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Discussion Topic:
Right rear wheel hop above 55 mph
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supereal |
08-29-2014 @ 8:02 PM
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Senior
Posts: 6819
Joined: Oct 2009
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It is more likely that one of the tires is seriously out of balance or out of round. When I put a new set of Coker tires on my '47, it had a serious wheel tramp beginning about 40 mph. We added higher pressure to each tire until the problem lessened. We tried moving the tires on the rim with no luck. There was not enough run out to see on the car, so we believe there was a structural problem, probably, when the tires were made. Coker replaced them, and it cured it. I can now run at highway speeds with no hop or vibration. I've seen some really worn rear axle housings that didn't cause vibration.
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len47merc |
08-28-2014 @ 11:14 AM
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Senior
Posts: 1165
Joined: Oct 2013
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Carcrazy & TomO - it's been so long since I dealt with pre-'70 brake drums that the more I thought about both your comments the more likely I think it is that the drum is the culprit. TomO - I should have recalled this with your comment alone but after carcrazy weighed in it finally clicked. In my previous reply I unintentionally omitted that during the brake system restoration all 4 drums were turned and at that time I did not recall the need for balancing them, even after noting the balancing weights tacked on to the exteriors. Back in the day I had a '68 International Travelall that routinely required having the tires balanced on the vehicle for just this reason - drums and hubs were no longer balanced after turning the drums. I called the old local facility that I used at the time and was surprised to find they are still in business and still had and use their on-car wheel balancer, although only one 'senior' guy knows how to use it. Before I pull the hub off I plan on driving the car over to them next week and giving the on-car balancing a go first. Still plan to clean, check and repack the bearing (or new one) again, especially if the on-car balancing does not address the problem. Since I can get no play at all in the elevated wheel anywhere in its rotation think the on-car balancing makes sense as a first step. TomO - found your brake bearing grease locally. Heavier and more viscous that what I have been using. Thanks for the recommendation. Thanks again to all three of you. Will update with bearing and balancing findings and results next week. Steve
This message was edited by len47merc on 8-28-14 @ 3:56 PM
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cliftford |
08-28-2014 @ 10:51 AM
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Senior
Posts: 845
Joined: Jan 2014
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If you can't find someone to balance the RR wheel and drum on the car, and if all else fails, try swapping the rear drums, and see if the vibration shows up on the left side. If so I would say that the drum is at fault. Gene.
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carcrazy |
08-28-2014 @ 8:58 AM
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Senior
Posts: 1651
Joined: Oct 2009
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Your right rear brake drum may be out of balance. Not sure if you can have it balanced individually. If you can find a tire shop that balances tires and wheels on the car you can have them spin balance the right rear tire and wheel on the car. Any weight they add to the wheel will serve to balance the tire, wheel, and brake drum assembly. The downside to doing this is that you will have to mark this wheel and the brake drum so that the pair are indexed to each other. This will allow you to install the wheel in the same location to maintain balance of the assembly.
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len47merc |
08-28-2014 @ 8:40 AM
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Senior
Posts: 1165
Joined: Oct 2013
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Thanks cliftford and TomO. Upon receipt of the car last year the second order of business (after first dropping the fuel tank) was to strip the gunked-up, clogged-up brake system in its entirety and replace it all. The bearings were cleaned at that time but unfortunately I only performed a cursory inspection of the bearings for smoothness before repacking them. I ran my finger around all the axle and hub bearing surfaces for feel and felt nothing out of order at the time but in retrospect should have been more rigorous with the inspection. I bet you both are on the mark here - perhaps (hopefully) the bearing is just worn adequately enough to be the catalyst for the wheel hop without showing itself as 'loose' when testing with the wheel raised. Since I'm pulling the drum/hub again, in thinking about both your comments I plan to install a new bearing to eliminate this as a root cause regardless of what I find. TomO - what's your thinking/reasoning about replacing the drum as a potential next step? Sincere thanks again to you both - Steve
This message was edited by len47merc on 8-28-14 @ 8:41 AM
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TomO |
08-28-2014 @ 6:50 AM
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Senior
Posts: 7250
Joined: Oct 2009
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Pay special attention to the bottom bearing surface of the axle housing. Look for signs of wear and pitting. Check the bearings as well. Repack with StaLube drum brake bearing grease. Next, I would try replacing the drum.
Tom
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cliftford |
08-28-2014 @ 6:29 AM
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Senior
Posts: 845
Joined: Jan 2014
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Try pulling RR hub and inspect bearing, hub bearing surface, and housing. I would almost bet that's where your problem is. Gene.
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len47merc |
08-28-2014 @ 4:53 AM
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Senior
Posts: 1165
Joined: Oct 2013
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'47 Merc - New bias-ply tires re-checked for balance, radial and lateral run-out confirmed as well within tolerance, completely new suspension all around and low-mileage, long-idled lever-arm/Houdailles reworked and fundamentally new, 3.78 rear, springs are balanced/car rides and sits level. Plans are to drive the car at 60 mph MAX only when necessary with touring intent to maintain 55 by the speedo. Problem - the right rear ONLY begins an annoying, minor wheel hop on smooth asphalt as you approach 60 mph and worsens as you increase speed. A one-time test to 75 mph yielded no problems with any wheel other than the right rear. Side-to-side and front-to-back tire swaps have been tried but the right rear continues to be problematic. Shocks have been adjusted to be stronger but even with the right rear shock approaching max setting, the right rear only, regardless of which tire/wheel is on it, begins this hop above 55 (confirmed by feel as well as son viewing from behind in a separate vehicle). It was much worse before the shock rebuild and has improved significantly (both fronts and the left rear are rock solid now) since shock rebuild. I'd blow it off if it began to hop at 70 mph as when cruising at the planned 55 a 15 mph buffer would exist, but given it begins to be felt at about 56-57 it needs to be addressed. The right rear shock was sent back to the rebuilder and was gone through a second time without seeing any change in performance. This has to be something simple and fundamental that is being overlooked. I'm stumped. Greatly appreciate your knowledge and advice on this.
Steve
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