FL_Gator

Hey all, this might be an easy question but I’m just struggling with it a little.

I like to go fast and also far.. I have Roval Rapide CLX wheels (which I love) where the front rim width is 35mm. I currently run 28 GP5000s which measure 29 wide.

With all the articles and videos in the last year convincing me that 32mm is faster on normal roads.. it would also appears that the Rule of 105 supports up to 33mm wide tires on my front rim (back rim is only 29 wide but also less important in the aero calcs). Noted 32mm tires will be very slightly heavier as a non-factor.

So the question, seems like there is no penalty for 32mm tires in my setup but my old school mind struggles to accept that.. am I missing anything?

Yan 

There is a weight penalty in both the wider rims and wider tires. You cannot make something wider without it also getting heavier.

Whether or not you can gain enough advantage back via bump smoothing depends on the road.

Roads in Dubai and Shanghai are ice smooth. They have huge road budgets and they have no winter to damage roads. 32s wouldn't be faster there. A wide tire cannot absorb vibration if there is zero vibration to begin with.

genejockey 

You're already riding on 28s and your "old school mind struggles to accept" that 32s might be faster? Forgive me for finding that funny, because a REAL "old school mind" rebels at the idea of 28s!

That aside, a lot depends on how bad your roads are. The worse the pavement, the more likely it is that the 32s will be faster. On Friday, I was riding one of my favorite bikes on my usual roads. This bike is really stiff, and also can't take anything wider than 25s. I was noticing how much more jostling I was feeling from imperfections in the road, compared to another of my bikes, which runs 28s. All of that jostling has to move not only 20+ pounds of bike, but also 200+ pounds of me. By contrast, the 28s on the other bike, and possibly the frame as well, absorb all that chatter. That smoother-riding bike is also significantly faster.

FL_Gator

Haha, I hear you.. my much older bike that I now use as a trainer bike is good old 23mm, but I did convince myself to switch to 28mm many years ago which at this point feels old school 😆

I too am 200 lbs on an 18lb bike, I ride the rails to trails all over Florida so the pavement is relatively rough and worn most of the time.

eduskator

Wider tires are indeed more comfy and faster for 99% of the people. On perfect roads (which does not exist at all where I live and neither in most places around the globe except may-be Dubai where money seems to be growing in trees), narrower may not be the better option.

Wider = heavier. Also most likely less aerodynamic.

Now, would you notice a difference (would you feel or be faster?), I know not.

PeteHski

As you weigh 200lb I would just go with the 32 mm tyres. The difference in speed is negligible, but you might notice an improvement in ride quality and grip. Since you already have wide rims and clearance then there is no real downside.

genejockey 

If you want to test whether it's faster, don't do what I did: My Canyon runs Conti GP5Ks in 28, but has lots of room, so I thought I'd try 32s. I didn't want to cough up > $65/tire, so I ordered some 32mm Vittoria Corsa G2.0s from Bike Closet (I think the bought up Vittoria's stocks when the Corsa Pro was introduced last summer). Swapped them for the 28mm Contis, and pumped them up to 70/75 F/R, based on Silca's calculator. When I rode them, they felt slow, my speed was lower than usual for that bike everywhere on the route, and the average speed for that route (which I've done dozens of times) was about 0.4 mph slower than the average of all rides on it.

I was puzzled, till I looked up the rolling resistance on bicyclerollingresistance.com and saw that the Contis have 4w lower rolling resistance than the Corsas. Double that for 2 tires and you've got 8w more resistance. I checked bikecalculator.com and sure enough, 8w would work out to about that much slower average speed.

The moral of this little fable: Get the same make and model of tire, or your results will be meaningless.

BTinNYC 

Also, Conti GP 5Ks will spoil you.

FL_Gator

Great point and thanks for noting that, I plan to stick with the GP5000s but apprentice this insight.

genejockey 

The Vittorias, to give them their due, are just a bit more comfortable than most Conti offerings, though I have yet to do a direct comparison with GP5Ks. Supposedly the new Corsa Pros are The New Hotness, compared to which GP5Ks are Old And Busted, but honestly it's hard to imagine anything better than GP5Ks. If I had a lot more money, I'd run them on all my bikes. For now, it'll have to be just the Canyon and the Litespeed. Everyone else gets Corsas.

Mtracer

GCN just dropped a video where they compared the same tire model (Pirelli P Zero's I think) at three different widths (26, 30, 35 mm, I think) on the same bikes and same wheels. They also did three different power levels (100, 200, and 300 W) so a good range of speeds.

They did it on an outdoor closed track with what they said was very smooth pavement. They found no significant difference in speed. And in fact the widest 35 mm tires were the fastest, though just ever so slightly.

Of course, it's a small data set, but even they were surprised that the wider tire, at appropriately lower pressure, wasn't slower given the smoothness of the surface. But then again, even smooth pavement, isn't really that smooth.

I think they did note they thought the wider tire didn't handle crosswind as well, likely due to the airflow not being as smooth around the tire, given it was wider than the rim.

This is just another one of these types of videos I've seen lately that seem to show essentially no penalty for running wider tires. There's of course an upper limit, and as mentioned in this thread, wider rims and tires are going to be a little heavier.

I'm currently waiting until I wear out a set of GP 5000 S TR 28 mm to try some 32 mm. But these damn GP 5000's just don't want to wear out. I have 2,700+ miles on the rear tire, and the wear indicators are still very visible. I'm not sure I've ever gotten this many miles out of a rear tire. Though often it is the cuts that do them in rather than gradual wear.

FL_Gator

Yes, I saw that video as well. I think the fact that it was smooth pavement implies the advantage of the wider tire would be even greater the rougher the surface gets.
In terms of Aero penalty that really was my main question, it seems like with my 35mm wide front rim that I could go up to 33mm actual tire width without an aero penalty using the Rule of 105. Was checking here to see if I missed anything in that assumption.

Mtracer

Looks to me you'll get both better aero properties and lower rolling resistance. Win Win!

choddo

Are you doing burnouts?? I think I get 5000 miles or more out of tyres and yes it’s always the cuts which do for them even then.

eduskator

Good luck mounting them, though. What a stiff and tight tire.

At 77kg, I get 2500kms (1500mi ish) out of a Schwalbe Pro One rear tire. Front one will last 3500-4000kms (2000-2500mi ish) Top tier tires will use fast, very fast, especially on worn roads.

FL_Gator

Also note that once the middle section of the tire has a significant flat spot that although they tire may have a lot of ‘life’ left in them that the performance, and aero characteristics, are considerably reduced. So depending on how you ride and the performance you want sometimes you have to choose when to replace rather than wait for full usage. Personal preferences.

I use the blue Schwalbe tire levers that come in a three pack. They have a feature that allowed you to clip two of the levers onto the frame to hold the progress while you use the third lever to continue working the bead. These have been a total game changer for mounting GP5ks.

PeteHski

This is the best width comparison I’ve seen, but doesn’t cover aero effects.

https://www.bicyclerollingresistance...-tr-comparison

This is for the latest tubeless spec I use, but they did a comparison of the previous gen with similar results.

Rolling resistance, grip, ride comfort and puncture resistance (on tubeless) are all better on the wider versions. Aero will depend on the specific combination of tyre and rim, but I wouldn’t sweat that unless you are competing in TTs.

PeteHski

OP is already using them.

andydallas

Can we have the road crews from Dubai and Shangnhai come to Dallas for a few years,,,,

eduskator

I wrote good luck mounting them, not good luck using them.

genejockey 

Find a patch of broken glass?

eduskator

Not being able to get through a tire is a good problem. I'd touch wood if I was him! I would be more than happy to get 2700mi on a rear tire. That guy must be very light and must ride on close to perfect pavement.

genejockey 

It's funny - mostly I have no trouble mounting and removing GP5Ks from either the DT Swiss or Fulcrum Racing 4 rims without tools, but I got a set of Fulcrum 600s and they were sheer hell. Weird.

genejockey 

I got pretty near that out of at least one GP5K. Most of that was on the front, though. The rear got a cut on it that left me not trusting it at about 1500 miles, so it got consigned to trainer duty, and I swapped the front to the back and mounted the new one on the front.

PeteHski

Yeah they mount quite easily on my DT Swiss rims too.