How Much Of A Difference Does 4mm Make?
 

A few weeks ago I replaced the brakes on one of my bikes. Because I didn't do any sort of "research" or anything, the brakes didn't have the reach for 700C wheels- so I got the brilliant idea of throwing on some 27" wheels I had sitting around.

Last night I took it for a ride- and I was surprised by how much I liked the ride. I've had the bike for 3 years or so, but even though I think it's my prettiest bike- it's not my favorite riding machine. Although I replaced the brakes- the big change was going from 700C x 32 to 27 x 1 1/8.

I'm sure there's other things- the different wheels, the new tires... but something made a really positive difference in the ride of the bike, and I'm attributing it to the wheel size.

Has anyone had the same experience- going from 700C to 27" or the other way around?

I think you are making a mistake by attributing any perceived difference to the negligible difference in wheel diameter. Hubs, rims, tires, etc. are certainly the reason for the perceived difference.

Yes, LOTS of variables....Just TIRES can make a difference. I went from 27 to 700 on an old Schwinn LeTour...a BIG change, going from HEAVY chrome rims with big fat 27x1 1/4, to lighter alloy 700s with 23s...made it feel a LOT faster, lighter, more responsive, with better braking. Tires, rims, hubs, weight, stiffness, and such will make a difference. My oldest road bike with 27s feels "Softer" on the road, more of a Cadillac ride, smooths out the bumps, but not as quick in a sprint.

4 mm makes a substantial difference in the length of a person's nose. For the diameter of bike wheels? Not so much. I think you're feeling the cushy ride of the 1 1/4" tires. I like them a lot, too.

I'm curious what make and model tires you are comparing. Also, what is the real width of each tire? 27x1 1/8 is around 25mm, correct?

fify

It's the tires.

I went from a 700C x 32 to a 27 x 1 1/8, both Panaracer Pasela Tourguards. 1 1/8" is "roughly" 28mm.

So I actually went from a wider tire to a skinnier tire. If it were just a matter of width (or air volume), the larger tire should (and generally is) more plush. I *should* be experiencing a more harsh ride, correct?

Again, I'm not discounting the change is due in part to the change in hubs, rims and tires- what was on the bike were the stock Maillard rear hub laced to a Matrix rim and a Sovus front hub laced to a Sun rim. Now I've got Sanshin hubs laced to Araya rims. From what I understand- kind of a wash, quality wise.

As most people are mentioning tires as the primary focus of the ride change, and I've logically gone backwards- I should be experiencing a more harsh ride- as the other factors are the rims and hubs, why wouldn't the rim size be considered a significant factor?

Because the change is insignificant. I think you are underestimating the variables involved. Tire pressure can make a significant difference between two otherwise identical bikes.

I'm not trying to pointlessly argue- I'm genuinely interested in this.

I went from a higher volume, lower pressure tire to a lower volume, higher pressure tire.

I've experienced this with 700C x 25 to 28 and 28 to 32 and 1 1/8 to 1 1/4. In each instance- going from a smaller tire to a larger tire increases the "plushness" of the ride. I've ridden this particular bike with two different sets of 28s and 32s. I don't think it's a matter of the tire or the pressure. That leaves the hubs, rims and size.

Hey, it's all perception anyhow. It is whatever you think it is.

Or rather you think it is whatever you wanted it to be.

Without going heavily into the math of toroids, I'd think that a 27"x1-1/8" and 700x32 tire ought to have about the same air volume, or at least really close. What is it about the ride that you like now?

as well as road conditions, wind, how much sleep the rider got the night before...etc.

From a purely scientifical type of approach there is no way to prove your claim one way or the other. There are no controls, and too many variables that aren't being accounted for.

Anyone who rides regularly knows some days just feel better on the bike than others, and that's BEFORE you even begin to factor in the slight bike equipment changes. Plus, not for nothing, but if you're hoping the wheel & tire change will improve the ride, it probably will. Not that a wheel & tire upgrade isn't one of the best ways to improve a bikes performance, but you yourself admit the wheels, other than size, are equal in quality.

Point is, unless you can set up a controlled experiment, resulting in repeated results in favor of 27" vs. 700c everything else is pure speculation.

I "want" to believe that it's geometry. Subtle difference to the fork's trail characteristics? The inertia of the larger rims?

But a better hub is more likely-- I find that differences in front hubs make a big difference in the perception of the bike's ride

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27" generally looks better, as it tends to fill the forks better than 700c. And a better-looking bike rides better. Everyone here knows that. So there you are.

The plush qualities of a wide tire does not always equate to a more pleasant ride. If it did we would all be riding fat franks. There are lots of variables at play, but I'm leaning towards this being a combination of great tire size and air pressure for you.

+1 on it being the tires. And the wheels. Did you mention what the rims were in each case? I might have missed it, beer being what it is.

The 1-1/8" would have been slightly lighter, but the larger radius means more angular momentum of the wheel itself. One curious thing I believe I thought I think I felt when I switched a bike from steel to alloy rims decades ago was that though the alloy rims accelerated more easily they also has less momentum carrying the speed between pedal strokes. So it felt more responsive but not as smooth, so to speak.

I recently switched from 700c with 25s to 27" with 32s on the Bertin on the premise that the bike had been built originally for bigger tires and possibly even the larger wheel. In fact the BB was about 1cm lower than I was used to. I believe the handling improved with the whole bike lifted higher. But I haven't ridden it enough yet to be sure. What the heck, I may never be sure. It's all perception anyway.

This is true. A clean car runs so much better than it did when it was dirty. What is the name of this phenomenon?

This is a helmet thread, right?

That is the question, isn't it? What actually changed.

While I'd like to have a good, solid, quantifiable answer there other than "I kinda liked it." The truth is, I rode the bike for 3 years with 700Cs on it- and the ride of the bike did not move me. I changed to 27" Paselas and rode it around the neighborhood- just to see if it worked. A month or so later I put 27" Tourguard Paselas on it and took it for a short ride that turned into a long ride because the ride was more pleasant.

If the answer just is "the tires," and there is absolutely no apparent correlation between the wheel size and any noticeable change in the ride- then that's it. It doesn't make sense to me.

Me neither.

One thing I've noticed about older 27" rims is that every one I've encountered was single walled without eyelets. The spoke tension ends up being quite a bit lower than on a double walled rim with dual eyelets. All the 700c rims I've bought were at least double walled and felt much stiffer and more responsive.

With actual equivalent wheels in the different sizes, I don't think I'd be able to tell the difference in ride, but due to the generally lower quality 27" rim, I think I'd experience what you described.

I was just going to mention spoke tension could have a significant effect on perceived ride quality.
You beat me to it!

dang. In my post above, I backspaced over wondering aloud about spoke tension because it was pure conjecture... haven't read anything about how it affects ride quality. Shoulda trusted my instincts! (probably better I leave out my conjecture and let the more knowledgeable state facts... but this is the internet!)


I think that comfy bikes = fast bikes for most of us mortals. The more we ride, the faster we get. Clunker or not.

What about fit?

I find a big difference in my too-small 26" folder when I switch from 26"x1.75 to 26"x2.1 tires. .35" = 8.89 mm. Not sure how that quite equals out to the 8mm difference between 622 and 630 -- but I really notice the fit difference.

Survey says?