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Quaife Atb In A Road Car: Anyone Have First Hand Experience?


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#1 growlerbearnz

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Posted 29 May 2021 - 06:19 AM

TL;DR: If you have a Quaife ATB, is it a bit twitchy on the motorway (65mph) when lifting off and getting back on the power? 

I had a fun weekend on some very twisty roads and utterly destroyed my 2-pinion diff (along with a pair of front tyres). No regrets! 
I've gone for the nuclear option and replaced it with a Quaife ATB (this one from Minispares)

 

...and I think I've gone too far. Funny, that. 

Good points: it's more progressive than a plate type LSD: it doesn't suddenly snatch the steering wheel out of your hand, and traction through the corners and on rough surfaces is phenomenal: you can feel it hunting for the traction.

However if I'm driving on a cambered motorway, steering ever so slightly to one side to go in a straight line, there's a bit of a weave when transitioning between drive and coast. It's almost like torque steer, except there's no torque. Or like a loose rear axle in an old RWD. 

Suspension is set up about as accurately as lasers will allow. Front: 1.5mm total toe out, -1° camber, 3° caster. Ride height is set so that the driveshafts are perpendicular to the wheels (minimises drive angle differences from side to side). Bump steer is... about average for a Mini, and shouldn't be relevant to this problem.  Rear is -0.5° camber, 2mm toe in. It's on discs with 10 x 4.5" ET35 wheels, 165 tyres so the scrub radius should be quite reasonable.

Marketing says "Drives like an open diff under normal conditions" and "You won't know it's there until it starts to work". Clearly I'm doing something wrong, or I'm a lot more sensitive to how my car handles than the Quaife marketing department. 

Anyone got any first hand experience? 

(I've found this thread which is encouraging, maybe I can further reduce the twitchiness by fitting firmer suspension bushes.) 


Edited by growlerbearnz, 29 May 2021 - 11:28 AM.


#2 evoderby

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Posted 29 May 2021 - 07:12 AM

No first hand experience I am afraid, quite some threads on the blown mini forum suggest however that corner weighting is the cure for any pulling and weaving experienced after fitting an atb. Rest assured you’re not the only one with less than favourable experience of these diffs, which has put me off fitting one. 
 



#3 Spider

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Posted 29 May 2021 - 07:53 AM

I have them in nearly all my Minis and Mokes.

 

I've never found they cause any 'torque steer' or twitchness, in fact, it is almost as the blurb says " drives like an open diff " only at very low speeds, it does make the steering quite heavy, other than that, you wouldn't know it's there, other than I find I don't spin wheels anymore.

 

As I have said elsewhere about there, other than original restorations, I'll never ever go back to an open diff - never.

 

I'll add here in regards to twtchiness, as you dial in any negative camber on a Mini, you're increasing the scrub radius of the wheels and that alone makes the front end very susceptible to any variations in road surface. At most, on my Minis, I set the front to zero degrees and dial in 3 - 4 degrees caster. At Zero Camber, I find I have the best compromise between braking and acceleration for traction / grip and increasing the Caster gives the front end 'bite' when cornering.



#4 PoolGuy

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Posted 29 May 2021 - 08:21 AM

I think it’s safe to say that it’s not the atb that’s causing your issues. I’d be inclined to be a little more conservative with the geometry and see if it improves.



#5 Earwax

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Posted 29 May 2021 - 10:43 AM

I have an ATB in a road car and haven't found any twitchyness either , sorry.  What tyres and tyre pressure are you running? if these a tad sensitive to slightly higher pressures,, it could contribute.



#6 growlerbearnz

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Posted 29 May 2021 - 10:47 AM

Some great info and encouraging answers here, thanks! 

It sounds like tomorrow's task is to go over the suspension again. I'll try Spider's numbers (0 camber, 3.5 caster) and see if anything changes. I like my negative camber, but more caster will do the same thing in the turns.  
 

 

it is almost as the blurb says " drives like an open diff " only at very low speeds, it does make the steering quite heavy, other than that, you wouldn't know it's there, other than I find I don't spin wheels anymore.

Interesting! I most definitely know it's there, even apart from the heavier steering at low speeds: if I'm accelerating hard and one wheel runs over a leaf/stick/small human, the momentary break in traction really yanks on the steering wheel. 

Acceleration with both wheels on a good surface is fantastic though. I can use full throttle in first gear now! Never been able to do that before. 


Edited by growlerbearnz, 29 May 2021 - 08:45 PM.


#7 growlerbearnz

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Posted 29 May 2021 - 10:48 AM

I have an ATB in a road car and haven't found any twitchyness either , sorry.  What tyres and tyre pressure are you running? if these a tad sensitive to slightly higher pressures,, it could contribute.


Yokohama A008 165/70R10 at 29psi front, 27psi rear. 

No need to be sorry! It's actually very encouraging that others have an ATB and don't find it twitchy when cruising on the motorway. My fear was that everyone would say "yeah they just do that" and then I'd have a £700 paperweight!

 

At least I now know there's a chance it might work out after all... 
 


Edited by growlerbearnz, 29 May 2021 - 11:29 AM.


#8 Spider

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Posted 29 May 2021 - 07:31 PM

.... if I'm accelerating hard and one wheel runs over a leaf/stick/small human, the momentary break in traction really yanks on the steering wheel. 

 

 

While a diff (not necessarily an ATB) can do this, so can steering geometry. Again, I can see this being the ATB (assuming here it's in good order). When I fitted my first ATB, to see just what these would do and how they'd behave, I took the Mini to a section of road that had gravel on the side. I stopped the car with one wheel on the bitumen, the other in the gravel, reved it hard and dumped the clutch. Firstly I found it would pull away quite well and secondly (and most impressively), while I could feel it on the steering, it wasn't yanking around or being difficult in the slightest.

 

Just thinking a bit more about the steering issue you have and my earlier comment, while dialing in Neg Camber does increase the scrub radius, I can't see 1 degree having that much of an effect to match your description of the feed back in to the steering.

Will it do this on side side or with either wheel ?

On a good flat, even section of road, on acceleration, does it steer straight ?

 

Same bit of road, but on Brakes, how does it behave ?

What wheels are you running and how much off-set do the have ?
 



#9 growlerbearnz

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Posted 29 May 2021 - 08:44 PM

Will it do this on side side or with either wheel ?

On a good flat, even section of road, on acceleration, does it steer straight ?
 
Same bit of road, but on Brakes, how does it behave ?

What wheels are you running and how much off-set do the have ?


It'll pull quite strongly to either side when accelerating over a poor surface. My street is quite steep and usually has leaves on one side: when driving uphill I wouldn't want to hold the steering wheel lightly, it could end up on the kerb.

On a perfectly level road under steady acceleration? Yes, it's nice and straight. If there's some camber/crown on the road then it'll pull on the steering wheel a little.

On brakes it seems fine, nothing too exciting. (The alarming twitchiness comes when driving at a steady 100kph, I lift off the accelerator to go for the brakes, but the moment my foot's off the accelerator it'll twitch in one direction. It doesn't yank the steering wheel in this case, but it needs steering input to correct. Put my foot back on the accelerator, even lightly, and it twitches in the other direction.  

Wheels are 10 x 4.5" with 35mm offset (Minisport alloy replica Cooper S LP883). Tyres are Yokohama A008, 165/70R10, so nothing particularly wild going on there. 

From your description it does sound like there's something moving where it shouldn't. I might disassemble the front suspension and go over every part. It's all practically new (10,000km since restoration) but even new parts can fail. 

Question: if you had the gearbox in neutral, one wheel in the air and tried to turn the wheel by hand, how much effort would it take? If it were a plate LSD that's how I'd be gauging the preload. Mine takes a fair shove (scientific term) before it'll turn the wheel, I'd say 20 ft.lb? ...which seems high for something that's not supposed to be noticeable.

Quaife say there's no break-in period, but maybe it'll loosen up after some miles? 


Edited by growlerbearnz, 29 May 2021 - 08:53 PM.


#10 sonscar

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Posted 29 May 2021 - 08:49 PM

For free I would be tempted to check the rack fixings to the body.I had similar experiences with a normal diff.Good hunting,Steve..

#11 Spider

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Posted 29 May 2021 - 11:07 PM

Question: if you had the gearbox in neutral, one wheel in the air and tried to turn the wheel by hand, how much effort would it take? If it were a plate LSD that's how I'd be gauging the preload. Mine takes a fair shove (scientific term) before it'll turn the wheel, I'd say 20 ft.lb? ...which seems high for something that's not supposed to be noticeable.

 

It does take a bit of effort, gripping the wheel, you can turn it with a good 'shove' as you've found - that to me sounds right.

 

I must measure the break-away torque here.

 

I found from new, they do 'settle', but they don't take long to do so. Certainly, by 10 000 km any 'settling' would have well occurred.
 



#12 growlerbearnz

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Posted 29 May 2021 - 11:40 PM

I found from new, they do 'settle', but they don't take long to do so. Certainly, by 10 000 km any 'settling' would have well occurred.

 
Ah, right, this diff is a recent addition, only 180km on it so far. When Quaife says "there's no break-in period" I suspect they mean "you don't need to give it any special consideration when it's new" rather than "it's broken in at the factory". I'm going to measure the breakaway torque here too, so I'll know if it's getting looser. Data!

 

The 10k.km is on the whole car since restoration. Straight subframe, new hubs, adjustable front suspension, all new bushes, bearings, balljoints and shafts. 
 

 

For free I would be tempted to check the rack fixings to the body.I had similar experiences with a normal diff.Good hunting,Steve..

An excellent call, but unfortunately that was the first thing I checked. It does feel very similar to a loose rack though (been there, done that, got the brown stains to prove it). 


Edited by growlerbearnz, 29 May 2021 - 11:44 PM.


#13 evoderby

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Posted 30 May 2021 - 04:54 AM

Please do check over your suspension bushes for any to have degraded. I have seen new ones turn to ‘bubble gum’ within six months with hardly any use at all, fed up with this I have now gone to fully rose jointed everything. Should have done this ages ago:-)

 

The thing with height adjustable suspension is you can completely mess up corner weights without this showing up during setting up alignment. The correct way is to start off with making sure the adjusted trumpet length is the same on both sides of one axle, and from there mirror each adjustment until you have the desired ride height. Without access to scales, don’t adjust one side without mirroring the other! When having access to (bathroom) scales you can now spend hours on optimising balance.

 

A wrongly set up height adjustable suspension will make a mini twitch and weave even on an open diff (ask me how I know LOL), an ATB seems to magnify this effect. Not saying this is the matter with yours…just something to check.


Edited by evoderby, 30 May 2021 - 04:55 AM.


#14 PoolGuy

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Posted 30 May 2021 - 05:46 AM

 

 

When Quaife says "there's no break-in period" I suspect they mean "you don't need to give it any special consideration when it's new" 

 

They mean that you don't have to change the oil after a few miles and then every *****miles thereafter.



#15 growlerbearnz

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Posted 30 May 2021 - 09:12 PM

The correct way is to start off with making sure the adjusted trumpet length is the same on both sides of one axle, and from there mirror each adjustment until you have the desired ride height....
 
A wrongly set up height adjustable suspension will make a mini twitch and weave even on an open diff (ask me how I know LOL)...


Huh. I was planning to do the corner weights, but since I'm well into "overthinking things" territory now it never occurred to me to start by making the trumpets the same length.  >_<
 
When I first installed the ATB I left the ride height standard (maybe a bit tall) and I discovered a fair amount of *actual* torque steer; at full throttle in 2nd the steering wheel was pulled to the right. I dialled that out by lowering the front ride height until the driveshafts were perpendicular to the wheels, but I worked on one side at a time. Given the unequal length driveshafts my front trumpets are almost certainly out of whack. 

Something else to check while I'm re-shimming the ball joints today. 

  

 

They mean that you don't have to change the oil after a few miles and then every *****miles thereafter.


Engineering and marketing, separated by a common language. I guess I should have used smaller words when asking them. "Will it start out tight and get looser after I drive it some distance" (Answer: yes.)

I must measure the break-away torque here.


When mine was freshly installed with zero miles I estimate the breakaway torque was 15ft.lb (A very loose estimate: there was enough preload to snug up the wheel nuts).
Now it's at about 5ft.lb. I even had to break out the digital torque wrench and put new batteries in it!
So yes, there's definitely some breaking in happening.

Edited by growlerbearnz, 30 May 2021 - 09:30 PM.





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