trek y-22 for donor? Picture included
- Thread starter Doug Burton
- Start date
Doug Burton
Zen MBB Master
Hi Randy,
Normally I'd warn you about seat height, but based on the position of your seat in the picture, you're probably pretty tall. You can relax the rear shock to bring the crossbar height down some.
My principal concern is with the seat bracket digging into the carbon fiber. The Cruzbike seat pan bracket is a semi-circular saddle that fits over the top tube, and rides on a rubber insulator. This insulation would be critical in the case of a carbon fiber frame becuase they don't take point loading or fretting loads very well.
Others may have some more perspective, please bring all questions, and welcome!
Best,
Normally I'd warn you about seat height, but based on the position of your seat in the picture, you're probably pretty tall. You can relax the rear shock to bring the crossbar height down some.
My principal concern is with the seat bracket digging into the carbon fiber. The Cruzbike seat pan bracket is a semi-circular saddle that fits over the top tube, and rides on a rubber insulator. This insulation would be critical in the case of a carbon fiber frame becuase they don't take point loading or fretting loads very well.
Others may have some more perspective, please bring all questions, and welcome!
Best,
I think drilling into Carbon fiber would be a pretty bad idea, but that's just my gut reaction. There's got to be a way to attach a cruzbike seat with enough chafe gear underneath that it won't rub a hole. But Doug's point about point loading is well taken- finding a way to spread the load may be hte more imporant consideration for this application.
Re: trek y-22 for donor? [Y-11 lessons learned]
1) You don't want to drill holes in a CF frame unless you add some sort of reinforcement or boss to distribute the load. Point loads are very bad and cause catastrophic failure. You need to distribute the load over the greatest surface area possible.
2) The problem with the Y-11 frame as a donor is the non-constant curvature of the frame cross section -- it's an ovaloid. I ended up rebending the seat mount bracket to get as close as I could. Then, I wrapped baking parchment (serving as release paper) around the frame, applied a layer of Gorilla Glue (a rigid expending urethane foam) to the seat mount bracket, clamped it to the frame in the right spot and let it set up overnight. I then peeled the parchment paper off and wirebrushed off the extra foam residue. (You can see the pale yellow foam line with bubbles in the upper left photo.) The intent was to minimize point loading. I also modified the front hose clamp clearance hole to be oriented towards the front. I still used the rubber shim as supplied in the kit between the frame and the modified seat mount bracket. Additionally, I cut up a couple pieces of old license plate, pounded them flat and used some sections of old inner tube as shims between the license plate sections and the frame. This worked very well for over a year and a half in temperatures from 100F down to -15F as a commuter bike.
3) The Y-11 rear end is rather thick, especially compared to the FWD brackets in the Curzbike kit. Plan on putting a couple of flat washers on the outside of the axle stack (see the lower right photo) to allow your QR to develop enough clamping force. One nice collateral effect of the FWD conversion is the elimination of the pogo motion when pedaling. The Marzocchi air/oil shocks were very comfortable on potholed roads, crossing RR tracks and going off curbs.
4) I don't know what the frame size of the Y-11 I converted is, but it measures 21.5-in from the center of the bottom bracket to the top of the seat post clamp unloaded. It's my wife's mountain bike and she's 5' 7". As converted, the Cruzbike seat base to ground measurement was 31". Once I got on and the suspension sagged, this dropped to 28.5". I'm 6' 2", 210# and have an x-seam of 46.5". Under extremely heavy braking, I nosed over a few too many times. This convinced me to remove the kit and convert the bike back to a mountain bike. The high seat height and resulting high CG is a problem with this conversion.
5) One of the other big problems was knee clearance to the brake levers and shifters. I had to try several component mixes of riser bars and angled stems to get enough clearance.
6) The donor bike weight was 30# and the Cruzbike kit added another 10#. It took me a couple of weeks riding in longer and longer sessions to get comfortable enough to take it out in traffic on my 4 mile commute. The best comment I got on it was from a 12-year-old hispanic kid -- Oooh! That bike is sooo pimp!
1) You don't want to drill holes in a CF frame unless you add some sort of reinforcement or boss to distribute the load. Point loads are very bad and cause catastrophic failure. You need to distribute the load over the greatest surface area possible.
2) The problem with the Y-11 frame as a donor is the non-constant curvature of the frame cross section -- it's an ovaloid. I ended up rebending the seat mount bracket to get as close as I could. Then, I wrapped baking parchment (serving as release paper) around the frame, applied a layer of Gorilla Glue (a rigid expending urethane foam) to the seat mount bracket, clamped it to the frame in the right spot and let it set up overnight. I then peeled the parchment paper off and wirebrushed off the extra foam residue. (You can see the pale yellow foam line with bubbles in the upper left photo.) The intent was to minimize point loading. I also modified the front hose clamp clearance hole to be oriented towards the front. I still used the rubber shim as supplied in the kit between the frame and the modified seat mount bracket. Additionally, I cut up a couple pieces of old license plate, pounded them flat and used some sections of old inner tube as shims between the license plate sections and the frame. This worked very well for over a year and a half in temperatures from 100F down to -15F as a commuter bike.
3) The Y-11 rear end is rather thick, especially compared to the FWD brackets in the Curzbike kit. Plan on putting a couple of flat washers on the outside of the axle stack (see the lower right photo) to allow your QR to develop enough clamping force. One nice collateral effect of the FWD conversion is the elimination of the pogo motion when pedaling. The Marzocchi air/oil shocks were very comfortable on potholed roads, crossing RR tracks and going off curbs.
4) I don't know what the frame size of the Y-11 I converted is, but it measures 21.5-in from the center of the bottom bracket to the top of the seat post clamp unloaded. It's my wife's mountain bike and she's 5' 7". As converted, the Cruzbike seat base to ground measurement was 31". Once I got on and the suspension sagged, this dropped to 28.5". I'm 6' 2", 210# and have an x-seam of 46.5". Under extremely heavy braking, I nosed over a few too many times. This convinced me to remove the kit and convert the bike back to a mountain bike. The high seat height and resulting high CG is a problem with this conversion.
5) One of the other big problems was knee clearance to the brake levers and shifters. I had to try several component mixes of riser bars and angled stems to get enough clearance.
6) The donor bike weight was 30# and the Cruzbike kit added another 10#. It took me a couple of weeks riding in longer and longer sessions to get comfortable enough to take it out in traffic on my 4 mile commute. The best comment I got on it was from a 12-year-old hispanic kid -- Oooh! That bike is sooo pimp!
WhiteSilvio
Well-Known Member
So that's 40 pounds all up. Or 18.2kg
