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How much of a difference does tire width make on road bike performance?

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How much of a difference does tire width make on road bike performance?

Old 10-01-19, 09:11 PM
  #101  
bobwysiwyg
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Originally Posted by NomarsGirl
I guess my point is that it is nice that we have choices. Some will choose to put on the widest tires that the bike can handle. Some will stay with the skinny, high-pressure tires because they like them or want the bike to look as close to original as possible.

I understand the principles of physics. But the optimum tire size/pressure does assume a perfect road surface and a certain level of efficiency of the rider. The pros are much more efficient than us mere mortals. A rider who is feeling sore from every bump in the road isn't going to be as efficient as one who is more comfortable on the bike. But at the same time, really big tires are just going to feel heavy and sluggish and that will wear you down too. So while you can crunch equations all day, the truth is the best tire is the one that works best for the individual rider allowing him to have his best ride (which isn't necessarily the fastest ride).
+1
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Old 10-01-19, 09:12 PM
  #102  
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Originally Posted by NomarsGirl
Isn't it great that we have more choices than ever? The C&V guys can run their 23 mm high pressure tires on their steel framed bikes to their heart's content.
And I do and at 66yo my heart if fully content with that choice.
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Old 10-02-19, 12:48 AM
  #103  
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Originally Posted by JasonD67
My old Cannondale CAAD 4 can't fit anything larger than 25's due to brake clearance issues. With most rim brake bikes 25's are going to be about the max you can fit. IMO, one of the biggest advantages of disc bikes is the ability to run wide tires.
That is too big a generalization. My bike with rim brakes (cantilevers) can take far wider than I would go (currently 32mm). For most RACE bikes the issue is the fork clearance and the popularity of short reach brakes. This is not an issue if you take wider tire possibilities into consideration before purchase. When I was last in the LBS, the majority of bikes on the floor were running 28mm tires due to the gravel/all road thing, even if all road for most is the MUP.
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Old 10-02-19, 01:01 PM
  #104  
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Originally Posted by sheddle
dude flat bar hybrids with tires wider than road bike tires are like the best selling type of bike.

at this point you're just arguing against specialization. it'd be like if I argued that touring bikes should be less good at carrying loads, or if mountain bikes should be less good on trails, or if beach cruisers should be less comfortable
I am not arguing against specialization, I just think most of us could greatly benefit from much wider tires than our road bikes offer. On the contrary, drop bar road bikes are terrific for a sprint finish and track bikes excel on the velodrome. The prevailing conditions in these two types of riding are not the same as what the overwhelming majority of us experience in our daily rides.
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Old 10-02-19, 05:38 PM
  #105  
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Originally Posted by davei1980
... drop bar road bikes are terrific for a sprint finish ...
Yes, drop bar road bikes are terrific for sprint finishes, BUT they are also terrific for riding on the road. That's why they're called road bikes, not sprint bikes, and that's why the people who ride them are referred to as roadies, not sprinters.
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Old 10-02-19, 06:15 PM
  #106  
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Originally Posted by no motor?
I've been wondering about this lately as I've switched from 26x1.5 to 26x1.9 slicks and then 26x1.95 knobbies. The narrower tires were too painful to ride and had such unpredictable handling that I switched to the 1. 9 slicks for a few weeks. A sidewall failure got me to switch back to the 1.95 knobbies (these were all old tires I had used in the past) with my commute times being about the same and some surprising readings of the speedometer when I thought I was just plodding along. The wider tires use less pressure too, now that we know lower pressures don't mean less speed does anyone know how to figure out what pressures to use? I had been using the maximum listed on the tires for both front and rear before fwiw.
I ride a hybrid comfort bike with 26" 1.95 tires I find 50 pounds of air pressure is comfortable with little rolling resistance.
I read an article once that for a MTB used for off road you can lower the pressure down to 30 pounds, without worrying about a pinched tube.
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Old 10-02-19, 07:21 PM
  #107  
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On my road bike I use 700x23s at 90F/100R. On my "flat bar gravel bike" (steel '90s MTB with rigid fork) I use 26x2 at 30F/35R. I enjoy riding both.
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Old 10-04-19, 06:27 AM
  #108  
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Originally Posted by alpharalpha
I used to have an Cannondale with 23mm tires that had great performance but was difficult riding as almost any bump/crack in the road could affect the rims. I am considering purchasing another one since I have such fond memories of that one, but am wondering how much of a performance difference I could expect if I went with 28mm instead; or could I even go as far as 32mm?
I ride a CAAD12 with 25 mm Mavic USTs. Most comfortable ride I've ever had. Also just for info:

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Old 10-05-19, 10:13 AM
  #109  
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If you want to know something, do an experiment. Ride with different width tires. A good experiment would use the same bike and completely similar tires. For example Continental GP5000 exist in 700x23, 25, 28, 32. Compass/Rene Herse tires all use the same construction, from 700x26 to 700x55. Measuring how wide the inflated tire really is on a particular rim would help. Determining equivalent inflation pressure for the different width tires would help. Comparing an overinflated 700x42 on a hybrid to a underinflated 700x23 on a race bike tells nothing.

Someone tells me they do fun bike rides on X or they go fast on X, I will believe them. Do the same thing over and over probably you get good at it. This is never a reason not to try something different.

There's a limit on what you can directly compare. A bike that will take 700x32 is likely not designed to give optimum results with 700x23. A bike designed to go fast with 700x23 will usually not take tires much wider. Do the experiment you can with what you got.

One experiment is over. It took forty years to run its course. When tires as narrow as 700x18 came out in the late 70s everybody had to have them. They were claimed to be fast. Very fast. They were OEM on touring bikes. There are still riders loyal to those skinnies, willing to ride dried out garage sale tires to have what they were taught was best. But no manufacturer is willing to make new ones. When evaluating tires try to be smarter than the 700x18 loyalists.
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Old 10-06-19, 09:10 PM
  #110  
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Hi, don't mean to beat a dead horse, but I don't think I saw anyone mention tire load sensitivity yet - only hints around it.

Here's a video from Engineering Explained:

And here's a practical example. Wider tires can cause hydroplaning for cars, but it isn't a concern for bikes.
https://www.roadandtrack.com/car-cul...res-more-grip/

Essentially, the higher the pressure on the contact patch, the less the coefficient of friction. The coefficient of friction falls logarithmically (ish) with load, until it plateaus at some point. This means that the lighter the load, and the bigger the contact patch, the higher the coefficient of friction. I believe that most people are at the "plateau" region of the graph because hydroplaning isn't an issue for us. Unfortunately, this means that there is not a significant difference in the coefficient of friction between slightly different setups. So going from a 23mm tire at 120 psi to a 25mm tire at 105psi may not yield a big difference. However, going from 23mm @ 120psi to 35mm @ 35psi would. Sure, the bike would feel different, but it would almost certainly grip harder. EDIT: But of course the #1 factor is getting tires that are sticky.

This also means that big/heavy people should run bigger tires. Someone who weighs 120lbs should not have the same size of contact patch as someone who weighs 250lbs.

Also, can we *please* stop using exceptional people who coincidentally align with our beliefs as evidence? I bet Chris Froome could beat me on a climb right now if he could spare the time, on a fixed gear bike that weighs 30 lbs. I'm not going to look at breaking all my bones as an effective training strategy or throw out my road bike. It's just a terrible logical fallacy. EDIT: Explicitly, don't use "Safa uses 23s" or "Jeff Linder doesn't ride an aero bike" as evidence.

EDIT: Another example of increased contact patch improving grip:

https://www.cycleworld.com/2019-yama...gt-first-ride/
The Yamaha Niken uses two front wheels to improve front end grip. Now, it could be that this setup doesn't actually provide more grip and this is just a marketing ploy, or that having two separate tires is important to increasing the level of grip, rather than just a fatter tire... but I don't see any reason to believe that.

Last edited by smashndash; 10-12-19 at 08:59 PM.
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Old 10-07-19, 11:53 AM
  #111  
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Originally Posted by alpharalpha
I used to have an Cannondale with 23mm tires that had great performance but was difficult riding as almost any bump/crack in the road could affect the rims. I am considering purchasing another one since I have such fond memories of that one, but am wondering how much of a performance difference I could expect if I went with 28mm instead; or could I even go as far as 32mm?

Before you go spending money on different width tires, please use the bathroom scale to see how much force the air in the tires must work against. A greater force will require a greater force upward (Newton's Laws). The force your tires will exert will be F=P*A, where P is the pressure and A is the surface area contact with the pavement. A wider tire will have a greater area and thus require less pressure to the same effect as a narrow tire with greater pressure. Assuming the same rubber compound, the wider tire will have better breaking power due to the increased surface contact, as it will start slipping after the thin tire. But since pressure usually runs lower in the wider tire, the ride will be more bouncy, which over rough pavement may be a plus, but could transfer pedaling energy into heat instead of motion.

My rule of thumb is that if your bathroom scale stops under 65 kilos (143 lbs) you have nothing to gain and much to lose by moving from 23 to 25. If you scale over 65 and less than 90 kilos (200 lbs), 25 would be a better choice. If you are above 100 kilos (220 lbs) then 28 would be much wiser.

Wider tires are being promoted as faster than thinner tires, but those arguments deeply flawed because they never factor in the weight of the cyclist, nor the aerodynamic effect of the width of the rim (they always use a rim optimized for the wider tire). But with the current obesity epidemic in the biggest market for high end bicycles, the need for wider tires is evident, especially for those potential buyers who want the very best but never stop to factor in their own weight.
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Old 10-07-19, 12:30 PM
  #112  
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I have a Giant Defy that originally came with 23MM, rode hardddddd.
Eventually went to 25's. Maxed out frame clearance with current 28's.
HAVEN'T lost much in speed, gained cornering stability, bumps are less jarring,
comfort made a BIGGGGGG difference.
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Old 10-07-19, 06:23 PM
  #113  
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''What's the first rule of holes?''

The probability of crossing a peril with sufficient ability to create a hole is directly proportional to, the last time a repair was made, cost
of the tire and the relation to leisure or expediency in the manner of travel.

Last edited by fred911; 10-07-19 at 06:26 PM. Reason: clarity
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