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Trek 750: Upgrading component questions

Old 08-30-22, 10:05 PM
  #1  
Matafuna
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Trek 750: Upgrading component questions

Greetings,
I picked up a 97 Trek 750 the other day and want to convert it for a gravel bike for a race my wife and I are tackling in the Lost Sierras next year.
The gears and teeth are pretty worn and "fin" like so I was looking to replace the front crankset and rear cassette and upgrade the derailleurs if needed. Currently the bike has Shimano STX components.
I'm not looking to do a 1x as I'm pretty happy with the current gearing. Would I be able to use a Sram S600 (42,32,22) or similar?
I am also going to need some drop 3x7 brifters. I read in another post that Shimano Sora ST3300 shifters would work but I wanted to see what others are using.

Here's the 750.

Thanks for any help!
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Old 08-30-22, 11:11 PM
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Nice lookin' ride. Good luck with the build.
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Old 08-30-22, 11:19 PM
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The new crankset may need a bottom bracket with a different spindle length. If you are changing the bottom bracket and crankset you may consider upgrading to external bearings/2-piece crankset. Shimano FC-MT210, T4060 or similar.

If you are converting to brifters/drop bars and replacing the whole drivetrain you can also rebuild the wheel with a different hub/get a new rear wheel and go 8 or 9 speed. The choice of 7 speed cassettes is not great. I really liked the 13-28 one, but Shimano stopped making it and most of the other ones. More choices if you go 9 speed.

I run Sora 3500 brifters with a 105 FD-5504 front derailleur, Microshift M46 rear derailleur, Shimano HG50 11-30 cassette and 48-36-22 Shimano FC-M590 triple crankset on my bike.
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Old 08-31-22, 07:02 AM
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Show Your Vintage MTB Drop Bar Conversions
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Old 08-31-22, 10:53 AM
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Thanks for the specs csport. I"ll research those options. I'd rather not throw a new rear wheel into the mix if I can find a lightly used HG-50 but availability looks limited.
I"m also not sure what size tires I can get on these rims but if I can't fit at least 40's I may go that route. What drops are you using?

Dedhed- Thanks for the link. Yeah, I've started reading that thread already and I'm about 5/300th of the way thru Great info though.
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Old 08-31-22, 11:02 AM
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The factory Matrix Vapor rims are, if I recall correctly, 15mm wide internally. I've had as wide as 40mm tires on my '97 750 and they worked very well. With a tire that much wider than the rim, you start to have concerns with getting brakes to open wide enough to clear the tire when adjusted correctly for the rim width, so I don't think I'd go much wider than 40mm for that reason alone.
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Old 08-31-22, 12:15 PM
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My understanding is that the STX groupset is a MTB groupset and as such the FD is not compatible with road brifters.
If you want to stick with a 3X7 drivetrain, you can look for a RSX triple crankset and RSX FD. In addition to the RSX and ST3300 brifters, another choice for 7 speeds is the Microshift R7 brifters.
As for wheels, if it was me I would change out the rims to tubeless ready rims. For wide tires with low pressure, tubeless is best.
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Old 08-31-22, 12:28 PM
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Originally Posted by Matafuna View Post
Thanks for the specs csport. I"ll research those options. I'd rather not throw a new rear wheel into the mix if I can find a lightly used HG-50 but availability looks limited.
Do you mean a 7 speed HG50 cassette? Those were discontinued several years ago. There are ones like 12-28, 11-28, 12-32, 11-34.

I was trying to say that if you get 7 speed brifters you are locked into 7s which is dead. Replacing/rebuilding the wheel with a wider hub will let you go 8-11 speed (11 speed with a MTB cassette).

Another solution is to upgrade to 9 or 10 speed and run 8 of 9 or 9 of 10 on 7 using the current wheel: https://www.sheldonbrown.com/k7.html (you have a 7s cassette hub, not a freewheel, right?)
At some later point you can get a new wheel and run the full cassette.
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Old 08-31-22, 01:14 PM
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Understand that the spacing between chainrings is wider from road to MTB. And while you can get flat-bar shifters that work with road derailleurs, you can't get a left STI lever that will work with an MTB derailleur. And road brake levers don't pull enough cable to effectively actuate linear-pull brakes. But for the go part, if the rear axle spacing is 130 mm, I'd recommend a full Claris 8-speed kit. 8-speed freewheels are still available. But I don't have a solution for the stop part.

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Old 08-31-22, 01:51 PM
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csport- I have the freehub with cassette. (Shimano FH-R050 silent clutch) which according to the homework you graciously sent me (Sheldon Brown) means I could swap in a 9 sprocket cassette for the time being. Cool, I didn't realize that. I know you're running Microshift and Shimano deraileurs with Sora brifters so I guess compatibility isn't an issue?

hokyfied- I don't plan on going larger than 40 on the rims so that should work. I read once that you had issues with the beading on these Matrix Vapors.. any particular brands you liked that had better fitment?
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Old 08-31-22, 02:17 PM
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Originally Posted by Matafuna View Post
csport- I have the freehub with cassette. (Shimano FH-R050 silent clutch) which according to the homework you graciously sent me (Sheldon Brown) means I could swap in a 9 sprocket cassette for the time being. Cool, I didn't realize that. I know you're running Microshift and Shimano deraileurs with Sora brifters so I guess compatibility isn't an issue?
Up to 9 speed speed almost all (I think except for some old Dura Ace) Shimano rear derailleurs use the same pull ratio. Microshift M46 is Shimano compatible "mountain", it works with road shifters, it should work with the new Sora 3000 as well. Front derailleurs have different pull ratio, you probably have to use "road", my FD-5504 is old 105 (when 105 was 9 speed) road.

Freehub body for 7 speed cassettes is narrower, and it will not fit an 8-10 s cassette (unless you have an 8-10s freehub body with a spacer - most likely this is not the case). You can remove one cog from a 9s cassette and mount it on the 7s freehub you have, the article I linked has a section named "8 Of 9 On 7 -- or 9 of 10 on 7" near the end. You will need 9s shifters, and with this setup one shifter position will be not usable. If you ever get a wheel with a full 8-10s freehub and mount a full 9s cassette you will be able to use all shifter positions.
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Old 08-31-22, 02:41 PM
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Thanks for the lengthy explanation csport. I'm still wrapping my head around these conversions between road and MTB and this really helps a lot.

We're packing up the Airstream today and heading up to the Gorge to see DMB so I'll have to report back once we return and I have some time to finish this build.

Thanks again everyone.
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Old 08-31-22, 10:07 PM
  #13  
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Originally Posted by Matafuna View Post
csport- I have the freehub with cassette. (Shimano FH-R050 silent clutch) ....
Finding an 8-10 speed FH body for your hub would be quite the task and probably prohibitively expensive if you found one.
I included the exploded view of your hub, the 8 speed version of the same hub, an "old style" 7 speed hub and one of the semi newer 8 speed hubs.
Your hub is "the odd man out" compared to the last 2 docs (and beyond)
You can see how the FH bodies attach very differently on your type vs the 2 other types. I'm NOT up on the latest stuff, so it probably gets worse with all the different diameter through axles etc.

Anyway, study the docs and I think you'll find them somewhat informative.
You could have a new hub installed on your current rim. Spokes should work lengthwise. The wheelbuilder may not want to use used spokes. Frequently the threads are so corroded, you simply can't get a good feel on tension which results in frustration and a less than good job. Think of having to twist a spoke a 1/3 of a turn before the nipple releases. I'm too old and cranky to not use new spokes & nipples. It makes it MUCH easier to build a "good" wheel with nice even tensions.

What's the drop out spacing?
Attached Files
File Type: pdf
FH-R050.PDF (266.6 KB, 0 views)
File Type: pdf
FH-R080.PDF (263.6 KB, 0 views)
File Type: pdf
FH-M290-95.PDF (522.2 KB, 0 views)
File Type: pdf
FH-RM30-8S.PDF (299.2 KB, 0 views)
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Old 09-01-22, 07:01 AM
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Spacing on this bike is 135mm.

Regarding tires, yes, I have had trouble finding ones that "fit nicely" on these wheels. I've been happy with Continental Speed Rides (those are the 40mm tires I referenced earlier). They're labeled "700x42", but they inflate up to about 39-40mm on those rims.
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Old 09-01-22, 07:40 AM
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Matafuna A number folks are mentioning that the your existing front derailleur won't be compatible with road shifters. Why not universally true (I have a '93 XT FD running happily with a 3x Tourney shifter), it is true most of the time. You can use your mtn/trekking FD with road shifters if you install a Shiftmate. Works fine.. (I'm surprised this isn't more well-known as it's an easy work-around)

Jtek ShiftMate Gear Shifting Adapter for Shimano Campagnolo and SRAM components

As for brakes.. install a set of cantilever brakes..they play well with road shifters and are easier to run with wider tires. There's lots of vintage stuff around, or pick up a set of Tektro CR510s or CR720s. Cap them off with Koolstop pads and you're good to go.
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Old 09-01-22, 07:46 PM
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Originally Posted by Matafuna View Post
Greetings,
I picked up a 97 Trek 750 the other day and want to convert it for a gravel bike for a race my wife and I are tackling in the Lost Sierras next year.
The gears and teeth are pretty worn and "fin" like so I was looking to replace the front crankset and rear cassette and upgrade the derailleurs if needed. Currently the bike has Shimano STX components.
I'm not looking to do a 1x as I'm pretty happy with the current gearing. Would I be able to use a Sram S600 (42,32,22) or similar?
I am also going to need some drop 3x7 brifters. I read in another post that Shimano Sora ST3300 shifters would work but I wanted to see what others are using.

Here's the 750.

Thanks for any help!
I have a 94 that I built up, the frame is 135mm but steel so road wheels fit fine; new wheels add a lot of flexibilty, and machined brake tracks. I went Sora 9sp because I had a bunch of 8sp era parts. Front derailleur is a Ultegra 6800, XT 11-34 cassette, Deore 24/34 crank, TRP mini Vs, tires are Conti SpeedRide.



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Old 09-01-22, 07:52 PM
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You could find a set of 7 speed indexing bar ends (rather than brifters) and keep your existing derailleurs. That's what I'm going to do with a '93 Trek 750 I picked up recently. I wouldn't be so quick to change out parts if they are still serviceable but I like reusing parts. YMMV.

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Old 09-02-22, 09:50 AM
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Nice bike. I'd love to pick one up someday.

Originally Posted by Matafuna View Post
I am also going to need some drop 3x7 brifters. I read in another post that Shimano Sora ST3300 shifters would work but I wanted to see what others are using.
I prefer a friction shifter for the FD on a triple, but I had a '96 Specialized Allez for a few years with Shimano RSX 3x7 brifters. They worked very well once cleaned and lubricated.
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