Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Mountain Biking Mountain biking is one of the fastest growing sports in the world. Check out this forum to discuss the latest tips, tricks, gear and equipment in the world of mountain biking.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 09-15-02, 02:13 AM   #1
Seth
Junior Member
Thread Starter
 
Join Date: Sep 2002
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
How to tell a good frame from a bad frame

How could one go about determining whether a bike's frame is good or bad?

The reason I'm asking is because I was recently given a bike, and I have no idea of its quality.

The frame is unpainted aluminum with fairly large, visible welds. Are there any distinguishing features a well mad frame might have? a poorly made frame?

Thanks
Seth is offline   Reply With Quote
Old 09-15-02, 05:41 AM   #2
MichaelW
Senior Member
 
Join Date: Feb 2001
Location: England
Bikes:
Posts: 12,926
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Usually the easiest place to see quality is in the rear dropouts (where the wheel is held).
Next time you are in a bike shop, check out the detail on the dropouts in different price ranges.
The seatpost clamp is another good sign.

The really important things, like alignment and facing of the tubes is very difficult to see, and often overlooked by bike tests. Its really easy to make a cheap frame which looks good but is badly finished inside.
MichaelW is offline   Reply With Quote
Old 09-15-02, 02:27 PM   #3
Guillermo
Junior Member
 
Guillermo's Avatar
 
Join Date: Jun 2002
Location: Chicago
Bikes:
Posts: 337
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
visible welds are ok. Just look for uniformity in shape, thickness, etc. Isn't Al suppose to be painted though??
Guillermo is offline   Reply With Quote
Old 09-15-02, 08:28 PM   #4
Mashimaro
Senior Member
 
Join Date: Jun 2002
Location: Vancouver
Bikes:
Posts: 104
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
check to see if the beads of the welds are uniform...i believe a good weld would look like 'a string of pearls'. also check to see if the bottom bracket is clean and not sharp or rough..the surfaces of the tubes (ie: for headset/seatpost/bottombracket) should be smooth and the seatpost shouldn't scratch up going in and out.
Mashimaro is offline   Reply With Quote
Old 09-15-02, 10:25 PM   #5
Seth
Junior Member
Thread Starter
 
Join Date: Sep 2002
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'm bringing it to a reputable local bike shop to get it checked out.

I dont even know what kind of bike it is
Seth is offline   Reply With Quote
Old 09-16-02, 06:05 PM   #6
LockRobster853
Newbie
 
Join Date: May 2002
Location: Boro, England
Bikes:
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Measure it.

Get a piece of string and make sure stuff isn't ben't and all the lengths add up. Look for cracks and dings too.
LockRobster853 is offline   Reply With Quote
Old 09-16-02, 08:13 PM   #7
Seth
Junior Member
Thread Starter
 
Join Date: Sep 2002
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
the beads are very uniform, and everything seems to be perfectly straight. I didn't really bother measuring, because I don't know what the correct lengths are. Where is the serial # usually located? I need that to find out what kind of bike it is.
Seth is offline   Reply With Quote
Old 09-17-02, 07:55 AM   #8
faith
Member
 
Join Date: Sep 2002
Location: Reston, VA
Bikes:
Posts: 51
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Every bicycle that I've owned or serviced has the serial number stamped into the lower side of the bottom bracket (BB) housing. However the some instruction manuals I’ve reviewed indicate that the rear dropouts may have the serial number stamped on the inside of it. The front fork (if a shock fork) may also have it's own serial number.

An important issue with Aluminum Frames is their design life. Unlike steel and titanium, Aluminum will only take a finite number of stress cycles. While the manufacturing engineers design "extra" strength into Aluminum Frames to accommodate this, it least one major US bicycle builder is on record for stating a five-year design life for their Aluminum Frames.

Ask the mechanics at your Local Bike Shop (LBS) about Aluminum and frame failures and there is a high likelihood you will be told to "check the welded areas carefully for any signs of cracks” Although without "calibrated eyeballs" you might miss these sure signs of structural concerns. As for paint, Aluminum is sometimes "clear coated" with a polymer that makes it appear "unpainted".

If you are intent on extreme sports use, then please do have a skilled veteran mechanic look the frame over before you attempt any maneuvers that would challenge the integrity of the machine. Today I’m replacing a font fork (Shock absorbing variety) that sheared off at the steerer tube weld during a high impact-loading maneuver. In speaking with several LBS mechanics they indicated that the evolution of the shock absorbing front fork has now moved completely away from welds on the steerer tube, they are all now force fitted into the fork crown.

Extremely important resources are the “Recalls” listed on the Consumer Safety Commission’s Web Site http://www.consumeraffairs.com/recal...alls_sport.htm
Products are listed by year and vendor, also you can use it’s search engine with the serial number and find if there known significant issues with your product. There are many different bicycle vendors and models comprising thousands and thousands of individual bicycles currently on recall! The Front Fork unit that I’m replacing was on recall, which affected “24,800 mountain bikes” and was shipped to me at no charge by the vendor. Side Note: I had to request the replacement, it was not volunteered without solicitation.

Sadly the LBS community doesn’t endeavor to contact the folks to whom they sold the faulty equipment (it is the bicycle Vendor’s responsibility I was informed), however they do post the “Recalls” on their service departments bulletin boards, which is good.

And please always wear a helmet, ride within your known abilities especially in remote terrain and never ride at night. Thank you…

Cheers; Faith
faith is offline   Reply With Quote
Old 09-17-02, 11:19 AM   #9
Seth
Junior Member
Thread Starter
 
Join Date: Sep 2002
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
thanks, faith. Some good info there.

To get the most out of my trip to the LBS, what sort of questions should I ask about the frame/bike?

thanks
Seth is offline   Reply With Quote
Old 09-17-02, 11:55 AM   #10
a2psyklnut
NCAA - DUAL CHAMPIONS!
 
a2psyklnut's Avatar
 
Join Date: Mar 2000
Location: From Sarasota, FL sitting in front of a computer spewing random thoughts!
Bikes: Intense Uzzi SL, Masi Speciale, Trek 3700 Nashbar Single Speed, Old Cilo Road frame
Posts: 7,964
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hey Seth, do you have a digital camera or scanner capabilities. I'm sure if you post a picture here, the exhorbinant wealth of knowledge here will possibly turn out a manufacturer, just from the design of the frame.

L8R
__________________
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger
a2psyklnut is offline   Reply With Quote
Old 09-18-02, 03:35 AM   #11
tFUnK
Senior Member
 
Join Date: Jun 2002
Location: Menlo Park, CA
Bikes: GT Forte Ti, Ridley XBow, Specialized Tricross Sport, Specialized Langster, Xootr Swift
Posts: 2,278
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
does it look something like this? frame chopped by factory?

thats my frame, its cut at the toptube and welded back together. serial # found inside of the dropout not on the bb shell.
tFUnK is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:14 PM.