What is my actual max tire size capacity?
 

I have a Trek Domane 3 Al Disc (https://www.trekbikes.com/us/en_US/b...-disc/p/33082/). The factory tires work great for hard surfaces, but I installed some 35mm cyclocross tires to try gravel riding. I find that gravel riding suits me well, but would like to try some larger tires. Trek says that 35mm is the maximum tire size, but my current 35mm tires look like they have miles of clearance and I know that there is a great selection of tires if I can put 38mm tires on the bike. Can anyone help me understand whether 38mm tires could work on my bike?

https://cyclingtips.com/2021/01/trek...disc-4-review/

The maximum tire width that you can safely user depends on the inside width of the rim. There is a page on the Sheldon Brown website https://www.sheldonbrown.com/tire-sizing.html that probably has more information than you need. Check out the part that shows how to measure the inside width of the rim and then go to the chart further down the page (it's bright green and red) that shows what you can safely use.

Really you just have to worry about how much clearance you want between the tires and frame or where ever they will rub first. It's really a personal preference thing and what kind of surface you ride, IMO.

Some wouldn't feel comfortable for their safety with any less than a ¼" . Some might feel comfortable with whatever size won't rub.

If you ride in mud sometimes, then you might want to have more clearance. The gumbo mud around here can stick to your tires and build up even beyond a ¼"..

I tend not to worry too much about rim size because IMO, you'll probably max out your tire size with the frame before you max out the recommended max tire width for that rim. Unless perhaps you have a very old bike from the days of 18 mm tires and even then I doubt you'd exceed the max width rec. first.

According to what I can find, the inside width of the rims is 21mm. I found a table (https://www.lightbicycle.com/newslet...cycle-rim.html) that claims a 21mm inside rim width can accommodate all the way up to 43mm tires. I don't want to go that high, and am hoping that 38 will work fine. I am wondering if anyone on here is maybe running 21mm inside width rims and has used 38mm tires and could give their thoughts on how it worked.

I even found a photo that someone took of the inside width of their wheels, so I feel very confident they are 21mm inside width.
https://cimg9.ibsrv.net/gimg/bikefor...fdf15b71e5.jpg

If you’ve ever seen a 90s mtb with 2” tires in skinny mavic rims you wouldn’t worry about your rim width.

Tires grow in diameter about as much as the change in width. So if you know where on the bike the least amount of clearance is, then you should know how much bigger a tire you can get.... Once you decide how much space you do or don't want to leave.

If you are going for tires with a real aggressive tread or knobbies, then that probably isn't part of any width used in the sizing. Also, using the ISO size will make it easier all around. Don't use any inch sizes written in big letters on the tire.

Dont think twice about a 21mm internal rim handling the tire sizes we are talking about here. 15mm internal rims were used on 2.1" MTB tires all the time for years and years. You are plenty good.
The CyclingTips website shows a 42mm tire doesnt even contact any of the frame, so a 38mm tire will be OK there.
The only potential issue is the tire contacting the front derailleur arm. Your r3000 Sora FD is designed the same as the Tiagra FD in the linked review. It has a really long mounting arm and when the chain is in the big ring the FD arm may be in the way. Since you want to use a 38mm tire and what was tested is a 42mm tire, you may be fine.

The problem is that rim widths vary and the way tire manufacturers measure varies as well - a 38mm tire from Manufacturer A will measure differently than a 38mm tire from Manufacturer B. To alleviate much of the guesswork, some tire manufacturers have started to publish WAM (width as mounted) and RAM (radius as mounted) specifications. Very helpful if you can find them.

If they don't use WAM/RAM, then your best bet is to use something like an Allen wrench as a feeler gauge to see how much room you have in the various tight spots. In general, manufacturers suggest 4mm on each side. Unfortunately, this only gives you guidance on sizing up with the same make/model of tire as measured.

Yes, AR36 Falcon rims with 38mm Specialized Pathfinder Pros. They work great. I wouldn't go wider than 38, despite what Light Bicycle says.

A possible problem is the increase in tire diameter. Tires get taller as they get wider. My fork limits the front
tire diameter long before the rear.

My Domane has the Pro 3v's that are 25mm internal and I had 40's on the rim and had plenty of space, might have been able to put a 42, but think it would be sketchy. The tires were the Bontrager GR1Team Issue Gravel tires. For the road, I ride the 30mm Pirelli's.