Numpty IM Bike Thread

Bike ponces only welcome if they don't speak in tongues

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PSC    pirate
28/03/2012 at 16:55
it is the numpty thread don't panic.  All numpty's welcome and the only questions that are genuinely stupid ones are the ones that you don't ask. 
31/03/2012 at 13:38
Bit of a long shot maybe but anyone live near Brixham/torbay could recommend a spin class - going down there next week and fancy doing a couple of sessions just to tick over.
31/03/2012 at 17:57
I'll make an enquiry Pops of someone who does live that way!
Cheerful Dave    pirate
31/03/2012 at 20:10
Celt6776 wrote (see)
2. When fitting the extensions originally, you need to open the valve and put insulating tape around the thingy-me-jig to keep the valve open.

The reason they do that is not to keep the valve open (the tyre pressure keeps the valve closed as FB says), but to stop the little screw nut working its way back closed while you're riding.  If that happened you wouldn't be able to get any air in the tyre without taking it off the rim.  Unlikely to be a problem during a ride (unless you're trying to use a sealant inflator after a flat) but you won't be able to top up the air before the next ride - some tubular tyres don't hold pressure for very long.  Vittoria Evo Corsa, I'm looking at you.

Not that I've known that happen - I prefer the type that FB mentions using a removable core.  The only snag with that is that you really need to get your spares set up beforehand, extensions and all, but it does mean the valve is always outside the rim.

IronCat5    pirate
01/04/2012 at 20:55

Update: Barse now bedding in, and I find it a lot easier to ride the TT bike long distances. Happy bunny.

Numpty question #187070775:

What can cause the back of the bike to start wagging and it feel like I have a puncture. As the bike curves round bends it almost feels like the tyre is being rolled off the rim, or the wheel is bending? I've had this twice this week, both on long rides, and both whilst going very fast (so I assume descending - today certainly was).

Tyres were topped up before I left. Front to 80psi, rear to 90. Rear was close to 85 when I got back. As I was descending I can imagine there wasn't too much weight on the rear wheel. I did try and push back on the saddle, but it kep going until I slowed down.

Any ideas?

Also - does anyone else wander all over the road on their TT bike; is this something that defines us as triathletes? I do seem to get blown around a lot.

02/04/2012 at 10:06
C5 - I would suggest that you up the psi in the tyres. you're no heavyweight I know but you'd be better running them at 100-110psi (front and rear). what tyres are you running out of interest??

I'd also check your spoke tension as if they are a bit slack that could contribute to the feeling you're getting. you can tension them yourself or if you're not happy with that, get the LBS to do it.

and TT bikes do tend to wander a bit more - usually pilot error (you have less overall control whilst aero), or due to crosswinds affecting deep rims (if you're running them)

02/04/2012 at 13:59

Fell off my bike whilst stationary yesterday. Not for the first time . Was trying to open a gate and just plopped over sideways onto my right side (the gear mech side). An hour or so later when changing down onto the small chain ring for a hill, the rear mech snagged in the spokes of the rear wheel, dropping the chain and un-seating rider for a second time.

How likely do you reckon it is that the impact of the first bump has pushed the rear gubbins inwards and got it too close to the spokes? And if that's the case, any suggestions for how to shove it back out again without doing more harm than good?

02/04/2012 at 14:14
stil - sounds like the rear mech has been bent in enough to impact the spokes when in the lowest gear. I suspect the mech hanger's not been bent by much and you should be able to bend it back yourself BUT you need to be very careful when doing so.

first off - check you have a replaceable rear mech hanger - the bit where the mech bolts to the frame - it should be easy to see if it's replaceable or not as that bit will screwed to the frame. if it's not - get the LBS to sort it as they will be more experienced. the last thing you want to do is snap the non-replaceable rear hanger!!

next check where the bend is - chances are it's the hanger that's bent. if the cage (the bit that holds the jockey wheels) is bent, then you'll need to replace that.

as for doing it yourself, you need to be able to provide sufficient force to bend the hanger unit back to straight - and do so slowly rather than overstress matters. it's really down to feel I suppose and then the difficult part is getting the unit straight.

unbolt the mech from the frame after removing the chain and using a good length adjustable spanner, tighten the adjustable onto the hanger and then SLOWLY bend the hanger back. a long handled spanner will allow more force and more "feel" for what you're doing. you may need to play around a bit to make sure it's straight (you can get a tool for this but for a one-off job, eyesight is usually fine)

but if in ANY doubt get the LBS to sweat it for you.

next time - fall the other way....
Edited: 02/04/2012 at 14:25
02/04/2012 at 14:18
Thanks, as always, FB. Off to the workshop with a coffee and a lump hammer .
02/04/2012 at 14:27
have another read - I've made some amendments
IronCat5    pirate
02/04/2012 at 14:31

Could be a bent mech hanger STIL

FB - I'm running Schwalbe Ultremo ZX (cunning labelled with 95-145psi on the side...). PX Model B wheels, so about 30mm rims.

The huge Speedfil may have something to do with x-wind issues; it fills the front triangle quite nicely.

02/04/2012 at 14:39
don't see that those tyres would be an issue C5 but you still need more air in them especially if they're rated as they are. try them with 120 in and see how that feels.

also check the spokes tension, and the other thought I had was that the QR wasn't tightened up enough allowing a little play. you probably wouldn't notice this when riding a straight line, but any looseness would be more noticeable at speed on a bend as the wheel is trying to come out of the dropouts.
02/04/2012 at 15:09

I now know what a hanger is, if the hanger is the shiny alloy bit that the wheel skewers tighten onto and the black geary bits attach to? Anyway, that's the bit that was bent. It's not bent now, or at the very least, it's not bent enough to get in the spokes. Thanks as always!

cougie    pirate
02/04/2012 at 15:18
Cat are you on the tribars anyway ? That will make you more prone to wandering across the road.
02/04/2012 at 16:02
stil - spot on description of the mech hanger - "shiny alloy bit that the wheel skewers tighten onto and the black geary bits attach to" 'cept hanger is quicker and easier to say.

have you checked that the gears index OK now??
02/04/2012 at 16:55

Haven't put the wheels back on yet. Need to mend the puncture in the front and I was thinking of changing the rear cassette to the more tenby-friendly ratio I got bought for chrimbo.

Good chance that tomorrow will see me taking pieces of bike to my LBS .

02/04/2012 at 17:57
it might be worth looking at getting a new mech hanger while you're at it. even though you've straightened it, the metal will now be a a little weaker so will bend more easily in any future hits. it will be fine for the moment, but it's worth thinking about replacing it - it shouldn't be too expensive to do so.
IronCat5    pirate
02/04/2012 at 18:13

hurrah for STIL's club hammer.

cougie wrote (see)
Cat are you on the tribars anyway ? That will make you more prone to wandering across the road.

Yes Cougie, on the tribars. I officially have no handling skills when aero.

So Schwalbe recommend 115psi for a 75kg rider, and that's about me and the bike combined. So possibly the tyres are squirming. I had wondered if it was speed wobble, with the bars damped and the back wobbling?

QR is tight. The drive-side tension feels higher than the other. I may drop the wheel in the shop next week.

I'll try 115-120psi. Thanks FB, you are a vast font knowledge!

03/04/2012 at 09:54
[bows humbly......]

Cheerful Dave    pirate
03/04/2012 at 13:55
Cat5 in the Hat wrote (see)

Thanks FB, you are a vast font!


FTFY

[sorry FB, couldn't resist]

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