kokomo61

After I got a decent road and commuter bike, I came up with this wild idea to upgrade my Trek 7300 hybrid into a fast flat-bar road bike (with the exception of some head-tube height, it's identical to the FX geometry).

Well, the combination of being a noob and initial excitement has gotten me into kind of a bind. I've bought things that don't work - Front DR (too small of a band clamp), crankset (outer chain ring is too big for the drive train - it's a 52/39/30 - max for the Shimano flat bar setup is 50T)

I also bought different shifters than I wanted, but I put those back on eBay.

Here's my question - is there a 50T Shimano outer chain ring that I can swap with the 52T? There's a 10SP compatible one that's 50T, but I don't want to buy ANOTHER thing that doesn't fit......at this point, the bike isn't really rideable, because it's still got the old SRAM X series RD, the 11-32 cassette, and the old front DR (with the new crankset). Am I in over my head, and should get a REAL mechanic to set it up properly, or can I (slowly) dig my way out of it?

Here's what it's SUPPOSED to have when I'm done:

Shifters: Shimano R-660 flatbar shifters
Crankset: 105-series triple (50/39/30) - it's currently a 52/39/30
FR - Shimano FD-R453B (9-sp, compatible with the R-660's)
RD - Shimano Ultegra long-cage (9-sp compatible)
Cassette - Shimano 105 12-25
Wheels - Shimano WH-R550

Right now, my sticking point is the outer chainring. If I keep making mistakes, it will have been cheaper to buy a new 7.3 FX.

Sheldon Brown

I don't understand what the problem is with the 52 you already have...? I would have expected this to work just fine...

Sheldon "Puzzled" Brown

operator

If you don't HAVE to have a 50t chainring upfront, there are plent of choices < 50t. What exactly is limiting you to 50t? The derailleur? This doesn't make sense.

jaxgtr

I am looking at the same issue, I have to replace my crank on my 7300 and don't want to have to replace the whole drive train. I live in ultra-flat Florida so I moved to a 12-23 8 spd cassette 9 months ago and would just like to find a crank\BB that will work not requiring new shifters, fd and rd. I've seen 48T Bontrager Select for Hybrids which seems like it will work, but no one has it in stock so I can look at it. I'm not looking to spend any serious cash, just something that will make the bike go forward

I_bRAD

The derailleur is getting replaced anyhow 'cause the clamp is too small.

oldokie

In the end, you may spend more than you planned and still not have that fast flat bar bike you were expecting. I had a similar notion with a 7500 but decided to sell and do it right (buy a decent road bike). Even after you swap out components, your bike will still be heavier than a road bike and you will still be unhappy. Your suspension front fork alone weighs a bunch and your tires will still be heavy compared to a road bike.

jaxgtr

I replaced my fork with a rigid but want to keep the bike. I use it for interval training cause it is heavy. I live in flat Florida and this helps me with my leg strength as I ride over bridges.

kokomo61

Thanks for all the replies so far.......here's some more info:

The 50T size is dictated by....the front derailleur....which is dictated by....the shifters.


The Shimano R-660 shifters are compatible with the 443/453 series front derailleurs, which have a 50T limitation (at least according to Shimano). Because I jumped in without a lot of knowledge, I didn't know that my 52/39/30 was too big. Hopefully I can swap the outer chain ring....that was my first question to start.

I also have to get a front derailleur that is compatible with the shifters, AND fits around the seat tube. I think that's the 34.9 453 FD from Shimano.

If I can solve the drive train issues and get that part set up, it should work out, but right now, I'm thinking that I should just take it to a qualified mechanic and have them set it up. I'd like to get better at working on the bike, but I keep hitting dead ends and making mistakes, and it's getting frustrating.

As far as weight, etc...I've already swapped the suspension fork for a rigid steel fork, and have converted it over to a threadless headset, flat bars and axed the suspension seat post. I've also got new road wheels/tires that are a lot lighter than the stock Bontrager rims/tires.

I have two light (real) road bikes, and my commuter, so I'm not trying to turn this into a full-blown road bike - I just want to make it into a faster casual bike with better components than what it came with.....but it's getting to be an expensive lesson.....

kokomo61

This is a little weird....The Shimano web site says that the R-440 shifters (and 660's too) are compatible with the 440/443/453 series derailleurs, and can use a maximum chain ring size of 50T (for the triple).

This BD bike has a setup almost exactly what I'm trying to do with the Trek, but it has a 52/42/30 front CR. Who's wrong? Shimano or BD? (I pretty much know that I'm wrong at this point)....

BD Bike specs

Shimano 453 FD specs

Sheldon Brown

Actually all Shimano flat-bar shifters are compatible with that excellent front derailer.

I'm guessing you haven't actually tried this, just given up on the basis of Shimano's marketing materials. Big ring size is important in choosing a front derailer, but I've never known a mismatch as small as two teeth to be a problem in practice.

See: https://sheldonbrown.com/capacity

Sheldon "Imaginary Problem" Brown

kokomo61

Thanks, Sheldon - I guess what I'll do is this:

1) Get the proper size band clamp for my FD (The Trek hybrids have a fairly think aluminum post - would I go for the 34.9?)
2) Take the old shifters, wheels, chain, RD and FD off
3) Install the new shifters, RD, FD, chain and new rear wheel/cassette
4) See if I have any problems in shifting
5) If so, swap out the 52T for a 50T outer chainring (will the 105 50T 5600 chainring fit the 5503 crankset?)
6) If that doesn't work, take it to a real mechanic who'll bail me out of the mess I've created.....