Help me get my head around disc brake mounts

Hi all,

I’ve got some Spyre post mount brakes that I want to mount to my Surly disc trucker. It’s the earlier version with IS mounts so I therefore understand I need post mount to IS disc adapters. I’m planning on using 160mm rotors front and rear but am struggling to get my head around what adapters I need to order.

I see a lot that are 140 and 160 mounts but not 160 both ends. Most sites that sell them don’t sell them in pairs but don’t give the option of buying a front or rear adapter. Are they both the same?

Can anyone point me in the direction of the right adapters? Thought this would be an off the peg jobby but I’m finding it more complex than that!

What should I use?

This is my first disc brake build so I’m having to do a lot of learning…

if you google the right thing (for instance : "IS to post mount 160 front") you will get the right item :)

Yes, this was my first port of call! But when I look up for example what you suggested they all seem to say 160 front or, for example. 180 rear. I haven’t come across ones that say 160 front or 160 rear. Is it that you use the same mount front and rear but it gives you 160 spacing or 180 spacing rear?

ignore me, being an idiot

That's right. The mounts used are the same, but the one on the rear needs 20mm more height.
So a 160mm rotor on the back would need the same adapter as a 180mm rotor on the front.

Same with 140mm rear / 160mm front.

This is the answer I needed!

So 160 front/180 rear adapter is needed for the front and a 140 front/160 rear is needed at the back?

So to use Hope adapters as an example I’d need an A and an F adapter?

https://20twentystore.com/products/hope-brake-mounts?srsltid=AfmBOor0I3ipI6XXtUHwgSaQKOYC6A1k7UTyo1X3WoLKp8ep8s6429X-

Yep, that's it. I'd get some cheap ones though, they don't really do much - £20 each is a rip!

you shouldn't overthink it imo, this ebay listing will switch pictures for you

sometimes you will discover that by flipping it it does the job elsewhere for the other side ( edit : as described above ), so one model will do both.

Super, yeah totally agree! Just wanted to check my thinking

Ordered these, hopefully they’ll do the trick. Silly cheap too…

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banana industries?

Yep, that’s the one

So discs were a mtb thing before they were ever a road thing and no mtb(er) I know has ever used a 140mm rear disc so how the hell did that end up being the 'standard'?