Bicycle Mechanics - New MTB Chain-rings With Old Deore XT

I've finally decided to replace the Bio-Pace rings on my MTB with real chain-rings; the Bio-Base has to go, (can't take it any longer). I have a Diamond Back Arrival bike purchased back in +/-1985. It has original Deore XT. It has 5 arm/bolt cranks.
Will any Shimano 5 bolt MTB rings fit these crank-arms?
The rings are pre "compact" style and they are 46/36/26 rings. I would like to change to similar gearing as I don't subscribe to the new compact range of 42/32/22. Freinds I have spoken to that have newer "compact" gearing are unhappy with their top end when they ride on the road.
I'm unhappy with top end on mine with 46! Any suggestions on rings for my bike? The smallest cog in the back is 13. I don't want to replace the cassett to an 11 if I don't have to.
Can I get something like 48-50/36-38/22-26?
Thanks in advance for any help. The Fife

The fife; You’ll need to determine your Bolt Hole Diameter for the chainrings (hopefully stamped on the rings). Next you’ll have to take care about the ratio between big chainring-big rear cog verses the small chainring small rear cog least you exceed the capacity of your rear derailleur. Your rear derailleur travel will limit the amount of slack it can handle when in smallest gears front and rear verses how tight the drive train can go with largest gears front and rear. Sorry I don’t have numbers for you, however you might post the spread of the rear (13-??) cassette (i.e. what’s the max tooth cog?). I’ trust that information may help other folks give you the necessary wisdom.

Originally posted by The Fife
It has 5 arm/bolt cranks.
Will any Shimano 5 bolt MTB rings fit these crank-arms?
The rings are pre "compact" style and they are 46/36/26 rings.
Thanks in advance for any help. The Fife The crank takes 5 hole 110 BCD rings on the middle and big and 74BCD rings on the granny. Plenty of choices out there. Try www.branfordbike.com for choice,but you may find them cheaper elsewhere, like Nashber. You can easily do a 52x42x30 or a 50x40x28 with that BCD,but may need a road derailer to handle the bigger rings,which could create cable route isues if your current set up is not bottom pull.Ther are ways to convet a bottom pull derailer to top pull routing if necessary. Your rear derailer will handle the wrap as the original front chainring was a 2o difference and even the biggest combination mentioned is still only 22 difference, so it's a wash.A 48 big ring will create no issues with your front derailer.

If you want a brand recommendation, I'm a fan of the Real "Ultimate" middle and outer chainrings, which are nickel-plated 7075 aluminum... very wear-resistant, and very gouge-resistant. They are probably some of the most expensive aluminum rings you can buy, but considering how long they last, I still believe they are a good value in the long run. http://www.real-design.com/rings.html

If you do end up changing cassettes as well, you might think about using a 12-28 7-speed cassette to boost your high gear. The 12T is about 7% higher than your 13T. To get a 7% jump by changing the chainrings, you would need to go from 46 teeth to about 50 teeth. A new chain is probably in order at this point, too. Too bad there isn't a 12-32T 7sp combo, that would be very nice.

Thank-you Pokey for the info. You are absolutely correct that there are 2 different bolt circles for the rings. I don't care much about the inner chain-ring so I want to replace only the big and middle ring. Where is a good place to order these from? Will any 5 bolt Shimano ATB fit?
Sorry Pokey, if I don't know much about the MTB stuff or possibly other issues in the future. I tend to ask alot of questions since I do not know everything. Perhaps I may be able to answer a question for you some day, if not in mechanics maybe with training.?

Thanks MechBgon, You are a wealth of knowledge.
I will go with a 12-28, 7-speed cassette. I'll get a new chain also.
How about my rings? I want to finally ditch the Bio-Pace. I want to replace only the middle and big ring considering the bolt circle difference and I don't care about the inner ring. Will any 5 bolt Shimano pattern fit for the middle and large ring?

Shimano did make some other 5-bolt patterns too, so look for ones listed for 110mm BCD as your best guarantee of getting the type that fits your cranks. I have a "full-size-drive" crankset too, and I prefer them... with more teeth, the chainrings wear out more slowly, and statistically they are less prone to chainsuck. They'll pry my 110/74 XTR cranks from my COLD DEAD FINGERS! ;)

If you are getting a new cassette and also new middle and outer chainrings, what I would do is get the 12-28T cassette, for the 7% boost in high gear back there, and get 36T and 48T chainrings, so you also get an additional 4% boost in your high gear due to the bigger chainring. 48 x 12 is a pretty fair road gear, and as pokey mentioned, the derailleurs will not be stressed by this. You still get the versatile 36T middle chainring.

If you try this out and decide you could still use even more high gear for the road, then you could get a 11-30 cassette for another ~8% faster top gear. On an old cassette body such as what your hubs come with, a spacer would be needed behind the big cog to accomplish this, and sometimes a slight re-spacing of the axle is needed to keep the chain clear of the frame, so I think the 12T is the best bet to start with. Good luck! :)

Fife,
OK, the chainring thing seems resolved, but I have another question. Are you sure you have a freehub/cassette or could it be a freewheel? Have you ever had it off?
Regards,
Raymond

Are you sure you have a freehub/cassette or could it be a freewheel? Have you ever had it off?
I just took it off for the first time since the bike was new in +-85'. It's a 6 speed freehub/cassette held on with the small cog being threaded as a lock-ring. The cog set has three small bolts screwed in from the back side to hold them together. I would like to change it to 7 speed.

6-speed! :eek: That does make things more complicated. If you are planning to move from 6sp, may I suggest going to 8sp instead of 7? 8sp is not really dramatically expensive and you can pick from a wider range of gearing options. Here is my suggestion:

New 8sp shift levers (GripShift, Shimano Revo-twist, Shimano RapidFire/EZ-Fire, as you like)
Possibly new grips
New brake and shift cables/housings (at this point it's surely time for them, anyway)
New 7/8/9sp compatible rear derailleur such as DeoreLX (the 6sp derailleurs are not compatible, having a different parallelogram slant angle) New 8sp cassette (Sachs 11-32 8sp or Shimano 11-30 8sp, killer high gear)
New 8sp Sachs chain such as PC-58
Have the rear wheel rebuilt with a Shimano 8/9sp-compatible road hub such as Shimano 105 (you have 130mm frame spacing, hence the road hub). Make sure to get it built with DT or Wheelsmith-brand spokes.
Alternately, instead of having the wheel rebuilt, buy a good-quality new wheel with an 8/9sp-comaptible Shimano 135mm hub, and have the frame cold-set to 135mm width. Again, if you want it to last, demand DT or Wheelsmith spokes (there are some pre-built wheels available with DT).
New chainrings as desired; 36-46 is good with the 11T in back, giving a 5% higher gear than even a 48x12 comboObviously this is a big investment in money, and I leave it to you to decide if it's worth it. :)

Originally posted by The Fife

I just took it off for the first time since the bike was new in +-85'. It's a 6 speed freehub/cassette held on with the small cog being threaded as a lock-ring. The cog set has three small bolts screwed in from the back side to hold them together. I would like to change it to 7 speed. There is little or nothing you can do with that 6 speed cassette. They are no longer available)except maybe from aplace like www.loosescrews.com) and the spline pattern is different than 7,8, and 9 speed.Better to plan on a new hub or wheel.

I'd like to replace the large Bio-Pace chain-ring to a 48, 110 BC. They seem to be hard to find. I've given up on replacing the cassette.

Originally posted by The Fife
I'd like to replace the large Bio-Pace chain-ring to a 48, 110 BC. They seem to be hard to find. I've given up on replacing the cassette. ... Biopace is no more.use a standard 48 in a 110 BCD. try www.branfordbike.com catalogue. for about any chainring available. www.nashbar.com may have 110 48s