Thoughts on Potholes... Reinforced -vs- Double-Wall Rims

Discussion in 'General Questions' started by sparky, Aug 30, 2011.

  1. sparky

    sparky Active Member

    OK... I'm building a wheel with my new, custom machined hub.

    I've got a "reinforced" rim that I've got in a junk pile, and I'm wondering if I should just send it to the Wheel Master, instead of ordering a double-wall Sun Rhyno Lite for $55 or so w/ 2 day shipping.

    I just want to do this one time, because it can only be done one time without grinding the inner freewheel off. Soo...

    I never had any problem with my Chinese 1.5" reinforced rim, but the wall did bend when I hit a pothole. And it bent right above the reinforced part. I'm wondering if a double-wall rim is ACTUALLY going to protect me from potholes ANY MORE than a reinforced rim.

    And, since I was able to repair the reinforced rim by hammering it back and jb welding the crack with multiple layers (*NOT* recommended for front wheels)... I'm wondering if a reinforced rim actually has an advantage over a double-wall rim??? If a double-wall rim hits a bad enough pothole at 20mph, that wall would seem more likely to crack, as the lower part of the wall will NOT bend outward.. so such a hit would have even MORE force on the middle part of the wall, which WILL bend.

    Or am I over thinking this??

    I really think it's all in the metal used. So anybody know a good 20" x 1.5" 36 hole rim? Is the Sun Rhyno Lite good enough? Or are my inclinations right, that a reinforced rim actually has a benefit, since I was never able to get one to be "untrue" from extreme use?

    I need to get this shipped off to the Wheel Master like yesterday.
    Last edited: Aug 30, 2011

  2. loquin

    loquin Active Member

    I really like the Sun Mammoth BFR (Big Fat Rim). A little heavier than most other aluminum rims, but pretty much indestructable. The wheelmaster built a front wheel on the 26 inch (36H) version of this rim for me, and I believe I could take it off a 5 foot curb if I had to. I know I've hit potholes at speed, and the wheel stays true. (and I'm no lightweight ... (unfortunately :( ))


    Amazon has 'em in 20 inch for $32...

    Attached Files:

    Last edited: Aug 30, 2011
  3. sparky

    sparky Active Member

    Dang... wish I'd seen those sooner. They look pretty sweet.

    20"x2" is a bit wide, tho, methinks. The Odyssey Hazard Lite rims look pretty sweet, and they say 20"x1.75".

    The rim that originally came on the bike was 20"x1.5". And I'm not too keen on making it a whole lot wider, because when I put the brake cables on there, I cut the cable too short, so I can't actually adjust the brakes any wider without getting more cable. I'd need new brakes, too, because the spring is worn out and won't spread open much further than where it's currently at. And the rim always stayed true, so I think it can handle it.

    My problem was with a sidewalk that had a "tectonic plate shift", and me not seeing it until it was too late, so my front tire hopped over it, no prob... but my back wheel got hit with something like a concrete arrow, bending the sidewall of the rim.

    I do not think that any rim will actually be able to stop that, but I came here to see. I was expecting more like a steel rim, perhaps??? Or for somebody to tell me that reinforced rims were just as good as any others, so I wouldn't have to buy anymore.. but I just had the Rhyno Lite shipped directly to The Wheelmaster, because it's saving me a great deal of time with shipping. So that answers that....

    But a steel bicycle rim is something that I'm hoping somebody is still able to point me toward. That would be sweet!! :D
    Last edited: Aug 30, 2011
  4. motorpsycho

    motorpsycho Active Member

    If i were building a m.b. with 24" or 26" wheels, here's what i'd do.
    I'd get a set of ACS Z rims for it (but they can be expensive)
    The ACS Z rim is made of very a strong nylon composite (Dupont Zytel to be precise) the same stuff that the old school bmx skyway tuff wheels were made out of. The rims themselves are VERY strong, flexible and are known to be unbreakable.
    You can bend the spokes if you really try but most of the time the rim will flex and the spokes will spring it back into shape. You can bend the spokes bad enough to bend the rim, but all you have to do to fix it, is replace the spokes and have the rim re-trued.
    These rims are stronger and lighter than aluminum or steel, plus they won't bend or break like an aluminum or steel rim.
    I don't know, but that's what i'd do.
    here's a nice little tib-bit of info on these rims.
    Last edited: Aug 30, 2011
  5. retromike3

    retromike3 Member

    Tuff Luck

    Back in the time of my youth they had BMX bikes that you raced on a quarter mile track. One of the most popular wheels at that time was the skyway Tuff wheel. It was a bombproof bendex coster brake 20 inch wheel. It was very heavy but would never fail. Later they came up with a compromise it was called the Z-rim it was made out of the same material the Tuff Wheel but was laced up like a standard rim,

    The main problem with this rim was the fact that the breaking surface really did not work with the brake pads at the time. They came out with a special set of pads just for the tuff wheels. Those pads did not last very long, but they were the same color as the rim so it didn't look too bad and if you're only riding the bike for a quarter-mile shot is really not too much to worry about.

    I built a downhill bike that had two front tuff wheels on it. It was very fast and I would clock speeds of about 50 miles an hour down some of these hills. The main problem that I had was that I had to wait quite a while at the bottom of the hill for the smell of burnt brake pad to leave the area so I could put the bike back in my little station wagon in order to get to the top of the hill again.

    I went through a new set of brake pads every other time I went down the road on that little bike. I would recommend if you were going to use such a rim on a modern bike it would be in your best interests to switch to some kind of disk or drum break, or just forget about breaking altogether.( I've been told that stopping is overrated anyway.)

    Last edited: Aug 31, 2011
  6. motorpsycho

    motorpsycho Active Member

    see my post above, you're a day
  7. darwin

    darwin Well-Known Member

    Trick is to avoid the pothole. From the pic above I thought double wall meant 2 sidewalls on each side, guess it doesn't.
  8. sparky

    sparky Active Member

    No doubt. I will likely stop riding on the sidewalk now. Too expensive and time consuming to deal with this wheel building nonsense.

    Here's the difference between a double & triple wall rim...

    Here's what I'd consider to be a "reinforced sidewall"...

    My rims are "reinforced sidewalls", but the reinforcement only goes halfway up the wall.... similar to the double & triple wall rims...

    But the BIG difference between a reinforced sidewall & a double/triple wall rim is that the double/triple wall rims HIDE the spoke nipples. The double and triple walls are actually more like floors.

    THIS is exactly what led me to post my question here!!!

    The difference I see between a reinforced sidewall and a double wall rim is "the number of floors". I guess that the extra layer or two of floors would make the torque necessary to bend the sidewalls a good bit more.... but I feel that a bend in a sidewall of a double-wall rim would be a sharper bend, and far less likely be be able to be repaired.

    Oh well... I'm about rimmed and spoked out. Hope I don't have to deal with anymore custom wheels for another 2 or 3 years.
  9. motorpsycho

    motorpsycho Active Member

    a double wall rim is just that.
    the wall where the spokes go through is doubled with an air gap in between.
    I have double wall rims on my bmx bike and they are a lot stronger than single wall rims.
    BUT, in reality, single and doube wall rims can be just sas strong as each other if they are set up and built right.
    a good resource for info about this stuff is to check out old school bmx web sites.
    there's a ton of info on those sites that are very usefeul.
    there's also a lot of older products made for bmx and racing that were extremely tough, but aren't available as new anymore.
    this info would give you a name to look for, and you can usually find some of the parts on e-bay if you know what to look for.
    back in the 70's & 80's when i raced and rode bmx, the products that were available then were MUCH better than the stuff that's out there now.
    things these days are made cheaper, and not as strong in my opinion.
    sometimes, using older parts is the way to go.
  10. 5-7HEAVEN

    5-7HEAVEN Active Member

    I agree. Avoid potholes and install a front suspension fork.:idea:

    I bought a set of 32-hole double-walled Alex rims w/14g SS spokes on sale. With Armadillo 26 x 1.95 tires and a year of regular street driving, I've had one loose spoke problem, that's it.

    And that's a 70lb bike and 225lb man and backpack, running 4hp+ @ 44mph on pavement.

    Avoiding potholes in sight, of course.:devilish:
  11. 2strokepoke

    2strokepoke Member

    it's a rotten shame things arent made to last anymore, jus like our HT engines haha
  12. DougC

    DougC New Member

    I don't believe that a stronger rim is going to prevent damage if you're hitting pavement edges hard enough for them to do damage directly to the rim's edges.

    The main advantage of a stronger rim is that they distribute bump-caused shock loads better around the whole wheel and so prevent individual spokes from breaking.

    Not to be a smart-alek or anything, but you're not supposed to hit anything so hard that it compresses the tires enough to contact the rims.... Not in a truck, in a car, in any motorcycle, not any bicycle or anything else I can think of.

    It sounds like OP should be using fatter tires, or preferably, suspension.
  13. darwin

    darwin Well-Known Member

    These new cars with low profile tires and alum rims i bet have huge issues w/pot holes and curb hits destroying the rim and tire. Your talking $$$$$$$$$$ to replace.
  14. retromike3

    retromike3 Member

    strong rim VS. strong wheel

    A bicycle wheel is a amazing thing. It is a very strong structure and it holds up hundreds of times its own weight under load. You can have a very light rim and a very strong wheel if it is built correctly. On the other hand you can have a very strong rim and a weak wheel if the wrong person built it. I have been in bike crashes where both wheels were perfectly straight and true, and yet the frame got bent. The case that I was referring to actually had the front wheel in perfect shape and yet the frame collapsed right where the down tube and the head tube met.

    Building wheels is still in some cases is more art than science. I know that they can make a very strong machine built wheel, however there are some things that I really think are done best by hand.

    Wheels like many mechanical objects generally fail at the weakest point. Where that point is can vary depending on the mechanical structure of the object. Modern bicycle rims are very strong and the number of spokes on these new wheels has been dropping precipitously. Lately the modern mountain bike has dropped from 36 to 32 spokes. When I started building wheels at my shop 36 was the number that most people used. I did set up a number of mountain bicycles with 48 spoke wheels. These were generally used for tandem wheels but, they seem to work quite well for mountain bikes. I never had any of my 48 spoke wheels come back "potato chipped"

    I think there's nothing wrong with over building wheel. Currently I have been building a lot of 32 spoke wheels in my current motor bicycle is running that set up. With the Wieman double wall rim with spoke eyelets. I also try not to go wider than 135 mm with no more then an eight speed spacing on my motor bicycle because, when you over dish the wheel it seems to be way too much tension on the pedal drive side.

    I just recently built a set of wheels with velocity aero rims. These rims are 36 spoke and I'm planning on using them on a get around bike I'll let you guys know about it after they find there way on something I put together.

  15. motorpsycho

    motorpsycho Active Member

    yeah but the tires these days are manufactrued to withstand more shock. the sidewalls are extremely tough.
    most "aluminum" rims on cars these days have a steel hoop with an aluminum insert for the center, which makes the rims a lot stronger than you think.
  16. sparky

    sparky Active Member

    I'll take a 15" steelie over a 22" aluminum rim all day long...

    But I can't find steel rims for bicycles. That's why I started this thread... for thoughts on potholes!!!

    I have a 4-stroke motor and pedals... I can apply all the torque in the world needed to get this puppy up to speed for pennies or less. Once you get the forward inertia of a rolling wheel, it doesn't matter how much it weighs... and, in fact, the larger & heavier (i.e. - more inert) one should roll farther!!

    Anyway... I think that the Sun BFR rim is actually what I was looking for, since I see no steel bicycle rims. Even tho it's aluminum, those sidewalls look incredibly tought.

    And yes, my Shadow Conspiracy Undertaker tires hold plenty of PSI... 110 psi, actually. But I tend to run over a good number of pebble patches in the middle of intersections, so I usually keep it around 60 psi. Much better for the road, but the inevitability is that sometimes it falls down to 50 psi. And the eventuality of riding on sidewalks is that you won't see the damage in the concrete until it's too late, and a sliver of a concrete teaches you all about calculating psi... specifically, dividing with a denominator as a fraction of a fraction of a sq. inch.
    Last edited: Sep 10, 2011
  17. retromike3

    retromike3 Member

    I beg to differ a bit

    The question of forward inertia is really not much of a factor, But the "spin up" energy can make a big difference. I was told that if you take one pound off of the rotating weight it compares to taking seven pounds off the frame. The current set of wheels I am running right now are pretty heavy, mainly because I found some torn proof tubes that weigh a bit more than standard.

    The main reason I am not found of steel rims is not necessarily all about the weight but the fact that they don't brake worth a darn. if you are running steel rimes its going to take you a lot longer to stop than if you use aluminum rims. i have been told that if you set up a six bolt hub and a Kings adapter than you can use a disk brake and those will stop regardless of the rim material.

    Something that I also read about in BikeTec magazine a few years ago was that when you do decrease the height of the wheel then the rolling resistance is increased exponentially. So I tall wheel requires much less energy to spin than a small one.( I guess bigger is better);)

    If you look at most racing bicycles and even the new 29er mountain bikes they go with a fairly tall wheel. The only reason that my motorized bicycle is running 26 x 1.5's is because I have no suspension on my bike and I like the dampening effects that these particular wheels have. Plus there is something to be said about not having to to fix flat tires, especially rear tires on these particular types of bikes.

  18. HeadSmess

    HeadSmess Well-Known Member

    come to australia were youll find the footpath is the better option, when there is one...

    potholes? we consider ourselves lucky that theres some tarred gravel in the middle of all these mineshafts!