The majority of 4×100mm frames available have either 190mm or 195mm spacing, which requires you to get a new boot with the same spacing. As you can see from the diagrams below, with 165mm spacing, the second wheel of a 4×100mm setup is directly under the mounting position, causing the boot to be very high up. If the spacing is changed to about 195mm, the boot can actually be below the second wheel, allowing the boot to be about 10mm lower. Being 10mm lower to the ground makes a significant difference in how the average skater can control the skate.

Below are the approximate ride heights (the distance between the ground and rear deck of the frame) of most of the frame configurations available today. The K2 frame I have has a ride height of 107mm, and 195mm spacing.

Two modifications were required to my boot to fit the 4×100mm frame; a new mounting hole had to be created, and a cavity created in the boot for the second wheel. First, a new platform 195mm away from the back mounting hole was created using epoxy and some aluminum. Next, a hole was drilled into the boot in the desired position, and a thick washer and T-nut was inserted from inside the boot. More epoxy was used to hold everything in place. I am hoping that the washer will spread the force from the T-nut over a larger area on the fiberglass / carbon fiber; thereby reducing the chance of the boot cracking.

On the K2 frame, the second wheel is 4mm higher than the front deck, so a cavity at least 4.5mm deep was required. This cavity is in the same place as the 165mm mounting slot. I did not want to destroy any chance of remounting a standard frame, so, I decided to compromise and add a 2mm spacer between the boot and frame. As a result I needed a cavity 2.5mm deep, which partially preserves the mounting slot. I then used a Dremel to create the cavity for the second wheel. Below is a cross section of the modification, and a picture of the bottom side of the modified boot.

In terms of speed I find it difficult to accelerate from a standing start, but accelerating from 25km/h to 35km/h seemed a little easier. The skates are smoother, as expected with the larger wheels. I have also had comments that my skating technique has improved and I have less of a toe-push. The slight change in style requires a bit of time for the muscles to adapt, but it should not take too long.

With all the frame options available today, it is hard to choose which one is best for you. For novice skaters, or those on a budget, a 5×80mm is still a good choice. For intermediate skaters (under a 1h50min marathon time), moving up to a 5×84mm frame may help you knock a minute or two off your marathon time. If you had no problem moving up from 5×80mm to 5×84mm, then a 5×88mm or 5×90mm frame may help you knock another minute off your marathon time. With the 88mm or 90mm frames, you do not have to invest in a new boot. If you do not like the longer frame, you may be stuck with a 5×84mm frame, or spend the money on a 4×100mm frame and a boot with the appropriate spacing. I do not recommend a 4×100mm frame with 165mm spacing because they are either too high, or have uneven wheel spacing. I am also not a fan of different size wheels for two reasons: It makes it difficult to rotate the wheels, and actual wheel size may differ by 0.5mm, which unevenly distributes your weight over the wheels, and increases overall resistance.

To keep everything in perspective, an intermediate skater going from a 5×80mm setup to a 4×100mm may improve the time by 3 to 4 minutes. Adding a 1 hour interval practice to your training each week could easily improve your marathon time by 5 minutes. Unless you are already skating 1:10 marathons, improving technique and conditioning is more important than having the latest equipment.

Keep on rolling.

Winson Chan

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