Tandem Cycling - Rake for an ENVE fork?
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Okay, I've been reading a lot of posts, and I'm only more confused. What would be the best rake for an ENVE fork? "Best" in this case means most stability at high speeds but ability to steer effectively when maneuvering around at low speeds. From what I'm reading, it would seem a longer rake would work best for this application, but I'm also seeing that the opposite may be true. At this point, you can get 43,45 and 50 mm of rake. I can't tell what is usually used, but it appears 45 is most common on tandems. Is that also a "safer" amount of rake with regards to the forces applied to the fork?
Any input would be much appreciated.
There is no perfect rake, it depends on the bike. A number of things including the ht angle determine what rake should be used.
If you are replacing a fork already on a tandem, what is its current rake? when replacing a fork, it is best to get a fork with close to the same measurements.
08-30-12, 06:19 AM
Very true there is no perfect rake. The type of riding, tire width used, and personal preference play a big roll. I have ridden 45mm, 50mm 55mm, and 60mm rake forks. More rake on the same head tube angle will ride very differently and many who try a higher rake reject it before riding it long enough to acclimate and see all its benefits, including less required counter steering.
I like high rake lower trail tandems but generally less rake is more popular. To give some perspective below are some major tandems and the fork rake often used with a 73 degree head tube. All ride well but differently.
CoMotion race carbon forks 43-45mm (& many 3rd party carbon forks on other tandems)
CoMotion Steel Forks 50mm
Santana steel and carbon forks 55mm
My Bilenky fork 60 mm
The great thing about forks is that you can replace your fork and completely change the handling of your tandem. If you are going to ride a lot of miles, consider purchasing two and give both a few thousand miles before you decide what you like.
08-30-12, 02:47 PM
What would be the best rake for an ENVE fork?
1. What brand/model/year tandem are you considering it for?
2. What are you trying to accomplish: a direct replacement, or a change in handling?
3. Are you willing to do some trade-offs if the ENVE isn't a "direct replacement fork"?
Unless you're a bit of a geek, your best bet is to consult the company that designed your tandem to get their recommendation based on where your head is on the answers to Questions #2 & #3.
Here's the deal, ENVE's forks use an axle-to-crown dimension of 367mm compared to most stock tandem forks @ 395mm to 400mm. Therefore, unless a tandem was designed around an ENVE (or a True Temper Alpha Q X2 for that matter, as they use a 374mm axle-to-crown dimension), you're going to alter the geometry of your tandem's head & seat tubes as well as lowering the front bottom bracket height.
Many of us have gone ahead and made the trade-off in geometry/cornering clearance against the lighter weight and vibration dampening characteristics of a composite fork and adjusted just fine to the change. Some of the first Alpha Q's made by AME used 48mm of rake and the early Wound-Up tandem forks used 47mm. 45mm eventually became the default. However, if your tandem was designed around a 73° head tube angle, lowering the front end of the tandem by 2.1mm for an Alpha Q would increase / steepen that head tube angle to something closer to 73.5° or 74° depending on the length of the tandem's wheelbase. So, you didn't get a linear change in steering trail when you went from say a 50mm steel Co-Motion fork to a 45mm Alpha Q given the associated change in head tube angle that came with the shorter fork. The ENVE fork just exacerbates that condition since it's another 7mm shorter than even the Alpha Q. Now days, you have folks like Co-Motion and Calfee designing their tandems around these single-bike-based fork designs to fine tune the handling so that there aren't any trade-offs and any good custom builder who has spec'd a composite fork for a customer's tandem has likely done the same when setting the head tube angle and adjusting front bottom bracket placement for toe-overlap considerations.
Again, many tandem owners have switched to composite forks on tandems that weren't designed around them without ever considering the geometry changes and quickly adapted to the net result and continue to enjoy the way their tandems handle. Many of these changes in geometry are only an issue for teams where the captain is very sensitive to bike handling nuances and/or has a stoker that is either large or prone to moving around a lot... and for those teams adding steering trail is not always the right answer. It's also worth noting that the net change in handling will be greater on tandems produced by Cannondale who spec's a 53mm rake fork as well as Trek, Santana and a few others who spec'd a 55mm rake fork and KHS, Bilenkly/Sterling and others who used varying head tube angles and fork rakes that were even greater than 55mm.
Just some food for thought.
Wow, thank you all very much for the help! I will report back with a ride report when done.
09-01-12, 10:42 AM
......... Now days, you have folks like Co-Motion and Calfee designing their tandems around these single-bike-based fork designs to fine tune the handling so that there aren't any trade-offs and any good custom builder who has spec'd a composite fork for a customer's tandem has likely done the same when setting the head tube angle and adjusting front bottom bracket placement for toe-overlap considerations. ......
Lots of good information in TandemGeeks's post. The head tube angle calculation is very useful. I think however that he may be overstating the builders design care and expertise when building tandems with carbon forks. Using CoMotion (a fine company) as an example, when they built tandems with steel forks they used a 73 degree head tube angle and a 50mm rake fork. When using carbon forks, Alpha Q, Woundup Composites, or now Enve they still use the 73 degree head tube angle. Some of these forks have different rakes. It appears to me that many tandem builders like the 73 degree head tube angle regardless of the fork used. This is not a terrible thing and I suspect that there are production reasons for taking this approach. It appears many builders don't sweat a few degrees of fork rake on there production non-custom geometry frames with carbon forks.
One exception for good or bad is Santana which believes in 55mm rake and 1.25 steering tube forks. They sources their own carbon forks and specify 55mm on the carbon ones to match the 55mm on the steel ones that they make in house.
09-01-12, 12:53 PM
I think however that he may be overstating the builders design care and expertise when building tandems with carbon forks. Using CoMotion (a fine company) as an example, when they built tandems with steel forks they used a 73 degree head tube angle and a 50mm rake fork. When using carbon forks, Alpha Q, Woundup Composites, or now Enve they still use the 73 degree head tube angle. Some of these forks have different rakes. It appears to me that many tandem builders like the 73 degree head tube angle regardless of the fork used. This is not a terrible thing and I suspect that there are production reasons for taking this approach. It appears many builders don't sweat a few degrees of fork rake on there production non-custom geometry frames with carbon forks.
Actually, if you ask Co-Motion I suspect they'll tell you they specify the shorter rake forks because they have found that performance-minded customers prefer having steering trail that's even longer than what's yielded by their 50° rake fork-equipped tandems.
Bear in mind, as an OEM they have their own house-branded composite forks -- the tandem Elite models in both caliper & disc versions -- and they have geometry & dimensions that are very similar to the ENVE fork. However, before they developed their own forks and before they used the True Temper Alpha Q X2 forks, they partnered with Wound-Up to develop a tandem-specific composite fork. It was spec'd with a 387mm fork leg-to-crown length, a little shorter than their normal steel fork spec at that time and 47mm of rake. Since then they've reduced the rake to 45mm.
But, getting back to the 367mm - 374mm length forks like the ENVE, Alpha Q and Co-Motion's Elite, the "race" tandems they spec' those forks on are designed around the shorter length fork -- which is also true of Calfee, etc. -- relative to bottom bracket height, etc., but maintain the 73° head angle to get the designed steering trail & handling characteristics they want for those tandems.
It's not accidental design, it's all very intentional.
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