I need schooling on shock stroke/length again…

I have a Knolly Fugitive. It’s a cracker of a bike, but I’m getting frustrated at the near-as-damn-it 17kg weight. On that basis, and given that I already have most of the necessary parts spare, I’m going to give this kind of build a crack.

I’m scratching my head about the shock, though…

The later ‘138’ version of the Fugi I have is designed around a 185mm x 55mm shock for 138mm travel (or a 50mm for 131mm). The ‘LT’ version shown in that link used the same shock for 135mm travel (or a 50mm for 128mm).

First question:  If he’s using a 50mm stroke shock, does that mean he’s not using a 185mm length to achieve the reduction to 120mm of travel?

Second question:  For me to get 120mm at the rear (or close to it), what length and/or stroke of shock do I need to run?

Thanks!

Length of the shock doesn’t affect travel.

Rear wheel travel is calculated by shock stroke x leverage ratio.

We can work out the ratio using your numbers,

138mm from a 55mm stroke gives a ratio of ~2.51:1.

128mm from a 50mm stroke gives a ratio of ~2.56:1

So if we take a rough average of 2.53 and divide 120 by that number, you need an eye to eye length of 185mm and stroke of 47.43mm to achieve 120mm of rear wheel travel.

Approximately…

Given that metric shocks tend to come in 2.5mm increments, you might struggle with that. I guess if you can find a 185×45 and remove a spacer you might end up at 47.5mm. I have no idea if such a thing exists though.

I know for example my Float X comes at 210mm length and 55mm stroke. That can be reduced to 52.5 or 50  but that’s your lot in terms of adjustment. I’m not sure you can add more spacers to get down to 47.5.

Actually, now that I look there seem to be a few options for 185×47.5 so should be fairly easy.

Is it a trunnion or standard mount?

That kind of works, bens but doesn’t take into account that with less travel from less stroke there will be less sag when you sit on the bike and the 185 x 47.5 will give a higher BB and steeper head angle. Manufactuers that vary the travel using different shocks usually reduce both stroke and overall length on shorter travel versions so the ride height is unchanged.

Edit: I’ve just measured the shocks on the short-travel Lapierre Zesty at 185mm and the long-travel AM Zesty at 190mm. I suggest a 180 x 47.5 would be a better bet (if they exist).

Ok, that’s not too bad then – there seems to be some options in 185mm x 47.5mm with trunnion mounts.

Thanks!