9 years ago 0
Posted in: Uncategorized
For really, really smooth brakes …

have the drums turned with wheels still attached. Bolting the wheel to the drum distorts the drum and can cause minor or major pulsation at the pedal (think of the effect a bent wheel on bicycle has on the brakes – you can feel it on the brake operating lever located on the handlebars).  Same effect on a car only it’s at the pedal.

Out of round drums are often most noticeable when coming down a freeway off ramp at speed. You’ll feel it in the pedal, the whole car may kinda shake and the steering wheel may shimmy if a front drum is a major contributor.

Pulsation at the pedal is particularly common on wide five wheels on both buses and bugs. ’66 and ’67 bugs are particularly susceptible since the wheel itself more flexible due to the slots in the wheel.

Don’t assume putting new drums will magically solve pedal pulsation problems.  I’d expect the problem with new drums. If you do put new drums on and wish to turn the drums w/wheels attached, do it a few days and a few tens of miles later after you install the  wheels. And if your tires are tired,  wait until you can put new tires or used ones with a reasonable amount of tread on them. You don’t want to do it today and then a month later after the tread flies off that tire with the crumbling sidewall.

Vehicles with disc brakes suffer from out of round discs but it’s really warpage, not out of roundness. You can’t turn any disc with the wheel on but proper resurfacing of a disc will result in a nice fix and smooth brakes. Just make sure no one turns it under the limit but it’s best to use new ones if it will be over but still close to minimum thickness since the missing metal is missing heat sink and heat causes warping.

I’ve never turned the drums with the wheels on for any non-wide five wheeled vehicle but it can’t hurt for any vehicle of any make. The brakes will always be smoother and the pedal will be higher with the difference in height dependent on how out of round the drums  were before turning but it will make a difference.

The way to tell how bad your drums by the way the brakes behave and by adjusting the brakes. If you adjust – lock up wheel, back off until free – you may find that when you rotate the wheel 90 degrees for instance, the drum binds on the shoes and you have to back off more to obtain free movement – you’re now de-adjusting the brakes – causing a lower pedal. But you have to have free movement so you have to de-adjust.

Turning the drum will alleviate the problem and you’ll have a higher pedal. You can obtain perfection for the front and improve and possibly obtain perfection in the rear but the rears may never be perfect – rear imperfection is pretty much inherent because the rear wheels turn with the axle and the fronts don’t. Think about it …

on swing axle vehicles without reduction boxes,  the axle is long and it’s supported by … parts supported by a big bearing at the transmission end and simply a bearing at the wheel end. Perfection is hard come by. IRS vehicles and reduction box vehicles have short axles and a bearing at each end so they’re better re out of roundness but it’s not really the drum – it’s caused  by axial precession of the axle – Google it. The fronts can’t have this because you can’t have axial precession if the axle doesn’t turn and front spindles don’t turn.

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