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Saving a 1995 Mongoose Alta! - full drivetrain replacement
#1
Hello all,

I have ridden my bike, a 1995 Mongoose Alta, for the past 20 years and replaced just about every component on it except for the frame, FD and front wheel. Gone through 3 RDs, several chains, rear hub, both shifters, etc. I'd estimate it's lasted at least 30k miles. I put road slicks on it and use it as my daily commuter, going 10 miles/day now. Love the bike!

Last week, the chain started skipping when I pedaled hard, and I suspected the chain was stretched. I took it off and I can almost join the two ends together so it's pretty loose. In addition, the drive side crank has a hairline fracture in it that makes me think it'll snap eventually. Probably from turning too tight and scraping the pedals on the asphalt.

Since the chain is stretched and the crank is cracked, I figure I would need to do the following to get the bike back into shape:

- New chain
- New rear cassette / gears
- New crankset
- Perhaps a new chainring? The ones on there look fine, but I'd like to upgrade to remove the granny gear, and add a 48 or 50 tooth chain ring to get higher speeds.

I've been looking around for parts, and I'm hella confused as to what will work on my bike. Currently, it has an Alivio RD, 7 speed gears (I don't know if it's a cassette or gears or what...), and an STX FD (original) with the original bottom bracket and STX crankset (5 prong).

Part of me says it's time to retire my trusted bike. I went shopping for a new bike on Sunday and didn't quite find what I was looking for. The closest thing was a Trek FX 7.4 and it's about $700 a the LBS. However, I felt pangs of betrayal as I thought about trashing my old ride and couldn't bring myself to do it.... yet. I know it's silly to hold onto a frame, fork, FD, front wheel, and the old caliper brakes.... I'm weird.

My question is - can I get the components I need to fix my bike up? If so, how much would it cost, and would it make more sense to buy a new bike or stick with the old?

From what I've seen, it seems I can get the cassette for around $30, chain for $15, but the crankset seems tougher to find, anywhere from $50-250. Also, not sure I can fit the 48t chainring on that crankset. However, I have no clue what actual parts I need, since I don't know anything about fitment and whether this works with that, etc.

I live near San Jose, CA, in case that matters. TIA!
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#2
San Jose area has more than one *bike co-op* available (Google it) I'd advise you to go there. Also, it's best to replace both crank and bottom bracket, as the new crank may require a different length spindle. You need to get the proper chainline when you replace the crankset.

Finally, a larger chainwheel will not make you go faster, and neither does removing the granny gear. Your current 42/11 small cog (you have a cassette) should be good for at least 30 mph.
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#3
p.s. The 42-11 on your cassette is good for at least 30mph, and given the mountains around San Jose I would not be so eager to get rid of the granny. You can always just adjust the derailleur so you only get the larger cogs temporarily.
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#4
If you can wait until Oct 11; I can help you out face to face.

What is your budget? Using new low end (durable, but heavier than mid to high end); I think you are looking at around $100 plus your labor for:
new bottom bracket, crankset with integrated chain rings, chain, cassette
Nigel
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#5
I forgot Nigel's from San Jose - his offer is worth waiting for if you can. That bike is definitely high-end enough to justify putting some money into it. If you really want a higher top gear and go for a larger chainring I would suggest you start with no less than a 12 tooth small cog - much less wear on the cog and chain. But again, it won't make you faster - and it will move all your gears higher.
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#6
Thanks guys!

If you'd help me ftf, that would be awesome! I would definitely take you up on that! I can wait until 10/11 to work on it if it means I can save my ride. Maybe I can trade you some homebrew by then. Right now, I swapped my tires onto an old 16" Mongoose Maneuver I had lying around... grip shift FTW! It's like moving from a road bike back to BMX again. Smile

I've been looking at mid-level components. I want good bang for the buck. The things that are important to me in order are:

1) Durability - This is my commuter, I don't want it to break down.
2) Cost - I'd like to stay reasonable with the cost.
3) Weight - I don't mind getting more exercise on my commute, it's only 15 min anyway for 5 miles.

Back in 1994, I bought STX because it seemed like a good compromise for quality vs cost. Didn't want to shell out for the Deore, XT, or XTR at the time. That decision has served me well, although the derailer died when the chain snapped off and took it with it.

I'm not as familiar with the component levels that are around today; seems like Acera, Alivio, or Deore may be right for me? I'd have to see the read reviews to get an idea of durability, and weigh the costs.

I use my bike for 95% road riding, with some minor trail here and there, like cutting across sidewalks / patches of grass / dirt. Rough asphalt (potholes), hopping curbs and such, which is why I wanted the MTB frame + wider slicks instead of a pure road bike.

$100 is totally reasonable, compared to the cost of a new bike at $500+.

Also, thanks for the pointers on top speed. I guess my cadence is really slow and I need to work on that instead of the high torque I've been putting out. I tried lower gears on my commute to work today and it was... different. When I pedal real fast, it feels like I don't get enough "oomph" out of each stroke.

Right now, I only use the 42t gear with the top 3 rear cogs. I've never used the other two chain rings at all! (part of the reason is because my front shifter is FUBAR'ed and can only shift between the middle and large chain rings... if I move the chain manually!)
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#7
For cadence, find an rpm rate that feels reasonably comfortable (not too fast but less oomph). Then just shift to maintain that cadence. The "oomph" may feel like you're doing more but in fact for a variety of reasons it is both slower and poorer at getting you faster.

There's no sense in worrying about weight on derailleurs and cranks for your usage - not worth the time/effort for a few dozen grams (yes even for 100 grams). durability in the Shimano line is more a factor of how the equipment is treated than how it is designed, until you get higher, where things are sometimes LESS durable.
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#8
I finally met Nigel today. Great guy, he removed the old crankset, BB, and rear cassette and gave me an idea of what I need to get.

The parts were in decent shape for being so old. The BB is original, and is still sealed. It catches in one spot as I rotate it, but it wasn't noticeable when the crankset is attached. The crankshaft has a crack in it, so that's definitely got to be replaced.

I've been searching online for parts, and I'd like to get the group's opinion on the following setup:

I chose the crankset because I wanted to keep a similar component level to my old STX. I saw the cheaper M171 cranksets, but couldn't find any specs on those from the Shimano website, making it hard to compare parts. This crankset also comes with the BB, which I think should fit my 68mm MTB.

I need the left shifter since mine is shot.

My Q's:

  1. Do I need to buy screws for the crankset to attach to the BB? Or is it all included?
  2. Is this chain a good one, or is there a better choice?
  3. Any other gotchas I should look out for?

I'm hoping to place this week so I can my bike back on the road over the weekend. Any thoughts or advice would be nice. Thanks!
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#9
Hi Steve;

Thank you for the kind words. Smile

The crankset you list above is Hollowtech - which means the cranks and BB interface is very different. It will work fine. I have never seen one, and do not know what tools are required for it. A review of Shimano's Tech Docs will show you.
I would have gone with:
http://www.niagaracycle.com/categories/altus-28x38x48t-6-7-8spd-170mm-square-w-guard
and
http://www.niagaracycle.com/categories/shimano-un55-bottom-bracket-68-x-122mm-english-threading
which is about ½ the cost. Downsides are that the chain rings are not replaceable - not really an issue; that it would be ½lb heavier; and the granny ring is 28 vs 26 - not an issue for you anyway.

Cassette; I think that you'd be happier with an 11-28 given your description of your riding.
http://www.niagaracycle.com/categories/shimano-acera-hg41-7-speed-11-28t-cassette
http://www.niagaracycle.com/categories/sunrace-csm63-7-speed-bicycle-cassette-11-28

Chain is fine, though I prefer:
http://www.niagaracycle.com/categories/kmc-x8-chain-w-missing-link-6-7-8-speed-each-silver

Shifter is fine.

Sorry, I missed putting your crank bolts and cassette lock ring in the bucket yesterday. I will make sure that I don't loose them.
Nigel
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#10
Thanks Nigel!

I didn't realize about the Hollowtech. I'll go with your recommendations. I've ordered the parts and I'll have them soon. I won't have time this weekend, but if you're around the next weekend (10/25) I'd love to stop by and borrow your tools to finish the job!
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