|do older tires lose their tackiness?||tarwheel|
Dec 2, 2003 6:39 AM
|I'm still trying to determine the cause my crash reported on the General board. All signs seem to point toward the tires. I had just installed some green Michelin Axial Pros on my red bike for the Christmas season. Talk about ridiculous. The green Michis were some I bought a while back and removed after a few hundred miles because I got tired of the color. They had plenty of wear left on them, but they had been hanging on my garage wall for about a year. I thought the green tires on my red bike would be kind of funny to use during the Christmas season. |
The crash happened when my bike slid out on a 90-degree corner on a neighborhood street. I was going slightly downhill about 20 mph at the time. I've taken this particular corner at much faster speeds, although there was a minivan in the other lane so I had to cut it a little closer than usual. My bike slid out so fast that I hit the ground before I knew what was happening. I hit the ground on my right shoulder, hip and head. Fortunately I always wear a helmet and it protected my head well. I did get some nasty scrapes and road rash on my hip, knees, elbows and hands.
I looked at the pavement after crashing and did not see any sand or gravel that could have caused me to slide. The rear tire has a obvious scrape on the sidewall where it slid out. What I'm wondering is: Can older tires develop lose their tackiness after sitting around a while? I am hesitant to use these tires any more, but it seems ridiculous to just toss a set of tires that have lots of wear left on them. Perhaps I just need to lightly sandpaper the tread to restore it. I had ridden only about 2-3 miles when I crashed, so the tires didn't have much time on the road. The road was dry and the temperature was about 60 at the time.
Dec 2, 2003 8:19 AM
|I think you may have taken the turn poorly or hit a slick or sandy patch, causing you to lose it. It only takes a little bit, especially in a turn and then it can be hard to recover.
Consider yourself lucky how long you've been riding without a major crash up until now. Crashes happen eventually.
Its your call on the tires. If you decide to keep them, inspect and clean the entire exterior rubber surface with soap and water to get any residual oil off the tread and sidewall. Try them out for a few miles. Take a few turns slowly in a clean and dry parking lot and see how they do.
Dec 2, 2003 10:42 AM
|I had a similar accident, though at lower speeds and with much older tires. I had a wheelset with some older Tiogas mounted - Tioga Proline F's. A standard 23c, knurled tread tire.
The day was damp, and the corner was right next to a Greyhound depot, so there's a good chance the roadway was covered in diesel soot, which is notoriously slippery and fairly invisible.
I didn't go down quite as fast as you - I knew it was coming, but couldn't correct, and smacked my hip pretty hard. Got up, kept riding, but I tossed those tires that afternoon.
Granted, these were old, though, and I think were more suited for dry roads and warmer temps. The Axials are much more current, and the silicium tread should stay flexible as well as carbon black rubber, if not better.
I'd suspect, in this order, oil on the road, or plasticizers coming up out of the tread.
Chances are there was something on the road itself - it may or may not be visible, and even something like cars burning oil could do it. Remember, your contact patch is a couple of fingers in size.
It's slightly possible that the long period of disuse let some excess plasticizers (these are oils added to increase treadlife and resistance to drying out) come to the surface. The fact that you hadn't ridden very far, and that it was a sharp corner, lend this some credence.
If it were me, I'd wash the tires with some fairly soapy water, rinse well, and ride them as usual. They deserve to be worn out.
However, if you don't trust them, toss them. Better to spend a little extra on fresh tires than to lose confidence.
|Two possibilities||Kerry Irons|
Dec 2, 2003 5:40 PM
|Yes, a tire's rubber can oxidize and harden and therefore be less grippy. How were these tires stored? In a cool, dry basement or in a hot, humid garage? A second possibility is just plain dust collected in storage. The equivalent of coating your tires with talcum powder. While the effect wouldn't last long, it certainly could make the tires slippery for a few miles or more.|
Dec 5, 2003 8:14 AM
|Sorry for taking so long to respond. I've been out of town on business for 3 days. The tires were stored in my garage, just hanging from a pegboard unfolded. The tread definitely seems slicker and harder than on other newer tires I've got. My garage is not insulated and gets pretty hot in summer and cold in winter, but it's dry. I would think any dust on the tires would have worn off as I had ridden about 3 miles on pavement when I crashed.|
|not sure about the tires, but I'd guess they're fine||desmo|
Dec 2, 2003 6:04 PM
|I had a very similar fall. 90 degree flat corner, one I drill all the time at high speed. Came in a little too hot and was going wide, put more lean in to tighten up (motorcycle instincts!), and was on the ground hard before I knew it. The tiny contact patch of a bicycle tire is pretty unforgiving. As soon as the front tire was past it's adhesion point it was all over in a heartbeat. I'm guessing when you tried to correct your line because of the van the same thing happened, 20mph is plenty fast enough to dump you without warning. Oh, I did bust my collar bone and knew it.|
|Yes, I beleive they DO become harder with age||RickC5|
Dec 3, 2003 3:17 PM
|My reasoning is this: In a recent copy of Road & Track, a question was raised regarding the traction of older tires. The finding was that after several years (5 to 8), auto tires get noticeably harder than when new. Along with the increase in hardness came a noticeable decrease in traction. The outcome was that if an car owner does not wear out their tires (seldom-driven collector car?) in about eight years, they SHOULD replace the tires to ensure adequate traction and stiction. This info supposedly came from tire manufacturers.
Given that bicycle tires have less "added ingredients" than car tires (more like natural rubber) to assist in the aging process, it is sure possible that bike tires will lose traction and stiction over time, just like cars tires do. OTOH, it used to be very common practice to "age" sew-up bike tires for about a year before using them. Sadly, I don't recall why this was such a good thing to do.
All that being said, I somehow doubt that you would encounter such a dramatic loss of traction after only a year. I imagine it depends on the composition of the tire(s), how well they age, and what happens to those specific tires during the aging process. I would also imagine that one would see marked differences between different brands of tires.
It would be interesting if someone (like a bike magazine) would conduct a study on this topic. I for one, would really be interested in the results.
|agree; they definitely get harder with age||DougSloan|
Dec 4, 2003 10:14 AM
|What I read is that they off-gas some of their component chemicals, and this leaves the resulting tire harder. Every heat cycle can harden tires, too, but probably not a significant issue with bicycle tires (with road racing/autocross tires, it's a huge issue). Ultra violet radiation can harm tires, too.
Yes, in the old days, we intentionally "aged" tires to harden the rubber so we'd get fewer flats.
Some tires age more than others. I noticed that Michelin Axial Pros got a glaze after a year or so. More natural rubber tires don't seem to be as bad.