suggestion for headtube angle

[flyingbalut]

Request for suggestions: What headtube angle would you use with a 700C carbon fork with a 4.9mm rake (offset)? Customer wants a responsive yet stable handling bike. I'm thinking 70 degree head angle?

[e-RICHIE]

You can't isolate a measurement atmo. What frame size, saddle height, and reach are needed? Start here.

PS when you are the frame maker, you don't make the frame to fit the fork. You design it all, and then find a fork that complements. Better yet, make the fork. It's part of the whole, not an accessory.

[afwalker]

49mm rake I'm guessing you mean. Can you draw it up in bikecad (pro or free java) and post the pic to give some idea of the whole dimensions you are working on?
Trail, front center, tube lengths, bb drop etc.
cheers
andy walker

[Peter Polack]

Cervelo's RS model used a 72 degree head angle with a 49mm rake on their 54cm frame.

Independent Fabrications paired a 50mm fork rake with a 72 degree head angle for their stock road bikes 53cm and smaller.

With Trek's Domane, the specs are as follows: frame size/head angle/fork rake.

56cm/71.9 degrees/48mm

58cm/72.0 degrees/48mm

60cm/72.1 degrees/48mm

62cm/72.1 degrees/48mm

If these brand name manufacturers and a limited production shop/custom shop can pair similar head angles and fork rakes, I don't think you can go wrong with a 72 degree head angle/49mm rake, regardless of what size the frame is. A millimeter either way in fork rake isn't a deal killer.

[Rody]

Guys, if I may so bold as to continue Richie's train of thought from my perspective, a custom bicycle needs to be designed to fit under the rider, carefully balancing his physical needs with that of the performance goals. You cannot select a set of specifications, borrowed from manufacturers who design for the mean average, and expect to come out the door with a vehicle that meets that individuals goals.

There are many necessary attributes that have to be identified that drive the dimensions of the bicycle, ultimately placing the bike under the rider and the tires to the ground. To pick and choose geometry unrelated to the customers needs, hoping to create a fit and performance goal, is an unproductive strategy.

There is no correct formula that works for each customer, it is instead like putting together a puzzle while being an active listener. Take a look at his physical requirements, his current position on the bike, what he likes and does not like about the current fit, physical conditions 25/50/75/100 miles into a ride, how his current bikes are set up, what type of riding he intends to use this bicycle for and his performance goals, etc...then add in your flavor on how you believe the bike should feel and be configured to achieve his needs.

These are the items that drive the fit and ultimate dimensions of the bicycle. Create it from the rider down, not copy someone else's print for an unknown datum.

If you are creating this for a "customer" and do not have a working knowledge of bicycle design, work with a more experience builder to help you begin to understand and gain this insight before accepting more custom commissions. As experience grows, you will define a set of specs that blend rider type with how you want your bikes to feel and perform, providing consistency.

You will not always hit the target, but the more informed you become, the more accurate your interpretation of the end product will become.

[flyingbalut]

Thank you all for the feedback, information and advices.