Wednesday, September 08, 2021

Project Wide Gravel Wheels v2: Initial Ride Impressions

Project Wide Gravel Wheels v2 on the Noble Bikes GX5
 Now that I've gotten past Gravel Worlds and a couple of other things I have been able to - finally - turn my attention back to the PWGWv2. The last update was in early August, which if you care to refresh yourselves on this project, can be seen here

Initially I set the rear wheel up as something I could use on my Noble Bikes GX5. That's because of Gravel Worlds and my ongoing review of the WTB CXR Carbon wheel set. Now that Gravel Worlds is over, I eventually am going to swap things around again. But the initial ride was with the Nobel Bikes rig as seen here. 

As far as how these ride? They are smooth! The tires were run at something in the mid-30's for air pressure and the tread, being more flat to the surface, really buzzed and hummed on pavement. But this made them corner like MTB tires on gravel. Pretty amazing, actually. Speed-wise? I think that takes a bit away, but I did not compare any roll-outs or back-to-back tests of wheel sets. And I don't think I will need to go any further with this than I have. Read on for the reasons why.....

I've mentioned before how I was not completely impressed with how the tires set up like on these Spank rims. But, after giving this some thought, I have a reasonable explanation for what has happened here and I think it is telling for anyone else thinking about putting a gravel tire on what amounts to a mountain bike type rim. 

Notice that as you spread out the tire's beads from each other, it draws the crown of the tire downward.

As with anything, 'more' is better to a point, then it becomes a very steeply falling curve toward 'not-so-good'. Such is the case with wider inner rim widths. When road rims were 18mm-20mm wide internally, bigger tires than 25mm would suffer from an excessive amount of 'light bulb effect', especially as you got above 30mm in width for tires. Tire pressure has to be kept higher when tires form such a profile because if the tire isn't rigid enough, it will squirm sideways when side-loaded, especially in curves and when accelerating. As internal rim widths get wider, this spreads each bead of the tire outward, which in turn starts to draw down the crown of the tire until it no longer resembles a light bulb in cross section. 

That's good for tire pressures, comfort, traction, and especially with tubeless tires. But when the bead on each side of a tire gets too far apart due to a very wide inner rim width? Then the tire's crown flattens out too much, it draws inward toward the rim, and the wheel over all will have a shorter diameter. This will affect handling and,to a lesser degree, gearing. It also can increase rolling resistance because the tire patch now is wider than it would be with a narrower inner rim width. Additionally this can affect  how tire sidewalls flex, also contributing to higher rolling resistance and a stiffer ride feel.

So, what is right? Well, I can only speak to my experiences, but I am of the mind that there is no way I would normally run this 700 X 42mm Resolute on this wide a rim. Note- The Spank 359 rims have a 30.5mm inner rim width. Many "gravel" rims are 24mm-26mm inner rim width and - in my opinion - that is about right. At least for 38mm-45mm tires, it is about right. You'll get optimum bead to bead spread and the crown of the tire won't get flattened out too badly, or not at all, since most tires are being designed for rims with that inner rim dimension range. 

Conversely, running less than 38mm wide tires on - let's say 25mm inner rim width rims - is also not optimal. You will begin to get more and more of that same effect I have noticed with my Resolutes the narrower the tire gets. I would say anything 32mm-30mm is borderline not very good at all, and anything less wide than that is ridiculous. But - you know - someone out there is doing it. They will think I am full of it because "it works great for me and has for years!". 

Like always - I say "You do you." I know what all this adds up to for me. 

And that is that Project Wide Gravel Wheels v2 has shown me that 30.5mm inner rim width is too wide. (Note- These Spank rims did not make the tires any wider than about 45mm, and on 25mm inner rim width rims they come out to about 44mm anyway and they have a much better profile.) So, now what? Well, a wider tire, that's what! As stated in a previous post on these wheels, I am going to mount some 700 X 47mm Teravails and see how that adds up on these rims, and if that doesn't work? Yeah.......about that......

I probably do not have the right bike for these wheels if that is the case. I'd probably need something like a Fargo, or that new Tumbleweed Bikes Stargazer, but.....those are Boost bikes, and my hubs are not. Bah!  So, I may end up blowing these wheels apart and re-lacing up some Velocity Blunt SS rims I have that are 26.6mm inner rim width. OR I could get some QR end caps for the DT Swiss 350 hubs and make these wheels my Fargo Gen I wheels. I don't know...... Anyway! 

There are a lot of steps to go before I have to worry about the 'end game' for this wheel set. Stay tuned!


Dan Buettner said...

Problem Solvers make kits to fit non-boost hubs into boost frames & forks.

There are centerlock versions too

Guitar Ted said...

@ Dan Buettner - So, you are stumping for me to get a new frame and fork? (Just kidding!) Thanks for the tip!