Sep 3, 2001 1:04 PM
|I am looking at a Colnago bicycle and notice that the cbike website says the 55 cm frame has a 71.7 degree head tube angle. A 55 cm waterford (and most other makes) has a 74 degree head tube angle. How will the 71.7 dsegree angle affect the fit of the bike. Will it cause the top tube to fit shorter than other frames. Any help will be appreciated|
|here's a start...||C-40|
Sep 3, 2001 6:33 PM
|I've never seen anyone publish the head tube angles for Colnago frames, but I'll assume the published figures are correct.
Head tube angle has nothing to do with the fit of the top tube, but the seat tube angle certainly does. A 55cm Colnago (like mine) has a nearly 74 degree seat tube angle. To compare the Colnago top tube length to a frame like a Litespeed, which has a 73 degree STA, you have to add about 1.2cm to the Colnago 54.3cm figure, because the saddle must be moved back by this amount to get the same knee-over-pedal position. I can provide the simple formula by which this is calculated. With a Colnago, you want to be sure to use a traditional seat post with plenty of set-back, like ITM, Campy or DuraAce to permit the saddle to be moved back far enough. Don't even consider a Thomson, USE, or other similar seatpost.
The slack head tube angle will provide a little more distance between the toes and front wheel, if toe overlap has ever been a problem. The wheel base will also be slightly longer. The steering will also be slower than a bike with a 74 degree head tube angle and the same fork rake.
Colango's 71.7 HTA and 43mm fork rake will yeild a trail of 65.8mm. A frame with a 74 degree HTA would be likely to have a 45mm rake (maybe more). This would yield a trail of 49.5mm. The Colnago geometry is definitely set-up for long road races, not criteriums.
I've logged about 7000 miles on my 55cm C-40. I've been very impressed with the handling. Post again if you need additional clarification.
|I was told by the guy at trialtir-usa.com that||Live Steam|
Sep 3, 2001 6:47 PM
|the fork rake on all Colnagos is 42mm. They seem to be the only frames with this. I have been considering changing out my chromed steel fork for a carbon and he said that I could get away with a 43mm without changing the handling characteristics too much. He also said that Look used to make a 42mm but stopped as they are now making Colnagos carbon forks exclusively and don't want to compete with them for aftermarket business.|
Sep 3, 2001 6:51 PM
|A frame with a 74 HTA would be likely to have less fork rake (like 40mm)to slow down the steering a bit. This would still result in a trial of only 54.7mm.|| |