# BB and crankset help.



## bones72751 (Sep 1, 2010)

Ok well I'm trying to figure out what I need to get. Please no judgemental remarks in this thread, I only want helpful answers. I'm upgrading my Schwinn aluminum comp. I want to put an acera crankset on, replacing the SR Suntour. I measured the spindle at 126mm, but all that's offered in a sealed type is 127.5mm. Would that work? Also I've read something about proper chainline being 47.5mm. Do I need the same size spindle that I have now or will a different length be needed when changing to a different crankset?

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## rlouder (Jun 26, 2007)

According to the tech docs at shimano, the 341 and 361 need a 123mm spindle. The 361-8 and 391-8 use a 126 spindle, but those appear to be oem models. Might be difficult to locate one without going through a bike store.

http://techdocs.shimano.com/techdoc...RTMENT<>ast_id=1408474395181679&bmUID=i.QYpt2

The item description on this one confirms:

http://cgi.ebay.com/Shimano-Acera-M...Cycling_Parts_Accessories&hash=item1e609d1d3d


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## zebrahum (Jun 29, 2005)

I would highly, highly recommend going to a crank with removable chainrings. Unless I'm mistaken, that Acera crank has riveted chainrings. That means that if you wear out your rings in a year or two then you'll be replacing the crank once again instead of just bolting on new rings. Try to find a Deore level crank.

I don't know why you're changing your crank and BB, but I can say it's worth it to spend a bit more.


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## bad mechanic (Jun 21, 2006)

If you're hell bent on upgrading it, then it doesn't make much sense to spend money on a little upgrade, since you don't gain much and will upgrade it again in the future. Buy something nice now, so you don't buy it twice down the road.


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## jtrops (Aug 4, 2008)

You need to match your bottom bracket spindle to the crankset. That being said, chainline on a triple front is not terribly critical as long as it's within a few mm's. So, unless you are particular about getting a crankset spec'd for a 126 BB, you should get the appropriate BB when you get the crankset. 

The chainline issue becomes more important if you have a derailleur that has a narrow H/L limit range, or if you have a bike with an oversized seat tube that puts the derailleur closer to the chainwheels. As a general rule I like to run the narrowest spindle I can to reduce the q factor.

The move from your SR Suntour crankset to the acera is not really an upgrade. It's more of a lateral move. Your cranks are a little on the heavy side, but pretty stiff. I have a pair on my beater single speed, and aside from having to be careful with pedal installation (soft aluminum) they haven't been anything but reliable.

For an upgrade I would look for something with: Aluminum rings for the middle and large position, Forged arms, and Lighter. I'm not a weight weenie by any measure, but with cranks, up to a point, lighter translates to better materials and build.


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## bones72751 (Sep 1, 2010)

Ok, well I do have a truvativ isoflow crankset, but I'd have to buy new chainrings. Also the ring side arm is bent, is there a good way of straightening it?

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## jtrops (Aug 4, 2008)

Yup, it looks like it's slotted. In that case see if you can move the wheel forward a bit to give you the room for your new cog.


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## AndrwSwitch (Nov 8, 2007)

I think once the arm on a crank is bent, it's done.

I don't know what price you saw on the Acera. Probably less than this

http://www.cycleclubsports.com/p-54091-shimano-deore-m590-crankset-170mm-crankarms-223244t.aspx

but the basic Deore crankset is a pretty kickass deal, IMO. This one includes the new bottom bracket.


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## bones72751 (Sep 1, 2010)

Would that work with an 8 speed rear?

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## AndrwSwitch (Nov 8, 2007)

The crank doesn't care what the back of your drivetrain looks like. Should be fine. The very worst that might happen is that you might find you get a little noise using an 8-speed chain, and want to go to a 9-speed. I don't think that would happen, though.


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## jpeters (Nov 19, 2010)

I would go with the new Deore crank they are a really good crank for the money.


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## bones72751 (Sep 1, 2010)

So if I get a crankset that comes with the bottom bracket, it WILL work?

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## pfox90 (Aug 8, 2010)

AndrwSwitch said:


> I think once the arm on a crank is bent, it's done.


You can bend them back with a pipe and cloth wrapped around it. Isn't the best way. But that is how we fixed a bent arm that was hitting the chainstay and chain on a POS bike. Don't really recommend it as I don't know how it's going to work down the road.. but they didn't want to get a new one.


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## bones72751 (Sep 1, 2010)

What about something like this?
http://www.amazon.com/gp/aw/d/B0052U8DTI/ref=mp_s_a_3?qid=1308098180&sr=8-3

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## pfox90 (Aug 8, 2010)

bones72751 said:


> So if I get a crankset that comes with the bottom bracket, it WILL work?
> 
> Sent from my VM670 using tapatalk


I wouldn't say that. The chain line might not work.


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## bones72751 (Sep 1, 2010)

Ok, so there's not really a way to know what bb to get with a new crankset? I'd rather not have to go through a lbs cause all my local ones have outrageous markup. 

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## AndrwSwitch (Nov 8, 2007)

Bicycle drivetrains are a pain in the butt in many ways.

Almost all mountain bikes have bottom bracket shells in two different sizes: 68mm English and 73mm English. There are some others, but I'm confident that a bike you pulled a Suntour crank off of is English threaded.

The recent Shimano external bottom bracket cranksets are compatible with both widths, by including or omitting spacers. They're also compatible with E-type front derailleurs and chain guides, same deal.

There has been a change in chainline in the last several years, so an old enough front derailleur, or a really low-end off-brand one might not work with a new crank. For more recent stuff, it's fine. What bike do you have?

I'd want to read the service manual for a Saint or Hone (like in your link) crankset, because those are DH/FR lines, and some bikes for that purpose have yet another bottom bracket shell size. Stuff in the Deore/LX/SLX/XT/XTR lineup is going to work on the more common sizes. I'm not saying the Hone crankset won't work - just find the manual for it.

EDIT: Also - all cranksets should say in the manual what bottom bracket should go with them. Many mountain bike cranksets will give the sizes required for each shell type.


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## bones72751 (Sep 1, 2010)

AndrwSwitch said:


> Bicycle drivetrains are a pain in the butt in many ways.
> 
> Almost all mountain bikes have bottom bracket shells in two different sizes: 68mm English and 73mm English. There are some others, but I'm confident that a bike you pulled a Suntour crank off of is English threaded.
> 
> ...


I've got a '10 model Schwinn aluminum comp. Its a Walmart bike, but its one of the better ones. I got it cheap enough, and all my upgrades thusfar were free. I've got a total if $125 in it, so I figured a crankset wouldn't be an overboard upgrade.

So, I just need to look at tech sheets and find out what bb is needed for a chosen crankset? I don't habe to worry about it not fitting the bike as long as its 68/73mm English thread? The hone I looked at is a 68/73, so it should work?

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## rlouder (Jun 26, 2007)

I wouldn't put an expensive crankset on a 170 dollar bike. Besides costing more, you will also need an additional tool with the deore or hone cranksets mentioned. Get the least expensive thing you can find that will work and save your money for a better bike. If there is nothing wrong with the suntour, ride the bike and enjoy it. Even if you want some upgrades, you would get more for your money on something besides the crankset.

You would need a new bb with the isoflow, and it would cost more to replace the rings than it costs.

If you want detailed help, you will have to make two measurements: 

Bottom bracket shell length: Turn your bike upside down and measure across the shell. As AS mentioned, it's most likely 68mm or 73mm.

Chainline: Measure the distance from the center of the middle chain ring to the center of the seat post. It's likely 47.5mm or 50mm.

If you can't find a direct replacement so you can use your bb.... One fairly inexpensive option is the alivio. It's on sale for $25 at amazon. Price match it at jenson and get one of their $10 bb's.


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## bones72751 (Sep 1, 2010)

rlouder said:


> I wouldn't put an expensive crankset on a 170 dollar bike. Besides costing more, you will also need an additional tool with the deore or hone cranksets mentioned. Get the least expensive thing you can find that will work and save your money for a better bike.
> 
> You would need a new bb with the isoflow, and it would cost more to replace the rings than it costs.
> 
> ...


Thing is I most likely wont get another bike any time in the next 10 years. Also, I know it costs more to upgrade than to buy in the long run, but I'm fine with that. I'd can easier spend $100 next month or so than spend $1000... ever. I've looked at the alivio, but then I saw the deore and liked it. Then saw the hone, for cheaper, and liked it too. The reason I wanna get a new bb is because mine isn't a sealed type, and that's what I want. Just had to figure out how to figure out what bb I need.

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## AndrwSwitch (Nov 8, 2007)

bones72751 said:


> I've got a '10 model Schwinn aluminum comp. Its a Walmart bike, but its one of the better ones. I got it cheap enough, and all my upgrades thusfar were free. I've got a total if $125 in it, so I figured a crankset wouldn't be an overboard upgrade.
> 
> So, I just need to look at tech sheets and find out what bb is needed for a chosen crankset? I don't habe to worry about it not fitting the bike as long as its 68/73mm English thread? The hone I looked at is a 68/73, so it should work?
> 
> Sent from my VM670 using tapatalk


As an upgrade, cranksets are not great, no matter the bike. But when you need a new one to keep the bike rolling, you don't get a choice, and it's often cheaper to replace the whole thing than to replace the rings, or a couple rings and the bottom bracket, etc.

I'm a little confused though - you're replacing a SR Suntour crankset but the destroyed one is the Truvativ Isoflow? Is the Suntour crankset damaged? They're disposable, so if it is, once again you don't get a choice about replacement...


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## bones72751 (Sep 1, 2010)

AndrwSwitch said:


> As an upgrade, cranksets are not great, no matter the bike. But when you need a new one to keep the bike rolling, you don't get a choice, and it's often cheaper to replace the whole thing than to replace the rings, or a couple rings and the bottom bracket, etc.
> 
> I'm a little confused though - you're replacing a SR Suntour crankset but the destroyed one is the Truvativ Isoflow? Is the Suntour crankset damaged? They're disposable, so if it is, once again you don't get a choice about replacement...


Sorry, didn't mean to be confusing. When I bought the bike, the guy gave me all the good parts left from a frame damaged giant. The parts included the truvativ crankset minus the rings, although the crankset was bent. The stock crankset on my bike is the suntour, which is the only stock part left on the bike. That's part of the reason I wanna upgrade, so I can say I built it.

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## AndrwSwitch (Nov 8, 2007)

bones72751 said:


> The reason I wanna get a new bb is because mine isn't a sealed type, and that's what I want.


This is a big uh-oh.

Can you post a picture of your bottom bracket? You don't necessarily need to pull the crank arms off if you don't have the tool - just a shot from the outside is enough.

Some dept. store bikes use a different bottom bracket standard.


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## bones72751 (Sep 1, 2010)

Here you go. I've had a sealed/external bb (whatever it's technical name is) installed before, but the spindle wasn't long enough for the current crankset so I swapped back. 















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## rlouder (Jun 26, 2007)

bones72751 said:


> (whatever it's technical name is)


Probably a cartridge bb - typically used with square or splined cranksets. The deore and hone are called external bearing.

If you had a cartridge bb installed, then the deore or hone should work. I would skip the hone because, as mentioned, it's heavier. The deore looks good. The lx at jenson is very popular if you want to spend a little more.

https://www.jensonusa.com/store/product/CR303A00-Shimano+Lx+Fc-M582+Crankset.aspx

Cartridge bb
................


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## bones72751 (Sep 1, 2010)

rlouder said:


> Probably a cartridge bb - typically used with square or splined cranksets. The deore and hone are called external bearing.
> 
> If you had a cartridge bb installed, then the deore or hone should work. I would skip the hone because, as mentioned, it's heavier. The deore looks good. The lx at jenson is very popular if you want to spend a little more.
> 
> ...


Gotcha. I've been looking at cartridges type bb's. But, I want a hollowtech, just don't wanna spend a whole lot. I found the hone for like 70 bucks on amazon. Also, how much difference will I feel between a 170 and 175 crank arm?

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## jtrops (Aug 4, 2008)

*


bones72751 said:



Gotcha. I've been looking at cartridges type bb's. But, I want a hollowtech, just don't wanna spend a whole lot. I found the hone for like 70 bucks on amazon. Also, how much difference will I feel between a 170 and 175 crank arm?

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Click to expand...

If you want an upgrade that you will notice immediately I would get lighter tires. Then I would ride the bike as hard as I could to try to hurt the cranks.

In the mean time, I would learn about cranks and bottom brackets. Maybe pick up a crank extractor, pull your cranks, repack your BB, and put it all back together. Or swap out the current BB with a UN26 for $12.

I would bet that a 127.5 cartrdge BB like a UN26 would do fine for your existing crankset. Most cartridge BB's are symmetric, while cup and cone BB's are often asymmetric. Before I bought a new BB for your bike I would measure the amount of spindle sticking out on the fixed cup side, and compare it to the amound on the adj. cup side. If it's the same it is symetric. If there is more on the fixed cup side it's asymmetric. If it is a symmetric BB you will only be altering your current chainline by .75mm's if you go with the 127.5. On a geared bike that isn't nearly enough to be concerned about.*


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## bones72751 (Sep 1, 2010)

jtrops said:


> *
> 
> If you want an upgrade that you will notice immediately I would get lighter tires. Then I would ride the bike as hard as I could to try to hurt the cranks.
> 
> ...


*

My tires aren't even worn out yet. I've got kenda nevegal on the from and a kenda blue groove on the rear. What would suggest I get? I've already repacked and greased my bb, but I may get the un26 just so I don't have to KEEP repacking and greasing it every few rides. While I haven't measures each side, they look the same.

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## jpeters (Nov 19, 2010)

Get a crank from ebay but you will need to get tools as well but its always good to have tools. If you want to upgrade the walmart bike thats fine with me if you get enough good parts you can always get a new frame later. I would not upgrade a Walmart bike but to each his own. I think you can remove the current bottom bracket with pliers I got one off of my city bike like yours with pliers. Have a look at sheldon browns web page for directions on changing cranks.

http://shop.ebay.com/i.html?_from=R...mano+deore+crankset&_sacat=See-All-Categories

http://cgi.ebay.com/PARK-BIKE-BICYC...aultDomain_0&hash=item43a7bf2d37#ht_770wt_698

http://cgi.ebay.com/New-Park-Tool-B...640?pt=LH_DefaultDomain_0&hash=item27bbaa38f8

http://cgi.ebay.com/Super-B-37pc-Ho...997?pt=LH_DefaultDomain_0&hash=item5d2f22564d


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## jpeters (Nov 19, 2010)

bones72751 said:


> My tires aren't even worn out yet. I've got kenda nevegal on the from and a kenda blue groove on the rear. What would suggest I get? I've already repacked and greased my bb, but I may get the un26 just so I don't have to KEEP repacking and greasing it every few rides. While I haven't measures each side, they look the same.
> 
> Sent from my VM670 using tapatalk


If you want to upgrade I would go through ebay and get some new deore parts. Your front dr is crap and brakes are not so.

http://shop.ebay.com/i.html?_from=R40&_trksid=m570.l2736&_nkw=deore


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## jtrops (Aug 4, 2008)

bones72751 said:


> My tires aren't even worn out yet. I've got kenda nevegal on the from and a kenda blue groove on the rear. What would suggest I get? I've already repacked and greased my bb, but I may get the un26 just so I don't have to KEEP repacking and greasing it every few rides. While I haven't measures each side, they look the same.
> 
> Sent from my VM670 using tapatalk


I really do understand the desire, and need for upgrading. So, I'm not trying to tell you not to do it. I'm just suggesting that the performance gain will be slight, if even noticeable. In fact, you may realize your frame has a lot of flex once you put stiffer cranks on it.

First of all, your tires are fine, but if you wanted to shed some weight a set of "small block 8's" would do it. The 8's are a great tire for Colorado, but if you are riding in an area with a lot of soft, muddy stuff you probably want a more aggressive tread.

Other parts that will offer an immediate improvement in the ride would be: brake pads, grips, saddle, and clipless pedals. As I said before getting a good adjustment can make low quality parts work fairly well, and to this end you may need better cables/housing. This isn't as flashy as getting slick brakes, or cranks, but it's practical. It would be interesting to see if you are really riding this bike in 10 years. My guess is that you won't be.


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## AndrwSwitch (Nov 8, 2007)

My "most senior" bike is over ten years old.

It started life reasonably high-end. It's a Reynolds steel road bike with a carbon fork and Shimano 105 build.

There's actually a lot of original stuff on it. But there's also a fair number of things that have been replaced. Nothing lasts forever, including some things I scoffed at the idea of ever wearing out - I recently finished building new rims onto the wheels, and the rear derailleur has gotten sloppy. It's also been through many chains, a few cassettes, several tires, and is on its second set of shifters, although I swapped those more for the hood shape of the newer ones than for wear. This bike did spend a couple years in storage, while I was trying something different with my life and cycling didn't really fit.

My mountain bike is four years old. Not much of its stock build is still on it. It started life relatively cheap - it's an '07 Hardrock Comp - and between the desire to improve performance and stuff wearing out, I've changed out a ton of stuff. Off-road riding is tough on gear.

My oldest bike is a mid-'80s road bike that was never "all that." Of the parts that were on it when I bought it, I still have the frameset itself, crank arms, seat post, headset, stem, handlebars, brake levers, one shifter, and the derailleurs. Both wheels are replacements, including one I built from parts because of a change in the spacing standard of road frames, and all the wear parts are new either because of damage to the freewheel mechanism or because I use it to ride up hills with loads, and wanted smaller chain rings.

Nothing lasts forever, and when people are still riding ten-year-old mountain bikes, usually it means one of a couple things - the bike is a garage queen, it gets ridden mainly on the road, or the person replaces things as they wear out or suffer mishaps, and little to none of the original build is left. FWIW, when I have a little money to spare on the project and if he still has it, I want to buy the MTB I rode in college back from the friend I sold it to when my priorities shifted. It may get a rigid fork as a replacement for the RockShox Pilot it has now, but I'll try to keep the rest of the build with its pretty basic 3x8 drivetrain and V-brakes. That bike has spent the last eight years in his parents garage, behind some boxes. So it fits in the garage queen category.

FWIW, I totally agree with the decision to replace your Suntour crankset. Sealed vs. unsealed bottom brackets are a huge performance difference, whether you just look at performance without all the maintenance you're doing, or you include maintenance as an aspect of a part's performance. It may make sense to replace the bottom bracket only, if the crankset itself is still fine, but if it's the kind of with riveted rings or a nonstandard BCD, you'll have to throw it out as soon as you wear out or damage a ring.

Something else you may consider doing sooner, rather than later, if you want to chip away at a nicer bike - start with the frame. There are a few heavy but serviceable frames kicking around for $100 on the 'net, and some really beautiful NOS frames start being available from $200. Check out bikeman.com, pricepoint.com, performancebike.com, nashbar.com. I don't think the frame is actually a hugely important place to try to upgrade most existing bikes, but if you're going to worry about weight at any point in time, the $/gram for frames is pretty favorable compared to other parts, and there are a few other parts that have to be compatible. So doing a nice build and then transferring to a new frame makes less sense to me than getting the new frame, figuring out where the compatibility issues are and addressing them, and then transferring the rest of the build all at once - your bike is down for an afternoon, instead of the several weeks people often take to sort out compatibility problems when they do it in the other order.


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## bones72751 (Sep 1, 2010)

Ok, let me rephrase... if my bike isn't broken in 10 years, I wont replace it, lol. I don't have a problem with my frame, its pretty stiff. So far my frond derailleur hasn't missed a beat, but I'll replace it when it does. I've got most any tools I need at work, and I know how to work on my own bike. Everything I've done so far has been without the help of a lbs. My brakes a a little sub-par, but I've heard there are a couple different types of pads that help. I will soon be getting grips and cables, although I see that as more maintenance than upgrade, they're getting worn out. I still want a new crankset and bb too, what do y'all think of the alivio? I don't do any hardcore riding, just the local trails and singletrack. 

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## jtrops (Aug 4, 2008)

I do recommend getting a sealed cartridge BB. From the way you describe your riding even a UN26 may last the life of the bike. 

As for your crankset, you'll just have to decide that one. Between my various bikes I have mostly really nice cranksets, and yet last year I rode my beater SS with the Suntour cranks every week. Those cranks took a serious beating. I did impromptu crank grabs (bad timing going into slots) with them, and while they look worse for the wear, they are still solid. 

I got them for free. If I had to buy them I probably would have found a deal on some old, maybe used, cranks at least a few grades better. These cranks have been reliable, and functional. That's about all you could ask from cheap parts. I don't see the Alivio being a great step up. It may be a bit nicer in some ways, but not enough.

As for the rings. Mine are 104mm bcd, and the outer, and middle rings were bolted on. The inner ring was riveted to the middle one, and I punched the rivets out when I did my ghetto SS conversion. I have a tendency to land on my chainrings, so the bash guard is a nice bit of extra weight that builds confidence.


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## bones72751 (Sep 1, 2010)

That suntour is still a step up from mine. Mine are all riveted rings. I think I'm definitely gonna upgrade it, if for nothing else just to say I did. 

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## bones72751 (Sep 1, 2010)

Any one know anything about the shimano fc-m443 octalink? I've got one in my cart at amazon for 40 w/ bb. I read the tech sheet on it and its applicable derailleur group was deore stuff...

Also, I have 170mm crank arms right now. Would there be any clearance issues with a 175mm set? Also would there be much of a difference in how it rides?

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## jtrops (Aug 4, 2008)

The M443 is in the "non series" category in the Shimano parts line, but the part number puts it in the same range as the Alivio. I don't think it will be much different than Alivio. 

Going from 170 to 175 generally doesn't cause any problems. The two issues that could arise would be pedal strikes, and toe clearance.

If your bike has a lower than normal BB, you may have more pedal strikes in slots, or rocky areas. The bigger problem would be toe clearance for the front wheel. Some bikes that have short ETT, bring the front wheel so close that your foot will hit the tire occasionally. 

Performance in this case is a trade off of spinning speed, and climbing torque. You may think that it's not a big difference, but it really does matter. If you are a spinner you might appreciate the smaller pedal circle of the 170's. If you ride in a lot of steep terrain you may like the longer lever you get from the 175's. This is a really personal choice, and I'm sure if you search a little you'll see that there are hundreds of good points to be made on both sides of the issue. Since you've been riding 170's you might want to try the 175's just to see how you like them. I'm pretty sure that you're going to dial in a nicer bike before long. The interest and motivation you are showing already makes it a good bet.


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## bones72751 (Sep 1, 2010)

Don't get me wrong, I'd love to get a nicer bike, but all signs lead to no in the near future. I'm working with a Walmart paycheck and have a 9 month old daughter on top of rent, 2 cells, 2 cars, and hopefully will be buying a house sometime soon. But, I like the bike I've got right now. It does good on the trails I ride, and it gives me a project to tinker with.

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