I'm in the process of planning a singlespeed build, and one of the dilemmas I'm having is which tires to use, and how they affect the gearing. My goal is 73 gear inches. According to the gearing calculator I've been playing with, I can get near-identical gearing with 700x32 tires and 46x17t, and 700x37 tires and 48x18t.

Tire sizing standards seem to be a bit fluid, and I'm trying to wrap my head around the relationships between the different nominal sizes - specifically, the Schwalbe Marathons, which have "700x35C" printed on them, but also have "37-622" molded into the sidewall. From asking around, I've gathered that the inflated width on a 20mm rim is just under 35mm (which is great to know for fender/frame clearance), but what about the height, for determining gearing?

The ultimate question, though, is this: All else being equal (tire brand/model, rim size, frame, gearing, etc.), would you rather ride the bigger tires or the smaller ones, and why?

In this case, it'll be used for all-purpose riding around the Boston area, primarily on paved surfaces with varying degrees of roughness. My main bike is a geared Bianchi Volpe with 32s, and I have no complaints about those, but I'm looking at frames that allow for larger tires, and am wondering if it's worth taking advantage of this extra clearance.

Wot?

Go with 32's..

For me, for regular road riding, assuming the same tire; anything above 28 is too heavy and the extra volume is generally a waste since I don't perceive any added comfort above 28.

So I guess you could tab me as in the 32 column? I'm also not convinced you should be using tire width to fine tune gearing as I don't find that a reliable or useful indicator. I'd recommend just using the nominal size (27 inch) and staying consistent with that measurement across gearing calculations.

First, the only thing you care about for gearing calculations is the diameter or circumference, not the width.

Tires are random as heck when it comes to their labeled size vs their true size. Profiles vary too. I have Schwalbe Kojaks that are labeled 700x35. They barely measure 32mm wide, but are a true 35mm tall. I have some Specialized tires that are the opposite. They are labeled as 700x45 and they measure a full true 45mm wide, but are only 40mm tall.

Personally, I can feel a big difference with every significant increase or decrease in size. If the bike is just for putting/cruising around, bigger is better IMO. Lots more comfort, especially on rough surfaces. If you are going to be riding quick, and care about weight, keep them as small as your confort level can tolerate.

If you look around, you can find large volume tires that are pretty light too.

Would you guess, then, that the 35 Marathon, which gives both numbers, is 35 wide by 37 tall? I tend to ride as hard and fast as conditions allow, but I also have bikes equipped with rear racks, full fenders, one with a drum brake and 3-speed hubs, so I'm not really what you'd call a weight weenie.

I rode 28's most of last summer and when I switched to 23's my bike felt way quicker.

32's I guess?

When you switched tires, did you do anything about the gearing? Reducing tire size means reducing overall wheel size, which lowers your gearing a little (from 72.23 to 71.18 gear inches), with the same chainring/cog ratio...meaning, you'd theoretically be quicker off the line. What I want to know is, with the same effective gearing, what do people think of the difference in tire size?

Just go ride your bike

I have no doubt the slight reduction in gear played into it, as well as the reduced weight, but I'd also wager a lot of it was mental. I should also mention I went from a mildly treaded tire to a slick. Like Unkle Rico said, go ride your bike

I can't ride the bike until I have it, and I can't have it until I have the build specs worked out!

I tend to pick tire size and gearing independently. The only time the tire directly impacts the gearing is when I install the studded tires on the fixed-gear and drop the gearing in order to avoid a heart attack.

Here is my recommendation. This is what I do.

1. Buy the tires that you dig, or that you want to try based on whatever critera.
2. Mount the tires.
3. Measure the tire's ACTUAL circumference.
4. Based on the ACTUAL tire size, select the sprockets that will give you your desired gearing.

You'll never know if you like the tire until you try it anyway. I've had tires with "killer specs" that felt crappy. And I've had tires the "weighed a ton" but felt lively, agile and fast. In fact' the heaviest tires I have on a bike, with the THICKEST and stiffest sidewalls feels the most compliant AND the fastest. I have no idea why. And the cheapest crappiest tires I own out GRIP my expensive slicks by a wide margin. Dunno.

Definitely overthinking this.

If there weren't people out there to think about stuff like this, we'd all be riding functionally identical bikes, with the same geometry, brakes, features, etc.

Not at all.

Yes -- these people are like top tiered pro race teams where stuff like this is crucial but I doubt you are on a team like this simply because.. You wouldnt be asking us jokers these questions

So really, don't stress out so much about the difference between a 73 gear ratio with 28c vs 32c tires etc.. Yes, there will be a difference -- will you notice it? Probably not. So just pick some good tires -- get a good deal and go ride!

Let me see if I can rephrase my original question in simpler terms...because you're right, I'm not on a team, nor am I any sort of racer, but I know what I like for singlespeed gearing, and I'm trying to decide the best way to achieve it with a custom build around a stock frame.

In general, if all else was equal, would you rather run the larger or smaller version of the same brand and model of tire, each filled to its optimal pressure? Would there be a noticeable difference in handling? Would the larger one feel squishier and slower on paved roads? Would the larger size and lower pressure smooth out the rough spots and stay on the road, while the smaller one bounces around?

That's the sort of thing I want to know. As it happens, the gearing I like for singlespeed lands almost halfway between two of my most frequently-used gears on my Volpe, but I originally achieved it using different chainring and cog, and wheel sizes than what's available on that bike. So I could always just do the simple thing and use the same chainring size, and the cog halfway between the two in question. Actually, that looks like it may even give me my comfortable singlespeed gearing (within a probably-acceptable margin of error) regardless of which of the two tire sizes I choose.

Tire width has no correlation to gearing. The end.

Will a 32c tire even clear your frame? Lots of fixed gear frames don't have the clearance for tires that big generally.. I think 25-28c should probably be just fine for bombing around Boston -- I've got 25c on most of my bikes for riding here in SF, my road bike has 23c's though. The handling is good, ride isnt squishy but not crazy stiff either. I've always been told that Boston streets are crazy bad so based on THAT I'd probably rock 28c's!

Easily. I normally ride 32s, and the frames and fenders I'm looking at will handle up to 38s. Smallest I've ever ridden for any significant amount of time was 28s (with 25 front and 28 rear briefly before that), but that was a couple years ago.

Edit, just for the record: freewheel single, not fixed.

Not by itself, no...but different widths will generally mean different heights, which means a change in the diameter and circumference of the wheel, which has an effect on gearing.

Me? Bigger for sure.



Yes. Bigger tires will feel less nimble. BUT, bigger tires will have a bigger contact patch and offer increased grip in corners. (That's one reason I like big tires)

NO! Not if inflated properly.

YES! And that's one of the key advantages. Less fatigue on longer rides.

This is the tire I am putting on the Townie I am building.

700 x 45mm Gumwall. 100% Slick....no tread. It's gunna slolom like glue.

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