# Thread: 7" rotor = ? mm

1. ## 7" rotor = ? mm

203mm rotor is 8" and I'm sure 185mm = 7"?

160mm = 6"?

2. 7" = 177.8 mm. In the biking world this would be rounded up to 180mm.

3. Originally Posted by lebikerboy
7" = 177.8 mm. In the biking world this would be rounded up to 180mm.
Or 185mm.

I wish the use of 6", 7", 8" and now 9" for rotor size would just be dropped. There are too many exceptions in actual diameters. Just use the actual size, preferably in mm.

4. I have Hayes 7" rotors on my AM Santa Cruz Nomad. Love 'em!

5. Originally Posted by Mudd
I have Hayes 7" rotors on my AM Santa Cruz Nomad. Love 'em!
I bet they do not measure exactly 7". I have no clue whether they are 180mm or 185 and the Hayes web site is no help.

6. Eh, all bike stuff should be metric ...that would solve a lot of problems. Besides, we're 1/2 way there anyway (all the hex bolts are metric, forks are metric, some mfgr's are listing rear travel in metric...even tires are stamped with the metric size even if referred to by imperial).

7. Originally Posted by shiggy
Or 185mm.

I wish the use of 6", 7", 8" and now 9" for rotor size would just be dropped. There are too many exceptions in actual diameters. Just use the actual size, preferably in mm.
Don't forget there is also Hope's 183mm rotors in that range (maybe even Magura Louise FR's 190mm, since their "eight incher" was 210mm)

8. Originally Posted by crisillo
Don't forget there is also Hope's 183mm rotors in that range (maybe even Magura Louise FR's 190mm, since their "eight incher" was 210mm)
My point exactly. Using the 6, 7, 8-inch designations implies the rotors are all interchangeable when they may not be. And this is ignoring the braking track width differences (mostly a Shimano rotor issue).

9. Originally Posted by shiggy
My point exactly. Using the 6, 7, 8-inch designations implies the rotors are all interchangeable when they may not be. And this is ignoring the braking track width differences (mostly a Shimano rotor issue).
Totally agree...

besides ... metric rules!

10. Originally Posted by crisillo
Tottally agree...

besides ... metric rules!
I have lots of metric rulers! and tape measures

The crazy thing in the US is the expensive tape measure are imperial-only while the cheapest ones have the imperial scale on one edge and metric on the other.

11. Your northern cousins went metric 'cause we were told that's the way our major trading partner was going...hasn't happened yet! For a guy who went to school and learned imperial it's tough to figure out what someone is talking about when it's in metric.

Here's one for our American cousins...did you know that an imperial gallon is 160 ounces while an American gallon is 128 ounces?

12. Any body that count a \$10 dollar bill in pennies is already an expert. You mind already works in base 10 math, you just have to learn that a mm is the thickness of a dime. It make so much sense, whole numbers.....you will be assimilated, resistance is futile. The conversion is 25.4 mm/inch.

13. Actually, the US is "officially" metric...but don't expect anyone to budge a cm from their well intrenched imperial system any time in the near future.

Besides, up here in the Great White North all the stores still have \$/lb for produce and meat.

14. It can come in handy that the a2z brake adapter IS mounts are slotted, and adjustable in a 5mm range, which can help fit different brands of rotors - 180mm, 183mm 185mm, no problem.

15. Originally Posted by shiggy
Or 185mm.

I wish the use of 6", 7", 8" and now 9" for rotor size would just be dropped. There are too many exceptions in actual diameters. Just use the actual size, preferably in mm.
Yep, life would be so much easier if simplification went the way of the dodo.

Just think:

26" bars would be 660 milimeters!
27" bars = 685 milimeters
better hope manufacturers step up and don't short us that extra handlebar room!
My 5.75" travel frame would be 146 mil
Its' 6" travel fork would be 152.4 milimeters
My 2.1" XC tires would be 53.3 mil - depending on whether you're measuring outer knob or casing - in which case it could be 60 milimeters. Maybe we should average it and say 56.6 mil? Or should I go with 60 mil?

On second thought, I probably shouldn't shorten it to "mil" - that's so imprecise. Milimeters. Say it "MILLL I METERRRR". Enunciation is next to Godliness - which is almost as highly regarded as propeler headed bicycle fanaticism.

My 3" travel fork would be 76.2 milimeters - except that I think it's actually 80 milimeters, even though Manitou called it 3". Now which is it, Manitou???

We need a new industry standard, diplomatic peace movement, ala the now mostly defunct ISIS movement.

My "big bike" has 203.2 mil in the front and back - if we're to believe the manufacturers, that is. Those dunderheads refuse to step up and call it anything other than 8". And, the rear travel is adjustable to 152.4 or 177.8 mil - caveat that with the above - it's listed as 6", 7" and 8" - now if only we had the next ISIS industry standard...

... Someone, quick call Foes, they're going to need to add a couple pages to their catalog, what with this extra precision! And while you're at it, smack Brent around until he learns the Metric System and proper diction!

As if we didn't have enough to bicker about in our procrustean, high browed manners; now we can quible over tenths of a milimeter! Yippee!.

What fun the exorcism of simplicity brings!

16. Originally Posted by imridingmybike
Yep, life would be so much easier if simplification went the way of the dodo.

Just think:

26" bars would be 660 milimeters!
27" bars = 685 milimeters
better hope manufacturers step up and don't short us that extra handlebar room!
My 5.75" travel frame would be 146 mil
Its' 6" travel fork would be 152.4 milimeters
My 2.1" XC tires would be 53.3 mil - depending on whether you're measuring outer knob or casing - in which case it could be 60 milimeters. Maybe we should average it and say 56.6 mil? Or should I go with 60 mil?

On second thought, I probably shouldn't shorten it to "mil" - that's so imprecise. Milimeters. Say it "MILLL I METERRRR". Enunciation is next to Godliness - which is almost as highly regarded as propeler headed bicycle fanaticism.

My 3" travel fork would be 76.2 milimeters - except that I think it's actually 80 milimeters, even though Manitou called it 3". Now which is it, Manitou???

We need a new industry standard, diplomatic peace movement, ala the now mostly defunct ISIS movement.

My "big bike" has 203.2 mil in the front and back - if we're to believe the manufacturers, that is. Those dunderheads refuse to step up and call it anything other than 8". And, the rear travel is adjustable to 152.4 or 177.8 mil - caveat that with the above - it's listed as 6", 7" and 8" - now if only we had the next ISIS industry standard...

... Someone, quick call Foes, they're going to need to add a couple pages to their catalog, what with this extra precision! And while you're at it, smack Brent around until he learns the Metric System and proper diction!

As if we didn't have enough to bicker about in our procrustean, high browed manners; now we can quible over tenths of a milimeter! Yippee!.

What fun the exorcism of simplicity brings!
...right...

17. Imperial is my mother tongue but we switched in grade 4. Most of Canada is kinda bilingual when it comes to Imperial vs Metric. Temperature is always Metric nobody understands the Farenheight scale anymore. It's painfully sensible, water boils at 100 and freezes at zero. The rural areas were laid out in mile squares so acres stuck. Everything large is weighed in Tonnes but small stuff is often pounds. The road signs are all in Kilometers but everyone thinks miles. A sheet of plywood is 4x8'. Gas and fluids are sold in Litres.

18. Yup, the joys of living next to one of the "big"countries which is stuck in imperial....it spills over the border whether we want it or not.

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