B1KE

Hey everyone,

I'm currently running a 30mm Specialized tire that came with my Secteur Elite. They weigh in at a hefty 440 grams each.

1. I was wondering if I switch to a tire in the 220-280 gram range how much of a noticeable improvement in speed would I see?

2. How many grams do I have to drop to see an improvement in speed?

3. How much improvement can I expect to see?

Jofu

Not an answer to your question I know (sorry!), but interestingly the 2015 Secteur Elite Double now comes with the 25mm Specialized Espoir Sport. Is your Secteur from a previous year by any chance?

Geoff

B1KE

I have a 2014 Secteur Elite Disc, it comes with 30mm Espoir Sport. It's a great tire, very durable and puncture resistant but I want to get a sportier tire.

Bah Humbug

The Grand Prix 4000S II is the typical choice for those looking for a fast tire that's still puncture-resistance. Be aware, though, that it's not a matter of the change in weight making it faster - it's about the aerodynamics and rolling resistance.

datlas 

Higher performance tires will ride better but not going to make you any faster.

B1KE

What do you mean exactly by this?

B1KE

What qualities/characteristics determine a tires rolling resistance?

Elvo

There are low rolling resistance race only light weight tires (such as Continental Supersonics) that will make you go faster at the expense of longevity and puncture protection

Bah Humbug

A car's rolling resistance? Or a bicycle's?

Either way, its about how the tire deforms as it rotates under load. Typically, higher thread count tires will have lower RR (though the GP4Ks are really 110 crossed three ways) (and latex tubes help a ton, but that's independent of tire). The relevant data is available at Slowtwitch. The fastest tire is the Continental Supersonic, or at least it was last I checked, but it has no puncture belt and very short life.

Doug28450

I think he changed the channel.

datlas 

Try some different tires and you will see.

Homebrew01

.02 mph
In other words, not enough that you can measure the difference. But you may like the feel of the ride better, or not.

B1KE

Thanks for the insight!

DaveLeeNC

I just went to one of many handy dandy bike calculators (this one at An interactive, model-based calculator of cycling power vs. speed ) and assumed the following

1) no wind
2) totally flat course except for 3000 feet of climbing at 6% grade up (in one long hill) and the same thing down (one long descent)
3) You put out a flat 200W no matter what
4) You save about a pound with the new tires and I assumed an additional savings of .001 (from .006 to .005) Crr on a tire change - no change in aerodynamics
5) Bike, rider, gear total 194 pounds (old tires)

With the old stuff your ride takes a few minutes over 3 hours. You'll save about 3 minutes with the new tires. You could do the same thing with around 1% more power output.

This is really a crude analysis, but you get the idea.

dave

gregf83 

Something wrong in your calcs I believe. There can easily be a 10-20W difference between good tires and tube vs sub-standard tires and they don't normally test 400g 30mm tires so the difference could be even higher. A 5-10% difference in power would translate to roughly 2-3% higher speed.

If you're riding with a group the primary benefit is saving power rather than speed. Saving 10-20W over the course of a 3 hr ride will make a significant difference in how you feel at the end of a ride.

DaveLeeNC

A couple things to consider here.

1) Roughly half of this proposed ride (from a time perspective) is extremely insensitive to Crr. Uphill it is almost all gravity and downhill it is almost all aerodynamics.

2) I made a very small assumption about Crr improvements as the originating post seemed focused on weight.

I don't think the issue is 'calculations' per se. But it might be assumptions.

dave

DaveLeeNC

Oops - I did make a calculation error after all. I took the square root of the speed difference to calculate the power difference. I should have squared it (as an approximation). So it would require more like a 3% power output change to get the same result. My mistake.

dave

OldsCOOL

When I ride my bike with the 27x1.25" vs the lighter (similar gearing) Cdale with 235gr 23mm tires, huge difference on hills. Around here it is a rarity to find a level piece of road. Give me lightweight everytime.

Lazyass

If you're talking about dropping @ a half pound of rolling weight (453 grams in a lb) on each wheel then you'll probably notice some difference in accelerating and even braking.

Kopsis

If you're riding at a constant speed (doesn't matter if you're climbing or in the flats), weight is weight. A gram off the wheels has the exact same effect as a gram off any other part of the bike (or the rider). Where wheel weight matters is accelerating (braking is acceleration from a physics standpoint). If your rides include lots of stops and starts or pace changes (such as racing or riding in the back of a pack), the benefit of mass reduction in the wheels/tires gets amplified. How much added benefit over just what you get from general weight reduction completely depends on the ride.

Marcus_Ti

Easier way to lose half a pound....take a trip to the crapper before a ride....same effect.

greenlight149

according to flo, saving 1000grams from the wheels (2.2 pounds) saved just 1 min 42 secs over the course of a 6 hour ride with 4600ft elevation....it might feel nicer to ride a lighter wheelset, but dont expect to notice much difference in your speed.

Homebrew01

Sounds about right.