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I'm building a full-suspension XC bike for racing technical courses. My frame is built with a leverage ratio such that 45mm of shock stroke corresponds to 130mm of rear travel. 99% of the time, I am interested only in using the first 115mm of rear travel, and will be running a 120mm travel fork up front.

I have been considering two scenarios:

  1. Run a 40mm stroke shock to limit rear travel to 115mm travel.
  2. Run a 45mm stroke shock with higher pressure to limit effective rear travel most of the time to about 115mm, but with 15 extra mm of travel for big bumps.

I guess I'm not entirely clear on the disadvantages of running a longer stroke shock at higher pressure, if there are any.

  • Would small bump sensitivity be similar across setups #1 and #2?
  • Is he concept of "effective rear travel" (accessible travel under 99% of conditions) relevant, supposing I've carefully tuned my shock pressure?
  • Is there a kinematic advantage to running a longer stroke shock?

Thanks in advance for your thoughtful technical insights.

  • Do you want a shock absorber or a shock amplifier? – Daniel R Hicks Mar 16 at 0:43
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The stroke really makes no difference here.

You set the pressure in the shock such that a certain sized hit causes a certain amount of travel. The only difference is where a shorter travel shock will hit the bump stop, a longer travel stroke will carry on. Presuming all else the same, small bump compliance is the same, as is all shock behavior up till 40mm stroke.

For XC riding, the lower travel comes from a desire for firmer suspension, firmer suspension requires less travel, and there is no point building a bike with more travel than is needed.

A longer stroke shock may be a bit heavier, but my guess is if a model comes in both options, the difference will be the bump stop rubber, so maybe the 40mm stroke will be heavier from having a bit more rubber.

In your case, I would go shopping for the best 40mm or 45mm stroke shock I could find for my money, but I would prefer a 45mm as there is no disadvantage and you can increase travel simply by lowering shock pressure if you desire.

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