You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Hi Guys & Girls,
Recently picked up a Cotis Solaris Frame and Rockshox Reba RL fork. I'm looking to fit some SRAM Guide R Brakes with 200mm rotor on the front and 180mm on the back.
Front: I've done a bit of digging on the SRAM website and it looks like I'm needing a 40mm post to post mount adaptor. Which will require 39.5mm & 34mm mounting bolts.
I've found an adaptor: http://www.chainreactioncycles.com/lifeline-disc-brake-adaptor-post-to-post/rp-prod155580
But I'm struggling like hell to find any suitable bots and cup and cone washers. Any ideas?
Rear: I **THINK** I'm needing a 180mm IS to Post Adaptor. Are all IS mounts on bike frames designed around a 160mm rotor? I've found this one: http://www.chainreactioncycles.com/lifeline-disc-brake-adaptor-is-to-post/rp-prod155579 but again, no bolts included. I think the 4 bolts I need are 18mm long.
Probably a proper novice question but my head is farting. Can someone shed any light on this?
Thanks,
Marc.
I’d wager a 200mm rotor is way beyond the limit for the Reba which is an XC fork. It’s built using a lighter chassis could suffer damage due to the bigger forces of a large rotor (200mm usually being used on dh/long travel bikes).
It wouldn’t be my first choice of size, but its what I’ve acquired when buying a set of brakes. Trying to keep costs down on the build so thought i would give it a try for a while.
The Sram website says the Reba Rl is compatible with rotors up to 220mm size. https://www.sram.com/rockshox/products/reba-rl-1#sm.000pjycbz151oe95xgf1qmn2f7anh
Although apparently compatible, what would be the drawbacks of such a large rotor on a trail bike? I’ve only ever really had any experience with 160mm rotors.
It might not get hot enough to work properly but bar that no issue.
IS mounts don't really have a disc size - is callipers came in a variety of sizes for different discs from the same mounting - however all is disc mounts are the same ( but differnt front and rear)
YOu need a 200mm is to post mount adaptor mount - that one will do but you don't need long bolts - you have one set of bolts mount to frame and another caliper to mount
Which will require 39.5mm & 34mm mounting bolts.
<span style="font-size: 0.8rem;">That crc one uses standard bolts note it has 4 holes and each one takes a normal bolt - about 10 p each from a hardware shop as standard size- if you want some pm and i can post you a set for about a quid - please state length or i can just get standard - no idea would need to measure. </span>
IIRC you have to get avid things separate from avid and are pricey. £5 per set see in below.
http://www.chainreactioncycles.com/sram-bracket-mounting-bolts-stainless-steel-/rp-prod164208
I’d wager a 200mm rotor is way beyond the limit for the Reba which is an XC fork.
Rebas are sold as suitable for disks up to 200 mm. I've been running 200 mm brakes on Rebas and Revelations since they first came out. No problems.
A larger disk won't actually stress the fork any more than a smaller disk anyway. Even with a 160 mm disk, if you hit the brakes as hard as you can, you will either skid the tyre or launch yourself over the bars. Running a larger disk won't load the fork up any more, it will just mean you don't need such strong fingers to crash.
what would be the drawbacks of such a large rotor on a trail bike?
Easier to bend rotors on rocks and stuff. You have different sized rotors front and rear, so need two different spare rotors if you worry about stuff like that. Larger rotors give more power at high speed but slightly more difficult to modulate at low speed. I run 200 mm front and 160 mm back, so I don't see the drawbacks as worth worrying about.
Thanks for all the replies!
IS mounts don’t really have a disc size – is callipers came in a variety of sizes for different discs from the same mounting – however all is disc mounts are the same ( but differnt front and rear)
YOu need a 200mm is to post mount adaptor mount – that one will do but you don’t need long bolts – you have one set of bolts mount to frame and another caliper to mount
To fit the 200mm on the front it would be 200mm (+40mm) post to post wouldn't it? And then the rear would be a 180mm (+20mm) IS to post?
That crc one uses standard bolts note it has 4 holes and each one takes a normal bolt – about 10 p each from a hardware shop as standard size- if you want some pm and i can post you a set for about a quid – please state length or i can just get standard – no idea would need to measure
Thanks for the offer! I can get my hands on some shorter Stainless Hex Head bolts from work - do you know if they are M5 or M6 thread?
A larger disk won’t actually stress the fork any more than a smaller disk anyway. Even with a 160 mm disk, if you hit the brakes as hard as you can, you will either skid the tyre or launch yourself over the bars. Running a larger disk won’t load the fork up any more, it will just mean you don’t need such strong fingers to crash.
Hopefully I don't find that out the hard way!
Easier to bend rotors on rocks and stuff. You have different sized rotors front and rear, so need two different spare rotors if you worry about stuff like that. Larger rotors give more power at high speed but slightly more difficult to modulate at low speed. I run 200 mm front and 160 mm back, so I don’t see the drawbacks as worth worrying about.
I think I will just throw them on and see how I get on with them. If I don't like the 200mm at the front, I will just have to change it at a later date.
So guys, is the bottom line that the 2 links that I posted in the original post are the correct ones and that I will just need some regular (20mm ish) bolts to mount them?