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Old 08-05-10, 08:11 PM   #1
Bubu
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Problem finding screw size equivalence for lowrider brazon screw

I went to the store to get some longer screws for my lowrider rack because the ones that came with the rack are too small for the thread in the fork and the ones on the bike aren't long enough since the rack is probably made for newer/larger touring forks and I have no place for spacers with the short screws. I came to a conclusion that the screws seems to be sized 1/4 x 32 and I want them in 1 1/2 lenght. All the 1/4 screws I find are 20 tpi threaded, I can't find 32 tpi threads. Is there a metric equivalent I should look for? The #10's are too small, they only fit in the lower brazon.

My bike is a 1990 Miyata 1000LT if it helps.
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Old 08-05-10, 08:42 PM   #2
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1/4" - 28tpi would be the fine thread for quarter inch. 1/4-20 is standard coarse thread for 1/4". If you have a Miyata, I suspect you have size M5 fender and water bottle mounts I would think. A good investment would be in both a standard (imperial) and metric thread gauge. When you find an exact match for your threads It saves you a lot of time and eliminates all doubt.
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Old 08-05-10, 08:45 PM   #3
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The standard braze-ons are threaded to accept M5X.80 metric screws. They are commonly availbile in 10, 12, 16, & 20mm lengths. 1-1/2" or 36mm seems pretty long and might not be able to take the stress of a loaded rack. (I know that 1-1/2" is not not 36 mm but this is probably the closest size available)
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Old 08-05-10, 09:53 PM   #4
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Quote:
Originally Posted by masi61 View Post
1/4" - 28tpi would be the fine thread for quarter inch. 1/4-20 is standard coarse thread for 1/4". If you have a Miyata, I suspect you have size M5 fender and water bottle mounts I would think. A good investment would be in both a standard (imperial) and metric thread gauge. When you find an exact match for your threads It saves you a lot of time and eliminates all doubt.
Oh, maybe it's 28 tpi, I saw no screws at all with that tpi at the store... And yes, for the bottle and fenders mounts it seems to be M5 as I've been told but the middle lowrider mounts have bigger screws than the other ones on the bike. That's the problem! The screws that came with the rack are ok for the rest of the brazons but too small for the lowrider brazons on the front fork.

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The standard braze-ons are threaded to accept M5X.80 metric screws. They are commonly availbile in 10, 12, 16, & 20mm lengths. 1-1/2" or 36mm seems pretty long and might not be able to take the stress of a loaded rack. (I know that 1-1/2" is not not 36 mm but this is probably the closest size available)
I may not need that long but to get everything parallel and leave enough space for pannier hooks and also to get the screw in the furthest possible I measured close to that. So that's , in order, the lowrider frame, a couple spacers and finally the fork whole fork brazon (or should it be braze-in? hmmm...) Maybe I could bend the stabilization bar on the lowrider rack to get it closer and need less spacers on the fork but I was trying not to play with that.
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Old 08-05-10, 10:05 PM   #5
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If they're bigger than M5, they're probably M6x1.0. Bring an existing too-short screw into a well-stocked hardware store. Where the fastener bins are, there should be a couple of displays with actual studs and nuts of all common sizes, metric and "SAE" mounted on bases, used for finding the right fastener.

I don't think I've ever seen an inch-fractional braze-on on a bike made since disco sucked. I'm sure there's one out there, though....
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Old 08-05-10, 10:48 PM   #6
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Maybe some pictures will tell the story a little better about the spacing problem and the difference between the 2 types of screws.



I tried the bigger screw in 1/4 test base at the store and it seemed to be the right size but it wouldn't thread in correctly for 20tpi. And in another 1/4 test base, with closer threading, it was loose. I'll try and find a store with metric test bases, I hope I find one. The thread is definitely not the same as the other screw is one thing I can see.







The lowrider rack is rated for only 20 pounds so I won't be overcharging in the front, it's just there to even the weight a little for my first tour (4-5 days on the bike at most), kind of a test tour for me, the bike and the equipment.

Last edited by Bubu; 08-05-10 at 10:52 PM.
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Old 08-05-10, 11:30 PM   #7
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If they're bigger than M5, they're probably M6x1.0. Bring an existing too-short screw into a well-stocked hardware store. Where the fastener bins are, there should be a couple of displays with actual studs and nuts of all common sizes, metric and "SAE" mounted on bases, used for finding the right fastener.

I don't think I've ever seen an inch-fractional braze-on on a bike made since disco sucked. I'm sure there's one out there, though....
+1000... about disco.

The braze-ons are certainly M5 x 0.8mm. My local hardware store stocks these in lengths from 6mm to 30mm; in standard head, hex head, and button-head hex; black and stainless steel.
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Old 08-05-10, 11:40 PM   #8
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just make sure the boss is actually threaded. Quite a few older lowrider bosses were unthreaded, just hollow tubes thorough the fork. If this is the case, use an M5 bolt, with a nut on the inside.
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Old 08-06-10, 12:06 AM   #9
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As you can see in the pictures one bolt is M5 (i'm almost certain), the other shorter one is bigger with a different thread (original from the bike), I suspect M6 like madpogue suggested. The bosses are threaded and it's the reason why I don't want to use a smaller bolt and a nut.
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Old 08-06-10, 12:15 AM   #10
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Given just one view offered, Looks like a thru the fork tube, and if it's not threaded ,

Expectation is .. it's Metric, [Napoleon's system, used around the world] predominate in bike hardware.

and same size as a water bottle boss .. But longer , goes all the way thru then you put a nut on the other side..
5mm, Thread Pitch .. 0.8 thread per mm is standard.

get a long bolt and spacers [or a whole bunch of flatwashers] so you will keep the planes of the pannier carrier as wide as it is in the picture.. IE, which is as wide as the mounting to the hoop in front.....
they made a hoopless rack it braces to both sides of the fork, sold many as such ..
but It's only a guess, as I am not offered adequate alternate views..

Last edited by fietsbob; 08-08-10 at 10:04 PM.
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Old 08-06-10, 12:21 AM   #11
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Look at the picture a couple of posts higher, you'll see the difference between the fender/bottle screw and the other one which goes in my lowrider brazon in the middle of the fork. Both fit in their respective brazon and aren't the same.
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Old 08-06-10, 12:47 AM   #12
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Just so we're on the same page - the too-short, bigger screw DOES thread into the braze-on by itself, it's just too short for the rack rod, right?

And indeed, since 6mm is very close to 1/4", an M6 will seem to start to thread into a 1/4-20, but will stop, just as you experienced at the hardware.
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Old 08-06-10, 12:51 AM   #13
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as a pass thru scheme, #10- 32 would work , get a high quality machine screw, 8.8 are tempered steel.
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Old 08-06-10, 07:44 AM   #14
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Originally Posted by madpogue View Post
Just so we're on the same page - the too-short, bigger screw DOES thread into the braze-on by itself, it's just too short for the rack rod, right?

And indeed, since 6mm is very close to 1/4", an M6 will seem to start to thread into a 1/4-20, but will stop, just as you experienced at the hardware.
Yes, that's it, it's too short to give me clearance for pannier hooks and makes the whole rack twisted if there are no spacers. Thanks alot for the info on the M6, it's probably that size and I'll look for that before anything else.
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Old 08-06-10, 08:35 AM   #15
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My 1991 Miyata 1000 uses an M6 bolt in that location.
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Old 08-06-10, 02:01 PM   #16
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as a pass thru scheme, #10- 32 would work , get a high quality machine screw, 8.8 are tempered steel.
Thinkin' it through, "pass-through" won't work. These are the braze-ons midway up the fork blade. They're not "edge-on" to the fork like the dropout or seat-stay braze-ons are; the threaded hole leads right into the inside hollow of the blade.
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Old 08-08-10, 12:08 AM   #17
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It was an M6 bolt! Thanks for all your advice, I found some steel ones and they will get some stainless steel and call me when it's delivered. The rack mounts in a better alignment now (with aluminum/rubber spacers) and it will be OK for my tour and I will change for stainless later.

Thanks again!
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Old 08-08-10, 10:41 AM   #18
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Eighteen posts to arrive at the obvious conclusion that an M6 bolt is required. I hope none of you are professional mechanics.
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Old 08-08-10, 11:52 AM   #19
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Eighteen posts to arrive at the obvious conclusion that an M6 bolt is required. I hope none of you are professional mechanics.
> 9000 posts and none worth reading. Hope you're not pretending to be helpful.
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Old 08-08-10, 01:53 PM   #20
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> 9000 posts and none worth reading. Hope you're not pretending to be helpful.
Bingo; if it were so "obvious", what stopped GB from posting right away? And no, it DIDN'T take "18 posts"; I suggested M6 in post 5. I just forgot to be snide and surly about it... Gotta love "Sunday morning quarterbacks".
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Old 08-08-10, 09:51 PM   #21
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For a number of years the manufacturers also brazed a tube straight thru the fork blade, in one side and out the other ,
no threads were cut, it was a way to bolt a rack with out a hoop. the sleeve was in compression between the 2 parts of the rack.

That style fork braze thru, Uses this kind of front rack:

http://tubus.com/en/lowrider/duo

Just One picture was not making things as clear as if it were right in front of me.
It was my guess that was the other end of such a tube on the inside of the fork blade that I saw.

Ex c UUUUUse me..

Last edited by fietsbob; 08-08-10 at 10:01 PM.
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Old 08-08-10, 10:19 PM   #22
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Bingo; if it were so "obvious", what stopped GB from posting right away? And no, it DIDN'T take "18 posts"; I suggested M6 in post 5. I just forgot to be snide and surly about it... Gotta love "Sunday morning quarterbacks".
If your not snide and surly then who's going to take you seriously?
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