Jaysus cycling! (1 Viewer)

flashback

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it *does* actually lean a little back from the head tube. but there's no sign whatsoever of any crash damage.
speaking of which, i think the bars did take a little bit of damage, the left drop is bent inwards by a degree or two. did not spot that in the dark car park when i bought them for a tenner.

I don't any of us here can honestly say we've never made mistakes in dark car parks in Mullingar.
 

magicbastarder

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secondhand on the cycling adverts forum on boards. it was barely used, came in its original box, the proofing wax hadn't been opened. you sometimes get some great bargains there. i recently got a pair of aksiums in good nick for €50 there too.

also, i managed to place a bid on this last night, it's too big for me, but i know two guys it'd be the right size for. for the price of a bottle of whiskey...

 

magicbastarder

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picked this up today - too big for me (22") but i know a chap who was looking for a project but probably now won't take it. was only 25 quid, so have offered it to another friend.
it's a sun super vitesse, 531 tubes (assume it's just main tubes), seller reckons it was made in the raleigh factory on hanover quay in 1952; i haven't found any records of sun bikes being made there though.PXL_20210202_162726968.jpg
 

ann post

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picked this up today - too big for me (22") but i know a chap who was looking for a project but probably now won't take it. was only 25 quid, so have offered it to another friend.
it's a sun super vitesse, 531 tubes (assume it's just main tubes), seller reckons it was made in the raleigh factory on hanover quay in 1952; i haven't found any records of sun bikes being made there though.View attachment 14610

I don't know anything about Sun but i know the Irish Built Raleighs have different badge on the front, possibly not saying location if that would help. A quick google of a sun bike showed me the birmingham ones said birmingham on the badge below the seat post.
 

the_jen

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Fat tyres don't have higher resistance (like I thought they did), because the area of the point of contact with the road is only the same size as with skinny tyres, and the shape of that contact patch is better.

"That short wide contact patch of the fatter tyre results in less tyre casing deflection" and "the wider tyre is able to absorb imperfections in the road so energy normally lost moving the bike and rider up and over a bump with a narrow tyre is conserved, resulting in a lower rolling resistance."
 

magicbastarder

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i *think* if i understand correctly, skinny tyres do roll faster, but only if the roads are billiard table smooth. that then goes the other way once you start to cycle on normal roads.

i've also read a theory that people think they are faster because they conflate two things:
1. skinny tyres give a harder ride, more vibration up through your arms, etc.
2. the faster you cycle, the more vibrations you'll feel

therefore, fast = vibration; skinny tyres = vibration, but people then think skinny tyres=fast
 

flashback

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The way I understood it was energy that was previously moving you forward is translated to energy moving you up, and this energy isn't recovered perfectly on the way back down. This is the dominating source of energy wasted in tyres.

Then there is another loss of energy: rolling resistance, but this is relatively less.

So yeah, what you're both saying. Energy up = waste, energy converted into heat/rolling resistance = waste, but less.

The ideal tyre would absorb all up/down movements, transferring none into the rim/bike. Any mechanism to damp the inputs (pressure/width) is going to give you a lot of efficiency. Rolling resistance isn't negligable, but the difference between an 18C tyre and a 26 isn't as big as people were thinking about. (Then there's tubs/tubeless/inner tube which also effect rolling resistance, but it's really on a diff order of magnitude than the up/down stuff.)
 

the_jen

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I don't have the clearance to go messing around anyway, I've just baaaaarely squeezed mud guards on with 23s, but it's interesting!
 

magicbastarder

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i was asking about wheels once in duff cycles, and the sales guy there insisted you should run your tyres at whatever the max pressure allows. he was cycling - to work in santry - on 25mm tyres running 140psi. i decided not to trust his judgement on wheels.
 

flashback

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i was asking about wheels once in duff cycles, and the sales guy there insisted you should run your tyres at whatever the max pressure allows. he was cycling - to work in santry - on 25mm tyres running 140psi. i decided not to trust his judgement on wheels.
sounds crazy, but when I was living in cold places I'd often pump the tyres in my apartment and when I'd be out on the road the wheel would cool down so much that I'd feel the pressure being off.

In the end if I wanted 80psi or something I'd have to kind of guess at ~100psi, and see how it worked out a mile down the road.
 

rettucs

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I used to always go for 120 in the summer, and 100 in the winter (it was always recommended to drop the PSI a bit in winter for extra grip, and extra 'give' against debris. That was when I was running 23s. I moved to 25s a few years ago and instantly felt I had more control on the bike. I've run 100 PSI on the 25s all year round. Never had trouble, regardless.

I read a study a few years about about the difference in rolling resistance between 23 and 25 and it was shown there was no difference at all (probably because of what magicbastard was saying). I'd say that might change if you go to 27 (I think 27 is the max clearance on most racers?) or above.

My work bike is a hybrid with 35mm. It goes like an old dog, but I need that for the city streets (or will whenever I'm allowed cycle to work again).
 

magicbastarder

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i run 25s at 80psi and have never had any issues at that pressure; i heard the rule of thumb is that with 25s, you can run 1psi per total weight of bike and rider.

i *have* had issues when laziness meant i let the pressure drop and had pinch flats as a result. one of which led to a gas situation when i had the tube replaced and was just about to reseat the tyre, a french lady walking past produced a puncture repair kit she obviously was carrying around for stricken cyclists, and was crestfallen when i told her i didn't need it.
 

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