Cactus459

So I am wanting to try converting an old mountain bike to a gravel bike. Some of my concerns include reach because going to gravel bars from flat will effect handling, and the second big concern is tire size. The two bikes I have to choose from are a 1992 Gary Fisher Sphinx 700c tires or a 1990 Specialized Rockhopper Comp 26" tires. The Sphinx is a tad shorter in the reach department. I believe the Sphinx will handle a 700 x 46 no problem. Also have some 650b rims I could put on either bike with some modifications to the brakes

Looking for opinions on which one you would convert to a Gravel bike and why? Thanks for any additional information.

1992 Gary Fisher Sphinx

1990 Specialized Rockhopper Comp

tangerineowl

Sphinx.

Starting out with the rollover of a 700c. Dropbar? frame design.

46mm is a good width for gravel.

Just read of the 88mm bb, which is interesting.

Am guessing these days there may be a few better performing brake setups available.

Cactus459

So has anyone even owned the Gary Fisher Sphinx? It is very hard to find much information on the bike. I mounted some Specialized 2.1 inch Ground Control tires, and the front is fine but the back is tight in the chain stays also rubbing the front derailleur hanger bolt. I am guessing I think max width might be about 1.95 inches or about 49mm?

Cactus459

Thanks for chiming in, what would you recommend in the brake department?

mstateglfr 

Between those two- Sphinx.
Never heard of it, but 4min of google reading is enough to say that I would choose the Sphinx for sure. 88mm of bottom bracket drop is significant as the current average for new gravel bikes is probably 72mm right now, but even with that considered it would still be what I would use to try and make a drop bar gravel bike.

My first gravel bike was an early 90s Univega hybrid that I converted to drop bar to ensure I liked the style of riding. It fit 40mm tires with ease and that width +/- 3mm has been enough for me thru the years.
For brakes- use cantilever since they have the proper pull to pair with STI shifting. Find some bars you like the bend shape of, find a stem that is the right height/length, and try it out.

As for tires- 50mm is really wide. Its definitely on the high side of the current tire width spectrum. Obviously there is no right or wrong way to do things, but just keep in mind that a 40-44mm tire can be plenty wide and comfortable on a lot of types of gravel.

DorkDisk

Sphinx, for 700c and shorter top tube.

Regarding brakes, it depends on which brake levers you will use. For modern STI, I live miniVs, for standard brake levers with bar end shifters, maybe cantis will be better.

Does yours have a 1-1/4"headset?

Cactus459

Yes the Sphinx is the Evolution series with the 1 1/4" fork and the funky bottom bracket.

katsup

Finding a suitable 1 1/4" stem may be difficult.

The rockhopper appears to be 1" which would be easier, but reach may be long. I've tried the same with a few 22" (23" reach) bikes.

I'd vote for flat bar gravel build with either.

mstateglfr 

I know ow camera angles can mess with frame size appearance, but those look like very different fitting bikes. Significantly different.

tangerineowl

There are a few 1 1/8"-steerer stems out there. Sphinx has the higher front end to start with.

If wanting dropbar, a short reach and short drop like the Dixna Neither 2 would be a good choice to get a decent fit. 52mm reach. 64mm rise / 40mm?drop.

Running a bar like that would allow you to fit a less angled stem.

katsup

The Sphinx is not 1 1/8", it's 1 1/4".

shoota 

Gary Fisher, no question.

Cactus459

So you hit on something that is definitely different. The Rockhopper feels a bit big and the Sphinx feels a bit small. I ride a 58 in my road bike and a large frame in my current Stumpjumper.

Sphinx
22" tt
​​​20" ct
22" front axel to top of head tube

Rockhopper
24" tt
21.5" ct
22.5" front axel to top of head tube

Cactus459

I am currently trying to find a adapter that would let me use 1-1/8" stems but they haven't been made for years and currently searching eBay. I know that my older Trek has the same size fork as well as my older Cannondale. I have a few 1-1/4" stems but nothing shorter than what is already on the bike.

tdilf

Start with the red one.

mstateglfr 

https://www.benscycle.com/nitto-mt-s..._3488_sm1062/p

Then just use whatever threadless stem you want and whatever bar you like.

Cactus459

I purchased this adapter, hopefully it will allow me to be able to fit the bike with comfortable stem and bars. Also couldn't find much selection for a drop bar that was flared.

I guess I will start with the Sphinx and I can always try the Rockhopper at a later date.

I tend to prefer 42cm bars on my road bike, but I noticed a trend where people seem to be going wider on the gravel bikes. Any suggestions on width of bars? Thanks

mstateglfr 

The selection of flared drop bars is seemingly endless. Ritchey, Soma, Origin8, Salsa, PNW, Whiskey, Spank, ProDesign, FSA, Zipp, and many more brands have em. The bends are all different- some have a sharp bend with minimal drop, some have a lot of flare, some have sweep, some have ergo bends, etc etc. While one may be terrible, another is perfect.
Look at FSA, Zipp, and Salsa to start. Zipp Service Course has an option for sure, FSA Adventure bar is another to start, and Salsa has 3 different styles- Cowbell, Cowchipper, Woodchipper for you to visually see the differences.

ksryder

I like a slightly wider bar -- 44 cm -- because I'm a bit broad shouldered. I also like a minimal flare -- 12 degrees max. I prefer a shallow bar so I can spend more time in the drops during long headwind sections more easily. But these are all highly subjective and personal preferences and there's a million choices. Eventually you just kinda have to bite the bullet and get something.

Brakes -- Tektro 720 is kinda the go-to budget canti brake. Tektro mini-Vs are a pretty good option for V-brakes but personal experience with those is that even though they provided great stopping power, they were pretty tight on the clearance and I'm not sure they would've worked for anything more than a 38mm tire. Also they were finicky as hell and seemed like I had to adjust them every time I removed the wheel. Eventually went back to cantis.

If budget isn't an issue then get Paul everything. Of course you're probably not converting a vintage hybrid to gravel if that's the case.

Cactus459

Well just got confirmation that the adapter is out of stock and got a refund. Any chance someone has any other leads?

Germany_chris

I like my 50cm kitchen sink bars..

I also run those Chinese replica travel agents to use full fat V-brakes and road levers

Cactus459

Anyone have a lead one a stem adapter for1-1/4" threaded quill to 1-1/8" A-Headset adapter?

Fentuz

to the OP, you might want to check youtube spindatt channel, he did a comprehensive rockhopper conversion. if you like it, you can either replicate it to your own rockhopper or if you want a faster bike with bigger wheels, apply the same concept to the sphinx

personally, I would look at both bikes original equipment, check which one can get the easiest steerer conversion and check if the rear free hub can take 8,9 or 10 gear cassette and then if all equal, convert the the lightest of both.
Scrap the groupset a put a shimano sora 9x2 with 11-34 (or push to 11-36) 9 speed cassette and select the 2 chainring depending of the terrain you want to ride (compact 50-34 or easy 44-28)

Metieval

I vote Sphinx

scubaman

IDK why everyone votes Sphynx. Elsewhere on Bike Forums is a thread with literally hundreds of people posting about their drop bar conversions of old 26" MTBs. If the Rockhopper fits you now with the very long stem in the photo, it will fit you with a tall quill adapter (1" to 1 1/8", which should be easy to find), a short stem, and gravel drop bars (I've used Salsa Cowbell and Cowchipper for exactly this type of build). The rest of the conversion will mainly be similar oh both bikes, except the tires. René Herse, Sim Works and others make high quality 26" tires; I've built multiple bikes up with René Herse' wonderful 26" x 2.3" Rat Trap Pass tires, and have done gravel & bikepacking trips with them on a bike like the Rockhopper with a drop bar and updated drive train etc., and the bike rides and handles great. Yes, an old rigid MTB has a higher bottom bracket than most current gravel bikes; for me, at least, that hasn’t been an issue, and on certain terrain it can be an advantage (which is why they were built that way in the first place). The rest of the Rockhopper geometry is pretty similar to modern gravel bike, especially with a short stem.

If you can indeed fit 700c x 46mm tires on the Sphynx, and you can figure out the stem issue - that Nitto adapter may be available elsewhere, but it's quite short! - then that's also a good option to convert. But it's definitely not your only good option!

BTW, the cantilever bosses on both frames make it difficult to switch wheel sizes. I doubt you could get brakes that work with smaller wheels than the bike was built for. I've seen builds where someone put 650b wheels on a 26" bike with canti bosses, using cantilever brakes on which the pads are raised to fit (Paul Comp make brakes that enable this, as do some others); I'd worry about what that does to the brakes’ mechanical advantage, but you could try it and see if you have adequate braking power, or maybe there are folks here who can comment firsthand.