Effect of DH tire size?

Hey Lee,
Got a quick question about tire pressure. I’ve been running Kenda Blue Groove 2.7’s up front for years and wanted to switch to a 2.5 for racing. My problem arises when I try to run the 2.5 I cannot seem to find the correct pressure to work like the 2.7. My setup for the 2.7 is PSI = 18-20, for the 2.5 I’ve tried the same pressure, even a bit higher and lower but nothing works. With the 2.7 I can corner like mad, leaning the bike hard, but on the 2.5 my front washes, same trails, same riding position, same suspension setup, same everything, just different tire. What gives??? I’m at a loss! Thanks Lee.

Sincerely, David

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Hey David,

A 2.5 will never perform the same as a 2.7.

A 2.7 has:

– 17% more volume. That means more shock absorption and more wiggle, which makes more traction.

– More contact with hard surfaces.

– More float on loose surfaces. This can be either good or bad.

– In different sizes, some tires have different block sizes and spacing. The 2.7 might have a better tread pattern for your conditions.

All that said, a 2.5 has:

– Less weight.

– Less rolling resistance, especially on harder surfaces.

– More penetration in loose surfaces.

– An overall quicker/livelier feel. I run 2.5s — I can’t say they hold me back at all.

These choices usually come down to riding style. You’re apparently more comfortable on a bigger tire. I say rock it. Increased confidence counts for a lot!

— Lee

3 replies
  1. tony says:

    I don’t race, and I don’t ride a DH bike, but I have my 07 SC BLT set up with 2.5 Nevegal DH (2 ply) tires. I’ve psyched myself out once or twice b/c of weight concerns (these tires are 2 pound each! my BLT is around 35 pounds!)), and both times when I downsized to the 2.35 Nevys, my riding suffered. Sketch and uneasiness in all situations.

    I have since resolved to run the “heavy-nevy” set up from here on out, even on cross country/trail rides. The larger volume and tread definitely help the confidence on climbs and techy single track just as much as they help on the rocky, rutted downhill stuff I ride. I run them at 27 psi with tubes.

    Here’s a pic of the rear clearance:

  2. David says:

    Thanks Lee. I have one more question if you wouldn’t mind. Do I need to run different pressure in a 2.5 than a 2.7 and if so should it generally be higher or lower??

  3. leelikesbikes says:

    I guess I would run the same.

    BUT: If I ran a bigger tire on a really rocky trail, I might run it softer — for more absorption.

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