Wheel flex

[ColinJ]

^^ What he said, Aksiums on that bike, why? It's a bit like putting fast wheels on a bike then adding slow tyres.

I've just weighed a nice old Campag Proton that I have lying about and wondered why I haven't put that on my Cannondale instead of the Khamsin which is on there now. It is only about 50 g lighter but the Khamsin has a nasty pinned joint on the rim which causes judders when braking.

 

[User6179]

^^ What he said, Aksiums on that bike, why? It's a bit like putting fast wheels on a bike then adding slow tyres.

Being 15 stone myself I doubt the OP would benefit from lighter faster wheels , when your 15 stone you just want something that's going to be durable which the Aksiums are up to a point .

 

[totallyfixed]

Being 15 stone myself I doubt the OP would benefit from lighter faster wheels , when your 15 stone you just want something that's going to be durable which the Aksiums are up to a point .

I was just giving an analogy, that said there are plenty of lighter yet stiffer wheels out there, for a price of course that will handle your sort of weight without problem.

 

[Fab Foodie]

If you can bear to ride something other than the fahsionable 20 front/24rear spoke wheels I'd strongly recommend learning to build your own wheels. H+son Archetypes look pretty cool, even with 32 spokes. Mine are on Hope hubs but you are looking at a lot more ££ than the Aksiums. Still, for an s-works Tarmac.... got to find something a bit better than Aksiums.

Bling!

 

[Yellow Saddle]

.Unless some spokes are completely loose it is not spoke tension that is causing your wheel flex but a lack of sufficient spokes. Spokes are made of steel, a material that obeys Hooke's Law. Basically this means that for a given force, the spokes will strain (elongate) a fixed amount irrespective of the tension in the spoke. If you tension them more, they will still flex just as much. You are experiencing frame or wheel flex or a combination of the two. Further, unless you have spokes with zero tension in them, your wheels are just as still now as they day they were built. Steel does not become less stiff with use or age.

 

[ColinJ]

Standing on the pedals with the back brake on and leaning against a wall, I could flex the stays but not enough to make the tyre rub. What happens when I am riding is that I can cause the chain to rub on the cage of the front mech if I really stomp on the pedals. If I pedal more smoothly then it does not happen.

Not anything to do with wheel flex, but since I mentioned my flexing frame above, I will tell y'all what I discovered today which may be of use to somebody one day ...

I was riding my Basso in the big ring and came to a short uphill slope at about 5%. It wasn't worth changing down a ring so I stood up and yomped my way up the rise and the characteristic chain-rubbing sound started. It dawned on me that the rubbing continued over the top of the hill even when I was no longer flexing the frame much. It turns out that the lateral movement of the bottom bracket seems to pull on the front gear cable and move the derailleur cage inwards. I have to retrim the mech to stop the rubbing and it is then ok unless I stomp down on the pedals again.

This might be because my shifters are 15 years old and the ratchet positions on the left shifter are worn and are pretty easy to change between now. The flexing of the frame probably pulls the cable hard enough to 'unclick' the shifter one or two stops.

I'll try holding the left shifter lever up against its endstop and see if that stops the problem occurring.

 

[Cyclist33]

That's interesting. I noticed something similar with my Specialized Roubaix Expert SL4 bike. When I'm pedaling up steep hills, if I get off the saddle to pedal, I hear a rubbing sound which appears to be coming from the front wheel. The forks for these bikes seem to be pretty solidly built, so perhaps the wheel is flexing? I have 36 spokes rear and 32 front, so I'm surprised at this behaviour.

I had something similar and traced it actually to the tyres, those particular ones, on either set of wheels on either bike, produced a feeling of "rubbing/flexing" when pedalling hard. I don't use them any more.

 

[Yellow Saddle]

I had something similar and traced it actually to the tyres, those particular ones, on either set of wheels on either bike, produced a feeling of "rubbing/flexing" when pedalling hard. I don't use them any more.

Tyre flex cannot cause rubbing on the frame. The flex will be between the tyre and rim only and then only at the contact patch, out of reach of the frame. I do agree that some tyres make the rear of the bike fishtail with hard pedaling.

 

[Cyclist33]

Tyre flex cannot cause rubbing on the frame. The flex will be between the tyre and rim only and then only at the contact patch, out of reach of the frame. I do agree that some tyres make the rear of the bike fishtail with hard pedaling.

Which is not at all what I was talking about.

"hearing a rubbing sound" does not necessarily mean there is a tyre rubbing. As I said, in the case of my "rubbing sound" it turned out to be the tyre producing a feeling of rubbing, it doesn't mean it actually was. It had something to do with the tyre compound and/or tread and the way it felt on tarmac under load.

Notwithstanding that, surely if you fitted a tyre that was almost too large for a frame, and underinflated it, then under load it would splay out sideways and could rub against the frame.

Stu

 

[Yellow Saddle]

Which is not at all what I was talking about.

"hearing a rubbing sound" does not necessarily mean there is a tyre rubbing. As I said, in the case of my "rubbing sound" it turned out to be the tyre producing a feeling of rubbing, it doesn't mean it actually was. It had something to do with the tyre compound and/or tread and the way it felt on tarmac under load.

Cut cut cut

Stu

Sorry, I misread your statement.