Reducing eye-to-eye to change geometry

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Reducing eye-to-eye to change geometry
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flag trialsracer
O+
Posted: Sep 19, 2016 at 12:13 Quote
I've really enjoyed the changes made to my bike by using a 2 degree angleset. With that and fork travel, you can tune a bike's HA and bb height quite nicely. Add offset bushings into the mix and you have quite a few ways to tweak a bike. However, with an internal headset frame, you can't use an angleset, leaving only bushings and fork travel at your disposal, and no way of dropping the bb without reducing travel AND steepening HA (the angleset is particularly nice to achieve both of these things).

So my question is, could you mount a slightly shorter shock (for some bikes this will require a reduction in stroke length and thus travel), to drop the bb and slacken the bike out? I haven't put anything in CAD to check numbers (nor do I really want to), but estimating from what Offset Bushing's site says ( http://www.offsetbushings.com/pages/how-they-work ), you should get about a degree slacker and 10mm bb drop for each 4mm reduction in eye-to-eye. So taking a 140mm bike with 197x54 to a 190x51 would get you 1.75 degress slacker, an extra 17.5mm bb drop, and a travel reduction to about 132mm.

What do you guys think? Anyone tried this and had success? My worry would be that messing with shocks could mess with the intended function of the suspension when you actually change the stroke length.
flag fuzzhead45
O+
Posted: Sep 19, 2016 at 13:04 Quote
I would think messing with the eye to eye length without reducing your travel could cause some issues with the suspension linkage. If you reduced the eye to eye length in the compressed state (using a shorter eye to eye shock with equivalent travel) your rear end is going to move further, possible crashing parts of the frame into each other and causing general unpleasantness .
flag jezzah
Posted: Sep 20, 2016 at 14:21 Quote
trialsracer wrote:
I've really enjoyed the changes made to my bike by using a 2 degree angleset. With that and fork travel, you can tune a bike's HA and bb height quite nicely. Add offset bushings into the mix and you have quite a few ways to tweak a bike. However, with an internal headset frame, you can't use an angleset, leaving only bushings and fork travel at your disposal, and no way of dropping the bb without reducing travel AND steepening HA (the angleset is particularly nice to achieve both of these things).

So my question is, could you mount a slightly shorter shock (for some bikes this will require a reduction in stroke length and thus travel), to drop the bb and slacken the bike out? I haven't put anything in CAD to check numbers (nor do I really want to), but estimating from what Offset Bushing's site says ( http://www.offsetbushings.com/pages/how-they-work ), you should get about a degree slacker and 10mm bb drop for each 4mm reduction in eye-to-eye. So taking a 140mm bike with 197x54 to a 190x51 would get you 1.75 degress slacker, an extra 17.5mm bb drop, and a travel reduction to about 132mm.

What do you guys think? Anyone tried this and had success? My worry would be that messing with shocks could mess with the intended function of the suspension when you actually change the stroke length.

Offset Bushings themselves don't reduce the amount of travel your frame has. Fuzzhead45 is right in that they adjust the bottom out position of your swingarm, though very few frames are tight enough on clearance to have any issues. Fortunately it's very easy to check how much clearance you would have before hand at bottom out.

Hope that helps!

Jeron
Offsetbushings.com
flag trialsracer
O+
Posted: Sep 20, 2016 at 15:10 Quote
jezzah wrote:
trialsracer wrote:
I've really enjoyed the changes made to my bike by using a 2 degree angleset. With that and fork travel, you can tune a bike's HA and bb height quite nicely. Add offset bushings into the mix and you have quite a few ways to tweak a bike. However, with an internal headset frame, you can't use an angleset, leaving only bushings and fork travel at your disposal, and no way of dropping the bb without reducing travel AND steepening HA (the angleset is particularly nice to achieve both of these things).

So my question is, could you mount a slightly shorter shock (for some bikes this will require a reduction in stroke length and thus travel), to drop the bb and slacken the bike out? I haven't put anything in CAD to check numbers (nor do I really want to), but estimating from what Offset Bushing's site says ( http://www.offsetbushings.com/pages/how-they-work ), you should get about a degree slacker and 10mm bb drop for each 4mm reduction in eye-to-eye. So taking a 140mm bike with 197x54 to a 190x51 would get you 1.75 degress slacker, an extra 17.5mm bb drop, and a travel reduction to about 132mm.

What do you guys think? Anyone tried this and had success? My worry would be that messing with shocks could mess with the intended function of the suspension when you actually change the stroke length.

Offset Bushings themselves don't reduce the amount of travel your frame has. Fuzzhead45 is right in that they adjust the bottom out position of your swingarm, though very few frames are tight enough on clearance to have any issues. Fortunately it's very easy to check how much clearance you would have before hand at bottom out.

Hope that helps!

Jeron
Offsetbushings.com

Yes, I am aware of that! I was asking if the offset bushings couldn't do enough, what the ramifications of actually shortening the shock, instead of just changing the position. However, I see Fuzzhead45 is saying, where if the shock is shorter in it's bottom out position, bad things could happen.

If there is no change in the length of the shock when bottomed out, the concept should work, right?
flag Gavingroves
Posted: Dec 14, 2022 at 0:53 Quote
I'd like to ask if someone has or know if offset bushes go in I a 250/75 WILL IT FIT OLD FURY.
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