Bicycle TutorBicycle Tutor

Show off your bike!

Related video tutorials:
LBS Says No to Stiffer Crank
#1
Does anyone know why a bike shop would tell me I can't put a better quality (stiffer) front crank on my bike? The one that's on there has a significant degree of flex in top gear, yet when I ask if I can get a stiffer one, they just give me answers like the one on it is fine, it would cost too much, it wouldn't really be worth it. I tell them I don't care what it would cost, that I would like to do it even if it meant the entire drivetrain would have to be replaced, but they just tell me again it wouldn't be worth it. Eventually that front crank will need replacing, so what are they going to do then? I'm not quite confident enough in buying and installing everything myself yet but I am learning everything I can.
Reply
#2
Not having any information on your bike and equipment, except that you are ignoring professional advice, its impossible to say anything technical. What exactly is flexing? Crank has lots of parts.

If it works do not fix it, ignore your itch to tinker.
Never Give Up!!!
Reply
#3
(07-24-2011, 06:09 PM)GeorgeET Wrote:  . . . If it works do not fix it, ignore your itch to tinker.

Ya gotta keep up George. Smile

I think she is referring to a previous post, she hasn't got a lot of them yet;
http://forums.bicycletutor.com/thread-3405.html

Steve
Junkyard Tools rescued from the junkyard!
Reply
#4
Spinning the crank while off the bike, I can see that the chainrings have a warp. While pedaling in top gear, the warp appears to be worse, the chain scrapes the FD (only when pedaling hard), and I've had the FD adjusted at the same shop, yet they cannot seem to set it up so that the chain clears the FD. They say it's due to flex in the crank, and when I ask for a stiffer crank, we start the same circle of logic they always give me. I had another LBS who was willing to do the job, but they damaged my bike and did a sloppy job on a previous repair, so I'm not going back to them.

Edit: I got the chain to clear by turning the FD slightly away from the crank and by adjusting screws on top of FD; the downshift from top to middle is a little screwy, but workable if I am pedaling at certain speeds.
Reply
#5
It looks like George is in a "cranky" mood and probably won't answer now. Smile But I will say that everyone could be much more helpful if we knew what year, make, brand, and model your bike is so we can offer some assistance.

Cranks are different on different bikes and might not be replaceable with newer styles, better quality, yadda-yadda.

Others here know much more about that than I do.

Steve
Junkyard Tools rescued from the junkyard!
Reply
#6
Bike is Electra Townie 21 speed, 1 year old and 1800 miles. I don't know model number or any more specific information as this particular bike has never been listed in Electra catalogue and some parts on it do not have same specs as similar models they do list. Front crank rings have had warp from brand new, rings are riveted rather than bolted together. Dealer was willing to put in higher quality crank, but went out of business before I could get it done. As I have written previously, I am completely willing to rebuild entire drivetrain and do not care about cost.
Reply
#7
Since it is about 150,000 degrees outside, give or take, I am still hanging around my computer today.

Your bike doesn't sound very common. Where did you buy it?

Here's my suggestion. If you can remove it, take it to as many LBS's as possible and try to match it up with one that has a little more substance to it. Many LBS's keep boxes of old parts around just for that purpose.

And RobAR has a bunch of old parts as well. If you were to PM him he might be able to let ya know. A photo of what you have would also help. And just in case you need the BB assy, maybe measure the distance left to right in millimeters.

Steve
Junkyard Tools rescued from the junkyard!
Reply
#8
Thanks Steve. Bike was purchased at approved Electra dealer who has since gone out of business; there is another Electra dealer in town, who are the ones saying a stiffer crank wouldn't be worth the money. BB spindle on my bike measured out to 127.5mm (was just replaced with a 127) while Electra catalogue lists BB on similar bikes as 118 or 122 (just an example of my bike having different parts).

I'm just wanting a front crank that isn't going to flex as much and that I'm not going to be able to bend with normal use, but it seems to be turning into a major headache. So I'm already buying some tools online and reading up, so likely what I will be doing is removing crank, shopping around for a better one and installing it myself. I'm fairly confident in my ability to change it out, but I'm still unsure about compatibility with other components on the bike.
Reply
#9
Hi BMG;

Are you anywhere near one of us who could help you out?

Many of us have the tools to remove the crank and BB, and measurement tools to provide accurate information for finding a replacement. It is hard to diagnose from far away with no pictures.
Nigel
Reply
#10
What me mad?? Never.

Just got back from a ride along the coast to a vintage Woody car show at a marina. That was nice. Some of them actually had wooden bodies from the frame up, wow. BTW its 75 degrees here on the coast.

AS per bike ye one of the things needed to get answers is information. It should at least have the name of the bike and of the components . Than a description of the problem . Photos are helpful if properly taken. One of the things we can help with is how to ask questions.

I looked up the Electra Townie and it seems to be a mid level cruiser/townie bike.

Do not know crank make/mode if available. Most likely manufacturers. Someone here may know now that the bike make is known.

If you see wobble just turning the crank slowly by hand (which is a good test) it seems that the chain rings may be not seating straight or that the crank shaft is bent. Bottom bracket out of line.

From your description it does seem the be a cheap set up if its riveted together.

Try grabbing the chain rings and pull back and forth away from frame see if there is play. Try to isolate the component that has play.

At that level of cost it should have been a better component. Ye replacement is also doable. Check Nashbar and some others for parts .
Never Give Up!!!
Reply
#11
Thanks everyone. Sorry no pics right now as camera is not working, but will try for some soon.

Nothing on crank is loose and there is no play whatsoever. The crank rings appear to be warped, but I suppose it could be a bent shaft or they are not mounted straight, as all rings move towards the frame together at the same point in their revolution; it is much more noticeable under hard pedaling, so I am guessing that the shaft is flexing. Would having a long (and cheap) BB spindle contribute to the degree of flex (mine is 127mm)?

Crank is forged alloy 170 mm triple 48/38/28 and I am not wanting to go smaller and would not mind going 50 on the top. I have square taper but don't mind switching to another style BB. I am limited by the post on which the FD is mounted and think I can only move FD up or down 3/4 inch or so.

I actually do have access to a fully equipped machine shop with basically every tool and measurement device imaginable (and some people to help if I can't figure out how something works), just don't have specialized bike tools like crank puller and BB tool.

With my work schedule and weather up here, I just realized that I will have only about 14 more days in which I can actually take the bike for long cruises (I normally put on 45-50 miles in 3 hours, so I move along pretty good), so thinking I should make this a winter time project. I'm way up north in Saskatchewan.

But yea, I'm not seeing any reason why the crank can't be replaced. It is going wear out eventually. And it's just the one shop saying it wouldn't be worthwhile to do it, but there's not many LBSs around here (one went out of business, one damaged my bike and wouldn't take responsibility, so choices are limited).
Reply
#12
Most likely the chain rings are warped . Look from side at the center and see if its going up and down too. That would indicate bend shaft or off center mounting.

You keep on talking about the shaft, if its the shaft you need a new bottom bracket too. However I think the problem is cheap rings. The shaft is thick doubt it could flex.

http://www.sheldonbrown.com/cranks.html

If the Bottom Bracket is OK changing the rings is easy . Its a square taper Bottom Bracket you say. So one like this will do. Make sure it comes with both arms.

Does the shop have small gear pullers? If so you can use one to pull the crank. or use Liquid wrench or like and loosen crank and gently tap off with a hammer and drift where needed. For BB you do need a special socket. Depends on type.

Is it this one?

http://www.rei.com/product/813222/electra-townie-21d-step-through-womens-bike-2011

or

http://www.rei.com/product/798551/electra-townie-21d-bike



http://www.amazon.com/Sram-Crankset-175mm-48-38-28-Square/dp/B004NKA6B6/ref=sr_1_15?s=sporting-goods&ie=UTF8&qid=1311564934&sr=1-15

http://www.amazon.com/Shimano-UN54-Bottom-Bracket/dp/B0039369B4/ref=pd_rhf_shvl_3


I looked at google satellite at Saskatchewan. Man its way North for sure. :-)) With so little riding time left do the fixes in winter.
Never Give Up!!!
Reply
#13
What kind of Canadian are you, using miles instead of metric? Wink I spent a year in Saskatoon, was quite nice (but winter was too long for my taste)... are you more to the north of the province?
About the flexing: I'd guess that the cranks are stiff enough, they are probably some lower end / really old (being riveted etc) thing, really heavy and stuff. I guess that the flex is in the frame when you push too hard. You should ride with a high cadence (also better for your knees).
Additionally, the chain rings are probably warped / bent (as others also remarked). If they were not riveted on you could simply take them off and check...
Replacing: I don't know what the specs are, but a square taper crank set is not too expensive (but don't go for the cheapest one), same goes for the bottom bracket. Tools will set you back an additional 30 bucks I guess (BB tool + crank puller). Check Alex's tutorials on how to do the replacement, it's not difficult.
Reply
#14
Thanks, I was actually already looking at the SRAM crank. Bike is similar to the second one. I've actually already bought crank puller and BB tool online. I will most likely be replacing the crank myself after the riding season is over here and will have about seven months to tinker with it.

I have actually thought about frame flex as well and was thinking at a later time of welding in some sort of reinforcement if the bike ever needs repainting. Some newer Townies are coming with triangle shaped supports welded in at the joints.

And yes, I am a ways north from S'toon. Metric -- I went to school before there was metric.
Reply
#15
Hey, good luck with the replacements! I guess you wouldn't find a crank set that has a chain ring larger than this one (MTB parts). You could try your luck mixing road and MTB (works at least for Shimano), but this would involve also getting a new front dérailleur as the limit for MTB fds is around 48 teeth (well, it might work with 50, too, might be worth to give it a shot). This will also give you a larger smallest chain ring (30 teeth at least). Another route to go might be using a road cassette in the rear, probably 11-25 or so (get the one with th matching number of sprockets[*]). This will give you a closer gear spacing as you probably don't need that 32 teeth dinner plate in the rear anyway[**] and should work without problems.
I figured you'd be from up North, September was still quite warm in S'toon, but up there you have like 9 months of hockey and 3 months of bad ice as I was told. I only ride through German winter (lows only about -20 C, wimps that we are), I think I wouldn't ride once it was below -30 or so (air is just too cold).

[*] yeah, thanks for blinding me with the obvious...
[**] though I was told that the steepest part of highway 1 is in Saskatchewan
Reply
#16
Thanks, I am looking at a few options but think I will stay with the 48 top ring on front as I can't really move the FD much higher, and I found a freewheel/hub that is one size smaller than the one I've got now, so that'll add a little more speed. I've never used that silly Alpine gear, so that will definitely not be on the new assembly (well, I did use it once, because I wanted to see if it was even possible for my RD to make that big of a jump).

And yea, I can usually only get out biking from late April/early May to mid Oct.
Reply
#17
I saw this billboard and thought of BloodMoonGrrrl. They would probably get more publicity putting that billboard out in California though. Smile
Junkyard Tools rescued from the junkyard!
Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  Crank Puller Failing to Pull Crank metellus 6 10,168 07-06-2010, 05:23 PM
Last Post: Billy

Forum Jump:



ISSN 1918-3445 © Copyright 2007-2010 Bicycle Tutor / Privacy Policy / Created by Alex Ramon

feed