Cycling UK Forum

Barrowman wrote: ↑8 Aug 2024, 1:43pm Got to agree. Imagine trying to ride one of the Olympic Track Bikes . Stiff as a board .
Decent 'old school' touring bike . Ride it all day every day.

Brucey wrote: ↑8 Aug 2024, 12:04pm my take on it is this; frames that are likely to be too flexible are also likely to be noticed and rejected, well before the flexibility actually slows you down much. Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

mig wrote: ↑8 Aug 2024, 2:37pm for most of my biking year i'm on a hack commuter fixed frame that uses stiff 35/37c rubber. it's functional but not a thrilling ride.

when the sun comes out for those 2 days a year then the 631 summer bike comes out. made in 2002 (although still thought of as my 'new' bike) the thing is both a revelation in terms of ride comfort yet no doubt a dinosaur in terms of modern bike set ups. 32 spoke open pros on chorus 9 shod with 23c schwalbe ultremos. you'd think that i'd be uncomfortable on such slimline covers yet not a bit of it. it really is the 'magic carpet ride' that is often spoken about.

now i'm not sure that i can pick out any one contributing factor to the 'compliance' of the bike over another but i do know that the sum of the parts makes for an excellent bicycle. i'm still managing with rim brakes too!

my crashed mercian was a similar beastie. get on, ride for as long as you need, get off. pure, simple stuff.

531colin wrote: ↑8 Aug 2024, 3:12pm 631 fork blades are interesting, in that the taper starts immediately below the canti. studs.

peetee wrote: ↑8 Aug 2024, 2:08pm Transfer of l, and effect of forces applied to a bike frame is a very complex subject and, although I have made significant inroads, I’m not fully up to scratch yet. Many years ago I used the limited knowledge I had to great effect with a custom steel MTB frame where I chose every single tube from a Reynolds list. It’s fantastic to ride and way better that a ‘tubeset’ model from that time.
I do believe that it’s possible to have a compliant and responsive bike frame if the builder considers the riders needs, weight, power and riding style and has access to the materials and tooling for the job.
I understand that rigid frames feel (and usually can be) faster and that almost always results in a harsh ride - how can it not?
Well, perhaps by making the frame more resistant to lateral and torsional forces because it’s those forces that come in to play when full-gas efforts such as out-the-saddle sprints or hill climbs are on the cards. This can be achieved with a substantial main ‘triangle’ ie, head, seat, top and down tubes. At the same time lighter gauge seat stays can be used - perhaps curved to perform the same function of a front fork. Along with a stiff frame a short wheelbase is advocated for maximum results but maybe a better option would be slightly longer chainstays so their horizontal section can be maximised between the crankset and rim/tyre. Wide but vertically slim chainstays would be stiff horizontally and compliant vertically which takes us further in the right direction.
I am, of course, referring to these tubes individually and, as inferred earlier, things are not that simple. No tube in a frame works independently and any force applied to one will affect an adjacent tube in one way or another. Likewise no force is independent and whilst transferring power the frame has to track straight and true, support the riders weight and deal with braking and road forces in a controlled manner.
That heavy main tube and slim stays look was a strong feature of early Cannondale road frames.
I’m not a great fan of aluminium bikes but stole myself to buy a 1990’s ‘Dale which was immaculate and can’t have had more than a few yards use as the rims have no brake block marks whatsoever. I have a bit of recommissioning to do on it but I’m keen to get it down the road to see if that performs to my liking or not and compare it to my steel and titanium bikes.

slowster wrote: ↑8 Aug 2024, 5:10pm the dimensions of the non-disc touring blades are the same for 853 and 631, suggesting that the same tubes are used for both, the only difference being the final heat treatment for 853. In that case 853 ought to have the same taper profile, and the stiffness of the blades should be identical.

Yet Dave Yates was adamant that 853 forks were too stiff for touring/audax, and recommended Reynolds' basic 'R' blades instead (as well as often persuading customers to have frames of 631 rather than 853).

531colin wrote: ↑8 Aug 2024, 3:04pm

Brucey wrote: ↑8 Aug 2024, 12:04pm.... Some people even think flexible frames are faster. My view is that it might be true in some cases, if perhaps the flexible frame makes you pedal better.

I may be mis-remembering, but didn't you tell us (long ago) that the lateral force generated by pedalling is entirely (or almost entirely?) reacted by the seat tube?