RadRover : how slim (Tires) can we go ?

[Kyogiro]

I already replaced my rear tire with a Jumbo Jim 26x4 on my rear wheel. I have another one waiting for the front wheel.


I've been mostly riding my Rad Rhino (Rover) on pavement, I was wondering if anyone has tried to fit 2.25 wide tires.

 

[AHicks]

The 26x2.25's, in my mind, are way too narrow for the extra wide rims used with the 26x4" tires. The stock rims are usually about 80mm wide. Rims for 2.25 tires will be something closer to 30mm wide. What you CAN do is drop down to something like a 26x3" tire using the stock rims. I've done this using 26x3.0 Kenda Flames with decent results (though they may be hard to find), but there are others in that size range as well and my bet is they'll have similar results.

 

[Kyogiro]

Thanks. I've seen users successfully switching to 3 inches tires.

I was wondering for 2.25" due to the larger choice of tires. Probably next year, I'll change for 3" tires after using my current Jumbo Jim ones (which should last longer than the Kenda stock ones according to reviews).

 

[ExPatBrit]

I installed 3 inch street tires, quieter and faster and got slightly more battery range.

Three caveats, speedometer will read high, you can scrape the pedals when leaning over and cornering and the bike leans more on the kickstand. My original stand snapped off.

 

[AHicks]

You can have 27.5 (or 29'er) rims laced on to your existing hubs too. Getting ready to do that on my fatty (27.5 in my case). After giving them a fair try, I consider the 4" tires a mistake here. That's me though. Some love them!

Worth mentioning maybe, is that the balloon type tires like the Schwab Super Moto-X and Big Apple lines, do a REALLY nice job of providing both a nice ride AND low rolling resistance. Designed to be run from 40 to 20 psi, when run down in the 20-30psi range they provide a GREAT ride, and still manage to handle SOME sand well. Super Moto-X come in 2.4 and 2.8 widths..... just sayin.....

 

[m@Robertson]

Assuming they are 80mm rims, you can go as far down as 2.35" with a Super Moto X. 2.5" with a Maxxis Hookworm is a very common thing to do for height-challenged riders looking to take the bike down as far as possible (typically petite women). Ride comfort is compromised though. Expect a hard ride like you would get with a road bike with 100 psi tires.

I did the Super Moto X tires on 80mm rims on a fast bike (not a Rad) and I also used an oversized tube to ensure the tire formed properly to the hook bead rims. Fitment was surprisingly good. But the ride absolutely sucked. At high speeds on the street (28+) it was just not worth the trouble.

 

[AHicks]

Re: hub width adapter, I'd approach something like that with a healthy dose of caution for a disk brake equipped e-bike. That rotor needs to line up on the caliper. Using a spacer of some sort is just about guaranteed to screw that alignment up. That's for starters. Then there's chain alignment issues something like that might get into. There's also the very real possibility of a need to change the amount of "dish" used to center the tire over the hub in a manner where all that lines up.

Not saying an adapter like that can't be made to work. Saying there's a good deal to keep in mind when considering one.

 

[m@Robertson]

From a purists' perspective I agree doing new wheels is the 'right' thing to do mechanically, but realistically you can get the desired result with just a tire.

And its reversible if you decide you want to go back.

I know the guy who did the yellow bike. Pic is from 2018 and he still has it like this. Me... I didn't last past 6 months and maybe 3000 miles. Both bikes use 80mm rims. The yellow one is 2.5" Hookworms. The orange one is 2.35" Schwalbe's. The sidewall/casing is actually straight up from the rim on both of them.

 

[AHicks]

From a purists' perspective I agree doing new wheels is the 'right' thing to do mechanically, but realistically you can get the desired result with just a tire.

And its reversible if you decide you want to go back.

I know the guy who did the yellow bike. Pic is from 2018 and he still has it like this. Me... I didn't last past 6 months and maybe 3000 miles. Both bikes use 80mm rims. The yellow one is 2.5" Hookworms. The orange one is 2.35" Schwalbe's. The sidewall/casing is actually straight up from the rim on both of them.

On the bold, in your opinion, would the "desired results" include things like minimized rolling resistance and a great ride? Would love to know more about how rim vs. tire width play here.

I have 2 other bikes (both city bikes). 1 is a 26" and the second a 27.5, both equipped with 2.4" Schwalbe Super Moto-X tires front and rear, mounted on 30 and 32mm rims. Those bikes both work GREAT. They both ride better and pedal easier than the ex-fatty now running 26x3" Kenda Flame tires on 80mm rims. Those tires (the Flames) are about the same width across the tread as the rim is wide
(80mm= 3.14"- giving a great looking "square" appearance ). It seems to ride rough even down under 30psi. If I go much lower, like down into the high teens, I get into the dreaded self steering issue. My opinion above based on this experience.

Worth mentioning maybe, is the fatty is a Bafang Ultra Powered Rize. My current plan is to do a rim swap, and install a 2.8" Schwalbe Super Moto-X on the back and a 2.4" Super Moto-X on the front.

 

[AHicks]

So I guess something like Schwalbe Moto-X (26 x 2.40) might fit RadRover just fine?

Schwalbe Super Moto-X wired tire Performance SnakeSkin HS439 Dual DD GreenGuard reflective

Schwalbe Super Moto-X wired tire Performance SnakeSkin HS439 Dual DD GreenGuard reflective ☆ free shipping from 300 (UK)

www.starbike.com

Yes, they'll fit. The bike will roll with them installed. My question is more like will they perform as designed?

 

[AHicks]

Thanks for the charts Timpo. I rest my case....

Those charts pretty well match my experience. I like the second one better as it describes what you might expect to happen when you get too far away from "suggested".

There's still the point regarding will the skinny tires "work" on the fat rims, and clearly they will. Story there is about working as designed, and as the charts show, they do not. Point being, I suppose it depends on your interpretation of the word "work". So the questions that need to be answered - are you looking for something you can get by on, or something that will allow the tire to work as designed?

 

[Gordon71]

Thanks. I've seen users successfully switching to 3 inches tires.

I was wondering for 2.25" due to the larger choice of tires. Probably next year, I'll change for 3" tires after using my current Jumbo Jim ones (which should last longer than the Kenda stock ones according to reviews).

What did you get for mileage on your Kendas? I've got about 2700 miles on my Rover (mostly pavement and groomed gravel trails) and there's still life left in them. I expect I'll replace them during the winter down time and will probably go with a street tire this time. Either 26X4 or 26X3 but will probably stick with the 4's as I'm too cheap to replace my tubes and Tuffy liners.

 

[m@Robertson]

That looks like the easiest solution. Just change the tire.

How's the speedometer though? Did you have to change it?
I know typically people just set their speedometer setting to 29 inch for 26 x 4.0 because of larger tire diameter.

Yes you do need to adjust your tire diameter in your display. Always necessary when fiddling with tire diameters. 29" is for big tires like a 4.5-4.8. 28" is what I am using right now with 4.0" tires on that orange bike. Arrived at via measuring.

 

[m@Robertson]

I believe 28, 700C and 29 are all the same. People just call them differently.
Though, I could be completely wrong, I know they're all interchangeable from my experience.

The correct answer is yes, no and maybe. A '29er' is a 700C road bike rim in mtb width. 700C is not accurate as a diameter. Its 622mm using the metric ETRTO standard found on the side of the tire. In the EU, 28" is commonly referred to as equivalent to 700C but the ETRTO diameter is 635.

Here take a look at a Schwalbe tire page. Expand out its tire size section down at the bottom. You'll see 700C and 28" tires side by side. Look at the ETRTO measurements.

Delta Cruiser Plus Road Bike Tire | Schwalbe Tires North America

The PLUS version of the Delta Cruiser road tire has that classic center rib profile, is versatile and offers pleasant rolling characteristics for you…

www.schwalbetires.com

I also think you might be missing what the '29' means on the display: '29' on a 29er is used as a term referring to the outside diameter of the tire on that 700C/622 rim (29"). '29' on an ebike display is the same thing (unless your display manual says differently). So typically on your various KT, Bafang etc. DIY/aftermarket displays the value is always the measured outside diameter of the tire. This makes sense because of course our subject in this thread is about different outside tire diameters on the same wheel diameter.

Life is a lot simpler if you dispense with imperial measurements and instead go with the metric system. The ETRTO on the side of every tire is a lot more useful and generally less influenced by marketing. The first number is the width of the tire casing, and the second is the bead seat diameter of the rim/tire. Easier said than done I still think in imperial sizes myself but I refer to the ETRTO when I want to know for sure if something fits a bike frame or fork.

As for the 'maybe'... 28" tires are often close enough to fit without issues on a 700C rim despite the 622 vs. 635 issue. Or so I've heard. Not something I mess with, personally.

 

[m@Robertson]

Well not likely, because 2.4- 2.6 tires are designed for 25mm to 40mm max.
So obviously RadRover's 80mm is too wide for optimal performance.

Well here's where the instruction manual ends and experience picks up. People do this all the time so what are the real world consequences? Reality is you can fudge things quite a lot and you'll be fine. Can you put a too big tire on a too narrow rim? Up to a point. Will there be consequences? Yes, ranging from 'totally unnoticeable' to 'tire falls off and you crash'. You need to know what you are getting yourself into via experience. If you don't, that chart gives you some guardrails, although personally I prefer the much more complete DT Swiss Tire Pressure and Dimension guide (which is still conservative, but a good starting point).

https://pictures.dtswiss.com/uploads/WPR1400AAQXKA04431/MAN_WXD10000000866S_WEB_ZZ_001.pdf

What about the reverse? Too wide of a rim for a too-small tire? Consequences will range from 'totally unnoticeable to 'tire does not seat on the rim and you crash'. Here again you need to have the experience to know what you are up against. In this case the internet is your friend as you can see plenty of folks who have done this as it is a very common thing to do. As I noted above, I personally took the extra (and unusual) step of using an oversized 3.0" tube to ensure the tube helped the tire hook into the rim with authority. Most folks don't take that extra step and it still works for them.

On the bold, in your opinion, would the "desired results" include things like minimized rolling resistance and a great ride? Would love to know more about how rim vs. tire width play here.

The desired results were ultra smooth rolling resistance on hard rubber. I loved the ability to lift and just coast for what seemed like forever, unpowered. Is that part of a great ride? Yes. But there were undesired results too. That higher pressure tire with minimal (albeit sufficient) sidewall had a whole lot less cushion, and it changed how the bike handled imperfect road surfaces dramatically. Remember an ebike goes faster than a bicycle. So you come up on things faster and impacts are magnified by speed. The wheel's strength was just fine (a hand built wheel using double-wall Weinmann rim with DT Champion 2.0 spokes and brass nipples, so thats quite a bit stronger than any machine-built Chinese wheel).

As I've said it is not something I would do again, but it is something I know plenty of people do and never regret.

 

[m@Robertson]

Well not likely, because 2.4- 2.6 tires are designed for 25mm to 40mm max.
So obviously RadRover's 80mm is too wide for optimal performance.

Something to note: That chart you linked is not gospel. If you look at the DT Swiss chart, they use increments of "2.35" to 2.6" as the closest to your 2.4-2.6 range. For a 2.35 tire, the possible rim combinations range from 20mm to 51mm, where the 'possible' combinations are that range, but the 'ideal' combinations are 25-33mm. For a 2.6" tire, max possible are 23-51mm, with ideal being the same 25-33. Also if you have hookless rims the separate chart gives slightly different guidelines.

I had a 2.4" tire that fit my front 20", 19mm inside-width rim on my Bullitt just fine. Thats outside the guidelines, and I only did it because I was sort of stuck and had to, but I was surprised to see it worked fine (I replaced that wheel with one that was 33mm with a 27mm inside width).

So the two charts are different in their recommendations, and experience differs as well. The point being these are not hard and fast design rules. Some judgment is in play here.

Also note the Rad 80mm rims you mention... 80mm is the advertised external (marketing) width. Thats different from their inner width which is what you use for measuring tire/rim compatibility. Inner width on an 80mm hook-bead rim is typically in the ballpark of 73mm. Subtract 2mm for each rim wall and 2mm for each of the hooks as a good WAG.

So when figuring up stuff like this, if you don't know the INNER width and you want to do calcs, pull the tire off and get out your calipers.

 

[AHicks]

Struggling with something these charts aren't showing. I have to wonder if there's an assumption regarding the design of the tires? Consider for a second a Schwalbe Marathon with it's stiff sidewalls, and then a balloon type like a Schwalbe Super Moto-X. They both have outstanding reputations for our purposes, but I believe the 2 tires are like night and day regarding designs. The Marathon is an outstanding tire, that is generally run with twice the air pressure that the Super Moto-X (and some similar tires like the Big Apple) typically run. If you've ridden the same bike equipped both ways, the extra pressure run in the Marathons makes them feel like you're on a roller skate riding down a brick road. Remove that tire and install one of the balloon types (like the Super Moto-x X or Big Apple), and things are very noticeably smoother. Expansion joints and dried out cracked pavement area seem to disappear!

This is what I'm talking about when I say "ride". Talking about the amount of vibration transferred to you wrists and your back side as you ride on a paved road.... minimizing that vibration.

We've seen the note regarding too big a tire on a rim (the Bell shape) causing a stiff ride - assuming it would be a softer ride if the tire and rim were properly matched. So what about when taken to the extreme, where we're installing a 2.25" tire on an 80mm rim?

 

[AHicks]

In my experience, no two tires are the same. Continental for example, I found they're way narrower than what's indicated on the sidewall.

I know it's obvious but if you really want to know for sure, contact the manufacture.
Call Schwalbe and say, "I can put 26 x 2.25 size Marathon Plus HS468 on Rad Rover's 80mm rim?" and they will tell you yes or no.

I think it pretty safe to assume what they're going to say. Where they'll stumble is the why.....

 

[Kyogiro]

For now, I had to put my spare Jumbo Jim 4" on the front wheel because my Kenda tire gave out yesterday. Second puncture in less than a month and this one couldn't get fully sealed with my tubeless liquid sealant. So I decided to change the tire since I have to use my bike pretty much everyday. The stock Kenda tires lasted me about 2000 miles (3000 km, this one was really all used up) for rear and 2500 miles (4000 km, probably could have gone longer if I would have worked on (temporary) fixing the puncture) for the front.

I'll probably test 3 inch tires next time but those Schwalbe Jumbo Jim are rated for a long(er) lifespan.

 

[AHicks]

Noteworthy, to save others the time to look, is the fact the Jumbo Jim is a knobby tire