Specific custom Rake/Trail question

[Catrin]

Is a rake of 45 (head angle of 70) significantly different from a rake of 50 with a head angle of 71.5? I only know the trail of one of these, though I am trying to get the trail from Surly directly.

I am starting to understand the difference between rake, trail, and how head angle matters. I am trying to wrap my brain around the possible different handling between my LHT and the Gunnar recommended specs.

[lunacycles]

Trail for 26" wheels (assuming 1.5" tires):

70 deg Head angle with 45mm rake = 66mm trail
71.5 deg head angle with 50mm rake = 62mm trail

I personally would go with the latter. But it's not a big difference.

[Catrin]

Trail for 26" wheels (assuming 1.5" tires):

70 deg Head angle with 45mm rake = 66mm trail
71.5 deg head angle with 50mm rake = 62mm trail

I personally would go with the latter. But it's not a big difference.

Margo, thank you, I had hoped you would see this. The 71.5 deg head angle with 50mm rake is what Waterford is recommending for my Gunnar custom build. It appears to have a trail of 54.7 if my fitter has recorded this properly - is that possible with the given head angle and 50mm rake? I do not know what tire size they are assuming for the Gunnar. The basic design is based on their cross frame, and they are recommending an upgraded Waterford road fork (for weight, and I won't be putting racks on this bike).

I am looking at some hand-written notes he gave me that compares the custom specs with my LHT - and the wheels are indeed 26'. Both chainstay and wheelbase are quite a bit shorter, if that matters.

[lunacycles]

My error. I read it wrong on my CAD program (it's an image on top of an image, and my reading glasses are at work with my welding helmet). 71.5 h.a. with 50mm rake is 52mm, not 62mm of trail based on 26 x 1.5 inch tires (your fitter may have used a different tire profile to arrive at the other number..and it's 56mm, not 66mm of trail for the other combo). I like a trail of 60 mm plus or minus a few for this kind of bike, but builders have a lot of opinions around this based on their own biases, insofar as what constitutes "ideal handling." IMO, a higher trail is better if there is no load on the front. A lower trail will be theoretically livelier in terms of front-end handling but also maybe less stable/more "twitchy." Typical road bike trail is 55mm or so. But it also depends on your stem length, body weigh distribution, blah blah blah, as to what's best.
A fork with more rake will be more plush, theoretically. A head angle of 70 degrees is the very lowest I would go. 71.5 sounds a lot more reasonable for a frame using 26" wheels.
Ultimately, seriously, this is all within normalcy, so I'd advise that you trust your builder. It's Waterford, after all. They've been doing this a while.

[Catrin]

....
Ultimately, seriously, this is all within normalcy, so I'd advise that you trust your builder. It's Waterford, after all. They've been doing this a while.

Indeed, that is my perspective as well! I am just trying to better understand the design to help me justify the cost. Waterford does beautiful work and have great people

My fitter encourages his clients who are getting a Waterford or Gunnar to talk directly with the frame builder so that all three of us (designer, fitter, and customer) are all happy when it is time for me to to literally sign off on the final design.

Thank you Margo, I appreciate it!

[lunacycles]

Cool. It's great you want to be in the know about all of it, even this minutiae which can make customers (and builders) a bit nutty... It's also cool you are going this route. I think it makes sense, it's great you're asking questions, and I hope you love your custom Gunnar!