In my motocross and desert racing days my bikes all had 21”/18” wheels. Since the bike’s OEM wheels are both 19ers I wanted to find a 21” front wheel. Well after researching they are almost impossible to find. Because the bike is a hybrid between a mountain bike and moped the hubs on the Sur Ron are MTB, but the rims are motorcycle. A lot of guys on the Facebook group have used 26” MTB rims on the front. The overall diameter of a 26” MTB rim/tire is the same as a 21” moto rim tire.

21er with a Hope 225mm rotor next to my stock 19er on the rear. I’ve gone with Shinko 244 tires for the terrain I most often ride.

But what dissuaded me from going that route are the tire choices for a 26er. They are almost all exclusively MTB tires. 21 inch motorcycle tires are the defacto size so guess what? TONS of tire choices. And MTB rims/spokes are designed for bikes that weigh about 40 pounds. The Sur Ron weighs 110 pounds in OEM trim…. So I researched a few places and decided on using a guy out of NYC to build my wheel.

I had mentioned to a private Facebook group about my purchase of the 21er and in typical forum fashion ALL OF THEM PooPoo’ed the idea. “Too heavy” was their consensus. Yet when I asked them what they didn’t like about the handling of the 21 inch rim, NONE OF THEM had ridden a Sur Ron with a 21!

When I mentioned that to my well builder, here’s what he said:

” Okay the extra weight thing;;;;

#1 yes it’s more weight but when you ride it you’ll see how much better your bike is “planted” on the trail/road!

#2 lighter mtb wheel is a much more of a loose feeling front end that at speeds will want to drift off of your line! Really bad on fast dirt roads!

#3 mtb tires don’t work on a 130+ lbs motobike! Motoped community has all ready tried to

I’ve tried the moto wheel in the back & MTB front for about 3 months.. trying many many 26” tires and at the end,they just don’t werk well because of the extra weight of the bike…

I had to run 45-50 psi on mtb front so it wouldn’t get pinch flats on rocks and roots. That much psi the tire doesn’t work that well or ride well!

Motorcycle tires I use 22 psi or so and grip the road/trails awesome”

So after mounting and trying the 21er all I can say is WOW. It has transformed the bike into a very capable off-road bike. Rutted downhills are not scary now, holding a line in a turn is just like it should be, planted. Bumps are smoother than before. All in all I would never go back to the 19 inch rim. What are the downsides? The OEM front brake on the Sur Ron is overwhelmed by the added weight of the 21 inch tire rotation. In the past I could do stoppies with the 19s. Not so with the 21s. So I have ordered a 224mm (9”) rotor to replace my 203 in hopes that solves the issue. If not then I will upgrade my front brake to a Magura MT5s. I love those brakes and have experience with them. Of course if Brembo made MTB brakes I’d be SO THERE!

Update: I mounted a 225mm Hope floating rotor and the bike stops on a dime. You can read about it in my section on Brakes.

12 Comments

  1. Just went and picked up my 21″ wheel from Josh. Turns out he lives 45 minutes from me. Really nice guy, and really nice wheel. Miss you on the FB group, but I get it. Glad to see all you have done here. You have inspired me to spend lots of money. 🙂
    Best,
    Bill

    • Heya Bill thanks for coming by! SO glad you got to pick up one of Josh’s wheels. He really does an excellent job. Also glad to hear he’s a nice fella too. I do miss many of the folks on the group, but man Facebook just is NOT something I want to support. Especially with the US elections coming up next year.

      Sorry (kinda not too! LOL) about spending your hard earned after tax dollars. I get that too! Unfortunately my dad taught me to write down EVERY PENNY spent on recreational items so I can see just how much dough I’ve spent! I mean that was when I was 13 years old, but I’ve done it ever since….the bastard ruined me! LOL

  2. Could I get your contact in NYC for the 21″ wheel? I too am an offroad guy (singletrack). My other bike is a KTM 300 XC. I REALLY want to get that 21″ front going. Thanks so much for this awesome website.

    • Hey Andy thanks for stopping by. You can search for the builder of my wheel, Josh Nowell on Facebook. Never ridden a KTM, but I owned a Penton which is the original brand that became KTM. I personally love the 21er on the bike. I did upgrade to a 225 rotor though to compensate for the extra rotating mass of the new size rim/tire. Just look up Brakes on my site. BTW how did you find my site? Thanks.

      • Thanks a ton Mark. I actually found you from a link on Facebook.

        • Thanks Andy. I use to be one of the admins on the Private Sur Ron Facebook Group. But because I have strong opposing views to Facebook in general, I deactivated my account. I wanted to start this website to help other owners in the Sur Ron space. There are not a lot of resources other than forums which I find most are there who ‘just want to be right’ so I avoid them like the plague.

          I was just hired to write a long term review of the bike by WebBikeWorld and it should be published in a few weeks. Thanks for stopping by and letting me know the site has helped you. Makes all the work worthwhile.

  3. Thx for sharing this!
    I wish to do the same with my Sur Ron X.
    What front hub and spokes did you use? 36 spoke rim, right?

    • Dmitry, the OEM front hub. Yes it is a 36 hole rim. The trick are the nipples. A MTB hub which the SR uses mated to a moto wheel requires special nipples. 12 gauge spokes were used. Homes Hobbies was the only supplier I know of the nipples. You can also contact Josh Nowell on Facebook to have him supply a built wheel.

  4. any tire interference issues with the increased wheel diameter during full compression travel?

    • The only issue I’ve run into that you won’t is with my little bottle holder. IF I’ve turned the wheel left and land a jump flat then the tire will hit my little drink holder. But other than that nope, no issues. The trials type fender I’ve rigged up can hit sometimes, but no biggie for me. Next to the front forks the 21er is my favorite mod for handling….and tire selections.

  5. thank you ! in mtb bike applications I experimented with differing traction level tires front/rear & nothing had the positive feeling of a larger ie larger contact patch & rake/trail changes on the front I’m very surprised this is not the ‘new standard’ in mtb bikes – whens the last time you purchased similar wheel sizes in motorcycle F/R

  6. Another good thing about using moto rims is you can use Tubliss. I am using it with a Shinko Fatty tire which is a lot wider and taller than a normal tire. 90/100. Plus I am running 1 psi which really smoothes out the ride. I will have to go higher as the tire wears in but 1 psi works great right now.
    I’ve been thinking about a Sur Ron but went with this $1000 Chinese motorcycle that comes with 21 inch wheels. Power wise, I think it is comparable to the Sur Ron but it sounds like a mini Harley!
    https://advrider.com/f/attachments/shinko-fatty-jpg.1816586/


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