phughes

Not even close to the same thing.

AlmostTrick

I don't have experience doing this but done carefully and cleanly I don't see how your proposal would cause any safety issues. And you certainly don't deserve any scorn for thinking outside the box or asking for answers to a specific question.

Let us know how it goes.

Elvo

Tire bead jack in combination with tire levers, let the tire expand in the sun, or take it to an experienced mechanic?

bike_accountant

Be careful with sandpaper

Koyote

You’re the reason that this forum has an ignore function.

‘bye.

superdex

Don't sand.

Get out your spoke wrench and tighten everything 2 turns. Poof, you've shrunk your radius. You're welcome.











* Edit: Apparently this suggestion has caused a few people to bristle; allow me to clarify its farcical intentions. This entire thread is a "kids, don't try this at home," including the facetious comment above. There. Now go buy a tire jack and move on to something else.

growlerdinky

too smart for your own good

urbanknight

Should anybody wander into this thread and wonder, that's a joke and in real life would likely lead to catastrophic failure of the wheel.

pdlamb

OP, it’s not enough to come up with an “outside the box” idea. You need to consider how you’d implement it. For instance:
1. How much are you planning to sand off?
2. How are you planning to control the sanding process? I’d get bored with a sanding block rubbing it around the rim, one side at a time, to get a couple mils off. Hit it with a belt sander, though, and you get:
3. How are you going to sand the rim down enough to get a tight tire on and off, without gouging it in the process? Too big a gouge and it’ll pop right off – probably right before you reach a hairpin curve going downhill.
4. How are you planning to maintain the edge of the rim profile? Sharp edges could cut into the sidewall and give you a blowout, probably in the same location as the previous concern.
5. Are you willing to give up any semblance of a warranty on this wheel? I’m pretty sure the manufacturer will laugh in your face if you try to claim there was a defect after you’ve re-shaped the rim.
Those are just the questions that pop into my head on a casual reading. I’m sure there’re more that need to be considered before you head out to your garage.

jesnow

To be clear I can get the tire on and off, using the usual tricks (I don't bring an experienced mechanic on rides with me usually), but it requires about 10x the normal amount of force. This is not normal, these tires were on other wheels just fine. The problem is the rim.

jesnow

These are good questions to ask, thanks!
1) I posted my calculations about this up the thread, I figure the maximum is about 0.15 mm along a few cm of rim. That's not even enough to see.
2) The top of the rim has a round profile, I think it would be wise to keep, so I think hand sanding with wet/dry sandpaper would be the way to go. No belt sander or sanding block.
3) See above, If you start with 100 grit that will score the aluminum, but following with 300 and 600 (wet) will bring the finish back to perfect. I'm just trying to get it back to *normal*. That doesn't pop off in turns. It will be a slightly low spot on the crest of the rim hook, but not even close to the level of the bottom of the hook, and not for the entire circumference of the wheel, just the point of maximum stretch (which will then have to be marked).
4) I think I can hand sand it pretty well smooth.
5) I void warranties on just about everything I buy! I can't help myself.

Steamer

The rims are probably defective. It happens.

jesnow

I measured the rim circumferences of two front wheels (new and old), and swapped the tires that were on them. They were indeed *very* different in ease of tire mounting independent of the tire used, and they were repeatably different in circumference. I don't think the rims are defective -- I think manufacturers are making them this way on purpose.

jesnow

More new information: I measured the diameter of the hook in the aluminum rim of both wheels with digital calipers. The old Dura Ace rim hook is 1.76mm in diameter, the newer Cheap Chinese rim hook is 2.26. Assuming they're the same material I can easily sand off 0.5mm from the CC rim without compromising its strength. That's way more than I had in mind. Well, the whole *reason* I'm getting new wheels is the Dura Ace rim busted right at the bead as a consequence of riding over a train track at 40 mph in a race a few years ago, and I've been living with that since.

jesnow

Quite right, I post a serious question here and people here get their nose out of joint and post stuff that will get people hurt if they follow it. Somebody should report that post, but I just sort of ignored it.

jesnow

I'm not sure how I've been unpleasant to anybody, though I've surely been called an idiot over and over again, including in this post from you. So it took me a while to get around to doing some measuring and comparing, just as you say, which I have now done (see above). Tight wheels are indeed well documented, they existed much more than four or five years ago and so did all the tips and tricks discussed here. *That wasn't my question.* You could easily have answered my question as "I don't know", which is clearly the case, and would have been fine. But you have to beat us all over the head with an answer to a question that wasn't asked. I'm familiar with this kind of toxicity, it's pretty common in cycling and it doesn't upset me. A lot of other people have answered with really helpful ideas, but you're better off butting out. Bye now.

cxwrench

You've definitely been unpleasant and thrown the 'know it all' bit a bunch. You had to know it was coming despite what you requested in post #1. I see the 'I know how to put tires on, I've been riding for xx years' all the time. All. The. Time. There are some really tough combinations but 99% of the time we can put them on in a matter of seconds. Removing material from a rim has not crossed my mind in over 25 years of making a living as a mechanic.

jesnow

So far I have had 11 very helpful posts in this thread, ones that told me things I didn't already know. I want to thank pdlamb, 70San0 79Pmooner, THook and UrbanKnight for thinking about my question and answering thoughtfully.

15 other people answered in some way that while not moving the ball was at least non-insulting, and thank you too.

To the 21 people who answered negatively including especially Growlerdinky Koyote and shelbyfv, why don't you just leave it alone when you're ignorant on some topic instead of coming back and insulting people? You guys (and you know it's guys who do this) are probably just the same out on the road. Too much testosterone or something. You might dial that stuff back. You give cycling a bad name.

Anyway I'm pretty sure I know now how much material to remove and where. You can calculate the length mismatch from the chord length (~1mm), and from that you can calculate how much material to take off from one side of the chord, and it doesn't even come close to the thickness of the bead, which is twice as thick as it needs to be. The measurement of difference in rim circumference between new and old rims checks with the calculated mismatch between rim and tire -- again around a mm of circumference ie 0.15 mm radius. This is nothing, impossible to see on a truing stand, but (my prediction) makes the difference between popping a tire on real quick and an uber ride home with sore thumbs. I can't seem to figure out how to post pictures, or I'd show some photographic evidence.

I have the sandpaper and stuff, but I'm not doing it tonight. Probably over the weekend.

If I'm right or wrong, I will post here and y'all can call me an idiot some more.

Cheers,
Jon.

jesnow

I didn't say I know it all. I said I know the tips and tricks, which I'll admit the kapton tape someone mentioned I hadn't thought of. So that's one thing. You can always get a bigger wrench or a bigger hammer, and of course I did that. I did get the tires on there, but there's no way that's working out on the road. What's nice is a lot of people actually engaged with my question and had something thoughtful to say about it. I learned something from those people. I'm a professional "out of the box" thinker I can't help myself. It's sometimes a disaster and sometimes awesome.

Your initial answer was at least honest and to the point. I marked that one "neutral".

cheers,
Jon.

thook

well, man, if you're gonna do it, go fine grit and keep checking your work just until you can get the tire on easy enough so you know what you're up against with a road side repair. when i got those panaracers, i knew there was no way in hell i'd be able to make one. do you have a digital micrometer? it'd be handy. you might even just sand on one rim bead 'cause you only need one side to actually get the tire on

fwiw, i didn't find any of your replies to be unpleasant. frustrated, but not even insulting. i've been in those shoes over different but similar matters. pots meet kettles sorta thing

Gresp15C

An amusing anecdote: My spouse's new bike came with tubeless-ready rims, and it is extremely difficult to get tires on and off, even with the bead jack that I've used successfully on other bikes. There's no way that her hands will ever be strong enough to deal with a flat while on a ride, even if she brings the bead jack along, and she's quite mechanically inclined.

Another pair of tires that we tried was so tight that we couldn't mount the rear one at all. We were very careful to keep them in new condition, did not ride on them, and the shop graciously took them back.

I started a thread on HN at the time, and received some replies to the effect that this is a common problem with tubeless-ready rims. Now I know what to avoid. A more recent thread, that I have no hope of finding, suggested that manufacturers have backed off on the designs of those rims.

Measuring the absolute diameter of a rim would be difficult with home shop tools, but the difference between two diameters should be easy with a yardstick and a few odds and ends.

jesnow

Thanks, this is what I was thinking. You know the potential for expensive embarrassment is quite high. Especially since I promised to post here if it all goes south. My wife agrees with growlerdinky and them and thinks I'm an idiot for even contemplating it. I was thinking I would mark the place where the bead starts to get tight on the rim, then take just a tiny amount off near there and see if that changes the stretch point at all. There's about a 90 mm difference between the length of the chord at the stretch point with the *same* tire stretched on the two rims. That also works out to about a mm difference in circumference.

Hey I got the upload to work! Here is my setup for measuring the total circumference *difference* between the two rims. I have a mark on each rim and marked the tape by rolling the new rim one revolution. You can see the start mark by the first joint in the floorboards. The end mark for the new wheel is way far away, you can't see it. The new wheel nails that mark spot on every time. The old rim stops with its rim mark about a mm behind the mark of the new one every time. Best I can do today, but it's better than trying to measure the diameter, which is factor 2*PI smaller difference. I don't think I can measure that precisely enough to tell.

thook

jesnow a micrometer sure would make it easier and more accurate. google micrometer and see what i mean. you could use the caliper going around from where each nipple enters the rim and to the rim edge. i mean, you really may only need to take off less than a mm. and, i'd think that would be a better idea than taking off more than that in isolated spots so you could get the tire on. it'd be uneven and those spots would be even weaker. follow?

veganbikes

Ahhh you know all the tips and tricks, that is great, you should share them all here because I know that there are some I haven't yet learned and my boss who has been working in bike shops for over 30 years probably doesn't know ALL of the tips and tricks, I mean he knows a lot but not all like you. I also have some other mechanic friends who have been doing it for 20 years+ who would love to hear all the rest they don't yet know.

I mean if you knew all of the tips and tricks you would have those tires on already because some of those tips and tricks work quite well for tougher beads. Also someone who knew all those tips and tricks wouldn't ever go to lets just start removing material on the thing that holds the tire and you brake on which further wears down the rim but of course you know them all and tried them all so who I am I to judge. As it says in the Torah "Only Judy can judge me".

I just hope one day to ascend to your level of greatness that I can know everything and yet still somehow have an issue and think to myself what is the most dangerous way I can solve my issue and then when people give me useful advice I can shoot them down like Manfred Von Richtofen in WW1.

The way you have acted makes me want to say "try this at home" but the person who has worked in shops for the past 10 years and the bicycle rider and lover in me says DON'T DO IT DUDE, COME ON! Seriously if you are having trouble then ask for help and accept it, if you want someone to say yeah go for it then go down to the local hobby supply shop buy some modeling glue take a big sniff and go for it.

Chuck M 

The OP just needs one person to validate his idea. This happens on every internet forum for everything. Once someone does this and claims it works, there will be a plethora of what type of sandpaper to use and if a disk or belt sander is better/faster posts.