Continental GP4000SII Tire Review Update: 700x25c vs. 700x28c

A little over a year ago, I posted about the Continental GP4000SII tires.  At the time, I was running 25c Contis.

I’m now running 28c Contis, and have several hundred miles on them.  In the realm of reviews, I stand behind what I said about the Contis last July.  They’re fantastic.  They have amazing traction under a lot of conditions, and have shown great durability and wear characteristics.  Riding here in flat/straight Illinois, I tend to wear out rear tires faster than front, so I swap front to rear about halfway through the rear tire wear, and everything goes pretty smoothly.

A big part of this post is comparing the 25c to the 28c.  You wouldn’t really think 3mm of width would make a big difference, but in reality, that 3mm is more than a 10% increase in tire width.  Particularly when mounted on a wide-ish rim, it’s noticeable.  One of the biggest advantages is that I’ve been able to significantly drop tire pressure.  I’m running in the 75psi range (a little lower in the front), to great effect.  They’re fast, grippy, roll smoothly, and there’s no palpable “bounce” from underinflation, even when out of the saddle or sprinting.  There is a significant and appreciable difference in compliance.  I still have great road “feel” and can tell what’s going on at the tires, but they really help knock the sharp corners off of road imperfections, potholes, expansion joints, and the like.

I’m still a data nerd, and hence I was worried about weight and aerodynamics.  In the realm of aerodynamics, a 23c tire would be superior to a 25 or a 28.  Candidly, I’ve run ENVE 3.4s with 20c, 23c, 25c and now 28c, and I’ve never been able to discern a difference in aerodynamics.  Headwinds suck all around.  I’m sure that over a measured distance, there is some difference in drag/wattage.  It is small enough to be inconsequential to a rider like me.  If you’re doing TTs, you may wish to reconsider.  If you’re doing crits, I tend to think that the extra grip in the corners from a 28 would outweigh any aerodynamic disadvantage.  And from what I’ve read, in the realm of aerodynamic disadvantages, carrying a bottle cage or unzipping your jersey a bit carries a greater penalty than riding 28s.

That leaves weight.  By manufacturer’s specs, the 23/25/28 are 205/225/260 grams.  I’ve found mine to be within a few grams of that, typically plus a few grams.  If you went straight from 23 to 28, you might notice an extra 110 grams of rolling mass.  That’s about a quarter of a pound.  I went from 23 to 25, and then from 25 to a new bike with 28s.  I haven’t discerned the extra rolling mass.  In that same bike jump I went to disc brakes and a different frame material.  I don’t feel that the 28s are holding me back in weight, and haven’t noticed them in an adverse way, even on hill repeats.

There’s an interesting study of rolling resistance over here, which concluded that the 28c tires save you 1-2 watts of energy in comparison to 23s at the same pressure and speed.  Candidly, I can’t sense that kind of change either.  What I do notice is the smooth ride and amazing traction.  So in conclusion, unless you’re riding a TT and need every millisecond, I’d go wide on road tires.




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