pstock

I got a Trek 420 recently.
not modern but not ancient either .
oddly the front brake bridge takes a recessed Allen nut (RAN) while the rear bridge does not. It seems to not take RAN but rather an exposed nut.
the front fork is original.

Why would that be?
seems odd given brake sets would come (I would think) as either RAN or exposed nut.

maddog34

the fork is most likely a replacement one.
according to the list on Vintage Trek, your frame is most likely a '89...

https://vintage-trek.com/model_numbers1.htm

there are several resources to identify your trek.
here is a cool group on FB.. LOTS of very knowledgable fellow trek owners... including some very famous ones.
Vintage Trek Bicycles
https://www.facebook.com/groups/120288977723

well biked

Also, the fork crown might have been drilled on the back side at some point in the bike's life to allow for a recessed nut and more ( modern) brake choices. The brake bridge is much more difficult to drill because of the tight space between the seat tube and the brake bridge.

pstock

No, the fork is original.

well biked

The fork crown was likely drilled out to allow for a recessed nut. Again, much more difficult regarding the rear brake because of limited space between the seat tube and brake bridge. As a result, lots of older bikes end up with a fork that will accept a recessed nut, and a rear brake bridge that won't.

79pmooney

Much more fun speculation - the brake manufacturer had surplus older rear brakes. Sold mixed sets to Trek as a deal. No sweat for Trek to build accordingly. But the later drilling of the fork is far more likely.

maddog34

ahh, thanks for the pics... your bike is a "Resto-mod" incorporating more modern parts.

cool.

https://vintage-trek.com/images/trek/...Trek89_420.jpg

FBinNY 

The OP has to consider the possibility that someone along the way modified the fork, but not the rear bridge.

That's a real possibility because the fork easy, but the rear is near impossible without a precise tools.

dedhed

I dunno, I did it on a '87 400 and a couple others pretty easily and quickly with a short drill in a small vise grips. Doesn't need super precision and not tons of material to remove.

pstock

I got it setup like the pictures. complete overkill with 10S Dura Ace 7800 groupset
I have parted that out and will rebuild it with something more modest.

icemilkcoffee 

Ha! even the catalog pic shows recessed nut in the front and exposed nut in the rear!

maddog34

HA! Who cares?

Do you feel somehow superior that you were able to look at additional information PROVIDED BY ME, and deduce that i didn't have that information when i originally Replied?
Does your reply help anyone except you?

If your only purpose in a reply is to fail at making someone else look bad... DON'T BOTHER REPLYING.
SMH.

maddog34

Shimano 600 arabesque is popular as a group, and holds value well too.
Tri-color 600 is probably a closer fit to the age of the frame, and also holds value well.

and thanks for the pic earlier, it let us fellow Trek owners more closely pin down the age of your new bike. the paint looks nice even! It's the same color as my '82 930 custom. The "metallic" adds a rainbow of tiny reflections in the sunlight......not sure what paint was used on yours, mine is coated with Dupont Imron, now banned due to the nasty fumes emitted During Painting.... Imron is nearly as tough as Powder coat paints.

you'll find many more Trek owners/lovers on the FB page i mentioned... and a wealth of info too. join up and post your bike.

icemilkcoffee 

Huh? Where did that come from? What on earth made you think I was trying to ‘make you look bad’ or make myself look superior?
I was merely reacting to the fact that the bike came out of the factory with recessed nut in front and exposed nut in the rear.

maddog34

"ha!" a comment preceding a pointless proclamation.

icemilkcoffee 

'Ha!' is like 'A-ha!'. As in amazement. Not an insult on anyone. Whether the proclamation was 'pointless' or not- it wasn't any kind of insult on you, nor was it an insult on your mother or your wife or your religion , etc, etc, OK? Chill.

Trakhak

His "ha!" seems to have meant the same as "Wow!" --- i.e., "Turns out that, instead of surreptitiously shipping the bikes with mismatched recessed and non-recessed brake bolts and hoping no one would notice, they actually showed them in the catalog that way, loud and proud!!"

At least, I didn't see any connection whatsoever between your earlier post and the one you objected to. If it did reference your post, if obliquely, I'd have read it as meaning "maddog34 was right."

maddog34

not needing to "chill". HA!

the amount of non-post-related back and forth B S is getting to be too high. I have recently watched two responders argue points not related to the Subject for DAYS, never once helping anyone except themselves, i guess.
and now you're attacking Trek, btw... one of the few Companies that actually warranty their products,and recently recalled a large number of ANOTHER COMPANY'S Badly designed parts, at Trek's expense. Trek took heat for their Diligence and charity... I'm not remembering even one negative comment about JOYTECH during that period.

sorry i mistook your chit chat as an attack, but it sure looked like one to me, whether it was directed at me or not.
If no one had ever spoken up, we'd still be riding around in cars with no seat belts, horns, radial tires, Shock absorbers, hydraulic brakes, and defective suspension componennts.... see: Nissan recalls cars for defective "Steering wheels"... a mis-identification by Ignorant Media writers, BTW... it is defective TIE ROD ENDS that are being replaced, NOT "steering wheels that may break"). The defective tie rod ends were NOT made by Nissan, but i've already heard trash talk about Nissan.

i choose to speak up instead of "chill". It's in my nature.
your comment was not helpful.

maddog34

odd, because i wasn't right or wrong.about the non-issue.

the colors of the bike led to the bike's specs being found and reported to the owner....which then prompted icemilkCoffee to post the pointless poke at Trek, etc.

I think this dead horse has been flogged.
i'm out.

have fun.

Iride01 

Front brake bridge? You mean the fork crown? The pic is the rear brake bridge.

All the bikes I ever had used a recessed nut or barrel nut on the front since it had to go through the fork crown that was at least a inch and a half or so. And the rear just used a normal external nut since the rear brake was being mounted on something a half inch or less in thickness. Because bikes are different, that's why Shimano gives you a butt load of different nuts when you buy a brake set from them. Or at least they use to.

FBinNY 

So may I assume you're Gen-X or younger?

FWIW both front and rear brakes were mounted with through bolts and rear nuts through the early seventies (or so), when recessed hex nuts were introduced.

Both brakes changed at the same time, though an OEM might have mixed mounts, possibly owing to left over fork crowns or rear bridges.

Iride01 

No I'm a boomer.

I do remember my cheaper bikes having just a long threaded rod or bolt and external nut on the front. But while I might be wrong, I remember my early to mid 70's Schwinn Suburban as not having the external nut for the front brake. Actually remembering it as a stud that didn't go all the way through the crown, but again, I might just be delusional and delirious. I don't remember seeing a external nut on my '79 Varsity either. And likewise my '91 Paramount frame that I got circa 2016 seemed to want the recessed allen nut.

Still the OP seems to wonder why stuff made today doesn't quite match what was made many years ago. And since the front and back are being bolted to something of a vastly different size, I wouldn't expect the fasteners to be the same. If the recessed nut doesn't fit the hole in the rear of the fork crown, it's not a major issue to simply drill the rear hole to the correct size.

JohnDThompson 

Recessed mount in the front and exposed nut in the rear allows using the same length caliper mounting bolt for front and rear; one fewer part to stock.

SurferRosa

I can't tell you how many vintage road bikes I've had like this with their original group. Especially mid-level Univegas!

Also, the nutted rear allows you to easily mount a rack using that bolt to secure it. Pretty handy for a sports tourer, but doesn't quite look right for a racing bike, especially as you get deeper into the '80s.