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Cannondale ST fork conundrum
I have a 1991 Cannondale ST600 and I love the bike however the fork has been causing some trouble for me. The dia-compe 986 brakes are at the limit of their adjustment to fit the original wheels. Now using a set of wheels wider than the originals it is almost impossible to adjust them correctly. The posts are too high.
I've noticed in the catalog the ST600 uses a different fork than what I have on the bike. It looks like Cannondale reached into their parts bins to equip these bikes and it really seems that the fork was intended for 27" wheels instead of 700c. The axle to crown also seems off. I've measured ~412mm a-t-c. I haven't put a level on the top tube yet, but it sure seems to slope upwards because of this tall fork. Looking at images of other 91 ST600s with the unicrown fork and they seem to have this slope as well. The fork in the catalog looks significantly shorter, but by how much I don't know. I've been on the hunt for a replacement fork and am even considering having something custom made for the frame. I'm wondering if anyone on here has an ST600 with the correct, per the catalog, fork who can measure the distance of the axle to crown length? 1991 ST1000 should be the same geometry as well, so if you have one of these the measurement would be useful to me as well! https://cimg7.ibsrv.net/gimg/bikefor...c94422f64d.jpg https://cimg0.ibsrv.net/gimg/bikefor...218093c078.jpg |
measure from ground to the bottom of the headset lower cup... then let air out of the tire until the bike's top tube looks level... re-measure... there's the difference you'll need to level the bike...
also... use either a machinist' protractor or a cell phone angle app to check the head tube angle with the bike in the "lower tire pressure " stance... see if that spec matches the bike spec. as called out by Cannondale... adjust if needed. Re-measure the ground-headset cup distance... do the math, find your new fork. Don't forget to consider needed Tire Clearance in the vertical direction... oh, and that sidewalk is not level to the wall's grid... ;) |
Catalog page shows a fully sloping crown fork. Your bike shows a unicrown fork that style often makes for a longer fork.
post placement is really from the axle. the difference between 27” and 700c is typically 4mm. |
Is that fork a replacement?
Looking at the photo, the front wheel is lower than the rear wheel, but the top tube is higher at the front. So thinking that the fork is from a 27" bike is not far fetched. |
Originally Posted by maddog34
(Post 23396727)
measure from ground to the bottom of the headset lower cup... then let air out of the tire until the bike's top tube looks level... re-measure... there's the difference you'll need to level the bike...
also... use either a machinist' protractor or a cell phone angle app to check the head tube angle with the bike in the "lower tire pressure " stance... see if that spec matches the bike spec. as called out by Cannondale... adjust if needed. Re-measure the ground-headset cup distance... do the math, find your new fork. Don't forget to consider needed Tire Clearance in the vertical direction... oh, and that sidewalk is not level to the wall's grid... ;) I'm aware the ground is unlevel in my image, but it seems odd in all of the other examples that I can find the visible slope is consistent. https://cimg9.ibsrv.net/gimg/bikefor...1d069d8b26.jpg https://cimg0.ibsrv.net/gimg/bikefor...4a9a20de69.jpg And then a 1991 ST1000 as a reference with a visibly shorter fork and perfectly level top tube https://cimg1.ibsrv.net/gimg/bikefor...6afd9af2c1.jpg |
Was the photo of the 1991 ST1000 at the bottom of post 5 taken with the same camera? The upper photos show what appears to be more distortion toward the sides and bottom of the photos (vertical lines appear to lean outward, bottom stairs appear slightly curved).
Edit: here's a more extreme example of the kind of funhouse mirror-looking distortion I mean, copied from a recent post in the C&V "Are You Looking For One Of These?" thread. https://images.craigslist.org/00t0t_...t2_600x450.jpg |
Originally Posted by theblackbullet
(Post 23396661)
I've noticed in the catalog the ST600 uses a different fork than what I have on the bike. It looks like Cannondale reached into their parts bins to equip these bikes and it really seems that the fork was intended for 27" wheels instead of 700c.
Often, too, the individual bike photographed for the catalog was one of the very first of the production run, or even one of the previous years' model (a 1990 "dressed" as a 91) so some of the details are not as pictured. Could just be a change of brake arms is in order. A 90s MTB style like the DiaCompe 988 has a pretty big adjustment range, or something modern like the Avid Shortys would get the adjustment you need. |
My '90 ST600 came with 27" wheels, but I put in 700's and the adjustment worked fine. It has the "vintage style" fork bridge.
https://cimg0.ibsrv.net/gimg/bikefor...fb7832ee50.jpg My '91 SH800 has a unicrown fork, came with 700's and the clearance looks like yours. https://cimg2.ibsrv.net/gimg/bikefor...885e187ef7.jpg |
Originally Posted by Chuckk
(Post 23399853)
My '90 ST600 came with 27" wheels, but I put in 700's and the adjustment worked fine. It has the "vintage style" fork bridge.
https://cimg0.ibsrv.net/gimg/bikefor...fb7832ee50.jpg My '91 SH800 has a unicrown fork, came with 700's and the clearance looks like yours. |
The 92 T1000 came with the steel fork designed for 700c, also with Diacompe canti's.
Crappy film pic. https://cimg8.ibsrv.net/gimg/bikefor...754cb2a60f.jpg |
Originally Posted by Chuckk
(Post 23401104)
Will do, but it's at the back of the pile.
Meanwhile, look at the difference in the bend between your fork and the one in the catalog. But the curve looks just like that on my H bike! Or maybe it hit a wall in the past. I agree 100%! It definitely looks like the same fork as the hybrid. I do not believe the unicrown fork spec matches the lugged fork. The unicrown measures ~412mm atc whereas I believe the lugged fork will likely be between 385-395mm atc, just hoping to get some confirmation. |
I don't know if this will help you but......
My 88 ST600 converted to 700c measures 370mm from the top of the fork crown to the center of the axle, ridden hard, well worn and well loved. https://cimg4.ibsrv.net/gimg/bikefor...5ad82e9c65.jpg |
Originally Posted by OTS
(Post 23401909)
I don't know if this will help you but......
My 88 ST600 converted to 700c measures 370mm from the top of the fork crown to the center of the axle, ridden hard, well worn and well loved. |
Zombie thread. Sorry. I am close to picking up a 1991 ST600 and I noticed the same difference in forks compared to the ST1000 of that year. The ST1000 has a gorgeous taper crown fork, but the ST600 had a unicrown fork on the production bike even though the catalog photo looks to be using the ST1000 fork. It does look like they simply grabbed one of the hybrid forks and ran with it to get the cost down on the ST600. Sadly, it seems like that unicrown fork throws the geometry off a bit.
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Well, here she is and she definitely rides a bit higher in the front. I have seen a few builds of these that look better when you throw on the fattest tires possible, which I intend to do.
https://cimg1.ibsrv.net/gimg/bikefor...ac1a126624.jpg |
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