

If you want a car that will hang its tail out nicely on demand, without scaring you excessively, go for 13" wheels that aren't too wide. I have 13" x 5.5 wheels with 185/70 R 13 tyres (very old-fashioned!) and it's a pussycat in the corners.

I can hang the tail out when I want, I always have a fair idea when it's going to let go, and it's easy to recover when it does - see my post on greasy roads elsewhere.

I don't have the ultimate grip that wider, low-profile wheels & tyres may have, but I get far fewer 'ring-twitching moments'!

In other words - I'm with Syd on this one...

David

[Edited on 9/2/06 by David Jenkins]

Some really interesting points raised in this discussion. Maybe I can contribute a little?

Would it be possible when talking about your LSD seven to state what the LSD came from or was designed for?
Whether it came from Sierra or Escort, etc.
This will help others to judge the weight of the designed for application.

Just a thought!

quote:

---

Originally posted by David Jenkins
If you want a car that will hang its tail out nicely on demand, without scaring you excessively, go for 13" wheels that aren't too wide. I have 13" x 5.5 wheels with 185/70 R 13 tyres (very old-fashioned!) and it's a pussycat in the corners.

I can hang the tail out when I want, I always have a fair idea when it's going to let go, and it's easy to recover when it does - see my post on greasy roads elsewhere.

I don't have the ultimate grip that wider, low-profile wheels & tyres may have, but I get far fewer 'ring-twitching moments'!

In other words - I'm with Syd on this one...

David

[Edited on 9/2/06 by David Jenkins]

---

I actully think that LSD`s cause UNDERSTEER.

I have run my Minor with and without the Sierra viscous LSD.

With the LSD I was suffering a lot from power on understeer. My driving style was slow in and fast out (very safe way of doing it when learning a car and track). But when trying to power around a corner I suffered understeer. If I tuned out the understeer, by softening the front bar it then caused oversteer in high speed corners (not very good!!)

With my open diff I could power around the bends with a better balanced car at all speeds.

If I really provoked the power and steering I could get oversteer with both diffs, it was generally more controlable with the LSD.

As I got better at driving and carried more speed into the bends, the LSD became the preferred diff. I was going fast into the apex then powering out and releasing the car from the bend. In other words I would be taking the lock off as I was under power.

So in my experience the LSD was good as long as I did not put power with steering lock applied. I had to bring the power in and unwind the lock.

In general though the LSD will be more oversteery under large provocative applications of power, because both wheels are spinning. However if the car is set up and driven correctly the LSD will cause understeer when braking and when power is applied.

If anybody has difficulty with the LSD causing understeer then take it to extremes and think of a locked diff. With a locked diff the car always wants to go straight on because it is so difficult to turn the wheels at different speeds when they are connected.

John

LSDs do cause understeer, but a sierra viscous coupling LSD in normaly deactivated. That is, if neither wheel has lost grip then it acts like an open diff. Only if one wheel goes much faster than the other does the viscous coupling start to lock. It then tries to make both rear wheels turn at the same speed, more or less. This makes it harder to turn, provoking understeer. I guess in this sense, it turns oversteer into something more like a 4 wheel drift.

quote:

---

Originally posted by JB
I actully think that LSD`s cause UNDERSTEER.

I have run my Minor with and without the Sierra viscous LSD.

With the LSD I was suffering a lot from power on understeer. My driving style was slow in and fast out (very safe way of doing it when learning a car and track). But when trying to power around a corner I suffered understeer. If I tuned out the understeer, by softening the front bar it then caused oversteer in high speed corners (not very good!!)

With my open diff I could power around the bends with a better balanced car at all speeds.

If I really provoked the power and steering I could get oversteer with both diffs, it was generally more controlable with the LSD.

As I got better at driving and carried more speed into the bends, the LSD became the preferred diff. I was going fast into the apex then powering out and releasing the car from the bend. In other words I would be taking the lock off as I was under power.

So in my experience the LSD was good as long as I did not put power with steering lock applied. I had to bring the power in and unwind the lock.

In general though the LSD will be more oversteery under large provocative applications of power, because both wheels are spinning. However if the car is set up and driven correctly the LSD will cause understeer when braking and when power is applied.

If anybody has difficulty with the LSD causing understeer then take it to extremes and think of a locked diff. With a locked diff the car always wants to go straight on because it is so difficult to turn the wheels at different speeds when they are connected.

John

---

From my observations of comments made on here by various folks about the 'lively' handling of their newly-completed Locosts and of drivers in general I have drawn the two following conclusions:
1) Sometimes not enough attention is paid to getting a car set up properly. THis applies to all walks of life, motorsport included. A well set up car will always be easier to drive than a badly set up one. Junior Johnson, the notorious NASCAR driver come moonshine runner was quoted in an interview as saying he never ever user brute force to drive his cars as he set them up so they didn't need it, and he wwas a big chap who could have easily muscled cars around.
2) An awful lot of drivers (me included) really do not recognise where the limits of their abilities & talents are, and put themselves and their car into an unrecoverable situation all too easily. Testosterone is a pain in the arse sometimes!

Geez fellas, don't too many agree with me and make me think I got something right for once. The smaller and narrower tyres are, indeed, more foregiving and progressive leading to better 'feel'. 'Nuff said.

The diff thing is interesting. In particular, viscous diffs can be a big pia if made to work constantly. They don't get a chance to go open, and end up acting permanently solid. Locked for all intents and purposes.

Plate diffs can be set up to give near to no slip, or be near open, and anything in between. I like the genuine Torsen type diffs, because of the constant and very predictable behaviour, or so I'm told by those who I work with who use them.

Setup is THE most important thing.

I've got a few anecdotes, but the best was a Mustang in the 'states. I made a cfrp intake for it, 5.5lbs total. The original ali item near 65lbs! The driver said the car had more grunt, but was undriveable in the corners. When I asked about corner weight setup and springs, I got a blank reply. ( We'd taken 60lbs off the front axle.) Quick trip and some maths on the springs, and the car was constantly in the top 3. The manifold was then banned in the class, so back to the heavy ali thing. More maths, new springs and arb's, and no change in placings. Top 3 consistently. Previous to all this his best was a 5th.

So, it shows just how important setup is.

Syd.

The Torsen diff is the best in therory --- my only actual experience with it has been FWD as used by Rover on the turboed 820 and 620 :-).


However have you noticed a lot of the cars that have made a oneway trip into the boonies recently have't been Locosts.

Tyres also play a big part --- fitting over wide tyres on a light car for road use has big disadvantages -- bigger isn't always best.

Unlike a racer where tread compound gives break away progression on a road car particularly in cold weather it is to a large part l down to tread, the tyres available to Locoster were all designed for much heavier cars as a result the tread area of the tyre is not loaded to its design parameters.

[Edited on 10/2/06 by britishtrident]