oldschool33

I just bought a 1994 Rockhopper Sport 18" frame & fork, which I'm hoping to convert (well, build.. since I only have the frame) up to something gravel-capable.

It's my first time doing something like this and before ordering parts I wanted to double check a few things. Here is my proposed build:
Wheelset: WTB DX18/Shimano HB-M475 27.5" w/ Shimano hubs - I've heard 26" is not great on long trips and 700c doesn't work well with the geometry, so 650B feels like the right compromise. Planning to put ~48mm tires on it. Curious if anyone has tried this set up?

Crank: Shimano 32T - I'd love to get 36T so I have more power at high speed but I can't seem to confirm that the 36T chainring can clear the frame chainstays - can someone confirm??
Rear Cassette: Shimano CS-M4100 11-46T 10 speed
Rear Derailleur: Shimano RD-M5120 - The 4120 is much easier to get but it seems it has no clutch and may not work with 11-46T, so better go for the 5120, right?

Shifter: Microshift M100 OR Deore M4100 - still debating whether to go for these with dropbars (which makes geometry weird but maybe better for long distance) or get sunrise/butterfly bars with a deore shifter - curious to hear opinions on this!
Brakes: TEKTRO CR720 with a 650B adapter... though I'm open to suggestions here as well!

Bottom Bracket: Shimano MT501, 68/73mm - unclear whether BB is 68 or 73mm, but it seems most BB will fit either.

Thanks fir any thoughts you might have!

maddog34

the 36t chainring may or may not hit the DS chainstay, but since you're going 1x, you can move the chainline right a bit to gain clearance by using a different BB length.I prefer seeing at least 1/4" clearance between the chainstay and Chainring.. less will have the chainring hitting the frame when you are stomping up a steep trail.

the rear dropouts are too narrow for a 135mm O.L.D. hub that will be the standard hub in a 27.5 wide rimmed MTB rear wheel,

Drop bars are a bad idea with that frame since it's designed for a flat bar and is too long for drop bar/rider fit... you might find a really short stem to make it work, but still, the geometry is going to be odd, at best. Drop bars put your hands 4" forward of a flat bar riding position, AT LEAST... So unless the frame is now Way Too Short for you, you Won't Enjoy the stretch. Stay with a Flat Bar.

and, on a personal note.. i don't use Microshift on ANY build...they feel cheap and clunky, even when "brand new." SRAM is just as bad, IMO... Go with Shimano Alivio, Deore, or XT.

along the way, i spotted an Ebay listing for a 1994 rockhopper sport... the seller is asking $3295... he is insane. The bikes sold for $500 new...It was a midrange bike then, and is still a midrange bike today, with No decent features.. No amount of bolt-on bling. will change that fact.

$699 will get you a 27.5" wheeled Rockhopper with better Geometry, a suspension front fork, and disc brakes, Brand New.

soyabean

This implies you have little idea as to what will work, and regardless of how much you do to this project bike, there is no "best build".

Custom builds are to the flavor of the builder/rider, using parts that they know and trust and best for THEM, the individual.

If your intention is to have a bike for a great cycling experience, take the advice of the above reply and visit your LBS for a good bike.

A 1994 Rockhopper at the end of the day is still a vintage unicorn worth $50.

kommisar

I would ditch the change in wheel size. I would be concerned that it would effect tire clearance at the fork crown and bottom bracket because of the increased diameter. At least one "expert" thinks 26" is just fine for gravel:

https://www.renehersecycles.com/how-...should-i-ride/

You need to consider the stem you will use because of the much longer reach of drops. Here is a discussion about stems:

https://old.******.com/r/xbiking/com...ar_conversion/

Here is a discussion about the frame specs:

https://old.******.com/r/bicycling/c...ed_rockhopper/


edit: WTF? my links were broken by this website. They are pointing at the site that rhymes with beddit.

wheelreason

No issues with tire clearance, that unicrown fork has lots of clearance, and the diameter difference won't be much anyway. I had a Comp a couple of years older, and while a good bike, Popeye should have gotten a tattoo of it on his forearm,

oldschool33

Thank you all for the input! For context, I already have a Topstone Carbon gravel bike, so this project is purely for fun / to learn how bikes work. I'm definitely not expecting to save money or to end up with a bike that's "worth the money" compared to a brand new one. Since it's my first time, it's also true that I won't be able to personalize it very much to my preferences, but I'm at least trying not to make any obvious mistakes. I'm trying to make the bike into something that I can use for commuting and maybe take on slightly rougher trails, where I might not want to risk a carbon frame.

What I'm hearing so far:

1. Rear dropouts are too narrow for 135mm O.L.D. wheel - I think that might be the case with other vintage mtb frames, but several people have said the rockhopper is at 135mm. I could be wrong of course - this comment makes me think I should wait to receive the frame and measure for myself before ordering the wheels, so thank you.
2. Dropbars will make a weird geometry - I was already hesitant about this one, thanks for confirming it. I think in the end I'll go with with bullhorn, sunrise or butterfly bars that would work well on longer trips.
3. Microshift will feel cheap - Understood, I've heard this one elsewhere and also got that feeling when I rode a Topstone 4. Since I won't be using dropbars, I can just go with the Shimano M4100 shifters
4. I might need a larger bottom bracket to make the 36T chainring work - Does this mean I should be getting an 83mm one instead of 68/73? Or I get the 68/73 and add some sort of spacers?
5. 26" will work better - I'm fairly committed to 27.5" at this point and I've seen many examples of people making it work. The brakes will be tricky as I'll need an adapter, but it should be doable.

Thanks again!

maddog34

As to whether a 36t will clear the frame... exactly WHICH crankset and bottom bracket are you planning to use?
The overall with of your frame determines which width BB Body you will need, but there are a lot of different STYLES and LENGTHS of bottom bracket SPINDLES available... And if you're getting a HT2 Crankset, the spindle lengths are set.. the 68, 73, and 83 boost frame widths are detemined by the Frame, a 68/73 HT2 bb is for MTB cranksets, mostly.. and 83mm BBs are for the Boost framed bikes..

Measure your FRAME's BB and report what you find.

your chosen frame came with a square taper crankset and BB... there are others, including the popular Shimano HT2 style... the BB threading is English 1.37 x24tpi.. the most common type! this is a good thing.

the square taper spindles come in a wide range of lengths... HT2 is one length for road style cranks, and one length for MTB cranks... Octalink2 spindles can be found in 4 lengths... Octalink1 spindles are pretty much obsolete now... ISIS/Gigapipe is another style spindle for several non-Shimano Cranksets.. etc.

whichever crankset you decide on,get an MTB crankset, or the pedal end of the arms might hit the frame no matter what.

Ironfish653

@ the OP; I think the spirit of this project is great, but you’re trying to force a bunch of idealized specs onto an as-yet unseen frame that may or may not work with them.

I ll try to hit some of the ones spelled out in the above posts:

Axle spacing; being a 1994 model, it’s likely a 130mm.
Specialized has used the Rockhopper name for over 30 years, on dozens of different versions, that share nothing in common except the stickers; MTB tech and standards update and change every few years, especially from the 90s through the 2010s, it’s hard to nail down the specs for a certain year model by trying to backdate from newer versions.
Also goes with the cranks/BB. You may have to get the frame in hand and take some measurements to determine what will play nicely together; although I suspect that being designed in the day’s of 3x7 triple cranks, it’ll be more of a matter of getting the right BB spindle length than chain wheel clearance


Handlebars are a concern for you, and it’s hard to guess what bars will work well, until you have the frame to pull a few basic measurements (to compare to your current bike). There are a lot of different alternative bar shapes besides standard-issue road bike drop bars, some are specifically intended for Gravel MTB conversions; the Soma Gator is a flattened out drop bar, Surly has the Corner Bar, which gives you a drop-bar-like position, while utilizing MTB controls, and typical MTB stems.

Finally, Wheels: I know you’re set on 650B, and I can see that as far as availability, there’s not many really nice 26” wheel sets being offered anymore, though some specialists like Velomine had some better than adequate options.
A 650x40 tire should fit the Rockhopper just fine, because it’s almost the same diameter as the 26x2.1 that would have been fitted when it was originally built; you just give up 1/3 of the air volume and have to finagle up some adapters to relocate the brakes

if you’re intending on riding a lot of irregular/ mixed surfaces, you may find that extra air volume useful. Not all 26” tires are beefy knobbies, either; Panaracer offers the GravelKing in 26x2.1, and there are a whole subset of high performance hard surface tires in the BMX category that do well on repurposed 26ers. The Maxxis DTH is a favorite here.


PS note: I’m seeing a lot of interest over the last couple years for restomod 1990s Rockhoppers; why that particular model? It wasn’t anything special, just a decent middle-of-the-road MTB

maddog34

there is a lot of them still around, they don't break, they handle well, and they can be had for pennies.
plus, the name is really cool.... like a fuzzy bunny with a mohawk haircut.

TiHabanero

I just picked up an 87 Fuji Sundance and an 87 Miyata Valley Runner, one to be repurposed for touring and the other a flip to help offset the cost of the other. Set up as a gravel bike is really no big deal as these are mountain bikes and made for dirt surfaces. The OP's Rockhopper is a good choice, however I hope he takes up touring as well because these old ATB's do touring very well.

SJX426 

@oldschool33 - I have a '97 and find it to be very versatile. It was bought new so it still has most of the original parts. one that changes was going from 7 to 8 speed because Amazon supplier kept sending me an 8-speed cassette instead of a 7.
One of the first things I did was change the stem to be shorter and put more street worthy tires on it.
RKHPRDrivSideW on Flickr

I have used to for commuting with a rack, bag and fenders.
1997 Specialized RockHopper on Flickr

found a suspension fork for it for dirt trails after riding a trail that beat me up. It is air suspension so I can adjust height after getting on to restore geometry.
1997 Spcialized RockHopper on Flickr

Event used the configuration for commuting to see if the fork impacted trip time, it didn't.
P1020526 on Flickr

Current state with 2.3 shoes
04272023RockHopper on Flickr

I call it my "truck" due to the versatility of it.

BTW: BB shell is 73. Rear spacing is 135.

wheelreason

Its like an Onza bar ends convention...

oldschool33

Thank you all for the replies!

After reading more about it I've decided to try with 26" with Maxxis as someone suggested. I think what turned the tide for me is seeing that the Surly Long Haul Trucker came in a 26" option. I do plan on using this as a touring / bikepacking bike, and it seems like 26s will make it a bit slower but not significantly so.

icemilkcoffee 

I doubt the 650B wheels would work with the rim brakes on the bike. Rather than converting to 650b wheels, I think you would be far better served converting to 26" tubeless wheels.

Another issue is that the drop bar has a larger diameter than the flat bars, so the Deore shifter most likely will not fit on the drop bar. I think your best course of action would be to stay with flat bars, but add some bar end grips.

t2p

I also like the Maxxis DTH 26” tires

included a couple of pictures (2nd, 3rd / bottom pictures) above of old MTBs with Maxxis DTH tires installed including one that someone did a drop bar conversion on

another tire option is the 26” Panaracer Pasela - included a picture (1st / top picture) of an old MTB with 26 x 1.75 Pasela on an old MTB

DorkDisk

TBH, 90s MTBs are great gravelers as-is. Just add some modern parts like V brakes, saddles with channels, slick tires, risers and go for it. Shedding the knobs goes a long way, DTHs are really nice and versatile.

Here is my 92 Stumpjumper (135mm spacing) which I use on the same routes as my Ritchey Swiss Cross; it yields a different experience due to the smaller diameter wheels.

TiHabanero

DorkDisk has it right, and I will add to it that any mountain bike makes for a great gravel bike as they are literally designed to excel in the dirt environment be it two track, single track or dirt roads. They just do it!

oldbobcat

Getting the brake calipers to work with 650b rims might be a problem. Measure carefully. Does anybody still make 26" tubeless ready?

As for shifters, bar-cons will always work.