33.3% grade Climb with shocking result!

[MuniAddict]

The steepest hill in Los Angeles County, and one of the steepest streets in the country, is located in San Pedro, Ca, at the corner of W28th street & Peck. The length of this 33.3% grade is only 75 feet long, compared to the famous Fargo street which is 500+ feet in length, and rated at 33% grade.

I decided to ride this slightly steeper hill, for a couple reasons. First, it’s much closer to my home base and, Because it’s only 75 feet long, I could set up my video cam at the top of the hill, and film myself riding from bottom to top, without ever being so far away that you’d barely be able to see me, like my first video from Fargo.

So today, after a pretty taxing 10 Mile MUni yesterday, I decided to see how many continuous climbs I could do. I would have to do seven non-stop climbs in a row (plus the downs!) to equal the distance of just one climb up Fargo street!

This is actually more taxing than one continuous climb up, since I would have to turn around after each climb, and go back down and do it over and over and over again! The ride down takes a toll in its own way, even with the aid of a brake, which was squealing like a stuck pig, and didn't help matters, lol!

Well, my attempt was cut short by what sounded like a ear splitting SHOTGUN BLAST! But I shall return! (With extra provisions! )

YouTube - Catastrophic failure like...

[Dane M]

Aw bummer! Do you know what caused the blowout?

[JacobSpera]

ive had that happen with a hookworm.

Haha i was in shorts and i didnt even know what happened until my tire was flat. Needless to say i was heart broken until i got another tire

[MuniAddict]

Originally Posted by Dane M

Aw bummer! Do you know what caused the blowout?

I think the tire may have overheated from the brake squealing so badly against the rim, (going back down) which was flexing really bad! I'm having my LBS rebuild the wheel again using the original, wider drilled kh rim. It's only 3oz heavier, and much more stable and doesn't flex, and braking is smooth and sure. I did a test ride at this same hill the other day, about 4 times, with kh rim setup (before rebuilding with this much narrower rim) and didn't have any problems.

The only reason I decided to change rims was because the kh rim had a bad flat spot in it, plus we thought it would be a lot lighter...it wasn't! But my LBS will now pound out the flat spot and it should be good to go.

Originally Posted by JacobSpera

ive had that happen with a hookworm.

Haha i was in shorts and i didnt even know what happened until my tire was flat. Needless to say i was heart broken until i got another tire

I've never experienced anything like that before on a uni, and the last time I heard such a sound was at the Long Beach marathon, when two ppl on a tandem bike suffered a blowout less than 1/4 mile from the finish line! And they were running tubeless!

[Xyphota]

Are you sure your rim just wasn't out of true? Working at a LBS, I don't think the rim flexes as much as you think. The spokes cause pressure to be distributed equally around the rim. Haha, just sayin. What kind of rim was it?

[MuniAddict]

Originally Posted by Xyphota

Are you sure your rim just wasn't out of true? Working at a LBS, I don't think the rim flexes as much as you think. The spokes cause pressure to be distributed equally around the rim. Haha, just sayin. What kind of rim was it?

The wheel had just been built and was perfectly true. It was a high end bmx rim. The spokes looked almost "bent" at a pretty severe angle out of the nipples, in order for them to angle out to the hub flanges. I think this rim was made for much narrower hubs and the spoke eyelets seem too small as to allow the spokes to angle out much.

There's a 24" bmx bike at my LBS with the exact same rims and kenda tire, but the hubs are a good 1-1.5" narrower than my nimbus isis hub. But I don't think that was a contributing factor to the blowout. But the rim was as true as could be. I think the fact that the tire blew off the rim was likely because it is a folding bead and not wire, which would make the sidewall much more stable, imo.

I did find another option for a lighweight 24" tire that does have a steel bead. It's almost as light as the Kenda. But either way, blowouts like that should not happen if your riding on pavement and not doing drops. But then again, it is under a lot of stress when climbing hills like this!

[MuniAddict]

I think this rim was made by a Russian guy name Vladamir "Popoff"!

After yesterday's massive and LOUD blowout, my LBS thought that the psi was probably too low and thus blew off the rim. The folding bead tire is rated at 40-65psi, and we had 55psi in it. So They took the same size and tread design kenda tire off one of their 24" bmx bikes, but this one has a STEEL bead.

So this time we figured the tire would be more stable, and they recommended max psi of 65. Wheel was again perfectly true and off I went to try another, slightly less steep hill. Well, about 5 revs into my second ascent, BANG! Another massive blowout!

So I went back to my LBS and we agree that the RIM they were using was too narrow, and that the downward thrust of each half rev was causing so much friction and pressure on the wheel, and also heating it up to the point of it blowing off.

So they are rebuilding the wheel again with my original kh drilled MUni rim. This was the original setup using the folding bead tire, and it was stable, hill climb after hill climb. Oh well, I'll test it again tomorrow and make darn sure it holds!

First ascent went fine:


The guy in back of me almost jumped out of his shoes when it blew!

[tholub]

Your tire is probably damaged at this point; the force of a big blowout like that can knock the tire out of round, and lead to more blowouts.

[Dane M]

2 blowouts in 2 days, and never had one before this right? Sounds like you're set to not have one for a long time after this haha.

[MuniAddict]

Originally Posted by tholub

Your tire is probably damaged at this point; the force of a big blowout like that can knock the tire out of round, and lead to more blowouts.

Nope. This was a fresh, brand new tire, with a wire bead.

[MuniAddict]

Originally Posted by Dane M

2 blowouts in 2 days, and never had one before this right? Sounds like you're set to not have one for a long time after this haha.

Yeah, hopefully the third time will be the charm! My LBS and I feel that the rim was the issue, and I will know tomorrow when I get it back with kh rim and fresh tire. I feel very confident that the problem will be solved once and for all! And if it does happen again, then I would say, without doubt, that this particular *tire* was the culprit! (I have been reading reviews from ppl who have used this kenda tire, and the pop-off issue is not uncommon!)

[MuniAddict]

Second day, second massive blowout fail! With new wire bead tire, tube, perfectly trued wheel, and max psi as recommended by LBS.

YouTube - Another one Bites the Dust!...

[JacobSpera]

what was the width of the rim?

I was using a 47mm rim when my tire blew up but i personally think it was a faulty tire

[MuniAddict]

Originally Posted by JacobSpera

what was the width of the rim?

I was using a 47mm rim when my tire blew up but i personally think it was a faulty tire

I've been riding over 5 years, almost daily, and have done 6 foot drops and all manner of extreme riding, and NEVER had a tire blowout. And even with the lighter, folding bead version of this Kenda 24x2.1 tire...on my KH MUni rim, there was no problem.

Only when we built the wheel with this narrower bmx rim did these blowouts occur...with *both* folding bead and wire bead tires, and wheel perfectly true. As I mentioned, I firmly believe that the *rim* is too narrow, to support the extra down force thrust of climbing such steep inclines. My LBS also thinks that the rim could be defective, and/or the rim sides are not holding the tire well. I also thing that the tire and tube probably heat up significantly from the friction, expand and BLAMMO!

[Dane M]

You're just so extreme, these tires can't handle you!