ghostm42

Hi,

I'm new here, but I've been reading several of the archived threads and have learned quite a bit. I recently purchased a bike off CL - a chromoly Miyata SportCross hybrid (I believe it's the 1991 model after flipping through the Miyata catalog). Everything on the bike is original, including the tires. The tires are advertised as 700x35c.

The tire says "37-622 (700x35c)". This is the first point of confusion. Based on Sheldon Brown's tiring sizing page, I thought 700x35c would be called 35-622, not 37-622. What's the difference?

Next, I removed the tire and tube. The tube and rim strip actually say "28 x 1 5/8 x 1 3/8". I don't see such a fractional number on Sheldon Brown's page, though I do see a "28 x 1 5/8 x 1 1/4" that he says is "Northern European designation for the 622 mm (700 C) size". I'm not sure how this corresponds.

The real purpose of this exercise is to determine the thinnest tires the rim will accommodate. The inner width measures 17mm, so, again, based on Sheldon Brown's page, it sounds like I can put 700x25c or 700x28c tires on this. Is this correct? Also, will I notice any appreciable difference by changing from 35c to 28c tires?

Thanks for any help.

Ref: https://www.sheldonbrown.com/tire-sizing.html

RonH

bump

Retro Grouch 

I'm only about 90% confident in this answer: I think the first number is the outside tread width measurement, in other words, across the knobs. 35 mm is width of the actual carcass. One is important for determining if the tire will fit the bike frame, the other for fitting the rim.

A 28 mm tire will allow you to use more air pressure without blowing the tire off of the rim. That, in turn, will give you a little less rolling resistance at the expense of ride comfort.

HillRider

The actual and nominal width of bike tires don't always correspond and there is quite a bit of variation. So, the 700x37 and 700x35 designations on the same tire, while confusing, are not unusual. The difference is insignificant.

The "28" is an obsolete designation. Bike tubes are pretty tolerant and both 700c (622) and 27" (630) wheels use the same tubes. Tubes do vary in how wide a tire they are intended for and you will see packages marked things like 700x23 to 28 (27"x 1"- 1-1/8") or 700x 25 to 32.
Even then there is a fair bit of interchangability.

Your rims can easily take 700x25 tires and even 700x23 if you wish. Rims are also pretty tolerant of tire width.

Al1943

700 X 25 tires would be a good choice on your hybrid if you plan to stay on pavement. 700 X 28 would be better if you expect to ride fine gravel or dirt as well as pavement.

garage sale GT

Unless you currently run 35mm Panaracer Paselas you will experience a difference based on the different construction of the tire as well as the width. A finer sidewall and a thinner tread will contribute to reduced rolling resistance. However, the sidewalls can be a bit prone to damage if you ride through deep gravel or brush against broken pavement edges with them.

DieselDan

Usually I wouldn't go narrower then 28mm with a hybrid, but 17mm wide rims tells me you can go all the way down to 23mm.

Grand Bois

I wouldn't go narrower than 28c. It's a good compromise width. I have that size on most of my bikes, including the one with tubulars.

noglider 

28 is my favorite width. Jobst Brandt's measurements showed him that narrower tires have GREATER rolling resistance. They sure do ride harder, too.

10 Wheels

I ride with 700 X 20's to 700 X 35's

700 X 28's are my favorite size.

ghostm42

Thanks everyone. This was very informative. I will probably replace these tires with 700x28c based on all the recommendations. I will only be biking in paved roads either in NYC or Boston.

Kimmo

O_o

Linkage?

Panthers007

I run Rivendell Roughy Toughy's - made by Panaracer - in what they call 700 X 27C on my hybrid. They have a nice 2mm Kevlar belt, yet low rolling-resistance and are very nimble. I highly recommend them.

noglider 

https://lmgtfy.com/?q=jobst+brandt+ro...sistance+tests

jack002

Gee, someone should tell bike racers this.

Al1943

???
I've read the information and reviewed the data on Brandt's chart and what it says to me is:

1) rolling resistance decreases as pressure increases

2) smaller cross-section tires generally have less rolling resistance than large cross-section tires, 20 mm tires have less rolling resistance than 25 mm, which have less rr than 28 mm tires.

On a smooth surface this is what should be expected.

No doubt that larger tires ride softer. It seems that for today's road bikes the 23 mm size has become the most popular.

LesterOfPuppets

I like no larger than 25s on caliper brakes. 28s are the sweet spot if you got cantis or vees.
Just because 28s won't get past many caliper brakes without deflation.
That's of little consequence if you rarely remove wheels, however.

garage sale GT

I find the 23s can actually seem to be riding softer at a given rolling resistance because they are narrower and can compress easier. Of course, the fatter the tire the lower the pressure you can use but the drawback is rolling resistance.

Sluggo

Unfortunately, real roads are not not smooth steel, as the drums were in the Avocet tests. Other tests (Bicycle Quartery,Vol. 5, No. 1 (Autumn 2006)), performed on actual roads, reach somewhat different conclustions. Velochimp's summary: "The test’s findings point to a new direction for performance bicycles. For most cyclists, wide, supple tires at low pressures offer more speed, better comfort, increased versatility and improved safety than today’s narrow high-pressure tires. However, this type of wide, fast tire currently is not available. Hopefully, these test results will help persuade manufacturers to produce them."

noglider 

Interesting article! But, like many studies, while it brings many new facts, it creates new questions. What does he mean by "wide"? Does it mean relative to anything narrow, or does it mean up to a certain width? If he means 28mm, that's narrow to some people's thinking. I'd like to know the widest tire he tried.

garage sale GT

I wouldn't say that goes contrary to Avocet's conclusions simply because they didn't comment on hypothetical 28mm tires with super supple sidewalls which don't exist.

noglider 

What does supple mean? I have 28mm tires called Panaracer Pasela, and it's made of nylon, of course, and the sidewalls are very supple. And yes, they do feel very fast and comfy. They're also surprisingly round, so they may be close to the ideal design you're speaking of.

Sluggo

The original BQ test is not available on line, and do not have a copy, so I don't know how wide they went on the original test; I assume it was at least 28 mm. I need to buy the back issue, I guess. Here is a more recent article, but it does not include the roll-down testing of the original article.

There are more wide, supple tires available now that there were in 2006, many of them imported by BQ. The Pasela has been there all along, and has the same cords, but more rubber, than the tires BQ sells. My experience is that the BQ tires do indeed roll better than the Pasela or the nearly identical Rivendell tires, but the BQ tires are significantly more fragile.

BQ also did a test in the most recent issue that involved a power tap to measure the amount of rider power necessary to maintain a given speed over rumble strips. The conclusion of that experiment was that tire casing made little difference with this lower-frquency higher-amplitude vibration, but lower pressure (up to a point) generated lower rolling resistance. Of course, if you want to prevent bottoming-out, that means wider tires.

noglider 

Interesting stuff which debunks our intuitions and folklore. I'm in the computer biz, and as you know, computer and electronics technologies move very fast. By contrast, bike technology moves very slowly. But one thing that is exciting is that tires are constantly improving.

I don't doubt that there are better tires than the Pasela, but I often sing its praises because of its value. I have them on my old Raleigh Super Course, which is set up as a commuter bike. They make the bike feel much lighter than it really is.

I have some Schwalbe Stelvio tires on a road racing bike, and they feel very supple. I tested them at 130 psi, and while I may have sacrificed rolling resistance with that pressure, it didn't seem to make the ride rougher.

So this thread has evolved and is no longer about simple stuff!

Al1943

No argument there. My issue is that there was a comment, above, that Jobst Brandt said that narrower tires have more rolling resistance. And then in another post the test data offered as evidence shows just the opposite. Misinformation.