Three Wheeler Rear end Sag

Back to Technical Articles

Rear End Sag, by Ian Pinkney

As the years go by, many of us seem to suffer fromthis, but enough of my personal problems, my trikehas got it too.
Not unrelated is the steering,which, unless I’ve become too used to modern cars,is really dreadful and keeping it in a straight1ine on overrun down a road that has trenches init has become nerveracking. Then 1 had a go inKe1s Hannahs car, and what a difference, so I knewit could be improved.
Jack up the back of the car under the tube, undo all the nuts and remove caps, use a large hammerand out comes the rear suspension. Three thingswere obviously wrong. First, the spring must havebeen a bit flat because it came out so easily.Then I noticed that the rubber shackle bush insidethe spring mount had almost disintegrated, withthe consequential up and down play, and lastly thefelt on the sliding bush was worn so that therewas some up and down movement.
Ian and His Three-wheelerHaving some distant Scottish ancestry, I managed to look through my old spares and built up a verygood rear spring set with a good curve on it.Also I managed to use the top felt from anotherbush, as it seems the bottom half wears muchfaster than the top. One tip is don’t try andjudge springs when they are on the arms.
I wasfooled into thinking I had a good curve on oneset, only to realise that it was a deep dish armwhich is forged with a different spring angle tomake them higher at the back than shallow disharms.
The hub wheel bearing also had some wear so Idecided to change them too. Again, after theevent, the removal of these would have been easierhad I left the arm in the car first. I’ve heardof the threads in some being the wrong way rounddue to people adapting Scout offside hubs, socheck all threads with pins first. The dust coveris right hand thread, and grips and hammer soonget this off. A castle nut holds on the hub, andthis is left hand thread. I found no need for apuller and managed to tap it off once the brakeshoes were out of the way. The small bearingcomes out with a drift from behind, but don’tforget the spacer, small end towards smallbearing.
The larger bearing is retained by aretaining ring and odd spring clip. I understandfrom old articles that this may be right handthread, but mine was left hand. Reassembly of thehub is straightforward but easier if the brakeshoes are put on before the hub unit. The largebearings are RLS9A or RLS9 and the smaller LS8 orRLS8, and cost about £20. (in 1992, psb)Why is it that there is never any grease in therear hub when taking it apart? MOTs are normallyobtained when driving alone. When loaded with allthe junk for a rally the rear goes down (or not,if you read on) and the brakes go on. Ten milesdown the road, what’s that funny smell? Whoops,rear hub on fire! My answer is the footbrakeoperates the front brake, and the handbrake therear brake.
I’ve got this thing about trikes handling betterif high at the back (is it castor angles?), sowhat I did was to put in a packing piece about3/8″ thick and filed down to a wedge shape. Thiswas put between the spring and the arm, and boltedthrough using the spring mounting bolts. Thiswould have the effect of increasing the angle ofdangle and raise the rear of the car to about thesame as a deep dish arm.
The brass bearings are the next job, and theseshould be a reasonable fit (the Spares Scheme usedto have them). You often find that the offsideones wear better than the nearside tubular ones,and it is possible to saw off the ends of offsideones and use them for the nearside. I was not afounder member of Bodger’s Corner for nothing!Make sure all bearings are well greased beforereassembling, as I always have doubts that anygrease gets there afterwards. On the nearsidebearing line up the grease nipple on the cap tothe hole in the bearing.
It’s best to wait a day before the next bit, orsupply earmuffs to the neighbours! Knock thebolts back on the chassis, so in theory they don’tdamage the brass bearings. Grease the felt padsthe day before to try and get as much soaked in aspossible. Slide in the spring, and lo and behold,the bearings are at least two inches below thehousing. Then I remembered where my old rearspring came from. I got it retempered years agoand realised it was so curved 1 couldn’t get itin! 1 put a trolley jack with its wheels pointingdown the chassis, and it moved only slightlybefore lifting the car off the supporting jack.What I needed was ballast, and plenty of it. Inow had the wife and daughter seated in the car,and this time it started to get closer. Fromexperience this is not the time to make jokes onthe only advantage of the failure of diets.
Bythe way, remember to put the inner fibre disc on.Make a token effort to keep grease off. I cleanedit in paraffin and roughed it up with a wirebrush.
Now comes the clever bit. Get two large G-clampsand hook one end on the top of the chassis and thescrew-up end on to the caps that are protectingthe brass bushes. Screw a bit each side at atime. It’s not quite as easy as it sounds, andsometimes they slip off, but with the clamps andthe jack, in they went. Bolt on the caps,re-attach the brake arm and fit the fibre disc onthe shock absorber. Then do up the metal disc,and the large nut and locknut, and splitpin. Dothese up tight, e.g. big hammer. Grease up thebearings, and I found I’d lost the grease nipplethat lubricates the felt bearing bush that islocated on the tube.
Back to my obsession with rear ride height. I’ve4.50×19 tyres on the front, but when new I found Icould not get them on the back, and if 1 did thetyre rubbed on the rear wheel cover. I thereforeused a 4.00×19. Now the arm was down more at anangle I found I could use a part worn 4.50 on theback, which is a Dunlop flat pattern, which shouldput more rubber on the road.
The car was then let down, and what did I find? Iwas a good two or three inches better off than before (I’m also submitting this article to Penthouse). There is absolutely no movement at the back at all, try and lift the rear end and there is no give before the wheel comes off the ground. Now the test drive. What a difference!Hands off at 50, down hill, lift off, open eyes,and I’m still on the same side of the road!

 

lan Pinkney


WebSTAT - Free Web Statistics

Total Page Visits: 99 - Today Page Visits: 1