a simple question of threads
10-31-08, 01:59 AM
#1
Senior Member
Thread Starter
a simple question of threads
Ok mechanics - how do you spec a screw that screws into the rack and/or fender mounts. I installed some Planet Bike fenders today (first rain of the year in my part of N. Calif), and the bike only had one point (boss?) for a rack or fender, not two like my touring bike.
Two stays from the fenders and one from the rack had to fit into one hole, and the screws provided were too short. They even say so in the instructions (thx, planet bike!). So if I go to the hardware store, what am I looking for? You know, threads per inch, or whatever the metric equivalent is.
Don't care to much about the head, but a 4 mm allen wrench type of head would be nice for consistency.
Two stays from the fenders and one from the rack had to fit into one hole, and the screws provided were too short. They even say so in the instructions (thx, planet bike!). So if I go to the hardware store, what am I looking for? You know, threads per inch, or whatever the metric equivalent is.
Don't care to much about the head, but a 4 mm allen wrench type of head would be nice for consistency.
10-31-08, 02:12 AM
#2
Large Member
take the short screw with you and match the threads that way. you'll also enure you DO end up with the correct length, rather than buying one that is embarrassingly only 1 mm longer, though you could have sworn it looked longer in the shop.
10-31-08, 02:13 AM
#3
Senior Member
Join Date: Sep 2006
Location: Paradise, TX
Posts: 2,087
Bikes: Soma Pescadero, Surly Pugsley, Salsa Fargo, Schwinn Klunker, Gravity SS 27.5, Monocog 29er
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 186 Post(s)
Liked 234 Times
in
166 Posts
Should just be 5mm allen head bolts. If you are unsure take one with you and find a nut in one of the parts bins that matches it. Then you will know the size.
10-31-08, 04:47 AM
#4
Senior Member
Join Date: May 2003
Location: Mountain Brook. AL
Posts: 4,002
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 303 Post(s)
Likes: 0
Liked 136 Times
in
104 Posts
On our tandem the rack mounts were 4mm OD at the top of the chain stay but
5mmx.8mm at the dropout end. Get screws at least 20mm long for fender +
rack. If the rack is to be loaded might be better to avoid local supply and look
into internet ordering to get the equivalent of 8.8 grade screws. 20mm is
pretty long cantilever for a loaded rack. Stainless might not be a bad idea
either.
5mmx.8mm at the dropout end. Get screws at least 20mm long for fender +
rack. If the rack is to be loaded might be better to avoid local supply and look
into internet ordering to get the equivalent of 8.8 grade screws. 20mm is
pretty long cantilever for a loaded rack. Stainless might not be a bad idea
either.
10-31-08, 10:57 AM
#5
Senior Member
Be sure to put the rack stays close to the drop-out eyelets first, then the fender on top. This keeps the heavier load on a shorter moment-arm on the bolt and applies a lower cantilever load.
10-31-08, 11:48 AM
#6
Senior Member
Join Date: Feb 2001
Location: England
Posts: 12,948
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Likes: 0
Liked 7 Times
in
7 Posts
M5 thread, stainless steel, allen head.
Get the order right: bike frame dropout, luggage rack, fender stay, washer, bolt.
This way the heavily loaded rack is not levering at the end of the bolt.
For the rear dropouts make sure you have a couple of threads protruding the other side but not enough to touch the chain.
Get the order right: bike frame dropout, luggage rack, fender stay, washer, bolt.
This way the heavily loaded rack is not levering at the end of the bolt.
For the rear dropouts make sure you have a couple of threads protruding the other side but not enough to touch the chain.
11-01-08, 01:05 AM
#7
Senior Member
Thread Starter
Interesting ideas. I never thought of the quality of the bolts, just the threads per inch (or mm) and length. And definitely didn't think too much about the order of stays (oh maybe about 10 seconds).
Got some long bolts today at my LBS and re-installed everything correctly. This is my grocery bike, not my touring bike. It will have some load, but if it breaks, it will be close to home. Nevertheless, I'll keep my eye out for some hi-quality bolts to replace the ones I got today. If anyone has an online source ...
Got some long bolts today at my LBS and re-installed everything correctly. This is my grocery bike, not my touring bike. It will have some load, but if it breaks, it will be close to home. Nevertheless, I'll keep my eye out for some hi-quality bolts to replace the ones I got today. If anyone has an online source ...
11-01-08, 06:36 AM
#8
surly old man
Join Date: Sep 2006
Location: Carlisle, PA
Posts: 3,392
Bikes: IRO Mark V, Karate Monkey half fat, Trek 620 IGH, Cannondale 26/24 MTB, Amp Research B3, and more.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Likes: 0
Liked 42 Times
in
18 Posts
jim
__________________
Cross Check Nexus7, IRO Mark V, Trek 620 Nexus7, Karate Monkey half fat, IRO Model 19 fixed, Amp Research B3, Surly 1x1 half fat fixed, and more...
--------------------------
SB forever
Cross Check Nexus7, IRO Mark V, Trek 620 Nexus7, Karate Monkey half fat, IRO Model 19 fixed, Amp Research B3, Surly 1x1 half fat fixed, and more...
--------------------------
SB forever
