CarloM

Hi All,

I just bought a Giant TCR Advanced SL1 which came with complete Ultegra 8050 Di2 groupset. Both the front and rear hydraulic brakes are 140mm. My 2018 Cannondale SuperSix Evo also has the Di2 groupset but the front brake is 160mm and the rear is 140mm.

Shortly before I got my TCR, I purchased some Dura-Ace RT900 rotors for the Cannondale. I'd like to move those rotors over to the TCR which is now my daily driver. The rear one shouldn't be too hard since it's 140mm to 140mm. However the front rotors are different: 160mm vs. 140mm.

Looking closely at the 2 front brakes, they seem to be identical down to the resin pads. Even the mounting brackets are the same, except for the Supersix, the "Up for 160mm" is on the outside, pointing up, and for the TCR the "Up for 140mm" is on the outside, pointing up. The opposite labeling is true for both (SuperSix has Up for 140mm pointing down on the inside, and TCR has Up for 160mm pointing down on the inside).

TCR 140mm Ultegra front hydro brake


SuperSix 160mm Ultegra front hydro brake



So my question to the BF experts is: can I convert the TCR to 160mm simply by switching the mounting bracket's orientation so that Up for 160mm is on the outside? Or is there "more than meets the eye" to this?

I do realize I'll have to re-align the brake if I can successfully change the orientation of the mounting bracket, but I have familiarity with that because I aligned the rear brake (following Parktool's video method) to address a very minor but annoying bit of rotor rub that was occurring.

It also seems I'll have to buy different spline lockring tools since the TCR (DT Swiss) lockring has external splines vs. the Cannondale (Shimano) lockring has internal splines.

Thanks in advance for any help/advice you can give!

dsaul

Just flip the adapter around so the 160 arrow is pointing up. The external lockring tool is the same as an external bottom bracket tool. The internal lockring tool is the same as a cassette lockring tool.

CarloM

Great, thank you for your help! I was hoping that it was that straightforward with regards to flipping the mount. I was worried that maybe the fork wouldn't be compatible somehow (although logically that didn't make sense to me, I thought I'd ask the knowledgeable folks here first).

I wonder why Giant made the decision to go 140/140 instead of 160/140 like a lot of other road bikes. I can't imagine it's cost because, for consumers at least, the cost of 140 and 160 rotors are the same.

Metaluna

It’s not an illogical concern at all and you’re right to be thinking about things like that rather than just plowing ahead. Many manufacturers spec a maximum rotor size for their forks, but I don’t know how common it is to max out at 140. I would hope everyone at least can accommodate 160mm, then again performance road bike manufacturers departed from sanity long ago in their quest for aero-everything, so who knows.

Anyway, most forks get narrower as they taper from the axle to the crown, whereas a rotor just goes straight up as its diameter increases. So at some point, if the rotor is large enough, its edge will intersect with the fork blade, which is not good for obvious reasons. Also, a larger rotor will exert a larger stress on the fork for a given amount of pressure on the brake lever, so it’s possible that you may exceed what the fork is designed for in a panic stop situation (if you really haul on the lever and aren’t limited by ground traction). On the other hand, in normal braking, a larger rotor actually exerts less stress on the fork for a given amount of braking force, i.e. you get the same amount of stopping power for less squeeze on the lever.

Weight, aero, and fork clearance would be the three likely culprits here.

CarloM

So now I'm a little concerned. Everything you've said makes sense, and I could easily see weight and aero being factors since Giant markets this as one of the "lightest/stiffest" frames they make.

However the comment about stressing the fork worries me. I would hope for what this bike costs that they'd include a fork that could withstand the added tolerance of a 160mm rotor, especially since many other road bikes in this class are using the 160/140 combo.

Also will it become fairly obvious if I flip the mount if clearance is an issue? (i.e. will there be rotor rub I can't resolve, or the actual brake caliper will start contacting the spokes?)

CarloM

Quick update, my normal Giant LBS is closed today, but I called another nearby Giant reseller and asked the tech, and he did not think (nor had he heard from Giant) that flipping the mount up and putting 160mm would put undue stress on the fork. So when my bracket and lockring tools get here tomorrow night, I'm going to give it a shot!

redlude97

make sure the rotor clears the fork too, probably not an issue on modern disc forks but for awhile road forks only cleared 140mm rotors

CarloM

Great advice thank you! A fellow BF member who is SoCal as well (and has owned lots of Giants) just texted me and his trusted mechanic who has worked on Giant bikes extensively said it should be fine to flip the mount. Fingers crossed! Between the mechanic at a Giant LBS and this forum member’s mechanic (who does great work), my fears are assuaged.

Atlas Shrugged

The stress on the fork will be essentially be the same with equivalent stopping forces. The amount of effort at the lever may be higher for the smaller rotor however at the fork the amount of energy resisted is the same.

Another reason for the smaller rotor may be, given the amount of stopping power with hydraulic disc brakes a smaller rotor will require higher lever forces thus preventing over actuating should the rider not be experienced with modern disc brakes.

CarloM

Quick update, converted the front to 160 last night, had to re-align the brake, and everything seemed to go well. Took it out on a 5 mile ride with some hard stops and everything seems to work great. Post-ride checkup on the brake/rotor didn't reveal anything sketchy.

The only thing I probably should have done, but didn't want to because of the hassle, is shorten the brake line by 10mm (which I assume is what I moved it up to accommodate the 20cm larger rotor). Instead, since the line is clipped to 2 spots on my fork, I just pushed the line up which created a bit more play above the last tie, to where it goes into the bar tape.