mwandaw

My wife and I ride our Cannondale RT1000 enthusiastically, and together we weigh about 280 lbs. I installed Continental Grand Prix 4-Season 28-622 (700x28c) on our bike about 125 miles ago. I hoped they would be half way between the Grand Prix 4000S and Gatorskins in terms of rolling resistance, weight, durability and flat resistance.

My wife and I both feel that they provide a smooth ride and low rolling resistance. That's good! However, I have a real complaint about the steering. If we go faster than "medium" through a corner, I can clearly feel that the steering angle wants to increase and the tire wants to lose traction. It's classic understeer behavior, and it's pretty scary on a tandem!

I wouldn't be surprised if understeer is normal at the limit of tandem cornering speeds, but this happens at speeds noticeably slower than what we considered normal with the four other types of tires we have had on this bike.

I wonder if these tires have a hard rubber compound, and that limits their cornering traction. I wonder if they just "scuff in" slower than usual. In fact, there is still a noticeable "bead" (mold flashing) running down the middle of the tire. Maybe that is messing up the handling.

Most of all, I wonder if anyone else has noticed this behavior, and I wonder how the tires worked out for you.

Thanks!

By the way, gracehowler has already given me some feedback in a related thread. Thanks!

Ritterview

My complaint with the 28 mm versions is that they are only 26-27 mm on the caliper. At Sea Otter, I talked to the Conti rep, who divulged that the GP 4Seasons have the same Black Chili compound as the 4000s. I think the main difference is an extra Vectran layer. My rear 4 Season was causing mystery flats, so I had to remove it. Must have been some irregularity, but I couldn't determine what it was. I think that's a fluke. The Conti 4Seasons would be the bomb if they were only 28 mm.

I have high hopes for the Conti GP4000S 28 mm, which will be out in Spring 2015. Those had better be 28 mm!

Specialized is going to release a 30 mm tire in the Roubaix Pro in 2015. That might be a comfy tire on bikes where it will fit.

Team Fab

I think understeer is inherent to tandems. But I did notice the Conti's both 4000 and Gatorskins (in 25 mm) to slide much easier than 28mm Bontrager Hard Cases( I think "Race") that we normally run for training and general riding.

That being the case I found the slides easy to control, very smooth with no sudden changes in traction. I always thought it was due to a overly soft compound. As they are probably designed for less than 250 pounds a 300 pound tandem team may be above the designed traction limits???

mibike

We use GP 4Seasons on our tandem and are very happy with them. What rim are your GP 4Seasons mounted on? I checked mine and they are 28+ to almost 30 mounted on Dyad rims (24mm). This is wider then 2 other types of 28 mm tires I checked on Dyad rims. I was also told by Conti that a GP 4Seasons is a GP4000S with the extra Vectran layer that is why I started using them.

I also have high hopes for the Conti GP4000S 28 mm. I plan to try them when they come out. They should be about 20g lighter then the 4000s based on Conti's web site. I use GP4000S tires on my single and I'm very happy with them and based on this I don't think flats will be a problem.

DubT

Will, it has been interesting following your posts. You have the Ferrari of tandem bicycles and it seems like you are tying to make it a Cadilac. The Dragonfly utilizes very stiff tubing, you may have been better served with the Tetra. Our Tetra is extremely comfortable with 25 mm Schwalbe One tires at 120 psi. No flats and great wear YMMV.

Ritterview

I don't any difference in stiffness of the tubing used in the Dragonfly and Tetra amounts to any perceptible change in compliance. I don't even know that they are different tubing, I think they are both sourced from ENVE.

A theme of my hopefully interesting posts recently is the tandem application of the surmise in cycling generally that wider tires have lower rolling resistance. For example, the recent quantitative half-bike test that showed the least rolling resistance was 28 mm. When 140 lb UCI racers are on 25 mm tires, 290 lb. tandem teams have no business on the same width.

When experiencing wider tires, it is soooo nice. Its all for the good, smoother, better grip, more confidence, keep a straighter line, less fatigue, fewer pinch flats, happier stoker, ergo, more riding. Did I mention happier stoker?

Whoever figured out that wider tires have lower rolling resistance deserves a medal. Its the greatest benefit, and at no cost! Team DubT needs to join the wider tire revolution, your stoker deserves it.

B. Carfree

I don't know who figured out that wider tires have lower rolling resistance (on real roads), but wasn't it those folks from Bicycling Quarterly who did all the testing and have been announcing it from hilltops?

Ritterview

BQ has had that graph, that half-bikes should be running like 40 psi. I don't think they've done extensive testing.

The test I had referenced above is here.

I don't understand Conti. They made enough 28 mm GP 4000s II's for Tour Magazine to test in 2013. The 28 mm comes out on top, stoking demand. Then they sit around waiting to release the 28 mm until Spring 2015, if we are lucky.

Team Fab

One thing to remember. The rolling resistance test has a stated margin of error of 10%.

I would also like to suggest that the larger tires on the same rim would be taller. This would affect the resistance if measured at the axel as the contact patch being further from the axel would have more leverage.

So maybe the lower resistance is due to a effective bigger wheel not the tire.

DubT

if I read the sidebar right the difference in watts was only 10 watts, best to worst, who but the pros are going to be able to notice that? Jens used Schwalbe track tires in his hour record run, I never did find anyplace that said what size they were. That would be good information.

Dean V

Road surface has to be factored in as well. For smooth roads and velodromes a narrow high pressure tyre is fastest. On coarser surfaces the larger tyres start looking better. The speed and weight of the team also comes into it but basically rolling resistance is a bigger factor on tandem than single as you have twice the weight and no more speed to effect the aero side of the equation.

ct-vt-trekker

We've been running GP 4 seasons for a couple of years now in 700 x 28mm. They're much better than the Bontrager hard case tires in every way. Much better road feel , better handling and less flats too.The only tire we preferred was the GP4000s but they are only available in 25mm width. But 25mm was just too small for our terrible roads. After a flat from a pothole that blew the tire completely off the rim and wrapped itself around the cassette and we found ourselves riding on a bare metal rim we decided to go back to 28mm tires. So far the GP 4 season is our number 1 choice. As soon as the GP4000s come out in 28mm we'll be trying them.

We run these at 110lbs. My stoker can tell me if they are 5lbs high or low.

reburns

I ran these tires for a while on my single bike, but was disappointed when they started to fray near the rim and eventually the brown cross hatch pattern started to delaminate from the sidewall. Has anybody else heard of this problem or did I just get some lemons? I still have one as a spare that I carry on the tandem, but I've never mounted it. Meanwhile we've been enjoying the Schwalbe Ultremo ZX on the tandem in 28mm. Much smoother than the Gatorskins for sure.

gracehowler

Reburns, yes, I have had that same delamination, usually after the tire has seen some miles and sunshine.
R

zonatandem

We are just under 250-lbtandem duo and been riding tandems (on tandem #5 now) since 1974.
Have always run narrow tires; back in the 70s we rode 27x1 1/4 or 1/8s.
Then 700x23s and now (in our 'old age': 81/79) we run 700x25s.
We are roadies and have ridden in 30-some odd states and on all sorts of road surfaces.
Definitely road surface has a big impact, but if it gets too rough riding you can bleed off some tire pressure.
We normally run 120 PSI; but stoker sometimes complains and we let out a couple PSI. We don't use a suspension seatpost and bike frame is carbon fiber.
Just our experience/input.
Rudy and Kay/zonatandem

mwandaw

Mark at Precision Tandems suggested trying 120 psi, and I did. The steering felt much better while cornering.

Now I'm hoping that over time they'll scuff in some more, and I'll feel even more confident in the tires.

When we had the Ultremo ZXs they felt great at 90 F / 100 R psi. However, despite the numbers molded into the sidewall, the Ultremos looked bigger than the 4-Seasons.

Thanks for the tips!

WillFam-Reno

So, upon your first impressions, and with the new higher pressure, which do you like better? We just changed from Hutchinson to Ultremo ZX foldable in 700 x 28c and like them so far. We are a triplet and occasional tag-a-long, so the combined weight is about 550 lbs. Tomorrow we plan on riding about 40 -50 miles on them. They sure are expensive! What was your reason for going to the 4-Seasons if you don't mind?

Enjoy.

Captain John

3rd year for us on the GP 4 seasons, agree with Mark at Precision with the 120 PSI.
rough roads around here and lots of chip n seal.
25 MPH thru a 90 degree corner at the bottom of a downhill and these tires are rock solid
good tires

mwandaw

Schwalbe Utremo ZX 28-622 (700x28c) - we started at 90 F / 100 R psi, but ended up using 100 F / 110 R psi
Advantages: excellent ride comfort; great traction & handling; low rolling resistance.
Disadvantages: wore out after just 1,200 miles; less flat resistance than we wanted.

We switched to the 4-Seasons expecting the tires would last longer and have better flat resistance than the Ultremo ZXs.

Which tire do I like better? Hmmm... the jury is still out. My impression is that the 4-Seasons have a harder rubber compound and have not yet fully broken in. There's still a mold mark down the center of both tires after more than 200 miles of riding!

Continental Grand Prix 4-Seasons 28-622 (700x28c) These are my early impressions. We started at 90 F / 100 R psi, and are now running 120 F / 130 R psi.
Advantages: good ride comfort; very low rolling resistance - we'll need more miles to form opinions about everything else!

twocicle

The appropriate PSI needed usually depends on how much air volume you achieve in your wheel setup. For example, a narrower rim (ie: 18-19mm) or thicker inner tube or rim strip will result in less air volume and therefore require a higher PSI to stabilize the tire sidewalls. At your team weight of less than 300lbs, 120psi with a 28mm tire is a bit on the high end, but could be appropriate for you depending on your wheel config. Typically one would expect 110psi to be sufficient.

I am very picky about cornering handling and ride quality. For comparison, at a team weight of ~255lbs, we run our 25mm 4-Season tires on 23mm rims at only 106psi, and 28mm at ~100psi. The ride quality is not as silky as with the Schwalbe Ultremo ZX, but the Contis are definitely more puncture proof.

We just came back from riding our coupled Calfee Tetra for 2 weeks in the Puglia, Italy region. The road surfaces on these routes were of the worst quality we have ever ridden on a tandem. On a rare occasion there was a small bit of acceptable tarmac, but typically it was what I call "bombed out, WWII crap" similar to what you would expect if doing the Paris-Roubaix race route. I had the impression the posted "bike routes" were devised by local companies trying to rent out fat tire cruiser cycles to tourists and not for true roadies. In preparation for that trip, I reinstalled the original beefy ENVE tapered fork and mounted the 28mm Conti 4-Seasons which performed excellently and we had zero issues. Both of us took a pounding over these roads, but even so, my stoker still insists she does not need a suspension post (currently using a stiff Thomson Elite and Terry Carbon Butterfly).

That said, I can't wait to remount the Schwalbe Ultremo ZX 25mm tires (and 3T Rigida fork for quicker steering) to resume riding on our typical N. American roads. I would use this setup in Switzerland and Tuscany, but do opt for wider more puncture resistant tires in areas when expecting lesser quality and/or more road debris.

mwandaw

Our 1999 Cannondale RT1000 has 17mm wheels. With many thousands of miles on them, they are very tired. The picture makes them look much nicer than they actually are.

I am definitely in the market for a used wheel set that is wider and in good shape. (Please feel free to PM me with offers!)

In addition, when I installed the 4-Season tires, I used larger inner tubes. When I have a chance, I'll try the smaller tubes that we used before.

We think the ride quality of the 4-Seasons is good, but I have to agree... the Ultremo ZXs are "silky". We liked them a lot, and puncture resistance was acceptable, but at 1,200 miles they worn out too quickly for us.

twocicle

Ok, your rim width seems to confirm a couple things I mentioned. Mainly that the skinny rim will cause the tire to assume more of a light bulb shape and therefore will need to be pumped firmer to stabilize it, and that the pinch in at the rim also reduced the total air volume you can put in the tire which again will require a higher psi to compensate.

Another point, if you run higher pressure then you reduce the tire contact patch which increases wear on that narrower strip. Conversely, using lower pressure increases contact area and therefore spreads the wear over more of the tire tread. I am seeing much better wear pattern (and tread life) on our tires since moving to wider 23mm rims, plus the ride quality is far better with lower psi.

If you are thinking of improving your wheel setup, then perhaps you could have them rebuilt with wider rims which should help solve a few issues for you.

chichi

I quit using the 28mm 4 season 4 years ago because the plys on the rear tire would move within the casing resulting in a what felt like an out of round wheel. I have been running Vittorias for the last 4 years with no problems. My shop was out of the Vitorias so I decided to give the GP's another try. Tires did the same thing they have done in the past after a few sustained climbs delaminated plys. Team weight 350 climbing hills in northern California. The GP's may work for rolling terrain or lighter teams but they have consistently failed us.

twocicle

Interesting feedback that I had not heard before. I've not had any such failures of either the 4-Season on our tandem, or the GPs on my single. Wonder if others have experienced the same, or if you think there is a particular style to your climbing that causes this issue on multiple models? Just weight & torque factors twisting the crap out of the Contis?

mwandaw

UPDATE

Now we have 300 miles on the Continental Grand Prix 4-Season tires, and I feel that the cornering performance has improved. I no longer feel that the front tire understeers when we corner at higher than "medium" speeds. I no longer feel like the steering angle wants to increase and the tire wants to lose traction. I am more confident when cornering, even though I have lowered the pressure to 115 psi.

My theory is that the rubber has become "buffed" over the past 300 miles and the tires now have better traction.

I'm guessing the tires will last a long time, because they both still have a noticeable mold line along the center of the tread.

From the start we both felt that the tires provided low rolling resistance and a relatively smooth ride. We still feel that way. Combine that with the improved cornering, and so far we happy overall with the tires.