Actual Tire Clearances

Ugh. 

i was really really Hoping I try out a gravel race without buying another bike. I already plan on buying another bike anyway. 

such is life. I’ll keep doing my group rides. 

that said-the area it’s narrowest is near the bottom bracket. Flex tends to happen at the top vs the bottom of the wheel. 

The space at the seat stays on either side of the wheel is 45mm and the clearance at the forks is 46mm. 

regardless. I’ll take your advice. 

thanks!

AdamJGross wrote:

that said-the area it’s narrowest is near the bottom bracket. Flex tends to happen at the top vs the bottom of the wheel. 

bnystrom wrote:The most likely point of frame flex is the chainstays, which tend to flex laterally and could cause the tire to rub near the bottom bracket.

Yep, I did the same. I had a first generation Domane, and wanted to ride Almanzo, so squeezed in a 30mm tire, with only about 1.5 mm clearance on the tightest spot. But, it was dry, and fortunately, I never have to worry about putting out 500W, haha!

My friend did some gravel rides, including some very sandy sections, on his ~10y.o. synapse alloy, with 28’s. I would say, go for the widest tire that fits, then just deal with it, don’t wait for a new bike!

Seriously though, claimed tire width is VERY different from actual tire width.

So the best you can do is try it out, or at least find people who have it mounted in the same width of rim as you have and ask for measured width after stretching.
Then consider how muddy it is, how strong and stiff your wheel and frame is to think o about how much clearance you need.
You can test the required frame clearance with your current, narrow tire, by taping up the tight spot, and doing some hard efforts, seeing how close you can get to the tire before there is wear on the tape.

Backing up a bit, let’s think about why we want big tires:
In the front, it helps with comfort, grip, and prevents the front digging in and sending you over the bars. Sounds like you can get a fair bit bigger tire in front.

In the rear, we are looking for low tire pressure in order to increase traction, comfort and reduce rolling resistance on rough or soft surfaces.

The first two are nice, but not essential (see Paris Roubaix), the latter is more important.

Key to remember is that we want wide tires, because they are also tall tires, that can be run at low pressures without pinch flatting or rim damage, so what you can do is the following:

1. Tubeless of course.
2. Run a wide tire on a narrow rim, instead of the other way around. This gives you the same height (to protect rims), with less width.
3. Run a tire with a tough casing. This will also protect the rim and keep the wider tire from squirming on the narrower rim.
4. Run an Crushcore gravel tire insert. This will further stabilize the tire and prevent rim strikes.