Here are the results for my comparative work on the factory shocks from '03 and '05.
I'm doing this because...
1. I would prefer a heavier spring in my '05 shock as my preferred for "one up" riding is 6. I'd like 3 or four "clicks" above that for riding "two up" with some gear.
2. I'm broke. Penske/Ohlins, while wonderful, are off the table. If I had that money, I'd look into a new bike, not spending $1k on a 19 year old bike with 50k+ miles.
3. Excellent opportunity to learn, especially for my daughter, about free sag, rider sag, etc.
4. I like data. Working through all of this is fun for me. Yes, I'm strange, lol...
Notes -
1. - This is a summary graph of a LOT of data. I have graphs for preload heights, rider sag as % of travel, free sag as % of rider sag, etc. etc. If you have a specific question, just let me know and I'll post it.
2. - Rider weight, geared up, is 172 pounds.
3. - The free length of the '03 spring (157 mm) is 6 mm longer than the '05 spring (151 mm). Also, the installed length of the '03 shock (151 mm) is 6 mm longer than the '05 shock (145 mm). Other than free length, there is no obvious difference between the '03 spring and '05 spring. The wire diameter (.505 in.) is identical as is the number of active coils, etc., which surprised me as my previous experience with the '03 combination was that the spring was way to heavy. Is it possible that the rebound damping (non-adjustable) on the '03 shock was stiff enough to keep the shock compressed, during operation, further down in its operating range, resulting in a stiffer ride?
Results -
Sag was measured (*) at 1, 3, 5 and 7 for each combination as well as 6 (preferred) on the '05 combination.
Note that the rider sag is essentially identical for the '05 combination set on "6" and the '03 spring on the '05 shock set at "1" which is where the bike sits today. A 30 mile ride on a variety of roads confirm that the ride quality between the "6" on the '05 shock is essentially identical to the '03 spring on the '05 shock set at 1.
Next steps - While I accomplished my goal of having additional preload options above 6, the result is "preferred" is a 1. I'd like something below that for a random occasion of piling up miles on the interstate or if my daughter rides the bike.
I will double check when I next disassemble but I believe the difference in installed height is in the spring seat for each shock which are not interchangeable between the two shocks. If I can duplicate the 157 mm installed height on the '05 shock I will do so, but I doubt it is possible. Therefore, I am fabricating spring shims to install between the spring seat and the adjustment collar to use with the '05 spring/shock combination to reset the "6" to a "3" or so. Will report back when that work is done.
Here's a shot of my homemade spring compressor arrangement. It worked well but will do some refining if I keep doing this. I'd like to duplicate the arrangement on the right on the left. Just works better. (The white duct tape is there to attempt to prevent scratching the spring.)
* - I'm confident in my sag measurements. Each data point was created using several measurements (bike being compressed and bike rebounding) and were repeatable.
I'm doing this because...
1. I would prefer a heavier spring in my '05 shock as my preferred for "one up" riding is 6. I'd like 3 or four "clicks" above that for riding "two up" with some gear.
2. I'm broke. Penske/Ohlins, while wonderful, are off the table. If I had that money, I'd look into a new bike, not spending $1k on a 19 year old bike with 50k+ miles.
3. Excellent opportunity to learn, especially for my daughter, about free sag, rider sag, etc.
4. I like data. Working through all of this is fun for me. Yes, I'm strange, lol...
Notes -
1. - This is a summary graph of a LOT of data. I have graphs for preload heights, rider sag as % of travel, free sag as % of rider sag, etc. etc. If you have a specific question, just let me know and I'll post it.
2. - Rider weight, geared up, is 172 pounds.
3. - The free length of the '03 spring (157 mm) is 6 mm longer than the '05 spring (151 mm). Also, the installed length of the '03 shock (151 mm) is 6 mm longer than the '05 shock (145 mm). Other than free length, there is no obvious difference between the '03 spring and '05 spring. The wire diameter (.505 in.) is identical as is the number of active coils, etc., which surprised me as my previous experience with the '03 combination was that the spring was way to heavy. Is it possible that the rebound damping (non-adjustable) on the '03 shock was stiff enough to keep the shock compressed, during operation, further down in its operating range, resulting in a stiffer ride?
Results -
Sag was measured (*) at 1, 3, 5 and 7 for each combination as well as 6 (preferred) on the '05 combination.
Note that the rider sag is essentially identical for the '05 combination set on "6" and the '03 spring on the '05 shock set at "1" which is where the bike sits today. A 30 mile ride on a variety of roads confirm that the ride quality between the "6" on the '05 shock is essentially identical to the '03 spring on the '05 shock set at 1.
Next steps - While I accomplished my goal of having additional preload options above 6, the result is "preferred" is a 1. I'd like something below that for a random occasion of piling up miles on the interstate or if my daughter rides the bike.
I will double check when I next disassemble but I believe the difference in installed height is in the spring seat for each shock which are not interchangeable between the two shocks. If I can duplicate the 157 mm installed height on the '05 shock I will do so, but I doubt it is possible. Therefore, I am fabricating spring shims to install between the spring seat and the adjustment collar to use with the '05 spring/shock combination to reset the "6" to a "3" or so. Will report back when that work is done.
Here's a shot of my homemade spring compressor arrangement. It worked well but will do some refining if I keep doing this. I'd like to duplicate the arrangement on the right on the left. Just works better. (The white duct tape is there to attempt to prevent scratching the spring.)
* - I'm confident in my sag measurements. Each data point was created using several measurements (bike being compressed and bike rebounding) and were repeatable.