# Disc Rotor Sizing Problems



## BretonM (8 Jan 2017)

Hello all,
I would like to put some custom brake rotors on my bike. 
On the same specification it says that the bike has a 6" brake rotor front and rear. 
I have been trying to find 6" brake rotors all over the shop and nothing seems to even exist. 
Is there a conversion to a similar size in millimetres as this is what they all seem to be set out in. 
As I've stated before I am a rookie at these sorts of things, so any advice or help for future reference would be greatly appreciated. 
Thanks.


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## classic33 (8 Jan 2017)

BretonM said:


> Hello all,
> I would like to put some custom brake rotors on my bike.
> On the same specification it says that the bike has a 6" brake rotor front and rear.
> I have been trying to find 6" brake rotors all over the shop and nothing seems to even exist.
> ...


Price limit?
 Check here for prices.


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## BretonM (8 Jan 2017)

classic33 said:


> Price limit?


I would like a rotor with some blue or gold anodisation on it. 
Preferably under £40 for the pair. 
Just the rotors themselves. 
Thanks.


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## classic33 (8 Jan 2017)

There's these http://www.chainreactioncycles.com/brake-spares/disc-brake-rotors


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## BretonM (8 Jan 2017)

classic33 said:


> There's these http://www.chainreactioncycles.com/brake-spares/disc-brake-rotors


Thanks a lot ... however I'm still confused about which size to get ... as I say the spec says a 6" rotor but in reference to mm I have no idea ??


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## classic33 (8 Jan 2017)

You'd be looking at 152 - 153mm. It's actually just shy of 152.5mm is 6 inch, possibly why they've used the imperial measurement in the sizing.

If it says 6 inch rotor required, then any shop should know which size you mean. If they don't, keep your money in your pocket.


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## BretonM (8 Jan 2017)

classic33 said:


> You'd be looking at 152 - 153mm. It's actually just shy of 152.5mm is 6 inch, possibly why they've used the imperial measurement in the sizing.
> 
> If it says 6 inch rotor required, then any shop should know which size you mean. If they don't, keep your money in your pocket.


So if ordering online I should look for 152 or 153 mm Rotor ?


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## classic33 (8 Jan 2017)

BretonM said:


> So if ordering online I should look for 152 or 153 mm Rotor ?


Stick with the 6 inch when searching & ordering. 152mm & 153mm aren't there, for bicycles.


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## fossyant (8 Jan 2017)

Are you sure it's 6" imperial..... Rotors come in 140, 150, 160,etc etc. 

Measure the diameter with a ruler !


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## BretonM (8 Jan 2017)

classic33 said:


> You'd be looking at 152 - 153mm. It's actually just shy of 152.5mm is 6 inch, possibly why they've used the imperial measurement in the sizing.
> 
> If it says 6 inch rotor required, then any shop should know which size you mean. If they don't, keep your money in your pocket.


It's just that online the only sizes close enough are 140mm and 160mm.


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## BretonM (8 Jan 2017)

fossyant said:


> Are you sure it's 6" imperial..... Rotors come in 140, 150, 160,etc etc.
> 
> Measure the diameter with a ruler !


Yes I measured earlier, would 150mm fit because it's only 2mm out.


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## fossyant (8 Jan 2017)

150 is best, but can you post details of fork/ discs/callipers as most stuff is metric.

My 170/160's run a few mm in from the furthest edge, so going for the nearest would do the trick.

We are running totally blind here as we don't know the bike model or anything.


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## BretonM (8 Jan 2017)

fossyant said:


> 150 is best, but can you post details of fork/ discs/callipers as most stuff is metric.
> 
> My 170/160's run a few mm in from the furthest edge, so going for the nearest would do the trick.
> 
> We are running totally blind here as we don't know the bike model or anything.


I apologise, the bike is a Norco Ryde 2009. 
Thanks.


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## BretonM (8 Jan 2017)

fossyant said:


> 150 is best, but can you post details of fork/ discs/callipers as most stuff is metric.
> 
> My 170/160's run a few mm in from the furthest edge, so going for the nearest would do the trick.
> 
> We are running totally blind here as we don't know the bike model or anything.


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## fossyant (8 Jan 2017)

A 2009 bike will be metric, 150's then


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## fossyant (8 Jan 2017)

I bet the size is stamped on the discs. It is on the 3 we have in our house.


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## fossyant (8 Jan 2017)

PS that's a jump bike ?


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## BretonM (8 Jan 2017)

fossyant said:


> A 2009 bike will be metric, 150's then


Are 150's hard to find as I'm struggling to find any. 
Thanks.


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## BretonM (8 Jan 2017)

fossyant said:


> PS that's a jump bike ?


Yes ?


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## fossyant (8 Jan 2017)

140 / 160 is usually the smallest and fairly common. I have a 170 on my Boardman Pro at the front and that's unusual.

Go take a close look at the rotors, the size will be stamped on them.


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## fossyant (8 Jan 2017)

What bike is it. I can't see a name and make ?


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## BretonM (8 Jan 2017)

fossyant said:


> What bike is it. The pics tell me it has Rockshox forks, and SRAM rear mech, but can't see name on frame.


It is a Norco Ryde 2009, it has SRAM X-5 Gearing and Marzocchi Dirt Jumper 3 (Bomber) Fork.


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## BretonM (8 Jan 2017)

fossyant said:


> 140 / 160 is usually the smallest and fairly common. I have a 170 on my Boardman Pro at the front and that's unusual.
> 
> Go take a close look at the rotors, the size will be stamped on them.


In which case ( due to the rarity of the 150mm) should I just leave the stock rotors on ??


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## fossyant (8 Jan 2017)

Until you can find some, yes, leave it on. I'm struggling to find full specs.

Very little info on disc size on the web - I've looked.. Unless you've got the bike near, then the size is usually printed on them.

Ride it, not pimp it !


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## classic33 (8 Jan 2017)

fossyant said:


> Until you can find some, yes, leave it on. I'm struggling to find full specs.
> 
> Very little info on disc size on the web - I've looked.. Unless you've got the bike near, then the size is usually printed on them.
> 
> Ride it, not pimp it !


*Specification*
Name: Ryde (09)
Built by: Norco
Price: £799.00
Description The specifications are for the medium model of this bike.
Available Colours: Green
Available Sizes: M S
Bottom Bracket: Howitzer Spline BB
*Brakes:* Mechanical, 6" rotor
Cassette: Sram PG-830, 8 speed, 11-28T
Chain: Z-72
Cranks: Ruktion, 34T, Black Spire NSX 1 guide, black guard
Fork: Dirt Jumper 3, 100 mm of travel
Frame Material: 4130 butted chromoly, slotted dropout, integrated headset, integrated seatpost clamp
Front Hub: Alloy disc hub, blue ano
Grips/Tape: Norco custom design, blue
Handlebar: Full Bore 710 x 65 mm rise, 25.4 mm, black
Head Angle: 69.5
Headset Type: Impact 8D integrated
Pedals: Oddessey Twisted pedal black plastic
Rear Derailleur: X-5, 8 speed, medium cage
Rear Hub: 135 x 10 mm nutted, 8 spd 32h, blue ano
Rims: Alien Nation PBR 26" , 32 hole black
Saddle: Pivotal thin seat, Norco custom design cover, hollow bolt
Seat Angle: 72
Seatpost: Pivotal Tron alloy post 25.4
Shifters: X-5 trigger, 8 speed rear
Stem: Rippa, 45 mm ext. black
Weight: (kg) 15.5
Brake Levers: Tektro MT-2.1 alloy
Spoke Type: Stainless black 2.0

&
http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?year=2009&brand=Norco&model=Ryde


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## BretonM (8 Jan 2017)

fossyant said:


> Until you can find some, yes, leave it on. I'm struggling to find full specs.
> 
> Very little info on disc size on the web - I've looked.. Unless you've got the bike near, then the size is usually printed on them.
> 
> Ride it, not pimp it !


Okay, I don't usually upgrade my bikes in any way but (as I said I am a rookie) so wanted to see how difficult upgrading was. I usually ride a bike stock but thought a blue anodised rotor would set it apart from the rest. 
Thanks for the help as always @fossyant


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## Tim Hall (8 Jan 2017)

BretonM said:


> Okay, I don't usually upgrade my bikes in any way but (as I said I am a rookie) so wanted to see how difficult upgrading was. I usually ride a bike stock but thought a blue anodised rotor would set it apart from the rest.
> Thanks for the help as always @fossyant


Umm, aren't brake discs steel? And anodising a treatment normally carried out to aluminium? Or as it says here:


> *Is it Possible to Anodise Steel?*
> Anodising is an electrolytic process which coats a metal substrate with a protective oxide layer. The anodised coating on aluminium increases corrosion resistance and wear resistance, is electrically insulative, provides a good key for paint or adhesive and is often used as a decorative finish. The oxide layer that forms on iron or carbon steel is commonly known as rust, which readily flakes off and actually promotes the corrosion of the underlying material. So an anodising process for steel would not be terribly useful.



So good luck with finding an anodised brake disc (won't the colour rub off anyway?)
(waits to be proved wrong as usual)


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## classic33 (9 Jan 2017)

Tim Hall said:


> Umm, aren't brake discs steel? And anodising a treatment normally carried out to aluminium? Or as it says here:
> 
> So good luck with finding an anodised brake disc (won't the colour rub off anyway?)
> (waits to be proved wrong as usual)


Depends on the actual mount, which may be aluminiun whilst the rotor is steel.


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## BretonM (9 Jan 2017)

Tim Hall said:


> Umm, aren't brake discs steel? And anodising a treatment normally carried out to aluminium? Or as it says here:
> 
> 
> So good luck with finding an anodised brake disc (won't the colour rub off anyway?)
> (waits to be proved wrong as usual)


I hadn't though of that ... I always thought that the high quality 'coloured' brakes (such as those from Hope) were anodised.


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## MarquisMatsugae (9 Jan 2017)

Are you definitely going to settle with this bike ?
Will DJ be your thing ?


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## Jody (9 Jan 2017)

BretonM said:


> I hadn't though of that ... I always thought that the high quality 'coloured' brakes (such as those from Hope) were anodised.



They are. 






If you really want to change then you could swap the caliper mount so you can fit a 160 etc


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## BretonM (9 Jan 2017)

MarquisMatsugae said:


> Are you definitely going to settle with this bike ?
> Will DJ be your thing ?


I don't know .. we'll have to see


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## classic33 (9 Jan 2017)

Jody said:


> They are.
> 
> 
> 
> ...


Like  this one  from Chain Reaction Cycles?


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## BretonM (10 Jan 2017)

classic33 said:


> Like  this one  from Chain Reaction Cycles?


Where does that mount to.


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## Jody (10 Jan 2017)

BretonM said:


> Where does that mount to.



It mounts to your fork or frame so you can fit different size discs. You just need to know if you have post or IS mount and what size disc you want to fit.


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## Nigeyy (15 Jan 2017)

Well you live and learn....

Here I am, stuck in an imperialistic country ( that is, non-metric) yet I can't recall ever seeing discs over here in anything but mm! And the UK was supposed to be metric too . Tbh I've never heard of 150mm discs either -140, 160, 180 or 203mm seem to be the common ones. Even then, those are just guides as different designs and manufacturers can easily provide small mm differences. I've put discs on that aren't the same manufacturer as the calipers, and my rule of thumb is to use washers (not sure I'd use more than a couple of mm though) to get as close to a perfect track. I also keep an extremely close eye on the bolts so I get maximum purchase but I also am not going to crack the fork housing if they are too long.

Anyway, YMMV.


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