Can someone explain fender sizing to me?

These are listed as 700c x 45mm but they say the max tire width is 35mm

https://www.planetbike.com/store/pro...d-touring.html

I'm confused.

I have a 38mm tire and I'm trying to figure out if this would still work and the 45mm and 35mm numbers have me stumped.

If the width of the fender is 45mm on the outside, and the plastic isn't 5mm thick, how does a 45mm wide fender not hold more than a 35mm wide tire? I'm guessing the plastic is 1mm thick. Maybe 2. That would leave 41mm to 43mm of space inside it.

Is there clearance for a 38mm tire that's just less clearance than is recommended? Would a 38mm tire completely not fit at all? Would it fit but be more likely to rub the fender if it was bumped or was installed wobbly or something?

This is for a 2017 Specialized Crosstrail if anyone has any other fender recommendations. (Yes. I know the issue with the front suspension fork. I can deal with that.)

Or if anyone can say "Yes, these will work on a 38mm tire you just have to be super careful installing it", that'd be cool too.

They look sleek and not like 1980's TV antennas like most fenders. And they are cheap. So if they fit I'd be all kinds of happy with them.

(Note: I'm willing to entertain responses in the line of "Just get 35mm tires and you won't even notice a difference". I will need new tires soon anyway.)

Yes, I have 45mm PB fenders on my Crosstrail. careful installation and they are fine. Look nice too, because they aren't big and clunky looking. They might not work well in heavy mud or snow, but for everything else, they are good.

p.s. I have 35 and 40mm tires on there now, and have no problems. In fact, I think the 40s actually look better. I also have 35mm PB fenders on my Sirrus, with 28 and 30mm tires, for the same reason, they look nice. They also work fine if you are careful with your clearance during installation.

The nice thing about installing slim fenders on a bike, is that they "disappear" better. And, they still keep the water and dirt off you!

Thank you! I figured it was a "35mm is the biggest if you ride through the gates of hell, but bigger tires are fine if you ride on pavement and the occasional hardpack dirt / sand"

but doesn't tire brand & model vary the actual measured width of a tire?

The general rule is 10mm wider than the tire you want to use. That being said I have 45mm fenders and run Schwalbe Little Big Bens that measure 38mm wide. They are a tight fit, but there is no rubbing and there have not been any issues.

If I was going to go to 40mm tires I'd go to the 50mm fenders.

I even had them on a set of 45s on the Crosstrail for awhile - you just have to be careful to keep them up off the tire. THey still catch the stuff getting flung off the tire. They just don't overhang the sides.

Thank you. I figured there was some kind of general rule about this but I could not find anything on it.

Found a lot of stuff where people seemed like they were TRYING to sound like they know what they were talking about. But nothing felt credible.

I don't ride through active volcanoes. I kick up a little road grit here and there but nothing crazy. I just want to stop flinging dirt and grime at my rear derailleur and taillight and have it look halfway decent.

The black mounting arms and the clean lines on these seem to accomplish that. And $30 is a price I can be THRILLED with even if they aren't perfect.

I run 32 mm tires on 35 mm SKS longboards. that's about the limit of the 35mm fenders. I put 35mm studded tires on it and while it still works, I'd prefer it to be a bit wider.

I've also got 38 mm tires on 45 mm fenders, and lots of room on that. I'm planning to mount 40-mm studs on them. Should work fine also.

The 10-mm rule is just a suggestion. You're not compromising anything by violating it just a little.

had fun last year mounting 53mm SKS fenders on 2 bikes for 45mm Riddlers & 40mm Marathon studded winters. wound up having to cut both front fenders to raise them higher for more clearance

before


after


before


after


after


you can make your own mounting parts but so much nicer to buy stuff like this

I bought the Planet Bike 45mm fenders yesterday. LBS didn't carry them but can get them. So I'm happy to order from them instead of Amazon.

Should have them tomorrow so I can install them over the weekend.

The Planet Bike fenders ended up fitting great.

Well the back one at least. I haven't figured out how to mount the front one yet so it looks nice as my fork doesn't have fender mounts. I may not even mount the front one as my down tube is pretty wide and kinda works as a built in fender. I was more concerned with the rear when I bought the fenders anyway to keep road grit and slop out of my tail light, out of my deraileur assembly, and off my back.

Took me about 2 hours to get it perfect so it's even all the way around and solidly mounted. Had to do some custom mounting to get it perfect but it ended up looking really good. It fit the 38mm tire fine as long as I kept it elevated a little bit. One of the adjustable hanger mounts clips to the inside of the fender and decreases the width in that 1 spot. So I had to get creative.

All in all I'm really happy with it. I haven't hit and slop while riding yet to see how well it works though.....I'll try to start aiming for some tomorrow.

The only thing I don't like about them is the Planet Bike logo emblazoned on the back. I am not their rolling advertisement so I'm looking for something to cover that up. I could do the sensible safe thing and cover it with black reflective tape so you can't see it while it adds safety...but I'm leaning more towards a Star Wars Rebel Alliance logo decal because 'character'.

Doesn't the fork bridge between the stanchions have a hole in it? Mine does! Also, you should be able to fashion a P clamp (encase it in shrink wrap tubing) for the bottom if you have no holes on the bottom of the leg.

pics or it didn't happen ;-)

It does. That only holds it at the top though....its' not enough. It needs the support arms to support it lower or it bounces too much.

Crummy indoor pics because it's dark outside right now.

But you get the idea.

I think it looks okay with only the back one. Most of it's hidden under the rack anyway.

The reflector pictures is because I accidentally had the flash on for that pic and I just thought it looks cool. So sharing...

good job, looks great, pics are perfectly fine, don't give up on the front

It's not so much a matter of giving up on the front as it is deciding if I actually want the fender on the front.

It doesn't cause as much spray as the back tire and I like the look of the exposed tires. The rear tire already isn't exposed much because the rack and panniers and what not. I'm still deciding.

The front doesn't have the obvious mounting options but it's MUCH more accessible than the rear (no bag rack to work around) so it'd be easier to install if I put my mind to it. I'd probably alter the fender support arms and use the holes on the fork intended to mount a front rack. Or I'd cut the fender way shorter and just have a small section at the top to keep spray from going up into the head tube. If I did that it could bolt to the cross piece with a single bolt and would probably be sturdy enough if it was shorter.

Generally water comes off, mostly, the center, of the tire... so wide wrap around mudguards are not that important..

but a mud flap on the lower end of the front one may be..

Planet Bike makes a mud guard for these fenders. I think it's like $6 with free shipping.

Does the extra flap really make much of a difference?

Oh and I decided last night to put the front fender on. It rained yesterday so there were giant puddles everywhere and like a 10 year old I said "Puddles!? I must try out my new fender by hitting these puddles at full speed!!!"

Long story short....back dry. Front wet.

So I learned the true value of fenders and will get the front one on there.

If it comes down very close to the street , you get less wheel spray onto your feet..

Yes, the extended flap does make a difference. Pretty much keeps your shoes drier in the wet, and keeps the spray down for the guy behind you.... I started out with regular length on their hardcore fenders on my Crosstrail, and switched to the long ones - made a difference enough, to also put them on my Sirrus.

sometimes ... just sometimes ... the bow wave breaks just right so that it all goes out to the sides. but don't count on it

Hold my beer...

It took some doing but I got the front fender on and looking good.

I had to modify the support arms and the mounting brackets.

I ended up mounting it to the 5mm holes intended for a front rack. I had to cut the support arms to make them short enough to mount it to high. And I had the seriously modify the brackets. I ended up breaking off a plastic casing on the bracket and bending it so it mounted properly on the forks at the correct angle for the support arms.

Then it was just a matter of tweaking it until it was the right height off the wheel and centered on the tire.

All I need now is a puddle to ride through!

What you did looks good. As if it was intended to be this way. However, that front fender isn't long enough to protect your feet and the drivetrain. So when you ride through that puddle, it'll spray some dirty water right at the crankset/chain/pedals. Just something to be aware of. Perhaps you could fashion some kind of rubber flap to extend the protected area.