This is my hotrod TY175 showing the swingarm extension of 45mm behind the bottom shock mount

1980 SWM standard 52.5" 28.6%

1987 Aprilia standard 51.5" 28%

1982 SWM modified footrests 53" 25.5%

Here is info from a couple more bikes from my collection. I hope I don't add another level of compexity to the discussio but I noted one other significant difference when I was measuring - swingarm length - so I am adding that also.

'74 Yamaha TY250 51" 29% Swingarm 15"

'85 Honda TLR200 52" 29% Swingarm 18"

'94 Gas Gas JT25 53" 33% Swingarm 20.7"

I am not a suspension engineer but I think I see a trend here.

Related to this is the location of the swingarm pivot. The TY250 pivot is only slightly in front of the pegs. The TLR and the JT swingarms pivot 3 to 4" in front of the pegs. Can't change that because of the length of the engine.

For those who lengthened their TY175's how did it change the riding characteristics?

I am not a suspension engineer but I think I see a trend here.

Related to this is the location of the swingarm pivot. The TY250 pivot is only slightly in front of the pegs. The TLR and the JT swingarms pivot 3 to 4" in front of the pegs. Can't change that because of the length of the engine.

Yes there is an obvious trend - motors were developed over time to be shorter so the swingarm could be made longer

The lengthened swingarm on my TY175 made it more relaxing to ride (due to the increased wheelbase) and the rear suspension worked better (due to increased wheel travel).

Update.

Wow, I didn't realize how long it has been since I started this thread. I finally got to add the extensions to my swing arm. Actually, I picked up a second swing arm so I now have both the standard and longer one.

I cut off the old ends and added the extension pieces I bought from Shedworks. Also cut off and rewelded the mount for the brake plate rod. I think this added 1.5" to the length. Installed longer chain.

Rode for a couple miles last weekend and it seemed to work much better. More compliant, less twitchy. Also better for starting from a stop going uphill. It definitely made the front end feel heavier as expected. Overall, I am happy with the change.

On 12/8/2012 at 3:48 PM, b40rt said:

1980 SWM standard 52.5" 28.6%

1987 Aprilia standard 51.5" 28%

1982 SWM modified footrests 53" 25.5%

@feetupfun @pmkk parallel topic 're footrest position. The 87 Aprilia has had the footrest moved down and back since above, the percentage has dropped to 25% . Bike feels more "planted"  The top yoke has been changed to txr with risers, now much more comfortable with no downsides.