I have a Kabuki/Bridgestone that I have set up as a fixed gear around town errand bike. I really like it set up this way.

I converted this one on the cheap. I kept the original BB spindle, which was pretty long. So now, with one chain ring, there is quite a bit of spindle showing between the cranks and the BB shell. Maybe 5mm.

I have noticed that when I pedal hard (I am big and tall, and pretty strong, btw), there is a LOT of frame flex as I pedal. The BB shell seems to really torque around down there. At first I thought the cheapo plastic MTB pedals I had on it were flexing.

I have never noticed any bike I have ever ridden flex like this.

So, two questions,

-this must be largely a function of the overly long spindle right? (The frame is pretty heavy CroMo. Not all that lightweight at all. I am sure nothing is broken down there also.)

-Am I going to rip this thing apart?

jim

Steel frames flex alot.

Yeah. I have a whole bunch of steel lugged frames. But there is flex, and there is FLEX. I feel like I could tear this thing into two pieces if I really hammered up a hill.

Not sure how to measure flex, but this thing has a lot. And it all seems located at the bottom of the frame. I have been around bikes enough to not be surprised that a steel frame flexes. And this is defenitely more than normal.

I am about 220 pounds and can put a lot of power into the pedals. I have several older road bikes and one old MTB. I have worked them as hard as I can, and they never feel like they are being pushed to the limits of their structural strength. But, just tooling around town, I can feel this one bend all over the place when I pedal mildly.

jim

Jim, are you sure it's the frame that's flexing and not the crank arms and spindle? On the other hand, maybe the flexing is a sign of give and the dissipation of energy. But, hey, I 'ain't no metallurgist!

Neal

Is it a higher-end Bridgestone, or a lower end, gaspipe machine? I'd expect gaspipe to flex some - and in the case of real cheap-os, I'm not surprised by a half inch of flex or more.

Bull. Have you ever ridden a quality steel frameset?

Try out one of the Huffeigh-era, '84-86 Raleigh USA frames sometime. Stiffest steel frames you'll ever ride in your life. Won't flex a millimeter.

-Kurt

some of those Kabuki frames had cast alloy lugs around steel tubes, those did flex by just looking at them.

Are you sure the frame isn't cracked somewhere? Check carefully around the headtube and bottom bracket just to be sure.

Hey, I have one of those in classic orange. The seatpost is the kind with an expander bolt, and I'm still working on getting it out of the frame. I've achieved some movement, so that's a good sign. It's available for trade, btw.

Neal

This is a lower to mid range bike. The stickers say CroMo, which does not mean much, but perhaps not exactly gas pipe. It is not one of the earlier, real oddball, Kabuki's however. This is a pretty ordinary lugged steel bike.

I am very sure the frame is not cracked anywhere. Possible, I guess, but not my guess.

Is it really true that high-end bikes flex less than lower end? I would have naively guessed the opposite. Wouldn't a thick, hi-tensile steel frame not flex very much?

Some one asked if it could be the spindle or crank arms flexing. Surely a solid steel spindle that is about 3/4ths of an inch could not be humanly flexed? And I thought that aluminum arms would not really flex either. Wouldn't they just break instead?

jim

If anything is Bull the above quote is. Your frame is going to flex, are you're other frames fixed? Is it a sport bike? Does it have longer chainstays than your other bikes? All of these will factor in how much flex you are going to experience. Of course when you make a road frame into a fixed gear with really low gearing it's going to flex alot when you mash on it especially if it is a tall frame and you are a 220lb guy. If it bother you I would recommend trying something else.

As with most things it can be true that an expensive frame will flex less... for example you could get columbus SPX tubing which is thicker and has splines. Very stiff... then again you could have super light ishiwata tubing and that bike will flex alot more. It depends on the frame size. Better builders will use thicker tubing on larger frames. Personally I wouldn't want an 62cm columbus SL frame because it is bound to flex more than a 56cm columbus SL frame because A) the tubes are longer and B) the rider will likely be heavier on the bigger frame. All things to take into consideration.. as for your question about hi-tensile... I would think that all things being equal a hi-tensile frame would be stiffer than a chromoly frame but I welcome others to disagree and tell me why that is not true since I am too lazy to start looking up steel properties right now.

Perhaps the joints between the BB shell and tubing are poorly done? I would inspect this section as soon as possible, with a nice high-intensity light and a magnifing glass if nessesary.

-Kurt

My 1971 Nishiki competition's full double-butted Ishiwata CrMo frame had an inordinate amount of bottom bracket flex, but it got me through a three hilly centuries and a 12:18 double century and 40k cumulative road miles (65k km) before the seat tube lug finally broke away from the rest of the BB shell. In general, early 1970s Japanese CrMo frames tended to feel mushy, but the situation improved steadily during that decade.

Unremarkably, my Bianchi has far less BB flex than my Capo, reflecting a 20-year difference in design philosophies for long distance road racing machines, which had alot to do with the gradual replacement or covering of cobblestones by much smoother asphalt in Europe. On a sprint or a hill climb, I'll take the Bianchi, but on a century, I'll settle for the comfort of the Capo.

What the hell 'd you call lugs like that (semi-lugs, pseudo-lugs?) Damndest thing I ever saw. Great colour & headbadge, BTW!

Technically I would think they are still lugs, they're just made from alluminum. They work the same way.. they are the joins and the tubes are fitted into them. I think I may have read that on some of those frame the lugs were actually cast in place right onto the tubes, but I could be wrong.

What can I say? First of all, I have a real hard time being on the same page as cudak888 with the quality of '84-86 Raleigh USA frames. The first decent(and all I can say is decent) bike I ever had in my life was a 84 "Racing USA" Raliegh Gran Prix. Raliegh Propriatary 555 tubing and dropouts. The first thing I blew through was the factory built wheels. At the time I bought the bike, I was a college student in Pullman Washington. I was putting on about 30 to 40 miles a day training on the bike. A typical ride would be about 15 to 20 miles out and the same back in with about 2000 ft feet of hill climbing. When I got back into town I would really take advantage of the Palouse hills. I had several hill climbing intervals (elevation change approx. another 1000 ft.) to finish the day. The grades would push upwards to 20%. It was during the hill intervals that I would snap the pulling spokes on the freewheel side of the rear wheel. After I blew through the factory wheels I had custom made wheels made from Campy Record hubs and Mavic MA 40 rims (36 spoke). The next thing to go on the bike was the right rear dropout.

After I trashed the Raleigh frame I was able to get full credit (still under warranty from Raliegh) for the bike. I applied the credit towards a Holdsworth Professional frame (handbuilt Reynolds 531 with Campy dropouts). It was like night and day between the two frames. The Holdsworth was so much stiffer. I built that frame up with Campy Record and Suntour Superbe. In the time, I was going to Washington State University and riding that bike, I had four different wheelbuilders try to build wheels that I could not trash. I finally got to to the point where I learned to build wheels myself. The Holdsworth survived. That Holdsworth frame has been a Warhorse. You wouldn't believe what I have put that bike through. I could climb a 1000 ft. in a mile with a 42 tooth chainring and a 22 tooth rear sprocket. I called that hill spokebreak hill.

My testimony to the stiffness of the Holdsworth is this. The first thing (other than the wheels) to go on my Holdsworth was the Campy bottom bracket. I had to replace the bottom bracket and it was with what I could afford (and what was available) at the time. It was a Shimano sealed bearing bottom bracket. The spindle length was short and the clearance between the 42 tooth chainring and the chainstay was such that you could't put a piece of piece of paper between them. I am no slouch as a hillclimber. In my prime I have beaten the Junior national roadracing silver and bronze medalists (two different riders) in hillclimbs only to watch some seriously surprised looks on their faces. I could climb over 4,000 ft. in little over an hour. All on my Holdsworth. I have put that Holdsworth frame to ungodly tests breaking spokes and climbing seriously steep hills with my 6'1" tall 175 lb to 195 lb body. The only damage I could make the 42 tooth chainring did to my frame was to rub off the outer coat of paint. The primer remains.

cudak888 you can have the Asian built Raleighs. You have no idea what a real frame is.

Also, if you are getting that much flex in a frame, it's garbage or you are way too big for it.

Just stand on the side of the bike with the peddle at six o'clock. Hold the bike away from you, e.g., about 30 degrees, and push down on the peddle.

See how much the flex is? That's normal--really noticible on a larger steel frame.

It's not a bad thing and makes for a comfortable bike for many riders but maybe it's not for everybody. People that don't like flex might refer to a large frame steel bike as being a bit whippy. Mine is. Maybe try an aluminum frame and see if you like a stiffer ride better. I like the feel of steel so it's not a bad thing to me.

I believe you're being a bit harsh to both the OP (it still doesn't answer his question - if flex were an indicator of garbage, then you'd better start dumping all your Alan aluminum frames at my door) and the Raleigh USA frames themselves. Considering their position as framesets on mid-range machines (and I note, frames), they are exceptionally well done.

May I ask if you remember whether your frame was marked as being Made In Japan or Made In Taiwan? If not, do you remember how many bottle positions it had? The Japanese frames have dual waterbottle mounts, the Tawanese only have it on the downtube.

I have two of the Japanese examples, and one of the Taiwanese, but have not been able to experience the Taiwanese frame as much, as it is not my frame size. Both of my Japanese examples are very stiff and have no indication of any excessive frame stress (tearing, cracking, movement) on any one joint of the frameset.

I find it odd that the dropout did snap on your machine, hence why I'm curious as to it being Taiwanese or Japanese.

I'll concur with you that the original wheelsets to these machines were less then spectacular, I'll grant you that. Heck, what do you expect out of galvinized spokes, and with the Grand Prix, cheap Araya rims? That's what they came with - hence why my '86 is equipped with Mavic G 40 rims and Campagnolo Triomphe hubs laced with DT's.

My '84 Competition came with Araya shallow aero pattern though, hence why I'm sticking with those. Haven't had any trouble with them so far, and curiously enough, that's on the old galvinized spokes and Sunshine hubs. I plan to replace them with a set of NOS Arayas, same as the originals, DT's, and Campagnolo hubs, when I get the chance.

P.S.: I shall have one of my 60cm Guerciotti framesets built up sooner or later. I'll let you know if I notice any particular difference between the Guerciotti and the Raleighs.

Take care,

-Kurt

I believe my frame had two waterbottle cage mounts because I remember I went from two (on my Raleigh) to only one on my Holdsworth. Also when looking for a new bike I test rode an Alan aluminum just long enough to know it was a noodle. I mean a noooooooooooooodle. If I had an Alan frame it would be all yours.

I think when you ride your Guerciotti you will find that there is a big difference between a great frame and a decent one. It was like night and between my Raleigh and my Holdsworth.

Also to the original poster the spindle length can make a difference but should not contribute that much. Once again I am saying that frame is junk or he is too big for it. To be honest I think it is a combination of both. The frame quality is probably not that great (or maybe defective) and he is probably just be too big for it.

or just tell yourself they are that much better to assuage the guilt

You mean like this?

That is a beautiful bike. Mine is WAY more pedestrian than that. It is a pretty tall frame, and I know that adds more leverage to the flex mix.

Did anyone ever address the heart of my original question: does a long spindle substantially increase flex at the BB?

jim

Not an engineer but I don't think it would because the force on the axle is tortional not side to side. On my fixie which is based on an 80 cheapo Raleigh I flipped the bb axle end for end to get my chainline and bring the single outside chainwheel closer to the frame. It also has a real long bb axle but doesn't seem to flex unduly. As long as the frame is is good condition, no apparent cracks or defects I would probably ignore it unless you really are uncomfortable with it

I would seriously doubt that an inch longer spindle creates any substantial extra flex to the BB. Look upon it as a leverage arm against the BB - an inch extra is probably going to add just a small fraction of pressure to the BB shell.

I would not rule out, however, that a long spindle is under considerable more stress then a short one. That I am quite certain of.

-Kurt

Also not an engineer, but I would have thought there was considerable side to side pressure being put on the spindle. Now matter how pure your pedal stroke is, a vast majority of the force is being applied down. So, when you pedal down on the left, wouldn't the spindle be pushed down on the left?

An inch is not much, but if you consider that the total distance from the outer of the BB shell to the ball of your foot is maybe 4 inches, then that would seem to add 25% more leverage. Is this wrong?

jim