Part 1: Brake Issue on Ultra Stumpy Solved!
I picked up Ultra Stumpy from the bike shop today. The horrendously dangerous Formula "The One"brakes that came on Ultra Stumpy are long gone. A much more predictable set of brakes, Shimano XTs, are now resting comfortably on Ultra Stumpy. The bike now is docile and predictable in braking performance. Ultra Stumpy is a sweet ride!
Ultra Stumpy is a Specialized Stumpjumper FSR Carbon Expert. The original brakes were made in Italy by Formula.
The service manager at the bike shop explained the problem. Formula bike brakes use DOT 5.1 brake fluid, which is a polyethylene glycol-based fluid and is designed to be hygroscopic. The translation is that Formula is using an automotive brake fluid that is formulated to absorb water. The ability for an automotive brake fluid to absorb water is advantageous because water in an automotive brake system is corrosive. As the DOT 5.1 brake fluid absorbs water two things happen: (1) the brake fluid expands, and (2) the boiling point of the brake fluid drops. An automobile has a large amount of free space in the master cylinder that allows the brake fluid to expand, and thus prevents a build-up of pressure at the wheel cylinders.
Are you still with me?
Not to put too fine a point on this, bicycle braking systems ain't the same as automobile braking systems. There is darn little space in hydraulic bicycle braking system for over-expansion of the brake fluid. It is a mystery to me why a bike maker would use automotive brake fluid in bike brakes.
The bike shop found that Ultra Stumpy's brake fluid was contaminated with water!
As the brakes heated during normal use, the contaminated brake fluid over-expanded causing the front brake to start dragging. The dragging caused the brakes to get very hot. The hot brake fluid had expanded until the slightest application of the brakes caused the front wheel to lock-up!
The front brake was a time-bomb!
When the front brake locked-up, my very expensive finely balanced mountain bike did what it was designed to do. Ultra Stumpy instantly responded and, thereby, became a death trap! Some less expensive bikes would have just skid when the front brake locked-up. Not Ultra Stumpy. Ultra Stumpy flipped forward, and in less than an eye-blink, hammered me into the ground!
The new Shimano XT brakes use traditional mineral oil as brake fluid, which does not absorb water and has an very high boiling point of 310°C (590°F). By comparison, the water contaminated DOT 5.1 brake fluid has a boiling point of 190 °C (374 °F). Mineral oil is dimensionally stable and is easier on moving parts than DOT 5.1 fluid. Cave paintings in France show hydraulic bike brakes being filled with mineral oil. Mineral oil is low tech perhaps. But it has worked in bike brakes since the dawn of time.
At no cost to me, the bike shop replaced the Formula Brakes with the tried-and-true Shimano mineral oil XT brakes.
They put on new rotors to match the XT brakes. I gave this new combination the acid test. The XT brakes are powerful, smooth and predictable. I think I am going to like these new brake a lot.
The service manager told me that he now knew how to get the Formula brakes working properly. I really wanted nothing to do with brakes that had hurt me twice! He got that.
Part 2: I Have a Fast Bike and a Smooth Bike - I want a Quick Bike
Alas, my trusty little hardtail, Little Stumpy, just doesn't cut the mustard anymore. Little Stumpy is a 2006 Stumpjumper Pro that was intended for sale in Great Britain. Somehow Little Stumpy ended up in the United States. Little Stumpy is a fiercely fast bike on a smooth single track or double track. Unfortunately, Little Stumpy is a handful on rough and/or rocky trails. In Colorado we have a lot of rough and rocky terrain.
I think I have become spoiled by the full suspension on Ultra Stumpy. During an ascent on a rocky trail, Ultra Stumpy's rear suspension keeps the rear tire in contact with the ground. The hardtail "suspension" on Little Stumpy tends to bounce off the trail. The result is loss of pedaling efficiency and some squirrely handling. Bikes are not airplanes and have cannot go around corners while airborne. On rough terrain Little Stumpy can get skittish in corners.
Little Stumpy does have a big advantage in that he is a very compact bike with 26" wheels. Baby Stumps can turn on a dime and give you 9 cents change! As long as he is in contact with the ground, he is extremely nimble! Little Stumpy is also very easy to jump and pump. Pumping over rolling terrain is a "free" way to get extra speed. Basically, you rise on the front side of a bump to get "light". You sink on the backside of the bump to get "heavy". You gain more speed on the backside than you lose on the frontside.
You may be able to see in this photo that Little Stumpy has a very short chainstay and a steep head tube angle. A big head tube angle is called "tight" steering.
Here is a diagram that shows some of the geometry of a bike. Little Stumpy's short wheelbase and a steep head tube angle equates to lightning-quick handling but less stability. Ultra Stumpy's longer wheelbase and less-steep (i.e. slack) head tube angle makes Ultra Stumpy quite stable on rough terrain but slower handling.
Touring road bikes tend to be stretched-out with slack steering making touring bikes very stable. My Allez sport road bike has a short wheelbase and tight steering giving my road bike amazing handling at the expense of stability.
My Specialized Allez is fun, fast and responsive. Compared to trail riding, street riding is silky smooth. This bike pedals smoothly, shifts smoothly and rides smoothly.
Part 3: Shopping for Quick Bike
I started thinking that there may be a full suspension bike out there that combines a full suspension with the lightning quick handling of a hardtail. Don't get me wrong. Ultra Stumpy is a great handling bike. But he has 29" wheels, which requires a longer wheelbase. Ultra Stumpy has a noticeably wider turning radius than Little Stumpy. Ultra Stumpy also has slack steering to improve stability in extreme conditions. The long wheelbase and "slow" steering requires greater body and bike separation in tight corners. Body and bike separation simply means you lean the bike at a steeper angle than your body. You also point your body where you want the bike to go.
I poured over bike specifications trying to decide what I wanted. I am what is known as a techno-nerd, which is another name for engineer. I also know that specifications don't tell the whole story. A bike is more than just the sum of it's parts.
I was pretty sure that I wanted a 26" full-suspension bike with 100mm to 130mm (4" to 5") of suspension travel. I test rode a number of bikes. Ideally, I wanted to keep the purchase price under $1,500.
Option 1: Scott Genius 40 (26" Wheels)
The Scott Genius 40 has a head tube angle of 68.5 degrees and a 1117mm (44") wheelbase. The suspension has two travel settings of 120mm and 150mm that are selectable by flipping switch on the handlebar. MSRP for this bike is $3099. Green Mountain Cyclery was asking $2,750 for a new Genius 40.
During the test ride, I found the Scott Genius to be pretty responsive and had a lot of nice features including a Fox 32 front fork. The bike had nice manners but was not what I wanted. The price was also an issue.
Option 2: Giant Yukon 26er
On the other end of the price spectrum was the Giant Yukon. I found this bike for sale at Campus Cycles for $929. A full suspension bike for under $1,000 from a reputable manufacture is hard to find.
The Giant Yukon has a head tube angle of 70.5 degrees (the bigger the number - the steeper the steering). The Yukon's wheel base is 42.9". This bike had steeper steering and a shorter wheelbase than the Scott. The Yukon had mechanical brakes and a low-end 100mm Suntour coil spring fork. The bike had 24-speeds and SRAM shifters. Not bad for $930.
Then I rode the Yukon. This bike is well behaved and very easy to ride. The riding position was more upright than I like. The bike struck me as docile. Surprisingly, this bike was slow to respond to rider input. The Yukon is a beginner's mountain bike and it felt dead. I could not get it back to the shop quick enough. If someone is looking for a docile full suspension mountain bike for a modest amount, this is it! Ultra Stumpy and Little Stumpy could run circles around this bike.
Option 3: Giant Trance X4 26er
I test rode the Giant Trance X4, which is a few notches above the Yukon.
The Trance has a 69.5 degree head tube angle and a 43.5 inch wheel base. The riding position is the traditional "forward lean" that I like. The brakes were Avid Elixir hydraulics that worked well. Suspension travel is 120mm. The fork was a coil spring RockShox XC 32. This bike felt a million times better than the Yukon, but still did not have the quick response I wanted. The bike was on sale for $1,350 so it was in my price range. I think this bike had a good frame and great geometry that was not served well by the inexpensive fork and rear shock. The next step up was the Trance X3 but the X3 is priced over $2,000.
I gave up on Giant.
Option 4: 26" Trek Fuel EX 5
The Trek Fuel EX 5 had the right stuff. Head tube angle is 68 degrees. The Wheelbase 1134mm (44.6"). The EX5 had an excellent suspension consisting of RockShox Recon air fork and RockShox Ario RL rear shock, which are really good components.
This bike is pretty. This bike was nimble and quick. Riding position was great and the SRAM X5 components were nice.
The problem with the Trek Fuel EX 5 was the price. Wheatridge Cyclery had the Trek for $1,869.99. Although, this price was close to my budget and was a great bike, I kept looking.
Option 5: Specialized Camber Comp 26
I have to admit I like Specialized bikes. I have bought a seven bikes since moving back to Colorado including: 2004 Giant Boulder SE , 2006 Women's Giant Boulder SE, 2006 Specialized Hardrock Sport, 2006 Specialized Stumpjumper Pro HT, 2008 Specialized Women' Myka Comp, 2012 Specialized Stumpjumper FSR Carbon Expert 29er and a 2012 Specialized Allez Comp Apex Mid-Compact. (2 Giants and 5 Specialized)
I looked a at 2012 Specialized Camber Comp 26. The Camber has a 69 degree head tube angle and 1118mm (44") wheelbase.
I am not really fond of the white seat and white handgrips but that can be changed. This bike came with high-quality downhill pedals! I took the bike for a spin. Oh my! This bike put the the Scott, Trek and Giants to shame! This little Camber had the lightning quick handling of Little Stumpy and a full suspension to boot!
In short, the bike was amazing! The Camber Comp lists for $1,850. Wheatridge had in on sale for $1,650. I talked then down to $1,450! The bike was mine! I put it on lay-a-way. I paid-off the Camber on Friday when I got Ultra Stumpy back.
I have already sold my 2004 Giant Boulder SE, called "Big Red". The Hardrock and Little Stumpy are for sale.
Part 4: Quick Ride on a Quick Bike
I took the Camber to Pine Valley Ranch Park for a shake-down ride. Pine Valley Ranch Park is at the extreme North end of the "Epic" Buffalo Creek Bike trail complex.
I took Narrow Gauge Trail to Buck Gulch Trail. I took Buck Gulch Trail to Skipper then looped back on Strawberry Jack to Pine Valley Ranch.
Here is a side view of my Camber on the trail. I think this photo shows the steep steering angle and short wheelbase. This little bike dances down the trail. The reflectors have got to go. IMHO, a reflector on a mountain bike looks like a satellite dish on an outhouse!
This is a view down Narrow Gauge Trail. The trail has some nice rollers. The only issue is the trail is mostly decomposed Granite, which are like ball bearings. If you are a mountain biker, and this fast single track doesn't get your blood pumping, nothing will!
Pine Valley Ranch Park is popular. The South Platte River runs nearby and attracts kayakers.
During my ride, a close encounter with a willow bush took off the rear reflector. I picked up the broken reflector and put it in my pocket. Just doing my part to keep the trails neat and clean. I think the "CAMBER" graphic on the seat post looks good.
Part 5: The Verdict
I rode 6 miles in 27.54 minutes. Maximum grade was 41%. Average speed was 13.1 mph. Maximum speed was 27.9 mph. Maneuverability is fantastic. The Camber is quick, not fast, but quick. The bike handles rough terrain with ease. Getting the bike in the air to clear obstacles is child's play. The Tektro Draco hydraulic disc brakes work flawlessly. The stock flat downhill pedals are kind of fun. I bought a new set of Shimano clipless pedals I will install later.
What are the downsides? The stock saddle is tolerable but not very comfortable. The white hand grips have to go. These white grips looked dirty after about 2 minutes of riding. The only mechanical weakness is the crank. The chain rings are stamped steel and do not allow smooth shifting between between the rings. Surprisingly, the Shimano Alivio shifters and the Shimano SLX rear derailleur work really well.
I can get a great crank for $130 to $200 but I can live with the low-end crank for a while.
I like this bike. Thanks for reading my blog.