Rear end skipping sideways

[mikeyb]

My newly built Midge(13/60 based) rides quite nicely on smooth roads but the rear end feels like it skips sideways quite violently when hitting a bump or pothole.  I have checked the rear toe in as accurately as I can, and this appears to be as per manufacturers specs. All bushes, shocks etc are new, and all fixings are secure.  Does anyone have any ideas as to what may be the cause, or even better, a cure? Thanks, Mike.

[JohnD]

Check shock absorber settings, both sides.  Set softer.

John

[Clive]

With a midge, being lighter than the original car, will need a softer spring too. I am sure that would be in the build plans?

I assume it is herald rear spring?

How did you check the rear toe? Car loaded up with weight in seats and rolled around to get it settled?

May be worth doing 4 wheel alignment too. Did my car in a very heathbrobinson manor. String around all 4 wheels at about 6" height (set using bricks or concrete blocks) and adjust all wheels so string just touches front and back of all tyres. Then used straight edges on bricks and tape measure to set toe front and rear, adjusting both sides equally. Car seems very happy, though with over 4k of abuse since May, I should recheck in case anything has settled.

Incorrect rear toe can make a car truly horrible to drive.

[mikeyb]

Thanks chaps.  Re the shocks....these are new, standard Herald so non-adjustable.  The spring is standard too.  Usual trick is to remove 4 leaves to compensate for reduced weight of the Midge body, however, when I did this, the resulting camber was excessive, such that on full compression, the tyres rubbed on the inner wings.  After much experimentation, I finally settled on a return to a full set of leaves, i.e. back to standard.  Bearing in mind though, that the spring is over 40 years old so it has lost much of it's temper, and consequently a lot softer than original.  I have used the string method to align all 4 wheels, and am reasonably confident that the wheels are pointing in the right direction.  I will be giving this another try,before I go to the expense of changing  adjustable shocks . Thanks again, Mike.

[Pete Lewis]

Bunny hops on pot holes etc sound more like toemerrors than spring rates

you need to Load the car with 150 lbs on each seat, on a 13/60 thats all 4 seats to get the static ride height you need to check the toe

 

what you do on Midge I dont know

 

set a decent straight timber on a brick to get above the tyre bulge, hold it against the tyre sidewall

Do this both sides of the car and tape measure across the beams in front and behind the tyre

You need an extra pair of willing hands to do this. Compare the widths gives you the toe

 

aim for 0 -2MM TOE IN laden

 

to check all square use a 6ft long straight timber , holdnagainst the side wall and sight it along the

side ofnthe car

both sides should look the same. tape measure to the sill line if visual is unclear

same with the fronts , set stg wheel ahead and sight the run each side , oth front and rear should appear /measure as parallel

[mikeyb]

Thanks Pete, I'll give that a go.  I think I may have dialled in some errors when I did this initially as I have 15" TR3 wire wheels fitted and I used my O level maths to calculate the measurements! Probably not a wise decision.  Mike.