# 1991 Schwinn Sierra MOS



## DrFizz2k1 (Apr 18, 2010)

I just got this a couple weeks ago, got it cleaned up and tuned up a bit, and figured I should post up before parts start arriving this afternoon.

*Frame:* Schwinn M.O.S. Tri-Butted (Cr-Mo) tubes w/ oversize head, seat and chainstays, 16.7" G-Force chainstays
*Fork:* Tange/Schwinn G-Force Cr-Mo w/ 800mm radius. OS Blades
*Rims:* Ritchey Vantage 26"
*Hubs:* Shimano Exage 400LX
*Quick Release: * Shimano 400LX
*Tires:* (Factory) Schwinn KOM skinwall (HAD Mismatched) Kenda Kinetic rear Tioga Psycho in Front... (NOW) Kenda Kross 26x1.95
*Pedals:* (Factory) "MTB Steel w/ Toe Jammer clips.
*Crank:* Shimano 400LX, Biopace Chainrings (28/38/48T)
*Chain:* Factory ? (Should I buy a new one??)
*Freewheel:* Shimano HyperGlide Cassette, 7-Speed, 13-30T 
*Front Derailleur: * Shimano Exage 400LX HyperGlide, SIS
*Rear Derailleur:* Shimano Exage 400LX HyperGlide, SIS
*Shifters: * (Factory) Shimano 500LX.. front was broken. (NOW) Shimano Altus ST-EF50.
*Handlebars:* (Factory) Schwinn 25.4 Team Issue Cr-Mo (flat w/ 6* bend) (NOW) Easton EA30 25.4 1.5" Riser (I wasn't comfortable with the flat bars.. short arms I guess.. HAHA)
*Grips: * (Factory) Foam. (bad condition.. 20 yrs old LOL) (NOW) Schwinn cheapies from Walmart. Sette Type-S Lock on set on order
*Stem:* Schwinn M.O.S. Team Issue Cr-Mo, Internal cable guide.
*Headset:* Tioga Avenger OS, Sealed.
*Brake set:* Shimano 500LX-SLR 
*Brake levers:* Integrated w/ Shimano ST-EF50 Shifters
*Saddle:* Schwinn MTB, Emerald Skin
*Seat Post:* DP-K, 350mm, Schwinn QR-Pin
*Paint:* Red w/ Black Spider
*Size:* 17" (I am only 5'6")

Schwinn Catalog....



















Pics... Condition when I bought it....





































And after a bit of a bath.....





































It's nothing special.. But It's a great fit, has already lasted 20 years, rides great, and I like it... I dont do any serious off road riding at all (obviously) and keep to the streets, and some 24 miles of paths in my neighborhood... Thus, the slick tires I ordered... I bought some paints to fix the scars on the frame, red, black and silver to touch up everything... I may tear it all down, and redo the whole frame... I have a custom vinyl graphics guy who could make me all new stickers to match the factory stuff... I'm really enjoying riding, and have already learned alot about repairs and adjustments and how to maintain a bike... I look forward to learning much more, and plan to upgrade this bike to the fullest I can over the summer, and will buy a new "good" bike once work picks back up hopefully next fall..

I'll update this as I change the bike, If there is any interest at all..


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## jtmartino (Jul 31, 2008)

"Into serious racing? What about adrenalin?"

LOL. :thumbsup: 

Marketing jabs aside, I like restoration projects well-documented with pics. Keep 'em coming .


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## sgltrak (Feb 19, 2005)

Those were decent bikes at the time. I sold them new and sold one to my roommate in college. He rode it pretty hard and it held up well for him. Thanks for the photos.


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## IMFitz (Aug 17, 2011)

I bought a bike just like yours a couple weeks ago. Mine has a taller frame and has had the wheels changed from stock, but is pretty much the same.

The problem that caused the original owner to sell it is that the chain "skips" in higher gears. He had replaced the chain and RD trying to fix it. When I bought it, I thought it might need a new cassette, but after cleaning the crud and sticks out, and closer inspection, found that it appears to be OK. However, I did find that the front chain rings are in terrible shape and appear to be the problem. The teeth are worn badly, and the rings are very much egg-shaped!

Once I get those rings replaced, it should be in good shape. The best thing about the purchase is that the previous owner just put new Vuelta Zero Lite wheels on the bike.


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## galleta loco (Feb 7, 2011)

Nice pics and report:thumbsup:keep it up!!!


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## DrFizz2k1 (Apr 18, 2010)

the front chainrings are supposed to be egg shaped on this bike. It's the "Biopace" thing.. it is supposed to be optimized for maximum leverage. Mine are worn too.. and i am getting a "click" each time around with the pedals... Im not slipping any gears yet so i'm holding off replacing anything else until it breaks..


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## wv_bob (Sep 12, 2005)

Fitz, you should probably check the hanger alignment too


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## girlonbike (Apr 24, 2008)

biopace is making a comeback!:thumbsup:


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## IMFitz (Aug 17, 2011)

DrFizz2k1 said:


> the front chainrings are supposed to be egg shaped on this bike. It's the "Biopace" thing.. it is supposed to be optimized for maximum leverage. Mine are worn too.. and i am getting a "click" each time around with the pedals... Im not slipping any gears yet so i'm holding off replacing anything else until it breaks..


Oh, I had no clue. Makes sense. Well, hopefully it is just the worn teeth. Thanks for the info!


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## IMFitz (Aug 17, 2011)

wv_bob said:


> Fitz, you should probably check the hanger alignment too


I've spent some time adjusting and looking at alignment. I think this is OK, but I won't try to act like I know what I'm doing with bikes.


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## IMFitz (Aug 17, 2011)

Took a pic of the bike while home for lunch.

The gear skip problem only happens when I'm in any of the four smaller gears of the cassette (with the front on largest gear), or if I use the middle or small gear on the front with any rear gear. If I stick to the large gear up front and the larger three in the rear, it doesn't do it.


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## DrFizz2k1 (Apr 18, 2010)

Shoot a pic of the front rings and the rear cassette. 

It looks to be a bit newer than mine.. certainly is a MUCH taller frame.. LOL.. I'm only 5'6.. scored when i found mine the size i did.. HAHA.


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## IMFitz (Aug 17, 2011)

I shot this one at lunch too, but didn't get a close-up of the cassette. Can do that later.

This is the height I was looking for since I'm 6'1". Stand over height is about 33-1/2".

Thanks.


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## IMFitz (Aug 17, 2011)

Here are some pictures of the rear cassette, and the chain rings. Let me know if you see anything wrong. Thanks.


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## jtmartino (Jul 31, 2008)

The skipping is likely coming from the cassette. The gears look pretty worn out. Get a new cassette and make sure your chain isn't too stretched out. Nashbar sells 7 speed cassettes for cheap:

Nashbar 7-Speed Mountain Cassette - Normal Shipping Ground


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## AM515 (Jul 12, 2012)

DrFizz...
I couldn't send a PM so here's a copy of the message I tried to send you.


Hey, I know that you posted about your bike long ago, but I was wondering if you ever got the decals that you mentioned in one of your posts? I just purchased a 1990 Schwinn Sierra MOS and I want to replace all the decals after I strip it and re-paint it. I've done a google search for an online shop that has the decals in stock or that can reproduce them and I've had no luck. Any information helps. Thanks.


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## DrFizz2k1 (Apr 18, 2010)

Actually what I did was... because they weren't stickers.. I wanted to maintain the "vintage" spec.. I bought some paints.. (Testors) and hand painted the scratched parts back on. Luckily the color matched pretty good. I can link you to a guy who can do the vinyl stickers though if you like...

Stickers guy

I'll snap some recent pics in the next day or two, weather permitting...

Sorry I'm not more help..


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## DFA (Jan 26, 2004)

I have a soft spot for the old Schwinns. Bought a Paramount PDG 70 back in 91. Stripped the parts off it to build my the Edge up in 93 and sold the frameset. Found another one on Kijiji in the spring locally and scooped it up. Still had the reflectors on it.


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## always_last (Jun 7, 2012)

I had a Mongoose, my first mountain bike, from the same year. Nearly identical red paint job with black swirl splatters- the early 90's were crazy like that. Of course my frame was made from straight gauge gas pipe and the bike weighed 35lbs. I still rode it on the trails somehow. Thanks for the photos, it brought back good memories of my early days.


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## skoda (Sep 27, 2010)

Nice bike, I would not only replace the cassette and middle chainring, I would also replace the chain. Chains are inexpensive unlike cassettes and chain rings. If you ride often replace the chain each year, your cassette will last much longer!
Cheers


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## AM515 (Jul 12, 2012)

Hey guys...so as I posted earlier, I just got my hands on a '90 Schwinn Sierra MOS. I stopped by this house in which the family always has a new batch of old beaters that they tune and sell off. I asked the guy if they ever run into the original components that the Sierra MOS came with, or upgrades and he recommended that I not do anything with the bike. He said that parts are hard to come by, the bike wasn't that great in 1990 and it's not that great now, he also said that many new components might not fit the old frame. He added that it'll be expensive to rebuild it into something decent and that I would never get my money back if I try to sell it off just because of the "Schwinn" on it.

I knew I didn't buy a diamond in the rough, but is he right? Also, the wife and I already have mountain bikes so I don't necessarily need the Schwinn if it's crap as this guy made it out to be...I liked the appeal of a semi-old bike of good "quality". Should I chop it and make a homemade tandem bike with it instead?


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## skoda (Sep 27, 2010)

KEEP IT!!!!!!! A Chrom-moly double butted, quality steel frame is strong, lively and responsive. The components look good as well, touch-up the paint and overhaul all bearings and you will have a great bike.
Cheers


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## Offroadman (Jul 18, 2012)

Cool bike---do it!!


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## smello (Jul 17, 2012)

Lookin good!


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## lifebeginsafterdeath (Jul 10, 2012)

i also have a sierra. it almost all original. bought it when i was up in Connecticut a truck load of years ago. may have 20 rides on it? just had it tuned a couple weeks ago. it has 4130 chrom moly on it, whatever that means?


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## skoda (Sep 27, 2010)

A high quality, light butted alloy steel that when built into a bicycle frame is resilient, responsive and lively, unlike aluminum and to some extent carbon fiber that are often more harsher riding than steel frames.


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## penvosea (Jul 28, 2012)

Great stuff man


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## StanleyButterfly (Nov 4, 2009)

I remember this being a tank. Get some sweet air on it and post some gnarly pics!!!


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## JPBakerIII (Mar 26, 2012)

I have a 1990 Schwinn Sierra MOS. I have changed out the shifters, seat, chain, and of course, tires. I have some real nice new mountain bikes that are better suited for dirt and trails but the Sierra is still a good bike to tool around the neighborhood on. Probably won't ever be worth a fortune, but it is very dependable.


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## the kraken (Jan 13, 2012)

I had one of these back in the day, it was my first mtb. I have such fond memories of that bike. Thanks for posting this. The pics are great! 

Here's mine, 20 years ago:


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## jimx200 (Oct 13, 2009)

Here she is..my latest find on CL: not sure of the year, but a absolute steal at $70. Only negative is a 13 yo kid (it was his dads) tried to peel off some of the name on the top tube. Everything is original, except for the tires that were just replaced. It's a 21" frame and loved my initial ride. Swapped out the seat for my WTB.


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## BRnPA (Oct 9, 2020)

*1991 Schwinn Sierra MOS - Mine still going strong...*

Admin - please delete.


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## BRnPA (Oct 9, 2020)

*Also have a 1991 Schwinn Sierra MOS - [Q] Upgrade or should I drop $$ on a new bike?*

Admin - please delete.


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## BRnPA (Oct 9, 2020)

*1991 Schwinn Sierra MOS. [Q] Upgrade or Spend $$ for new MTB?*

Admin - please delete.


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## BRnPA (Oct 9, 2020)

*1991 Schwinn Sierra MOS - Mine still going strong...*

I have this same bike that I bought in 1991 while in grad school and i'm still riding it. Changed the tires and basically kept it pretty clean. Still rides smoothly and shifts great. It is a little heavy compared to modern mountain bikes. I've been riding it a little more lately and was wondering what minor upgrades I could make to it to enhance the experience. I mainly ride on paved surfaces, gravel trails, and occasionally something aggressive (on the east coast). If I wanted to upgrade the original Shimano 400LX STI 7-speed shifters, what's the best replacement options? Are the older Deore 7-speed shifters still haunting Ebay?

Also - I've been toying with the idea of actually buying something newer and lighter. This has my attention right now but I'd wait until all the COVID-19 bike buying subsides (hopefully next year). Thanks.


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