Schwalbe Marathon sizing 700x38 vs 700x35
 

I am looking at picking up a set of Schwalbe Marathon for an older t trek hybrid touring bike i am building up. I have built up the exact same model using 700x38 and it was just a mm away from the fender or so at the fork crown. The tires are really tall.

Curious to know if 700x35 would be much shorter..?? If it isnt id rather stick with the larger tires just because they seem more comfortable/versatile over the long haul and try and deal with the lack of clearance. In my previous build i have had sticks and even small stones get stuck in the tread and actually hit the fender at the crown. I dont suspect that little of clearance is great once you are out on tour. SOmtehing about that spells disaster...and it seems it could be avoided.

According to this site: https://bikecounterculture.com/2017/...er-calculator/ you are looking at 4 mm of difference, which, in terms of fender clearance, would only be 2mm difference. That seems like next to nothing, but if it's already tight clearance, it might be worth it to size down. I maxed out my tire size in relation to my fenders, and it was fine until I went through some mud. Then it was miserable, with me constantly stopping to clean out enough mud to move forward a little more. I do like a wider tire, though. If I were in your shoes, I might look at what my options might be for a fender with better clearance, or even one of those, under-the-downtube spray-catchers.

without photos, if its truly 1mm clearance, as you say yourself, its just too bloody close. I'd size down going from your own accounts of same bike/clearance.

do take into account the possibility of maybe dremeling out the fender top mount thingee, to bring the fender up a smidge, or even dremeling out some of the fender itself, to allow you to bring it further up. Ive seen someone here post photos of doing this, but having to add two mounts at the fork area, essentially splitting the front fender into two parts--but to me this is a lot of work, just go with slightly smaller tires like the 35 or 32s...
I put 32s regular marathons on an old trek hybrid with fenders and as you say about stuff getting stuck inbetween, it can happen and at a certain point you have to use common sense and just go with smaller tires (unless you go the "split fender in two" route, which is a bit complicated)

Yeah...i am not against cutting into the fenders around the crown to raise them up and then re-enforcing around that are if need be. I just dont want to do it if i dont have to. I dont have fenders yet and want to find some used so i wont feel so bad if i have to chop them up.

For my Jamis Renegade that I use on gravel, rail trail, towpath type rides, I put on the 35mm Schwalbe Marathons and they are plenty wide/comfortable/durable for those type of surfaces. I've done a few sections that were closer to technical trail riding and both the tread and the width weren't really up to that - at least at my skill level, since I'm 90% a road rider.

I too have regular marathon 35mm on a bike, a commuter, and they work well at proper pressures for my weight.

Re tire dimensions, don't forget that different room rim widths change a tires shape, so it's hard to get an exact measurement as it will depend on your rims.

yeah..the rims i have are just a tad wider then road rims. They are the stock trek 36 hole titan rims if i recall correctly. I think i will try 35s and see if that is better.

mebbe try 38 rear, 35 front??

10mm of clearance at minimum. Its what I see on websites and fender packaging. You have tires that are too big for the frame to use fenders.
Or keep the 1mm of clearance and ride with an insane amount of caution since the odds of a stick or rock getting stuck in your front fender and flipping you over the bars is a lot more likely with such limited clearance.

For what it's worth, the newest pair of Schwalbe Marathon Pluses that I put on my wife's touring bike measured about one size smaller than stated, measured on two different rims. In other words the 38's that we purchased calipered at maybe 35 mm. But either way, you're running an unforgiving set up and hope you don't get a small piece of gravel to adhere to a tire via hot tar, as my wife once ruined her time trail bike that way when it wore a groove in the chain stay.

& can run the front at a lower pressure, that would make it narrower but probably also a smaller diameter

Here is a picture of the clearance with no fender. Seems like plenty of room. This is with the 700x38. Once you get the fender on there though it is extremely tight. Its probably save to say that a 35 wouldnt get me much more clearance. If i can find a good set of used 45c fenders i think i am going to try the cut out method on them and then run tab mounts on both sides of the fork doing some fancy dremel work.





https://cimg9.ibsrv.net/gimg/bikefor...b178692cd3.jpg

I so wish my Trek had been made for bigger tires. I switched to 35 Marathons (which was a huge improvement over the Conti TopTouring 32s that came stock) but now have only 6mm space between the fork crown and the tire. I feel like grinding some fork crown away so that I can fit a fender there.

that doesnt look that bad, but of course I dont have the bike and fenders in front of me.
good luck with trying stuff

yeah with them off the bike it looks fine. That gap is about 10mm. Its very hard to tell what kind of gap i have once the fenders are on because you cant see up in there but it is tight.....i do know that. I hate to butcher a pair of fenders by cutting around the crown but thats better than the cost of getting strand due to a destroyed front wheel or ....worse....the emergency room visit or ride in the ambulance i guess.

I'm sure you can find some Images of mods that folks have done, and as you say, finding some used fenders would be nice to experiment on.

If you use narrower tires you could use narrower fenders and get the fenders higher into the crown with out cutting them. It is possible to heat form plastic fenders to fit all the way up. I would recommend solid color fenders. On my bike with clear and silver fenders the silver tape separated off with the heat.

I can't help much with the fender clearance as I don't use fenders on my Trek 520, but I did run Marathon 700x35 for one season and found them a little narrow for the hilly, rugged roads I often find myself on. When I got a snakebite flat on one such rough road, I switched to the 700x38's, which I've been riding on ever since. 'Little apparent difference in rolling resistance, but noticeably more stable and robust on the downhiils and in the rough spots, and, knock-on-wood, no flats in 3 years. I guess the choice depends a lot on the nature of the roads you intend to ride on.

Maybe consider 32mm for more safety on the front? Locking up the back wheel can be bad but locking up a front wheel can be catastrophic.

I wanted to put fenders on my road bike that has 28mm tires. It looked like plenty of room, I had some spare fenders, tried to install them and it was just too tight to be practical. Sometimes what looks like a lot of room isn't so roomy once you try it.

Echoing what people are saying about the sizing.

I put Marathon Plus on my wife's bike. Went with 700 x 32 but they didn't look any/much wider than the 700 x 28s I pulled off.

Time to put in the reading glasses then!

Take a look on this site. Schwalbe Marathons are tested and the height (and other specs) are measured and discussed.

Good luck.

https://www.bicyclerollingresistance.com/

Marathons and similar Schwalbe with the 3 or 5 mm puncture layer and thick rubber tread are tall tires with a sloping peak compared most others, I think the wideness comparing two different sizes of the same tires is harder to visualize or notice because of that.

I've only had one set of Marathons and they were 26x1.75. I did a lot of off asphalt and even some single track on them. Relatively speaking, I found them to be a hard tire in general and even large adjustments in pressure did not provide much if any change in comfort. Never got a flat and great wear though.

on my previous build i went with the planet bike fenders in a 45 width running a schwalbe marathon 38c tire. I think those fenders might only be rated to a 35c tire. I see almost no options for a 38c tire. I could maybe go with the PB 29er fenders but those are 65mm.....which would look huge. I dont imagine that would help the clearance issues either. Those babies are almost $65 a pop too....

sorry but I dont recall all the details of stuff---but do you still own the fenders rated to about a 35? I guess you dont or you would have tried them on already...
I dunno, a couple of mm's, 1.5 more on either side cant make a real world difference, ie they would do their job most likely perfectly well on 38s also......again, armchair views here on my part...not in front of me.

also not sure if I already said, but your photo of clearance with the 38s LOOKS like fenders would fit in without being overly tight....