Frame not suitable for 70" fixed gear?

ive done a cheap conversion for a friend with a 52x20 70"GI. it rides pretty nicely.

when im really cranking it up a steep incline with alot of force there is a definate creaking around the bottom bracket area which has to be the frame flexing. theres no play in the BB and it was fitted by a good mechanic at the LBS so it cant be that.

is this frame just not really suitable for fixed gear? my guess is that becuase its a road frame, it was never designed for the force of a gear that tall being pushed hard up a incline. far more force is going through it than would be normal when it was geared.

when my friend rides it doesnt happen, but hes pretty new to bike riding and not as strong a rider as me. so it might well not be a problem until hes gets stronger, but im curious as to whever some frames just arnt built for the force that fixed gear provides.

what do you reckon? could this lead to frame failure? am i barking up the wrong tree?

Cranks? Pedals? Chain?

The amount of force going through a drivechain isn't as much as you think.

Huge pedalling forces aren't solely the preserve of fixed gear riding.

Either the frame has a flaw and is approaching failure (maybe the least likely option), or it's something else. I've heard sounds that were ***definitely ***coming from the BB area, but turned out to be:

• cleats
  
• external rubber seals on pedal axles
  
• saddle rails
  
• burrs on end of seatpost against seat-tube
  
• bar/stem interface
  
• cable/down-tube stop interface (okay, not applicable here)
  
• loose chainring bolts
  
• riding partners
  
• blah
  

tighten up !

70" is hardly a big gear... a good road frame should be able to cope with the force required to push it up a hill. 52/20 compared to around 52/12 at the high end of an average road cluster.

if by "cheap conversion" you mean "a cheap old road frame" then maybe the frame is fucked, but try the things that BMMF said before you chuck it.

As mentioned - people with gears pedal hard too! I just sounds like you've got a fairly flexy frame.

Chain ring bolts. Remove, grease threads and then really tighten them up. Worked for me.

my guess is that becuase its a road frame, it was never designed for the force of a gear that tall being pushed hard up a incline.
am i barking?

50 x 20? Yes, you're barking.
Your spelling's bonkers too...

bah im lazy with spelling on the internet.

i know its not a massive gear and that there are bigger on the cluster, but i doubt youd ever be riding up the kind of hills im talking about with that gear. im pretty sure its not the drivetrain, but the frame supporting it. the creaking is really quite loud and disconcerting.

the frame is a good condition purgeot, im not sure why i said cheap really, as it isnt other than its an old road frame.

im gonna give the chain ring bolts a go becuase thats the only thing i havnt tried yet, hadnt considdered that. i think it might just be flexy frame though.

Just make sure you've got the gizmo to hold the inside side of the bolts when you tighten them. Big screwdriver'll do it at a pinch...

i run my singlespeed 52/14,i rode it close on 50 miles today and my frame dont creak at all,but my knees do.route today was cycle streatham to victoria train to birchington on sea,cycle along the coastal trail to dover .then train dover to victoria ,then cycle victoria to streatham

you should HTFU or TTFU

i run my singlespeed 52/14,i rode it close on 50 miles today and my frame dont creak at all,but my knees do.route today was cycle streatham to victoria train to birchington on sea,cycle along the coastal trail to dover .then train dover to victoria ,then cycle victoria to streatham

you should HTFU or TTFU

...or just use public transport to take you to hill and traffic-free cycle paths, eh?

I had a similar gear on a road frame conversion (53/20) and got creaking from the BB/Crank area. Happened on the flat too, but was worse on hills. I reckoned it was the BB needing tightening/new bearings/replacing, but changed frame recently so haven't bothered fixing it.

hurrah! creaking has been resolved! turns out it was the chainring bolts that needed to be tightened. thanks for the tip.

reculver- well done on being such a hardman. i used to ride 52x18 here in cornwall and thought it was ok. until i changed down some inches and found myself flying up hills with a much higher cadance.

hurrah! creaking has been resolved! turns out it was the chainring bolts that needed to be tightened. thanks for the tip.

You're welcome.

Ner, ner, ne, ner, ner; I guessed first.

Nroa

melon ,not a hardman but a grockle ,i wussed out on some hills,but the bike makes up for it on the flat.btw st ives is a lovely place to live apart from the hills

i simply cant abide with getting off the bike becuase a hill defeats me, thats just cheating. unclipping before reaching my destination is also intolorable, but somtimes neccessary.

grockle is a dirty (wishes it was cornwall) devon word. the word "emmet" is the cornish term from an outsider or tourist. im not one of these patriotic cornish nationalist types though, and actually choose to live in other places sometimes. most cornish get a nosebleed if they go farther than bristol.

st ives is alright, but its full of self rightous middle class artists, who all want to open organic vegan muesli restuarants, and buy up all the great housing so the indigenous people cant live in thier hometown anymore. then theres the dickhead surfers who turn up every summer, to tell you all there is to know (there isnt much to know) about surfing at any oportunity, and the local wanker chavs to get pissed and cause trouble. with that said, it is quite a pretty place, and nice to visit if your doing it as a tourist.

(wishes it was cornwall) devon

Yeah? Your not selling it to me.

i sometimes have a creaking noise when i'm pedalling hard that sounds like it's the bb but it's actually just my saddle flexing on it's rails

I also have a Single Speed '89 Peugeot geared to 52x17 which creakes likes hell when pedalling up hills. I think that it is just frame flex....certainly hasn't caused me any problems....yet!

Is'nt the force experianced by parts after the gear (eg rear axle, chainstays etc.) the same regardless of gearing? I would of thought this was the force required to push bike + rider up the hill at a certian speed.

(I might be thinking rubbish though, it is monday)

eerm, 70" is a small gear. so no it wont be a problem!
i ran 84" on my old conversion with no problems. i think small furry is right, no real forces acting more on a fixed bike?

70" is a medium gear :p

Is'nt the force experianced by parts after the gear (eg rear axle, chainstays etc.) the same regardless of gearing? I would of thought this was the force required to push bike + rider up the hill at a certian speed.

(I might be thinking rubbish though, it is monday)

No, that's power (Watts).

Power is energy/time. The amount of energy you need to get to the top of the hill is largely fixed (ignoring speed-dependent energy losses, e.g. aero), if you do it faster then you need more power.

Power is torque*rpms. Same power, less rpms (e.g. bigger gear) means higher torque or more force on the pedals.

It's also to do with pedaling style. Two riders, same gear, same speed == same power. However, if one puts down all that power over a fraction of the pedal cycle, the peak torque can be much higher than that implied by power=torque*rpm.

That's why spinning and fixed gears are good - it forces you to be smooth with your power delivery!