Are disc brake rotors interchangeable between makes?

[Laser Man]

I'm about to receive my first disc braked bike through the post.
It will come with 160mm Shimano rotors, but in order to fit my e-bike motor wheel (Woosh kit) I will need to change the rear to 180mm (else the caliper will foul on the side of the motor).

Everywhere I've looked so far the basic Shimano 180mm rotors are out of stock (and I'm not about to pay a fortune for an ice-cool one).

So will it be OK to fit a Tektro (or other decent make) rotor - are they all about the same thickness?

Thanks
Mike

 

[iluvmybike]

Not good idea to put a 180mm on back and not the front. Also check if the mount on your frame will give you room to fit a 180mm - some don't. Makes are all interchangeable as long as diameter is same (some Hope rotors are 183mm instead of 180mm for example)

 

[smutchin]

Just make sure you get a rotor with the correct fitting - 6-bolt or Centerlock.

Otherwise should be fine to use any brand afaik.

 

[smutchin]

Not good idea to put a 180mm on back and not the front.

Why?

 

[BianchiVirgin]

Why?

You always need more braking force up front. You'll have a greater risk of locking up and skidding the rear otherwise.

 

[Laser Man]

Thanks Guys
I thought I should be OK with a different brand rotor, but it's nice to have that confirmed.

I don't want to risk going over the handlebars, so the front will stay 160mm and I'll put up with the risk of a skiddy rear.

 

[si_c]

Thanks Guys
I thought I should be OK with a different brand rotor, but it's nice to have that confirmed.

I don't want to risk going over the handlebars, so the front will stay 160mm and I'll put up with the risk of a skiddy rear.

It's unlikely you will go over the handlebars, on the road a 160mm rotor is fine, but you should be aware that about 3/4 of your braking performance comes from the front wheel. I rarely use the rear brake on it's own, it just doesn't do much compared to the front.

 

[smutchin]

You always need more braking force up front. You'll have a greater risk of locking up and skidding the rear otherwise.

Not necessarily. Depends how you use your brakes. The front brake is entirely independent of the rear and most people with two functioning hands are capable of applying different degrees of pressure to each lever.

I recently had a bike for a test ride that had a 105 calliper up front and a disc at the rear (the reasons for which are too boring to bother explaining). So the rear brake was arguably more powerful than the front, yet I didn’t lock up either at any point during my time with the bike.

 

[smutchin]

I don't want to risk going over the handlebars

The weight of the motor in the rear hub should make that a lot less likely. It’s also perhaps an argument for a larger rotor on the front too - many off-the-shelf road e-bikes come with 180mm rotors for this reason. Although I would think 160mm is plenty big enough.

Don’t worry too much about skidding. What actually happens when you use a bike with more powerful brakes is that you’ll moderate your use of the brakes accordingly.

 

[Deleted member 26715]

Don’t worry too much about skidding.

Unless of course you revert to child mode & do sliding stops

 

[si_c]

Unless of course you revert to child mode & do sliding stops

I do that now and again at traffic lights, for funzies.

 

[Yellow Saddle]

I'm about to receive my first disc braked bike through the post.
It will come with 160mm Shimano rotors, but in order to fit my e-bike motor wheel (Woosh kit) I will need to change the rear to 180mm (else the caliper will foul on the side of the motor).

Everywhere I've looked so far the basic Shimano 180mm rotors are out of stock (and I'm not about to pay a fortune for an ice-cool one).

So will it be OK to fit a Tektro (or other decent make) rotor - are they all about the same thickness?

Thanks
Mike

The thickness is all about the same, around 2mm. However, there are two basic types of materials used on bike brake discs. I'll paste this information from a book on the topic. It is quite detailed, but covers all the bases and should help with understanding the issue.

"Better discs can withstand extended use with sintered metal pads because they are made from a type of stainless steel (Martensitic stainless steel) that can be heat treated to make them harder and more durable. Heat treatment is a process of controlled heating and cooling that changes the crystalline structure of the metal and the benefit is not only a stronger end-product but also ease of manufacture. The untreated steel can first be cut, shaped and finished whilst still soft and easy to machine and then, right at the end, hardened. Heat treatment makes these discs more resistant to abrasion – exactly what’s needed for sintered metal pads. The extra manufacturing process increases the cost and hence these discs are OEM fitted to more expensive bikes and cost more in the aftermarket too. A heat-treated disc can be used with both types of pads whereas a non-treated disc can only be used with resin pads.

Heat-treated and non-treated stainless discs look the same to the untrained eye but there are usually some visual clues as to which is which. The non-treatable metal (technically called Austenitic stainless steel) is more malleable and can be stamped from sheet metal. The die leaves a telltale chamfer on the one side of the disc and a sharper edge on the other. Imagine a cookie cutter punching a shape in dough. The entry side is curved and the exit side has sharp, 90 degree edges. The harder, heat-treated stainless steel is laser or water jet cut and has a different edge finish, with both sides presenting sharp edges. Laser- or waterjet-cutting is more expensive than die-cutting.

Cheaper, untreated steel is suitable for resin pads only, heat treatable stainless can be used with resin and metal pads.

It is not only the base material that affects a disc’s performance. The size and design has an effect too. Insofar size goes, a larger disc can apply more torque than a smaller one and is thus advisable for sports such as downhill and endurance racing. Tandems also benefit from larger discs. Larger discs have some disadvantages, these being weight (marginal), fit, and feel. A larger disc is more prone to grabbing and offers less subtle modulation. Smaller discs feel smoother. Users may or may not notice or care. Some frames may not be able to accommodate larger discs.

Heat management
The size of the disc is directly related to cooling. A larger disc is easier to cool because of the large area exposed to the airflow. Heat affects brakes in various ways: resin brakes easily overheat and metal pads change their coefficient of friction when they heat up. Broadly, resin pads work better at low temperatures and metal pads better on higher temperatures. Technically the disc can be too large to become hot enough to benefit your sintered pads, but that’s on paper and for the consumer to attempt finding an optimum size disc based on those factors will be neigh impossible because of all the variables.

Discs are both heat sinks and heat radiators. The larger the surface area, the better the discs radiates heat and cools down. The heavier the disc, the more heat it can absorb before it starts to radiate heat. However, the heat sink effect is of no practical use on bicycle disc brakes since the mass of a large or small disc is small and very similar and both reach heat saturation (heats up to a point where radiation equals the heat input) after just a few seconds of application. Some aftermarket discs have large cut-outs which leave them with space than surface. In the extreme, this is counter-productive. Surface area is required for good radiation. Further, disc pads are flexible under the types of pressure the caliper is capable of and with filigree discs, hard braking creates a strong pulsation or vibration and audible buzz as the pads flex to fill the voids between the “spokes” of the disc."