Classic & Vintage - 1986 Centurion Dave Scott Ironman Geometry
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I'm having trouble finding geometry specs on any of the Centurion Ironman bikes. I'm riding a 1986 Centurion Dave Scott Ironman right now (not the Expert or Master). I can't really tell the differences from my Schwinn Prologue frame, which has 74.5 ST and 73 HT angles (both frames are 56cm) qualitatively, but I would guess that the Centurion has a more relaxed seat tube angle. Here's a link to some pictures and specs for reference:
FYI, the serial # is KG511572.
I'm going to take all those "vintage parts" off the Centurion and swap them with the "race parts" on my Schwinn since the frame is damaged and I want something reliable to train on. (Alas, the Schwinn will be confined to campus bike duties...)
I may try to get one of those angle measuring ruler things and just measure manually...
EDIT: I guess there was not an actual question (with a "?") when I wrote this, but here it is: What is the geometry of this Centurion frame?
10-09-08, 06:13 PM
I don't know the answer, but your going to put Shimano 600 on a campus bike???
Please buy a REALLY good lock.
for some reason, 6400 600 doesn't sell for much.
but use a bigger protractor, since we know that the top tube is pretty much parallel to the ground.
10-09-08, 06:49 PM
I believe 73 and 73
edit: well, the '84 TA's were, according to AWs scan. I just assumed Centurion changed the name but not the geometry.
10-09-08, 10:06 PM
Just by eye, I guess that Scott is pretty steep. I'd believe your numbers, between 74 and 75 for the front and rear. To get a real good measurement you need the actual bike, a good instrument, and a steady hand.
with my riding buds, I compare frame angles by parking the two bikes close together and eyeballing the tubes. You can't see actual angle of course, but i feel you can definitely see when two tubes are not parallel, such as caused by a difference in seat tube angle.
I think if they look the same side by side, then they are practically the same, barring measurment with a really good angle measuring guage.
10-09-08, 10:08 PM
I happen to have the geometry specs somewhere, from Bicycle Guide magazine. I will look.
10-09-08, 10:17 PM
this? Per Bicycle Guide, the frame specs only changed in 1989, but the test bike they got didn't have the changes.
I've ridden the Comp TA, the '86 Ironman, '88 Master, '89 Expert and Master, and the '88 Carbon. I have the fit the same, they ride about the same, other than component differences.
73ST, 74.5 HT...interesting. I have noticed it steers a little quicker but I get a little less power than my Schwinn (74.5ST, 73HT). Thanks for posting that, robbie.
10-10-08, 07:33 AM
steering quickness will be based on the combination of head angle and fork offset, using the formula for trail, not just on head tube. It's also affected by wheelbase and handlebar extension plus stem extension, so I don't think you can just isolate head angle.
it's hard to assess and hard to predict - same for the sense of power.
I've been trying to get a handle (;)) on this for a while - trail is the key number in determining quickness.
I've found this to be a pretty good explaination:
An interesting thing is that you can have a slow handling (ie a stable bike) with a steep head angle if it has more trail, due to low fork offset, than a bike with a shallow head angle which has less trail. The shallow head angle bike will have more fork offset, making it look like some sort of soft riding touring bike, yet it will have quick steering. Basically, looks can be deceiving.
This is really interesting. A circa circa 1985/1986 Centurion Ironman with a 1987 Kawamura serial number and a 1988 600 Ultegra group!
As for angles, these will change depending the year and size of the frame. For instance, the 1987 specs claim 74 degree parallel angles, but this is for a 58cm frame. A 56cm was 74 head and 73.5 seat. Typically, the head angle will stay the same for a particular year, but seat angles will get shallower as frames get smaller.
If you really want to know the angles, the only way to be sure is to measure them. I suggest you dig out your protractor, some boxboard, a ruler and a hobby knife. Cut several pieces of pie in 1/2 degree increments for 71-75 degrees and take a bite out of the apex, to clear the lugs. Make sure you mark the templates with the angles before you cut them out.
As previously stated, there's more to steering quickness than just head angle.
10-10-08, 06:37 PM
All these numbers....
I can only say from experience, my steel Ironman bikes ride pretty much the same.
The '88 Carbon is a different animal altogether, running Campy wheels that make a difference, too.
I find no difference between a 58cm Comp TA and a 58cm '86 Ironman as far as riding, but the Comp TA has a better chain and is smoother somewhow.
I put a CF fork on my '89 Expert, and it's a whole different bike.
Aesthetics aside, I like an Ironman with a CF fork for a good combination of ride/handling, differing wheel sets notwithstanding, guys.
There, I've used a couple of big words, and thanks for the info on this thread. I had no clue but this is really interesting.
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