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Discussion Starter #1
So... that's the question:

Is it a bad idea to take a sander or a grinder and sand down/smooth the feathered edges on a tire that is starting to cup?

My back tire is starting to cup and has the tell-tale feathered edges on the tread pattern. Only about 2,000 miles on the tire and it has plenty of tread life left.

I've been running it at 42 psi. The bike is not overloaded. (Wife and I weigh less than 300 lbs. combined!)

I've always wondered if you could knock those feathered edges down and improve the tire life somehow.

Yeah, I know... just buy a new tire. I may do just that, but I might try this first.

Anybody tried this before? Did it help? Or, was it an exercise in futility?

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IronMan
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Year or so on here guy took file/rasp and spun tire and knocked down tire. Have beads in tire , i added beads to a real bad cupped tire and stopped my butler mug from shaking and got another 4000 out of tire. Also if front put 41 lbs in it to ride more on center.
 

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I've done it a number of times using a surform file. All you are removing is rubber that isn't going to wear off anyway. It's not going to wear better or handle better but it will make less noise. I did it as an experiment to see what effect it would have. Tires under certain conditions are going to cup because the tread blocks are always moving. If you want tires that don't cup get tires without tread. :rolleyes:
 

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The feathering is annoying but it doesn't have much effect on anything but noise :thumbup:
 

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I consider my life worth more than that. :shock:
How does life / death play into this? Filing down some feathered edges isn't going to cause a tire to fail. I don't think it will accomplish much but you aren't going to die from it.

To the OP....unless you change something else as well, they're just going to cup again and come back so I'd just ride it and forget it.
 

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Rubber flexes so much, those little raised edges aren't going to change anything.
 

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I don't see how doing that would really help, other than maybe with noise. But probably won't really hurt either.
my father- in- law used to own a machine that would sand car tires back to round. I've not seen any machine like that anywhere in many many years!!! Sanding tires back to round probably was not the best idea around; but at some time some company made a machine to do it.
 

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I usually shave my Avon Cobra rear tires twice in their life span. I use a Stanley Surform rasp and set the blade in it backward so that the tire is pulling the rasp away from me instead of risking impalement. Before you begin such a job, run your palm over the tire to see where the feathering begins on each side and then eyeball a starting place for each side that will give you the same profile left and right. With motor cold, start on center stand with center stand tied in down position and run in third gear. The rasp will chatter a lot at first and as the feathers are removed it will chatter less and then the chattering stops as the job is done. DO NO remove any rubber in the middle or your tire will be worn out soon. I get a good double handful of loose shaving off each time and tire rides like new. When the feathers are left alone on a Cobra, there is little noise, but you can feel it and I "think" tar snakes get even more like oyster snot in the curves, but that could just me me thinking too much. I do think this job is a bit dangerous and has risk of throwing the rasp into the fender or the tire pulling you hand in and then there is the carbon monoxide exposure. I do NOT advise this. Just ride and put-up with it.

prs
 

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I have thought about trying to sand down the bumps. I would think that it would help mostly with the wobble during low speed turns, and with the noise at higher speeds.
 

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Discussion Starter #12
I usually shave my Avon Cobra rear tires twice in their life span. I use a Stanley Surform rasp and set the blade in it backward so that the tire is pulling the rasp away from me instead of risking impalement............ I do think this job is a bit dangerous and has risk of throwing the rasp into the fender or the tire pulling your hand in... I do NOT advise this. Just ride and put-up with it. prs
prs,

I agree, not that safe to do it that way. I was thinking more of using an electric sander with a really rough grit sandpaper on it and trying to smooth the edges down that way. (Not running the enginge and letting it drive the tire while I hold a rasp.)

I may try it just to see.

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Some of you would REALLY freak out if you saw tires that are 3 times softer than a GW tire and 2ply being grooved at dirt tracks then going over 100mph on them.
 

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I had a tight ass friend try it with a belt sander. He put it on the center stand, started it and put it in gear. When he laid the belt sander to it, the smoke started rolling. The stink had the neighbors raising hell. Smell hung around his garage for days..............
 

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I don't see how doing that would really help, other than maybe with noise. But probably won't really hurt either.
my father- in- law used to own a machine that would sand car tires back to round. I've not seen any machine like that anywhere in many many years!!! Sanding tires back to round probably was not the best idea around; but at some time some company made a machine to do it.
Back in the '60's I had a set of wire wheels with knock off hubs on a Triumph TR3 that I had mounted Michelins on. I took them into a tire store in Renton to be balanced, and before they balanced them they put them on a machine that spun the wheel/tire combo like a tire balancer. It had an arm with a big blade on it and they actually shaved rubber off the tires to make them perfectly round as they spun. Looked like a giant metal lathe for the tires. First time I had ever seen that done, and haven't seen it done since. But I have to admit, the tires were all slightly out of round. Maybe it was the wire spoke wheels.
 

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When these tires are gone, eliminate the issue on the next set by upgrading your suspension to one that keeps the tire on the ground properly. Cupping, on a properly inflated tire, is a product of an inadequate suspension, IMO.

Ran a couple hundred thousand miles and never cupped a tire. Of course, my rear tires wouldn't cup even with stock suspenders. ;)
 

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When racing tires are often cut down to 2/32" tread (Bars showing). The machine used is essentially a large Lathe that looks like a Spin Balencing machine. The Tire is spun at a relatively low RPM (10-20 I'd guess) and a rotating blade that looks remarkably like a Pizza Cutter is employed at about 60 degrees to the rotating tread. As this blade is moved across the tread it cuts the rubber from the Tire. I don't really think I'd want to try and achieve the same effect with a Belt Sander or a Rasp File.

Here is a link that has one example of this machine: http://www.uniquetruck.com/p-15844-tire-truer-and-shaver.aspx?affiliateID=10056&gclid=CP3d_t7dgb8CFfHm7AodOzsA5A

And another picture of such a machine in operation: http://www.tireshaving.com/tire_shaving/video/Tire_Shaving_2/Tire_Shaving_2-poster.jpg

Once a tire has been "used" the folks who do this sort of thing are loathe to do this because of the danger that hidden embedded debris (nails, rocks, etc.) beneath the surface of the tire can pose to the machine and the operator of the machine.
 

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Belt sander

I use a belt sander with a very course belt. Put the bike on a jack or center stand. Don't sand the middle but just the edges where the cupping starts. For the front I let the sander turn the tire and I just hold the tire between my feet to limit the speed it turns. (aka Fred Harmon)

This wont help the tire last longer but will help with the rumble or roaring in the corners. As for handling I don't know if it helps or not, but you can feel the improvement after you sand it back to a rounded profile.

I personally believe the balance beads are the single best method of balancing the tire. And they help me with the cupping and the mileage. So far I have been through 10 sets of tires. Typically I would get 10-12K out of a set before the cupping and wear was so bad I had to get rid of them. For the last 4-5 sets I run the balance beads. The cupping has improved and the mileage is now to about 15,000 miles a set. I cant explain it, just my experience.
 

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If a tire is feathered/cupped/scalloped... chances are its out of balance, unless one has a balance device installed... and if one takes a belt sander to a tire... chances are its either already out of balance, or soon to be really out of balance.... again unless there's tire balance device(s) installed... it just might stand to reason... and is really just a thought I'm throwing out...

Also... could the feathering occur from braking?.. hows the binders on the rig?.. are they applying evenly/correctly?... again just a thought.

I'd just ride and save for a new tire. I've had pretty good wear on mine fortunately... I've got about 3,000 miles on my newish E3's and they show no signs of feathering... I run them at 41 lbs.
 

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Feathering is caused by the Caster Angle of the steering geometry combined with the amount and aggressiveness of the cornering the bike is subjected to. Playing with tire pressures, balancing methods and tire construction will affect it, but they are not the cause.
 
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