New Disc brakes - what to do the numbers mean?

BarryFishFinger

Hi all.

Need some help understanding what new brakes I need to buy.

I managed to bugger up my rear brake the other week at BPW (*see below if interested!) - bike shop sorted it all out along with a long overdue service, but one of the advisories is that the seals in the rear brake lever of my SRAM DB5 brakes are on their way out and so stopping power on the rear is a bit reduced. I've bed the new pads in and whilst the rear brake works its definitely not what it used to be in terms of pure stopping power.

So figured I might get some new brakes. Equivalent spec to the (I believe) discontinued DB5s is as far as I can ascertain something like the SRAM Guide R. Chain Reaction cycles have some here on clearance:

http://www.chainreactioncycles.com/sram ... prod174534

I could nab a couple for £110 ish, which given how much I know now brakes cost, doesn't seem too bad.

But I don't understand what all the numbers mean:
- Left hand front, right hand rear? is this because Europe does their brakes the other way around?
- Size 750mm 20PM, 750mm 40PM? Is this mount sizes? Whats the PM value?
- Size 800mm 20mm, 850mm 40mm? What is this referring to?
- 1300mm up to 1700mm? What does this denote?

I think I have 200mm rotors front and back, whatever was standard spec on a YT Capra AL in 2016. I should have saved it for future reference but forgot.

Any help appreciated.

Thanks

*abysmal weather, biblical levels of rain and mud - a couple of hours of fun then an awful squealing noise at speed, followed by total lock up of the rear wheel 100 yds later; I hopped off, forced the pistons back so the wheel could rotate enough to get me down the rest of the run; 50 yds later even worse noises on a gentle exploratory brake and then a grinding crunch as the pads and metal Y mounts (whatever they're called) ingested themselves and locked everything up solid

JBA

I believe SRAM Guide brake levers are ambidextrous so can be mounted on either side. i.e. there is no right way up.

The first 4 lengths (750 - 850mm) are the length of the front brake hose, but I have no idea what 20PM, 40PM, etc means. PM is possibly 'Post Mount'.
The last 5 measurements (1300mm - 1700mm) are the lengths of the rear brake hose.

cooldad

I think, but no refunds if I'm wrong, they come with adaptors, so 20 mm would be for 180mm rotors and 40mm for 200mm. Direct fit for 160mm.

But from CRC's info, who knows? I'd call and check.

Or buy Shimano.....

steve_sordy

The Sram Guide brakes are ambidextrous. The Capra I bought came set up for the Continent, ie front brake on the left. It was easy to just swap them over. The discs are 200 mm.

CitizenLee

cooldad wrote:

Or buy Shimano.....

+1

SLX or XT.

BarryFishFinger

Thanks for the responses everyone, very helpful. The DB5s were ambidextrous so presumably the Guides are too. I could probably just switch over the existing levers now and put more power on the rear as a temporary measure. I've also been bedding the new pads in for a couple of hours and they're a lot better than they were. Not as good as they should be, but better.