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From my limited experience, soft tires feel more bouncy than hard ones, with same pressure. That is, if you lift and drop front side of unloaded bike, with soft rubber on front wheel it will jump like a bouncy ball (kind of). But with hard rubber it'll jump more like badly inflated football/basketball (at low pressure) or like a sack of potatoes (at high pressure).

Other things being equal (size, tread, pressure), do you think soft rubber tire will provide better suspension than hard rubber?

EDIT: made a test with Schwalbe CX Comp (soft) vs some Vee Rubber harder compound tire (same width) - dropped front side of unloaded bike from a small height. CX Comp definitely feels more bouncy and jumps more silently. But actually maybe they bounce with same rebound, since it's hard to measure precisely.

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Folks, note that he specifically says that tire pressure is equal when making these comparisons. –  Daniel R Hicks Jul 27 at 3:08

4 Answers 4

up vote 3 down vote accepted

There are tires made out of thin layers of relatively soft rubber, and ones (usually for puncture resistance) made out of thick layers of relatively stiff (almost like plastic) rubber. At a given tire pressure, the soft tire will be "bouncier" because the softer rubber has less of a viscoelastic damping effect than the harder rubber. As a result, the softer tire will have less rolling resistance for a given tire pressure.

(This is why I prefer puncture-resistant tires that employ a Kevlar belt (eg, Forte K models) vs those (Schwalbe Marathon) that employ a thick hard rubber layer in the tread -- less rolling resistance.)

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And for those who think I do not know of which I speak, I used to test rubbers for the Air Force. –  Daniel R Hicks Jul 27 at 3:09
    
So soft compound tires have lower rolling resistance, better traction and feel more bouncy. Seems like the only downside is that they wear out faster. –  alkar Jul 27 at 11:39
    
And judging by my CX Comp, soft tires are more vulnerable to punctures and cuts. The only protection is from Kevlar Guard layer. –  alkar Jul 27 at 11:47
    
@user713303 - My experience has been that a good quality Kevlar layer provides excellent protection against punctures, with only a slight impact on rolling resistance (and weight). Perhaps the thicker tires provide more, but (for me) the difference between a flat every 4 years or every 6 is not worth the extra resistance/weight. –  Daniel R Hicks Jul 27 at 12:23

Most definitely. I have some Schwalbe Marathon Plus HS 440 - very puncture resistant tire. It is hard rubber and has a puncture insert. It is a hard tire and gives a hard ride anywhere in the pressure range. I have a softer same size less less ballistic tire on another bike and at the same pressure it is a softer ride a nicer grip. And it is not the bike - I noticed the hard ride as soon as I put the tires on the bike.

Is it a mountain bike? You want a soft ride then put some 2.2+ tubeless on it and run at 30 - 40 PSI.

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I don't think your premise is right - an overinflated tire should be bouncier and faster than an underinflated tire which should provide better shock absorption at the risk of more tire damage. A properly inflated tire should balance this out.

A softer rubber compound should mostly be for increasing grip (and many tires are made of several rubber hardnesses in order to increase longevity). A more rigid construction of the tire (i.e. the actual structure of the tire with cords and what not, and rubber) can change the ride characteristics though (presumably to be more rigid). The term "better" is a bit too subjective and one person may hate the tire which you consider to have the best suspension properties and vice versa.

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As @Batman mentions, it's more about the construction than the rubber compound, but I suppose thick MTB tyres will cushion bumps better if they are made from softer rubber.

Lightweight racing tyres tend to be thinner, especially in the sidewalls - there they are made as thin as possible because puncture resistance is not a priority. Such tyres are typically very supple, and even when inflated to high pressures (100-120 PSI) they can still feel "soft" and provide a very nice ride.

Wider tyres can also improve the suspension effect. Generally their recommended pressure range will be lower than that of an equivalent narrow tyre, because they hold a greater volume of air.

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