So, I put some Cascadia fenders on my Amazon wish list for the holidays, and I think someone may have bit... ;-)

Unfortunately, I think I indicated the wrong size - 45mm hybrid/touring which are supposed to fit up to 700x35s. I have a 700x40mm tire on the rear, and one Amazon review said a 38mm tire just barely fit the 45mm Cascadias. So, two questions...

1. To those of you who have the 45 mm hybrid/touring Cascadias, what's the fattest tire you've used and had sufficient clearance and/or coverage with? Or more generally re: all fenders, is there a general rule of thumb about how much wider the fenders should be than the tire for fit and/or full coverage?

2. I think I may have already answered this question doing some research, but if I were to return the 45mm fenders and get a larger size, my two options would be a set of 60mm ATB Cascadias (for 26" wheels up to 2.25") or a 65mm set for 29er tires up to 2.3" in diameter. 29ers have the same bead diameter as 700c wheels, right? So I'd be better off with those than the 26" ATB fenders, right? I'm assuming that the difference in curcumference is too much to make a 26" fender work on a 700c wheel, no?

I wouldn't use 26" fenders on a 700c wheel.

BTW, I've got 35 mm Cascadias on my commuter/touring bike, and I've used 28 mm tires with no problems at all. However, I probably would get 45 mm fenders if I had it to do over again. The perfect size for me would be 40 mm, but few fenders come in that size.

The rule of thumb I've heard is that you need 10mm of clearance between your tire and the fender, but I believe that's intended to prevent sticks jamming the wheel. This will depend somewhat on your frame, I think.

Width is really about how wide the fender needs to be to block spray from the tire. I would guess that as long as the fender is wider than the tire it will help, but if it's not a lot wider it won't catch everything.

I've got all three sizes of Cascadias, though I haven't actually used the 45mm set yet. I have laid it on a set of 700x40 Conti TownRides to eye it up, and I think I'd be willing to try that. The 29ers are really wide, and they barely fit between the seat stays on my Marin Muirwoods 29er. If your bike isn't a 29er, I wouldn't expect them to fit without modification. I also have a set of SKS P50's that were supposed to work with either 700c or 26" wheels, but they didn't come down far enough in the rear (with the aforementioned Contis) to keep my back clean.

It's probably worth noting that the 29er Cascadias have longer V-stays than the hybrid/touring version. If you find that this is a problem, you can order the longer stays directly from Planet Bike for a very reasonable cost.

If I were in your position, I'd try the 45mm Cascadias and maybe consider a slightly narrower tire sometime down the road.

Big-time thanks for the feedback on the 29er fenders. I'll steer clear of those. Sounds like they'd definitely be too big, if not at least kinda funny looking, on my hybrid, and while I'm not necessarily averse to trying to modify things a little, things that work w/o mods are always easier. Seems like there should be a 50mm fender, but as tarwheel said, they don't always make the perfect size.

So... based on what I've heard so far I think I'll stick with the 45mm fenders. My 40mm rear tire is actually looking a little tired and old (a few threads visible on one of the sidewalls) at last tube change. If I keep the 45mm fenders and they don't work with the 40mm tire, I guess I'll just go ahead and get a 35 mm tire for the rear, and I've already got a 35mm tire in front, so front shouldn't be a problem. A basic 700x35mm city-type tire (which I probably need soon anyway) is all I'd need in that scenario.

Thanks guys!

I have some SKS P35 fenders with 28mm tires, and SKS P45 with the same tires.

While you can fit a 28 under a 35mm fender (3.5mm clearance), the issue I've encountered is side-spray. There's not enough overlap to really keep all the spray from getting back to you, even if you put on a mudflap.
I've noticed similar issues with my 35mm studs under the 45mm fenders. Sure, they fit with lots of clearance, but the tires sling a lot of grit and the fenders don't contain it all.

A 5mm clearance on a plastic fender could cause some issues at the metal brackets where the struts attach. The plastic fender is 45mm wide for clearance, but that bracket is riveted inside the fender and sucks up 1 - 1.5mm of total clearance. The 2.5mm clearance you'd hope for with a 5mm difference between fender and tire size is reduced to 0.5 to 1.0mm at the bracket, meaning you have to set the fender farther away from the tire, which significantly reduces the ability to effectively block side-spray.

Since you asked about a 26" fender; it probably won't fit over a 700c/29er wheel. The curve will just be wrong, like trying to put on a size Small helmet if you wear an Extra Large.
With the larger fenders, what you need to measure is the width clearance at your fork and your brake bridge. A fender like the 65mm 29er model might be too wide to clear your frame without modification. I had to modify a pair of SKS P65 fenders to clear the fork crown on my utility cruiser.

I've run 38's under PB Hybrid(45mm) fenders with no probs. 40's would be close. My Big Buzz has 32's under 35mm Hardcores,and they're real close to the edges and I've noticed a fair bit of spray getting around them(I'm going to swap them for some wider ones when I get the chance).

Just remembered. SKS makes alot of different sizes,if you're not set on PB. I've got a set of like 50mm SKS's I was going to use on a bike that was running 42mm tires.

Thx, Clifton and dynarider. I was originally looking at SKS Commuters, but was convinced by other BFers with experience with each to shoot for the moon w/ the Cascadias and ask for the Cascadias... I think I'd probably rather change rear tire size to 35s to make Cascadia 45s work. Like I said, I need a new rear tire soon anyway... And sticking with the Cascadias, the next size up for a 700c wheel would be the 65s and those, based on a rough measurement, would not work on my bike w/o mods.

I've even been thinking about going as narrow as 32s once I've lost some more weight, and for 32mm tires it sounds like the 45mm fenders would be just about the perfect width for complete coverage.

BTW, do studded tires have a different/wider/narrower even(?) spray pattern than standard city tires w/ siping of the same width? It seems like they might, b/c of the studs, but I could be completely wrong. Just curious...

I run the PB Cascadias for Hybrids on my bike. I replaced the factory 38mm Kenda tires with 35mm Schwalbe Marathon Winters for the upcoming snow and ice. It was raining cats & dogs during my commute this past Wednesday and I found the tires caused no more spray around the fenders than did the Kendas. In all fairness both tires have a "chevron" tread pattern which I understand to be engineered to "grab" the water and throw it to the sides. Both tires do that so well that if I traverse deep (over 1") water my feet get soaked. I would use wider fenders if they would fit but they don't so I wear waterproof footwear on wet days.

The biggest problem will be getting the needed clearance between the inside of the fender and the top of the tire, in other words, getting it far enough away from the tire. If you can't get quite enough clearance when pushing the official sizing limits of the Cascadia Hybrid, you may wish to order the Cascadia 29er V-Stay ($3 each on the PB site, you'll need two of them) which is 35mm longer to clear the taller tires.

For what it's worth I have Cascadia Road fenders and they just clear some 30mm CX tires, when the official limit is 28.