I have been commuting for about three years. I gone through several rims by wearing the rim down from braking. I decided to go with disc brakes in front since I use the front brake the most and I don't have a disc frame anyway. I can buy a fork for my Surly 1x1 made by Surly or a similar fork that is disc only made by Dimension. The Dimension for is a little cheaper. I've also decided on Avid bb-7 brakes due to simplicity and quality.

Here are the questions:

What size rotor should I go with? I think I'll need more that the standard 160mm since the bike is heavily loaded sometimes. Will 185mm be enough and will 203mm be better or overkill?

The Dimension fork is disc only. The Surly fork is disc or canti mount with removable bosses. The Surly fork is slightly more expensive. The Dimension fork will have a nice clean appearance with no canti mounts. Any thoughts on the two forks, quality or performance wise?

Am I overlooking anything on this front disc brake conversion project?
The best prices I've found for the brakes is $54 for the 203 rotor and $64 for the 185mm rotor.
$65 for the Surly fork and $52 for the Dimension fork.

If I understand things, if I wanted to go to a different size rotor, all I would have to do is buy the adapter and rotor. Those two items would make the change over, correct?

Thanks a lot y'all.

Don't forget the cost of a new disk hub to handle the rotor.

I did fail to mention that I already have obtained a used disk specific wheel set.

AFAIK, the caliper mounting position deterimes the rotor size--closer to the hub for 160, further away for larger. Unless your fork offers a choice of caliper mounting positions, I think you're stuck with whatever size fits.

You'll love the BB7s, BTW. I got mine for exactly the same reason---rotors are cheaper than wheels.

The Avid BB7 can be ordered with 160, 185 or 203mm rotors - the correct adaptor will ship with the caliper, so there's no need to worry about the mounts on the fork. You are correct about just having to buy the rotor and adaptor to make the switch to a different size.

OIC. Thanks for the correction!

Can anyone recommend a rotor size? I can get the 203mm for the least money, but I don't want overkill or something I'll regret...

I'm perfectly happy with the 160mm Avid Roundagons that came stock on my bike. We haven't had a lot of wet since I bought it, but it is true that there's no difference in braking with the discs, excepting, of course, tire traction on the road, which ultimately is the limiting factor in stopping power. Although I am much less prone to locking-up the wheels with the discs. The feel and modulation are that much better.

Two weeks ago I took the bike on a century that included lots of climbing, and thus, lots of long, screaming descents. Even a five-mile descent which peaked at 46.8 MPH was completely undramatic as regards the brakes.

BTW, this is with a 23 pound road bike and 170 pound rider and a typical unsupported century ride's worth of water, snacks and gear.

As for the rotor prices you quote, there's really no need to drop trou and reach for your ankles when buying rotors. I use BikeStop in Colorado for many of my component purchases. They have Avid Roundagon rotors for $22, $25 and $29 in 160mm, 185mm and 203mm sizes respectively.

They have other brands ranging from $15 for a 160mm Tekro, to $68 for a Hope, two-piece floating rotor. Not sure why two-pieces are needed or why one needs to float. Or if a $68 rotor stops better than a $15 one. But I went to discs because rotors wear longer and are cheaper to replace than rims. I see no point in buying rotors that cost more than rims, (albeit even these high-priced ones are still less than wheelsets.)

Linky: https://stores.ebikestop.com/Store/Ca...=2&catid=13826

I've got a 203mm front on my commuter and have had no real problems. The disadvantages are really only theoretical : It would weigh slightly more. Also a larger rotor may be slightly more inclined to warp, mainly in that any small warpage, or mounting misalignment, is magnified by the larger diameter of the rotor.

Well, I decided to go with a 185mm rotor and the Surly fork. Changing rotor size would not be that much of an expense if I can't live with the 185mm.

The wheel set I bought used has a 24 hole UST rim. It's an MTB specific wheel, so I'm hoping that will make up for the very low spoke count. I also like the UST rim for it's ease at running a standard tire with sealant since I've had very good luck with my home made sealant in Serfas Drifter tires. I just changed to Specialized Nimbus EX tires, so that good luck with sealant may not last.

BB7's rock. Anything over 160 is overkill on a street bike unless you're downhill racing on Pike's Peak. My entire fleet is 160 and I live in a hilly area and have never needed anything stronger. Your tires will make a bigger difference than the rotor size. Wider,smoother tires will have a larger contact patch and will allow harder braking.

I would've gone with a Kona Project 2 fork. Can be had disc only and lighter than the Surly.

Are you saying you're running hook rim tires on tubeless rims?

Floating rotors really aren't necessary on a street bike. Downhill racing maybe,or on a tandem. Floating rotors are used extensively on racing cars and motorcycles. The rotor is attached to the wheel by a piece called the carrier. The carrier bolts to the hub and the rotor attaches to the carrier with special mounts that allow it to move slightly. This movement allows the rotor to line up perfectly with the pads for maximum contact area. Mandatory for a 300lbs motorcycle tearing around a track at 180mph,bling on a 30lbs bicycle doing 20 around town.

The $68 rotor is probably made out of better material and will last longer and warp less than the $15 one.

1+.

Sorry, i have to go against the consensus and say Mech Avids are sooooo 90's. feel, reliability, weight, can't compare to hydro. Yes I've had em both.

I suggest picking up a Hayes HFX-9 Carbon front set, a standard 160mm rotor, and use metallic pads. Strong, cheap, dead reliable. I've used may discs on my commute and this is my preferred setup. Going bigger increases the chance of whacking it on a curb, rack, or something.

my 2cents

Cheers

Well now y'all chime in with disc rotor size suggestions. Oh well, I'll try the 185s and if they are too much, I'll spring for the 160 mm rotor and adapter.

I'll agree with acroy on the hydro vs. mech thing. The feel is more solid with hydraulic discs than with mechanicals. That said, for commuting purposes I would be happy with either, so long as I didn't have to back to rim brakes...

Trouble with hydros is levers--no STI, Ergos or Double-taps for hydros. If you prefer integrated levers on drop bars, there's only one choice: BB7

Yes, they work fine.

Hey JoebikerLA, how's tubeless commuting working for you??

I've been running tubless Marathons since May, about 2000 miles, no flats no issues. Awesome. I think it's the best kept commuting secret out there.

Shimano has a cable-actuated caliper for road levers: https://www.bikemannetwork.com/biking/p/BR8554

I also once saw a kludge where the owner used STI levers to pull cables to operate MTB brake levers mounted on the bar top. Pretty clever.

Magura made drop levers for their hydro rim brakes. I wonder if those levers would work with disc calipers?

I've been having great luck with them. The only time I have trouble is if I take the tire off to try another. I have to use the ghetto tubeless method and it requires a new tube each time I remove the tire. I had one really big puncture running the Serfas drifter tire on the rear. I looked down at the chain stays for some reason and saw the bright green color of my sealant on them, tire sealed up fine though and I made it home. Several other times I would see some green dots on the tread of my tire and that would be it. No leak, no flat. I do wish a true UST tubeless 26" road tire was made. I have a UST disc wheel set that I bought used and it would be easier to seat the bead if the tire was UST.

I just recently installed some Specialized Nimbus EX tires that came with the wheel set. They are 1.5" instead of the 2.0" of the Drifters. I had a little trouble getting the beads to seat, but finally did. The nice thing about using sealant in the tire is that after maybe a month, the bead will stick the the rim and you can deflate and add sealant through the valve stem without worry about seating the bead again.

I'll keep using tubeless mainly because all of the punctures I've had have sealed up and I've made it home or to work. That's the main thing for me. I can do the work on it from the comfort of home instead of on the road in the dark or bad neighborhood or pouring rain.

Glad to hear it. I have yet to have a failure. every few weeks i inspect the tires and pull nasty junk out. a bit of sealant bubbles out and that's it. my only issue is that my tires seem a bit small or my rims a bit big. Weird. Makes getting the tires seated true on the rim very hard. Strange problem.

Do you carry tire plugs for larger punctures, i.e. a big nail or screw or something?

sorry to threadjack

I've been riding on 160mm rotors for a few winter seasons now. They stop me (200lbs), and my loaded commuting rig on steep hills around Seattle.

I recently blew out a rear hub, and relaced my wheel using a Deore LX hub (19.99 on nashbar). I also upgraded the rear brake caliper from Shimano Deore to an Avid BB-5 (shimano was busted and avid was in stock on sale at LBS). I can't begin to explain how much more stopping power the Avid BB-5 has over the deore. I'm sure a BB-7 can only be better.

160mm disc is PLENTY for commuting. Unless you have bald tires or poorly adjusted brakes, you will be able to lock up your wheels anytime you want.

I was not aware of that since it seems not to be a current part. Searches at https://bike.shimano.com/ came up empty for that part number, and a generic search for "disc brakes" came up only with hubs, hydros and levers.

Call me old-fashioned, but I think the words "kludge" and "brakes" don't belong in the same sentence, let alone together on my bars.

It's not just plain brake levers I was referring to, it's integrated shifter/brake levers (brifters if you will) I was talking about. Not available anywhere for hydros.

Yup, you're right - sorry, I missed the brifter requirement. I can only imagine hydraulic brifters [drool...]