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Thread: Diffs set up's?

  1. #1
    Guest Member steven bough has a level 1 reputation
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    Diffs set up's?

    Hello Chicken's,
    Regarding Diffs,can you alter your car set ups by your diff?If so what is the method ???

    How do you set up your diffs - For different tracks?

    Reason im asking this is because some one i sat next to at Macc said he had talked to Andy Moore & that he said that on Corally cars it is very important that the diffs are right.
    but thats all he said,-

    I was hoping some one could explain what he might had ment by that,etc,etc.?

    Kind Regards
    8) Steven


  2. #2
    RaceChat Supporter rice98w has a level 1 reputation rice98w's Avatar
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    Re:Diffs set up's?

    i personally have always gone by the principal of smooth is better.

    i set my diff to be as loose as possible without slipping, and tune my setup in other areas of the car.

    a 12ths "feeling" on the track is very dependent on how smooth the diff is. just try putting some old balls & plates in and see how different your car is to normal.

    some-one along the line probably does adjust their diff for setups.... but for me its just another thing to get wrong! :

    Keep It Simple Stupid! :-* roflol
    ..:.:: Yokomo R12C3 - MB Models - AMC - HPI Racing::.:.

  3. #3
    RaceChat Supporter PDW has a level 1 reputation
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    Re:Diffs set up's?

    Chickens? Here's my 'cluckings' for you Steven.

    I am with Matt - go for smooth-as-you-can-get with the minimum of force clamping the diff. If you hold both wheels (one in each hand) you should not be able to turn the spur gear with your thumb.

    'Smoothness' is a function of the balls and the rings. However, the best results are not obtained with highly polished rings and balls (!). Rings should be roughed up on 800 grit Wet-'n-Dry paper and balls should be new. The roughed up rings grip the carriers better, and the balls (do both sides in other words) grip on the rings. This allows the pressure to be reduced and yet the balls will not slip.

    Counter-intuative I know, but it works. A very smooth ball against a very smooth ring will slip, and requires more pressure to make it grip - which leads to a rough diff action. Lastly, grease - it is only trying to reduce friction of ball to spur (hole) and keep s**t out of the hole. So little and light is the key. HTH.
    'Puff Daddy' races with : Team DORIS : Racer Magazine : Associated : AMC : Zen Racing :

  4. #4
    RaceChat Supporter rice98w has a level 1 reputation rice98w's Avatar
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    Re:Diffs set up's?

    someones been on the IRS website! LOL

    i use new balls and roughed up rings, best way.
    ..:.:: Yokomo R12C3 - MB Models - AMC - HPI Racing::.:.

  5. #5
    Big Jimmy G
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    Re:Diffs set up's?

    I usually go for the smooth method too, but I quite often change the tightness of the diff to alter the set up too. I find that if the diff is a little looser you get more steering, particualrly in the moddle of the corner and on the exit too. A tighter diff seems to make it more difficult for the car to turn - good for ironing out excessive twitchyness on faster sweepy tracks. I know that this is probably not the ideal method of setting up a car, but it is quick and easy and a good final tweak.... Never let it slip tho - wears the parts and wastes power.

    One thing some of the chaps at my club do is to put servo tape behind the diff rings to cushon it on the axel and hub bits. It servs two uses - it sticks the rings in place so slip is reduced and it also cushons the rings - much the same way as the Corrally O-rings do. Never tried it myself, but they swear by it...

    James

  6. #6
    Section Moderator Mark Stiles has a level 1 reputation Mark Stiles's Avatar
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    Re:Diffs set up's?

    The reason you may get less steering with a tighter diff is because, obviously, there is less slip. This results on the car handling more like a car with a solid rear axle (ie it understeers when turning in).
    Yokomo - Reedy - LRP - Protoform - Horizon Hobby UK - Sanwa - Racer - RC Dynamics - SMD

  7. #7
    RaceChat Supporter PDW has a level 1 reputation
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    Re:Diffs set up's?

    Unfortunately Matt, I have to confess that this idea pre-dates the Internet and IRS - so I am older than I look!!!!

    Some of the orginal Schumacher and Assoicated differentials used ground rings, where the grinding marks remained on the rings. When everyone went to the smooth rings, we got out the wet-n-dry to put the old grinding marks back on!!
    'Puff Daddy' races with : Team DORIS : Racer Magazine : Associated : AMC : Zen Racing :

  8. #8
    Big Jimmy G
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    Re:Diffs set up's?

    Just had a go at grinding some of my rings and it seems harder to do than it sounds.

    I have had them on 400 and 600 grit wet and dry and even if I press quite hard I can only see very faint scratches if I get the light just right. How severe do you have the scratches?

    James

  9. #9
    RaceChat Supporter PDW has a level 1 reputation
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    Re:Diffs set up's?

    Jimmy - can I check a few things first?

    Have you got the wet-'n-dry on a flat surface (like a set-up board) with the abrasive side up? (Sorry, gotta ask, it's happened before ) Key words here are flat (very, very flat) and up!!

    Have you placed the ring directly onto the w-n-d, and then moved it around in circles? It doesn't work if you hold the ring and rub it with the w-n-d.

    If yes to both the above, then you ARE looking for faint scratches, and also for the ring looking like it has a matt finish instead of a polished finish. However, if the ring is not flat to start with, you may only see the w-n-d marks in very few places.

    HTH - come back again if not.
    'Puff Daddy' races with : Team DORIS : Racer Magazine : Associated : AMC : Zen Racing :

  10. #10
    Delboy
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    Re:Diffs set up's?

    With my so far fairly short experience with 12th i have found the tightness (or looseness) of the diff to be crucial in the way the car feels on the track. Ive found if it is too tight it can be twitchy and sometimes bights coming out of corners, too loose and you end up just winding away all your power. I try to tun mine slightly loose, maybe just bordering on slipping as it makes the power delivery alot smoother and therefore smoothens out your driving.

  11. #11
    Derek Newbould
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    Re:Diffs set up's?

    For really smooth diffs use ceramic balls. They are realllyy smooth.

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