Isolate which wheel is throbbing/pulsing/bumping/hopping..?

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Old 01-28-16, 02:31 PM
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Question Isolate which wheel is throbbing/pulsing/bumping/hopping..?

OK, first apparently I can only edit the body of the post but not the subject header. Let's just forget I mentioned "hopping" since wheel hop is a thing but something entirely different than to what I'm referring.


I have two wheel/tire problems.
I'm trying to find how to determine what the problem is (or problems are) and whether it's the same or two different wheels. It's a used car. I know little to nothing of its history; the previous owner claimed to've known nothing about and not noticed a problem.

When I first got it there was a throbbing/pulsing/bumping --most noticeable at very slow speeds--that increases/decreases with tire rotation--that I attributed to a possible broken belt, an embedded stone, nail, screw, etc. Visual inspection revealed nothing. Watching someone else drive the car past me, none of the wheels appeared irregular. Later, I found in the car a package of tire plugs with one missing and assumed this might be it.

I don't know if this is due to a bad tire or wheel; one of the (alloy) rims may be bent/dented. I know it seems it should be fairly easy to, at least, determine whether it is front or rear, driver or passenger side but, for whatever reason, I've been unable to.

Any suggestions on methods to determine which wheel has the problem other than swapping out each, one at a time, with a fifth wheel?

On the car are four 205/50R17. I have a (universal bolt pattern) rim with a 215/45R17. Could this be temporarily used to do the one wheel at a time swap or would this mismatch introduce different problems?

If I took it to a tire shop, would/could they do anything other than using the balancing machine?
Would a trip on the balancer determine the culprit, regardless of the cause, wheel or tire, belt etc. or only if the weight is off balance?

Problem two is that more recently, a slow leak has developed. It gets low every few days. I know how to handle this if it's due to the usual causes (valve stem, bead etc.) but would like to first determine whether there's a connection to the first: bent rim or similar.

Thanks for any assistance, suggestions, etc.
 
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Old 01-28-16, 02:42 PM
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Take it to a shop and have each wheel road force balanced. They should be able to tell pretty quickly which wheels are causing the problem and whether it is the rim or the tire. For example, if they rotate the tire on the rim as indicated by the balancer and the high or low spot is the same in relationship to the rim, you have a bent rim, if the high or low spot moves in relationship to the tire, the tire has excessive road force (they will mark the tire and rim with chalk). If it turns out to be a tire issue and the road force isn't too high, they can "mount match" the tire to the rim (align high spot of rim to low spot of tire) to cancel as much of it out as possible, but if it is excessively high, you'll need to replace the tire.

The hunter website has a search tool that gives you a listing of shops in your area with the Hunter GSP9700 balancer: http://www.gsp9700.com/search/findgsp9700.cfm
 
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Old 01-28-16, 03:07 PM
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I normally get side up, hand spin tire while holding a chalk or something close to tread. If tire has bump in it, it'll scuff chalk. Also, you sometimes can see leading edge wobble.
If you ever had StopLeak or FlatFix in a tire, that tire becomes permanently unbalanced as that product never really hardens, peels off the inner wall and starts bouncing - hopping - inside tire.
 
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Old 01-28-16, 05:41 PM
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One wheel keeps going flat, Hmm.
That's the one would be the first one I'd be looking at.
 
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Old 01-29-16, 04:21 AM
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Did alignments for years and first thing was check tires. Jack up and slowly spin tire and look at tread, any difference in wear in one spot is a broken belt. If a new problem the harder it is to find as wear will be slight. Low speed vibrations almost always a tire and hard to see. Balancing will not fix this.
 
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Old 01-29-16, 04:24 AM
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one of the (alloy) rims may be bent/dented
That isn't a common occurance - is there damage that you can see?
The first thing I'd do [after inspecting the tires] would be to rotate the tires and see if the issue moves with the tires.
 
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Old 01-29-16, 07:56 AM
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I found one of my Volvo's Alloy wheels to have a small crack near the bead.

We found it by laying the rim flat and putting soapy dishwashing liquid on the bead; and the resulting bubbles/foam.

Luckily, it wasn't out-of-round, and I have a local Aluminum/Magnesium Welder who was able to re-condition the wheel . . . . finding a match to the other three would have been a headache.

Only once, and that repair was in 2012; so I guess it's holding.
 
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Old 01-29-16, 07:08 PM
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It could be a simple balance issue, but actually sounds to me more like a tire is out-of-round.
 
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Old 02-07-16, 11:15 PM
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Thanks for your responses!

Take it to a shop and have each wheel road force balanced. They should be able to tell pretty quickly which wheels are causing the problem and whether it is the rim or the tire.
This does sound like an ideal solution. However I try to do whatever I can myself whenever possible and especially steer clear of dealerships unless absolutely necessary and, around here, dealerships are apparently the only place that have this sort of balancer. Not to mention that it'll end up costing $60-80 before even get started with the actual problem.


One wheel keeps going flat... would be the first one I'd be looking at.
Yep. That's the plan... and becoming a little more attractive now that the temperatures are getting above freezing.

I'd still like to hear input regarding whether it's acceptable to temporarily use a 215/45R17 while working on this one. The others are 205/50R17.

In this article, I found some good info that may apply to my and others' similar problem.

Thanks again.
 

Last edited by ActionClaw; 02-07-16 at 11:32 PM.
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Old 02-08-16, 03:30 AM
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I'd still like to hear input regarding whether it's acceptable to temporarily use a 215/45R17 while working on this one. The others are 205/50R17.
Depends on the definition of temporary along with clearance. The less miles put on uneven tire sizes on a drive wheel the better!
 
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Old 02-08-16, 09:53 AM
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There ware websites that compare tire sizes so you can see how different your "temporary" spare is from your regular tires. I am no expert but it looks close enough to stay out trouble. However, since your are looking for something causing an uneven ride, using a mismatched tire may not expedite that answer.

Tire Size Calculator
Tire Size Calculator — Free Tire Size Calculation And Comparison Tool.

- Peter
 
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