MTB Tire Test: Maxxis Ikon eXCeption Silkworm

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Maxxis Ikon eXCeption Silkworm road bike tire on a rolling resistance test machine

The Maxxis Ikon eXCeption Silkworm 29 x 2.2 is a performance cross-country mountain bike tire with a folding bead, 120 TPI casing, and 62a rubber compound. According to Maxxis, these two combined (120 TPI + 62a Compound) results in an "eXCeption" tire. On top of that it has "Silkworm Technology" which is an "exclusive material incorporated into the casing" to increase puncture and tear resistance. Together it should result in a long lasting, low rolling resistance tire. Let's find out how fast this tire really is.

The tire is made in Taiwan and seems well made. While unpacking the tire I immediately noticed it has a very stiff tread although the side walls are quite flexible, this probably is because of the Silkworm protection under the tread. I did have an issue with the packaging, which made it unclear which tire I received. The packaging showed specifications for a 60TPI tire and nowhere did it say anything about eXception or Silkworm except for a small sticker with a part number and "120 TPI". The tire itself does have the 120 TPI and Silkworm logos so I'm sure it's the right tire.

Manufacturer Specifications

Manufacturer Specs
Brand Maxxis
Model Ikon eXCeption Silkworm
Year 2014
Supplied By Bought in store
New or Used New
Mileage 0 km
Price Range High
Buy At
Manufacturer part number TB96753400
TPI 120
Compound Exception
Bead Folding
ETRTO 57-622
Size Inch 29"
Width Inch 2.20
Specified Weight 560 grams
Max Air Pressure (psi) 65
Made In Members Only
Available Sizes 29x2.20

Maxxis Ikon eXCeption Silkworm Test Results

Maxxis Ikon eXCeption Silkworm  mountain bike tire on a rolling resistance test machine

Size, Weight, and Thickness Measurements

Size, Weight, and Thickness Measurements
Specified Weight 560 grams
Measured Weight 583 grams
Measured Width Carcass 52 mm (un-round)
Measured Width Tread 51 mm
Measured Height 53 mm (un-round)
Measured Knob Height Center 2.5 mm
Measured Knob Height Edge 3.8 mm
Measured Total Thickness Center (excluding knobs) No Data
Measured Total Thickness Sidewall Not Tested
All size measurements are taken at an air pressure of 35 psi / 2.4 bars on a 17.8 mm inner width rim.

The real measured weight is 583 grams, which is 23 grams more than specified. Volume wise it doesn't impress with a width of 52 mm and a height of 53 mm on a 17C rim which is slightly small for a 2.2 sized mountain bike tire. Knob height of the central knobs is 2.5 mm, knob height at the edge of the tire is 3.8mm. This is a typical knob height for a fast cross-country MTB tire.

Rolling Resistance Test Results

Rolling Resistance Test Results
Inner Tube Conti MTB 29 (225 gr butyl)
Rolling Resistance
55 PSI / 3.8 Bar
Members Only
Rolling Resistance
45 PSI / 3.1 Bar
Members Only
Rolling Resistance
35 PSI / 2.4 Bar
33.5 Watts
CRR: 0.01004
Rolling Resistance
25 PSI / 1.7 Bar
38.2 Watts
CRR: 0.01145
All numbers are for a single tire at a speed of 29 km/h / 18 mph and a load of 42.5 kg / 94 lbs.

Use the formula: RR (Watts) = CRR * speed (m/s) * load (N) to calculate rolling resistance at a given speed and load.

Rolling resistance is very high, I totally did not expect this from a mountain bike tire with such a fast profile. At an air pressure of 25 psi, rolling resistance is 38.2 watts. When we compare this to, for example, a Racing Ralph or Race King, Rolling resistance per tire is 15 watts higher! That's pretty insane.

Puncture Resistance Test Results

Maxxis Ikon eXCeption Silkworm  mountain bike tire on a rolling resistance test machine
Puncture Resistance Test Results (higher is better)
Total Puncture Score Tread No Data
Total Puncture Score Sidewall Members Only
Tread Puncture Force Sharp Needle 7 Points
Tread Puncture Force Blunt Needle No Data
Tread Total Tire Thickness No Data
Sidewall Puncture Force Sharp Needle Members Only
Sidewall Puncture Force Blunt Needle No Data
Sidewall Total Tire Thickness Members Only

Also not expected is the average puncture resistance. The silkworm protection doesn't give any better puncture protection than other much faster mountain bike tires. Combined with the very high rolling resistance, I was expecting a puncture resistance score of at least 10 points.

Hard Surface Static Grip Test Results

Static Grip Test Results
Wet Grip Average No Data
Wet Grip Center No Data
Wet Grip Edge No Data
Measured Knob Height Center 2.5 mm
Measured Knob Height Edge 3.8 mm
Grip in points = coefficient of friction * 100
MTB grip test rim width = 30.0 mm
Wet Grip Test and Off-Road Tires (info)


This tire doesn't impress at all. The Silkworm puncture protection doesn't bring much to the table and rolling resistance is very high for a tire with a fast profile and medium knob height. Running a pair of these tires at 25 psi/1.7 bar will cost you about 30 watts when compared to a Race King or Racing Ralph mountain bike tire, that's 15% of the power of an average cyclist vaporized!

This tire costs way too much money, you're paying premium prices while "performance" line tires from other brands are better in all respects. Don't get fooled by low rolling resistance marketing!

RATING: 1.0 / 5
Not Recommended