Fender size for 700x30 and 650bx47

[Eric Hounshell]

Hi All,

For the winter I've got my two wheelsets set up with 700x30 slicks and 650bx47 small-knob gravely tires. I am thinking about putting fenders on, but I'm unsure what is the best size to serve double-duty.

What about these 53mm SKS Bluemels (alternative link to similar set from manufacturer webpage).

Thanks for tips!

-EH

[satanas]

FWIW & YMMV: In 2019 I used the VO Wavy 58mm fenders over 48mm measured width 650b tyres and had plenty of room, however that frame was built for discs and to clear ~57mm tyres so had ~10mm lateral clearance and somewhat more above the tyre; on the frame drawing the bottom of the seatstay bridge is 375mm from the centre of the rear dropout.

The fenders linked seem suspiciously cheap to me, and the word "Bleumels" possibly implies that they are plastic only, rather than the chromoplastic laminate used in the better SKS models; this is much less tough, and tears or cracks much more easily.

Since 47-584 and 30-622 should be within a very few mm of the same radius anything that will clear the 47s ought to be fine with the narrower tyres, if a bit less aero than ideal.  ;-)

Later,

Stephen

[Pat Smith]

I also have 650b x 58 Velo Orange wavy fenders on my BMC Road+ disc frame and it fits my 650b x 48mm tires and my 700c x 32mm tires. Looks kinda funny with the skinny rubber though :)

The whole point of the "road plus" 650b x 48mm tire is that it is supposed to be the same outer diameter as a 700c x 28mm tire, right? 

Pat in DC

[Stephen Poole]

@ Pat: How do you find the handling of the Road+ with the 700c wheels? I'm assuming it will be different, but am wondering in what way.

Thanks,

Stephen

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[Patrick B. Smith]

I really only ride on pavement as the only non pavement option here in Washington DC is the C&O Cana trail. I very much prefer the feel of the bike with the 700c x 32mm tires and wheels. I'm using factory built Velocity Alieron rims and formula hubs with straight gauge spokes and gravel king slicks on the 700c wheelset. 650b wheelset handmade by me (first ever wheel build) and Pacenti Forza rims, Shimano 105 hubs, double butt spokes with RH slick tires. I also stripped off all the racks and bags for the 700c wheels, with just a small half frame bag. 650b I was running a front rack and rando bag.

I'm very much in the market for a pure road bike. 

[Eric Hounshell]

The similarity of outer diameter between 700x30 and 650bx47 is what gives me pause in fender size. The next size down would be 45mm, which would be the appropriate size for the 700x30mm tires and likely have sufficient vertical clearance to the 650b tires, but in the horizontal I simply don't know. Any further thoughts on that? Or do you folks think that extra clearance to the 700x30mm tires wouldn't be such a big deal?

Stephen asked about the BMC Road+, but I'll chime in anyway about my Marin Nicasio (not as nice as BMC but maybe similar in some basic ways). I find it rides really nicely with the 30s: slicks on the wider side are fun, especially in winter/spring conditions b/c they have good grip on wet asphalt. With 650b it feels more playful, I'd say. Doesn't feel sluggish like 26".

-e

[Stephen Poole]

I'd say the extra width of the wider fenders might look a bit odd, but they'd still work okay. Narrower ones are also likely to work, especially if: 1) they aren't metal and thus don't have a rolled edge taking up space inside, and 2) they're far enough above the tyre that there's a bit of clearance. How much is enough is arguable, but I'd think 10-15mm ought to do it. There should be at least that with the Road+ given I've seen pics with 2.1" Thunder Burts and fenders.

As for handling, I have a bike with the same front end geometry as the Road+, so 72° HTA and 60mm offset. With 42mm tyres like Hetres and a bar bag this was okay, though a bit less stable than I'd prefer. However, with 38mm (really 36.5mm & 240g) Écureil ELs and no bar bag it felt decidely twitchy, not perhaps surprising given a smaller diameter and less gyroscopic effect. My guess is that with 700x28-32 the tyre weight will be roughly similar to the Écureils (depending on which tyre), but the radius will be larger so feel will be in-between that with the 410+g Hetres and the 240g ELs. However, I haven't tried it and am just theorizing...

Later,

Stephen

[Christian B-H]

Hey EH, 

Maybe you've already bought fenders? If not, for what it's worth, I bought those SKS Bluemels 53's to put on my 56cm Kona Rove LTD which I switch a couple times a year between 700x42 and 650x47. The front bolt that comes with the fenders isn't long enough to reach through the hole in the carbon fork meant to allow a fender, so I haven't put the front fender on yet. I have 650b on right now and it seems like while I was able to get the rear fender on without cutting the metal attachments, I definitely need to get the fit closer to the tire. I had a successful 40mile ride on dirt and paved roads with some mud, and the fender held up fine even with a little bit of shaking while hard-brake skidding and high speed descending on gravel, but nothing too bad especially considering how mechanically challenged I am. For example, I forgot to tighten the bolts that hold the metal to the plastic with a tool instead of my finger, and leaving my house lost one of them while hopping a curb, and had to turn around quickly to tighten the rest and tape one of the metal fender stays to the plastic fender. It held fine over those 40miles though. 

Despite the rear fender sustaining a muddy mixed-terrain 40miler, it'll take some more miles to get them dialed in, not to mention a trip to the hardware store to find a bolt that will fit the carbon fork, and metal cutters to get the fenders to the right fit. 

For all this effort, I have to say I wish I had gone with the Velo-Orange 650x58 metal wavy fenders that Pat in DC mentioned for not too much more money...not that I can blame SKS for the performance of the fenders that I've shoddily attached so far. And, it's worth noting that Rivendell sells SKS....https://www.rivbike.com/collections/fenders 

Perhaps this was entirely unhelpful...

Good luck with the decision (and installation), 

Christian in Boulder, CO