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


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 05-22-11, 06:37 PM   #1
green427
Senior Member
Thread Starter
 
green427's Avatar
 
Join Date: Apr 2011
Location: Dela-where?
Bikes: GT Fitness series, IBEX Vantage 5500, Raleigh M-80
Posts: 226
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Why huge holes? Rack mounting question....

Ok, I give up. This is the first bike I've seen that has huge holes, about half-inch diameter at the rear triangle ends.

I would like to mount a rack, but these holes were made for something else. I asked the mechanic on duty at the local bike shop, he says they are for the disc brake setup.

I looked at other GT brand bikes and noticed the ones that have disc brakes are using the two smaller holes shown, so the guy had no explanation afterwards.

So, can anyone edumacate me on the purpose of having big-arse holes at these locations instead of the normal smaller holes?

Thanks....






green427 is offline   Reply With Quote
Old 05-22-11, 06:53 PM   #2
10 Wheels
Galveston County Texas
 
10 Wheels's Avatar
 
Join Date: Nov 2007
Location: In The Wind
Bikes: 2010 Expedition, 03 GTO
Posts: 29,377
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 99 Post(s)
Post a link to the bike model.
__________________
[SIZE=1][B]What I like about Texas[/B]
http://www.youtube.com/watch?v=PGukLuXzH1E

Set F1re To The Ra1n ( NY Night Rain Ride)
http://www.youtube.com/watch?v=W7jfcWEkSrI
10 Wheels is offline   Reply With Quote
Old 05-22-11, 07:01 PM   #3
kingsting
Bicycle Repairman
 
kingsting's Avatar
 
Join Date: Sep 2010
Location: The Land of Three Mile Island
Bikes: Many
Posts: 598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Maybe this frame uses the same dropouts as a full suspension model? The big holes would be used for the pivot bushings. They look kinda kool on a hardtail...
kingsting is offline   Reply With Quote
Old 05-22-11, 07:04 PM   #4
fuzz2050
Real Men Ride Ordinaries
 
fuzz2050's Avatar
 
Join Date: Sep 2008
Bikes:
Posts: 3,698
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Obviously to save weight. Drill a few more yourself and you'd be surprised how light your bike can get.
fuzz2050 is offline   Reply With Quote
Old 05-22-11, 07:06 PM   #5
electrik
Single-serving poster
 
electrik's Avatar
 
Join Date: Aug 2009
Location: Toronto, Canada
Bikes:
Posts: 5,098
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Those are not functional rack holes.
electrik is offline   Reply With Quote
Old 05-22-11, 07:06 PM   #6
green427
Senior Member
Thread Starter
 
green427's Avatar
 
Join Date: Apr 2011
Location: Dela-where?
Bikes: GT Fitness series, IBEX Vantage 5500, Raleigh M-80
Posts: 226
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
http://www.gtbicycles.com/nomad-sport
green427 is offline   Reply With Quote
Old 05-22-11, 07:17 PM   #7
10 Wheels
Galveston County Texas
 
10 Wheels's Avatar
 
Join Date: Nov 2007
Location: In The Wind
Bikes: 2010 Expedition, 03 GTO
Posts: 29,377
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 99 Post(s)
Quote:
Originally Posted by green427 View Post
Thanks for the link.
No clue.
Guess you should use the contact link and ask the GT folks.
__________________
[SIZE=1][B]What I like about Texas[/B]
http://www.youtube.com/watch?v=PGukLuXzH1E

Set F1re To The Ra1n ( NY Night Rain Ride)
http://www.youtube.com/watch?v=W7jfcWEkSrI
10 Wheels is offline   Reply With Quote
Old 05-22-11, 07:19 PM   #8
Dan Burkhart 
Senior member
 
Dan Burkhart's Avatar
 
Join Date: Oct 2004
Location: Oakville Ontario
Bikes:
Posts: 5,926
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
That looks like a job for Wellnuts.
http://www.spaenaur.com/pdf/sectionC/C147.pdf
Dan Burkhart is offline   Reply With Quote
Old 05-22-11, 08:09 PM   #9
Ciufalon
Senior Member
 
Join Date: Nov 2004
Bikes: A few
Posts: 918
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I think the two smaller holes on the drive side might be for disc brake (not positive though). But the lack eyelets on the drive side tells me the bike is not equipped for rear rack mounting, unless you use the skewer type of mounting like the one available here. Seems odd since on the page for the bike that is linked to it says "all utility braze-ons."
Ciufalon is offline   Reply With Quote
Old 05-22-11, 08:47 PM   #10
Bezalel
Senior Member
 
Join Date: Mar 2010
Location: City of Brotherly Love
Bikes: Raleigh Companion, Nashbar Touring, Novara DiVano, Trek FX 7.1, Giant Upland
Posts: 1,508
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I wouldn't trust the published specs. they say 7000 series aluminum but the decals on the seatstay say 6061.

I don't think these holes provide any funtionality.
Bezalel is offline   Reply With Quote
Old 05-22-11, 08:54 PM   #11
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 7,912
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Quote:
Originally Posted by Bezalel View Post
I wouldn't trust the published specs. they say 7000 series aluminum but the decals on the seatstay say 6061.

I don't think these holes provide any functionality.
Well, they do, but only in a structural sense. They make the welding area larger, strengthening the joint between the dropout and the chainstay/ seatstay. Great place to accumulate mud, too.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline   Reply With Quote
Old 05-23-11, 01:04 AM   #12
Seb71
Senior Member
 
Join Date: May 2006
Location: Romania
Bikes:
Posts: 175
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Jeff Wills View Post
They make the welding area larger, strengthening the joint between the dropout and the chainstay/ seatstay.
I also think that this is the reason for the small sections of tubes (the two bigger holes on each side) in the dropout area - larger area for the welding.

The two smaller holes present only on the left side (above the seatstay) are clearly IS disc brake caliper mounts.
Seb71 is offline   Reply With Quote
Old 05-23-11, 01:30 AM   #13
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Jeff has it - it's obviously just a lightweight way of providing a decent amount of surface area for welding that's amenable to various frame geometries.

You should be able to use those holes to mount a rack with a bit of ingenuity. Maybe just a couple of large washers and some innertube wrapped around the mounting bolt.
Kimmo is offline   Reply With Quote
Old 05-23-11, 02:03 AM   #14
laura*
Shop Wench
 
Join Date: Mar 2009
Location: California
Bikes:
Posts: 284
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Kimmo View Post
Jeff has it - it's obviously just a lightweight way of providing a decent amount of surface area for welding that's amenable to various frame geometries.
Notice the small holes to vent welding gases? With these dropouts, the manufacturer wouldn't need to drill/punch holes into the stay tubes. I also suspect that the large holes position the dropouts onto a welding jig...
laura* is offline   Reply With Quote
Old 05-23-11, 02:12 AM   #15
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
That too, but I'd say the former is a secondary benefit.
Kimmo is offline   Reply With Quote
Old 05-23-11, 05:00 AM   #16
jimc101
Senior Member
 
Join Date: Oct 2007
Location: West Yorkshire, United Kingdom
Bikes:
Posts: 4,750
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
From the pictures, the holes on the frame are cosmetic / design, and the frame as shown is not designed for using racks.

The OP needs a different frame if he wants to use a rack; or use a QR system as noted in post #9.
jimc101 is online now   Reply With Quote
Old 05-23-11, 08:51 AM   #17
cobba
B A N N E D
 
Join Date: Aug 2006
Bikes:
Posts: 1,393
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Looking closely at the photos on the GT website, some frames with these dropouts seem to have a insert in at least one of those holes where it looks like a rack could possibly be attached.

GT Dropouts.jpg


Last edited by cobba; 06-02-11 at 10:48 PM.
cobba is offline   Reply With Quote
Old 05-23-11, 09:10 AM   #18
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by jimc101 View Post
The OP needs a different frame if he wants to use a rack; or use a QR system as noted in post #9.
Bah! Sif get another frame or marry your wheel to the rack when you have these holes waiting to be filled.
Kimmo is offline   Reply With Quote
Old 05-23-11, 09:41 AM   #19
Booger1
Senior Member
 
Join Date: Sep 2007
Location: Gaseous Cloud around Uranus
Bikes:
Posts: 3,688
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
It's so you can mount the derailer upsidedown,to keep from bashing it on rocks...

I'm guessing it's for production,set up in a jig and being able to use 1 forging for many frames angles.

Just put a bushing in it and use it for rack mounts.Alot stronger than a brazeon,you'd have to tear the whole dropout off for it to fail.

Last edited by Booger1; 05-23-11 at 09:46 AM.
Booger1 is offline   Reply With Quote
Old 05-23-11, 09:50 AM   #20
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,902
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 232 Post(s)
Perhaps you can use a bit of ingenuity, if you want to use it as a rack mount.

How about a rubber bushing with a smaller bolt thru it?
fietsbob is offline   Reply With Quote
Old 05-23-11, 09:53 AM   #21
Booger1
Senior Member
 
Join Date: Sep 2007
Location: Gaseous Cloud around Uranus
Bikes:
Posts: 3,688
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
How about a nylon bushing with a hole in it?
Booger1 is offline   Reply With Quote
Old 05-23-11, 09:53 AM   #22
Kimmo
bike whisperer
 
Kimmo's Avatar
 
Join Date: Dec 2009
Location: Melbourne, Oz
Bikes: copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
Posts: 7,099
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by booger1 View Post
it's so you can mount the derailer upsidedown,to keep from bashing it on rocks...
pmsl : D
Kimmo is offline   Reply With Quote
Old 05-23-11, 10:42 AM   #23
Dan Burkhart 
Senior member
 
Dan Burkhart's Avatar
 
Join Date: Oct 2004
Location: Oakville Ontario
Bikes:
Posts: 5,926
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Quote:
Originally Posted by fietsbob View Post
Perhaps you can use a bit of ingenuity, if you want to use it as a rack mount.

How about a rubber bushing with a smaller bolt thru it?
Well yeah. Kinda like the dodads suggested in post #8. I've seen them used in similar applications.
Dan Burkhart is offline   Reply With Quote
Old 05-23-11, 10:58 AM   #24
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,902
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 232 Post(s)
a length of rubber hose and some nuts bolts and washers.. a variation on a motor mount in your car.
sleeve just the right length around the bolt would expand the rubber tubing enough to fit tight
Nylock nut will keep it there

Dan's widget maybe, but the simpler pieces come locally.
fietsbob is offline   Reply With Quote
Old 05-23-11, 11:05 AM   #25
MichaelW
Senior Member
 
Join Date: Feb 2001
Location: England
Bikes:
Posts: 12,920
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
A nylon plastic bushing may work.
If you want to be really tight and secure, take one drilled out tube of nylon. Cut the tube in two at an angle so that compression will cause expansion (like and old style quill stem).
You will need a washer that contacts the frame tube.
MichaelW 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 02:49 PM.