what to set the pinion angle for escort with 4 link and a pinto? the pinion down or up?
what to set the pinion angle for escort with 4 link and a pinto? the pinion down or up?
Is it not best set parallel with the gearbox flange????
Saying that i think i set mine a few degrees down just to make sure there was no contact between the diff and floor when i hit the loud pedal
Ideally it needs to be set pointing down,I can't remember how many degrees (4 rings a bell)but I'm sure someone will tell you GARY??
Pointing it down will increase traction,pointing it up will give axle tramp.
i must admit i've never understood how pointing the pinion down is supposed to increase traction, as the pinion is going to try and climb crownwheel whatever angle it sits at.
the ford rally prep book suggests pointing it UP 4 degrees, why i have no idea why though.
i suppose if you have a 4 linked rear end on leaf springs you are effectively applying a preload to the springs thus effectivly altering the spring rate
By pointing the diff down 4 degrees you will stop the diff hitting the floor thus ading traction
so wheres gary and his drawings proving were all talking out our behinds?
oh yes i forgot some bloke is giving him grief to get a mk2 race car finished
The diff pinion angle should be set at the same angle as the gearbox as Matt said .
The Escort Rally manual says 4 degrees up as thats the angle of a BDA and ZF gearbox
The pointing the diff down can only aid traction by stopping the diff hitting the floor.
The diff and its link to the chassis is via a propshaft and some rubber mounts the gearbox, so in reality its just flopping around in the wind .. why do fit polybushes and rod end ? because they control movements of linkages better .. now going back to the prop .. it has an upward lift under accel , and that is transmitted to the shell by ... opps nothing, the prop bends at the UJ and slides out of the gearbox. its like trying to push something with a length of spaggetti.
drawing is here ... http://www.turbosport.co.uk/search.php?searchid=378878
its the second thread down after this one after using the search faclitiy
glad to see im not the only one that cant see how angling the diff could improve traction
The only diffs that aid traction are the ' long nose ' .. ie Opel mantas .. and then they are used as a 3rd link and tansmit the torque to a point around the C of G of the car, hence the name torque tube , this gives the car anti-squat helping traction .. a floating prop cant do that and the leaf springs or 4 link dont know what way the diff is angled .. its just a rotational force ..
so when fitting 4 link brakets it wont matter 4deg up or down ? just try tomatch box angle ?
so with a pinto should the nose point 4 degree up?I dont have engine/gear in the car so I cant find the gearbox angle.
i wouldnt panic a couple of degrees isnt going to make much difference, afterall thats why props have U/Js, infact U/Js shouldnt be ru dead in line anyway
ok smartie, my point was that the diff angle itself doesnt actually aid traction,
on the basis of improving traction because the diff no longer hits the floor you could achive the same effect by jacking up the rear suspension, or hitting the floor with a big hammer to make more room for the diff
Can I just stick my dangerous lack of knowledge in here?
I agree that the pinion nose should point at the tail of the gearbox in the middle of suspension travel (or really where it spends most of its time under power). So, on a tarmac car I'd say this is between [static ride height + a bit of droop] and [static ride height - quite a bit of squat] i.e. if you've got 200mm of travel, static would be at ~130mm up - `normal' travel between 100mm & 180mm. So, point the diff at 140mm of travel.
The figure Graham refers to is in the rally prep book and I think is where the ride height would be higher for forest/gravel, in which case the diff nose maybe wants to point up more than standard.
As for the pinion angle giving more traction - isn't this to do with changing the angles of the 4-link bars to suit what surface you're running on? For a fixed set of axle brackets this would change the angle of the pinion.
My own Mk1 has engine & box tilted down at the back by a few degrees (just all sort of fell in that way), prop & diff near on parallel to the floor. Back end is still leafs with top bars & panhard rod.
In the end I think there's loads of other stuff to worry about that'll make more difference to acceleration than optimising your pinion angle.
Bernie
If you have a 4 link the pinion angle dosnt change through the suspensions travel ..
Adjusting the forward pickups ..normally only the top one has adjustment and its such a small ammount that you would need a accurate gauge to measure any pinion change.
The reason that the "Rally Prep" book gives 4 degrees nose up is because thats the angle that a BDA and ZF go in at
Run the nose 1.5 degree down with 145Lb springs,& coilovers, 4 linked and a panhard rod then you will get increased traction off the line as the diff will preload the springs.
Tested back to back, at minus 1.5, static, up 1.5 and up 4. 1.5 down worked better as the car seemed to squat and go, as opposed to spin and chatter.
I dunno... all the theories and born out practices say a floating link cant effect anything ... and what was the variables ..
was it all done on the same day, same rpm each time , and what did the clock say... and there is that word " seemed"
Hmm interesting results .. perhaps , and i'm assuming here, that by lowering the pinion you where changing the spring rate, as i'm assuming you lowered it with the links and they where slipper springs ???
exactly like that
Tramping is caused by the torque reaction rotation around the axle center line winding the spring up untill the spring over comes the reaction (goes solid) and the wheels break traction, no load, the spring bangs back to shape, and it starts all over again..
By pulling the nose down on the links its probably raising the rate..
So its not the diff angle but the links that are causing the extra grip.. if you kept the axle at the same angle but change the spring platforms angle, this would create the same force...
I still stand by the fact that a floating link cant change the grip
ive just re read barns post, he's saying the same as gary and i. the springs are being preloaded,
so if you tried the same thing with a coil over rear end, or adjusted the diff angle by moveing the saddle plates leaving the link lengths alone then the amount of traction would stay the same
So unless you have the links and just lower the diff nose by sorting the spring seats out you'll achieve nothing ... like we have been saying, lowing the diff nose does nothing ..changing the preload on the springs does ... a floating link (the axle pinion and prop) cant change load.
hence why some people fit anti-tramps with the car at ride height and some fit them differently
Shortening the bottom links and putting the springs under preload is done by the diff angle, not by the springs, as it's this tension that the axle is creating by being 1.5 degrees down that provides the extra traction, hence why it doesn't work on a coilover only setup.
Barn .. if i set the diff up on the bench at 4 degrees up and weld the brackets on to one axle .. and then weld another axle 4 degrees down .... which one would be right at 1.5 degrees down .. ????
Its not the diff angle.. because what is your diff to set to on the bench .. what your doing is pulling the diff nose against the springs .. and thats regardless of diff pinion angle to start with
Straight edge against the flange, then 1.5 degrees down.
Works, i thought it was all bollocks, but does work. I was in car one at the weekend, the dif was up a 3 degrees. Night before re-set to 1.5 down and the driver said "loads better" without knowing what had been done (If anything)
But Barn do you not get what i'm saying ...
The diff angle is set .. and then you fit it in the car .. and pull the diff down, your loading the springs.. send it up and your loading the springs a different way.. but your doing it with the 4 link brackets .. if there was no pigs head on the axle tube you would still be loading the springs up ..
If you just have leaf springs and no radius arms you would have to change the pinion angle by fitting wedges or re-welding the spring seats on.. and this would have no effect what so ever on the springs as the prop shaft cant be pushed against by the diff .. looosen the spring clamps and raise the nose of the diff up.. the prop just moves, pull it down and it moves again.. its not the diff causing the reaction but the arms.
Its the way your changing the diff angle thats getting the results ..
you say your diff was set at 1.5 degrees down.. now if you raise it to 1.5 degrees up, your pulling on the springs..
so take another axle that is set to zero .. raise it to 1.5 degrees up and its moved 1.5 degrees, where as your one has moved 3 deg total ..
now go 1.5 deg down, yours is there allready, his has to move 1.5 degrees. so his loading the springs with the arms to get that 1.5 down .
Take a classic Gp4 build.. 4 deg up, he has to pull that diff down 5.5 degrees to get to YOUR 1.5 down .
Like i've said its not the diff angle, its what you do with the arms and the loads the put through the springs .. your datum for those adjustments should be a line along the axle tube when your axle is just sitting on its spring perches, no radius arms fitted .. when the radius arms are fitted, you can raise or lower that line . not the diff , allthough of course it will move too.
Do you want a fight hehe,
Of course i know what your saying bud, but how it's done is by preload on the springs, your correct as you know more about this than me, all i know is that it works when the nose is 1.5 down and the springs are under tension.
Maybe i should bring the Fiesta down one weekend and we can have a play on settings?? We can do the normal setups and see the results and then play around with our measuring widgets and see if we can get some differnt results by being a bit wacky, what do you reckon?
The Fiesta ... what fester, you've got a G3 !!!
the point i'm trying to clear up is that quoting pinion angle is worthless .. you'll get people setting their diffs to 1.5 down and they will have 2 threads in the bottom links and screwed all the way in the top.. fine on launch but under braking the bottom links will pop out .. ouch prop out of box and the then pitches the car up on the roof as it digs in ..
"ermm Mr Barn, i did what you said and heres my repair bill ... £13,565.49p"
Barns case .. (assumming his spring seats are set to 1.5 deg diff down when sat at ride height)
setting the diff a neutral (his diff at 1.5 D ) means no pre load on springs ..
when he set it 4 degrees up, he wound the springs up like they do when tramping .. ie they where allready halfway to tramp..
Barn if you take the link rods off at ride height what pinion angle do you have, because in the above post i'm assuming you have set them for 1,5 down as well as your 4 link brackets ..
Ah! yes Mr Gary, we have longer link bars to compensate etc...
I need to do some measurements on the car as the axle is off now having some new tubes put in, (Fully floater 4HA)
Yep, ex John Cross Fezzer!!!
Cozzie Group A uprights, comp struts with ARB & droplinks, 4HA 6 linked, loads of threads to wind in and out everywhere!
So, you wanna measure mine and i'll measure yours??
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