Downsizing Tires on Fat Bikes: Your Experience?

[tommybgood]

I'm considering the 2021 Radrover for a potential Black Friday purchase.

I want a comfortable bike, but 4" tires might be a bit much.

Who has sized down to say 3.3" or 3" tires? How was your experience?

 

[m@Robertson]

Painful. If my butt and wrists aren't hurting, my feelings are when I hear the bike smash into something ***at speed*** I failed to avoid. Ride enough and that happens often in a day.

I loved the improved rolling and increased coasting distance, but eventually - even with a chromoly frame hand made in USA - I feared for the longevity of my bike and went back up to 4.0. Have stayed there ever since. If the bike was designed for fat tires chances are it won't tolerate skinny ones on wide rims as well as a bike not designed to be a fatty. I have bikes with skinny tires that I love to ride. Their angles and tube lengths were designed for that type of tire.

Chances are what you want is not so much a smaller tire but a smoother one without knobs.

 

[theemartymac]

I took my Rize RX Pro down to 3.5 with Vee Chicanes. The tires are a nice size, and smooth rolling with just a hint of self steer. Hard to find many tire options in that range though.

Ahicks on this site is currently setting his identical bike up for 2.8's I believe, but had to go to 27.5 to find a setup.

Going below 3.5 would require narrower rims, which would require a full wheel rebuild. and some unique component config.

 

[AHicks]

Just to add to what Marty says above-
The 4" tires didn't work out well for my purposes. I ride mostly pavement with some grass and hard packed trail on occasion. I found the 4" tires makes for a bike that looks and feels huge, handles like a huge bike, and draggy when it comes to rolling resistance. I changed from 4" knobby tires to 4" street tires. Tires were now silent, but the 4" street tires led to a lesson in the "self steering" I had read about, which can be a little unnerving, because it happens unexpectedly. You can dial out some of the self steering with an increase in air pressure - but that leads to a loss of that great ride. Next was a change to 3" street tires. MUCH better, but they still feel draggy. Now collecting parts to install narrower 27.5"+ wheels and tires on this bike. The bike I love, the tires not so much. I consider the 4" plan, for use mostly on pavement, a mistake. An expensive mistake..... -Al

 

[harryS]

I went from cheap 4" knobbies to 3.5" Veeco Speedsters, but I mainly ride on pavement. They do have a mind of their own when turning.

 

[m@Robertson]

I took my Rize RX Pro down to 3.5 with Vee Chicanes. The tires are a nice size. Hard to find options in that range though,

Going below 3.5 would require narrower rims, which would require a full wheel rebuild. and some unique component config.

I got some nasty injuries from a set of Chicanes I took right off after the test ride. Very poor cornering traction and I found out after the fact they're known for this. Faceplanted in a slow but sharp corner.

You don't need custom rims. You can do a 3.5" tube which will ensure the sidewalls seal without issue on much smaller tires. These are 80mm rims. 2.35" Crazy Bobs IIRC. Its surprising how well they fit the rims. I have seen people do Duro Beach Bums (3.0") and they have a pretty decent sidewall.

It is VERY common to put 2.5" Maxxis Hookworms on an 80mm fatty, particularly because they lower the standover so a lot of women do it in the Sondors world. Here's one and I know the rider has had his bike set up like this for many years.

 

[m@Robertson]

They do have a mind of their own when turning.

Pump those suckers up to their max. At lower pressure they self steer like mofos. At full pressure they don't. Back down from there to see where it becomes an issue. Origin8 Supercells are the same.

 

[AHicks]

Note that smaller tires can work on the extra wide rims (80mm or so) designed for use with 4" tires, but they're going need a lot of air pressure to keep them from pinching. That extra psi requrement is going to make them ride like a roller skate.

The MUCH better plan from a rolling resistance and ride standpoint are tires in the 2.2"-2.8" range (w/rims in the 28-40mm range). These are going to offer the best of both worlds. The Schwalbe balloon types (e.g. Super Moto-X and Big Bens) run very low pressure, and are the top shelf go to's here. They work super for a hybrid on/off road tire where ride and low rolling resistance are the goals.

Noteworthy is the fact RAD sells a TON of these Rovers. A TON of them! You see them everywhere! The fact I don't care for this type tire doesn't make them wrong for everyone. My experience though, would indicate you can do much better....

 

[m@Robertson]

Note that smaller tires can work on the extra wide rims (80mm or so) designed for use with 4" tires, but they're going need a lot of air pressure to keep them from pinching. That extra psi requrement is going to make them ride like a roller skate.

The MUCH better plan from a rolling resistance and ride standpoint are tires in the 2.2"-2.8" range (w/rims in the 28-40mm range). These are going to offer the best of both worlds. The Schwalbe balloon types (e.g. Super Moto-X and Big Bens) run very low pressure, and are the top shelf go to's here. They work super for a hybrid on/off road tire where ride and low rolling resistance are the goals.

Yup. You need to go max pressure. but if you are after low rolling resistance, thats how you get it, right? I assume thats what you mean by 'rollerskate'. A tire that has no deflection in its sidewall, sorta kinda.

I run those Schwalbe balloon type tires (Super moto X in 2.40", Marathon in 2.0"). I don't know about low pressure. My Super Moto X is rated 30-65 psi range, I usually keep it at 45. My Schwalbe Pickup is 30-65 and it needs 60-65 to run right. My Marathon Plus Tour in 2.0" is 30-70 and it needs 65. I don't consider those to be 'very low pressure'. But then again: We're different, with different riding needs and this goes to my point on the fatties. Too many absolutes pronounced above when all of this is shades of grey colored by personal preference and - since this is a room full of cyclists - insufferable bias. We all have it, myself included.

BTW 2.40" is the best you are going to get out of any Schwalbe in terms of size, and the 2.40" Super Moto X with its greenguard belt is a real star in that regard for durability and protection. To go wider, up to 2.8", Vee Speedsters have done me right in 26x2.8. At that size you are finally talking about low pressures with them being 15-35. I keep mine at 30 up front and 35 in back for a cargo bike that needs sidewall support. They are on 30mm MTX39 rims.

 

[AHicks]

Yup. You need to go max pressure. but if you are after low rolling resistance, thats how you get it, right? I assume thats what you mean by 'rollerskate'. A tire that has no deflection in its sidewall, sorta kinda.

I run those Schwalbe balloon type tires (Super moto X in 2.40", Marathon in 2.0"). I don't know about low pressure. My Super Moto X is rated 30-65 psi range, I usually keep it at 45. My Schwalbe Pickup is 30-65 and it needs 60-65 to run right. My Marathon Plus Tour in 2.0" is 30-70 and it needs 65. I don't consider those to be 'very low pressure'. But then again: We're different, with different riding needs and this goes to my point on the fatties. Too many absolutes pronounced above when all of this is shades of grey colored by personal preference and - since this is a room full of cyclists - insufferable bias. We all have it, myself included.

BTW 2.40" is the best you are going to get out of any Schwalbe in terms of size, and the 2.40" Super Moto X with its greenguard belt is a real star in that regard for durability and protection. To go wider, up to 2.8", Vee Speedsters have done me right in 26x2.8. At that size you are finally talking about low pressures with them being 15-35. I keep mine at 30 up front and 35 in back for a cargo bike that needs sidewall support. They are on 30mm MTX39 rims.

For use on pavement for sure, you really should try running the balloon tires (Super Moto-X) down to 30psi. You can run that kind of pressure and get rolling resistance similar to what the Marathons running 60+psi will get as measured by miles per charge. I ran a heads up side by side test on those 2 exact tires for quite some time.

I'm over 300lbs, and the pressures I'm running in the Super Moto-X today, after a LOT of screwing around with different pressures, are 28 rear and 19 front. I'm not endorsing that for everyone, nor am I encouraging anyone to try running lower than suggested minimum. I would like to share that at those pressures, they'll go as far as the 2.00" Marathons (roller skates) did at 60 and 65psi. That's on the same bike, ridden in the same conditions, with no other changes, as measured over several charges. This is why I changed every bike in our fleet over to the Super Moto-X (5 of them!). It was not a move made on a whim. The first time the wife rode a set, she even noticed the difference in ride - and she was running 30psi front and rear at the time.

The Marathon vs. balloon type Schwalbe difference is in the construction of the tires. Kinda like comparing radial to bias belted. One side wall is designed to flex easily with no downside....

Noteworthy maybe, is the 27.5x2.8 Super Moto-X are rated 20psi minimum..... -Al

 

[ElevenAD]

I have 3in now and imo that one inch makes a huge difference in comfort, the 3in is a good all around tire but 4in is far more comfortable for my rear!

 

[AHicks]

I have 3in now and imo that one inch makes a huge difference in comfort, the 3in is a good all around tire but 4in is far more comfortable for my rear!

That's my experience as well. For use on pavement, unless you want to get into installing narrower rims, the 26x3" are a decent compromise if ride is a priority. You have to change rim sizes to do better.

 

[Mike TowpathTraveler]

I'll present another alternative: just ride on your 4.0 inch fat tire until you wear those tread blocks down. Unfortunately, most of my riding these days is constrained to bicycling locally, which means alot of road riding as off roading is out due to private property ownership.

Schwalbe Jumbo Jim 4.0 inch tires on the stock Haibike Full FatSix 80mm rims. To get the maximum mileage out of a full battery charge, I found 25 psi is a firm enough tire to get the best roll without sidewall tire deflection. The JJ's are rated to 30 psi, but on hot pavement building up tire pressures, you risk tire blowouts (been there, done that).

On a 500wh battery, with the Yamaha PW e-drive system, I can get up to 40 miles on a full charge, using High Power. I seriously doubt folks here are getting much better "mileage" than I using these fat tire off-road specific tires. If you are, chime in, I'm curious as to what kind of mileage you are knocking down on your runs.

Schwalbe Jumbo Jim 4.0. Tannus Armour. Tube. Tire pumped to 25 psi. This rear tire has over 2 thousand miles plus, on it and it's due for replacement. 25 psi means good rolling ability on asphalt. Run into off road deep sand? Just air down to 8 psi or so. Note the contact patch. Although the tire is 4 inches wide, 25 psi ensures only a portion of the tire tread is in contact with the roadway. Air down and that contact patch size increases. Right here in this pic is proof that the fat tired ebike, properly set up, provides the best alternative of the greatest stability, ride feel, mileage per battery charge and overall rider comfort than any other bicycle or ebike on the road.

 

[AHicks]

The only issue (other than noise due to a knobby tread pattern) with running a 4" tire at 25psi is going to be the ride. To some, where that's not a big priority, agreed, 4" will work out fine when it comes to rolling resistance.