Gravel and mtb tires…what is fastest and why?

For now, I am keeping this spot as the central hub for the tire and aero testing I am doing. It is mostly focused on gravel and MTB setups but I am also working on road / TT oriented bike setups.

The gravel scene in the US (I feel like a moron saying that but hang with me for a minute please…) has lots of folks thinking about their tire choices thanks to numerous pros in the Lifetime GP series very obviously maxing out their tire clearance…and doing quite well with it.

Bottom line here is, I want to have some well defined data (spoiler: I have some of it) for what makes tires fast or not so fast off road …while also addressing the rather obvious aerodynamic or weight factors included in the tire change decision process!

I have been posting most of it on my Instagram as I like it and it is good practice to make it easy to understand with limited content. That is a major goal. The posts blend in some with my other content there, so here they are in one place…

Power to hold 15 mph on Medium Rough Gravel.

So…what does a test day look like with this?

The Delta Tells The Tale!

CRR varies by surface.

Whatabout really fast and smooth gravel?

It sounds like too much. I get it. Why go so deep into it?

How many folks tell you this stuff like,  “I switched to X and got a Strava PR after using Y the time before that!” We all know how to be nice but we all know we got a story there. Of course, there is more basic testing that is better than a straight up story. Usually riding a set course at a set wattage and comparing times. This is fine, and it beats Strava story time, but I have done plenty of that and wanted more defined answers!

I’ve done all kinds of testing over the last 15 years, but my current methods are mainly focused on the Chung Method. If you really want to understand how bikes go fast or slow, the pdf in the link is free to read. Robert has been incredible helpful to me on this project so I cannot thank him enough. For anyone halfway into the pdf… the testing is simple in format but NOT easy to pull off well! This YouTube video from Silca (Aero testing expert explains how to get accurate aero testing at home) has a fantastic interview with Robert Chung reviewing some testing files before the 2024 Unbound 200.

Golden Cheetah’s Aerolab.

This gives the data, when done well, of an actual CRR (coefficient of rolling resistance) and CdA (coefficient of aero drag) which then can play out ALL kinds of riding scenarios, whether on or off road! This means instead of isolated “faster or slower” testing days we have a data set that can be used to model ALL KINDS of “whatabout” riding scenarios…

The Data and the Data Collection Site

For off road tire testing, we of course have the Bicycle Rolling Resistance website, which I pay the small fee for a membership even though much of it is free. I like it. Some think it tells ya everything about what tires are always fastest off road and some think it is dumb because “conditions are always changing”.

Both camps are wrong. THAT is why I am doing this. 

After being without a gravel bike for a couple months, I spent lots of time on my MTB with a rigid fork out riding. I was really surprised how fast the bike was everywhere… even on fairly flat and easy gravel tracks, so of course, like any decent cyclist, I headed to Strava! Fortunately, I didn’t stop there! 

I wanted to know what the actual rolling resistance of these tires was off road, so….I did it. I am still doing it actually. I probably will be doing it for years. The progress is awesome so far. I am not alone here, the others doing this are small in number but are super helpful so that is encouraging. 

I started this project with the goal of taking folks out to field test THEIR setup…. how fast is your setup, for real? That is still happening, and it’s cool, and it works. I realized there was another layer so I kept pushing on the off road testing. 

Some fast tires on drum testing remain fast off road and some less so. General trends are pretty clear and some of the wild bike setups from the Lifetime Grand Prix (for real though… what is Dylan Johnson so excited about?) will make more sense soon. 

FAQ:

What about tire psi?

It does matter, that is for sure. I am usually testing off road with the rider’s preferred pressure, which also ends up usually VERY close to what the Silca or Wolf Tooth calculators would serve up as a suggestion. The goal is to get a “best case” for each tire, which is fairly easy.

Aren’t wider tires less aero?

Absolutely. The Swiss Side link below in the Resources section goes over this. There seems to be much more possible variation in CRR wattage than aero wattage swapping between different tires.

RESOURCES:

Reliability of the virtual elevation method to evaluate rolling resistance of different mountain bike cross-country tyres

Torsten Franks blog

Impact of Wheel Size on Energy Expenditure during Mountain Bike Trail Riding

More Speed, Less Power Offroad Tire Testing

Swiss Side Gravel Tire Width Aero Impact

Influence of wheel rim width on rolling resistance and off-road speed in cross-country mountain biking

Evaluation of aerodynamic and rolling resistances in mountain-bike field conditions. Journal of Sports Sciences

Tyre Volume and Pressure Effects on Impact Attenuation during Mountain Bike Riding

If you have questions, feedback, or want to compare notes just leave a comment below or email me at johnkarrasch@gmail.com

Testing Grounds

Wild card custom mtb build

Believe it or not, this bike started as a parts bin bike!

I had a too good to refuse type deal on a Santa Cruz Chameleon frame, so started collecting parts while I waited for it to arrive. My other mountain bike is an OLD Vassago Jabberwocky singlespeed, which I knew wouldn’t last forever so I wanted another in the mix. A few weeks went by and things ended up not working out with the Chameleon frame, leaving me with a pile of parts and no frame. Oops.

During this time I had worked with Jay Sandefur of Wild Card Bicycles in Opelika, AL on a singlespeed hardtail for one of my bike fit customers. The bike came in and was built up, so I made sure to take it for a ride after I checked the fit measurements. Well, hello… it rode nice enough I emailed Jay to put me on the list for a frame. Jay’s frames are custom as custom gets so I sent Jay some must haves and trusted him on the geometry. 

My goal for this bike was a bike well suited for big, climby, technical rides. This means something enjoyable to climb AND descend with. Given our twisty singletrack around here, I also wanted something fun for weaving through the trees. I ended up going kind of wild on the parts, but I also have the intention of this being a bike I keep a LONG time! Everything, and I mean everything, was carefully picked. 

I ended up building most of the bike with Jay at his shop in Opelika, which was honestly a dream come true for a long time bike geek like myself. The bike is as fun as it looks! I will leave you with a parts list and some more photos to check out below…

▪️Wild Card custom frame. Dedacciai double butted steel tubing with Paragon Machine Works sliding dropouts for geared or SS use. Two bottle mounts and full internal routing for rear brake and dropper post. Straight 44 millimeter head tube and 73 millimeter T47 bottom bracket shell. Paragon combo titanium slider hardware and Paragon bolt on thru axles. The paint color is called Lipstick.

▪️Fox F34 130 mm 29er fork 

▪️Cane Creek 110 headset and Hellbender 70 bottom bracket 

▪️SRAM XX1 175mm crank with Quarq power meter. Pedals are plain old Shimano 540s. 

▪️Singlespeed setup with 34 tooth Wolftooth ring and 21 tooth Boone Technologies titanium cog

▪️KMC X11 chain stripped and waxed with Silca hot melt. 

▪️Bontrager Kovee RSL wheels with Maxxis Rekon and Rekon Race 29 x 2.4 tires. Orange Seal Endurance formula and Reserve Fillmore tubeless valves. Both tires are Maxxis WideTrail designation to jive well with wide rims. 

▪️XT 2 piston brakes with 180 mm centerlock XT rotors and metal pads

▪️Fox Transfer dropper post with WTB Volt saddle with ti rails and Wolf Tooth post clamp 

▪️Paul Comp Boxcar stem with Santa Cruz flat bar cut to 730 mm and ESI grips. Bars and stem are 31.8 mm clamp diameter

▪️Weight is 23-24 pounds and the ride and handling are really great! It’s fun on downhill but still capable on steep climbs and switchbacks without feeling like a boat. 

To better describe it…think of an Epic Evo or Blur TR in hardtail form. 

It’s fine: A collection of short stories about rick karrasch.

September 19, 2022.

What a weird day. My dad Rick Karrasch passed pretty suddenly this morning out in Oregon. He felt weird, so my sis and stepmom took him to the hospital.

He made some jokes about the imaging machine with hospital staff and not long after, his heart stopped. He went out like many aspire to, quick and without suffering.

Dad was never an advocate of perfect health and by this point, I think he has had some deal with neighborhood cats to borrow lives, as he has been well past his personal nine for YEARS!

I wear my feelings on my sleeve as many know, so I’m obviously pretty damn sad. Just the way it is. Never had a poker face and never will.

Anyway.

I left work early, ate one piece of cold pizza and rode a few hours. Straight to bonk city. Didn’t bring enough water either. I did get a good picture of a 2nd Gen Dodge Caravan. He wasn’t one to overly plan things and I think would have appreciated all of it. Seemed right. Felt good.

I’ll throw in one of my favorite Rick stories as he loved telling stories haha.

He passed his Ford Ranger to me when I turned 16. It was a 93 Extra cab with a 5 speed MT and the 4.0 V6.

Like most 16 year old kids I was an absolute moron so took it deep into Talladega National Forest the first chance I got. I wrecked it and wrecked it good. Caved in the whole side of the bed. I had to walk hours to get someone to rescue me and the truck.

I played it cool when I got home and parked it with the wrecked side facing the fence where Dad couldn’t see it. Genius.

I parked it like that for 2 years then sold it. He never said anything so finally in college I asked him about it.

“Oh yeah, I saw it the day you brought it back, but figured it was your problem to figure out..”

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Top of Dunavant Mountain. 1989.

This is on Highway 25, that runs from Leeds to Vandiver. We grew up on the Vandiver side and it is one of my favorite roads of all time.

I was 4 years old and neither my Dad or I had any perception of his Nissan being a “paw paw truck” at the time.

Probably cause back then, most trucks were paw paw trucks!

This truck was my Dad’s and had all the requisite attributes of the genre:

Mostly stock

Camper shell

Extra cab

V6 with the 5 speed manual

I remember the jump seats in back well and so does my sister. They directly faced each other, and during drives to Missouri to visit family, the tension started high and got worse.

Dad obviously wanted me and Evangeline to stay close during these trips. We are still close to this day, and I’m proud to say haven’t kicked each other in years.

I suppose I always had an awareness of paw paw trucks, so my uncanny ability to find them was probably set in place as a youngster and I owe some thanks to Dad.

“People like hearing stories about other people.”

-Dan John

I found this poster in our office early this week. From the date on it, I think it is from Dad’s first year in Purdue’s marching band.

He was a trumpet player, and obviously a good one. Band stuff was him and Evangeline’s thing when we were kids. I always played sports, so it was just kinda understood we had our own things. (Evangeline says she was also a majorette which is a sport but I didn’t see it at the World Games so whatever)

She played clarinet, and he always helped her practice. He took me to my games and bike races. Simple enough.

Dad had a Masters in Political Science from Purdue. He ended up a car mechanic after college and was pretty good at it.

I know he sometimes seemed sour about not doing something more directly involved with his college education, but I was more interested in how he spent that time there and wasn’t into college basketball…

—————

Dad had relatively simple tastes in food, and never missed an opportunity to grab a treat for me and Evangeline.

In general, we ate healthy and had a giant garden shared with neighbors when we were little.

But yeah, I would say Dad exposed us to plenty of foods Mom might have missed 😂. Chili cheese dogs, Mountain Dew, and a large variety of candy.

I still remember the standoffs between him and Evangeline when he plopped down a SPAM sandwich in front of her!

I never quite nailed down Dad’s own food preferences however. My mother was and is a fantastic cook, and she also had a tough time impressing dad with meals.

I knew Dad liked room temperature, maybe warm, Folgers instant coffee. I also liked coffee, so decided once to make him my favorite coffee. I don’t remember what it was, but I made sure to grind it fresh and run it through the Aeropress.

He took one sip, set it down, and turned back to The Weather Channel. I was furious! He told me something like “oh it’s ok I guess” and that was that. Lesson learned.

I told my Mom about it and she had her own version from when they first got married.

He said he liked meatloaf, so she set out to make a great one. Like I said above, she was an awesome cook. He wasn’t impressed with the first few attempts…

“I don’t know, it just isn’t as good as my Mom’s” 😂

After a couple more tries, she was OVER IT.

She went to the store, got the cheapest ground chuck she could find, some French’s meatloaf mix, and ketchup.

Dad took one bite, his face lit up, and he said ,”Oh Linda, you finally got it right!!”

Dad was an absolute character and well remembered, which is all any of us can hope for when we are gone!

——————

Some vehicles don’t belong on dirt roads, and this was one of them.

This is The Queen Mary, Dad’s first Chevy Caprice station wagon. One of two, or maybe threes he had. I am not sure.

He really liked station wagons. So much in fact, that he got his first wife (my mom Linda) a Grand Marquis wagon once without talking to her first. Wood panels and all. I’ll let you guess how that went over.

This particular wagon here is the one he got us lost in Talladega National Forest driving. He was taking me to a mountain bike race at Cheaha and I had already been there a hundred times.

He pulled out a crumpled page of Mapquest directions and declared we would try a new way. I just told him alright, hand them to me and let’s go. I would read and he drove.

It only took a couple turn offs from pavement and we were in full gravel mode in the Caprice. No cell service. No map. For what it’s worth, a Caprice wagon is really bad with tight turns on loose gravel. It’s probably fun driving, but whoever isn’t driving will be scared as all hell. I was.

We had gone from being 90 minutes early to the race, to pretty close to being late to start. Eventually we popped out on pavement again, and made it up to the top of Cheaha.

I grabbed my stuff, begged the promoter for a plate and promised to pay when I finished. He laughed and let me race. Dad smoked his pipe in his camp chair like nothing had happened at all then drove me back down the mountain after the race.

This was the same day I got motion sickness for the only time in my life. I raced in the heat for two hours, then layed in the backseat of the wagon while he drove it down the twisty mountain.

Dad was super into cars, and that was probably my favorite thing to talk about with him…even if it was fighting over the best time of year for me to prep the entire wagon to paint by myself*.

The photo here is from a trip that went through Bryson City, North Carolina in the early 2000s. Dad was always happy to kick it in the parking lot for a few hours while I got a ride in.

*it’s never the right time of year to prep a Caprice for paint by yourself*

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