To LSD or not ?
Discussion
Ah but a Quaiffe isn't a limited slip differential..............................................
I have a plate style LSD fitted by someone who knows how to set them up for a Seven and it has transformed the car, so I would recommend the upgrade. I know a fellow owner who thinks several accidents local Caterham owners have had have been cause by LSDs though.
I have a plate style LSD fitted by someone who knows how to set them up for a Seven and it has transformed the car, so I would recommend the upgrade. I know a fellow owner who thinks several accidents local Caterham owners have had have been cause by LSDs though.
Have a read of this:
https://www.fastfordmag.co.uk/fastford-features/fa...
Basically - for a racer where absolute performance is critical, use a plate diff. For a road car use a Quaife ATB as you'll get 90% of the performance forever and at a super sharp price these days.
I've got a plate LSD in my 7. It certainly makes life a lot more fun coming out of slow corners and through roundabouts, especially with a nice tall first gear! I think much of the understeer people complain about is because they have a front end set up to work well with the stock (open-diff) rear set-up and it obviously will no longer be optimal for a rear-end that now has very different handling characteristics. I guess a bit of budget has to be thrown at the front of the car if we change the rear....
Turn7 said:
Anyone able to explain the differences in LSD's ?
In a technical sense, there are really three types to consider.A torque biased diff (ATB) where the limited slip action come from gearing. When torque is applied, the gears begin to lock up as they are almost like worm gears and work one direction but not so well in the other. The advantage is they provide good LSD action and don't require servicing. Low speed/power off they behave like an open diff and so are good for road use. The disadvantage is that the require torque to be transmitted to work, so if one wheel gets airborne, or finds a particularly slippy bit, then the LSD action can be lost. This can happen quickly and can require a 'lift' to come back and so they are not really first choice for track.
Plate diffs use small clutch like plates to provide the LSD action. Wedges force the plates tighter together as torque increases - and so need to be set up for the power and weight of the car. They will wear out over time and need serviced occasionally. The big advantage is that there is always some LSD action and they're more predictable (and reliable) for track type driving. Disadvantage is they can cause understeer on the overrun and at slow speed.
There are a group of LSD diffs that are hybrids which use technology from both types.
Edited by DCL on Saturday 29th September 09:48
downsman said:
Ah but a Quaiffe isn't a limited slip differential..............................................
I have a plate style LSD fitted by someone who knows how to set them up for a Seven and it has transformed the car, so I would recommend the upgrade. I know a fellow owner who thinks several accidents local Caterham owners have had have been cause by LSDs though.
Quaife do a torque biasing and plated diff'sI have a plate style LSD fitted by someone who knows how to set them up for a Seven and it has transformed the car, so I would recommend the upgrade. I know a fellow owner who thinks several accidents local Caterham owners have had have been cause by LSDs though.
And a TB diff is a type of LSD and probably the one I like for road but I've only ever had them on AWD.
DCL said:
In a technical sense, there are really three types to consider.
A torque biased diff (ATB) where the limited slip action come from gearing. When torque is applied, the gears begin to lock up as they are almost like worm gears and work one direction but not so well in the other. The advantage is they provide good LSD action and don't require servicing. Low speed/power off they behave like an open diff and so are good for road use. The disadvantage is that the require torque to be transmitted to work, so if one wheel gets airborne, or finds a particularly slippy bit, then the LSD action can be lost. This can happen quickly and can require a 'lift' to come back and so they are not really first choice for track.
Plate diffs use small clutch like plates to provide the LSD action. Wedges force the plates tighter together as torque increases - and so need to be set up for the power and weight of the car. They will wear out over time and need serviced occasionally. The big advantage is that there is always some LSD action and they're more predictable (and reliable) for track type driving. Disadvantage is they can cause understeer on the overrun and at slow speed.
There are a group of LSD diffs that are hybrids which use technology from both types.
Also plated diff's can be 1 or 2 way so that can work on acceleration only or on braking and acceleration. They can be tuned with different ramp angles and preload to suit your driving.A torque biased diff (ATB) where the limited slip action come from gearing. When torque is applied, the gears begin to lock up as they are almost like worm gears and work one direction but not so well in the other. The advantage is they provide good LSD action and don't require servicing. Low speed/power off they behave like an open diff and so are good for road use. The disadvantage is that the require torque to be transmitted to work, so if one wheel gets airborne, or finds a particularly slippy bit, then the LSD action can be lost. This can happen quickly and can require a 'lift' to come back and so they are not really first choice for track.
Plate diffs use small clutch like plates to provide the LSD action. Wedges force the plates tighter together as torque increases - and so need to be set up for the power and weight of the car. They will wear out over time and need serviced occasionally. The big advantage is that there is always some LSD action and they're more predictable (and reliable) for track type driving. Disadvantage is they can cause understeer on the overrun and at slow speed.
There are a group of LSD diffs that are hybrids which use technology from both types.
Edited by DCL on Saturday 29th September 09:48
My favourite rear diff was the Mitsubishi AYC rear that was basically an open diff with an electronically actuated multiplate clutch pack to accelerate of decelerate one wheel compared to the other. Provided active yaw control and LSD function all in one
Edited by Gary C on Saturday 29th September 10:39
I fitted a quaife atb to the Westfield and very much enjoy it. Makes the rear end more predictable in terms of no longer sometimes goes sideways sometimes lighting up one wheel. This allows you to get of the line quickly without occasionally lighting up one wheel, and to get the back end out reliability, etc.
Fast road use, but predominantly autotesting. Suspension set up very soft, to suit the light car and mixed road/course finishes.
Daniel
Fast road use, but predominantly autotesting. Suspension set up very soft, to suit the light car and mixed road/course finishes.
Daniel
Batwing 7 said:
Have a read of this:
https://www.fastfordmag.co.uk/fastford-features/fa...
Basically - for a racer where absolute performance is critical, use a plate diff. For a road car use a Quaife ATB as you'll get 90% of the performance forever and at a super sharp price these days.
In a more classic roadcar that may be true, but I'd take issue with that where a caterham is concerned. It clunks and shunts anyway, and is a light car. I had the same 'dilemma', but was convinced by various caterham experts that plated was the way forward, and certainly haven't regretted it.https://www.fastfordmag.co.uk/fastford-features/fa...
Basically - for a racer where absolute performance is critical, use a plate diff. For a road car use a Quaife ATB as you'll get 90% of the performance forever and at a super sharp price these days.
When I bought mine (vanilla 1.6k) I didn't believe it would need an LSD. With what is more or less a 'live axle' - well, lighter, but still a solid axle, not really an independent rear end.. it suffers more than anything else I've ever driven from an open diff. Yes, I was probably driving like a twunt..
Stuck a diff in it, awesome. Best money spent. I got a plated ZF.
Allegedly - as I have no experience of the others:
The quaife ATB is quieter, and as others have described has some issues with very low grip/hopping kerbs.
The titan is the current, and has slightly better ramp angles than a stock ZF, but unless you're a very very fast and sensitive driver it's hard to tell, AND the titans seem to require more regular servicing.
My ZF hasn't added one jot to the noise of the car. I appear to be very lucky in as much as it doesn't clunk and bang parking, or at all on the road. Sometimes I've managed to make it chatter/shunt a bit on track, but it's transformed the car, and again allegedly, they last forever and need little attention.
I heard about this LSD induced understeer quite a bit before I ever drove a car with an LSD. I subsequently raced two different cars with LSDs and never experienced it.
It may be more of a problem in a Caterham with 8" rears?
In my opinion, nine times out of ten when a Caterham driver is complaining about understeer, the problem is not so much with their car but with their feet (assuming suspension setup and bar selection aren't massively wrong)
It may be more of a problem in a Caterham with 8" rears?
In my opinion, nine times out of ten when a Caterham driver is complaining about understeer, the problem is not so much with their car but with their feet (assuming suspension setup and bar selection aren't massively wrong)
Edited by HustleRussell on Monday 1st October 16:14
Whilst I don't have Caterham specific experience (with regards to an LSD) I have run one in my 02, e21 and e30 BMW's for the past 30 years and the benefits over an open diff' are huge. The LSD in my e30 M3 was rebuilt and increased to 45% lock from the OE 25%. Personally I found oversteer far more progressive and much more easily managed when running an LSD. I no longer lift the inside wheel on slow / tighter turns and spin power away.
I guess the theory is that it can generate understeer in slower corners particularly on entry as it's trying to reduce the differential rotation of the wheels, and so inhibiting the rotation of the car.. in the same way as apparently it stabilises the rear on the brakes..
Maybe I'm a hamfisted oaf, but I can't detect either, and any understeer can easily be dialed out with the feet (or the ARB's)
Possibly more of a concern with powerful FWD cars with locking diffs?
Maybe I'm a hamfisted oaf, but I can't detect either, and any understeer can easily be dialed out with the feet (or the ARB's)
Possibly more of a concern with powerful FWD cars with locking diffs?
upsidedownmark said:
I guess the theory is that it can generate understeer in slower corners particularly on entry as it's trying to reduce the differential rotation of the wheels, and so inhibiting the rotation of the car.. in the same way as apparently it stabilises the rear on the brakes..
Maybe I'm a hamfisted oaf, but I can't detect either, and any understeer can easily be dialed out with the feet (or the ARB's)
Possibly more of a concern with powerful FWD cars with locking diffs?
I think when it's driven in a purposeful way, with power used through the corner, it's not a problem. But plate diffs can introduce significant under-steer if you're not paying attention - I've certainly been caught out on in-laps.Maybe I'm a hamfisted oaf, but I can't detect either, and any understeer can easily be dialed out with the feet (or the ARB's)
Possibly more of a concern with powerful FWD cars with locking diffs?
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