Cheseldine

Hey everyone,

I recently acquired an old Jamis Diablo mountain bike for $15. It was covered in thick tan dust, and had everything known to man bolted to the frame - a backpack strap hooked to the seat tube and top tube (factory option), pump, rifle rack on handle bars, front and back lights, front and back racks, fenders, cable lock on the downtube, and saddle bag.

After stripping all of this off, I found that the frame is actually in really nice shape and is fillet brazed on the headtube joints and seat tube/top tube intersections and made of tange double butted tubing.

I originally thought it was black, but it's actually a really deep metallic purple. I touched up the chips, covered them with automotive clear coat, and polished them down to get it looking in pretty nice shape. I treated the inside of the frame with phosphoric acid to neutralize and prevent any rust, although it was quite clean.

Anyway, I'd like to put some thinner (1.5 to 1.75") tires on it and convert it to more of a dirt drop setup. Do you folks have any good ($25-30ish) tire recommendations that would be ideal for street and semi-rough gravel roads?

For bars I've been looking at the Salsa Cowchipper or Woodchipper, the On-One Midge, or trying to find a set of older WTB dirt drop bars. The bike has a threaded, rigid fork with (I believe, I'll have to double check) a 1" quill stem. What do you guys typically run for a new stem to convert to dirt drops with a bit higher rise that can take a 31.8 bar? Am I stuck using an adapter that I can clamp a modern stem onto, or does a dirt drop quill stem exist that can take 31.8 bars?

The group is all Exage Mountain which I think they only made for one year - I'll reuse the crank and hopefully derailleurs. The thumb shifters can work in either index or friction mode. It currently has a 6 speed cassette in the rear - how difficult would it be to convert this to a 7 or 8?

I'd like to use bar-end shifters (I'd be happy with friction or indexed) - which should I get that would work for this project? Any recommendations?

The rear u-bake is mounted on the chain stay, and was a big cracked plastic mess. Can I just mount a standard BMX u-brake like the DiaTech Hombre or Odyssey Evo 2? Of course I'd prefer an older XT u-brake, but they seem to be quite pricey.

As found:



After working over the frame - stripping down components, cleaning, sealing inside of tubes, touch up paint, polish, etc.

rando_couche

Tires: I've heard good things about the 26x1.75 Michelin Country Rock, and intend to try 'em when I wear out the 26x2.1 knobbies on my bike right now.

Stem: Velo Orange has a nice looking 31.8 quill stem https://velo-orange.com/collections/...ceplate-31-8mm

Shifting: If you're happy with friction shifting, then just about anything will work. Rather than updating to 7 or 8 speeds, I'd recommend going to 9 as there's still a good selection of new parts available for that.

TenGrainBread 

Nice find! Old Jamis MTBs are pretty sweet. I believe these were first TIG welded and then fillet brazed over the TIG weld for aesthetic purposes.

I wouldn't assume that your headset is 1". It might be, but 1 1/8" threaded headsets were also popular around that time. Measure the quill (insertion) diameter with some calipers. Once you know the headset size for sure, you can choose a stem and bar combo. As far as the stem goes, for a dirt drop mountain bike you want a tall stem with not much reach (as the drop bars will stretch you out).

For 1" threaded stems, I would check out the Nitto Dirt Drop stem. You can also use a tall Nitto Technomic stem. These are 26.0mm or 25.4mm clamp only, so you will need handlebars that fit this. Nitto's Dirt Drop bar comes in a 26.0. You can also check out the Rene Herse Randonneur bend bar, in a 25.4, also made by Nitto. If you need a 31.8 clamp diameter stem but don't want to use an adapter, Velo Orange makes a tall 1" quill stem with a 31.8 removable faceplate. It might not be tall enough, though. Another option is getting a 1" threaded to threadless stem adapter and then using a threadless 1 1/8" stem, like the Velo Orange Cigne stem or the Crust Bikes LD stem, as you mentioned.

For 1 1/8" threaded stems, your options are more limited. Most vintage stems of this dimension were very long, meant for flat bars. Pairing these long stems with drop bars makes fitting the bike very difficult. Sunlite makes a 1 1/8" aluminum quill stem that I have used before. It has a faceplate for a 26.0 handlebar. While heavy, the finish is decent on it and it gets the job done. The other option is to get a replacement 1 1/8" threadless fork and then run a threadless stem. This widens your options but costs more, and of course you don't get to use the Jamis fork.

Cheseldine

That reminds me, I'll have to measure the rear drop spacing - I'd need 135mm for 9 speed correct? Would the wheel need to be redished?

As far as the stem goes, I won't know final height until I see how high I need the seat - that being said, I'm looking for a dirt drop specific one to get the bars up high enough. Something like this, but in a different clamp diameter.

https://www.harriscyclery.net/produc...clamp-4528.htm

dickbandit 

I second the vote for Country Rocks. I have them on my drop bar mountain bike and they are a nice tire for the money.

Any reason you are married to the 31.8 bar clamp size? There are plenty of dirt drop options with 26mm clamp size. I went with the Soma Portola which is similar to the Midge. I used a Nitto Dirt Drop stem.

Good luck!

TenGrainBread 

Regarding tires-

I would recommend you utilize the full tire clearance your bike has. A 1.5" or 1.75" tire will not be significantly faster than a nice 2" tire, but will offer you less cush and traction when riding on rough roads, gravel, or single track. I would recommend a foldable Maxxis DTH in 2.15" width. If you were willing to spend more on a nicer tire, the Rene Herse 26" tire range will definitely ride the best out of all of them.

Cheseldine

Thank you for the great info, I'll get out the caliper tonight and pen down some of the necessary dimensions. So far I've mainly been cleaning up the frame and servicing the bottom bracket - soon it'll be time to start putting everything together. I want to end up with the drops about as high as the seat without too much reach as you are saying.

Cheseldine

I am definitely not married to the 31.8 - most of the decent options I ran across were in that size. I'd definitely be open to other bars as long as they are designed to use the drops as the primary riding location that have decent flare. I'll add the Portolas to my list of options and check them out.

Cheseldine

I am certainly no expert when it comes to tires, so I'll definitely look into going wider. I was planning to go thinner just to cut weight down a bit. You all are the experts, and if you tell me that a thinner/lighter tire won't be faster I'll take your word for it.

Squeeze

If you haven't seen this thread yet, you might get some ideas here: https://www.bikeforums.net/classic-v...nversions.html

Cheseldine

Pics moved to first post

Dylansbob 

Another much cheaper 31.8 quil stem is this Origin8 one.

https://www.bikewagon.com/origin8-st...2x110x31-8bk-p

ncrnelson

I like the Kenda small block tire, it handles pavement, gravel, dirt and sand well. It's a little wider at 2.1 or 2.3, though.

If you have 6 sprockets in the rear, then I think you'd have to be dealing with a freewheel, which means you'll need a new wheel with a freehub body if you want to move up to a 7-10 speed cassette. You'll have to check the rear dropout spacing as well

ryansu

I bought some Schwable City Jet 26 x 1.95 that were $40 for the pair shipped from Chain reaction cycles in the UK They were recommended here on BF, I thought they rode nice and definitely felt plush and I like the tan sidewalls. Nice Jamis OP have fun with it.

PS for a different bike I got a pair of Vittoria Evolution 26 x 1.95 from Amazon for about $25 for the pair and they were good too although I think I liked the Schwables better. YMMV. The Vittoria's were black walls and I am not sure the deal I got currently exists on Amazon.

Cheseldine

This was kind of a strange one - most of the components showed signs of pretty bad corrosion, but the frame itself ended up being very clean.

That said, I don't think the old Exage Mountain Derailleurs will be worth cleaning up - they show some pretty deep rust pitting, and the main springs are really rusted inside.

This is just like the one that was on the bike:

https://www.ebay.com/itm/New-Old-Sto...0deca074de7751

I believe it's a bottom pull (no cables route on the top tube at all) with a 28.6 clamp diameter. Is there a good XT equivalent or should I stick with Exage Mountain?
Thanks!

Cheseldine

I measured the stem diameter where it inserts into the steerer and am getting a reading of exactly 22mm. Are stems typically undersized a touch? I was expecting a 22.2 and thought 22mm was only on older French bike. Anyone know if late 80s mountain bikes ever used 22mm?

Pompiere

They typically measure a little smaller than the stated size. I have a couple that are marked 22.2 and can fit in an older Peugeot tandem.