Continental Grand Prix 4000 S Tire
Since tires are the tread of a bicycle, they might have more impact on our ride than any other single component. Anyone who has ridden heavy training tires and has then swapped them out for lightweight racing tires has this sensation lodged in their memory. The training tires glued the bike to the road and made you feel inexorably slow. Racing tires add more than just zip, but a sensation of zinging along. Great tires aren't just icing on the cake of ride sensation, but much of the sensation itself.
The set of Continental Grand Prix 4000s tires we discuss in this review came with the Mavic R-Sys wheelset we tested earlier in the season. We transitioned into the GP4000s/R-Sys setup by riding a week on the R-Sys wheels with our training tires before switching to the GP4000s to try to isolate the wheel qualities from the tires.
The 4000s is the jewel of the Continental clincher line. It's made in black tread with black sidewalls and a folding Aramid bead, weighing in at 205g on Conti's spec sheet and 206g on our scale.
Our first impression was no surprise: They ride beautifully. Zippy, with an easy roll up to speed and no sensation of the tread adhering to the ground. We liked the ride, felt they handled well on turns and at speed, and after two-and-a-half months of regular riding, there's plenty of tread left on the tires.
Conti has a following for their smooth-rolling, easy-on easy-off Grand Prix tires. They're a joy to install and remove; no tools necessary for those with decent hand strength. If you own Mavic rims, the tire can quickly go on and off the rim without tools and won't blow off at any pressure. The reason for this is that both Continental and Mavic make their product to the middle of the "standard" 700c size range
The drawback of early Grand Prix iterations (we're thinking mid-1990's here) was always the sidewalls. The walls would often get destroyed before the tread was rolled off the casing. Continental was aware of this, and, over the years has changed their casing and worked on various sidewall solutions, and what you get with the 4000s is the fruits of Conti's labors. These sidewalls are a far cry from what we experienced a Grand Prix generations back.
As geeked-out as we like to get, it's hard to quantify the most important performance features of a tire: Rolling resistance and tire adhesion. We can notice gross changes, like from a training tire to a race tire, but from one race tire to another is hard and we don't have the means to do a real test of either. We contemplated riding rollers at specific tire pressures and power ranges to see if we could record a noticeable difference in speed, but decided we weren't in control of enough variables to make such a home test worthwhile. It is equally hard to figure out how well a tire grips because of the wide variables encountered on the road. We have a decent sense of how far we can go, but then the days when it feels like we're over the edge could be as a result of different tire pressure, or greater humidity, or a little gravel on the road.
We're always looking for the perfect tire. We want a light tire that has low rolling resistance, grips great, resists cuts well, lasts forever, feels good and is easy to get on and off without tools. And we want it cheap. Not that we're demanding. Everything to the limit. Unfortunately, few parts can be made with everything dialed to 11, and it's probably impossible with tires, even if price were no object. Compromises have to be made with all tires. A number of tire companies use a graphic where they create a geometric shape based on their different tire qualities and then skew the shape depending on how they have designed the tire. Continental has three qualities on their shape and claims that they try to aim for the middle. Their three things are Abrasion, Rolling Resistance, and Grip. Others add casing, pressure, bead, and more to their shape, but Conti likes to keep it simple. This effort of aiming for the middle means they'll probably never have the lightest, or most flat-proof, or lowest rolling resistance, or highest grip tire, but they'll have a tire that does everything admirably well.
They have three different casing cloths for their tire line, selecting the one appropriate for the function. Continental's finest are reserved for the finest tires. The good stuff has 110 polyamide threads per inch (TPI). The cloth is wrapped over the beads and itself so the part of the cloth under the tread is three-ply (all tires are wrapped this way). Greater TPI means the casing is more flexible, which helps lower rolling resistance and makes the tire a bit harder to flat. In addition, Continental adds a strip of a "breaker" ply under the tread. It's a swatch of Vectran fiber that makes it harder for the casing to get cut under the tread or for sharp objects to puncture through the tread and casing.
The casing and Vectran keep the tire flexible, but the rubber tread is important in both the rolling resistance and grip equations. Conti says that the 4000s is an improvement over the standard Grand Prix 4000 and Grand Prix 3000 because they improved their rubber. Far from having a mad cyclist mixing latex in a lab, Continental is a tire giant and makes tires for just about every vehicle that needs rolling rubber. The Black Chili compound that in the 4000s was developed by for Moto Gran Prix racing. They figured out a way to increase grip by milling carbon black rubber to nano-sized particles. We're told that if we could get a super-duper microscope, we'd see that even though the surface of various tires look the same to the naked eye, these tires put more rubber on the same patch of ground than regular carbon black tires thanks to the microscopic rubber pieces. Conti says they've tested this to 30% increased adhesion, 26% less rolling resistance, and 5% improved mileage over their older pre-Chili tires.
We were staring at the tread and riding and staring wondering how this tread was supposed to grip better than a traditional "slick" tread. In our riding, we didn't notice any better or worse grip. So we asked. We were told that the little side tread shapes are for show. Slicks grab better and bikes don't hydroplane, but there are people who just refuse to believe that slicks are better. So Continental puts a little side pattern on to make a good show to allay the concerns of the doubters who want tread. After riding the tires for a few months, we can see that almost all of the wear happens in the middle of the tread and very little of the side pattern gets touched.
Because the middle is where the wear is, Conti' has molded two little wear indicators into the middle of the tread. When these are gone, it's time to toss the tire. If it's hard to see by looking at the tread, you can find it by scanning the sidewall for "TWI." The marking is on both sidewalls, so it should be easy to find. Also on the sidewall is a directional arrow. Our assumption was that the arrow, when at the top of the tire, should point forward. We asked for confirmation, and found we were right, to a point. It can also read properly if it's pointing forward at the bottom of the tire. The arrow is there for the people who want such things; the tread is not directional.
The sidewall is also interesting for a few other reasons. The casing is covered by a thin strip of rubber that stops just above the bead. This might help in the prevention of the aforementioned sidewall cuts. While we did get a tire-destroying sidewall cut a few days ago, we were being deliberately careless with our riding habits. We rode over glass and rocks and whatever else was left on the road without much thought. And cuts happen.
A final thing worth mentioning on the sidewall is the recommended tire pressure. It says that 110psi is recommended and 120psi max. Tire pressure is an often-overlooked part of the ride equation and deserves more attention, though at another time. We asked our Conti rep about this, and he tells us that the 110psi is for the average 160lbs male. Lighter should go lower, heavier, higher. When we asked if Continental recommends decreasing tire pressure in the rain, we were told that a few psi might help a bit, but the pressure number was given as a compromise for all conditions and dropping the pressure too much will sacrifice ride quality without increasing traction too much. Our habit had to been to ride in the rain at the same pressure as in the dry, and doing so with this tire didn't seem to be any more of a handling problem than normal.
As fans of the "open tubular"-style of high-performance clinchers, the Continental Grand Prix 4000s was a pleasant surprise. Excellent ride quality, seemingly low rolling resistance, and long life. Even if they had disappointed, the great thing about tires is they wear out, can be replaced with something else, and the process can be repeated until the perfect tire is found.