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With mountain bikes, what do you think is more efficient: highly preloading the fork and using low tire pressure or having a "bouncy" fork and hard tire pressure?

I like to have the fork with quite a high pre-load and then I set my front tire to around 1.8-2.0 Bar (around 25-30 PSI). I think this gives me good response on the fork, not wasting much energy and also gives me good control on technical zones, specially descending. I sholuld also mention that my fork (Rock Shox Tora 302) has remote lockout which I mostly use in asphalt and technically-easy zones. Bike frame is made of aluminum.

On the other hand, I see some of my colleagues having soft forks, which IMHO bounce quite a lot, and they say they inflate their tires to almost maximum pressure possible.

Also, to what extent is rebound control important here? I like it to be more absorving than bouncing.

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1 Answer

up vote 6 down vote accepted

I don't think tire pressure should be set on how cushy you want your ride (unless you have no shocks).

Tire pressure pressure and tread selection should be done based on how much traction you need. The trade off is that with more traction, you get a higher rolling resistance and you need to exert more energy to cover the same ground. This is why road bike tires look different than mountain bike tires.

  • More traction => Lower tire pressure, knobbier tiers.
  • Less traction => Higher tire pressure, smoother tires.

After you figure out what tread and tire pressure is best for you and your riding enviorment, then you can think about dialing in your fork and stiffness and damping.

Fork stiffness is somewhat subjective, but it's probably best to set it so that you only bottom out the shock when you take a pretty big hit.

The fork damping (what you call rebound) should be set so that for your weight the fork is perfectly damped. No if's and's or but's about this one, physics dictates that the best ride is one where you are neither under or over damped.

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Thanks for the answer. I care more about traction in the back wheel, I prioritize other things on the front though. Am I right that most traction comes from the back wheel? I know having the front wheel too low can slow you down too. –  Narcís Calvet Dec 13 '10 at 18:57
    
Depends on what you are doing, If you are climbing, then yes, the back wheel is where the traction comes from, but if you are descending or trying to stop, most of the required traction comes from the front wheel. I recommend setting the tire pressure in the suggested range based on weight. If you are a bigger rider, set it towards the higher end of the range. If you are a smaller rider, set it towards the lower end of the range. If you need more traction, get tires with more tread. –  Ben Dec 14 '10 at 21:56
    
Ok, I understand. I weight 77 kgs and I'm 183 cms. Anyway, I still use the front pressure at the low end as I feel it gives me much more control in technical descents. I'm doing cross country mountain bike. –  Narcís Calvet Dec 16 '10 at 18:02
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