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Can I run 170mm Cranks on a new geometry Demo 8?

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TomBigmac

Chimp
May 31, 2009
58
0
I'm swapping my downhill frame for something lower and slacker (been on Giants every year for a long time). My 2011 Specialized Demo is on it's way and I'll just put all my current kit on it. I always have preferred 170mm cranks as I'm 6'3 and find 165mm piddly and hard to generate power. I'm a bit worried with the extremely low BB that I'm going to have trouble running these. The 2010 I rode felt great but I can definately tell the difference in crank length.

Forget it and smash 170mm to bits?

Swap for 165mm cranks and get used to them?
 
yd35

yd35

Monkey
Oct 28, 2008
741
61
NY
I have a 2010 Demo 8 and it is low at 13.4" static. I believe the 2011 is the same. I have 165 cranks, and you have to be very aware of your crank position at all times. Pedalling also has to be strategic, or else you'll slam your crank, pedal, toe into a rock. The point to this rambling is that I recommend going 165. I've never tried 170 on the Demo, but I'm guessing that it would make life more difficult.
 
frorider

frorider

Monkey
Jul 21, 2004
971
20
cali
don't forget the influence of pedal selection here. thin cross section, and a shape that isn't a big huge square can help minimize rock hits. i like the point1 podiums.
 
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TomBigmac

Chimp
May 31, 2009
58
0
I have Canfield Crampons already, they're also smashed to bits and if they got into that state on my Glory then perhaps I do need 165's!
 
F

freeridefool

Monkey
Jun 17, 2006
647
0
medford, or
I have an 07 demo. I know its has a bit higher bb but I ran 175's all year, with crampons. My demo is slamed past the safe level on my 40, and i run 2.5 minnions. pay attention where you pedal and you should be fine.
 
Uncle Cliffy

Uncle Cliffy

Turbo Monkey
Jan 28, 2008
4,490
42
Southern Oregon
Like most have already said, you may be fine with 170's

But, I went with 165's for my 951 and I think they're just fine length-wise. (I'm 6'2" with a 34 inseam.) In fact, I barely notice a difference jumping between my 170mm equiped SS to the 165mm 951. Maybe the BB width factors into that...?
 
F

freeridefool

Monkey
Jun 17, 2006
647
0
medford, or
Uncle Cliffy said:
Like most have already said, you may be fine with 170's

But, I went with 165's for my 951 and I think they're just fine length-wise. (I'm 6'2" with a 34 inseam.) In fact, I barely notice a difference jumping between my 170mm equiped SS to the 165mm 951. Maybe the BB width factors into that...?
Click to expand...
Cliff are you talking about riding them to the mail box or actual riding? We need to ride soon so I can see the mythical 951 in action.
 
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BmxConvert

Monkey
Aug 6, 2007
715
0
Longview, Washington
My first few runs on a borrowed demo I hit the pedals a bit, but on my Demo my pedals look darn close to new. I don't find myself hitting much.
Give it a try, you'll likely be just fine.
 
P

project_d

Chimp
Dec 15, 2009
93
0
SoCal
Think about it...is 5mm going to make that much of a difference in regards to clearance? No, we're talking about 5mm...about 0.20". I ran 175mm cranks on my old DH bike, and that had a pretty low BB with me on it, and there was VERY little difference in regards to hitting rocks.

But what I can tell you is that being 6'3", I liked the longer cranks. I was able to get more power out of my pedalling, and they put me in a better attack position. I think crank length is really more dependant upon your height.
 
P.T.W

P.T.W

Monkey
May 6, 2007
599
0
christchurch nz
project_d said:
Think about it...is 5mm going to make that much of a difference in regards to clearance? No, we're talking about 5mm...about 0.20". I ran 175mm cranks on my old DH bike, and that had a pretty low BB with me on it, and there was VERY little difference in regards to hitting rocks.

But what I can tell you is that being 6'3", I liked the longer cranks. I was able to get more power out of my pedalling, and they put me in a better attack position. I think crank length is really more dependant upon your height.
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Are you sure you where getting more power??? Like you said yourself "is 5mm going to make that much of a difference"?
It goes both ways:thumb:
 
JCL

JCL

Monkey
Aug 31, 2008
696
0
5mm can make the difference between clipping a pedal or not.

If you don't think every millimeter of clearance matters on a Demo have a look at Brendan and Sams chainring/bash.
 
HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Admittedly, I run 165s on my DH bike, but it's also a lot lower than a Demo. So I'd say, sure, you can get away with it.
 
HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
JCL said:
What bike has "a lot lower' BB than a Demo?
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Nothing production that I know of. ;)


It's a Draco Vigilante. 12.9" BB. Yes, I'm serious. It's a little lower than ideal, but it rails, and I've gotten used to it to the point where I don't hit many pedals. It's also a hair on the short side travel wise at 7.5", so that helps some too.
 
HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Verskis said:
My Jamis Diablo has about 12.6" BB. That is a little too low, even with 165mm cranks and only 7 inches of travel, but I can live with it.
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You sure about that? I thought they were way higher stock, I'm thinking either you've got a shorter than intended shock on there, or your measurement's a little off.

Edit: I'm wrong, Jamis' website actually says they've got a 12.6" BB. Holy hell that's low.
 
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HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,586
2,018
Seattle
Uncle Cliffy said:
Cool stuff!
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Thanks. It's a super fun bike, very comfortable at speed, great in the air. Suspension's really good too. It's a little bit of a handful at times in tight stuff, but nothing terrible. It's pretty stiff, but the lower link has a little give to it. I've been thinking about making a stiffer one, but haven't gotten around to it.
 
DirtyMike

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,437
1,017
My own world inside my head
Wa-Aw said:
It's 5mm, any difference would most probably be placebo.
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Agreed.... Most people I find that go to a 165 over a 170 actually have a different need for it, they have short legs. Combine that with the low seat heights we run in the DH world, its better for the knees, thats were 5mm can make a big difference.

kidwoo said:
You ever switched back and forth between lengths?


It does make a difference.
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I have, and as far as clearance, I will make this bet. I will install aset of cranks on your bike..... You go ride and tell me what length they are.


5mm, think about it... Go look at a 5mm wrench if you have to.... its nothing, you will sag a bike more than 5mm by leaning forward a tough, or by not taking a good **** before riding.......


project_d said:
Think about it...is 5mm going to make that much of a difference in regards to clearance? No, we're talking about 5mm...about 0.20". I ran 175mm cranks on my old DH bike, and that had a pretty low BB with me on it, and there was VERY little difference in regards to hitting rocks.

But what I can tell you is that being 6'3", I liked the longer cranks. I was able to get more power out of my pedalling, and they put me in a better attack position. I think crank length is really more dependant upon your height.
Click to expand...

Close, height makes a difference, but like listed above, you have to take into account leg length over height<usually go hand in hand> Body position on the bike, leg extension and flexion. Over working the knees is a terible thing. 5mm is nothing for clearance, any of these low ass bikes you have to watch were you pedal as it is, reguardless of crank length.





Bottom line, go with the 170's you have. Your gonna smack pedals for awhile reguardless.
 
kidwoo

kidwoo

Artisanal Tweet Curator
Aug 25, 2003
42,146
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DirtyMike said:
I have, and as far as clearance, I will make this bet. I will install aset of cranks on your bike..... You go ride and tell me what length they are.
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I will take that bet any day of the week.

You act like I've never done this several times over several bikes over many many years.

I fully believe you may not be able to tell the difference. That's cool. But I'll gladly take your money, because some of us can.

I know what 5mm looks like. I also know what the margin is between grazing a rock and flat out nailing a rock. And 5mm is well within that difference.

This same argument applies to a quarter inch in bar width or bottom bracket height too. Those are also small increments that make a significant difference in the way a bike handles.
 
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DirtyMike

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,437
1,017
My own world inside my head
kidwoo said:
I will take that bet any day of the week.

You act like I've never done this several times over several bikes over many many years.

I fully believe you may not be able to tell the difference. That's cool. But I'll gladly take your money, because some of us can.

I know what 5mm looks like. I also know what the margin is between grazing a rock and flat out nailing a rock. And 5mm is well within that difference.

This same argument applies to a quarter inch in bar width or bottom bracket height too. Those are also small increments that make a significant difference in the way a bike handles.
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BTW, last person to take the bet had no clue I put two different size cranks on their bike, one was 165, one was 170.

You are absolutly right though about the small incriments drastically changing how a bike rides, I see that all the time, 1/4 in on the bars can make a huge difference either up or down, few MM on the seat can completly change the "feel" of the bike as well as the performance factor, there is indeed alot more to fitting a bike properly than people think. Like I said originally four years ago, three years ago, two years ago, one year ago, and now.... Most people end up liking the 165's for downhill because their body position, and leg length matches up better.

We are talking everyday riders here, alot of people are now going from a bike with 14.5 or 15 in bb to a 13.5 or lower...... Doesnt matter what cranks are on it, they are going to smack the pedals and cranks into rocks. Its truly just something you have to get used to when you get a new bike.

But seriously, if your ever in socal and want to take my challenge, We will see if you can pick off what size cranks I put on your ride.


Not trying to slam ya, or knock anything, or say you cant ride or anything like that...... Cause you are right, small changes like that can seriously and dramatically change how the bikes feels/handles/ performs......I mean bike performance goes hand in hand with feel.... The better you feel on the bike, the better your going to perform on it.

In no way am I saying 165's are a bad thing, just to do it for the right reasons. I still stand by my statement that most people that are out tehre are shorter, smaller, shorter legs than I have, and 165's are probably a great idea for them. 170's fit my legs, When I went to a lower bike, I had to get used to it, I rarely smack my pedals anymore, but man that first ride was about every turn out there.
 
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kidwoo

kidwoo

Artisanal Tweet Curator
Aug 25, 2003
42,146
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DirtyMike said:
BTW, last person to take the bet had no clue I put two different size cranks on their bike, one was 165, one was 170.
Click to expand...

I'll bet you 50 bucks that person is a retard :D

I would have liked to have been a part of that experiment though :rofl:


I agree with all your points. The only thing I disagree with is a blanket statement that NO ONE knows what they're talking about with regards to crank length because you know a FEW PEOPLE who have proven they don't.

Know what I mean?
 
M

MDJ

Monkey
Dec 15, 2005
669
0
San Jose, CA
I would take that bet as well. I've run all different crank lengths on all differernt types of bikes and can easily tell the difference - especially when you throw 165s on.

Edit - although I agree most people probably wouldn't notice the difference, and yes, 165s are good for a lot of people.
 
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yopaulie

yopaulie

Monkey
Jun 4, 2009
165
7
NH
Am I missing something here....we are talking 5mm forward and back not down. I don’t think 5mm more in crank length is going to make enough of a difference to even decide crank length.
 
Wa-Aw

Wa-Aw

Monkey
Jul 30, 2010
354
0
Philippines
I have gone back and forth between two cranks that were 170mm and 175mm, which for years I had assumed both were 175mm. Didn't feel the difference. Looking back the 175mm may have felt slightly more powerful but I'm thinking that's in the realm of placebo.
 
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