Cycling UK Forum

Brucey wrote:I
this
https://www.sjscycles.co.uk/seat-posts/307-272-mm-gold-kcnc-sc13-twin-seat-post-clamp/
is both the normal seat clamp and a top collar in one.
CUT

After expieriencing a slipping (carbon) post on my China made titanium frame I ordered a similar double clamp ( it's on the market in al lot of brands/names) which solved it immediately., a good, solid solution.
After 2 years the thing annoyed me and I pulled out the titanium sleeve (which I thought was welded in, and it turned out it was not), replaced it by a an aluminium one an a normal (campagnolo) clamp and never had any problem after that.

Had teh same , many years ago, also a folding bike , and repaired it.
A small bar in which the pulling pin screws was broken.
Not difficult for someone who is familiar with SA 3 speed hubs.
After the repair it had only 4 speeds left, the top one was gone, never missed it, the 5 speeds were not the most reliable SA hubs...

That's why I use exclusively pre 2007 9 and 10 speed Ergopowers, they never gave me trouble the past 8 years and IF they do, I've numerous spares laying around.
Better avoid any Powershift Ergo's.
The 11 speed Ultrashift ones seem also good, but I don't need nor want 11 speed

So you don't think gussets thicker than frame tubes are a stupid idea?
So buy another similar frame ....

Main limitation is the size of the seat tube.
On a 28,6 and 31,6 seat tubes the 111 mm BB is fine, on bigger seat tubes you'll need the 115 mm.

Poor construction of that frame....
I guess the designer/builder of that frame never saw this animation, it shows that the lower gussset is completely unnecessary:

Samuel D wrote:I remain convinced that what you feel while cycling is almost entirely irrelevant to performance and the only way to understand these phenomena is through physics, albeit imaginatively applied. The idea that you can feel any difference in rolling resistance between a 23 mm tyre and a 25 mm tyre is far-fetched. You cannot even measure these tiny differences in the noisy real world with simple methods. That’s why we need lab tests of rolling resistance. Even the comfort difference between 23 mm and 25 mm tyres at appropriate pressures is in the just-noticeable range and dwarfed by imagined differences.

Exactly my opinion.

You seem to have something against physics......

Mick F wrote:

Keezx wrote:You don't have to be a physicist to know that moving mass, once up to speed ,does't need energy to keep moving.

Until you come to a hill.

Still no energy needed for moving/turning the wheel, only for bringing the mass up against gravity.

Alan O wrote:

Keezx wrote:You don't have to be a physicist to know that moving mass, once up to speed ,does't need energy to keep moving.

Not in a vacuum with no friction it doesn't, no.

Still, air resistance and friction is independent from mass.

You don't have to be a physicist to know that moving mass, once up to speed ,does't need energy to keep moving.

I think you got my point.
On a hilly course 5 kg makes a difference , but 120 grams in the wheels, really?
All over the world people are brainwashed about wheel weights, 1400 grams are light and 1800 grams are boat anchors.
For me it's not much more than fetishism.

Then explain to me what difference it makes....(on a flat course), (theoretical and not anecdotal)

mullinsm wrote:

Keezx wrote:IF you compare 2 tyre sizes, then you should use tyres with comparable construction/carcass/thread, otherwise it's useless.

The 23,25 and 28mm were all Conti Gatorskins. The only difference apart from the size was the weight. Rolling resistance theory says the 28mm should be quicker on the roads in question, but they aren't. I suspect the difference therefore is the weight and I imagine that the extra 60g between the 25s and the 28s makes as much difference as the 60g difference between good wheels and very good wheels.

Weight does matter a little bit when accelerating but nothing noticable for your average speed.
No way 60 gr./wheel would have any significanty influence, the tyre width does matter for air resistance though.
My guess is you sit also a bit more aerodynamic on the faster bike.

PS 1 thing which isn't even mentioned here is the fact that the rim inner width influences the tyre width, contact patch and riding properties significant.
Food for thought:
https://intheknowcycling.com/2016/04/03 ... eel-sizes/
I don't bother anymore about 23 mm or 25 mm , take what I can find for a good price, put them om 18C or 19C rims and pump 5-6 Bar depending on the expected road surface.

IF you compare 2 tyre sizes, then you should use tyres with comparable construction/carcass/thread, otherwise it's useless.