BNB

I have read several older post about using an ENVE fork on tandems and would appreciate any feedback on my situation. ENVE still does not recommend their forks for tandem use.

I am getting a custom steel tandem built. It is an unusual size with a small front compartment (I am 5'4") and a longer stoker compartment (5'10" stoker) with the issue being toe strike - tight tolerance here. Please understand that I am not a bike mechanic and learning so my terminology might be off. The recommended fork by the builder is steel with a 1.125 steerer tube. I have asked for a 44mm head tube and I was considering the ENVE 2.0 disc. But the sizing is different than the steel fork.

Steel fork from builder: HT 1.125, 395mm axle to crown, 55 rake
ENVE 2.0: tapered, 367mm axle to crown, 40 rake
ENVE CX fork: tapered, 395mm axle to crown, 47 rake

Sure looks like the ENVE CX fork would be a better fit plus allow for larger tires. The issue is the max rotor is 160mm. I want to find out if there is an adapter to allow for a larger rotor. I am in the process of working with the builder in making sure there is enough toe clearance (that said, the clearance on our current c'dale is only 58mm and toe does hit tire but it has not been an issue - but the builder is more conservative about this number wanting much more clearance). Feedback and suggestions appreciated.

update: just spoke with ENVE and the 160mm rotor spec is max because of stress on the fork so they don't recommend using adapter with larger rotor. Curious to know what others are using for rotors with their ENVE forks. ??

merlinextraligh

The ENVELOPE fork on our Calfee works great, but it's not a disc fork.

With regard to fork rake, I would spec the rake for handling,not to avoid toe overlap.

Toe overlap just isn't an issue. Only time your foot will hit the tore is tight turning at very low speeds, is easily avoided, and not a problem if it does happen.

akexpress 

+1^. If you are going to use a carbon disc fork seriously consider a thru axle fork. We are using the Whisky 15mm thru axle version on our Calfee with a 180 mm disc and it works great

fietsbob

I built a (sport-touring) bike frame with a bit longer top tube to solve Toe clip overlap (with Mudguards)

Its a single .. I noted the steering feel slightly lighter,
because the wheel moved a little bit away from the center of mass of me on the saddle.

the longer wheelbase of a Tandem that may not feel like that exactly..


FWIW, SJS Cycles inb UK recommends only a straight blade fork ( they sell steel).
disc torque would Un Bend the fork a Bit at a time ..

Another Disc Brake steel builder rakes the blades but oversizes the left fork blade where the disc mount is ..

The option Of a smaller front wheel may get the reach you want , without the TCO Issue , 26" instead of 700c/29"


But what is the resulting Trail of that combination?

BNB

I totally agree. I have big toe overlap with the c'dale and it simply has not been a problem. But hard to convince the builder who had a few returned bikes after crashes due to toe overlap. Sounded more like driver error.

BNB

Trail is something I'm just learning about and is a big deal to the builder. Not sure of the answer to that yet.

BNB

I'm checking that out @akexpress. Are you using the road version? What is the weight of your team and how long have you been riding it? Are you hill climbers - as in mountains - and, if so, have you used this fork for long climbs/descents? A pic of your bike setup would be great!

fietsbob

Trail is a better way to get a steering comparison between, A&B ..

I'm not going to use the other data to get that . you can , Its Your question .

sitting bike in front of you. head angle axis , plumb line down from the axle they intersect, cross, above the ground
Trail is the distance between those 2 points on the ground .

mtseymour

The ENVE CX (QR axle only) and Whiskey 9 Cross (thru-axle only) forks are good options. However, both of them require a tapered head tube (1-1/8" to 1.5"). My understanding is that it's difficult to make a tapered head tube in steel. Did you ask your builder if this is a deal breaker?

twocicle

Wrong info about needing a tapered head tube. Only the fork steerer is tapered.

For example, Calfee, Paketa and other builders usually provide a larger, straight 44mm head tube for their tapered fork compatible frames. This is what we have and then used a Chris King InSet-7 headset.

BNB

The Chris King InSet 7 was one option that ENVE gave me. As you said, you don't need a tapered head tube.

xlbs

From the original question, the builder's trail specs are different enough from the Enve options that I would suggest that taking the builder's fork is a no-brainer. When you pay the money to a builder to put together a custom frame to meet your specific requirements why on earth would you second guess one of the fundamentals that will determine the way your bike will handle and feel for every yard of riding? If Enve does not recommend their fork for tandem use, why would you second guess their engineers either? In the first case you are talking about ride quality and characteristics, and the second, potentially, your very life. I don't understand this second guessing at all. If I were the builder I'd walk away from your build---seriously!

BNB

And Happy New Year to you too!

xlbs

Here's my concern restated...disk braking on a tandem places much more demanding forces on the fork than it does on a single. The fork tips on the tandem fork must be configured to handle those forces; the angle of the tips determines how the axle is mounted to accommodate these forces; the angle is somewhat different from a CX fork. If the tips are not built properly the QR will not sustain the axle in the fork under heavy braking: braking forces will twist the front wheel right out of the fork unless the tips are built correctly. Result? Catastrophic crash...well documented.

Your builder certainly knows this, as does Enve. Your builder is liable if he builds a frame and fork that fails to provide you with safe braking management.

If you care to do the research on a variety of forums you'll discover that this very issue is a growing and current concern for frame-builders who are working on these problems actively.

Happy New Year's searching.

mtseymour

Thanks for the reminder about the 44mm head tube being compatible with straight or tapered forks. This will make it easier when we want to upgrade our fork.

twocicle

44mm is not the default HT size from Calfee, but available on request when ordering a frame. Getting a new frame?

mtseymour

Do you have examples of disk wheels coming off tandems or singles under heavy braking?

Dean V

Who knows someone that has actually had this happen? The QR system is not fool proof which has lead to the introduction of the Lawyer tabs on all forks. Also some QR mechanisms do not clamp well due to being flimsy and/or of poor design. But who has had a disc wheel move with a robust internal cam QR (eg, Shimano) that is properly done up??
I guess in some ways you could blame the introduction of vertical rear dropouts on the abundance of poor QR mechs and people that don't do them up properly. With horizontal dropouts if things aren't clamped properly you will soon pull the wheel and come to a halt.

xlbs

Here are some of the most comprehensive discussions I've found out there on this issue. with some of the world's most talented and recognized builders in on the discussion. They cover failures, liability, and remedies...If you will take the time to read through them you'll find that there is universal concern and interest about forks and disc brake failures among these fine builders. Hence my comments above.

broken dics forks
Thru Axle vs. Quick Release for Road Disc
fork blade specifically designed for disc applications - Page 2

twocicle

Many if not most QR levers these days use plastic cams. Cams increase the tightening/clamping force, but plastic cams can deform under high loads and result in a weak compression. Additionally, carbon QR dropouts cannot be tightened as much as metal dropouts, so that compounds the wheel security problem.

A year ago, I was startled to find what I thought was a very tight front Salsa QR slip rather easily on a carbon dropout.. enough to have the front tire move all the way over to the fork blade. This action was initiated while standing beside the tandem and pressing sideways on the captain's cranks (I was in search of a creak noise). Luckily, we were using a front rim brake and did not have any failures while riding. I can only surmise what might have happened if we had been using a front disc brake. Dumb luck, but I learned from it and decided to eliminate any possibility of QR slippage occurring on our new, full disc brake tandem by going with thru axles front and rear.

FWIW, none of our other bikes have had any front QR slippage issues with either Shimano skewers or Rolf. Sure I could have resolved the above tandem issue by replacing the Salsa skewer, but that issue underscored to me just how tenuous QR usage may be with a carbon dropout fork. Maybe passable for singles and rim brake tandems, but IMO not for disc front on a tandem.

marciero

I have also considered carbon fork options on our Cannondale. I would definitely get through-axle for disc. Our Cannnondale is QR, with the dropouts angled forward. This forward-facing design is a band-aid design fix on QR disc forks to prevent this wheel ejection that can occur, which is due to the rotational inertia of the front wheel. The way the inertial forces at the caliper and at the axle are related is the same as if the wheel were not moving and the brake were applied and you tried to rotate the wheel by gripping around the circumference and turning. It’s like the point at the caliper and axle are both competing to be centers of rotation. This puts the force from the wheel at the axle in the opposite direction to that at the caliper. On our bike, this puts that force on the lower tang of the dropout. I have not had any issues of slippage, and the fork and tang are pretty beefy so I dont fear for our safety, but QR is just not the right design for disc brakes, especially on the front. In the best situation you still pretty much need to over-tighten them. QR was designed 70+ years ago to facilitate quick wheel changes in races situation, with nothing like the forces from disc brakes in mind. Sure they can work okay, but not the optimal design.

joe@vwvortex

I've run pretty much what is considered on this forum as the worst brake setup out there - Avid BB7's on 203 ice tech rotors front and rear with a wound up carbon disc fork with Salsa quick releases for 5 years now with a 360lb team. NEVER had ANY issues with brake fade, QR problems or the like and the tandem has seen 70mph downhill. We've done numerous back to back days with long downhills which require significant braking and again - no loose QR's, no melted brake pads or plastic pieces. I feel very comfortable riding this bike with the setup I have.

mtseymour

The three threads that you cited don't support your claim that heavy braking will twist the front wheel right out the fork, nor is there "universal concern" from the "most talented and recognized builders".

The "broken dics forks" link from Velocipes was about a framebuilder who made a steel disc fork for his friend's polo bike. Newbe, self-described as a "new" builder, indicated that it was "actually just a crack, which was spotted before anything catastrophic happened, and on examination the blade was bent forward," He also explained that his brass brazing technique has "come along way, so getting it to (sic) hot may be the reason". There was no mention of the wheel twisting out of the fork.

In the 2nd article, "Thru Axle vs. Quick Release for Road Disc" from Velocipes, no one actually said that thru axle was safer or a better choice. On the contrary, there was hesitation to adopt thru axle wheels. OTF said that "I didn't get through-axles on the advice of several cross racers and frame builders. He identified concerns over limited wheel choices, lack of industry standard, and weight. He also said that "quick release still does just fine anyway as long as you use a good solid one like a Dura Ace or Hope." Another poster, dgaddis said that "From my experience riding two rigid carbon MTB forks back to back on the same frame/wheels, with the same geometry (AC & rake), both from Whisky, one TA and one QR - I don't see much need for TA on the road unless you're really driving the bike hard through corners (think crits). I could hardly feel any difference stiffness wise between the two. I'm getting the Whisky QR disc fork w/the fender mounts for mine anyroad/monstercx bike."

The 3rd thread "fork blade specifically designed for disc applications" (also from Velocipes) discuss the design and fabrication of steel disk forks. As with the first two threads, there was no mention of tandems, carbon disk forks, hydraulic disk brakes, or crashes (catastrophic or otherwise).

The statement that "disk braking on a tandem places much more demanding forces on the fork than it does on a single" ignore the extensive use of disc brakes in mtn biking under grueling conditions. First, no one has actually provided any measurements to show that tandem braking is more demanding than a mtn bike. Secondly, mtn bikes with disc brakes are routinely expected to handle steep, bumpy terrain. By steep, I mean 30-50 deg (not % gradient) slopes. Although some descents are very bumpy (with 3-5' drops), I have not heard of a QR wheel being twisted off by harsh impacts or heavy braking. Here are some photos to illustrate the abuse that mtn disk wheels are expected to handle.





I use thru axles (15mm and 142-12) on my full-suspension mtn bike, and like the idea of upgrading to a thru axle when our front wheel wears out. For us, the main benefit of the thru axle would be better handling and durability (w tapered steerer tube), with wheel security being a minor benefit. There is just no evidence that it's risky to use a carbon disk fork (w standard QR axles) from Co-Motion, Enve, or Wound Up.

marciero

The forces on a bike from bumpy terrain, jumps, etc, are all directed upward so do not play a role in wheel ejection like those from disc brakes, which are directed downward at the front wheel (assuming the caliper is directly behind the axle). Also, the braking force attainable is limited by the friction force between the tire and surface, which is much less on dirt. The greatest braking forces are attained when you combine high coefficients of friction (grippy tires, asphalt, grippy brake pads) with powerful brakes, and heavy bike/rider combination (for example, a tandem). Steepness of terrain would play a role only to the extent that skidding does not occur. This is simple F=ma stuff. Where these forces are applied, and their magnitude depends on the brake design. A little beyond simple F=ma. The only reason mountain bikes came up in the discussion is that they were the first bikes to use disc brakes, so they were the ones to experience front wheel ejection.

A search on "front wheel ejection" turned up a 2003 discussion involving none other than Jobst Brandt, who gives an example, and concluded that "this is not a safe condition [braking] when repeated often". The other main participant in that discussion is scientist James Annan, who brought one or more lawsuits in the early 2000's as a result of crashes that resulted from wheel ejection as a result of "...huge force on the front wheel, in the direction of the open dropouts." The simple example/comparison I gave in my earlier post is consistent with Annan's description and Jobst’s more quantitative analysis. (Am pretty sure Annan had a detailed analysis somewhere on the internet also but links in the thread do not work.) Since that time QR dropouts for disc forks have been angled forward, and it seems that most people are fine with that.

The surprising fact is that this whole phenomenon was missed by not one, but probably a fair number of design engineers. It must have been a real "Doh!" moment for them. Of course, they had to argue that the design was fine due to the liability.


Disk brakes and quick-release unscrewing (James Annan; Jobst Brandt)

reburns

I'm pretty agnostic on this whole deal. IMO disc brakes make sense in wet and/or dirty conditions. I've used one for years on my MTB fork with a QR and no problems. On our road tandem, which we ride almost exclusively when it's dry and sunny, I prefer rim brakes with a hub mounted drag brake for long steep descents, either disc or drum. Just my preference considering the pros and cons of which I'm aware.

But that said, I feel compelled to point out that there is a huge difference between the mounting of a disc brake to a suspension fork, frequently found on modern mountain bikes, vs a "rigid" fork found on most road bikes. Suspension forks are designed to be very beefy and absolutely stiff in every direction other than down the suspension axis. The massive lower portion of a suspension fork offers the perfect perch for a disc caliper. In contrast, despite the name, a "rigid" fork is intended to flex to provide the captain some level of isolation from road noise and bumps. The addition of a caliper mount capable of handling the stresses associated with braking a tandem necessarily will involve compromises. Whether these compromises rise to a level of concern are ultimately for the customer to decide, but they are non zero.