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    Project Idea: Converting a 90s MTB Frame into a Budget Gravel Bike


    Last year I started getting into wrenching a bit—modding my fixie and restoring an old road bike—and lately I’ve been toying with the idea of a new project: converting a 90s GT MTB steel frame into a gravel bike. Yeah, I’m not the first one with an idea like that and somebody did sth similar to a green timberline over here.
    But maybe you can help me to find out if my plan could work. I’m also planning to keep the cost under 1000€. That also means: no Shimano or SRAM groupset.

    Here’s the current build plan:
    • Frame: GT Karakoram, Timberline (steel), or possibly a Terramoto (aluminum); frame size between 18”–20” – size is the part I’m most unsure about.
    • Fork: 1 1/8” flat mount gravel fork (probably carbon from AliExpress), A-C 400mm, 45mm offset, clearance for 650x50mm tires
    • Cockpit: New stem + drop bars
    • Drivetrain: Microshift Sword 1×10,
    • Bottom Bracket: BSA 68mm
    • Brakes: Mechanical flat mount disc, probably TRP Spyre C with 160mm rotors
    • Wheels: 650b, 12×100 / 12×142 thru axle, HG freehub

    About me:
    • Height: 184cm (6’0”), inseam: 87.5cm
    • Some wrenching experience (fixie mods, vintage road bike rebuild)
    • Fully aware that buying something used would be more logical—but again, this is about the fun of building something unique

    Questions:
    • Has anyone here done a similar retro-MTB-to-gravel conversion?
    • How do you figure out the right frame size when the geometry wasn’t meant for drop bars?
    • Does this plan look doable overall? Any red flags or things I should consider adjusting to make this work?

    Image is AI-generated and just for visualization.

    by Dismal_Suit_3971

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    50 Comments

    1. Thisisntalderaan on

      You lost me at carbon aliexpress fork

      That and drops, I think.

      You’re also not going to get 142mm thru axle wheels into a standard 135 (was this frame 135 by then?) dropout.

      Edit: and when did this bike become a disk brake frame? I just googled every other 1990s year of the karakoram frame and none of them were disc. Not a huge deal to do disc in front with a fork change, but that’s also assuming you can even find one in the first place.

      There are going to be a few differences between a 1990 and 1999 frame. I don’t know when it switched to 1 1/8″ headtubes.

    2. Papa_Canks on

      Just let your 90s mtb be the flat bar 26er gravel bike it was born to be and save up for a better 700c purpose-built gravel bike if you’re into it. 

    3. justokayatbikes on

      Neat idea and it has been attempted in many ways. There are fb and reddit groups which cover these types of conversions. Just a couple points, bb may be 73mm and you won’t be able to run rear thru axle. These frames predate that standard. Older models also ran canti brake so you’ll have to find a late model for disc tabs. 650×50 may or may not fit the rear triangle.

    4. Plasmodium0 on

      Many many people have done projects like this, just search back on the sub for advice on sizing etc, it’s a very frequently asked question. You’ll also find the usual warnings about the frames having too much reach, compatibility issues (eg, will that fork fit in a 90s MTB with a 1″ head tube, how will you run a rear TA disc wheel on a QR rim brake frame etc), geometry being messed up by wheel swaps etc.

      The biggest question I have to ask about this is, well, if you want a 650B drop bar bike with disc brakes, why are you starting with a 26″ flat bar bike with cantis? For €1000 you could go on ebay (or to Decathlon even) and pick something that already meets most of your specs and will be more rideable. I love tinkering, but it feels like you could pick something a lot closer to start with or alter your desired outcome to match the frame you’re set on.

      I don’t mean to come across as too negative, because with a lot of effort/money, you can overcome most of those issues, and the other guys on this sub are great at working around them and will probably suggest some good workarounds. I just wanted to play devil’s advocate a little bit, and warn you about the complexity! 🙂

    5. wstephenson on

      Yes, 2007 Zaskar-to-GRX, with shocks. Excel and trigonometry. Pics in my post history. The weakest parts of your plan are not knowing the frame size nor which stem or drop bars to use to achieve a comfortable stack and reach. Use your existing drop bar bikes as a template but try to go a tiny bit shorter and a bit higher.

      It sounds like you’re planning to use a fairly recent frame with discs – was there a late 90s steel GT with discs you could start with or are you planning to weld? Likewise thru axles – because you have 650b wheels? are you going to use a QR adapter on those?

      Check the BB shell width of your candidate frame. Aluminium GTs in the 90s were 73mm BB at least.

      Keep in mind that it will have a 71 degree angle to begin with and putting a longer fork on it might make it even slacker. This is noticeable in handling and in the “flop” feedback you get through the bars when steering through the neutral point.

      Also, I really wouldn’t use an AI generated image for visualization as it will just show you an idealized gravel bike with a triple triangle frame and a GT logo, whereas because you’re fighting say a 590mm top tube where a 560mm TT would be ideal, the bike will have to have a short stem and will look a bit hunched, nothing like the AI visualization.

    6. BlackberryOk602 on

      Not to be a downer but I think GT literally has the bike in the photo you posted as a real bike you can buy right now. I’d drop all the modern stuff, old triples have (arguably) more gear range than 1x drivetrains, disc brakes only an option if the frame has the mounts etc. just get a pair of comfortable swept back bars that are still off road capable and take it for a ride

    7. YEinherierY on

      As someone who kinda did this let me tell you: You can either do it right or budget. If you want the bike to perform like a modern bike, budget is not an option. If you go budget, a regular tuneup and a pair of low rolling resistance tires would make much more sense. I did it right but for the money I could have bought a nice, of the shelf gravelbike with better performance. Don’t get me wrong, I don’t regret it because I had an Idea and wanted it to come to life, but expect to research parts specs and compatibility sheets for hours and still buy parts multiple times because the specific frame you’re using has some unexpected 90s quirks.

      Edit: to answer some of your questions: If you want to fit a dropbar, figure out a flat bar size that works for you and go a size down from there. Keep in mind that the dropbar has added reach. A short reach dropbar would be the Ritchey Corralitos. I have no experience with Microshift. You can get original GRX derailleurs from AliX for fairly cheap and pair them with 105 brifters if you want to go with mechanical brakes. Don’t get brake discs from AliX, they are really bad or hit or miss at best. You can get original Shimano discs pretty cheap. The ZTTO hybrid calipers work pretty good on Shimano discs. Don’t buy cranks or bottom brackets from AliX. There are good ones there, but they are as expensive as cranks from reputable brands. Don’t buy chains from AliX. As far as I heard, ZTTO cassettes are pretty decent for the price, I went with Sunrace.

    9. Olderschoolwillie on

      Don’t do it, it won’t turn out as good as you think it will. If you want an old bike to be gravelly just stick some corner bars on it and keep everything else the same.

    10. McDoof on

      I tried this with my 1992 GT Karakoram and it never fit the way I imagined. Take the advice of the others here and use the GT as a mountain bike.

    11. bikinibottomrealest8 on

      Gt had 700c hybrids in the 90’s – arrette, cirque, vantara should all have that classic triple triangle look you’re probably after. Slipstream and airstream are also 700c I believe but with a funkier curved tubing cruiser look.

    12. ENTroPicGirl on

      https://preview.redd.it/q1kfhwqk1o8f1.jpeg?width=3024&format=pjpg&auto=webp&s=f1896108f86117ced2715bd81be3da64e599eb94

      Here’s my drop bar 26”

      Frame: 1999 Giant ATX 870

      Forks: Girvin 1” steer tube w/ 1”:1-1/8” adapter

      Headset: Orgin8 SSR 1-1/8”

      Drive Train:Bontrager Race Lite GXP crank 130 BCD Wolf Tooth 38t chainring Sunrace M993 11/50 9spd cassette Sunrace M900 derailleur Dura-Ace 10speed chain XpedoM-G do 3 pedal

      Cockpit: Salsa WoodChipper bars FUNN Equaliser stem Shimano 105 FlightDeck road shifter Salsa bar tape Tektro Cross bar levers

      Brakes: Tektro Onyx cantilevers Tektro saddle cable Kool Stop Salmon pads

      Saddle: Sella SMP “Strattos” saddle Thompson post

      Wheels: Mavic Crossland (Tubeless)

      Tyres: Front/Rear:26”x2.35 Bontrager XR3 (tubeless)

      I’m gonna be honest there’s really no advantage of this bike over any modern gravel bike, the only reason why I was able to build it is cause I worked at a bike shop and I was able to cobble together some of the coolest most Gucci old school parts and didn’t have to pay retail or anything at all. If you have the means to build a cool drop bar bike, be my guest, but don’t expect to be able to keep up with a modern bike. Be prepared to make carve outs in caveat for your drive train. I’m running a one by nine which is obviously very steep. Doesn’t have a lot of gears in between and the only way you can make a one by nine work like this is you need to use a 10 speed chain.

      If what you want is something it’s more mountain than road when it comes to your gravel bike look for a used karate monkey.

    13. ReallySmallWeenus on

      The biggest issue the bikes are set up flat bars, meaning they have long top tubes. When you put drops on them, it moves the bars even further forward, giving you far too aggressive of a position.

      Old mountain bikes are what would essentially be a flat bars gravel bike nowadays.

    14. Horror-Raisin-877 on

      Well, you’ve come to the right shop 🙂

      And GT’s are loved here.

      You can keep within your budget by not swapping out the drivetrain. 8-9 speed is easy to find and less expensive. You also don’t trigger the need to replace the rear wheel.

      If you were to swap the fork, then you could have a front disc, and rear rim. It’s been done.

    15. MacroCheese on

      One thing to consider is whether it’s worth it to convert to drop bars in the first place. There’s lots of good alt bars out there. I have VO Crazy Bars on my gravel tandem and love them. Other people make their own crazy bars with bolt on pieces. There are also Surly Corner Bars, and a whole suite of bars that can use MTB components but give the drop bar feel. I love my drop bar gravel bike (Kona Rove), but the more I ride the more I realize I generally like alt bars better than drop bars. Plus you can still use an old 3×8 drive train which will remain indestructible with tons of range.

    17. PreviousMarsupial820 on

      I have almost the exact color GT timberline frame with a set of Paul cantis on there I turned into a commuter-ish bike with 650b’s for my daughter, but I gotta run skinnier tires than I would prefer to fit the fork. I’ve had that frame for almost 30 years at this point so I didn’t want to get rid of it but it wasn’t really the best option looking back on it

    19. Pattern_Is_Movement on

      “project idea” taking the meme MTB of this sub, and doing literally the most popular thing on this sub with it….

    21. Radiant-Armadillo865 on

      I put short kranks 1x and nice fork just use it as a gravel bike drop bars for gravel is imho not interchangeable and is an industry creation to sell more bikes

    23. catsandboobs24 on

      Let’s assume you keep the frame, seatpost, saddle…. That seems about it.

      No way you’re under $1000 unless you go for used parts, or new parts so cheap you’d have been better off with an original bike from the 90s anyway. If you’re dying to build a bike it sounds like a fun project.

    25. atxac on

      2000s era CX bikes make way better gravel bikes and can be found just as cheap. My gravel bike is a Traitor Ruben that originally had 700×32 tires. Swapped to 650×42 and I think it could even fit 650×48 slicks.

    27. _Vicker_ on

      https://preview.redd.it/5e7jtcsgmo8f1.jpeg?width=4800&format=pjpg&auto=webp&s=c74b226462fe000ea9880bd079d4a0a07756ed9b

      I agree with everyone here in saying that I wouldn’t recommend it for you. You can’t really build what you’re looking for for a reasonable budget.

      This was my 1993 Karakoram build, total build cost was over $1500 and that’s with me doing most of the work myself, getting great deals on parts and having a plan laid out. Rode nice and I loved the look but ended up selling it after 6 months cuz i just couldn’t get used to riding drops.

    28. phyx726 on

      No one says you have to ride on gravel in drops. Put a pair of sweet moth bars or something on it and you might have a better time.

    29. schheff on

      I have done this exact conversion with this exact bike that you have in the picture.

      I rode it for one summer and then took it apart because it was weird to ride and uncomfortable.

      I recommend against the conversion but you do you!

    30. Far-Resource3365 on

      I got an old German mtb bike from family friend for around 25$, changed everything but frame and fork, with surly corner bar just to get back to flatbar and having fun. Also have Specialized Crossroads that I installed dropbars and I miss my Ritchey Kyote Classic look and feel.

      Drop bars are cute but not only the right solution

    31. 8ringer on

      Answers: Yes. I didn’t, I had a 18” Rockhopper already so that’s what I used. Sure but why are you getting a new fork? Red flags are planning on “converting” to disc brakes on a 90s bike.

      Seriously, your plan is fine but ditch the disc brake idea unless you know a frame builder or can braze. Rim brakes are honestly just fine, people rode with them on all sorts of gnarly terrain for a century. I have CX-50 calipers on my Rockhopper and they’re honestly really really good. The hydraulic GRX on my Lynskey feel a lot better to pull but they don’t really stop any faster than my CX-50s when I’m getting on them.

      Building something unique is a perfectly good reason to do this, so go for it!

    32. metmerc on

      If you want to build up a budget gravel bike then I posit that a better starting point is an XC hardtail from around 2010. You can find these built around 29 inch wheels; they have disc brake mounts; and they’re not quite as long. They just fit a bit better, IMO. You can swap in 700c on the stock rims in many cases or just run slick 29″ tires. You can replace the 100mm suspension fork with a suspension-corrected rigid fork. You can run drop bars or alt bars (my personal preference). And then you’re good to go.

      The biggest drawback is that they tend to be aluminum frames. For that reason, I’ve tried to build up a couple of different 90s MTBs as some sort of gravel-type bike, but I just keep going back to my 2010 Access. I ride it and everything just feels right.

    33. Choice_Student4910 on

      https://preview.redd.it/1vxflpj5to8f1.jpeg?width=3360&format=pjpg&auto=webp&s=e5f7df932ac37aa4b2ae5fcdbd1a928845ef3579

      1994 Stumpjumper FSR (full sus). Did this in 2021 and didn’t go crazy over budget. No disc brakes, just cantis. Frame and seatpost I think were the only parts retained for this build.

      I had the too long/too low reach issue. Fork steerer tube was too cut too short so replaced with a cheap eBay “Suntour” suspension fork. Cockpit is Velo Orange Happy Stem 90mm, drops are Salsa Cowchipper.

      Drivetrain and levers 1×10 Microshift Advent X.

      BB converted to Shimano hollowtech2. Crankset is no name Amazon 32t oval ring.

      Wheelset was pre-built from an online bike retailer. Can’t remember the brand but I remember they were only $90. Smoke and Dart tires were new reissues so I got them at a great sale for $40 for the pair.

      It rode like a Cadillac, just absorbing everything. It was old dog slow but it was fun. I also bought a new titanium gravel bike that rips but I just loved that stumpy, aka the Warthog.

      I sold it in 2023 along with all of my bikes in a downsized move. I think if you’re curious and you have the means then why not?

    34. bignose703 on

      I don’t know why you needed AI slop for visualization, this is more than half the bikes ever posted in Xbiking.

    35. DIYfu on

      Honestly, for that budget, just get a used gravel bike or take a look at the Canyon Endurace AllRoad.

    36. runescape_nuttah on

      I have 90s steel mtb that’s got drops and brifters, posted about it complaining it feels terrible.
      Yeah it looks cool IMO but it rides so badly, the geometry is so wrong.
      Flat bar is more fun as well!

    37. bancars69420 on

      Haven’t done a conversion, but I’ve done lots of my own builds. If you have a bike co-op or a shop that has used parts, you can save a lot of money sourcing stuff from there.

      Also, just go rim brake. It’ll save you A LOT of hassle and they’ll work fine, I promise. I race mtb and gravel with rim brake bikes in Georgia, USA (piedmont terrain, no high mountains) and I’ve never been lacking.

    38. IHaveACoolHat on

      https://preview.redd.it/li114qhizo8f1.jpeg?width=1290&format=pjpg&auto=webp&s=89333b8f7c3e7eec849f086499793a57c903f8fc

      You should totaly do it, but don’t spend 1k! You can be savvy and get used parts from local co-op’s or eBay. I built this GF X-caliber with Tiagra brifters and GRX rear derailleur, 2.2 racekings with some other odds and ends for ~ $400 including the bike. Is it kinda sketchy to ride? Yes! but it looks fucking sick and it’s perfect for its intended purpose: ripping around town on short (20-30mi) party pace bar crawls, dipping into some mellow singletrack and low speed cruises with my wife . I’m definitely not taking this on a tempo paced gravel ride but that’s not what it’s for! I’ve got other bikes for that.

    39. TripleH18 on

      This is a very common project. These bikes look super cool. And some of the early 80s bikes work better for this project because they had more Road Geometry.

      By the 90s top tubes were longer and the fit for drop bars is all fucked up.

      This is honestly a project that rides like shit unless you fin a Goldilocks frame.

      This is doubly true for folks who NEED disc brakes. Fun project when you’re keeping rim brakes but suddenly you trying to weld disc brake tabs on a fork never meant for it.

      I live in a very x biking culture city and I NEVER see people riding these conversions.

      These projects cost a bunch of money and never work out right. Buy a cheaper drop bar gravel bike and tinker on that instead. It’ll be cheaper in the long run and you may actually ride it!

    42. DropKickedCat on

      https://preview.redd.it/8pm7xts34p8f1.jpeg?width=4096&format=pjpg&auto=webp&s=f942ada59a590dd9f24e5db1e9541f7d1a57aea0

      This is not a GT frame (Surly 2003 1×1…with some brazing done for cable routing and hanger..and a bridge club fork)..I put Corner Bars on mine to keep the MTB components – but anything with 90s geo MTB will take some interesting stem considerations to make it work.

      It can be done. It’s fun. But remember it’s a passion project and you will probably never get the money out of it you put into it – but it will be distinctly yours and that can be priceless.

      [Here is what you are getting into. ](https://youtu.be/MGu2aYx8SS4?si=fAA_LfdTbwE80xT4)

    43. Miginath on

      I have attempted similar builds. A couple of considerations:

      1) Sizing. Typically people advice that you go down a size if you want to make a MTB into a Gravel bike. For you a Medium is potentially the right choice. Leads to a more modern fit.

      2) stem length and angle. You will probably need to get an steeper angled and shorter stem for the handlebar to get a comfortable fit.

      3) If you can’t salvage the parts its probably not worth it. While this sub is biased towards adding $2000 worth of parts to a $50 frame it might not be the right choice for you. If you can find parts for cheap that do it but don’t spend a lot of money on it. Your time is worth what you make it.

    44. FluffyEar1332 on

      You should do it, but stick with regular brakes and instead of drops you should go with the microshift advent 1×10 and put it on surly corner bars! Thats what im planning at least

    45. tomcatx2 on

      We need less ai slop.

      Are you planning to add flat disc tab mounts to your project bike?

    46. drgalindez on

      Hi, I have a 2008 outpost that I wanna mod for a similar gravel type build. I should probably make a separate post for this, but has anyone tried this with an outpost frame? Have you considered an outpost frame? Idk if it’s a 90s frame but very common

    50. PatternsInJade on

      Lots of good and sensible takes here. For your money, an entry level gravel bike like a Poseidon is definitely an easier way to go but building something is fun.

      I would suggest looking at early 90’s Trek Hybrids. I went with a ‘92 Multitrack 750 and find it to be pretty great. The frame geometry is identical to the 520 drop bar touring model of the same year so it rides great and is comfortable with drops. I’m running 38c tires with fenders but have room for more, probably 42 or even 45c without fenders. Cantilever brakes have been just fine.
      New wheels, cassette, stem adapter, bars and shifters are basically the only parts I needed so my budget was about half of what you’re looking at, including the bike. Source used road parts instead of new like I did and you’ll be in even better shape.

      Lots of great advice here but build what you want! Happy to elaborate more if you’d like.

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