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Discussion Starter · #1 ·
This is my first road bike:

I just got a new 08 Trek 2.1 with a compact crankset. I didn't know it had 170mm crank arms untill I got it home. I have a 34" inseam and I run 175's on my MTB.

I topped out the 50/39 crank set tonight on the strait; 50/11 I think is the fastest ratio. Anyways I was peddling hard but I still could pedal harder.

I deffently want a larger 53 or 56T double to put on it, but it has a 110 bolt pattern. Or I just need to buy a new crankset. Should I go with 175 crank arms? I kinda feel like I'm spinning too much with the 170s. But It is a compact frame also... Any advise?
 

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I have a 32" inseam and like 172.5mm cranks best. With your inseam, I'd think that either 172.5 or 175 would be good. I think LeMond had an 84cm inseam (a little over 33") and ran 175s.

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Discussion Starter · #4 ·
Thanks, I think I will go with a 175 crank and 53T. I think the BB I have is ISIS, what crankset under $100 will fit? I've been looking online but all the sets never say what BB they are for. I don't plan on replacing the BB.
 

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Are you sure you didn't buy a frame that was too small? Seems really unusual to get a bike with 170mm cranks for someone with a 34" inseam... unless you have really odd proportions.

Are you pushing a 50x11 on flats? What kind of cadence do you consider unacceptable? I mean, you shouldn't have any problems riding 35mph with a 50x11.
 

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Discussion Starter · #6 · (Edited)
I'm all leg!!! I'm 5' 10.75" tall

I bought a 56cm, It seemed to feel better then the normal 56 I rode also.

I'm not sure how fast I was going, I need to get my Sigma 1606 on there with the cadence too. I'm totally new to Road Biking. But I must say that the bike is really fast compared to my mtb on the road...And I've been riding my mtb on the road for years, also some trail.

If you guys can point out some cranksets that will work with the 108mm ISIS BB that would be cool. The bike store is 40miles form here, don't plan on going back for a while.
 

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Seriously--if you bought a 56cm and got a 170mm, take it back to the bike shop and get the right sized cranks (for free). That is totally ridiculous. You should never get a 170mm on anything larger than about 52cm.

Your shop should be happy to make the change for a non-compact crank (for free). Compact cranks are much more popular and easier to sell. Shimano makes very nice cranks for the $$.
 

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Are you sure that you have an 11 tooth on your cassete and not a 12? A 50 tooth chainring and an 11 will go faster at the same cadance than a 53x12 which is what most normal road bikes come with. If you really like to sprint you could do the 53x11 which would give you a lot of top end speed. If you have a 34 inseam you should be on a 175 crank, a 170 isn't even close, a few might go 172.5, but most would be on a 175 its a no brainer. :thumbsup:
 

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Discussion Starter · #9 ·
Its an 11, I just counted. I found a new 105 crankset double and 5500 v1 BB (68x109mm) for about $83 I think I'm going to get. It will match my rear Der. I just have to make sure I have the right BB tools, to take the ISIS out and but the octalink v1 in. haha....

Same torque on the BB as mountain bikes? I ususally use teflon tape then put a thin layer of grease over that.

My friend today was telling me to just leave it, but i dont want to go back and fourth from a 175 on my mtb to 170 on a rb... :eek:
 

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"I topped out the 50/39 crank set tonight on the strait"
"I was peddling hard but I still could pedal harder."

If you can hammer like that on the flats, you'll be a Cat 2 in no time.
Let's see...50X11 = 40+ mph.

"I deffently want a larger 53 or 56T double to put on it, but it has a 110 bolt pattern. Or I just need to buy a new crankset. Should I go with 175 crank arms? I kinda feel like I'm spinning too much with the 170s. But It is a compact frame also... Any advise?"

Return to the shop where you bought your new bike, and ask them if they can exchange cranks, because you're ready to go Pro.
 

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Discussion Starter · #11 ·
I looked all over the net for some 175mm, 110 BCD cranks, and I could not find any to work with the Bontrager ISIS BB.

I know the bike store I bought the bike from won't have an exact price replacement. And It would be weeks before they got something. They were actually building this bike when i got there. I even called another store in the other direction and they didnt have anything cheap. LoL they wanted to sell me $265 crankset.

Turns out I need 3 tools to do the replacement job: CWP-6C crank puller, BBT-18, and a TL-UN74-S bottom bracket tool. Really sucks when you need 3 tools that total $42. That pushes me up to $140 shipped for everything :( maybe I should have bought a used bike....

Anyways thanks for the advice people, If you have a cheaper way or can point me to some 175mm cranks that will fit please do!!!!!!

I will put the speedo on tonight and see what mph I can get out of her. I'll report back ;)
 

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Tmaster: What bike did you get--and from what shop? Seriously, I can't think of ANY reputable brand of bike that would come with a 170mm on a 56cm. My guess is they screwed up at the factory--or someone at the shop wanted longer crank arms and gave you the short end of the stick.

If the shop doesn't have the right parts (and is too lazy to work it out with the manufacturer), call the manufacturer and work with them directly. I'm sure they'd love to know about shops that represent their brand so poorly.
 

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Discussion Starter · #13 ·
I'm sure it probably was like that from the factory. There wasn't any other new 2.1s or even 1.5s on the floor. I Think I will call the Bontrager company tomorrow.

I'm sure the shop would switch them out for me. The guy said i could get fitted and had two free tune ups when i come back off and on. I'm just not planning on going up there again for at least a few weeks or more. But i really want to get it right for me right now!
 

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Discussion Starter · #14 ·
I got my 1606L on and put in 2108(83") for the wheel circum...

I got up to 32.02 in the last gear sitting down pedaling pretty hard. Wind is anoying. I'm afrade to stand up and give it to her. I can tell the difference between the 170 and 175. seems like my legs are limited. The front end is a lot twitcyer then my mtb. lol. I'm used to the wide strait flat MTB bar to and the huge tires. The 23c tires are scary if im going to sprint it out. lol....... :eek:
 

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speed

That is pretty good for a 50x11 because if I remember right I think 30.5 mph is at a 90 cadance in 50x11 on Sheldon's gear chart. You will get used to the 23 mm tires and the bars, make sure they are at least 42's, 44's might even feel better for you. Keep hammering away. :thumbsup:
 

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I am the same height, and maybe a 1/2" shorter inseam, and I ride 172.5. I probably could be on a 175, but it is really difficult to tell any difference and there is always a chance of knee pain with too long of a crank. Your road bike is typically going to have a shorter crank than your mountain bike. If you look at bike geometry spec charts you will see that most mid size mtb are 175 while road is 172.5 (what your bike should have came specd with) and large mtb may be 180 and road bikes 175.

I would contact the company and find out if they can switch to the appropriate crank as they should. You should be fine with a 172.5...like me you are on that borderline and that is personal preference. If you prefer to not spin at a higher cadence, then the 175 might be your ticket...I like to spin as much as possible.

If you are topping out at 32 then you are more than ok with your current ratio. I run a 50/12 as my top end gear and max out about 38...any faster and I start to pee myself on the roads in N. MN. Even if I wanted to go faster it is so seldom that I am fine with what I got.

You are probably just going through the same thing I do when I get a new bike...trying to find every little thing that may not be perfect...I think we all do.

I would get the longer crank though. 170 is ridiculous (although is what I run on my ss.
 

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Discussion Starter · #17 ·
I actually measured myself a few more times and im 33.5" inseam. I thought i was 34, but the tape measure must have bowed some months ago when i measured. I used a strait yard stick this time.

After looking at the size charts I decided to go with a 172.5 crank set that I found a good deal on. An FSA and only 600g too; double. Also it will fit on my BB so I don't have to mess with that. My ratio will be 53/11 now.

The bike is starting to feel better now that I have ridden it 4 times, and a few weeks I should be pretty used to it by then. I'm just not used to spinning. Riding the MTB on the road I'm always in the large front chainring moving steady.

I'm sure i can go faster then 32. When I get used to the bike and actually stand up and go all out I'm hoping for close to 40. Heck, Even on my 24lb mtb, i was able to get up to 30mph on the strait, 44T, knobby tires, etc.

I'll report back on the speed :D
 

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what about for the short people... I'm 5'5" with ~28.5" inseam. I have a 170mm crank and my knees seem to come up higher than i've seen for others. My thigh is close to parallel to the ground at the top of the stroke, and with my heel on the pedal my leg is straight at the bottom of the stroke. Some online calculators would suggest a 155 or 160mm crank for my leg length, is anyone using something that low?
 
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