I have 140mm disc brakes up front. How big can I go with an adapter?

[Gasenginesarecool]

Ok I bought this great little motorized bicycle (used) and I've been going through it tweaking things and doing some well-needed maintenance. The brakes are so weak. So underpowered! There is no rear brake caliper at all just the front, and the front is a really wimpy 140mm disc. I want to use a post mount adapter to go from 140mm to at least 160mm, if not 180mm. Is it possible to go all the way from 140mm to 180mm with an adapter? Looks like all the adapters I see let you go from 160mm to 180mm. What if I used two adapters stacked on top of one another?

 

[GreasyChris]

I went from a 160 to a 203 rotor with an adapter. I also needed to shim the bracket and caliper with a couple m5 washers to fit properly.

 

[Tyler6357]

You should be able to use the adapter to at least get up to 160. I'm using 160 and wanted to go up to 203 but couldn't find the right adapter.

 

[Tyler6357]

I went from a 160 to a 203 rotor with an adapter. I also needed to shim the bracket and caliper with a couple m5 washers to fit properly.

Got a picture of that?

 

[GreasyChris]

Yup once I get home from work I'll post a pic

 

[Tyler6357]

Yup once I get home from work I'll post a pic

Thank you! What adapter did you use?

 

[GreasyChris]

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[GreasyChris]

You want the front IS 203 adapter

 

[Tyler6357]

Hmmmm, unfortunately I have a different type of disc brake caliper mount. It screws directly into the fork, similar to this pic.

 

[Gasenginesarecool]

Hmmmm, unfortunately I have a different type of disc brake caliper mount. It screws directly into the fork, similar to this pic.
View attachment 91118

I have this type of mount too. I'm pretty sure it's called "post mount". I want to take my stock 140mm and get an adapter to get to least 180mm if not 203mm.