FlexFit by John Karrasch

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Homewood, AL
FlexFit by John Karrasch

Not your basic bike fit. I provide professional bike fitting services at Cahaba Cycles for all disciplines for cycling.

This includes road, MTB, cyclocross, and triathlon/TT positioning for improved comfort, power, and performance. I bring a unique combination of skills to the fit clinic with experience as a racer, therapist, and mechanic. I am up to date on the most current Trek Precision Fit training. My approach to fit is based on a true understanding of the rider's individual biomechanics and goals. I do my own research and bring a wholistic method to a field increasingly filled with data. Numbers are important, but at the end of the day a good fitter is not dependent on any specific tool or technology. I assess movement, on and off the bike, to deliver a great fit for everyone from recreational riders to National Champions.

09/08/2026

Fit of the day - Jamie’s new Crux 5 with the new Terra Aero CLX hoops, Force XPLR bits, and new Terra cockpit. 45 to 55 tire swap soon, too. 🫡

As advertised, essentially a Tarmac with clearance for 2.2 tires. Love to see it… and ride it a bit myself.

Enjoy it, Jamie!

09/01/2026

Hutchinson Touareg Race 700 x 50 off road rolling resistance results 📊

Released in Spring 2026, the Touareg Race shows an evolution of other Hutchinson Cycling tires to produce a k**bbier counterpart to the ultra fast Caracal Race. The tread pattern isn’t new, stemming from the regular Touareg and before that, the mixed use Overide tire. The Touareg Race shares the same Mach Tread 3.0 compound and Swift Easy casing as the Caracal Race. Per Hutchinson, the Touareg Race “was designed to meet the demands of elite racing. It integrates the world-class technology of the Caracal Race into the versatile Touareg tread pattern. This is the tyre for riders who demand surgical precision and maximum efficiency without sacrificing the grip that made the original Touareg a legend.”

The construction is very similar to the Caracal Race, despite these being a black sidewall versus the brown sidewall on all the Caracal Race models I have used. The Touareg Race 50 was actually 10-15 grams lighter (620 grams) than the Caracal Race 50 I tested. Both had a 1.00 mm thick sidewall, 139 mm flat bead to bead width, and inflated width of 53 mm on a 25 mm internal rim. These have a fairly rounded profile, giving the option of easy (and perhaps preferable) use on a rim wider than 25 mm. Mine still looked good on a 32 mm internal rim and would work with even wider ones if desired.

I had no issues riding these or keeping air in them. Those looking for more traction than the semi slick Caracal Race will be happy here for sure, as they retain an impressive amount of the Caracals Race speed! Given the small k**b size, the Touareg Race is super quiet on pavement. These only give up a watt or so rolling resistance for a pair of tires on the road compared to the CR50, and about two watts for a pair of tires on both gravel surfaces tested. These margins are guaranteed to be missed with old school rolldown tests and exactly why I test via Chung Method / VE protocol. Fast setups don’t just happen…they are the result of many smaller decisions and having some clear data helps.

PSI notes in the comments.

08/21/2026

Silca Protocol RCG-1 700 x 55 off road rolling resistance results 📊

…yes, the Unlisted tire.

Per SILCA , “When speed off road is the goal, Protocol RCG-1 is the go to option. The first ever gravel tire that was developed around modern sizes first. RCG-1 is the fastest option available for the biggest races.” RCG stands for Race Casing Gravel.

I’ve been testing prototypes of this tire for months, as indicated by the tire in my photos, but other than the label this particular tire is THE Protocol RCG-1 production version released today. Generally, I would refuse the initial prototype phases and wait for the final ones, but agreed to all of it as they were kinda what I wanted to see exist but didn’t yet.

Claimed weight for these is 535 grams, I think mine were a few over that but close. Light. They aired up easily and are exactly 55 mm wide on a 25 mm internal width rim. Silca suggests their own sealant but I used Orange Seal per usual with an identical amount used in other 700 x 55 tires I have tested for absolute consistency in my own testing.

These have what is called a Pulsar compound for absolute speed and GhostShield protection (vs SealSkin on the RCG3 and RCG4) with a Race casing. They also have a 120 tpi casing, going to show again, tires are more than their individual specs, as plenty of high thread count tires aren’t fast.

The results are quite clear here.

Fast. Insane fast.

I tested them back to back each surface with previously tested 700 x 55 RS Pros from Schwalbe, my current control tire set. It’s always nice to have absolute certainty, as well as some subjective impressions on a new tire.

Silca suggests running 1-2 psi higher than other similar gravel tires, which I can back up as I realized it on my own based on ride feel. Further psi notes in comments.

All outdoor results are my own via Chung/VE testing through GitHub Virtual Elevation Analyzer. Thanks Hannes. 🤝

08/12/2026

Hutchinson Caracal Race 700 x 50 off road rolling resistance results 📊

(These are the first test results on my Manzanita Cycles. Thanks to Nick for making a killer bike. 🤝)

Per Hutchinson Cycling , the Caracal Race is “engineered for elite racing and high-speed gravel riding. Crafted with cutting-edge technology and precision, including Hutchinson’s innovative SwiftEasy casing and Mach Tread 3.0 compound, borrowed from the development of our new road racing tyre. The Caracal Race delivers unmatched agility and performance. Experience the thrill of speed with the Caracal Race – redefine your gravel riding experience today.”

The road tire referenced is the Blackbird, available in sizes up to 700 x 34. The Caracal Race originated in a 40 mm width (March 2025 test) and was followed by a 45 mm (September 2025 test) which both produced incredibly fast test results along with a luxurious ride feel. For those looking to add a puncture protection layer, a GridSkin model is also available.

My tan wall set of CR50s weighed an average of 630 grams, with a 1.00 mm thick sidewall. For context, that is similar to Schwalbe’s Super Race tan wall casing. Flat bead to bead width is 139 mm, giving an actual width of 53 mm on a 25 mm internal width Reserve rim. All sizes of the Caracal Race blow up about 2 mm wider on a 25 mm rim. The 45 and 50 have fairly rounded profile, so lend themselves to use on wider rims if that’s your thing.

I had no issues with these tires, and quite liked them. The ride feel is one of the smoothest out there and they roll incredibly fast… tying the 60 mm G One Speed Pro with a 0.0036 CRR value on smooth pavement. The 45 is a bit faster on Cat 1 Gravel, while the 50 is clearly faster rolling on Cat 2 gravel. Generally speaking, Hutchinson’s speed claims hold up across the Caracal Race size range, with different test surfaces showing clear volume benefits as the ground gets rougher (and softer).

All outdoor test results are my own via Chung Method / Virtual Elevation testing. PSI notes in comments.

08/08/2026

My new Allied Echo. So clean. So fast. So pretty.

I wouldn’t say the book is exactly closed on what a road bike should or shouldn’t be… or what size tires are best on pavement. Not all paved roads are the same, ya know?

Testing aside, the bike is good so far. REAL good. That means different things for different folks but I will elaborate on that soon.

Specs:

54 CM ALLIED CYCLE WORKS Echo in Supra White - I’m 5’9” / 175 CM tall. 73.5 CM seat height

SRAM Road Rival AXS XPLR group. 46 ring, 10-46 cassette, and 170 mm cranks

SILCA hot wax on the chain

Reserve Wheels GR 40/44 wheels - 27 mm internal width

Continental Bicycle Tires GP5000 S TR tires - 700 x 35 but puffed up to 38.5 mm actual on the Reserves. Tubeless with Orange Seal Regular

110 mm Allied 2 piece stem with 36 cm FSA bars. Allied post with a creaky Specialized Power saddle

Arundel Bike Company bar tape and Mandible cages

I’m hyped. More to come. 🤝

08/06/2026

Always sweatin’ the details 🫡

Full gas into the second half of the season. Link in bio for absolute certainty your fit is the best it can be.

08/04/2026

One of my current methods for roughly setting initial bike fit on my own bikes. This gets MY fore aft seat position close (110 mm index to 80 mm saddle point plus 65 mm actual setback from to nose from BB). This is effective a 74.5° seat tube angle.

Bikes roll, so finding level “enough” ground isn’t too hard either.

Your fit may differ but the same idea applies… having perfect tools and all the time in the world is nice, but having a quick version that gets it super close is good enough. Which is often pretty good. 😊

Oh yeah, I have a Supra White ALLIED CYCLE WORKS Echo so I’m gonna have some things to say about that soon. 👀

07/29/2026

Vittoria Terreno XC Race 29 x 2.25 off road rolling resistance results 📊

As I mentioned in last year’s test of the 2.4 Terreno XC Race, these new models (avialabel in brown or black sidewalls) are a major update from the prior generation Terreno XCR (tan wall I also tested last year). Vittoria says, “The new XC Race construction delivers the numbers: 20% more speed, 8% more grip, 44% better puncture resistance, and 9% improved riding comfort.”

The 2.25 shares it’s construction with the rest of the XC Race lineup, with a 60 TPI casing and Graphene + Silica Race Formulation compound. These measured in at an average of 658 grams and inflated to 56.5 mm on a 25 mm internal rim. Sidewall thickness is similar to the black sidewall XC Race tire at 0.8 mm. I had no issues inflating these and they were easy to deal with day to day for all riding and testing. These 2.25 Terrenos are the tires ridden to victory by Haley Smith at this years The Rift Gravel event, notorious for the demands it places on a a rider’s equipment!

Results wise, these are a big step up from the prior gen Terreno and show consistenly very fast results across all test surfaces. For a tire with minimal tread, these again proved to overperform their looks with impressive traction as long as you aren’t in slimy mud. I haven’t seen any performance variation related to the sidewall color within this Vittoria range, for anyone curious. Technically, these are an MTB tire, but worth a look for anyone with a gravel bike that will clear them!

Other 2.2s and 2.25s are similar speed to these, with the Terreno XC Race also serving up nice ride feel on pavement as a bonus. As we all know, numbers and lists are cool, but your bike should ride how you want it to ride! As much as I liked these, I have to end with a request for Vittoria…how ‘bout these in a 32 inch version? All results my own via Chung/VE outdoor testing, PSI notes in the comments. ✅

07/27/2026

Testing 700c v 32” gravel bikes with Ben Delaney… full results available on YouTube now:

https://youtu.be/mTEtR_1jUHM?is=kQZa5UnJCrsBH4v-

07/17/2026

Real world MTB wheel testing - Berd HAWK30 Gold Carbon wheels vs Nextie Alpha Unicorn/DT 240/DT Comp steel baseline. 📊

As Berd Spokes says, “With two Olympic Gold Medals, two Olympic Bronze Medals, and over 50 XC World Cup podiums in the last 2 seasons, Berd spokes are the winningest XC MTB spokes in the world. Lightweight, strong, vibration damping.” Their racing pedigree is obviously there, and many riders report improved comfort…but I still had some lingering curiousity over whether any outright efficiency differences existed with the Berd spokes. I tested the 32” version, but a 29” is also available. For a deeper tech dive on Berd spokes, check the work by Dave Rome - Escape Collective a few months ago.

My baseline wheels used here are 32” Nextie Alpha Unicorn carbon rims (30mm internal) laced to DT 240 hubs with DT Comp butted steel spokes and Prolock nips by Mike Curiak. They weigh 1540 grams vs the Berds at 1196 grams. Due to the way Chung Method testing is done, weight is neutralized in terms of rolling resistance and aero results. I tested both wheelsets with 32 x 2.4 Maxxis Aspens of similar mileage and weight. I used Orange Seal sealant in both sets, and kept identical psi for tests (24 on pavement and 15 off road) to keep things as similar as possible. I first tested on smooth pavement to isolate any aero differences between wheelsets then moved onto rough singletrack testing to see if any rolling efficiencies appeared off road.

As the results show, the Berd wheelset had the same aero and rolling test values on smooth pavement BUT showed a measurable benefit on rough terrain vs the baseline wheelset with DT Comp steel spokes. The off road values were .0226 CRR for the Berd set and .0232 CRR (coefficient rolling resistance) for the Nextie/DT set, which in more everyday terms works out to 5 watts of pure rolling efficiency savings with the Berd wheelset at 30kph or 4 watts at 25kph. Again, this doesn’t factor weight in, which has obvious benefits when the trail goes up! From a ride feel perspective, the Berd hoops have a smoother ride and seem to almost articulate to the trail better. I like ‘em.

Address

1724 27th Court S
Homewood, AL
35209

Telephone

+12054279869

Website

http://johnkarrasch.com/

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