elcyc

As noted in my Miyata 512 thread, a little snag I ran into while experimenting with various 700c tires, has led me to some confusion about tire TALLNESS.
The stock 512 comes with 700c x 25c clincher tires .
I have no issues with that second metric (width, 25c) and Miyata's frame and stock brake calipers can accommodate wider 700c fine. But actual tallness of tires causes issues, when fully inflated. TALL tires can rub the brake calipers.
But I have not see this dimension formally reported or discussed. Correct me if I'm wrong, of course.

Iride01 

As tires grow in width they grow in height. Roughly.

So if you have brand xyz on your bike and measure the clearance to the tread at the possible places on the bike it might rub., Then get brand xyz in a larger width you can expect it to be about that many mm taller. But if instead you get brand abc and it has a much more aggressive tread pattern, then you should be aware that since we are only talking relative measurements, then the actual increase in tread thickness is something that wasn't accounted for in the estimate calculation.

This only is for bike tires. Won't work on your car tires as other things about their design control that. But bike tires are essentially a long balloon that have the ends fastened together.

bboy314

Since bike tires are approximately round in cross section, width and height (tallness) are essentially the same thing. So a road bike’s frame and brake calipers will be the physical limit of how wide/tall a tire it will fit.

njkayaker

The "tallness" is going to be roughly the the same as the width.

The actual number depends on the rim size. A wider rim will make the tire shorter and a narrower rim is going to make the tire taller.

Apparently, the rim width affects tire width but not the height.

If it rubs against anything (that can't be moved/removed), the tire is too big.

Old road bikes weren't (generally) constructed to accommodate wider tires.

elcyc

Your reply is confusing.
My Fuji Absolute 2.0 (2010) model has rims just as narrow as the 1989 Miyata 51. But it (and the frame) can allow for a good variety of tire widths and tallnesses. Yes, the Fuji is a communing disc-braker, while the Miyata is a competition/sports rim-braker. They both have 58cm frames.
I assume, then, that on the issue of tallness, it is ultimately down to eyeballing, experience with bikes, etc. And there is no formal metric.

ThermionicScott 

As mentioned, bicycle tire casings take on a circular cross-section when inflated. What else would they do?

From this circle, tread adds to the height. Tires with a thick tread will have a slightly egg-shaped cross-section. Because so many factors are outside the control of the bike manufacturer, it's on the end user to select tires that fit.

elcyc

Car tire nomenclature has one useful "metric" that bike tires could also use: "LOW PROFILE" .

RH Clark

A wider rim may cause a tire to be slightly less tall than a narrower rim but as far as I know it's mostly a try and see if it fits proposition. You can usually gauge how much bigger of a tire will work by checking mm clearance with an Allen wrench around the possible contact points when you have narrower tire mounted.

bboy314

Sounds like your Fuji has room for wider tires, whereas the Miyata does not, which is normal for a bike of its kind. The rim affects how tall the tire sits but the actual important metric is how much room the frame has.

Iride01 

Bike tires don't have the structure to contain the profile. If they did, they'd be heavy and very unforgiving of every bump on the road. That'd defeat the reason you are probably wanting wider tires.

The best you can do for keeping a low profile is to not get tires with heavy tread patterns. Which IMO, tread isn't needed for a bike tire if you are on pavement.

njkayaker

The tire doesn't fit with the brakes on the Miyata. Thus, the tire doesn't really fit on the bike.

(I'm not sure if you can change the brakes on that bike to ones that have more clearance.)

Actual tire widths can also be (a bit) different than the listed width.

The relevant measurement on the rim is where the tire bead hooks. The inner width, I guess.

Bigger tires fit on the Fuji is because it has disc brakes.

It sounds like you are trying to fit a tire that is bigger than 25 mm.

If you are having an issue with a particular tire, I'm not sure why you wouldn't say what the tire (and the width) is.

Car tires are not bicycle tires. You need the profile with car tires so you can match it to the rim diameter or what the speedometer is calibrated to.

Car rims are also standard widths. The height of the tire is always the same.

No bicycle tire manufacturer is going to indicate height because it depends on the rim width the manufacturer has no control over.

You are stuck working with this limitation.

13ollocks

the problem with that is that low-profile car tires are augmented by active suspension. For most road bikes, that ~1” of air between the tread and the rim is your only suspension element. You need that height to avoid destroying your rim and/or rattling your teeth out of your head

NumbersGuy

Low Profile is not a metric but a descriptive term that is not specific or applied consistently.

The aspect ratio is the actual metric. It's the second value and indicates tire height as a percentage of the first value, the section width (which is not the width of the tread, but the width between the widest edges of the sidewall of an inflated tire without a load after it has been mounted on a proper wheel assembly). So car tires are a little confusing with a millimeter section width, a percentage and a rim diameter in inches. A number of different aspect ratios can be considered "low profile". It's not as if there are two versions of car tires, a regular profile and a low profile version.

For example 245/45R17 tires are 245mm across the widest part of the sidewalls and have a height of 110mm (45% of 245mm) and fit on a 17" diameter wheel. These were traditionally considered "low profile" tires, and some still do, but others might say only a maximum of 245/40R17 or 245/35R17 are low profile by current standard. There are also 30 and 25, or even 20 aspect ratio tires now, so "low profile" can mean many different things, and the same aspect ratio results in different sidewall heights for different width tires.

As others have stated, bicycle tires are not constructed in the same way and the measurements will vary much more depending on the width of the rim they are mounted on.

13ollocks

Not being a nit-picker - just want to ensure that the info in your otherwise informative post isn't confusing

urbanknight

It sounds like the brakes on the Miyata has a tighter tolerance than the Fuji. As for the rims, are you measuring the INSIDE of the rim with a caliper?

Bike tires couldn't use that because they have a pretty much round cross section.

slow rollin

There is no numerical reference for bike tires "height" or "tallness" At best you get the approximate width in inches or mm's and that is on a standard rim at a standard pressure. On a miyata 512 I would guess the rims might be a little narrower then average for modern tires, so you may find tires inflate to a smaller size. For reference this happens frequently with my older continental tires at 10psi below max tire pressure(I do weigh that much).
Honestly, my best recommendation is to err on the safe side, or buy tires on sale that are specced close to the maximum size that you can fit.
Oh, and run an exterior mudgaurd/fender, not one that sits inside the brake mount/chainstay. That would give more room.

Don't forget that if you have rear screw adjusters you can remove the springs and flip them around for more travel rearwards for larger tires.
Next time you are looking for a bike that can take larger tires, get a mtb, or vintage touring bike(these are coveted). Otherwise go for 70's era road bikes since they generally have more clearance.

terrymorse 

Rim width has minimal effect on tire height. It has a substantial effect on tire width.

njkayaker

Yeah, it looks like that’s the case.

https://velo.outsideonline.com/road/...-vs-rim-width/

It seems the OP is trying to use a larger tire (which doesn’t clear the brake caliper).

squirtdad

Bike tires are not precise, as noted above, internal rim width can make a difference in actual measurement

tallness is not a term used, height is, but is is not provided as a separate measure...i.e 28mm wide 25 mm high. tires are listed by width only

as general statement height will be close to width..

Bike frame clearance for tire varies wildly based on purpose of frame and trends at time the frames was mad

In 1989 the trend was to narrow tires. I had an 89 Miyata 1400 which came with 20mm tires. I was able to fit 28mm Conti 5000 on that bike, but on mavic open pro rims.

the 512 came with 25mm, I would think there is a good change to get to 28mm, but nothing more that

70sSanO

You can check out Bicycle Rolling Resistance...
https://www.bicyclerollingresistance.com/

They use their own measurements (17.8mm rim and 100psi) for width and height.

Over the past decade some tire mfg's have changed their dimensions to reflect wider rims. As rims have become wider, tires grew in width so a 25mm tire might measure 26+mm on a wider rim.

For example GP4000 vs. GP5000. According to BRR measurements, the GP5000 is also not as tall; 24mm vs 25mm.

John

elcyc

First a correction… the tires on THIS Miyata are 700 x 23c, Michelin hi-lite supercomp. So even narrower than its spec sheet.
I did not use calipers, but simply eyeballing the rims —and dimensions look very close, The stock Fuji tires on stock Fuji rims overhang (fatness) as much as when I installed the Fuji tires on Miyata rims. It’s JUST the Miyata brake calipers that rub those tires when inflated — maybe 2mm is all I need. The Miyata frame will otherwise easily fit quite a wide variety of “fat” 700c tires.
All that said, and actually riding the 512 today, I might be okay with very good low profiles as the Michelins are not as hard as I assumed.
Something soft and quiet.

shelbyfv

Low profile what?

79pmooney

This has probably been said, but I scanned the above posts and didn't see it.

Bicycle tires tend to go to a round inside shape when inflated. But, you can add material as you want outside that round shape to make a exterior shape that is far from round. Many, perhaps most bicycle tires have thicker thread than sidewalls. Often thickest at the center of the tread. So it is easy to make a tire that will fit the stays but not a close brake caliper or bridge. Stated tire width isn't going to tell you this.

NumbersGuy

Thanks. Fixed my post.

urbanknight

I have learned time and time again that eyeballing things is far from accurate. Different shades of color, shadows, shapes, forced perspective, etc. can trick the eye.


That's not actually a small amount considering what you're asking. The typical rubber of the tread on a tire is probably about 2mm thick, so shaving the tire down would not help. Might be able to shave off 2mm from the underside of the caliper, but I would consider that a risky move. You could possibly change to a caliper with more clearance.