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  #1  
Old 07-05-2018, 11:41 AM
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MattB MattB is offline
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Tire Life / Wear Characteristics

Fellow esteemed riders, I come to you seeking feedback.

It's no secret that I run my tires until the bitter end. In some cases, this is intentional. In other cases, I've been caught off-guard finishing a trip when the cords are suddenly present. It's this situation that I'd prefer to avoid.

I bought a tread depth gauge recently, nothing expensive and scientifically accurate, but a quick, easy, and decently accurate way to gauge how much of my tire tread is remaining. Through the years I can think of at least 4 trips where I found myself in an awkward position of needing tires mid-trip. Obviously I could shoe on a new set before each trip (which I've also done), but this method ends with a bunch of half worn tires in my basement that end up being garbage, not a winning proposition either.

So, to my point, I've felt through the years that tire wear is not linear and in fact increases as you near end of life. Does anyone else out there believe the same?

In trying to research, I came across a website claiming that the rubber nearest the steel cords is in fact softer by design such that it adheres better to the cords. The same website speculated that increased flexion in the tire carcass as it thins causes a tire to wear faster as it nears end of life as well.

To set it up, I was recently preparing for a trip that I estimated would encompass 1500 miles (actual ended up being 1529). The tires that were currently mounted to my bike, a set of Pirelli Angel GT's, showed 2/32" of tread remaining at their smallest measurement (the center). I found reference online to the tire having 6/32" of usable tread depth from new (I didn't have my gauge at time of installation). Using this data, I surmised that I had approximately 1/3 of the tire's usable life remaining. As I had experienced 5,000 miles on a previous set of these tires, I took that to mean that I had approximately 1,667 miles available on the tire.

Yes, I understand that many factors come into play with wear such as riding characteristics, speed, road surface, etc. While the road surface is out of my control, I'd submit that my riding characteristics, habits, and speed are fairly consistent.

Well, as the story goes, I hit the cords about 1140 miles into the trip, not the estimated 1,667. I didn't understand this as I tend toward science and things that make sense. Coming home and researching, I found the information that I mentioned above talking about a softer compound nearest to the cords. Based on this I thought that i would alter my equation a bit by considering the final 1/32" of tread depth effectively useless. As such, the tire would have a total usable tread depth of 5/32" (6/32 - 1/32). 5,000 miles extrapolated linearly over 5/32" would come to 1,000 miles per 1/32" of tire tread for ME using Pirelli Angel GT tires, AND me only truly having 1/32" of an inch usable tread remaining as opposed to the measured 2/32".

I don't know if this is a case of my making the numbers match my experience, or if this new wear equation would provide me with a bit more predictability on tire end of life, but this revised equation comes within 100 miles of when my tires reached the cords.

So, what say ye?


PS: a shout out to my friend George_in_KG from this site. Inquiring with him, he had a rear track takeoff that we mounted to my bike to get me home where I had a new pair of Dunlop Roadsmart III's already awaiting. It was great getting to see him again and I was exceedingly happy to take this route vs paying a dealer for a new tire when I already had some awaiting 200 miles away at home.
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Old 07-05-2018, 11:53 AM
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Re: Tire Life / Wear Characteristics

Definitely can relate to the increase in flex of the tire as the rubber thins. At least on DOT trackkday/race rubber.
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Old 07-05-2018, 01:56 PM
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Re: Tire Life / Wear Characteristics

Matt:

Everything you stated may be exactly correct - which in fact is way the heck over my head. I have a much simpler way of doing it - when going on a road trip of more than say 1,000 miles I always start with new tires. The tires I took off will go back on after the road trip and I will use them locally until they are finished.

You know me and tires - I don't want them to factor in - in any way be it on a trip or the track. I like riding fast be it on the street or the track and for this rider having fresh good tires is SOP.

Tires are cheap this old body can't take much more - o if I can take a little risk out of the ride I'm going to.

Too bad you live a little too far - you would never have to buy tires - you could have all my take offs!!!
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Old 07-05-2018, 03:00 PM
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Re: Tire Life / Wear Characteristics

I definitely believe that tread life is not linear, and believe that the last bit of tread wear goes more quickly than it does on new tires. In near 50 years of riding I've now come to understand that if I look at a set of tires, and think that its about time to replace them, I should do it. I cannot recount how hard this knowledge was to come by, yet I can recall looking at a set of tires and thinking that, "Oh yeah, they're good for this trip" only to either go looking for a new tire hundreds of miles from home, or limping home with the ever nagging, paranoid thought, "Shit, am I going to make it?"

I'm too old for that now, so when I start thinking I need new tires, I go for it.
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