Offset bushes to an...
 

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[Closed] Offset bushes to angleset geometry changes, help please.

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Changing from 1 degree bushes to 1.5 degree angleset, am I right in thinking when I remove the bushes I will regain reach, then lose it again with the angleset, leaving the bars in pretty much the same position? Also that the seat angle will steepen and BB will be roughly the same?


 
Posted : 21/06/2018 9:19 am
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Offset bushes will reduce reach, increase effective top tube and slacken seat tube angle, oh and lower bb obv.  An angleset will lower the front slightly (not the back as the bushes would) and so slightly increase reach, reduce effective top tube, steepen seat tube angle and also lower bb.  But the main effects of an angleset are on the head tube angle and on the wheelbase, the other effects are small, whereas with offset bushes the other effects are larger and more noticeable.


 
Posted : 21/06/2018 9:45 am
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Thanks greyspoke, makes sense.


 
Posted : 21/06/2018 10:49 am
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Offset bushes will reduce reach

This isn't true as the saddle and cranks are bolted to the same bit of the bike as the stem and bars, so offset bushings won't change reach, other than any side effect caused by a change in body position. I suppose an angleset would, but only very, very fractionally.

I use an offset bushing on my son's bike to reduce standover height (they certainly lower the BB and top tube) and slacken the headtube angle to offset the steepening caused by the reduction in travel from 120mm to 80mm on the fork. Works a treat.


 
Posted : 21/06/2018 10:52 am
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Offset bushings WILL alter reach because the front of the frame is angled more. Do I really need to get my crayons out again? I'm not sure I'd be able to find my original drawing with this new "improved" forum search.


 
Posted : 21/06/2018 11:05 am
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Offset bushings WILL alter reach because the front of the frame is angled more. Do I really need to get my crayons out again? I’m not sure I’d be able to find my original drawing with this new “improved” forum search.

I understand what you are saying and, as I said, reach only changes as a result of changed rider posture, but the typical measure of reach (saddle to centre of handlebar) will remain mathematically unchanged.


 
Posted : 21/06/2018 11:10 am
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I found that with a 2 degrees slackset, the reduction in reach from the angled steerer was not fully compensated for by the drop in the front end.


 
Posted : 21/06/2018 11:14 am
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That's not what is generally considered reach though is it?

Reach is BB to top centre of head tube in a horizontal line... Tilt the front end and the head tube gets closer to the BB horizontally.


 
Posted : 21/06/2018 11:15 am
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Thats not the traditional measurement of reach. Reach is the distance between a vertical line from centre of BB to a vertical line at the centre of where the stem meets the steerer tube.

Offset bushings will reduce the reach slightly. An angleset could also reduce the reach, depending on how many spacers are under the stem.


 
Posted : 21/06/2018 11:17 am
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Except reach has nothing to do with the stem or spacers...


 
Posted : 21/06/2018 11:19 am
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Thanks all - good information and it does make sense. I've been learned today 🙂


 
Posted : 21/06/2018 11:20 am
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So ignoring the actual maths, when I remove the offset bushes reach should increase slightly, then decrease again when I add the angleset?! max of a 5mm spacer under the stem, so body position on the bike should be very similar?!


 
Posted : 21/06/2018 11:23 am
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TBF the difference in reach are so small you're not likely to notice (unless you know in advance how much it is 😉 ).


 
Posted : 21/06/2018 1:18 pm
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but the typical measure of reach (saddle to centre of handlebar)

No.

No, no.

No, no, no.

No, no, no, no!


 
Posted : 21/06/2018 1:24 pm
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Bushings decrease reach, headsets increase reach. Last time I looked it was about 3mm on my setup. If you can notice that you're better than me.


 
Posted : 21/06/2018 3:01 pm

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