Nice analysis, Jim. It would be interesting to ride the tires until they fray to see how long they would go, but I tend to replace tires on my cars and bikes before I need to. I think the newer tires are safer, it gives me peace of mind, and it's a small luxury that I can indulge in. Kind of like buying new sneakers before your old ones are worn out. This also offsets other riskier, even dumber, behaviors that I engage in.
Thanks for the post. Richard On Nov 14, 4:57 pm, CycloFiend <cyclofi...@earthlink.net> wrote: > on 11/14/09 12:50 PM, R Gonet at richard.go...@earthlink.net wrote: > > > I just checked my 2-year-old Jack Browns and they have that same split > > all the way around, though not as bad looking as the much older Pasela > > tan wall. The split appears to be in the outer gum wall, if that's > > the correct term, and doesn't look like it's penetrated into the woven > > layers below. I don't know if this is a safety issue or not. I've > > never heard of a tire failing at that point before, but confess to > > little knowledge on the subject. > > > By the way, it's very easy to check your tires without removing them. > > Just deflate them all the way and push the tire bead away from the > > rim, working your way around the tire to inspect the circumference > > visually. > > > Is there anybody out there who has some knowledge in this area who has > > an opinion on the safety issue? > > Hey. It's the internet. I'll hazard a guess... > > If you work from the outside in, the tire layers consist of "contact" > material (the black part of a skinwall), The underlayer (the skinwall), the > thread/casing, and a thinner layer. > > AASHTA -http://www.sheldonbrown.com/tires.html > > In the photo that David E shared > -http://www.flickr.com/photos/cyclotourist/4103817724/ > > I notice two things - first, the cracking parrallel to the rim, second the > whitish "fold marks" from running at relatively low inflation. Overall, the > sidewall looks pretty dried out - certainly drier than my tires. > > David rides in an area which has consistently high ambient temps, which I've > always found to degrade tires quickly. My experience is that the > skinwalls/sidewalls go first. > > If those were my tires (and lemme just say that I may have a higher > tolerance for risk than others here, and if you base your actions on my > opinions, I can't take liability for it....) I'd run 'em until I start to > see the beginning hints of threads fraying through. But, I'm also just odd > enough to want to see how they begin to fail. > > If the whole sidewall is cracking, I'd replace the tire. This is how you > often find old tires on garage sale bikes - unused tread but brittle, almost > "varnished" looking sidewalls. But, if the sidewall is still relatively > supple and elastic, I'd run them for a while yet. > > IF I could see through to black tube anywhere when they are inflated, I'd > pull 'em, cut the bead with a tin snip and not use them. > > Back to the photo - > The threads still have to fail, and the thread casing/underlayer in general > is probably a bit thicker than the skinwall. The threads are probably more > resistant to heat damage than the surrounding rubber composite. > > I think what may be happening is the combination of running larger volume > tires at low pressures, while the sidewall itself is drying out a bit > quicker than average. That big footprint of the tire tends to stay stuck, > while you and the bike can move quite a bit side-to-side. I would tend to > think that's why you are seeing cracking like that. > > Just one other semi-unrelated data point - > Riding with a canti brake pad out of alignment, I cooked through a brand new > WTB Velociraptor rear tire in under an hour, and the first half was > climbing. There's not a lot of material there. You might check to make sure > the edge of the pad isn't off the edge of the rim, though David's doesn't > appear to have done so. > > One more thought - > If the underlayer is really dried out, there is a possibility of the black > layer delaminating. (Kinda like a retread auto tire failure). I've > experienced this with a Specialized road tire (can't remember the name - > back in the later 90's) that used a dual durometer compound. But, even that > was happening slowly enough that I noticed it between rides. > > Hope that helps. > > - Jim "who just took his Pasela 32's outside and looke at them under strong > light and cleaned glasses..." > > -- > Jim Edgar > cyclofi...@earthlink.net > > "One Cog - Zero Excuses" L/S T-shirt - Now > availablehttp://www.cyclofiend.com/stuff > > Cyclofiend Bicycle Photo Galleries -http://www.cyclofiend.com > Current Classics - Cross Bikes > Singlespeed - Working Bikes > > Send In Your Photos! - Here's how:http://www.cyclofiend.com/guidelines --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bunch@googlegroups.com To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en -~----------~----~----~----~------~----~------~--~---
