|
|
Post by Simon Crabb on Dec 10, 2008 17:43:49 GMT
When you're diff is dirty, or badly adjusted, it affects handling. The back end can spin out more easily.
Does anyone know what's actually happening when that happens, say the diff is dirty, and a bit stiff, what is actually happening?
The outside wheel isn't able to rotate faster in the corner as the inside wheel, thus it cannot generate the necessary grip?
What about if the diff is too loose?
Does anyone know?
|
|
|
|
Post by Martin Young on Dec 10, 2008 17:58:51 GMT
I'd be interested for some more experienced members to comment on this.
As I understand it:
When too loose acceleration will be lacking and when too tight the rear end will step out more especially under power.
Is this correct? Also how tight is too tight or too loose?
|
|
|
|
Post by Reuben on Dec 10, 2008 18:31:00 GMT
well I have been running an old gritty diff for a while, then sunday I had a brand new Pro diff.
Difference was SO noticable when I was driving, it felt alot faster through the corners and quicker aceleration when turning out of a corner. and felt like less corner speed was lost than usual.
?
|
|
|
|
Post by TryHard on Dec 10, 2008 21:14:23 GMT
The trick with diffs is too run them loose enough, but with out the balls loosing grip... hence the move towards more balls in the diffs (the larger rings are a consequence of this, you can only fit so many round a small ring). More balls = more grip on the rings for the same pressure. Having said that, a good thrust race cannot be overlooked, as this takes a huge amount of load... if in doubt, change it! Personally, I always run a the diff a little tight... as if it's too loose it'll slip. This a) reduces traction (the balls don't "grip" the plates) and b) generates heat... which reduces the life of the diff. Having it tight stops the diff slipping, maximising traction. And given we mostly run spools in the front, the stepping out isn't so much of an issue, simply as on acceleration, the spool helps to pull the car through. Not to say it does have an effect, but you shouldn't have a situation where by the rear will want to overtake the front on hard acceleration (we have too much traction for that, in the dry at least..) How to set it? Simply grab one wheel with your hand, and put you thumb on the spur, then try and rotate the other wheel with your other hand... you should require a lot of force to turn it  The other way is to take it out the car, place an allen driver in each outdrive (parallel to the diff pulley), then try and rotate the pulley... you shouldn't be able to move it! HiH Ed |
|
|
|
Post by Simon Crabb on Dec 10, 2008 21:20:52 GMT
You've not told me what's actually happening to the wheels on the track though when it steps out.
|
|
|
|
Post by yellowshark on Dec 10, 2008 22:30:40 GMT
The other way is to take it out the car, place an allen driver in each outdrive (parallel to the diff pulley), then try and rotate the pulley... you shouldn't be able to move it! HiH Ed ED do you tighten it to the point where it just switches over from you could move it but now you can't?. EG you can move it, 1/8th turn, you can't move it |
|
|
|
Post by lesbaldry on Dec 10, 2008 23:42:00 GMT
The other way is to take it out the car, place an allen driver in each outdrive (parallel to the diff pulley), then try and rotate the pulley... you shouldn't be able to move it! HiH Ed ED do you tighten it to the point where it just switches over from you could move it but now you can't?. EG you can move it, 1/8th turn, you can't move it Again Pete this is "experienced " feel and is very hard to put into words,Ill show you "the feel" with one of my spare diffs next time we meet..A good diff is vitally important to correct handling. As Ed said the diff should be loose enough but with out it slipping under load (for the power of motor you are runing)..the only exception here is when the grip is high or a very flowing track(Cotswolds 08) you can afford to wind the diff tighter to gain more grip/punch out of corners,a tighter diff will also increase power on steering too. To answer Simons question..and this is only my theory and may be totally wrong..A dirty notchy diff I think causes the unloaded wheel to snatch and brake traction unevenly causing the rear to step out...Traction control in reverse  Correct grease and the amount used can "make or brake" the handling too..If the diff is built "and run in correctly" hold the spur gear to stop the rest of the transmission spinning,spin up one wheel by hand, the other wheel should spin in the other direction relatively freely..if it stops in less than about one or two turns there is something wrong,a poor thrust race,grease too thick or too much,diff too tight...hope that made sense?? |
|
|
|
Post by lesbaldry on Dec 11, 2008 8:06:23 GMT
Pete in my opinion the Xray closed diff is the best diff out there at the moment with the Cyclone Pro diff a close 2nd..you shouldn't have any probs???
|
|
|
|
Post by TryHard on Dec 11, 2008 8:57:17 GMT
Never tried a 416 diff then les? Haven't rebuilt it quite a while now... still silky smooth  Under normal operation (i.e. a good diff), a stiffer one will "step-out" more, simply as there is more locking action on the diff... i.e., it takes a greater force to make the wheels rotate at different rates. If you think of a fully tight diff like a spool (both wheels spin at the same rate, regardless), you can kinda get the idea that by tightening up the diff, you'll move the performance closer to that of a spool... It's the inside wheel spinning up (it's less loaded), and losing grip that causes the step out. HiH Ed |
|
|
|
Post by mattsedgley on Dec 11, 2008 9:01:17 GMT
I thought this was about what was happening at the wheels?? not who can build the smoothest diff??
|
|
|
|
Post by lesbaldry on Dec 11, 2008 9:31:12 GMT
I thought this was about what was happening at the wheels?? not who can build the smoothest diff?? It is! but unless your diff is working correctly theres no point in understanding the effects of a tight/loose diff  Ed no I haven't Tried a 416 diff ,my quote is purely experience of owning and running both to good effect..plus talking to other drivers who have had many cars ..no doubt its very good if thats what you are just used too... |
|
|
|
Post by mattsedgley on Dec 11, 2008 11:31:56 GMT
|
|
|
|
Post by yellowshark on Dec 11, 2008 12:32:40 GMT
Pete in my opinion the Xray closed diff is the best diff out there at the moment with the Cyclone Pro diff a close 2nd..you shouldn't have any probs??? Oh no Les zero problems, I have often extolled the virtues of the Xray diff on these pages ;D I use the method of adjusting/testing the diff in situ, as taught to me by your kind self ;D I was just interested in Ed's alternative of doing it with diff off the car. On the car is very much as you say a feel for what it is and I think after your help I have pretty much got it. I was just interested whether the off car approach was less feel and more black and white. |
|
|
|
Post by oldtimeracer on Dec 11, 2008 13:32:58 GMT
Just how important is the thrust race in the diff.
There appears to be several "option" thrust races available for most cars, some of which are pre-built races with ceramic balls. I have always used good quality ceramic balls in the diff but never in the thrust race. Will this make much difference? and does the use of a pre-built race as opposed to seperate rings and balls mean anything at all?
|
|
|
|
Post by Simon Crabb on Dec 11, 2008 14:20:46 GMT
I've been using the Square ceramic thrust, it looks just like the Tamiya one (and just like the Jaad one), but it feels a whole lot better than the standard Tamiya one. I'm trying to not get them mixed up! The Tamiya thrust *appears* to have black ceramic balls in it, but I've no idea if they are or not.
I rebuilt Ian's 415 diff with just a new thrust race (as it already had ceramic balls as he mentioned) and it's been fantastic for a good few meetings.
It needs cleaning, so it will get rebuilt as a 16 ball diff, with bigger plates and a different pulley, as described on Ed's 415 pages.
Thanks for the discussion, I think I understand what the wheels are doing now - basically if it's sticky it's uneven grip and the rear end steps out.
|
|
|
|
Post by TryHard on Dec 11, 2008 14:56:47 GMT
I thought this was about what was happening at the wheels?? not who can build the smoothest diff?? It is! but unless your diff is working correctly theres no point in understanding the effects of a tight/loose diff Ed no I haven't Tried a 416 diff ,my quote is purely experience of owning and running both to good effect..plus talking to other drivers who have had many cars ..no doubt its very good if thats what you are just used too... haha.. i see what your saying there Thing is, whilst never having run an Xray or a HB, in my experience it's still the best, and I have tried lots of other peoples diff's out there (it's one of thoose things I just do when picking a car up... give the diff a quick wiggle ) One thing I'm sure we can agree on though... the worst... Schuey  |
|
|
|
Post by lesbaldry on Dec 11, 2008 15:07:11 GMT
It is! but unless your diff is working correctly theres no point in understanding the effects of a tight/loose diff Ed no I haven't Tried a 416 diff ,my quote is purely experience of owning and running both to good effect..plus talking to other drivers who have had many cars ..no doubt its very good if thats what you are just used too... haha.. i see what your saying there Thing is, whilst never having run an Xray or a HB, in my experience it's still the best, and I have tried lots of other peoples diff's out there (it's one of thoose things I just do when picking a car up.( Perhaps those other diffs you ave wiggled are tighter and not so free as a 416 for a reason...their chassis can handle the extra traction ;D...  |
|
|
|
Post by lesbaldry on Dec 11, 2008 17:01:13 GMT
Pre built races in my book are allways better..If you can find a match for your diff.
This is where the Xray diff scores highly,its thrust race is larger than normal and sits enclosed deep in the outdrives well away from dust
The Little thrust race takes a serious load so good grease and good quality balls are a must.
|
|
|
|
Post by TryHard on Dec 11, 2008 19:25:27 GMT
Pre built races in my book are allways better..If you can find a match for your diff. This is where the Xray diff scores highly,its thrust race is larger than normal and sits enclosed deep in the outdrives well away from dust The Little thrust race takes a serious load so good grease and good quality balls are a must. Certainly agreed.... back the thing with as much good quality greese (associated black stealth is my preference) as possible. If you can find a thrust with ceramic balls, the better still I said balls... hehe  |
|
|
|
Post by yellowshark on Dec 11, 2008 19:57:00 GMT
Pre built races in my book are allways better..If you can find a match for your diff. This is where the Xray diff scores highly,its thrust race is larger than normal and sits enclosed deep in the outdrives well away from dust The Little thrust race takes a serious load so good grease and good quality balls are a must. Certainly agreed.... back the thing with as much good quality greese (associated black stealth is my preference) as possible. If you can find a thrust with ceramic balls, the better still I said balls... hehe Hmn, having raced an Xray since we started I have never seen a thrust wotsit - does the Xray diff have one? I change the balls and the round metal bit they sit on occassionally and it runs silky smooth as checked by various. |
|
|
|
Post by lesbaldry on Dec 11, 2008 20:53:24 GMT
Certainly agreed.... back the thing with as much good quality greese (associated black stealth is my preference) as possible. If you can find a thrust with ceramic balls, the better still I said balls... hehe Hmn, having raced an Xray since we started I have never seen a thrust wotsit - does the Xray diff have one? I change the balls and the round metal bit they sit on occassionally and it runs silky smooth as checked by various. Pete Im not been funny..but...are you kidding me  ....If you are winding me up here look out  ;DLOL Ok here goes...split the diff and remove the internal cire clip from the outdrive,behind this you will find a bearing and 4 bell vue "cone" washers, hiding behind these is the diff thrust race...god help you if you are taking the wet stuff out of me here ....Failing my instructions, R.T.F.M...Read The Flaming Manual!!  |
|
|
|
Post by Reuben on Dec 11, 2008 20:58:45 GMT
Ian Miller has the Jaad prebuilt thrust thingy, and his diff's feel super smooth. When he is next down give his diff a swirl.
|
|
|
|
Post by Simon Crabb on Dec 11, 2008 21:19:17 GMT
Ian Miller has the Jaad prebuilt thrust thingy, and his diff's feel super smooth. When he is next down give his diff a swirl. Most of the Tamiya boys use Jaad thrusts, I used the Square one as Demon was out of stock of the Jaad at the time. I pretty sure they're the same item. |
|
|
|
Post by oldtimeracer on Dec 12, 2008 9:34:55 GMT
Can we also assume that the suspension set up is also critical to how the diff performs in the car? The object being to keep the wheels on the ground throughout the corner as I assume that lifting a wheel with a loose diff will cause loss of traction? I seem to remeber this happens when running gear diffs? or am I (as usual) talking out of my rear! |
|
|
|
Post by lesbaldry on Dec 12, 2008 10:35:27 GMT
Can we also assume that the suspension set up is also critical to how the diff performs in the car? The object being to keep the wheels on the ground throughout the corner as I assume that lifting a wheel with a loose diff will cause loss of traction? I seem to remeber this happens when running gear diffs? or am I (as usual) talking out of my rear! Blimey Ian thats a hard one..not sure but I see it this way..to me its opposite,perhaps its the correct opperation of the diff that works the susspention??? As for geared diffs,a true geared diff with planet and sun wheels will allways favor the unloaded wheel with total loss of efective drive to the other(there will always be a slight lubrication drag/drive)..A ball diff will always be limited slip,amout of slip depending apon the tightness...hence less "diffing up" under load compared to a geared diff. |
|
|
|
Post by oldtimeracer on Dec 12, 2008 11:10:51 GMT
Well I would have thought that if your suspension was too hard say and entering a corner the inside wheel lifted then surely that wheel will spin free ot at least more free than the outside wheel that is being forced on to the ground, if the diff was too loose of course.
With the spool at the front both wheels would be turning at the same speed regardless of traction, suspension set up or anything else.
This also brings on the difference between running a diff at the front as well as the rear as opposed to running a spool in the front and a diff in the rear.
Technologically a spool is not right. In fact I cannot think of any form of motor sport where a fixed diff/spool is used in a FWD car. Has always sounded wrong to me. Why is a correctly adjusted diff not better than a spool in the front?
|
|
|
|
Post by lesbaldry on Dec 12, 2008 11:36:49 GMT
Yep..got ya! I see what you are saying ,so to stop the inside wheel spining up you would have to tighten the diff ,this would then put more drive to the outside wheel causing a loss of traction...basicaly a no win situation??,so the suspension and diff tightness needs to suit the days grip level,a balancing act??,so what works what..duno chap ...you wont need to worry about this now you are driving Purple ;D I agree with you about spools,it a buggerance way of getting more punch out of corners and we pay in more wear to be faster!..if I had my way I would ban the bloody things A really tight diff can be just as effective as a spool on some tracks giving you the best of both worlds(turn in and punch out)..but they dont last long and burnout quicker than a match in a gale!! |
|
|
|
Post by oldtimeracer on Dec 12, 2008 11:53:37 GMT
Funny how it is only recently that spools have become the norm. Always used to be diffs and then one ways. I still think a diff is easier to drive even if everyone seems to think they are not as quick.
Maybe a spool in the rear as well is the next step?
|
|
|
|
Post by lesbaldry on Dec 12, 2008 12:05:37 GMT
A spool in the rear with front one ways is the norm in 1/8 th IC, I did try it in a 10th Tourer some time ago through curiosity...fun to drive,wicked punch out of a corner "if you time the throtle right" ;D..It works with an 1/8th car due to the rear wheels been twice a wide as the fronts..foams too! A front diff is easier to drive and I would always recomend a new driver start this way |
|
....If you are winding me up here look out 
;DLOL