ICE front suspension modification

Since I’m not that heavy (65-68kg) I found the front suspension of my ICE Sprint fairy harsh and thought of some options to get the stock elastomeres a bit softer and more responsive. Here is the original ICE Trikes front elastomere replacement manual with lots of images (PDF download)

ICE front suspension mod Mk I:
When you install a new set of elastomeres they fit fairly tight but after about 1000km of use I noticed the urethane elastomeres shrink some 3-4mm in length from the constant pounding of the suspension resulting in some slack in the front suspension.

ICE front suspension elastomere mod mkI

To get rid of the slack I inserted a 4mm thick rubber washer/water tab gasket with a 15mm outer diameter from the hardware store on top of each elastomere. The slack was gone and the suspension felt slightly softer absorbing small high frequency road shocks noticeably better. That was a start in the right direction but still not good enough.

ICE front suspension mod Mk II:
A couple of weeks ago a used set of medium hard elastomeres fell into my hands again and after some thinking how to improve the front suspension I simply drilled a hole with a 6mm (1/4″) drill through the center of the upper third of the elastomere. To get the hole right in center I used a 2.5mm (3/32″) drill for pre-drilling, then a 4mm drill and finally the 6mm drill. The resulting hole in the elastomere is about 5mm in diameter.

ICE front suspension elastomere mod mkII

The center hole in the elastomere together with the rubber washer resulted in a much more responsive but still stiff and ‘sporty’ suspension. Small to medium road blemishes get smoothed out now. Accidentally hitting a pod hole at some speed isn’t feeling like a hard blow that’s jarring the front of the trike anymore but is dampened to a comfortable thump.
Running over cobblestone at 30km/h isn’t the nerve and teeth rattling experience it used to be at 20km/h. While I normally kept the pressure of the front Marathon 20×1.5 at 3 to 3.5bar for comfort I can use 4bar now and still get better traction cornering fast on asphalt.

ICE front suspension mod Mk III:
Since I got quite a fine working front suspension with the Mk II mod I knew I was on the right track. To soften the medium hard elastomeres even further I took the ‘new’ set and first drilled a 3.2mm (1/8″) drill trough the whole length of the elastomere. While I got quite a long 3.2mm drill it seemed wiser to drill into the elastomere from both sides to keep the hole fairly central.
After that I used a 6.2mm (1/4″) subland twist drill to widen the hole in the upper third of the elastomeres. Any 5mm to 6.5mm drill will do the trick as well.

The right diameter of drill will depend on your weight. If you weight more than 70kg start with a smaller drill. Widening the hole to further soften the elastomeres is easy. If you make your elastomere too soft you may have to start with a new set.

ICE front suspension elastomere mod mkIII

On my test run with the freshly modded elastomeres and new rubber washers installed at first I couldn’t feel any big difference. Now 300km later the ‘Mk III mod’ definitely feels like an improvement.
When cornering sharply the curve outward side suspension will sag a few millimeters but it’s barely noticeable. Hitting pod holes at speed is further dampened. While I raised the pressure at the front wheels to 5bar the Marathons still seem to have better grip in corners.

For my weight and riding style meddling with the front elastomeres was a full success. My Sprint FS 26 is a different trike now.
The front suspension is way more responsive, dampens road irregularity better and when accidentally hitting a pothole does a better job keeping the worst blows off my trike and body. I have to see how the drilled elastomeres will hold up in the long run. If they don’t break, my front suspension is set up for good.

Update 2013.06.18
ICE front suspension mod Mk IV:
I haven’t measured them but after nearly 1000km both modded suspension elastomeres seem to have shrunk some millimeter more and both elastomeres slipped out of the lower suspension lever, piercing the rubber bellows in the process. 😦

Maybe only the rubber washers on top of the elastomeres just settled to the half dome-shaped end of the suspension housing and for that reason the suspension lost enough tension to allow the elastomeres to slip out when dealing with a good blow.
Anyway since I’m crossing half a dozen rail tracks in the streets on my commute every day, the front suspension has to frequently deal with some serious pounding…

Fortunately the fix was rather easy:
A short 5mm grub screw with a cylindrical part screwed in each elastomere, now let the elastomeres click positively in the existing hole in the lower suspension lever. To get a bit more pressure onto the elastomeres I inserted an other 4mm rubber washer with a smaller 10mm diameter on top of the 15mm rubber washer. Now the smaller rubber washer fits better in the half dome-shaped end inside the suspension housing. Both rubber washers provide enough tension to keep the elastomeres in place and the grub screws make it nearly impossible for the elastomeres to slip out again.

The suspension is a little bit more firm now. When cornering at speed the tiny sag of the curve outward suspension isn’t noticeable anymore.

Update 2013.07.01
I now have 795km on the ICE front suspension with Mk IV mod and it’s still doing fine.

Update 2013.09.12
About 3165km on the elastomeres of suspension mod Mk III and 2187km since the little update to Mk IV. A bit of sag is back when cornering hard but that doesn’t bother me.

Update 2013.11.16
An other 1100km later and since I reinstalled and changed the front fenders for a tighter fit around the tyres, the suspension sag when cornering got more noticable. I changed the rubber washers but they are just up not to the task for more than 500km or so.
I finally took the rubber out and installed 50mm long M6 carriage bolts upside down on top of the elastomeres instead. That would be suspension mod MK V…

Schlossschraube

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