xlbs

Maybe we should circle some wagons here.

This thread has veered into trails that aren’t at all related to the OP’s question. How about we revisit that question.

That question was should we substitute an Enve CX or other Enve fork for the custom fork the builder has specified.

My suggestion was that the rake and type of fork that the builder has specified were different enough that the OP should take the builder’s advice.
The reasoning was that both the handling and the strength of the fork were critical elements for the overall success of the bike, and that the builder has, presumably, good reasons for his specifications.

In addition, I suggested that the substitution of said Enve forks was not in the best interests of the OP and his stoker because of the potential liability that this might incur for both the OP and the builder.

Now it seems that the thread has veered off into personal and anecdotal accounts both for and against…including the quite off-track notions that the major tandem forks are suspect and unreliable, and that tandem braking is no different from extreme mountain-bike braking.

So, how about we address the physics first. Tandem braking is different from other bicycle braking based on a simple equation p=mv or momentum equals mass multiplied by velocity. By this equation anyone can understand that the math indicates that a tandem, with a combined rider and bicycle weight of over 330 pounds (estimated rider 1=180, rider 1=120, bike =30 pounds), will take more to stop than a mountain bike with a combined rider and bike weight of 205 pounds (rider=180 plus bike=25). Since velocity is built into the equation it is clear that tandem braking is more demanding on the component braking system, regardless of the style of riding.

Disk braking owes a huge debt to the mountain bike community, for which there is no dispute, but tandem braking is different from mountain bike braking.

Second point, there are four basic levels of fork design around strength: road, CX, mountain, tandem. Road and CX are closely related in design for both handling and strength, with the CX forks being the stronger of the two. Then mountain forks are clearly more rugged than CX forks since the stresses are more extreme, as evidenced by latter posts. Then there are the tandem forks, all designed with to handle even heavier loads than mountain forks.

The tandem manufacturers out there understand this, as do the custom builders. Their tandem-specific forks are a marvel of strength and durability and good design, with the performance records to prove that. Their disk-braking forks are even more rugged.

Our original OP was asking about substituting CX forks for those that the builder has specified. I stand my ground here: risking a fork-set that is two levels below the strength and design of a tandem-specific fork, especially when Enve says that this is not a good plan, and when rake and trail do not match, is not an optimal plan.

BNB

What I'm really asking is what rotor sizes are other tandemers using with their ENVE forks.

The builder has given his "OK" for using the ENVE CX fork with our tandem.

twocicle

Sounds like your builder gave up trying to steer you and just said to go pick one.

You should be able to figure out what rotor size to shoot for, and whether or not that size is compatible with your fork choice.

If you are riding flat terrain and never sustained high speed steep descents, you probably can get away with a 160mm front rotor (the max size for ENVE). Otherwise, look for a setup that allows a 180mm front rotor. There are plenty of bike tech articles that discuss disc brake performance difference needs between road and mtn bikes, plus brake fade, etc, so if you are unsure of why a larger rotor is needed then go do some reading.

Note, while most forks list a "post mount" size of say 160mm, they may be compatible with larger rotor sizes (by using a front post adapter of course). For example, Whisky lists their max rotor as 185mm while TRP does not mention max rotor size (an easy phone call to their support).

Seems pretty clear that ENVE does not feel their fork is strong enough for a rotor larger than 160mm and I would seriously take that into account for fork selection. Two major factors to consider: 1) rider weight limit, and 2) max rotor size.

gsa103

ENVE is very reputable company, but they tend toward the conservative side of things. Having said that, a tandem is a huge braking stress, and I wouldn't exceed the manufacturers recommendations.

A better solution is probably to use a 29er disc fork. For example, the Niner RDO fork is rated for 185mm rotors. The ENVE carbon mountain fork is also rated for 180mm rotors.

Chris_W

The OP asked if there was an adaptor that would allow a rotor larger than 160 mm to be used in the Enve CX Disc fork, and I didn't notice that being answered already. The reason for the limitation is probably that there is material in the way that would prevent there being enough clearance for a larger rotor and/or the fork is not designed to handle the increased torque that can be generated with a larger rotor. So, even though adaptors do exist to put the brake caliper in the right position, you would be ill-advised to do so even if the rotor did clear the inside of the fork (which is unlikely).

We've put a Co-Motion carbon disc fork on our tandem, which we're very happy with (we previously had a steel V-brake model). The Co-Motion is carbon, made with a straight (1.125 inch) steerer, and uses a regular quick release (which is an advantage for us because we have a front wheel with a dynamo hub that we put in when touring).

BNB

It was suggested to me to get a Co-Motion carbon disc fork so I called CoMo. Unfortunately, they no longer sell their forks as an independent component.

More info: I spoke with a CF tandem builder that uses ENVE forks. The info I got from the guy I spoke with said they use 180mm rotors; 200mm rotors will not work as they don't fit with the road fork. Not enough clearance as you suggested.

akexpress 

We are using a 180mm rotor on the Whisky thru axle fork and it has very good braking with the Shimano 785 road hydraulic caliper. It has be quite resistant to fade on some long descents this fall in Croatia. At the time we were a 340 lb team. I recently put a 180 rotor on the rear also to reduce the vibration I had associated with a 203 rotor I had on the rear and it was also good braking with semi metallic pads. Since we have two discs now in our new Calfee frame the braking is confidence building in long steep descents. One issue to consider is the brake line used needs to be very high quality as the length is so long and it is a bit of a chore to bleed the system for the same reason. I think Landshark modifies an Enve fork to allow a 180 mm rotor.

Chris_W

Tandems East still have the Co-Motion fork listed on their website, so if you're interested then you could give them a call to see if they really do have one in stock: wwTandems East Forks & Handlebars. I got our fork last year from the official local Co-Motion importer in Switzerland, who had it in stock, so there's probably still some out there.

mtseymour

We plan to try the R785 hydraulic shifter and caliper with a 180mm rear rotor on our Calfee. What kind of hose did you use? Did you thread the hose through part of the frame or use external housing guides (eg. Jagwire)?

BNB

I saw that fork on TE too. Will talk it over with Mel because he also lists the ENVE fork on his website.

marciero

I was also told by Comotion that they do not offer their forks separately. But in addition to tandemseast, I found some listed on precisiontandems. (They also list comotion frames). I am guessing, based on the picture of the fork on the tandemseast site and the fork I've seen in the flesh on a couple of tandems, that the forks that are available from these two suppliers are leftover stock of an older style of fork, which they offered separately. The forks on the new bikes look different and also have tapered, rather than 1.25 straight steer tube. Pretty sure they have rack attachments also.

Chris_W

The Co-Motion carbon disc fork that we have does have rack mounts. I contacted Co-Motion to ask what weight the mounts are rated to carry, since such mounts on a carbon fork are very rare. They told me that 5 kg was the official limit, which is pretty minimal and barely worth it IMO. Fortunately, we also have a steel fork that we can use if we ever go serious touring and need front bags as well as rear.

radsmd

Would love to see more info, specs, and reviews about the Comotion tandem forks.

BNB

I spoke with one of our local tandem dealers and he said CoMo has a new, redesigned fork, as you suggest. He said they are not selling them because they can only manufacture enough for their own bikes. Not sure why that is but apparently the supply is limited.

waynesulak

Most likely because they do not manfactuerer them. Overseas supply chains can be complex.