Friday, May 12, 2006

Geometry comparisons between Iron Horse Azure and Iron Horse Hollowpoint

I've been jonesing for an Iron Horse Azure ever since they released it. This is their first attempt at an XC specific platform.

A little history. I bought and sold my first XC suspension bike within a few months because the suspension action bobbed to much. For the second bike I researched to no end end. I finally settled on a used 2004 Iron Horse Hollowpoint. You can read my review of it here.

I adore this bike. It climbs like nobody's business, and handles so well for the aggressive XC of the mid-Atlantic and Virginia. However it is on the heavy side, and it's design was a compromise between XC and trail. The HP was split into two different lines for 2005: the Azure and the MKIII. The Azure took on the XC roles and the MKIII took on the trail. Everything I've read on it says that it is a pure rocket for XC, and climbs even better than the HP.

I am totally sold on the DW-Link. So much so that I won't even consider any other type of bike.

However, when the Azure first came out I was critical of two things.
1) Weight.
It is still on the heavier side for a pure XC racer. Iron horse qualifies it more as an enduro type of bike.

2) Top tube lengths. The top tube lengths are much shorter on the Azure than compared to the HP.

I was torn between what size Azure would work for me. I currently run a 15" HP. With the shorter top tube lengths I was torn between a 15 or 17" of the Azure. I am all of 5'4.5" so it seem funny to even be considering a 17", and at first it seemed that I'd have to run a 60-65mm stem.

Long top tubes and short stems are definitely something I've moved towards, and I currently run a 80mm on the HP. But 60 seemed too extreme.

After Nate got an Azure for his wife, I asked for some more dimensions of the bike to look closer at it.

I plugged some numbers into BikeCad which is a free CAD program for bicycles. You can enter in fairly detailed dimensions and it will give you some dimensions of the handlebar as referenced off the BB axle.

An important difference between the two frames is the HP has a 71.4 Seat Tube angle and the Azure has a more typical 73. This can really mess with the reach. See this article for why.

Somethings I'm not totally sure about. It allows you to specify the main triangle via Effective Top tube Length and the angle of the top tube, or by Front Center (distance from BB to front axle) and Head Tube length. I know the ETT, but not the angle of the top tube. I measured the Front center and Head Tube length and plugged it in, but when I checked what it had calculated for the ETT it is was off.

Regardless I do know that the measurement from my saddle tip to the handlebar is 49.5cm. And I know that my saddle setback is 50mm. So the distance from BB to handlebar is around 44.5cm.


The above shows the HP with an 80mm 6degree stem

After plugging in some numbers for a 17" Azure I got the below
This is with a 75mm 6degree stem. I can also use a 70mm 0 degree with a change in spacers too.

One thing with these CAD things is you can get close but it is NO substitute for reality. Things like headsets, tires, forks, etc. change things up in real life. But this does get you close.

What it tells me is that a 17" Azure at the current geometry is perfect for me. A 70-75mm stem is ideal IMHO. Several prominent people agree such as Gene Hamilton of and pro XC racer and former downhiller Salem Mazzawy

The 17" has a longer top tube than 15" which also creates a longer wheelbase

Salem said Traditional wisdom is a long wheel base is slower turning, but my experience is that with the stability of the long wheelbase, I can maintain grip at more extreme lean angles, and actually corner faster, although it does require a little more aggressive technique (fall with your hip vs. the more intuitive push with your arms). Also, the bb is a bit lower on the Azure, so it is that much more stable than the Hollowpoint.

I have to apologize to Iron Horse for being critical of their top tube lengths and saying they were too short. I'm pretty stoked that the 17" looks perfect for me. Standover really isn't an issue because the top tubes are sloped so much. Though it still seems funny that someone my height would be getting a 17" frame.

They only thing holding me back from grabbing a closeout 2005 Azure is that sitting on the fence mentality to see if they worked some diet magic on the 2007 Azure. Or did something really crazy and made a full carbon version.

Weight is one of those funny things. You see people talking about their sub 23lb or even sub 22-21lb Blur XC or Specialized, or soon enough Carbon Anthems. I'm running a 27lb HP and climbing better than ever. With the Azure I'd be at 26lbs. Not bad, but I can't post on the weight weenie forum with that! But still. If IH wants to play the marketing game and go head to head with the established XC race horses, they have got to get to the same weight ranges, regardless of how awesome the DW link is.

the man himself _dw said that A Blur XC (15") weighs in at 5.2 lbs with shock. An Azure (15") weighs 5.98 lbs with shock
.8 lbs.

Analytic cycling just on a basic calculation shows a .49 second savings with a .8lb difference

Which would probably be more than overcome with the pedaling efficiency of the DW-Link
*** I stand put in my place.

But I'm still a weight weenie!


At 2:50 PM, Anonymous Anonymous said...


It looks like the Azure is not quite ready for prime time for your needs, IMHO.

-You'd loose travel
-Only estimated 1 pound lighter
-Downtime from parts swaps/upgrades/new part exchanges
-Lower BB
-2005 would have you purchasing a "first production model year" frame, with none of the on-going refinements and all of the beta-bugs of 1st year models

-Nothing fills the heart like a "new bike"
-You'd loose 1 pound. Lighter is faster
-You'd lighten your wallet a bit

Per your calculations, if 0.8# extra would only cost you 0.49 seconds, how much more realistically would the additional 0.2# of your current rig cost you? And could you possible save 0.2# for the projected cost of the frame exchange with other parts that can be later moved to the next-gen Azure, which can't be far off?

Keep up the good work. I love the blog.


-capt pearl

At 2:58 PM, Blogger ashwinearl said...

Good points
travel loss isn't always a bad thing. The travel from an XC perspective is probably better on the Azure than the HP. Tighter, more efficient. But still compliant when needed like at DW-link bikes.

Lower BB is good from a stability point of view. bad from hitting rocks with pedals, but combined with the slightly shorter travel it is a good thing for cornering and downhilling.

2005 frame is actually identical to the 2006. They were late on production so the 2005 release is actually the 2006 frame. Identical except for color. The only major difference is the Factory frame which is made in the USA, it is slightly lighter and also come with a boutique price tag and sold out for 2005.

I'll be knee deep into bike build when the custom roadie gets here, and I probably should just keep my focus on training and racing unlike last year when I got focused on the whole dually thing in the middle of the year. The big downside is just time, and loss of focus on other things. And the my wife thinking I'm spending all this $$ on frames when it is just a little bit when you factor in selling the other bike.

However if there is no significant change in the 2007 model, I'm hoping they cut the price on the 2005 one more time, then I'll scoop it up. Unless they are all gone

At 9:05 AM, Anonymous Anonymous said...

I'm sure DW would give you his opinion on which size would be better for you.

My buddy is the same size as you, and he felt pretty good on a medium epic frame that had a tt of 22.5" when he went to a 90mm stem. He usually liked 21.5" tt. Not sure what tt he would prefer...but I will ask him which way he would go now...s or med.

My gut feeling is that a 15" would be better for you, but it will have that shorter tt feeling. The good thing you probably will throw it around easier and be able to jumps better. If your style is to ride from the center of the bike the longer tt might be the way to go. Nothing worse than riding a bike too small....what a conundrum!

...test ride?

At 9:27 AM, Anonymous Anonymous said...

You appear to be running too much set back, currently.
State your height, inseam, length of your femur, and I'll tell you if a 17" Azure is the right size. I own one.

You will love the way it pedals.

At 3:48 PM, Blogger ashwinearl said...

My saddle setback is 5.0cm. This was determined on a Serotta (existing) bike fit using the Hollowpoint. It is a WTB Rocket V Race saddle (with a Thomson 0 setback post)

The position is pretty close to knee over pedal spindle, though I can tolerate a knee forward of the spindle as well.

my inseam is 77.5cm
Femur length is 41cm (though this was measured years ago by someone who didn't have a strong fit or medical background)

I also have a hardtail with a 22.3 Effective top tube according to the builder (though when I measured it with a tape it came out longer) with a 70mm stem on it and the fit is equivalant to my Hollowpoint

I really like the handling of a short stem/long top tube bike, with the grips level with the top of the saddle, or maybe a tad lower.

At 6:12 PM, Anonymous Anonymous said...

You need a 17", but you already knew that. No-brainer.

You're giving up efficency on transitions and spin, with your saddle set as it is--if you have become accustomed to a high degree of mechanical leverage, you'd be better off moving forward and setting your cleats back. You'll need a stem longer than 70mm in order to weight the front sufficiently. Whatever--you're the one pushing the pedals.

At 7:26 PM, Blogger ashwinearl said...

I'm curious what you mean by "You're giving up efficency on transitions and spin, with your saddle set as it is--if you have become accustomed to a high degree of mechanical leverage, you'd be better off moving forward and setting your cleats back."

Would your suggestion be to move the saddle forward (less setback) and put the knee farther forward of KOPS? My cleats are already set very far back to help out with Hot foot, and I also like the control that farther back cleat provides on the downstroke. I am definitely more of a spinner than a slow cadence hammerer.

My current HP has an 80mm stem, the hardtail has a 70mm stem. My skills are improving a lot, but I know what you mean by not weighting the front end enough. It's more mental with me to put weight on the front in a downhill corner, vs getting too far back out of fear.

At 8:52 AM, Anonymous Anonymous said...

I'd suggest that you again measure your knee<>spindle angle. Given your femur length and the HP ST angle, you s/n be at KPOS. But if you are, then don't bother messing with your setback. You'll want a minimum 90-100mm stem on the Azure (estimate). Try a longer saddle, with less flare at the back.

At 9:12 AM, Anonymous site said...

What namely you're saying is a terrible mistake.


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