RoadBikeRider newsletter on tire wear

The RBR newsletter today had an interesting tidbit about tire wear:

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2. Jim's Tech Talk: Tire Wear II

In newsletter No. 147, I answered a question about
why tires wear faster on the rear wheel than the front.
That brought an e-mail from Kerry Irons of Midland, MI,
who has made a hobby of studying tires for 6 years.

His findings shed valuable real-world light on why tire
treads deteriorate at different rates. So this week I'm
using my space to share his findings with you.

Kerry, a 54-year-old retired chemical engineer, has
analyzed more than 50 new and used tires. He measures
tread and sidewall thickness, and records rider weight
and miles ridden. Other roadies help by sending him
their used tires and feedback.

Kerry weighs 180 pounds and rides 6,200 miles a year.
He also tracks tire wear on the bike used by his wife,
Mary, who weighs 125.

Here's a summary of Kerry's observations:

---Tire wear is roughly linear with rider weight.

---Tire location is the major factor in tire wear.
Identical tires will have significantly different wear
front and rear, far more than can be explained by
a rider's front/rear weight distribution.

---Even after thousands of miles, front tires essentially
lose no weight due to wear, although they do thin a
little because of mechanical spreading ("cold flow")
of the rubber on the casing.

---Exception: If there is significant hard braking
(lots of steep downhills), then front tires can wear
due to power dissipation.

---Riding a tire for significant mileage on the front
and then switching it to the rear reduces its rear
mileage somewhat compared to putting a new tire
on the rear. The front tire "ages" due to environmental
exposure, resulting in about 1/3 faster wear once
mounted on the rear.

---The reason rear tires wear out so much faster is
power transmission through the tire. Riders who stand,
sprint frequently, corner hard and so on are likely to
significantly accelerate rear tire wear. It is likely
that riders who "stomp" the pedals rather than "spin"
will wear rear tires faster.

---Tires are worn out when they have lost roughly 10%
of their weight. There are variations in tire construction
that can shift rubber (and weight) to the tread or away
from it, but this general rule applies to lightweight road
tires.

---For roughly 60,000 miles, my wife and I have found
that flats spread uniformly over tire life. Our experience
shows no correlation of mileage and flats, but any given
tire flats so infrequently that the statistics are fairly sketchy.

---There is a significant difference in tire construction
philosophy. For example, Continental GP and GP 3000
sidewalls are about 0.020 inches thick, while the
Continental GS is 0.040 inches. Michelin Axial Pro
sidewalls are 0.030-0.033 inches, while the Axial Super
Comp is 0.042 inches. Some would argue that these
differences explain the "fragile sidewall" reputation that
Continentals have, though my wife and I have never
experienced a Conti sidewall failure.

---A Continental GP has 0.045-0.055 inches of tread,
while a Michelin Axial Pro has 0.030-0.040 inches. The
extra tread thickness, rather than a rubber compound
difference, explains the Conti's greater mileage.

---Within a brand, tread compound affects durability. A
Continental GP3000 has about the same tread thickness
as a Conti GP. But the GP3000 wears out significantly
faster, presumably due to much lower carbon black
content in its tread compound.

After all this, what's Kerry's tire choice? He says he
and his wife ride Continentals almost exclusively.
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All very interesting, but how about the most important piece of information --
how long did all these different tires last? If anyone knows Kerry Irons,
perhaps we could convince him to publish his findings here (or somewhere else we
can all read it).

Matt O.

In article ,
"Matt O'Toole" wrote:

The RBR newsletter today had an interesting tidbit about tire wear:

-----------------------------------------------------------------------------
2. Jim's Tech Talk: Tire Wear II


All very interesting, but how about the most important piece of information
--
how long did all these different tires last? If anyone knows Kerry Irons,
perhaps we could convince him to publish his findings here (or somewhere else
we
can all read it).

Matt O.

It would also be interesting to see mileage comparisons between
different widths of the same tire. For example, I've used both 23mm and
25mm GP 3000, and the tread on the 25mm is MUCH thinner than the 23 mm.

All very interesting, but how about the most important piece of information --
how long did all these different tires last? If anyone knows Kerry Irons,
perhaps we could convince him to publish his findings here (or somewhere else we
can all read it).

I saw that he posted more elsewhere - i HOPE he doesn't mind wider
distribution:

New tire data (23mm unless noted) Weight Tread thickness side wall
thickness
Vredestein Fortezza TriComp 262 109-115 26
Vredestein Fortezza 25 280 NA 25
Conti Grand Prix 3000 232 128-129 23
Conti Grand Prix 220-222 115-122 22
Conti GS 275 NA 40
Michelin Axial Pro ~240 NA 31
Michelin Axial Pro Winter 227 NA 31
Michelin HiLite BiSynergic 260 NA 31
Michelin HiLite Comp 20 260 106-112 46
Michelin HiLite Comp ~280 NA 39
Michelin BiSynergic ~240 NA 33
Michelin Axial SuperComp 240 NA 42
Michelin Axial Pro 225 95-99 30
IRC Paper Lite Plus NA NA 21
IRC Metro 26x1.5" 540 NA 23
Specialized Armadillo 26 380 NA 40
Panaracer Pasela Comp 26x1.25 240 NA 21
Vittoria Twin Techno Green 230 80-87 30
Vittoria Twin Techno Orange 25 (measures 23) 270 120-127 33



Clincher Tire Note mileage rider wt (lb) Wt. % Wt loss Tread thickness
Vredestein Fortezza 2 ~2000R 180 234 11 66-74
Vredestein Fort. Tri Comp 4 6420F
1950R 180 236 10 59-65
Vredestein Fortezza 25 4 900 F
1200R 180-215 255 8 47-62
Vredestein Fortezza 2 ~2000R 180 234 11 66-74
Vredestein Fortezza 25 2 ~715R 195 265 5 69-74
Vredestein Fortezza 25 2 ~1940R 175 259 8 73-82
Vredestein Fortezza 2 1400R 175 225 14 78-86
Conti Grand Prix 3000 4 5050F
1300R 180 217 6 69-77
Conti Grand Prix 3000 4 1300F
2950R 180 203 12 66-75
Conti Grand Prix 3000 4050F 180 224 3 105-110
Conti Grand Prix 3000 5,6 4000R 190 194 16 66-72
Conti Grand Prix 3000 20 2 2640R / 2350F 150 178 23 82-88
Conti Grand Prix 3000 4 3380R / 3380F 142 192 17 63-70
Conti Grand Prix 3000 4 3380R / 3380F 142 191 18 65-73
Conti Grand Prix 3000 blue 5 3380R / 3380F 142 191 18 65-73
Conti Grand Prix 3000 gray 5 3380R / 3380F 142 191 18 65-73
Conti Grand Prix 3000 blue 5 3380R / 3380F 142 191 18 65-73
Conti GP 4 9500F/ 4500R 124 198 10 70-77
Conti GP 3 5045F/ 4068R 180 192 13 71-76
Conti GP 4 6070R 185 199 10 64-78
Conti GP 4 ~ 9500R 125 194 12 63-78
Conti GP 3 ~ 9500F 125 222 0 111-120
Conti GP 4 3170F 5045R 185 191 13 68-85
Conti GS 7 ~ 1500R 190 243 12 85-90
Conti GS 7 1100R 185 235 15 68-75
Michelin Axial Pro 5,6 2100R 190 209 13 54-56
Michelin Axial Pro Winter 5,6 2000R 180 205 10 54-56
Michelin HiLite BiSynergic 4 ~2300R 150 225 13 64-67
Michelin HiLite Comp 20 4 1730R 175 250 4 73-80
Michelin HiLite Comp 2 600R 195 243 13 70-75
Michelin BiSynergic 3 7940F 185 232 3 73-81
Michelin BiSynergic 4 7940F 2230R 185 220 8 52-58
Michelin Axial SuperComp 6 2160R 175 214 11 59-65
Michelin Axial SuperComp 2,6 3540F 175 217 10 71-76
Michelin Axial Pro 1 0 n/a 225 6 95-99
Michelin Axial Pro 4,6 3850F 185 221 8 70-72
Michelin Axial Pro 20 5,6 3500R 185 190 21 52-66
IRC Paper Lite Plus 5 2000R 150 175 ? 36-51
IRC Metro 26x1.5" 2 1100R 195 535 1 102-106
Specialized Armadillo 26 2 1100R 195 350 8 72-85
Panaracer Pasela Comp 26x1.25 2 1000F / 300R 195 231 4 93-98
Vittoria Twin Techno Orange 25 (actually 23) 4 4200R 180 245 9 68-75

Tubular Tire Note mileage Size rider wt (lb) New / used wt Tread
thickness side wall thickness
Vittoria Tour TSD 1 ~ 500F 23 185 273/273 78 25
Foxonall (Clement) Citerium 2,6 1690F / 1135R ~23 160 250/246 NA NA
Clement Citerium 2 2025R ~23 160 252/235 NA NA
Clement Citerium 2 2775F / 1310R ~23 160 252/237 NA NA
Conti Sprinter 250 2,6 2475R 22 160 280/262 NA NA


Inner tube wt (gm) Thickness
Vittoria tubular inner tube 38
Michelin Ultralight tube 69 38
Michelin Airstop tube 43
Kendra tube (Nashbar ultralight) 74 41



Notes:
1 New tire.

2 Tire not worn out but significant tread wear.

3 Tire not worn out but significant aging (crazing, cuts)

4 Tire worn so that casing just showing

5 Tire worn so that casing showing extensively

6 Tread separating from casing

7 Ridden by one rider who felt it was worn out at 1500 miles, then
ridden 1100 more miles before the casing started showing through
tread..

All tires 23 mm marked size unless noted

- Michelins have significantly thicker sidewalls than Contis or
Vredesteins, while the Contis have significantly more tread rubber
than the Michelins. A new Axial Pro's tread is not much thicker than
the Conti GP when the Conti is worn out. The weight of the Michelins
is in the casing rather than the tread.

- Weight of a new Michelin BiSynergic not known (around 240 gm?). The
manufacturers listed weight for the Michelin Axial SuperComp is 240
gm.

- Inner tube thickness measurement is "double" (two layers of tube).

- F/R refers to whether the tire was used on the front or rear wheel.

- Rider weight is in pounds.

- Tire and tube weights were determined on a Mettler digital balance
accurate to 1 gm.

- Thicknesses (tread and sidewall) are in thousandths of an inch
measured with a micrometer accurate to 1 thousandth of an inch. Tread
thickness measured in the center of the tread in at least 5 locations
around the tire. Sidewall thickness measured in at least two locations
away from any lettering or labels. Due to the fact that the rubber
could be compressed, an attempt was made to "tighten" the micrometer
to the same degree (by feel) on each measurement. Variations in
"tightness" could have changed thickness measurements by 3-4
thousandths. Vredesteins have softer tread than the Michelins or
Contis, so it was harder to get consistent thickness readings.

- Michelin Airstop tube was patched, so no weight was taken.

- After extensive use on the front , tires may be cracked and crazed
with numerous tread cuts, but do not show significant thinning of the
tread or weight loss.

- Vittoria information is on a relatively low cost tubular tire
(nominal 270 gm, $25), cut open to take the measurements. There was no
visible tread wear on the ribbed center section

Observations (biases are strictly the observer's!)

1. Tire wear is roughly linear with rider weight.

2. Tire location is THE major factor in tire wear. Identical tires
significantly different wear front and rear, far more than can be
explained by F/R weight distribution. Even after thousands of miles,
front tires essentially lose no weight due to wear, although they do
thin a little due to "cold flow" of the rubber on the casing. Riding a
tire significant mileage on the front and then switching to the rear,
reduces rear mileage somewhat compared to mounting a new tire on the
rear. The front tire "ages" due to environmental exposure, resulting
in about 1/3 faster wear once mounted on the rear (see the Conti GP
with 5K miles front/4K miles rear vs 6K miles rear for a new Conti GP
on the rear, same rider).

3. The reason rear tires wear out so much faster is power transmission
through the tire. If there is significant hard braking (lots of steep
downhills) then front tires can wear due to power dissipation. Riders
who stand, sprint frequently, corner hard, etc. will likely
significantly accelerate rear tire wear. Presumably hard cornering
would wear front and rear tires roughly equally (affected by F/R
weight distribution). It is even likely that riders who "stomp" rather
than "spin" will wear rear tires faster.

4. Tires are worn out when they have lost roughly 10% of their weight.
Obviously, there are wide variations in tire construction which can
shift rubber (and weight) to the tread or away from it, but for the
lightweight road tire this general rule applies.

5. My experience (me at 180 lb. and my wife at 125 lb.) shows no
correlation of mileage and flats, but any given tire flats so
infrequently that the "statistics" are fairly sketchy. For roughly
100K miles, my wife and I have found that flats spread uniformly over
the tire life.

6. There is a significant difference in construction philosophy for
different tires. The Continental GP and GP 3000 side walls are about
0.020 inches thick , while the Conti GS are 0.040 inches. The Michelin
Axial Pro side walls are 0.030-0.033 inches, while the Axial Super
Comp are 0.042 inches. Some would argue that these differences explain
the "fragile side wall" reputation that Contis have, though my wife
and I have experienced no Conti side wall failures in over 100K "tire
miles".

7. A Conti GP has 0.045-0.055 inches of tread, while a Michelin Axial
Pro has 0.030-0.040 inches. The extra tread thickness, rather than
rubber compound differences, explains the greater mileage with the
Conti. Within a brand, tread compound does effect durability - a Conti
GP3000 has about the same tread thickness as a Conti GP, but the
GP3000 wears significantly faster, presumably due to much lower carbon
black content in the GP3000 tread compound.